Science.gov

Sample records for optical depth precise

  1. Aerosol optical depth determination in the UV using a four-channel precision filter radiometer

    NASA Astrophysics Data System (ADS)

    Carlund, Thomas; Kouremeti, Natalia; Kazadzis, Stelios; Gröbner, Julian

    2017-03-01

    The determination of aerosol properties, especially the aerosol optical depth (AOD) in the ultraviolet (UV) wavelength region, is of great importance for understanding the climatological variability of UV radiation. However, operational retrievals of AOD at the biologically most harmful wavelengths in the UVB are currently only made at very few places. This paper reports on the UVPFR (UV precision filter radiometer) sunphotometer, a stable and robust instrument that can be used for AOD retrievals at four UV wavelengths. Instrument characteristics and results of Langley calibrations at a high-altitude site were presented. It was shown that due to the relatively wide spectral response functions of the UVPFR, the calibration constants (V0) derived from Langley plot calibrations underestimate the true extraterrestrial signals. Accordingly, correction factors were introduced. In addition, the instrument's spectral response functions also result in an apparent air-mass-dependent decrease in ozone optical depth used in the AOD determinations. An adjusted formula for the calculation of AOD, with a correction term dependent on total column ozone amount and ozone air mass, was therefore introduced. Langley calibrations performed 13-14 months apart resulted in sensitivity changes of ≤ 1.1 %, indicating good instrument stability. Comparison with a high-accuracy standard precision filter radiometer, measuring AOD at 368-862 nm wavelengths, showed consistent results. Also, very good agreement was achieved by comparing the UVPFR with AOD at UVB wavelengths derived with a Brewer spectrophotometer, which was calibrated against the UVPFR at an earlier date. Mainly due to non-instrumental uncertainties connected with ozone optical depth, the total uncertainty of AOD in the UVB is higher than that reported from AOD instruments measuring in UVA and visible ranges. However, the precision can be high among instruments using harmonized algorithms for ozone and Rayleigh optical depth as

  2. Mars-GRAM: Increasing the Precision of Sensitivity Studies at Large Optical Depths

    NASA Technical Reports Server (NTRS)

    Justh, Hilary L.; Justus, C. G.; Badger, Andrew M.

    2010-01-01

    The Mars Global Reference Atmospheric Model (Mars-GRAM) is an engineering-level atmospheric model widely used for diverse mission applications. Mars-GRAM's perturbation modeling capability is commonly used, in a Monte-Carlo mode, to perform high fidelity engineering end-to-end simulations for entry, descent, and landing (EDL). It has been discovered during the Mars Science Laboratory (MSL) site selection process that Mars-GRAM, when used for sensitivity studies for MapYear=0 and large optical depth values such as tau=3, is less than realistic. A comparison study between Mars atmospheric density estimates from Mars-GRAM and measurements by Mars Global Surveyor (MGS) has been undertaken for locations of varying latitudes, Ls, and LTST on Mars. The preliminary results from this study have validated the Thermal Emission Spectrometer (TES) limb data. From the surface to 80 km altitude, Mars-GRAM is based on the NASA Ames Mars General Circulation Model (MGCM). MGCM results that were used for Mars-GRAM with MapYear=0 were from a MGCM run with a fixed value of tau=3 for the entire year at all locations. This has resulted in an imprecise atmospheric density at all altitudes. To solve this pressure-density problem, density factor values were determined for tau=.3, 1 and 3 that will adjust the input values of MGCM MapYear 0 pressure and density to achieve a better match of Mars-GRAM MapYear 0 with TES observations for MapYears 1 and 2 at comparable dust loading. The addition of these density factors to Mars-GRAM will improve the results of the sensitivity studies done for large optical depths.

  3. Precise Measurement of the Reionization Optical Depth from the Global 21 cm Signal Accounting for Cosmic Heating

    NASA Astrophysics Data System (ADS)

    Fialkov, Anastasia; Loeb, Abraham

    2016-04-01

    As a result of our limited data on reionization, the total optical depth for electron scattering, τ, limits precision measurements of cosmological parameters from the Cosmic Microwave Background (CMB). It was recently shown that the predicted 21 cm signal of neutral hydrogen contains enough information to reconstruct τ with sub-percent accuracy, assuming that the neutral gas was much hotter than the CMB throughout the entire epoch of reionization (EoR). Here we relax this assumption and use the global 21 cm signal alone to extract τ for realistic X-ray heating scenarios. We test our model-independent approach using mock data for a wide range of ionization and heating histories and show that an accurate measurement of the reionization optical depth at a sub-percent level is possible in most of the considered scenarios even when heating is not saturated during the EoR, assuming that the foregrounds are mitigated. However, we find that in cases where heating sources had hard X-ray spectra and their luminosity was close to or lower than what is predicted based on low-redshift observations, the global 21 cm signal alone is not a good tracer of the reionization history.

  4. PRECISE MEASUREMENT OF THE REIONIZATION OPTICAL DEPTH FROM THE GLOBAL 21 cm SIGNAL ACCOUNTING FOR COSMIC HEATING

    SciTech Connect

    Fialkov, Anastasia; Loeb, Abraham E-mail: aloeb@cfa.harvard.edu

    2016-04-10

    As a result of our limited data on reionization, the total optical depth for electron scattering, τ, limits precision measurements of cosmological parameters from the Cosmic Microwave Background (CMB). It was recently shown that the predicted 21 cm signal of neutral hydrogen contains enough information to reconstruct τ with sub-percent accuracy, assuming that the neutral gas was much hotter than the CMB throughout the entire epoch of reionization (EoR). Here we relax this assumption and use the global 21 cm signal alone to extract τ for realistic X-ray heating scenarios. We test our model-independent approach using mock data for a wide range of ionization and heating histories and show that an accurate measurement of the reionization optical depth at a sub-percent level is possible in most of the considered scenarios even when heating is not saturated during the EoR, assuming that the foregrounds are mitigated. However, we find that in cases where heating sources had hard X-ray spectra and their luminosity was close to or lower than what is predicted based on low-redshift observations, the global 21 cm signal alone is not a good tracer of the reionization history.

  5. Precision Optics Curriculum.

    ERIC Educational Resources Information Center

    Reid, Robert L.; And Others

    This guide outlines the competency-based, two-year precision optics curriculum that the American Precision Optics Manufacturers Association has proposed to fill the void that it suggests will soon exist as many of the master opticians currently employed retire. The model, which closely resembles the old European apprenticeship model, calls for 300…

  6. Precision Optics Curriculum.

    ERIC Educational Resources Information Center

    Reid, Robert L.; And Others

    This guide outlines the competency-based, two-year precision optics curriculum that the American Precision Optics Manufacturers Association has proposed to fill the void that it suggests will soon exist as many of the master opticians currently employed retire. The model, which closely resembles the old European apprenticeship model, calls for 300…

  7. Ultra-Precision Optics

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Under a Joint Sponsored Research Agreement with Goddard Space Flight Center, SEMATECH, Inc., the Silicon Valley Group, Inc. and Tinsley Laboratories, known as SVG-Tinsley, developed an Ultra-Precision Optics Manufacturing System for space and microlithographic applications. Continuing improvements in optics manufacture will be able to meet unique NASA requirements and the production needs of the lithography industry for many years to come.

  8. Precision optical navigation guidance system

    NASA Astrophysics Data System (ADS)

    Starodubov, D.; McCormick, K.; Nolan, P.; Johnson, D.; Dellosa, M.; Volfson, L.; Fallahpour, A.; Willner, A.

    2016-05-01

    We present the new precision optical navigation guidance system approach that provides continuous, high quality range and bearing data to fixed wing aircraft during landing approach to an aircraft carrier. The system uses infrared optical communications to measure range between ship and aircraft with accuracy and precision better than 1 meter at ranges more than 7.5 km. The innovative receiver design measures bearing from aircraft to ship with accuracy and precision better than 0.5 mRad. The system provides real-time range and bearing updates to multiple aircraft at rates up to several kHz, and duplex data transmission between ship and aircraft.

  9. Optical transients and depth analysis

    NASA Technical Reports Server (NTRS)

    Schaefer, Bradley E.

    1992-01-01

    Flaws of the depth analysis technique of distinguishing photographic plate defects are discussed. The method is shown to be unreliable in confirming or disproving the astrophysical nature of optical transients. The arguments of Greiner and of Zytkow to the contrary are criticized.

  10. Precision optical reference frequencies

    NASA Astrophysics Data System (ADS)

    Riehle, Fritz; Schnatz, Harald; Zinner, G.; Trebst, Tilmann; Helmcke, Juergen

    1999-05-01

    Optical reference frequencies are provided by lasers of which the frequencies are stabilized to suitable absorption lines. Presently, twelve reference frequencies/wavelengths within the wavelengths range from 243 nm to 10.3 micrometers are recommended by the International Committee of Weights and Measures as references for the realization of the meter and scientific applications. As typical examples, we describe a diode-pumped, frequency doubled YAG-laser stabilized to an absorption line of molecular iodine and a Ca-stabilized laser. The latter one has been developed in two versions, a transportable system utilizing a small beam of thermal Ca atoms and a stationary standard based on laser cooled and trapped Ca atoms. The frequency of the Ca standard based on cold Ca atoms has been measured by a frequency chain allowing a phase-coherent comparison against the primary standard of time and frequency, the caesium clock. Its value is vCa equals 455 986 240 494.13 kHz with a relative standard uncertainty of 2.5 (DOT) 10-13.

  11. Depth Cues From Optical Flow

    NASA Astrophysics Data System (ADS)

    Shih, Frank Y.; Prathuri, Chandra

    1990-03-01

    In order to have a perfect computer vision system, it is important that it should emulate something which is already prefect - the human visual system. In this paper we discuss the relevancy of the study of the psychological and physiological aspects of human vision to computer vision research. Motion perception is an important aspect of vision. We make an approach here, to configure a system that can perceive world knowledge from moving scenes. This is based on the principle that moving scenes generate optical flow and getting the depth cues from optical flow gives three dimensional information of the scene. We derive depth information from passive ranging techniques. Potential applications are in autonomous vehicle navigation, coordinated motions between vehicles for passive ranging to moving targets and in industrial robotics.

  12. Precision optical metrology without lasers

    NASA Astrophysics Data System (ADS)

    Bergmann, Ralf B.; Burke, Jan; Falldorf, Claas

    2015-07-01

    Optical metrology is a key technique when it comes to precise and fast measurement with a resolution down to the micrometer or even nanometer regime. The choice of a particular optical metrology technique and the quality of results depends on sample parameters such as size, geometry and surface roughness as well as user requirements such as resolution, measurement time and robustness. Interferometry-based techniques are well known for their low measurement uncertainty in the nm range, but usually require careful isolation against vibration and a laser source that often needs shielding for reasons of eye-safety. In this paper, we concentrate on high precision optical metrology without lasers by using the gradient based measurement technique of deflectometry and the finite difference based technique of shear interferometry. Careful calibration of deflectometry systems allows one to investigate virtually all kinds of reflecting surfaces including aspheres or free-form surfaces with measurement uncertainties below the μm level. Computational Shear Interferometry (CoSI) allows us to combine interferometric accuracy and the possibility to use cheap and eye-safe low-brilliance light sources such as e.g. fiber coupled LEDs or even liquid crystal displays. We use CoSI e.g. for quantitative phase contrast imaging in microscopy. We highlight the advantages of both methods, discuss their transfer functions and present results on the precision of both techniques.

  13. Magnitude, precision, and realism of depth perception in stereoscopic vision.

    PubMed

    Hibbard, Paul B; Haines, Alice E; Hornsey, Rebecca L

    2017-01-01

    Our perception of depth is substantially enhanced by the fact that we have binocular vision. This provides us with more precise and accurate estimates of depth and an improved qualitative appreciation of the three-dimensional (3D) shapes and positions of objects. We assessed the link between these quantitative and qualitative aspects of 3D vision. Specifically, we wished to determine whether the realism of apparent depth from binocular cues is associated with the magnitude or precision of perceived depth and the degree of binocular fusion. We presented participants with stereograms containing randomly positioned circles and measured how the magnitude, realism, and precision of depth perception varied with the size of the disparities presented. We found that as the size of the disparity increased, the magnitude of perceived depth increased, while the precision with which observers could make depth discrimination judgments decreased. Beyond an initial increase, depth realism decreased with increasing disparity magnitude. This decrease occurred well below the disparity limit required to ensure comfortable viewing.

  14. Ultrasonic precision optical grinding technology

    NASA Astrophysics Data System (ADS)

    Cahill, Michael J.; Bechtold, Michael J.; Fess, Edward; Wolfs, Frank L.; Bechtold, Rob

    2015-10-01

    As optical geometries become more precise and complex and a wider range of materials are used, the processes used for manufacturing become more critical. As the preparatory stage for polishing, this is especially true for grinding. Slow processing speeds, accelerated tool wear, and poor surface quality are often detriments in manufacturing glass and hard ceramics. The quality of the ground surface greatly influences the polishing process and the resulting finished product. Through extensive research and development, OptiPro Systems has introduced an ultrasonic assisted grinding technology, OptiSonic, which has numerous advantages over traditional grinding processes. OptiSonic utilizes a custom tool holder designed to produce oscillations in line with the rotating spindle. A newly developed software package called IntelliSonic is integral to this platform. IntelliSonic automatically characterizes the tool and continuously optimizes the output frequency for optimal cutting while in contact with the part. This helps maintain a highly consistent process under changing load conditions for a more accurate surface. Utilizing a wide variety of instruments, test have proven to show a reduction in tool wear and increase in surface quality while allowing processing speeds to be increased. OptiSonic has proven to be an enabling technology to overcome the difficulties seen in grinding of glass and hard optical ceramics. OptiSonic has demonstrated numerous advantages over the standard CNC grinding process. Advantages are evident in reduced tool wear, better surface quality, and reduced cycle times due to increased feed rates. These benefits can be seen over numerous applications within the precision optics industry.

  15. Navy precision optical interferometer database

    NASA Astrophysics Data System (ADS)

    Ryan, K. K.; Jorgensen, A. M.; Hall, T.; Armstrong, J. T.; Hutter, D.; Mozurkewich, D.

    2012-07-01

    The Navy Precision Optical Interferometer (NPOI) has now been recording astronomical observations for the better part of two decades. During that time period hundreds of thousands of observations have been obtained, with a total data volume of multiple terabytes. Additionally, in the next few years the data rate from the NPOI is expected to increase significantly. To make it easier for NPOI users to search the NPOI observations and to make it easier for them to obtain data, we have constructed a easily accessible and searchable database of observations. The database is based on a MySQL server and uses standard query language (SQL). In this paper we will describe the database table layout and show examples of possible database queries.

  16. Precise relative earthquake depth determination using array processing techniques

    NASA Astrophysics Data System (ADS)

    Florez, M. A.; Prieto, G. A.

    2017-06-01

    Precise determination of hypocentral depth remains one of the most relevant problems in earthquake seismology. It is well known that using depth phases allows for significant improvement in event depth determination; however, routinely and systematically picking such phases, for teleseismic or regional arrivals, is problematic due to poor signal-to-noise ratios around the pP and sP phases. To overcome this limitation, we have taken advantage of the additional information carried by seismic arrays. We use velocity spectral analysis to precisely measure pP-P times. The individual estimates obtained at different subarrays, for all pairs of earthquakes, are combined using a double-difference algorithm, in order to precisely map seismicity in regions where it is tightly clustered. We illustrate this method by relocating intermediate-depth earthquakes in the Nazca subducting plate, beneath northern Chile, where we confirm the existence of a narrowly spaced double seismic zone, previously imaged using a local dedicated deployment. As a second example we relocate the aftershock sequence of the 2014 Mw 7.9 intermediate depth, Rat Islands earthquake, and provide evidence of a subvertical fault plane for the main shock. Finally, we show that the resulting relative depth errors are typically smaller than 2 km.

  17. Precision injection molding of freeform optics

    NASA Astrophysics Data System (ADS)

    Fang, Fengzhou; Zhang, Nan; Zhang, Xiaodong

    2016-08-01

    Precision injection molding is the most efficient mass production technology for manufacturing plastic optics. Applications of plastic optics in field of imaging, illumination, and concentration demonstrate a variety of complex surface forms, developing from conventional plano and spherical surfaces to aspheric and freeform surfaces. It requires high optical quality with high form accuracy and lower residual stresses, which challenges both optical tool inserts machining and precision injection molding process. The present paper reviews recent progress in mold tool machining and precision injection molding, with more emphasis on precision injection molding. The challenges and future development trend are also discussed.

  18. Ultra-precision processes for optics manufacturing

    NASA Astrophysics Data System (ADS)

    Martin, William R.

    1991-12-01

    The Optics MODIL (Manufacturing Operations Development and Integration Laboratory) is developing advanced manufacturing technologies for fabrication of ultra precision optical components, aiming for a ten-fold improvement in precision and a shortening of the scheduled lead time. Current work focuses on diamond single point turning, ductile grinding, ion milling, and in/on process metrology.

  19. Ultra-precision processes for optics manufacturing

    NASA Technical Reports Server (NTRS)

    Martin, William R.

    1991-01-01

    The Optics MODIL (Manufacturing Operations Development and Integration Laboratory) is developing advanced manufacturing technologies for fabrication of ultra precision optical components, aiming for a ten-fold improvement in precision and a shortening of the scheduled lead time. Current work focuses on diamond single point turning, ductile grinding, ion milling, and in/on process metrology.

  20. Precision Fiber Optic Sensor Market Forecast

    NASA Astrophysics Data System (ADS)

    Montgomery, Jeff D.; Glasco, Jon; Dixon, Frank W.

    1986-01-01

    The worldwide market for precision fiber optic sensors is forecasted, 1984-1994. The forecast is based upon o Analysis of fiber optic sensor and related component current technology, and a forecast of technology advancement o Review and projection of demand for precision sensing, and the penetration which fiber optics will make into this market The analysis and projections are based mainly on interviews conducted worldwide with research teams, government agencies, systems contractors, medical and industrial laboratories, component suppliers and others. The worldwide market for precision (interferometric) fiber optic sensing systems is forecasted to exceed $0.8 billion by 1994. The forecast is segmented by geographical region (Europe, Japan and North America) and by function; o Gyroscope o Sonar o Gradiometer/Magnetometer o Other - Chemical Composition - Atmospheric Acoustic - Temperature - Position - Pressure Requirements for components are reviewed. These include special fiber, emitters and detectors, modulators, couplers, switches, integrated optical circuits and integrated optoelectronics. The advancement in component performance is forecasted. The major driving forces creating fiber optic sensor markets are reviewed. These include fiber optic sensor technical and economic advantages, increasingly stringent operational requirements, and technology evolution. The leading fiber optic sensor and related component development programs are reviewed. Component sources are listed. Funding sources for sensor and component development are outlined, and trends forecasted.

  1. High precision laser photometer for laser optics

    NASA Astrophysics Data System (ADS)

    Zhao, Yuan'an; Hu, Guohang; Cao, Zhen; Liu, Shijie; Zhu, Meiping; Shao, Jianda

    2017-06-01

    Development of laser systems requires optical components with high performance, and a high-precision double-beam laser photometer was designed and established to measure the optical performance at 1064nm. Double beam design and lock-in technique was applied to decrease the impact of light energy instability and electric noise. Pairs of samples were placed symmetrically to eliminate beam displacement, and laser scattering imaging technique was applied to determine the influence of surface defect on the optical performance. Based on the above techniques, transmittance and reflection of pairs of optics were obtained, and the measurement precision was improved to 0.06%. Different types of optical loss, such as total loss, volume loss, residual reflection and surface scattering loss, were obtained from the transmittance and reflection measurement of samples with different thickness. Comparison of optical performance of the test points with and without surface defects, the influence of surface defects on optical performance was determined. The optical performance of Nd-glass at 1064nm were measured as an example. Different types of optical loss and the influence of surface defects on the optical loss was determined.

  2. Precision optical interferometry in space

    NASA Technical Reports Server (NTRS)

    Reasenberg, Robert D.

    1993-01-01

    POINTS, an astrometric Optical interferometer with a nominal measurement accuracy of 5 microarcseconds for the angle between a pair of stars separated by about 90 deg, is presently under consideration by two divisions of NASA-OSSA. It will be a powerful new multi-disciplinary tool for astronomical research. If chosen as the TOPS-1 (Toward Other Planetary Systems) instrument by the Solar-System Exploration Division, it will perform a definitive search for extra-solar planetary systems, either finding and characterizing a large number of them or showing that they are far less numerous than now believed. If chosen as the AIM (Astrometric Interferometry Mission) by the Astrophysics Division, POINTS will open new areas of astrophysical research and change the nature of the questions being asked in some old areas. In either case. it will be the first of a new class of powerful instruments in space and will prove the technology for the larger members of that class to follow. Based on a preliminary indication of the observational needs of the two missions, we find that a single POINTS mission will meet the science objectives of both TOPS-1 and AIM. The instrument detects dispersed fringe (channel led spectrum) and therefore can tolerate large pointing errors.

  3. Aerosol Optical Depth Determinations for BOREAS

    NASA Technical Reports Server (NTRS)

    Wrigley, R. C.; Livingston, J. M.; Russell, P. B.; Guzman, R. P.; Ried, D.; Lobitz, B.; Peterson, David L. (Technical Monitor)

    1994-01-01

    Automated tracking sun photometers were deployed by NASA/Ames Research Center aboard the NASA C-130 aircraft and at a ground site for all three Intensive Field Campaigns (IFCs) of the Boreal Ecosystem-Atmosphere Study (BOREAS) in central Saskatchewan, Canada during the summer of 1994. The sun photometer data were used to derive aerosol optical depths for the total atmospheric column above each instrument. The airborne tracking sun photometer obtained data in both the southern and northern study areas at the surface prior to takeoff, along low altitude runs near the ground tracking sun photometer, during ascents to 6-8 km msl, along remote sensing flightlines at altitude, during descents to the surface, and at the surface after landing. The ground sun photometer obtained data from the shore of Candle Lake in the southern area for all cloud-free times. During the first IFC in May-June ascents and descents of the airborne tracking sun photometer indicated the aerosol optical depths decreased steadily from the surface to 3.5 kni where they leveled out at approximately 0.05 (at 525 nm), well below levels caused by the eruption of Mt. Pinatubo. On a very clear day, May 31st, surface optical depths measured by either the airborne or ground sun photometers approached those levels (0.06-0.08 at 525 nm), but surface optical depths were often several times higher. On June 4th they increased from 0.12 in the morning to 0.20 in the afternoon with some evidence of brief episodes of pollen bursts. During the second IFC surface aerosol optical depths were variable in the extreme due to smoke from western forest fires. On July 20th the aerosol optical depth at 525 nm decreased from 0.5 in the morning to 0.2 in the afternoon; they decreased still further the next day to 0.05 and remained consistently low throughout the day to provide excellent conditions for several remote sensing missions flown that day. Smoke was heavy for the early morning of July 24th but cleared partially by 10

  4. Depth selective acousto-optic flow measurement

    PubMed Central

    Tsalach, Adi; Schiffer, Zeev; Ratner, Eliahu; Breskin, Ilan; Zeitak, Reuven; Shechter, Revital; Balberg, Michal

    2015-01-01

    Optical based methods for non-invasive measurement of regional blood flow tend to incorrectly assess cerebral blood flow, due to contribution of extra-cerebral tissues to the obtained signal. We demonstrate that spectral analysis of phase-coded light signals, tagged by specific ultrasound patterns, enables differentiation of flow patterns at different depths. Validation of the model is conducted by Monte Carlo simulation. In-vitro experiments demonstrate good agreement with the simulations' results and provide a solid validation to depth discrimination ability. These results suggest that signal contamination originating from extra-cerebral tissue may be eliminated using spectral analysis of ultrasonically tagged light. PMID:26713201

  5. Precise, controlled laser delivery with evanescent optical waves.

    PubMed

    Hooper, B A; Domankevitz, Y; Lin, C P; Anderson, R R

    1999-09-01

    Precise laser surgery is possible with laser pulses at wavelengths that are strongly absorbed at the surface of tissue. However, pulses at these wavelengths (far UV, far infrared) are not compatible with fiber-optic transmission, making endoscopic surgical procedures inside the body difficult. We use evanescent optical waves to demonstrate an alternative for confining energy near the tissue surface. Precise, superficial tissue ablation is achieved with evanescent waves generated at a sapphire-tissue interface by a free-electron laser, where the ablation depth may be varied. A new class of precise, controlled laser surgical tools may be achieved in this novel approach for use in endoscopic procedures. Electromagnetic theory governing evanescent-wave tissue ablation is presented.

  6. High precision Woelter optic calibration facility

    SciTech Connect

    Morales, R.I.; Remington, B.A.; Schwinn, T. )

    1995-01-01

    We have developed an off-line facility for very precise characterization of the reflectance and spatial resolution of the grazing incidence Woelter type I x-ray optics used at Nova. The primary component of the facility is a new, very versatile, high brightness x-ray source consisting of a focused DC electron beam incident onto a precision manipulated target-pinhole array. The data are recorded with a selection of detectors. For imaging measurements we use direct exposure x-ray film modules or an x-ray charge-coupled device camera. For energy-resolved reflectance measurements, we use lithium drifted silicon detectors and a proportional counter. An [ital in] [ital situ] laser alignment system allows precise location and rapid periodic alignment verification of the x-ray point source, the statically mounted Woelter optic, and the chosen detector.

  7. High precision Woelter optic calibration facility

    SciTech Connect

    Morales, R.I.; Remington, B.A.; Schwinn, T.

    1994-05-02

    We have developed an off-line facility for very precise characterization of the reflectance and spatial resolution of the grazing incidence Woelter Type 1 x-ray optics used at Nova. The primary component of the facility is a high brightness, ``point`` x-ray source consisting of a focussed DC electron beam incident onto a precision manipulated target/pinhole array. The data are recorded with a selection of detectors. For imaging measurements we use direct exposure x-ray film modules or an x-ray CCD camera. For energy-resolved reflectance measurements, we use lithium drifted silicon detectors and a proportional counter. An in situ laser alignment system allows precise location and rapid periodic alignment verification of the x-ray point source, the statically mounted Woelter optic, and the chosen detector.

  8. Developments in precision optical grinding technology

    NASA Astrophysics Data System (ADS)

    Fess, Edward; Bechtold, Mike; Wolfs, Frank; Bechtold, Rob

    2013-09-01

    Optical systems that utilize complex optical geometries such as aspheres and freeform optics require precise control through the manufacturing process. As the preparatory stage for polishing, this is especially true for grinding. The quality of the grinding process can greatly influence the polishing process and the resultant finished product. OptiPro has performed extensive development work in evaluating components of a precision grinding machine to determine how they influence the overall manufacturing process. For example, spindle technology has a strong effect on how a grinding machine will perform. Through metrology techniques that measure the vibration characteristics of a machine and measurements of grinding forces with a dynamometer, OptiPro has also developed a detailed knowledge of how the machine can influence the grinding process. One of the outcomes of this work has led OptiPro to develop an ultrasonic head for their grinding platform to aid in reducing grinding forces. Initial results show a reduction in force by ~50%.

  9. Diurnal variations in optical depth at Mars

    NASA Technical Reports Server (NTRS)

    Colburn, D. S.; Pollack, J. B.; Haberle, R. M.

    1989-01-01

    Viking lander camera images of the Sun were used to compute atmospheric optical depth at two sites over a period of 1 to 1/3 martian years. The complete set of 1044 optical depth determinations is presented in graphical and tabular form. Error estimates are presented in detail. Otpical depths in the morning (AM) are generally larger than in the afternoon (PM). The AM-PM differences are ascribed to condensation of water vapor into atmospheric ice aerosols at night and their evaporation in midday. A smoothed time series of these differences shows several seasonal peaks. These are simulated using a one-dimensional radiative convective model which predicts martial atmospheric temperature profiles. A calculation combinig these profiles with water vapor measurements from the Mars Atmospheric Water Detector is used to predict when the diurnal variations of water condensation should occur. The model reproduces a majority of the observed peaks and shows the factors influencing the process. Diurnal variation of condensation is shown to peak when the latitude and season combine to warm the atmosphere to the optimum temperature, cool enough to condense vapor at night and warm enough to cause evaporation at midday.

  10. Diurnal variations in optical depth at Mars

    NASA Technical Reports Server (NTRS)

    Colburn, D. S.; Pollack, J. B.; Haberle, R. M.

    1989-01-01

    Viking lander camera images of the Sun were used to compute atmospheric optical depth at two sites over a period of 1 to 1/3 martian years. The complete set of 1044 optical depth determinations is presented in graphical and tabular form. Error estimates are presented in detail. Otpical depths in the morning (AM) are generally larger than in the afternoon (PM). The AM-PM differences are ascribed to condensation of water vapor into atmospheric ice aerosols at night and their evaporation in midday. A smoothed time series of these differences shows several seasonal peaks. These are simulated using a one-dimensional radiative convective model which predicts martial atmospheric temperature profiles. A calculation combinig these profiles with water vapor measurements from the Mars Atmospheric Water Detector is used to predict when the diurnal variations of water condensation should occur. The model reproduces a majority of the observed peaks and shows the factors influencing the process. Diurnal variation of condensation is shown to peak when the latitude and season combine to warm the atmosphere to the optimum temperature, cool enough to condense vapor at night and warm enough to cause evaporation at midday.

  11. Diurnal variations in optical depth at Mars

    NASA Astrophysics Data System (ADS)

    Colburn, D. S.; Pollack, J. B.; Haberle, R. M.

    1989-05-01

    Viking lander camera images of the Sun were used to compute atmospheric optical depth at two sites over a period of 1 to 1/3 martian years. The complete set of 1044 optical depth determinations is presented in graphical and tabular form. Error estimates are presented in detail. Otpical depths in the morning (AM) are generally larger than in the afternoon (PM). The AM-PM differences are ascribed to condensation of water vapor into atmospheric ice aerosols at night and their evaporation in midday. A smoothed time series of these differences shows several seasonal peaks. These are simulated using a one-dimensional radiative convective model which predicts martial atmospheric temperature profiles. A calculation combinig these profiles with water vapor measurements from the Mars Atmospheric Water Detector is used to predict when the diurnal variations of water condensation should occur. The model reproduces a majority of the observed peaks and shows the factors influencing the process. Diurnal variation of condensation is shown to peak when the latitude and season combine to warm the atmosphere to the optimum temperature, cool enough to condense vapor at night and warm enough to cause evaporation at midday.

  12. Extinction and optical depth of contrails

    NASA Astrophysics Data System (ADS)

    Voigt, C.; Schumann, U.; Jessberger, P.; Jurkat, T.; Petzold, A.; Gayet, J.-F.; Krämer, M.; Thornberry, T.; Fahey, D. W.

    2011-06-01

    One factor limiting the understanding of the climate impact from contrails and aircraft induced cloud modifications is the accurate determination of their optical depth. To this end, 14 contrails were sampled for 2756 s with instruments onboard the research aircraft Falcon during the CONCERT (CONtrail and Cirrus ExpeRimenT) campaign in November 2008. The young (<10 min old) contrails were produced by 9 commercial aircraft with weights of 47 to 508 t, among them the largest operating passenger aircraft, the Airbus A380. The contrails were observed at temperatures between 214 and 224 K and altitudes between 8.8 and 11.1 km. The measured mean in-contrail relative humidity with respect to ice was 89 ± 12%. Six contrails were observed in cloud free air, the others were embedded in thin cirrus clouds. The observed contrails exhibited a mean ice water content of 2 mg m-3 and had a mean number concentration of 117 cm-3 and effective radius of 2.9 μm assuming asphericle particles with an aspect ratio of 0.5. Probability density functions of the extinction, with a mean (median) of 1.2 (0.7) km-1, and of the optical depth τ, with a mean (median) of 0.27 (0.13), are derived from the in situ measurements and are likely representative for young contrails from the present-day commercial aircraft fleet at observation conditions. Radiative transfer estimates using the in-situ measured contrail optical depth lead to a year-2005 estimate of line-shaped contrail radiative forcing of 15.9 mWm-2 with an uncertainty range of 11.1-47.7 mWm-2.

  13. THEMIS Observations of Atmospheric Aerosol Optical Depth

    NASA Technical Reports Server (NTRS)

    Smith, Michael D.; Bandfield, Joshua L.; Christensen, Philip R.; Richardson, Mark I.

    2003-01-01

    The Mars Odyssey spacecraft entered into Martian orbit in October 2001 and after successful aerobraking began mapping in February 2002 (approximately Ls=330 deg.). Images taken by the Thermal Emission Imaging System (THEMIS) on-board the Odyssey spacecraft allow the quantitative retrieval of atmospheric dust and water-ice aerosol optical depth. Atmospheric quantities retrieved from THEMIS build upon existing datasets returned by Mariner 9, Viking, and Mars Global Surveyor (MGS). Data from THEMIS complements the concurrent MGS Thermal Emission Spectrometer (TES) data by offering a later local time (approx. 2:00 for TES vs. approx. 4:00 - 5:30 for THEMIS) and much higher spatial resolution.

  14. THEMIS Observations of Atmospheric Aerosol Optical Depth

    NASA Technical Reports Server (NTRS)

    Smith, Michael D.; Bandfield, Joshua L.; Christensen, Philip R.; Richardson, Mark I.

    2003-01-01

    The Mars Odyssey spacecraft entered into Martian orbit in October 2001 and after successful aerobraking began mapping in February 2002 (approximately Ls=330 deg.). Images taken by the Thermal Emission Imaging System (THEMIS) on-board the Odyssey spacecraft allow the quantitative retrieval of atmospheric dust and water-ice aerosol optical depth. Atmospheric quantities retrieved from THEMIS build upon existing datasets returned by Mariner 9, Viking, and Mars Global Surveyor (MGS). Data from THEMIS complements the concurrent MGS Thermal Emission Spectrometer (TES) data by offering a later local time (approx. 2:00 for TES vs. approx. 4:00 - 5:30 for THEMIS) and much higher spatial resolution.

  15. Nanoscale depth reconstruction from defocus: within an optical diffraction model.

    PubMed

    Wei, Yangjie; Wu, Chengdong; Dong, Zaili

    2014-10-20

    Depth from defocus (DFD) based on optical methods is an effective method for depth reconstruction from 2D optical images. However, due to optical diffraction, optical path deviation occurs, which results in blurring imaging. Blurring, in turn, results in inaccurate depth reconstructions using DFD. In this paper, a nanoscale depth reconstruction method using defocus with optical diffraction is proposed. A blurring model is proposed by considering optical diffraction, leading to a much higher accuracy in depth reconstruction. Firstly, Fresnel diffraction in an optical system is analyzed, and a relationship between intensity distribution and depth information is developed. Secondly, a blurring imaging model with relative blurring and heat diffusion is developed through curving fitting of a numerical model. In this way, a new DFD method with optical diffraction is proposed. Finally, experimental results show that this new algorithm is more effective for depth reconstruction on the nanoscale.

  16. Processing depth distance data to increase precision of multiple infrared sensors in the automatic visual inspection system

    NASA Astrophysics Data System (ADS)

    Szablata, Piotr; Łąkowski, Paweł; Pochmara, Janusz

    2017-08-01

    Infrared depth recognition technology with an efficient custom-made signal smoothing algorithm is used as a base for a precise inspection system. The main purpose of this paper is to introduce the basics of an algorithm that will improve precision and stabilize distance measurements in projects with camera image and depth sensors. Such results are within the reach of currently available hardware but not with the available software, for which there is a lack of suppliers support. The second goal is to prove that golden sample data matrix compiled from multiple sensors data can be taken into consideration as a simple and general automated optical inspection system.

  17. Ultra-Light Precision Membrane Optics

    NASA Technical Reports Server (NTRS)

    Moore, Jim; Gunter, Kent; Patrick, Brian; Marty, Dave; Bates, Kevin; Gatlin, Romona; Clayton, Bill; Rood, Bob; Brantley, Whitt (Technical Monitor)

    2001-01-01

    SRS Technologies and NASA Marshall Space Flight Center have conducted a research effort to explore the possibility of developing ultra-lightweight membrane optics for future imaging applications. High precision optical flats and spherical mirrors were produced under this research effort. The thin film mirrors were manufactured using surface replication casting of CPI(Trademark), a polyimide material developed specifically for UV hardness and thermal stability. In the course of this program, numerous polyimide films were cast with surface finishes better than 1.5 nanometers rms and thickness variation of less than 63 nanometers. Precision membrane optical flats were manufactured demonstrating better than 1/13 wave figure error when measured at 633 nanometers. The aerial density of these films is 0.037 kilograms per square meter. Several 0.5-meter spherical mirrors were also manufactured. These mirrors had excellent surface finish (1.5 nanometers rms) and figure error on the order of tens of microns. This places their figure error within the demonstrated correctability of advanced wavefront correction technologies such as real time holography.

  18. Precision optical displacement measurements using biphotons

    NASA Astrophysics Data System (ADS)

    Lyons, Kevin; Pang, Shengshi; Kwiat, Paul G.; Jordan, Andrew N.

    2016-04-01

    We propose and examine the use of biphoton pairs, such as those created in parametric down-conversion or four-wave mixing, to enhance the precision and the resolution of measuring optical displacements by position-sensitive detection. We show that the precision of measuring a small optical beam displacement with this method can be significantly enhanced by the correlation between the two photons, given the same optical mode. The improvement is largest if the correlations between the photons are strong, and falls off as the biphoton correlation weakens. More surprisingly, we find that the smallest resolvable parameter of a simple split detector scales as the inverse of the number of biphotons for small biphoton number ("Heisenberg scaling"), because the Fisher information diverges as the parameter to be estimated decreases in value. One usually sees this scaling only for systems with many entangled degrees of freedom. We discuss the transition for the split-detection scheme to the standard quantum limit scaling for imperfect correlations as the biphoton number is increased. An analysis of an N -pixel detector is also given to investigate the benefit of using a higher resolution detector. The physical limit of these metrology schemes is determined by the uncertainty in the birth zone of the biphoton in the nonlinear crystal.

  19. High precision optical surface metrology using deflectometry

    NASA Astrophysics Data System (ADS)

    Huang, Run

    Software Configurable Optical Test System (SCOTS) developed at University of Arizona is a highly efficient optical metrology technique based on the principle of deflectometry, which can achieve comparable accuracy with interferometry but with low-cost hardware. In a SCOTS test, an LCD display is used to generate structured light pattern to illuminate the test optics and the reflected light is captured by a digital camera. The surface slope of test optics is determined by triangulation of the display pixels, test optics, and the camera. The surface shape is obtained by the integration of the slopes. Comparing to interferometry, which has long served as an accurate non-contact optical metrology technology, SCOTS overcomes the limitation of dynamic range and sensitivity to environment. It is able to achieve high dynamic range slope measurement without requiring null optics. In this dissertation, the sensitivity and performance of the test system have been analyzed comprehensively. Sophisticated calibrations of system components have been investigated and implemented in different metrology projects to push this technology to a higher accuracy including low-order terms. A compact on-axis SCOTS system lowered the testing geometry sensitivity in the metrology of 1-meter highly aspheric secondary mirror of Large Binocular Telescope. Sub-nm accuracy was achieved in testing a high precision elliptical X-ray mirror by using reference calibration. A well-calibrated SCOTS was successfully constructed and is, at the time of writing this dissertation, being used to provide surface metrology feedback for the fabrication of the primary mirror of Daniel K. Inouye Solar Telescope which is a 4-meter off-axis parabola with more than 8 mm aspherical departure.

  20. Chemical bonding for precision optical assemblies

    NASA Astrophysics Data System (ADS)

    Green, Katie; Burke, Jan; Oreb, Bozenko

    2011-02-01

    We report on the optimization of precision optical component assemblies for space application with respect to mechanical resilience and retention of optical tolerances such as flatness and angles. Optimized parameters include: the cleaning method of the surfaces to be joined; type, concentration, and quantity of the chemical bonding agent; and post-bonding and curing conditions. Experimental studies and quality assurance are complicated by the large statistical spread in breaking stress, which requires the preparation of a large number of samples. The results previously reported in literature have focused primarily on fused silica, rather than space-qualifiable materials such as Zerodur® and ULE®, and have typically addressed only one or two of the parameters. This study provides a comprehensive picture and a better general understanding of what makes a bond reliably strong.

  1. Precision optical device of freeform defects inspection

    NASA Astrophysics Data System (ADS)

    Meguellati, S.

    2015-09-01

    This method of optical scanning presented in this paper is used for precision measurement deformation in shape or absolute forms in comparison with a reference component form, of optical or mechanical components, on reduced surfaces area that are of the order of some mm2 and more. The principle of the method is to project the image of the source grating to palpate optically surface to be inspected, after reflection; the image of the source grating is printed by the object topography and is then projected onto the plane of reference grating for generate moiré fringe for defects detection. The optical device used allows a significant dimensional surface magnification of up to 1000 times the area inspected for micro-surfaces, which allows easy processing and reaches an exceptional nanometric imprecision of measurements. According to the measurement principle, the sensitivity for displacement measurement using moiré technique depends on the frequency grating, for increase the detection resolution. This measurement technique can be used advantageously to measure the deformations generated by the production process or constraints on functional parts and the influence of these variations on the function. The optical device and optical principle, on which it is based, can be used for automated inspection of industrially produced goods. It can also be used for dimensional control when, for example, to quantify the error as to whether a piece is good or rubbish. It then suffices to compare a figure of moiré fringes with another previously recorded from a piece considered standard; which saves time, money and accuracy. The technique has found various applications in diverse fields, from biomedical to industrial and scientific applications.

  2. Hyperspectral Aerosol Optical Depths from TCAP Flights

    SciTech Connect

    Shinozuka, Yohei; Johnson, Roy R.; Flynn, Connor J.; Russell, P. B.; Schmid, Beat; Redemann, Jens; Dunagan, Stephen; Kluzek, Celine D.; Hubbe, John M.; Segal-Rosenheimer, Michal; Livingston, J. M.; Eck, T.; Wagener, Richard; Gregory, L.; Chand, Duli; Berg, Larry K.; Rogers, Ray; Ferrare, R. A.; Hair, John; Hostetler, Chris A.; Burton, S. P.

    2013-11-13

    4STAR (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research), the world’s first hyperspectral airborne tracking sunphotometer, acquired aerosol optical depths (AOD) at 1 Hz during all July 2012 flights of the Two Column Aerosol Project (TCAP). Root-mean square differences from AERONET ground-based observations were 0.01 at wavelengths between 500-1020 nm, 0.02 at 380 and 1640 nm and 0.03 at 440 nm in four clear-sky fly-over events, and similar in ground side-by-side comparisons. Changes in the above-aircraft AOD across 3-km-deep spirals were typically consistent with integrals of coincident in situ (on DOE Gulfstream 1 with 4STAR) and lidar (on NASA B200) extinction measurements within 0.01, 0.03, 0.01, 0.02, 0.02, 0.02 at 355, 450, 532, 550, 700, 1064 nm, respectively, despite atmospheric variations and combined measurement uncertainties. Finer vertical differentials of the 4STAR measurements matched the in situ ambient extinction profile within 14% for one homogeneous column. For the AOD observed between 350-1660 nm, excluding strong water vapor and oxygen absorption bands, estimated uncertainties were ~0.01 and dominated by (then) unpredictable throughput changes, up to +/-0.8%, of the fiber optic rotary joint. The favorable intercomparisons herald 4STAR’s spatially-resolved high-frequency hyperspectral products as a reliable tool for climate studies and satellite validation.

  3. New sputtering concept for optical precision coatings

    NASA Astrophysics Data System (ADS)

    Rademacher, Daniel; Bräuer, Günter; Vergöhl, Michael; Fritz, Benjamin; Zickenrott, Tobias

    2011-09-01

    The deposition of optical precision coatings on glass by magnetron sputtering is still a challenging problem regarding particle density and long term stability of coating plants due to target material erosion. A novel approach to increase process stability and reduce drifts is the usage of cylindrical cathodes. These cathodes allow a particle free deposition process as they have virtually no redeposition zones that can lead to destruction of coatings by arcing caused by surface charges. In the present paper optical single layers as well as multilayer coatings were sputtered by means of reactive magnetron sputtering using a double cylindrical cathode setup. The particle density is determined and compared to particles produced with planar magnetrons. A new sputter coater concept will be presented wherein the magnetrons are attached to a rotating disc coater in a sputter-up configuration. The process was stabilized by means of oxygen partial pressure control. Preliminary optical properties as well as deposition rates of different oxide films will be presented.

  4. Aerosol Optical Depth (AOD) Trends Over Bangladesh

    NASA Astrophysics Data System (ADS)

    Salam, A.

    2016-12-01

    An important omission in the Southeast Asian observing network is the border region with the Indian subcontinent. Significant amounts of pollution are generated and transported down the Indo-Gangenic Plain into the Bay of Bengal. High population density in a semi-arid region leads to the development of a complex mixture of absorbing pollution coupled with dust. Transport patterns of this mixture takes pollutants into Bangladesh, where more pollution is added to the atmosphere-leading to what is one of the highest non urban emission loading in the world (AOD500= 0.75 during the premonsoon season). Bangladesh is essentially a riverine country, and atmospheric outflow is over delta regions fed by over 500 rivers, including the Ganges, Bramaputra, Jamuna, and Padma systems forming the massive Meghna river. This combination of atmospheric and riverine components makes for an optically complex littoral region which challenges a host of environmental sensors and modeling systems. Data is needed to understand the sources, transport and optical characteristics of aerosol particles in the region. Dhaka (23.8103° N, 90.4125° E) is the capital of Bangladesh with a population of about 16 million. It has been growing rapidly with all the problem of a mega city. We have installed a sun photometer with NASA Aeronet project at the roof of the Chemistry Department, Dhaka University with other aerosol particles and gas measuring instruments. Bhola is an Island of the Bay of Bengal. It is surrounded by the Meghna River on the north and east, the Tatulia River on the west and the Bay of Bengal on the south. The observatory is located at Charfashion Bazar, Bhola (N 22o10´01″, E 90o45´00″, 3m asl). There is very little influence from traffic and industrial emissions. A Cimel sunphotometer (NASA AERONET) was installed for AOD measurements at this locations since 2013. Aerosol optical depth (AOD) trends between 2012 and 2016 at two different locations (Dhaka and Bhola) will be

  5. Aerosol optical depth characteristics in Yinchuan area

    NASA Astrophysics Data System (ADS)

    Zhang, Yaya; Mao, Jiandong; Rao, Zhimin; Zhang, Fan

    2013-08-01

    Sand dust aerosol is the main component of aerosol in troposphere atmosphere of East Asia, which can produce the extensive influence on the ecosystem, atmosphere environment and atmosphere chemistry through intensive sand dust weather process. For investigation of the aerosol optical depth (AOD) and its temporal-spatial evolution over this area, a series of observation experiments were carried out by a sun photometer CE-318 located at Beifang University of Nationality( 106°E, 38°29'N ), Yinchuan Ningxia province of China from September 2012 to April 2013 and many direct solar radiation datum were obtained. The experiments results were analyzed in detail and some conclusions are obtained as follows: (1) For daily evolution of AOD, the variation trend are divided into four types: ①the AOD values are relatively steady in whole day; ② the AOD values increase from morning to afternoon; ③ the AOD values are greater at noon than that in the morning and afternoon; ④there is a peak in the variation trends of AOD from 9:00~12:00 in the morning, but it is small at other time. (2) For month evolution, the minimum AOD average value appears in September and the maximum one appears in April. (3) For the seasonal changes trend, the average AOD values in the April are bigger than that in the autumn. (4) In addition, during the observation period, one dust weather process was observed and the change characteristic of AOD of dust aerosol was obtained and analyzed.

  6. Hyperspectral aerosol optical depths from TCAP flights

    SciTech Connect

    Shinozuka, Yohei; Johnson, Roy R; Flynn, Connor J; Russell, Philip B; Schmid, Beat

    2016-06-01

    4STAR (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research), a hyperspectral airborne sunphotometer, acquired aerosol optical depths (AOD) at 1 Hz during all July 2012 flights of the Two Column Aerosol Project (TCAP). Root-mean-square differences from AERONET ground-based observations were 0.01 at wavelengths between 500-1020 nm, 0.02 at 380 and 1640 nm and 0.03 at 440 nm in four clear-sky fly-over events, and similar in ground side-by-side comparisons. Changes in the above-aircraft AOD across 3- km-deep spirals were typically consistent with integrals of coincident in situ (on DOE Gulfstream 1 with 4STAR) and lidar (on NASA B200) extinction measurements within 0.01, 0.03, 0.01, 0.02, 0.02, 0.02 at 355, 450, 532, 550, 700, 1064 nm, respectively, despite atmospheric variations and combined measurement uncertainties. Finer vertical differentials of the 4STAR measurements matched the in situ ambient extinction profile within 14% for one homogeneous column. For the AOD observed between 350-1660 nm, excluding strong

  7. The Navy Precision Optical Interferometer: an update

    NASA Astrophysics Data System (ADS)

    Armstrong, J. T.; Baines, Ellyn K.; Schmitt, Henrique R.; Restaino, Sergio R.; Clark, James H.; Benson, James A.; Hutter, Donald J.; Zavala, Robert T.; van Belle, Gerard T.

    2016-08-01

    We describe the current status of the Navy Precision Optical Interferometer (NPOI), including developments since the last SPIE meeting. The NPOI group has added stations as far as 250m from the array center and added numerous infrastructure improvements. Science programs include stellar diameters and limb darkening, binary orbits, Be star disks, exoplanet host stars, and progress toward high-resolution stellar surface imaging. Technical and infrastructure projects include on-sky demonstrations of baseline bootstrapping with six array elements and of the VISION beam combiner, control system updates, integration of the long delay lines, and updated firmware for the Classic beam combiner. Our plans to add up to four 1.8 m telescopes are no longer viable, but we have recently acquired separate funding for adding three 1 m AO-equipped telescopes and an infrared beam combiner to the array.

  8. Improved evaluation of optical depth components from Langley plot data

    NASA Technical Reports Server (NTRS)

    Biggar, S. F.; Gellman, D. I.; Slater, P. N.

    1990-01-01

    A simple, iterative procedure to determine the optical depth components of the extinction optical depth measured by a solar radiometer is presented. Simulated data show that the iterative procedure improves the determination of the exponent of a Junge law particle size distribution. The determination of the optical depth due to aerosol scattering is improved as compared to a method which uses only two points from the extinction data. The iterative method was used to determine spectral optical depth components for June 11-13, 1988 during the MAC III experiment.

  9. Smoke optical depths - Magnitude, variability, and wavelength dependence

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Russell, P. B.; Colburn, D. A.; Ackerman, T. P.; Allen, D. A.

    1988-01-01

    An airborne autotracking sun-photometer has been used to measure magnitudes, temporal/spatial variabilities, and the wavelength dependence of optical depths in the near-ultraviolet to near-infrared spectrum of smoke from two forest fires and one jet fuel fire and of background air. Jet fuel smoke optical depths were found to be generally less wavelength dependent than background aerosol optical depths. Forest fire smoke optical depths, however, showed a wide range of wavelength depedences, such as incidents of wavelength-independent extinction.

  10. Ultra-precision turning of complex spiral optical delay line

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodong; Li, Po; Fang, Fengzhou; Wang, Qichang

    2011-11-01

    Optical delay line (ODL) implements the vertical or depth scanning of optical coherence tomography, which is the most important factor affecting the scanning resolution and speed. The spinning spiral mirror is found as an excellent optical delay device because of the high-speed and high-repetition-rate. However, it is one difficult task to machine the mirror due to the special shape and precision requirement. In this paper, the spiral mirror with titled parabolic generatrix is proposed, and the ultra-precision turning method is studied for its machining using the spiral mathematic model. Another type of ODL with the segmental shape is also introduced and machined to make rotation balance for the mass equalization when scanning. The efficiency improvement is considered in details, including the rough cutting with the 5- axis milling machine, the machining coordinates unification, and the selection of layer direction in turning. The onmachine measuring method based on stylus gauge is designed to analyze the shape deviation. The air bearing is used as the measuring staff and the laser interferometer sensor as the position sensor, whose repeatability accuracy is proved up to 10nm and the stable feature keeps well. With this method developed, the complex mirror with nanometric finish of 10.7nm in Ra and the form error within 1um are achieved.

  11. All-optical depth coloring based on directional gating.

    PubMed

    Lim, Sungjin; Kim, Mugeon; Hahn, Joonku

    2016-09-19

    In non-contacting depth extraction there are several issues, such as the accuracy and the measurement speed. In the issue of the measurement speed, the computation cost for image processing is significant. We present an all-optical depth extraction method by coloring objects according to their depth. Our system is operated fully optically and both encoding and decoding processes are optically performed. Therefore, all-optical depth coloring has a distinct advantage to extract the depth information in real time without any computation cost. We invent a directional gating method to extract the points from the object which are positioned at the same distance. Based on this method, the objects look painted by different colors according to the distance when the objects are observed through our system. In this paper, we demonstrate the all-optical depth coloring system and verify the feasibility of our method.

  12. Effects of Ocular Optics on Perceived Visual Direction and Depth

    NASA Astrophysics Data System (ADS)

    Ye, Ming

    Most studies of human retinal image quality have specifically addressed the issues of image contrast, few have examined the problem of image location. However, one of the most impressive properties of human vision involves the location of objects. We are able to identify object location with great accuracy (less than 5 arcsec). The sensitivity we exhibit for image location indicates that any optical errors, such as refractive error, ocular aberrations, pupil decentration, etc., may have noticeable effects on perceived visual direction and distance of objects. The most easily observed effects of these optical factors is a binocular depth illusion called chromostereopsis in which equidistance colored objects appear to lie at the different distances. This dissertation covers a series of theoretical and experimental studies that examined the effects of ocular optics on perceived monocular visual direction and binocular chromostereopsis. Theoretical studies included development of an adequate eye model for predicting chromatic aberration, a major ocular aberration, using geometric optics. Also, a wave optical analysis is used to model the effects of defocus, optical aberrations, Stiles-Crawford effect (SCE) and pupil location on retinal image profiles. Experimental studies used psychophysical methods such as monocular vernier alignment tests, binocular stereoscopic tests, etc. This dissertation concludes: (1) With a decentered large pupil, the SCE reduces defocused image shifts compare to an eye without the SCE. (2) The blurred image location can be predicted by the centroid of the image profile. (3) Chromostereopsis with small pupils can be precisely accounted for by the interocular difference in monocular transverse chromatic aberration. (4) The SCE also plays an important role in the effect of pupil size on chromostereopsis. The reduction of chromostereopsis with large pupils can be accurately predicted by the interocular difference in monocular chromatic diplopia

  13. Optical vortex beam based optical fan for high-precision optical measurements and optical switching.

    PubMed

    Zhou, Zhi-Yuan; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen

    2014-09-01

    The polarization and orbital angular momentum properties of light are of great importance in optical science and technology in the fields of high-precision optical measurements and high-capacity and high-speed optical communications. Here we show a method for the construction of a simple and robust scheme to rotate a light beam such as a fan, which is based on a combination of these two properties and using the thermal-dispersion and electro-optical effect of birefringent crystals. Using a computer-based digital image-processing technique, we determine the temperature and thermal-dispersion difference of the crystal with high resolution. We also use the rotation phenomenon to realize thermo-optic and electro-optic switches. The basic operating principles for measurement and switching processes are presented in detail. The methods developed here will have wide practical applicability in various fields, including remote sensing, materials science, and optical communication networks.

  14. Black Hole Advective Accretion Disks with Optical Depth Transition

    SciTech Connect

    Artemove, Y.V.; Bisnovatyi-Kogan, G.S.; Igumenshchev, I.V.; Novikov, I.D.

    2006-02-01

    We have constructed numerically global solutions of advective accretion disks around black holes that describe a continuous transition between the effectively optically thick outer and optically thin inner disk regions. We have concentrated on models of accretion flows with large mass accretion rates, and we have employed a bridging formula for radiative losses at high and low effective optical depths.

  15. Microphysical and Dynamical Influences on Cirrus Cloud Optical Depth Distributions

    SciTech Connect

    Kay, J.; Baker, M.; Hegg, D.

    2005-03-18

    Cirrus cloud inhomogeneity occurs at scales greater than the cirrus radiative smoothing scale ({approx}100 m), but less than typical global climate model (GCM) resolutions ({approx}300 km). Therefore, calculating cirrus radiative impacts in GCMs requires an optical depth distribution parameterization. Radiative transfer calculations are sensitive to optical depth distribution assumptions (Fu et al. 2000; Carlin et al. 2002). Using raman lidar observations, we quantify cirrus timescales and optical depth distributions at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in Lamont, OK (USA). We demonstrate the sensitivity of outgoing longwave radiation (OLR) calculations to assumed optical depth distributions and to the temporal resolution of optical depth measurements. Recent work has highlighted the importance of dynamics and nucleation for cirrus evolution (Haag and Karcher 2004; Karcher and Strom 2003). We need to understand the main controls on cirrus optical depth distributions to incorporate cirrus variability into model radiative transfer calculations. With an explicit ice microphysics parcel model, we aim to understand the influence of ice nucleation mechanism and imposed dynamics on cirrus optical depth distributions.

  16. Aerosol spectral optical depths: Jet fuel and forest fire smokes

    NASA Astrophysics Data System (ADS)

    Pueschel, R. F.; Livingston, J. M.

    1990-12-01

    The Ames autotracking airborne sun photometer was used to investigate the spectral optical depth between 380 and 1020 nm of smokes from a jet fuel pool fire and a forest fire in May and August 1988, respectively. Results show that the forest fire smoke exhibited a stronger wavelength dependence of optical depths than did the jet fuel fire smoke at optical depths less than unity. At optical depths greater than or equal to 1, both smokes showed neutral wavelength dependence, similar to that of an optically thin stratus deck. These results verify findings of earlier investigations and have implications both on the climatic impact of large-scale smokes and on the wavelength-dependent transmission of electromagnetic signals.

  17. Electro-optical liquid depth sensor

    NASA Technical Reports Server (NTRS)

    Heppner, D. B.; Atwood, S. O.

    1976-01-01

    Transducer utilizes absorptive properties of water to determine variations in depth without disturbing liquid. Instrument is inexpensive, simple, and small and thus can be used in lieu of direct graduated scale readout or capacitive, ultrasonic, resistive or inducive sensors when these are impractical because of complexity or cost.

  18. Wavelength dependence of the effective cloud optical depth

    NASA Astrophysics Data System (ADS)

    Serrano, D.; Marín, M. J.; Núñez, M.; Utrillas, M. P.; Gandía, S.; Martínez-Lozano, J. A.

    2015-08-01

    This study examines the wavelength dependence of cloud optical depth. To accomplish this task two different wavelength bands of the solar spectrum were considered in the cloud optical depth retrieval which was conducted in Valencia, Spain. The first retrieval used global irradiance measurements in the UVER range taken from a YES-UVB-1 radiometer in combination with multiple scattering model estimates; while the second retrieval was obtained in the Broadband range, with measurements of global solar surface irradiance from a CM6 pyranometer and a multiple scattering model. Whilst the dependence of the cloud optical depth (τ) on the wavelength is small, the best result was displayed by the SBDART model with less than 2% deviation between two ranges and moderately worse results were obtained with the LibRadtran model. Finally, seasonal statistical data for optical depth are presented for 2011 and 2012.

  19. Towards Improved Cirrus Cloud Optical Depths from CALIPSO

    NASA Astrophysics Data System (ADS)

    Garnier, Anne; Vaughan, Mark; Pelon, Jacques; Winker, David; Trepte, Chip; Young, Stuart

    2016-06-01

    This paper reviews recent advances regarding the retrieval of optical depths of semi-transparent cirrus clouds using synergetic analyses of perfectly collocated observations from the CALIOP lidar and the IIR infrared radiometer aboard the CALIPSO satellite.

  20. Aerosol spectral optical depths - Jet fuel and forest fire smokes

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Livingston, J. M.

    1990-01-01

    The Ames autotracking airborne sun photometer was used to investigate the spectral depth between 380 and 1020 nm of smokes from a jet fuel pool fire and a forest fire in May and August 1988, respectively. Results show that the forest fire smoke exhibited a stronger wavelength dependence of optical depths than did the jet fuel fire smoke at optical depths less than unity. At optical depths greater than or equal to 1, both smokes showed neutral wavelength dependence, similar to that of an optically thin stratus deck. These results verify findings of earlier investigations and have implications both on the climatic impact of large-scale smokes and on the wavelength-dependent transmission of electromagnetic signals.

  1. Aerosol Optical Depth Value-Added Product Report

    SciTech Connect

    Koontz, A; Hodges, G; Barnard, J; Flynn, C; Michalsky, J

    2013-03-17

    This document describes the process applied to retrieve aerosol optical depth (AOD) from multifilter rotating shadowband radiometers (MFRSR) and normal incidence multifilter radiometers (NIMFR) operated at the ARM Climate Research Facility’s ground-based facilities.

  2. Precision-analog fiber-optic transmission system

    SciTech Connect

    Stover, G.

    1981-06-01

    This article describes the design, experimental development, and construction of a DC-coupled precision analog fiber optic link. Topics to be covered include overall electrical and mechanical system parameters, basic circuit organization, modulation format, optical system design, optical receiver circuit analysis, and the experimental verification of the major design parameters.

  3. Optical cryptography with biometrics for multi-depth objects.

    PubMed

    Yan, Aimin; Wei, Yang; Hu, Zhijuan; Zhang, Jingtao; Tsang, Peter Wai Ming; Poon, Ting-Chung

    2017-10-11

    We propose an optical cryptosystem for encrypting images of multi-depth objects based on the combination of optical heterodyne technique and fingerprint keys. Optical heterodyning requires two optical beams to be mixed. For encryption, each optical beam is modulated by an optical mask containing either the fingerprint of the person who is sending, or receiving the image. The pair of optical masks are taken as the encryption keys. Subsequently, the two beams are used to scan over a multi-depth 3-D object to obtain an encrypted hologram. During the decryption process, each sectional image of the 3-D object is recovered by convolving its encrypted hologram (through numerical computation) with the encrypted hologram of a pinhole image that is positioned at the same depth as the sectional image. Our proposed method has three major advantages. First, the lost-key situation can be avoided with the use of fingerprints as the encryption keys. Second, the method can be applied to encrypt 3-D images for subsequent decrypted sectional images. Third, since optical heterodyning scanning is employed to encrypt a 3-D object, the optical system is incoherent, resulting in negligible amount of speckle noise upon decryption. To the best of our knowledge, this is the first time optical cryptography of 3-D object images has been demonstrated in an incoherent optical system with biometric keys.

  4. Mechanism Design Principle for Optical-Precision, Deployable Instruments

    NASA Technical Reports Server (NTRS)

    Lake, Mark S.; Hachkowski, M. Roman

    2000-01-01

    The present paper is intended to be a guide for the design of 'microdynamically quiet' deployment mechanisms for optical-precision structures, such as deployable telescope mirrors and optical benches. Many of the guidelines included herein come directly from the field of optomechanical engineering, and are neither newly developed guidelines nor are they uniquely applicable to high-precision deployment mechanisms. However, the application of these guidelines to the design of deployment mechanisms is a rather new practice, so efforts are made herein to illustrate the process through the discussion of specific examples. The present paper summarizes a more extensive set of design guidelines for optical-precision mechanisms that are under development.

  5. Depth.

    PubMed

    Koenderink, Jan J; van Doorn, Andrea J; Wagemans, Johan

    2011-01-01

    Depth is the feeling of remoteness, or separateness, that accompanies awareness in human modalities like vision and audition. In specific cases depths can be graded on an ordinal scale, or even measured quantitatively on an interval scale. In the case of pictorial vision this is complicated by the fact that human observers often appear to apply mental transformations that involve depths in distinct visual directions. This implies that a comparison of empirically determined depths between observers involves pictorial space as an integral entity, whereas comparing pictorial depths as such is meaningless. We describe the formal structure of pictorial space purely in the phenomenological domain, without taking recourse to the theories of optics which properly apply to physical space-a distinct ontological domain. We introduce a number of general ways to design and implement methods of geodesy in pictorial space, and discuss some basic problems associated with such measurements. We deal mainly with conceptual issues.

  6. Depth

    PubMed Central

    Koenderink, Jan J; van Doorn, Andrea J; Wagemans, Johan

    2011-01-01

    Depth is the feeling of remoteness, or separateness, that accompanies awareness in human modalities like vision and audition. In specific cases depths can be graded on an ordinal scale, or even measured quantitatively on an interval scale. In the case of pictorial vision this is complicated by the fact that human observers often appear to apply mental transformations that involve depths in distinct visual directions. This implies that a comparison of empirically determined depths between observers involves pictorial space as an integral entity, whereas comparing pictorial depths as such is meaningless. We describe the formal structure of pictorial space purely in the phenomenological domain, without taking recourse to the theories of optics which properly apply to physical space—a distinct ontological domain. We introduce a number of general ways to design and implement methods of geodesy in pictorial space, and discuss some basic problems associated with such measurements. We deal mainly with conceptual issues. PMID:23145244

  7. A disposable flexible skin patch for clinical optical perfusion monitoring at multiple depths

    NASA Astrophysics Data System (ADS)

    Farkas, Dana L.; Kolodziejski, Noah J.; Stapels, Christopher J.; McAdams, Daniel R.; Fernandez, Daniel E.; Podolsky, Matthew J.; Christian, James F.; Ward, Brent B.; Vartarian, Mark; Feinberg, Stephen E.; Lee, Seung Yup; Parikh, Urmi; Mycek, Mary-Ann; Joyner, Michael J.; Johnson, Christopher P.; Paradis, Norman A.

    2016-03-01

    Stable, relative localization of source and detection fibers is necessary for clinical implementation of quantitative optical perfusion monitoring methods such as diffuse correlation spectroscopy (DCS) and diffuse reflectance spectroscopy (DRS). A flexible and compact device design is presented as a platform for simultaneous monitoring of perfusion at a range of depths, enabled by precise location of optical fibers in a robust and secure adhesive patch. We will discuss preliminary data collected on human subjects in a lower body negative pressure model for hypovolemic shock. These data indicate that this method facilitates simple and stable simultaneous monitoring of perfusion at multiple depths and within multiple physiological compartments.

  8. Design of precise assembly equipment of large aperture optics

    NASA Astrophysics Data System (ADS)

    Pei, Guoqing; Xu, Xu; Xiong, Zhao; Yan, Han; Qin, Tinghai; Zhou, Hai; Yuan, Xiaodong

    2017-05-01

    High-energy solid-state laser is an important way to achieve laser fusion research. Laser fusion facility includes thousands of various types of large aperture optics. These large aperture optics should be assembled with high precision and high efficiency. Currently, however, the assembly of large aperture optics is by man's hand which is in low level of efficiency and labor-intensive. Here, according to the characteristics of the assembly of large aperture optics, we designed three kinds of grasping devices. Using Finite Element Method, we simulated the impact of the grasping device on the PV value and the RMS value of the large aperture optics. The structural strength of the grasping device's key part was analyzed. An experiment was performed to illustrate the reliability and precision of the grasping device. We anticipate that the grasping device would complete the assembly of large aperture optics precisely and efficiently.

  9. Optical Frequency Synthesizer for Precision Spectroscopy

    NASA Astrophysics Data System (ADS)

    Holzwarth, R.; Udem, Th.; Hänsch, T. W.; Knight, J. C.; Wadsworth, W. J.; Russell, P. St. J.

    2000-09-01

    We have used the frequency comb generated by a femtosecond mode-locked laser and broadened to more than an optical octave in a photonic crystal fiber to realize a frequency chain that links a 10 MHz radio frequency reference phase-coherently in one step to the optical region. By comparison with a similar frequency chain we set an upper limit for the uncertainty of this new approach to 5.1×10-16. This opens the door for measurement and synthesis of virtually any optical frequency and is ready to revolutionize frequency metrology.

  10. Precision depth measurement of through silicon vias (TSVs) on 3D semiconductor packaging process.

    PubMed

    Jin, Jonghan; Kim, Jae Wan; Kang, Chu-Shik; Kim, Jong-Ahn; Lee, Sunghun

    2012-02-27

    We have proposed and demonstrated a novel method to measure depths of through silicon vias (TSVs) at high speed. TSVs are fine and deep holes fabricated in silicon wafers for 3D semiconductors; they are used for electrical connections between vertically stacked wafers. Because the high-aspect ratio hole of the TSV makes it difficult for light to reach the bottom surface, conventional optical methods using visible lights cannot determine the depth value. By adopting an optical comb of a femtosecond pulse laser in the infra-red range as a light source, the depths of TSVs having aspect ratio of about 7 were measured. This measurement was done at high speed based on spectral resolved interferometry. The proposed method is expected to be an alternative method for depth inspection of TSVs.

  11. Achievable Precision for Optical Ranging Systems

    NASA Technical Reports Server (NTRS)

    Moision, Bruce; Erkmen, Baris I.

    2012-01-01

    Achievable RMS errors in estimating the phase, frequency, and intensity of a direct-detected intensity-modulated optical pulse train are presented. For each parameter, the Cramer-Rao-Bound (CRB) is derived and the performance of the Maximum Likelihood estimator is illustrated. Approximations to the CRBs are provided, enabling an intuitive understanding of estimator behavior as a function of the signaling parameters. The results are compared to achievable RMS errors in estimating the same parameters from a sinusoidal waveform in additive white Gaussian noise. This establishes a framework for a performance comparison of radio frequency (RF) and optical science. Comparisons are made using parameters for state-of-the-art deep-space RF and optical links. Degradations to the achievable errors due to clock phase noise and detector jitter are illustrated.

  12. Manipulating Mechanics and Chemistry in Precision Optics Finishing

    SciTech Connect

    Jacobs, S.D.

    2007-05-30

    Deterministic processing is critical to modern precision optics finishing. Put simply, determinism is the ability to predict an outcome before carrying out an activity. With the availability of computer numerically controlled (CNC) equipment and sophisticated software algorithms, it is now possible to grind and polish optics from a variety of materials to surface shape accuracies of ~20 nm peak-to-valley (p-v), with surface roughness values (measured on white light interferometers over 250 um x 350 um areas) to sub-nm root-mean-square (rms) levels. In the grinding phase the capability now exists to estimate removal rates, surface roughness, and the depth of subsurface damage (SSD) for a previously unprocessed material, knowing its Young's modulus, hardness, and fracture toughness. An understanding of how chemistry aids in the abrasive-driven removal of material from the surface during polishing is also critical, Recent polishing process research reveals the importance of chemistry, specifically slurry pH, for preventing particle agglomeration in order to achieve smooth surface finishes with conventional pad or pitch laps. New sub-aperture polishing processes like magnetorheoogical finishing (MRF) can smooth and shape flat, spherical, aspheric and free-form surfaces within a few process iterations. Difficult to finish optical materials like soft polymer polymethyl methacrylate, microstructured polycrystalline zinc sulfide, and water soluble single-crystal potassium dihydrogen phosphate (KDP) can be finished with MRF. The key is the systematic alteration of MR fluid chemistry and mechanics (i.e. the abrasive) to match the unique physical properties of each workpiece.

  13. Depth Profilometry via Multiplexed Optical High-Coherence Interferometry

    PubMed Central

    Kazemzadeh, Farnoud; Wong, Alexander; Behr, Bradford B.; Hajian, Arsen R.

    2015-01-01

    Depth Profilometry involves the measurement of the depth profile of objects, and has significant potential for various industrial applications that benefit from non-destructive sub-surface profiling such as defect detection, corrosion assessment, and dental assessment to name a few. In this study, we investigate the feasibility of depth profilometry using an Multiplexed Optical High-coherence Interferometry MOHI instrument. The MOHI instrument utilizes the spatial coherence of a laser and the interferometric properties of light to probe the reflectivity as a function of depth of a sample. The axial and lateral resolutions, as well as imaging depth, are decoupled in the MOHI instrument. The MOHI instrument is capable of multiplexing interferometric measurements into 480 one-dimensional interferograms at a location on the sample and is built with axial and lateral resolutions of 40 μm at a maximum imaging depth of 700 μm. Preliminary results, where a piece of sand-blasted aluminum, an NBK7 glass piece, and an optical phantom were successfully probed using the MOHI instrument to produce depth profiles, demonstrate the feasibility of such an instrument for performing depth profilometry. PMID:25803289

  14. Precise earthquake locations show evidence of internal structures at intermediate-depth earthquake nests

    NASA Astrophysics Data System (ADS)

    Prieto, G.; Florez, M.; Dionicio, V.; Barrett, S. A.; Beroza, G. C.

    2012-12-01

    The mechanism for intermediate depth and deep earthquakes is still under debate. The temperatures and pressures are above the point where ordinary fractures ought to occur. Earthquake nests are regions of highly concentrated seismicity within subducting lithosphere that are isolated from nearby activity and may be key in revealing the mechanics of intermediate-depth earthquakes. We present precise earthquake locations of intermediate-depth earthquakes in the Bucaramanga nest, Colombia using double-difference algorithms combined with depth phases recorded at regional and teleseismic distances. Our results show an alignment of seismicity along subhorizontal and/or subvertical regions within the nest and a preferential location of larger earthquakes at the bottom of the cluster. These observed features might suggest preexisting structures within the subducting slab or some process that allows concentration of deformation and repeating ruptures along fractures.

  15. Validation of MODIS Aerosol Optical Depth Retrieval Over Land

    NASA Technical Reports Server (NTRS)

    Chu, D. A.; Kaufman, Y. J.; Ichoku, C.; Remer, L. A.; Tanre, D.; Holben, B. N.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Aerosol optical depths are derived operationally for the first time over land in the visible wavelengths by MODIS (Moderate Resolution Imaging Spectroradiometer) onboard the EOSTerra spacecraft. More than 300 Sun photometer data points from more than 30 AERONET (Aerosol Robotic Network) sites globally were used in validating the aerosol optical depths obtained during July - September 2000. Excellent agreement is found with retrieval errors within (Delta)tau=+/- 0.05 +/- 0.20 tau, as predicted, over (partially) vegetated surfaces, consistent with pre-launch theoretical analysis and aircraft field experiments. In coastal and semi-arid regions larger errors are caused predominantly by the uncertainty in evaluating the surface reflectance. The excellent fit was achieved despite the ongoing improvements in instrument characterization and calibration. This results show that MODIS-derived aerosol optical depths can be used quantitatively in many applications with cautions for residual clouds, snow/ice, and water contamination.

  16. Precision molding techniques for optical waveguide devices

    NASA Astrophysics Data System (ADS)

    Kalveram, Stefan; Neyer, Andreas

    1997-09-01

    Single-mode optical waveguide devices with integrated fiber- alignment grooves have been fabricated by injection molding of structured substrates and by subsequent filling of the waveguide channels with higher refractive index polymer. The master forms of the microstructures have been micro-machined channels with higher refractive index polymers. The master forms of the microstructures have been micro-machined in silicon. A special injection molding tool has been developed to yield plastic substrate chips with high surface planarity and replicated microstructures with details in the submicron range. Hot embossing is a further technology applied for the fabrication of large area waveguide devices with integrated mirrors, mainly intended for optical backplane applications. The hot embossing tool is driven on an injection molding machine which is a more cost effective method than the acquisition of conventional hot embossing equipment. In this paper, the injection molding as well as the hot embossing tool will be described together with the process and the results in the field of passive components for optical telecommunications and datacommunications.

  17. Measuring Mean Cup Depth in the Optic Nerve Head

    PubMed Central

    Johnstone, John K.; Rhodes, Lindsay; Fazio, Massimo; Smith, Brandon; Wang, Lan; Downs, J. Crawford; Owsley, Cynthia; Girkin, Christopher A.

    2016-01-01

    Since the deformation of structures in the optic nerve head (ONH) is associated with glaucoma and other diseases of the optic nerve, measurement of this deformation is of current research interest. This paper considers the computation of cup depth, a measurement of the depth of the internal limiting membrane (ILM). The computation of cup depth requires a reference structure against which to measure the ILM, and the construction of two reference structures is discussed, one based on Bruch's membrane opening (BMO) and the other based on the anterior surface of the peripapillary sclera (AS). A main focus of the paper is the robust computation of mean cup depth, which requires a good sampling of a reconstruction of the ILM surface. To evaluate our algorithm, the construction of synthetic datasets is considered. PMID:27942258

  18. Optics for multimode lasers with elongated depth of field

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim; Ostrun, Aleksei

    2017-02-01

    Modern multimode high-power lasers are widely used in industrial applications and control of their radiation, especially by focusing, is of great importance. Because of relatively low optical quality, characterized by high values of specifications Beam Parameter Product (BPP) or M², the depth of field by focusing of multimode laser radiation is narrow. At the same time laser technologies like deep penetration welding, cutting of thick metal sheets get benefits from elongated depth of field in area of focal plane, therefore increasing of zone along optical axis with minimized spot size is important technical task. As a solution it is suggested to apply refractive optical systems splitting an initial laser beam into several beamlets, which are focused in different foci separated along optical axis with providing reliable control of energy portions in each separate focus, independently of beam size or mode structure. With the multi-focus optics, the length of zone of material processing along optical axis is defined rather by distances between separate foci, which are determined by optical design of the optics and can be chosen according to requirements of a particular laser technology. Due to stability of the distances between foci there is provided stability of a technology process. This paper describes some design features of refractive multi-focus optics, examples of real implementations and experimental results will be presented as well.

  19. Estimate of water inherent optical properties from Secchi depth

    NASA Astrophysics Data System (ADS)

    Levin, I. M.; Radomyslskaya, T. M.

    2012-04-01

    This paper suggests a new version of the Secchi disk theory which shows a connection between Secchi depth measurements and inherent optical properties (IOP) of water such as the extinction coefficient, the single scattering albedo, and the backscattering coefficient. Ways around Preisendorfer's objection to using measurements of the Secchi depth for determining the IOP are proposed. This theory is compared with a marine experiment and its accuracy under different conditions is estimated.

  20. Neutron depth profiling study of lithium niobate optical waveguides

    NASA Astrophysics Data System (ADS)

    Kolářova, P.; Vacík, J.; Špirková-Hradilová, J.; Červená, J.

    1998-05-01

    The relation between optical properties and the structure of proton exchanged and annealed proton exchanged optical waveguides in lithium niobate was studied using the mode spectroscopy and neutron depth profiling methods. We have found a close correlation between the lithium depletion and the depth profile of the extraordinary refractive index. The form of the observed dependence between Li depletion and refractive index depends on the fabrication procedure by which the waveguide was prepared but it is highly reproducible for specimens prepared by the same procedure.

  1. Seasonal and Interannual Variability of Polar Stratospheric Cloud Optical Depth

    NASA Astrophysics Data System (ADS)

    Pitts, M. C.; Poole, L. R.; Thomason, L. W.; Damadeo, R. P.

    2013-12-01

    In addition to their important role in ozone depletion, polar stratospheric clouds (PSCs) may also impact stratospheric radiation and dynamics. Earlier studies indicated that PSCs could significantly affect radiative heating rates, but the magnitude and even the sign of the effect varied greatly from study to study, depending on many factors, e.g. PSC optical depth and underlying tropospheric cloud cover. A more recent study, which assumed nominal PSC conditions of 100% cloud fraction and visible optical depth of 0.01 for non-ice PSCs and 0.04 for ice PSCs, suggested that PSCs could produce significant perturbations to the radiative heating rates in the Antarctic stratosphere. A comprehensive evaluation of the radiative effects of PSCs requires more accurate knowledge of PSC characteristics over the entire polar region and throughout complete seasons. With the advent of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission in 2006, a more complete picture of PSC composition and occurrence is now emerging. The polarization-sensitive CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) lidar system onboard the CALIPSO spacecraft is acquiring, on average, over 300,000 backscatter profiles per day at latitudes poleward of 55° (including the polar night region up to 82°), providing a unique opportunity to examine the distribution of PSC optical depth on vortex-wide scales and over entire PSC seasons. In this paper, we describe an approach to calculate PSC optical depth from the CALIOP 532-nm attenuated backscatter measurements. We retrieve the PSC extinction profile downward from cloud top using a composition-dependent extinction-to-backscatter ratio and then integrate the extinction profile to derive PSC optical depth. We then examine this multi-year PSC optical depth record to determine the spatial and seasonal variability for the Arctic and Antarctic, respectively. Multi-year composites provide insight to the interannual

  2. Dual focus diffractive optical element with extended depth of focus

    NASA Astrophysics Data System (ADS)

    Uno, Katsuhiro; Shimizu, Isao

    2014-09-01

    A dual focus property and an extended depth of focus were verified by a new type of diffractive lens displaying on liquid crystal on silicon (LCoS) devices. This type of lens is useful to read information on multilayer optical discs and tilted discs. The radial undulation of the phase groove on the diffractive lens gave the dual focus nature. The focal extension was performed by combining the dual focus lens with the axilens that was invented for expanding the depth of focus. The number of undulations did not affect the intensity along the optical axis but the central spot of the diffraction pattern.

  3. Depth selective diffuse optical computed topography: simulations and phantom experiments

    NASA Astrophysics Data System (ADS)

    Fujii, M.; Kawanaka, A.; Nakayama, K.

    2007-07-01

    Diffuse optical topography has excellent features as a noninvasive method that provides 2D location information of cortical activity. However, it cannot distinguish the activation depth. We propose an image reconstruction algorithm that suppresses undesirable effects of skin circulation. It comprises a filtering algorithm that extracts target signals from observation data contaminated by disturbing signals and a 2D visualizing process. Computer simulations revealed its excellent performance. We developed a depth selective diffuse optical topography system prototype and performed phantom experiments. Our algorithm significantly suppressed the influence of the disturbing body in the shallow plane with minimal degradation of the target signal.

  4. Ultrasound-modulated optical tomography at new depth

    PubMed Central

    Lai, Puxiang; Xu, Xiao

    2012-01-01

    Abstract. Ultrasound-modulated optical tomography (UOT) has the potential to reveal optical contrast deep inside soft biological tissues at an ultrasonically determined spatial resolution. The optical imaging depth reported so far has, however, been limited, which prevents this technique from broader applications. Our latest experimental exploration has pushed UOT to an unprecedented imaging depth. We developed and optimized a UOT system employing a photorefractive crystal-based interferometer. A large aperture optical fiber bundle was used to enhance the efficiencies for diffuse light collection and photorefractive two-wave-mixing. Within the safety limits for both laser illumination and ultrasound modulation, the system has attained the ability to image through a tissue-mimicking phantom of 9.4 cm in thickness, which has never been reached previously by UOT. PMID:22734762

  5. Surface precision of optical membranes with curvature.

    PubMed

    Marker, D; Jenkins, C

    1997-11-24

    Space-based inflatable technology is of current interest to NASA and DOD, and in particular to the Air Force and Phillips Laboratory. Potentially large gains in lowering launch costs, through reductions in structure mass and volume, are driving this activity. Diverse groups are researching and developing this technology for radio and radar antennae, optical telescopes, and solar power and propulsion applications. Regardless of the use, one common requirement for successful application is the accuracy of the inflated surface shape. The work reported here concerns the shape control of an inflated thin circular disk through use of a nonlinear finite element analysis. First, a review of the important associated Hencky problem is given. Then we discuss a shape modification, achieved through enforced boundary displacements, which resulted in moving the inflated shape towards a desired parabolic profile. Minimization of the figure error is discussed and conclusions are drawn.

  6. Optical fiber couplers for precision spaceborne metrology.

    PubMed

    Killow, Christian J; Fitzsimons, Ewan D; Perreur-Lloyd, Michael; Robertson, David I; Ward, Henry; Bogenstahl, Johanna

    2016-04-01

    We describe the optical and mechanical design, construction philosophy, and testing of a pair of matched, spaceflight-qualified fiber couplers. The couplers were developed for the LISA Pathfinder mission but are relevant for other applications-both on ground and in space-where a robust fiber coupler with well-controlled beam parameters and stable beam pointing is required. This particular implementation of the design called for two couplers providing collimated beams with individual waist sizes and positions. The target values were a 522 μm waist 145 mm after the collimating lens for one coupler and a virtual 520 μm waist 194 mm before the collimating lens for the second coupler. Values of (542±4)  μm at (142±19) mm and (500±8)  μm at (-275±8)  mm were achieved, fully meeting the mission requirements. To control spurious noise effects in the interferometer, the optical system design also specified tight limits on relative beam curvature at an intended interference point. With nominal curvatures at this location of ∼2.35  m, the matching between the outputs of the two fiber couplers was measured to be λ/33 peak-valley over the central 1 mm of the beams. Results showing pointing stability of 3 μrad/°C over a 50°C range are presented. The vibration, shock, and thermal vacuum environmental testing conditions to which a pair of qualification fiber couplers were subjected-without change in performance-are listed.

  7. Perspective on precision machining, polishing, and optical requirements

    SciTech Connect

    Sanger, G.M.

    1981-08-18

    While precision machining has been applied to the manufacture of optical components for a considerable period, the process has, in general, had its thinking restricted to producing only the accurate shapes required. The purpose of this paper is to show how optical components must be considered from an optical (functional) point of view and that the manufacturing process must be selected on that basis. To fill out this perspective, simplistic examples of how optical components are specified with respect to form and finish are given, a comparison between optical polishing and precision machining is made, and some thoughts on which technique should be selected for a specific application are presented. A short discussion of future trends related to accuracy, materials, and tools is included.

  8. Automatic and Precise Localization and Cortical Labeling of Subdural and Depth Intracranial Electrodes

    PubMed Central

    Qin, Chaoyi; Tan, Zheng; Pan, Yali; Li, Yanyan; Wang, Lin; Ren, Liankun; Zhou, Wenjing; Wang, Liang

    2017-01-01

    Object: Subdural or deep intracerebral electrodes are essential in order to precisely localize epileptic zone in patients with medically intractable epilepsy. Precise localization of the implanted electrodes is critical to clinical diagnosing and treatment as well as for scientific studies. In this study, we sought to automatically and precisely extract intracranial electrodes using pre-operative MRI and post-operative CT images. Method: The subdural and depth intracranial electrodes were readily detected using clustering-based segmentation. Depth electrodes were tracked by fitting a quadratic curve to account for potential bending during the neurosurgery. The identified electrodes can be manipulated using a graphic interface and labeled to cortical areas in individual native space based on anatomical parcellation and displayed in the volume and surface space. Results: The electrodes' localizations were validated with high precision. The electrode coordinates were normalized to a standard space. Moreover, the probabilistic value being to a specific area or a functional network was provided. Conclusions: We developed an integrative toolbox to reconstruct and label the intracranial electrodes implanted in the patients with medically intractable epilepsy. This toolbox provided a convenient way to allow inter-subject comparisons and relation of intracranial EEG findings to the larger body of neuroimaging literature. PMID:28261083

  9. Polar stratospheric optical depth observed between 1978 and 1985

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Trepte, C. R.

    1987-01-01

    Observations of the stratospheric optical depth at 1.0 micron obtained for high latitudes are presented for a 7-year period. Weekly averaged data determined from measurements made by the Stratospheric Aerosol Measurement experiment from October 1978-1985 show that the overall yearly values in both polar regions are controlled by volcanic perturbations, with most volcanic effects being experienced in Arctic latitudes. Conservatively, peak values found in the Antarctic region were approximately 0.02 and in the Arctic region about 0.55. Probable values for these regions are estimated to be 0.26 and 0.11, respectively. The weekly averaged data also show the seasonal fluctuations due to microphysical and dynamical processes. Comparison of the optical depth record with a weekly averaged 50-mbar temperature record indicates that polar stratospheric clouds are present in the southern high latitudes each year near this level from early June to early September. A depression observed in the optical depth record each austral spring season is believed to be the result of the downward displacement of particles caused by subsidence and sedimentation during the course of winter. Following the breakup of the vortex, optical depth values increase as aerosol is transported poleward. These features are noted to be present in the Arctic region as well, but on a smaller scale because of the satellite sampling methodology and the averaging scheme employed.

  10. Polar stratospheric optical depth observed between 1978 and 1985

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Trepte, C. R.

    1987-01-01

    Observations of the stratospheric optical depth at 1.0 micron obtained for high latitudes are presented for a 7-year period. Weekly averaged data determined from measurements made by the Stratospheric Aerosol Measurement experiment from October 1978-1985 show that the overall yearly values in both polar regions are controlled by volcanic perturbations, with most volcanic effects being experienced in Arctic latitudes. Conservatively, peak values found in the Antarctic region were approximately 0.02 and in the Arctic region about 0.55. Probable values for these regions are estimated to be 0.26 and 0.11, respectively. The weekly averaged data also show the seasonal fluctuations due to microphysical and dynamical processes. Comparison of the optical depth record with a weekly averaged 50-mbar temperature record indicates that polar stratospheric clouds are present in the southern high latitudes each year near this level from early June to early September. A depression observed in the optical depth record each austral spring season is believed to be the result of the downward displacement of particles caused by subsidence and sedimentation during the course of winter. Following the breakup of the vortex, optical depth values increase as aerosol is transported poleward. These features are noted to be present in the Arctic region as well, but on a smaller scale because of the satellite sampling methodology and the averaging scheme employed.

  11. A comparison of hydrographically and optically derived mixed layer depths

    USGS Publications Warehouse

    Zawada, D.G.; Zaneveld, J.R.V.; Boss, E.; Gardner, W.D.; Richardson, M.J.; Mishonov, A.V.

    2005-01-01

    Efforts to understand and model the dynamics of the upper ocean would be significantly advanced given the ability to rapidly determine mixed layer depths (MLDs) over large regions. Remote sensing technologies are an ideal choice for achieving this goal. This study addresses the feasibility of estimating MLDs from optical properties. These properties are strongly influenced by suspended particle concentrations, which generally reach a maximum at pycnoclines. The premise therefore is to use a gradient in beam attenuation at 660 nm (c660) as a proxy for the depth of a particle-scattering layer. Using a global data set collected during World Ocean Circulation Experiment cruises from 1988-1997, six algorithms were employed to compute MLDs from either density or temperature profiles. Given the absence of published optically based MLD algorithms, two new methods were developed that use c660 profiles to estimate the MLD. Intercomparison of the six hydrographically based algorithms revealed some significant disparities among the resulting MLD values. Comparisons between the hydrographical and optical approaches indicated a first-order agreement between the MLDs based on the depths of gradient maxima for density and c660. When comparing various hydrographically based algorithms, other investigators reported that inherent fluctuations of the mixed layer depth limit the accuracy of its determination to 20 m. Using this benchmark, we found a ???70% agreement between the best hydrographical-optical algorithm pairings. Copyright 2005 by the American Geophysical Union.

  12. Precision glass molding: an integrative approach for the production of high precision micro-optics

    NASA Astrophysics Data System (ADS)

    Hünten, Martin; Klocke, Fritz; Dambon, Olaf

    2010-02-01

    Miniaturization and integration are the dominating factors for the success of numerous optical devices. Conventional manufacturing processes for the fabrication of precise glass optics by means of grinding and polishing cannot cope the increasing demands in terms of precision, volume and costs. Here, precision glass molding is the enabling technology to meet these demands of the future optical products and applications. Since the market requests further miniaturization and integration of the micro optical components the possession of the entire sequence of processes is absolutely essential. With the accomplished and ongoing developments at the Fraunhofer IPT, the replication of double-sided (a)spherical and (a)cylindrical glass lenses with form accuracies of < 150 nm as well as lens arrays and even freeform optics could be realized. Therefore, a sequence of processes needs to be passed. The FEM-simulation of the molding process which was driven to a point capable to simulate even the molding of freeform optics is the first process step. Further on, new mold design concepts were generated to enable the replication of free formed optics. The research works focusing on the mold manufacturing led to sophisticated grinding process strategies able to realized complex mold geometries such as lens arrays. With regard to the coating of the molds, proceedings were developed assuring a defect free and uniform coating which enables the longevity of the molds and therewith helps reducing the final costs per lens. Thus, the precision glass molding becomes more and more interesting even for highly complex mid volume lots, characteristic for European or US optics manufacturer.

  13. Precision Spectroscopy, Diode Lasers, and Optical Frequency Measurement Technology

    NASA Technical Reports Server (NTRS)

    Hollberg, Leo (Editor); Fox, Richard (Editor); Waltman, Steve (Editor); Robinson, Hugh

    1998-01-01

    This compilation is a selected set of reprints from the Optical Frequency Measurement Group of the Time and Frequency Division of the National Institute of Standards and Technology, and consists of work published between 1987 and 1997. The two main programs represented here are (1) development of tunable diode-laser technology for scientific applications and precision measurements, and (2) research toward the goal of realizing optical-frequency measurements and synthesis. The papers are organized chronologically in five, somewhat arbitrarily chosen categories: Diode Laser Technology, Tunable Laser Systems, Laser Spectroscopy, Optical Synthesis and Extended Wavelength Coverage, and Multi-Photon Interactions and Optical Coherences.

  14. Eddington limit for a gaseous stratus with finite optical depth

    NASA Astrophysics Data System (ADS)

    Fukue, Jun

    2015-06-01

    The Eddington luminosity of a spherical source is usually defined for a uniformly extending normal plasma. We usually suppose that the gas can accrete to the central object at the sub-Eddington luminosity, while it would be blown off from the central luminous source in the super-Eddington case. We reconsider this central dogma of the Eddington limit under the radiative transfer effect for the purely scattering case, using analytical and numerical methods. For the translucent isolated gas cloud (stratus) with finite optical depth, the concept of the Eddington luminosity is drastically changed. In an heuristic way, we find that the critical condition is approximately expressed as Γ = (1 + μ* + τc)/2, where Γ (=L/LE) is the central luminosity L normalized by the Eddington luminosity LE, τc is the optical depth of the stratus, and μ* (=√{1-R_*^2/R^2}) is the direction cosine of the central object, R* being the radius of the central object, and R the distance from the central object. When the optical depth of the stratus is around unity, the classical Eddington limit roughly holds for the stratus; Γ ˜ 1. However, when the optical depth is greater than unity, the critical condition becomes roughly Γ ˜ τc/2, and the stratus would infall on to the central source even at the highly super-Eddington luminosity. When the optical depth is less than unity, on the other hand, the critical condition reduces to Γ ≳ (1 + μ*)/2, and the stratus could be blown off in some limited ranges, depending on μ*. This new concept of the Eddington limit for the isolated stratus could drastically change the accretion and outflow physics of highly inhomegeneous plasmas, with relevance for astrophysical jets and winds and supermassive black hole formation.

  15. Space camera optical axis pointing precision measurement system

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Meng, Fanbo; Yang, Zijun; Guo, Yubo; Ye, Dong

    2016-01-01

    In order to realize the space camera which on satellite optical axis pointing precision measurement, a monocular vision measurement system based on object-image conjugate is established. In this system the algorithms such as object-image conjugate vision models and point by point calibration method are applied and have been verified. First, the space camera axis controller projects a laser beam to the standard screen for simulating the space camera's optical axis. The laser beam form a target point and has been captured by monocular vision camera. Then the two-dimensional coordinates of the target points on the screen are calculated by a new vision measurement model which based on a looking-up and matching table, the table has been generated by object-image conjugate algorithm through point by point calibration. Finally, compare the calculation of coordinates offered by measurement system with the theory of coordinate offered by optical axis controller, the optical axis pointing precision can be evaluated. Experimental results indicate that the absolute precision of measurement system up to 0.15mm in 2m×2m FOV. This measurement system overcome the nonlinear distortion near the edge of the FOV and can meet the requirement of space camera's optical axis high precision measurement and evaluation.

  16. Effects of age and optical blur on real depth stereoacuity.

    PubMed

    Costa, Marcelo F; Moreira, Sonia M C F; Hamer, Russell D; Ventura, Dora F

    2010-09-01

    Stereoscopic depth perception utilizes the disparity cues between the images that fall on the retinae of the two eyes. The purpose of this study was to determine what role aging and optical blur play in stereoscopic disparity sensitivity for real depth stimuli. Forty-six volunteers were tested ranging in age from 15 to 60 years. Crossed and uncrossed disparity thresholds were measured using white light under conditions of best optical correction. The uncrossed disparity thresholds were also measured with optical blur (from +1.0D to +5.0D added to the best correction). Stereothresholds were measured using the Frisby Stereo Test, which utilizes a four-alternative forced-choice staircase procedure. The threshold disparities measured for young adults were frequently lower than 10 arcsec, a value considerably lower than the clinical estimates commonly obtained using Random Dot Stereograms (20 arcsec) or Titmus Fly Test (40 arcsec) tests. Contrary to previous reports, disparity thresholds increased between the ages of 31 and 45 years. This finding should be taken into account in clinical evaluation of visual function of older patients. Optical blur degrades visual acuity and stereoacuity similarly under white-light conditions, indicating that both functions are affected proportionally by optical defocus. © 2010 The Authors, Ophthalmic and Physiological Optics © 2010 The College of Optometrists.

  17. Precision optical angular position marker system for rotating machinery

    NASA Technical Reports Server (NTRS)

    Barranger, J. P.

    1983-01-01

    An optical system is described which generates one or more markers of the angular shaft position of rotating machinery. The system consists of a light source, an optical cable, a machinery mounted lens assembly, a light detector, and a signal conditioner. Light reflected by targets on the rotor is converted to a digital output signal. The system is highly immune to extreme environments of vibration and temperature and achieved a 0.002 percent precision under operational test conditions.

  18. Precision spectral manipulation: A demonstration using a coherent optical memory

    SciTech Connect

    Sparkes, B. M.; Cairns, C.; Hosseini, M.; Higginbottom, D.; Campbell, G. T.; Lam, P. K.; Buchler, B. C.

    2014-12-04

    The ability to coherently spectrally manipulate quantum information has the potential to improve qubit rates across quantum channels and find applications in optical quantum computing. Here we present experiments that use a multi-element solenoid combined with the three-level gradient echo memory scheme to perform precision spectral manipulation of optical pulses. If applied in a quantum information network, these operations would enable frequency-based multiplexing of qubits.

  19. Ship-based Aerosol Optical Depth Measurements Near Antarctica

    NASA Astrophysics Data System (ADS)

    Sakerin, S. M.; Smirnov, A.; Kabanov, D. M.; Turchinovich, Y. S.; Holben, B. N.; Radionov, V. F.; Slutsker, I.

    2006-12-01

    Aerosol optical properties over the oceans were studied in November 2005 January 2006 onboard the R/V Akademik Fedorov within the framework of the 51st Russian Antarctic Expedition. Measurements were made with the handheld sunphotometer Microtops II. The sunphotometer was calibrated against the AERONET reference CIMEL radiometer. The direct sun measurements were acquired in five spectral channels at 340, 440, 675, 870 and 936 nm. Aerosol optical depth was retrieved by applying the AERONET processing algorithm (Version 2). The paper presents results of measurements along the Atlantic transect and in the Antarctic region, where the main data volume was obtained (spanning 20 days). During the measurement period near Antarctica aerosol optical depth was low (daily averages varied within 0.02-0.04 at a wavelength 440 nm). Average spectral dependence of aerosol optical depth showed usual monotonic behavior, decreasing from 0.037 at 440 nm to 0.022 at 870 nm. Daily averaged Angstrom parameter was 0.84. Spatial and temporal variations in the Antarctic region were less or about 0.02 which is comparable with the measurement uncertainty. For a few days Microtops was collocated with the stationary sunphotometer ABAS-3 from the coastal Antarctic station Myrnyi and took simultaneous measurements. Presented results are compared with the long-term observations in Antarctica.

  20. Depth resolution enhancement in double-detection optical scanning holography.

    PubMed

    Ou, Haiyan; Poon, Ting-Chung; Wong, Kenneth K Y; Lam, Edmund Y

    2013-05-01

    We propose an optical scanning holography system with enhanced axial resolution using two detections at different depths. By scanning the object twice, we can obtain two different sets of Fresnel zone plates to sample the same object, which in turn provides more information for the sectional image reconstruction process. We develop the computation algorithm that makes use of such information, solving a constrained optimization problem using the conjugate gradient method. Simulation results show that this method can achieve a depth resolution up to 1 μm.

  1. Design of an optical system with large depth of field using in the micro-assembly

    NASA Astrophysics Data System (ADS)

    Li, Rong; Chang, Jun; Zhang, Zhi-jing; Ye, Xin; Zheng, Hai-jing

    2013-08-01

    Micro system currently is the mainstream of application and demand of the field of micro fabrication of civilian and national defense. Compared with the macro assembly, the requirements on location accuracy of the micro-assembly system are much higher. Usually the dimensions of the components of the micro-assembly are mostly between a few microns to several hundred microns. The general assembly precision requires for the sub-micron level. Micro system assembly is the bottleneck of micro fabrication currently. The optical stereo microscope used in the field of micro assembly technology can achieve high-resolution imaging, but the depth of field of the optical imaging system is too small. Thus it's not conducive to the three-dimensional observation process of the micro-assembly. This paper summarizes the development of micro system assembly at home and abroad firstly. Based on the study of the core features of the technology, a program is proposed which uses wave front coding technology to increase the depth of field of the optical imaging system. In the wave front coding technology, by combining traditional optical design with digital image processing creatively, the depth of field can be greatly increased, moreover, all defocus-related aberrations, such as spherical aberration, chromatic aberration, astigmatism, Ptzvel(field) curvature, distortion, and other defocus induced by the error of assembling and temperature change, can be corrected or minimized. In this paper, based on the study of theory, a set of optical microscopy imaging system is designed. This system is designed and optimized by optical design software CODE V and ZEMAX. At last, the imaging results of the traditional optical stereo microscope and the optical stereo microscope applied wave front coding technology are compared. The results show that: the method has a practical operability and the phase plate obtained by optimized has a good effect on improving the imaging quality and increasing the

  2. Development of an ultrahigh-precision x-ray optics

    NASA Astrophysics Data System (ADS)

    Kitamoto, Shunji; Takano, Haruko; Saitoh, Harue; Yamamoto, Norimasa; Kohmura, Takayoshi; Suga, Kazuharu; Sekiguchi, Hiroyuki; Ohkawa, Yohei; Kanai, Jun'ichi; Chiba, Shigeto

    2003-12-01

    We are developing an ultra high precision Soft X-ray telescope. The design of the telescope is a normal incident one for 13.5 nm band using Mo/Si multilayers. Two ideas are introduced. One is the optical measurement system in order to monitor the precision of the optics system. The other is the adaptive optics system with a deformable mirror. Using an X ray-optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror to compensate the system distortion as a closed loop system. We confirmed that the absolute precision of the wave front sensor was less than 3 nm rms. This is also confirmed that the determination of the image center of each micro lens can be ~1/100 of the pixel size. The precision of the deformable mirror was roughly 5 nm rms. Using the closed loop control the accuracy of the repeatability of the shape of the deformable mirror is less than 2 nm rms. The shape of the primary mirror was an off-axis paraboloide with an effective diameter of 80 mm. This primary mirror was coated by Mo/Si multilayers. The reflectivity of the primary mirror at 13.5 nm was ranging from 30 to 50%. The X ray-optical separation filter was made from Zr with a thickness of ~170 nm. The transmission of the filter for low energy X-ray measured and was roughly 50% at thickness of ~170 nm. The transmission of the filter for low energy X-ray was measured and was roughly 50% at 13.5 nm.

  3. The Navy Precision Optical Interferometer for SSA Applications: An Update

    DTIC Science & Technology

    2014-09-01

    the Navy Precision Optical Interferometer (NPOI) located in Flagstaff AZ and finally the European Southern Observatory Very Large Telescope...bootstrapping approach. Lastly, we also mention that our current program, jointly with our partners at USNO and Lowell Observatory , for the

  4. Strategies for precision adhesive bonding of micro-optical systems

    NASA Astrophysics Data System (ADS)

    Müller, Tobias; Kotnur Venu, Vyshak; Haag, Sebastian; Zontar, Daniel; Sauer, Sebastian; Wenzel, Christian; Brecher, Christian

    2015-02-01

    Today's piezo-based micromanipulator technology allows for highly precise manipulation of optical components. A crucial question for the quality of optical assemblies is the misalignment after curing. The challenge of statistical deviations in the curing process requires a sophisticated knowledge on the relevant process parameters. An approach to meet these requirements is the empirical analysis such as characterization of shrinkage. Gaining sophisticated knowledge about the statistical process of adhesive bonding advances the quality of related production steps like beam-shaping optics, mounting of turning mirrors for fiber coupling or building resonators evaluating power, mode characteristics and beam shape. Maximizing the precision of these single assembly steps fosters the scope of improving the overall efficiency of the entire laser system. At Fraunhofer IPT research activities on the identification of relevant parameters for improved adhesive bonding precision have been undertaken and are ongoing. The influence of the volumetric repeatability of different automatic and manual dispensing methods play an important role. Also, the evaluation of UV-light sources and the relating illumination properties have a significant influence on the bonding result. Furthermore, common UV-curing adhesives are being examined on their performance and reliability for both highest precision prototyping, as well as their application as robust bonding medium in automated optics assembly cells. This paper sums up the parameters of most influence. Overall goal of these activities is the development of a prediction model for optimized shrinkage compensation and thus improved assembly quality.

  5. Contrails of Small and Very Large Optical Depth

    NASA Technical Reports Server (NTRS)

    Atlas, David; Wang, Zhien

    2010-01-01

    This work deals with two kinds of contrails. The first comprises a large number of optically thin contrails near the tropopause. They are mapped geographically using a lidar to obtain their height and a camera to obtain azimuth and elevation. These high-resolution maps provide the local contrail geometry and the amount of optically clear atmosphere. The second kind is a single trail of unprecedentedly large optical thickness that occurs at a lower height. The latter was observed fortuitously when an aircraft moving along the wind direction passed over the lidar, thus providing measurements for more than 3 h and an equivalent distance of 620 km. It was also observed by Geostationary Operational Environmental Satellite (GOES) sensors. The lidar measured an optical depth of 2.3. The corresponding extinction coefficient of 0.023 per kilometer and ice water content of 0.063 grams per cubic meter are close to the maximum values found for midlatitude cirrus. The associated large radar reflectivity compares to that measured by ultrasensitive radar, thus providing support for the reality of the large optical depth.

  6. Variations in stratospheric aerosol optical depth during northern warmings

    NASA Technical Reports Server (NTRS)

    Wang, P.-H.; Mccormick, M. P.

    1985-01-01

    In this paper, the properties of the stratospheric aerosol optical depth (above 50 mbar) have been studied by using aerosol extinction profiles (at 1 micron) derived from the Stratospheric Aerosol Measurement and Stratospheric Aerosol and Gas Experiment (SAGE) during warming periods in the Northern Hemisphere. It is shown that, during the disturbed periods in winter, low values of aerosol optical depth (less than 0.0002) are found within the low-pressure system(s) (at the 30-mbar pressure surface), while high values are found outside. Similar characteristics are found to exist for the simultaneously observed SAGE O3 and NO2 columnar density distributions. Strong longitudinal gradients are shown with the low values within and wherever the vortex exists. This characteristic is maintained during and after the circumpolar vortex is disturbed, even after breakdown, indicating an isolation of the material within the vortex.

  7. Radial widths, optical depths, and eccentricities of the Uranian rings

    NASA Astrophysics Data System (ADS)

    Nicholson, P. D.; Matthews, K.; Goldreich, P.

    1982-02-01

    Observations of the stellar occultation by the Uranian rings of 15/16 August 1980 are used to estimate radial widths and normal optical depths for segments of rings 6, 5, 4, alpha, beta, eta, gamma, and delta. Synthetic occultation profiles are generated to match the observed light curves. A review of published data confirms the existence of width-radius relations for rings alpha and beta, and indicates that the optical depths of these two rings vary inversely with their radial widths. Masses are obtained for rings alpha and beta, on the assumption that differential precession is prevented by their self-gravity. A quantitative comparison of seven epsilon-ring occultation profiles obtained over a period of 3.4 yr reveals a consistent structure, which may reflect the presence of unresolved gaps and subrings.

  8. Signal filtering algorithm for depth-selective diffuse optical topography

    NASA Astrophysics Data System (ADS)

    Fujii, M.; Nakayama, K.

    2009-03-01

    A compact filtered backprojection algorithm that suppresses the undesirable effects of skin circulation for near-infrared diffuse optical topography is proposed. Our approach centers around a depth-selective filtering algorithm that uses an inverse problem technique and extracts target signals from observation data contaminated by noise from a shallow region. The filtering algorithm is reduced to a compact matrix and is therefore easily incorporated into a real-time system. To demonstrate the validity of this method, we developed a demonstration prototype for depth-selective diffuse optical topography and performed both computer simulations and phantom experiments. The results show that the proposed method significantly suppresses the noise from the shallow region with a minimal degradation of the target signal.

  9. Elimination of depth degeneracy in optical frequency-domain imaging through polarization-based optical demodulation

    PubMed Central

    Vakoc, B. J.; Yun, S. H.; Tearney, G. J.; Bouma, B. E.

    2009-01-01

    A novel optical frequency-domain imaging system is demonstrated that employs a passive optical demodulation circuit and a chirped digital acquisition clock derived from a voltage-controlled oscillator. The demodulation circuit allows the separation of signals from positive and negative depths to better than 50 dB, thereby eliminating depth degeneracy and doubling the imaging depth range. Our system design is compatible with dual-balanced and polarization-diverse detection, important techniques in the practical biomedical application of optical frequency-domain imaging. PMID:16480209

  10. Remote Sensing of Atmospheric Optical Depth Using a Smartphone Sun Photometer

    PubMed Central

    Cao, Tingting; Thompson, Jonathan E.

    2014-01-01

    In recent years, smart phones have been explored for making a variety of mobile measurements. Smart phones feature many advanced sensors such as cameras, GPS capability, and accelerometers within a handheld device that is portable, inexpensive, and consistently located with an end user. In this work, a smartphone was used as a sun photometer for the remote sensing of atmospheric optical depth. The top-of-the-atmosphere (TOA) irradiance was estimated through the construction of Langley plots on days when the sky was cloudless and clear. Changes in optical depth were monitored on a different day when clouds intermittently blocked the sun. The device demonstrated a measurement precision of 1.2% relative standard deviation for replicate photograph measurements (38 trials, 134 datum). However, when the accuracy of the method was assessed through using optical filters of known transmittance, a more substantial uncertainty was apparent in the data. Roughly 95% of replicate smart phone measured transmittances are expected to lie within ±11.6% of the true transmittance value. This uncertainty in transmission corresponds to an optical depth of approx. ±0.12–0.13 suggesting the smartphone sun photometer would be useful only in polluted areas that experience significant optical depths. The device can be used as a tool in the classroom to present how aerosols and gases effect atmospheric transmission. If improvements in measurement precision can be achieved, future work may allow monitoring networks to be developed in which citizen scientists submit acquired data from a variety of locations. PMID:24416199

  11. Diurnal variations in optical depth at Mars: Observations and interpretations

    NASA Technical Reports Server (NTRS)

    Colburn, D. S.; Pollack, J. B.; Haberle, R. M.

    1988-01-01

    Viking lander camera images of the Sun were used to compute atmospheric optical depth at two sites over a period of 1 to 1/3 martian years. The complete set of 1044 optical depth determinations is presented in graphical and tabular form. Error estimates are presented in detail. Optical depths in the morning (AM) are generally larger than in the afternoon (PM). The AM-PM differences are ascribed to condensation of water vapor into atmospheric ice aerosols at night and their evaporation in midday. A smoothed time series of these differences shows several seasonal peaks. These are simulated using a one-dimensional radiative convective model which predicts martial atmospheric temperature profiles. A calculation combining these profiles with water vapor measurements from the Mars Atmospheric Water Detector is used to predict when the diurnal variations of water condensation should occur. The model reproduces a majority of the observed peaks and shows the factors influencing the process. Diurnal variation of condensation is shown to peak when the latitude and season combine to warm the atmosphere to the optimum temperature, cool enough to condense vapor at night and warm enough to cause evaporation at midday.

  12. Nighttime Aerosol Optical Depth Variability From Astronomical Photometry

    NASA Astrophysics Data System (ADS)

    Musat, I. C.; Ellingson, R. G.

    2006-12-01

    A technique for determination of the short-term (6 minutes intervals) variability of the aerosol optical depth (AOD) during nighttime from broadband visible measurements of star irradiances during clear nights was developed for the instrument called the Whole Sky Imager (WSI), placed at the Atmospheric Radiation Measurement (ARM) observation site in Oklahoma. The AOD is inferred indirectly from simultaneous observations of extinction of stars having different colors (spectra) and different elevations above the horizon, and takes into account the other sources for starlight attenuation in the atmosphere which might be present and which are measured by other instruments at the site at compatible timescales (e.g., precipitable water vapor content, columnar ozone amount, observed atmospheric stratification). The total error of the new method is a combination of the absolute star flux measurement error with the WSI and a systematic error in the models assumed for the other atmospheric components causing the starlight extinction. The relative error in the aerosol optical depth determined through this method is found to be below 4%. For the validation of the results, the comparison of the aerosol optical depth measured with the Lidar at 10 minutes intervals (at 355nm) with the AOD determined from WSI (in visible) shows a good agreement for the data in the interval studied (1999-2003).

  13. Evaluating UVA aerosol optical depth using a smartphone camera.

    PubMed

    Igoe, Damien P; Parisi, Alfio V; Carter, Brad

    2013-01-01

    This research evaluates a smartphone complementary metal oxide semiconductor (CMOS) image sensor's ability to detect and quantify incident solar UVA radiation and subsequently, aerosol optical depth at 340 and 380 nm. Earlier studies revealed that the consumer grade CMOS sensor has inherent UVA sensitivities, despite attenuating effects of the lens. Narrow bandpass and neutral density filters were used to protect the image sensor and to not allow saturation of the solar images produced. Observations were made on clear days, free from clouds. The results of this research demonstrate that there is a definable response to changing solar irradiance and aerosol optical depth can be measured within 5% and 10% error margins at 380 and 340 nm respectively. The greater relative error occurs at lower wavelengths (340 nm) due to increased atmospheric scattering effects, particularly at higher air masses and due to lower signal to noise ratio in the image sensor. The relative error for solar irradiance was under 1% for observations made at 380 nm. The results indicate that the smartphone image sensor, with additional external narrow bandpass and neutral density filters can be used as a field sensor to evaluate solar UVA irradiance and aerosol optical depth. © 2013 The American Society of Photobiology.

  14. Diurnal variations in optical depth at Mars: Observations and interpretations

    NASA Astrophysics Data System (ADS)

    Colburn, D. S.; Pollack, J. B.; Haberle, R. M.

    1988-05-01

    Viking lander camera images of the Sun were used to compute atmospheric optical depth at two sites over a period of 1 to 1/3 martian years. The complete set of 1044 optical depth determinations is presented in graphical and tabular form. Error estimates are presented in detail. Optical depths in the morning (AM) are generally larger than in the afternoon (PM). The AM-PM differences are ascribed to condensation of water vapor into atmospheric ice aerosols at night and their evaporation in midday. A smoothed time series of these differences shows several seasonal peaks. These are simulated using a one-dimensional radiative convective model which predicts martial atmospheric temperature profiles. A calculation combining these profiles with water vapor measurements from the Mars Atmospheric Water Detector is used to predict when the diurnal variations of water condensation should occur. The model reproduces a majority of the observed peaks and shows the factors influencing the process. Diurnal variation of condensation is shown to peak when the latitude and season combine to warm the atmosphere to the optimum temperature, cool enough to condense vapor at night and warm enough to cause evaporation at midday.

  15. Random Walks and Effective Optical Depth in Relativistic Flow

    NASA Astrophysics Data System (ADS)

    Shibata, Sanshiro; Tominaga, Nozomu; Tanaka, Masaomi

    2014-05-01

    We investigate the random walk process in relativistic flow. In the relativistic flow, photon propagation is concentrated in the direction of the flow velocity due to the relativistic beaming effect. We show that in the pure scattering case, the number of scatterings is proportional to the size parameter ξ ≡ L/l 0 if the flow velocity β ≡ v/c satisfies β/Γ Gt ξ-1, while it is proportional to ξ2 if β/Γ Lt ξ-1, where L and l 0 are the size of the system in the observer frame and the mean free path in the comoving frame, respectively. We also examine the photon propagation in the scattering and absorptive medium. We find that if the optical depth for absorption τa is considerably smaller than the optical depth for scattering τs (τa/τs Lt 1) and the flow velocity satisfies \\beta \\gg \\sqrt{2\\tau _a/\\tau _s}, then the effective optical depth is approximated by τ* ~= τa(1 + β)/β. Furthermore, we perform Monte Carlo simulations of radiative transfer and compare the results with the analytic expression for the number of scatterings. The analytic expression is consistent with the results of the numerical simulations. The expression derived in this study can be used to estimate the photon production site in relativistic phenomena, e.g., gamma-ray burst and active galactic nuclei.

  16. Enhanced optical clearing of skin in vivo and optical coherence tomography in-depth imaging

    NASA Astrophysics Data System (ADS)

    Wen, Xiang; Jacques, Steven L.; Tuchin, Valery V.; Zhu, Dan

    2012-06-01

    The strong optical scattering of skin tissue makes it very difficult for optical coherence tomography (OCT) to achieve deep imaging in skin. Significant optical clearing of in vivo rat skin sites was achieved within 15 min by topical application of an optical clearing agent PEG-400, a chemical enhancer (thiazone or propanediol), and physical massage. Only when all three components were applied together could a 15 min treatment achieve a three fold increase in the OCT reflectance from a 300 μm depth and 31% enhancement in image depth Zthreshold.

  17. Precision molding of advanced glass optics: innovative production technology for lens arrays and free form optics

    NASA Astrophysics Data System (ADS)

    Pongs, Guido; Bresseler, Bernd; Bergs, Thomas; Menke, Gert

    2012-10-01

    Today isothermal precision molding of imaging glass optics has become a widely applied and integrated production technology in the optical industry. Especially in consumer electronics (e.g. digital cameras, mobile phones, Blu-ray) a lot of optical systems contain rotationally symmetrical aspherical lenses produced by precision glass molding. But due to higher demands on complexity and miniaturization of optical elements the established process chain for precision glass molding is not sufficient enough. Wafer based molding processes for glass optics manufacturing become more and more interesting for mobile phone applications. Also cylindrical lens arrays can be used in high power laser systems. The usage of unsymmetrical free-form optics allows an increase of efficiency in optical laser systems. Aixtooling is working on different aspects in the fields of mold manufacturing technologies and molding processes for extremely high complex optical components. In terms of array molding technologies, Aixtooling has developed a manufacturing technology for the ultra-precision machining of carbide molds together with European partners. The development covers the machining of multi lens arrays as well as cylindrical lens arrays. The biggest challenge is the molding of complex free-form optics having no symmetrical axis. A comprehensive CAD/CAM data management along the entire process chain is essential to reach high accuracies on the molded lenses. Within a national funded project Aixtooling is working on a consistent data handling procedure in the process chain for precision molding of free-form optics.

  18. Aspects of ultra-high-precision diamond machining of RSA 443 optical aluminium

    NASA Astrophysics Data System (ADS)

    Mkoko, Z.; Abou-El-Hossein, K.

    2015-08-01

    Optical aluminium alloys such as 6061-T6 are traditionally used in ultra-high precision manufacturing for making optical mirrors for aerospace and other applications. However, the optics industry has recently witnessed the development of more advanced optical aluminium grades that are capable of addressing some of the issues encountered when turning with single-point natural monocrystalline diamond cutters. The advent of rapidly solidified aluminium (RSA) grades has generally opened up new possibilities for ultra-high precision manufacturing of optical components. In this study, experiments were conducted with single-point diamond cutters on rapidly solidified aluminium RSA 443 material. The objective of this study is to observe the effects of depth of cut and feed rate at a fixed rotational speed on the tool wear rate and resulting surface roughness of diamond turned specimens. This is done to gain further understanding of the rate of wear on the diamond cutters versus the surface texture generated on the RSA 443 material. The diamond machining experiments yielded machined surfaces which are less reflective but with consistent surface roughness values. Cutting tools were observed for wear through scanning microscopy; relatively low wear pattern was evident on the diamond tool edge. The highest tool wear were obtained at higher depth of cut and increased feed rate.

  19. High-precision measurement of magnetic penetration depth in superconducting films

    SciTech Connect

    He, X.; Gozar, A.; Sundling, R.; Božović, I.

    2016-11-01

    We report that the magnetic penetration depth (λ) in thin superconducting films is usually measured by the mutual inductance technique. The accuracy of this method has been limited by uncertainties in the geometry of the solenoids and in the film position and thickness, by parasitic coupling between the coils, etc. Here, we present several improvements in the apparatus and the method. To ensure the precise thickness of the superconducting layer, we engineer the films at atomic level using atomic-layer-by-layer molecular beam epitaxy. In this way, we also eliminate secondary-phase precipitates, grain boundaries, and pinholes that are common with other deposition methods and that artificially increase the field transmission and thus the apparent λ. For better reproducibility, the thermal stability of our closed-cycle cryocooler used to control the temperature of the mutual inductance measurement has been significantly improved by inserting a custom-built thermal conductivity damper. Next, to minimize the uncertainties in the geometry, we fused a pair of small yet precisely wound coils into a single sapphire block machined to a high precision. Lastly, the sample is spring-loaded to exactly the same position with respect to the solenoids. Altogether, we can measure the absolute value of λ with the accuracy better than ±1%.

  20. High-precision measurement of magnetic penetration depth in superconducting films

    DOE PAGES

    He, X.; Gozar, A.; Sundling, R.; ...

    2016-11-01

    We report that the magnetic penetration depth (λ) in thin superconducting films is usually measured by the mutual inductance technique. The accuracy of this method has been limited by uncertainties in the geometry of the solenoids and in the film position and thickness, by parasitic coupling between the coils, etc. Here, we present several improvements in the apparatus and the method. To ensure the precise thickness of the superconducting layer, we engineer the films at atomic level using atomic-layer-by-layer molecular beam epitaxy. In this way, we also eliminate secondary-phase precipitates, grain boundaries, and pinholes that are common with other depositionmore » methods and that artificially increase the field transmission and thus the apparent λ. For better reproducibility, the thermal stability of our closed-cycle cryocooler used to control the temperature of the mutual inductance measurement has been significantly improved by inserting a custom-built thermal conductivity damper. Next, to minimize the uncertainties in the geometry, we fused a pair of small yet precisely wound coils into a single sapphire block machined to a high precision. Lastly, the sample is spring-loaded to exactly the same position with respect to the solenoids. Altogether, we can measure the absolute value of λ with the accuracy better than ±1%.« less

  1. High-precision measurement of magnetic penetration depth in superconducting films

    NASA Astrophysics Data System (ADS)

    He, X.; Gozar, A.; Sundling, R.; Božović, I.

    2016-11-01

    The magnetic penetration depth (λ) in thin superconducting films is usually measured by the mutual inductance technique. The accuracy of this method has been limited by uncertainties in the geometry of the solenoids and in the film position and thickness, by parasitic coupling between the coils, etc. Here, we present several improvements in the apparatus and the method. To ensure the precise thickness of the superconducting layer, we engineer the films at atomic level using atomic-layer-by-layer molecular beam epitaxy. In this way, we also eliminate secondary-phase precipitates, grain boundaries, and pinholes that are common with other deposition methods and that artificially increase the field transmission and thus the apparent λ. For better reproducibility, the thermal stability of our closed-cycle cryocooler used to control the temperature of the mutual inductance measurement has been significantly improved by inserting a custom-built thermal conductivity damper. Next, to minimize the uncertainties in the geometry, we fused a pair of small yet precisely wound coils into a single sapphire block machined to a high precision. The sample is spring-loaded to exactly the same position with respect to the solenoids. Altogether, we can measure the absolute value of λ with the accuracy better than ±1%.

  2. Impact of Using Assimilated Data for Evaluating Performance of Active CO2 Optical Depth Measurements

    NASA Astrophysics Data System (ADS)

    Kooi, S. A.; Harrison, F. W.; Lin, B.; Ismail, S.; Browell, E. V.; Yang, M. M.; Choi, Y.

    2015-12-01

    NASA has recently conducted multiple DC-8 flight campaigns of candidate instruments for the future Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. For each campaign, the precision and accuracy of the remote measurements of atmospheric CO2 differential absorption optical depths from the candidate instruments were evaluated with respect to corresponding CO2 optical depths derived from in situ profiles of atmospheric state variables including atmospheric CO2 mixing ratios, temperature (T), pressure (p), and humidity (q) and radiative transfer calculations using the HITRAN spectroscopic database in combination with recent measurements of spectral line parameters. To enable this evaluation, the DC-8 flights were designed to include multiple overpasses of a comparison location where the aircraft performed a spiral ascent or descent and captured the in situ profiles using a suite of onboard instruments. However large segments of some flights took place far from spiral locations and therefore had no coincident in situ measurements of the atmospheric state (CO2, T, p, q). For these situations meterological analysis data from the Goddard Modeling and Assimilation Office (GMAO) GEOS-5 gridded data have been used to assimilate atmospheric state profiles for use in the CO2 optical depth derivation. We use the location of the DC-8 spirals to identify all of the GMAO GEOS-5 gridded profiles that would compare with each spiral and report their differences with respect to the DC-8 in situ profiles. We show how these differences affect the in situ derived CO2 optical depth for the three campaigns and the impacts of these differences on the precision and accuracy evaluations of the remote CO2 measurements.

  3. Impact of Using Assimilated Data for Evaluating Performance of Active CO2 Optical Depth Measurements

    NASA Astrophysics Data System (ADS)

    Kooi, S. A.; Lin, B.; Ismail, S.; Browell, E. V.; Harrison, F. W.; Yang, M. M.; Choi, Y.; Kawa, S. R.

    2014-12-01

    NASA has recently conducted multiple DC-8 flight campaigns of candidate instruments for the future Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. For each campaign, the precision and accuracy of the remote measurements of atmospheric CO2 differential absorption optical depths from the candidate instruments were evaluated with respect to corresponding modeled CO2 optical depths derived from in situ profiles of atmospheric state variables including atmospheric CO2 mixing ratios, temperature (T), pressure (p), and humidity (q) and using the HITRAN spectroscopic database. To enable this evaluation, the DC-8 flights were designed to include multiple overpasses of a comparison location where the aircraft performed a spiral ascent or descent and captured the in situ profiles using a suite of onboard instruments. However large segments of some flights took place far from spiral locations and therefore had no coincident in situ measurements of the atmospheric state (CO2, T, p, q). For these situations meterological analysis data from the Goddard Modeling and Assimilation Office (GMAO) GEOS-5 gridded data have been used to assimilate atmospheric state profiles for use in the CO2 optical depth derivation. We use the location of the DC-8 spirals to identify all of the GMAO GEOS-5 gridded profiles that would compare with each spiral and report their differences with respect to the DC-8 in situ profiles. We show how these differences affect the modeled CO2 optical depth for the three campaigns and the impacts of these differences on the precision and accuracy evaluations of the remote CO2 measurements.

  4. Polarization Lidar for High Precision Water Depth Measurements of Glacial Melt Water

    NASA Astrophysics Data System (ADS)

    Barton-Grimley, R. A.; Thayer, J. P.; Koenig, L.; Moussavi, M. S.; Gisler, A.; Crowley, G.

    2016-12-01

    In the past decade, warming temperatures over the GrIS have significantly increased the surface melt flowing through the supraglacial hydrologic system - melt ponds, lakes, and rivers - all playing a crucial role in the mass loss of land ice. The smaller melt ponds, rivers and streams on the ice sheets, which evacuate more water than is contained in the larger lakes [Smith et al., 2015], are not sufficiently measured to quantify melt. Scientific requirements established by the cryospheric community call for hydrographic lidar measurements with water depth accuracy better than ±10 cm over meter-scale depths during the melt season. Lakes observed in Southwest, Greenland were on average 2-3 meters deep with maxima near 8 m. Stream depths ranged from 0.6 to 3.4 m with a mean depth of 2.0 m [Moussavi et al., 2016, Pope et al., 2016 and Smith et al., 2015]. In response, a 532nm topographic/hydrographic lidar demonstrator implementing a novel measurement scheme has been developed. The lab demonstrator isolates water surface and ice substrate returns using polarization scattering attributes, and fast timing, to range resolve the two surfaces at centimeter precision. Results of the lidar demonstrator on polarization properties of surface water roughness and varied ice substrates expected during measurement of supraglacial streams, rivers, and shallow melt ponds will be presented. Demonstrating the measurement techniques in a number of controlled scenarios, necessary for understanding the subsequent instrument response, provides a baseline for future measurements in flow regimes that include stream cross-sectional area and discharge estimates. Supporting analysis indicates benefits in system scalability, applicability, and adaptability using this lidar technique, and offers the means to accurately quantify the predominantly shallow, melt ponds, sinuous rivers, and streams that are not currently identifiable from satellite imagery.

  5. Large area precision optical coatings by pulse magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Frach, Peter; Gloess, Daniel; Goschurny, Thomas; Drescher, Andy; Hartung, Ullrich; Bartzsch, Hagen; Heisig, Andreas; Grune, Harald; Leischnig, Lothar; Leischnig, Steffen; Bundesmann, Carsten

    2017-05-01

    Pulse magnetron sputtering is very well suited for the deposition of optical coatings. Due to energetic activation during film growth, sputtered films are dense, smooth and show an excellent environmental stability. Films of materials like SiO2, Al2O3, Nb2O5 or Ta2O5 can be produced with very little absorption and scattering losses and are well suited for precision optics. FEP's coating plant PreSensLine, a deposition machine dedicated for the development and deposition of precision optical layer systems will be presented. The coating machine (VON ARDENNE) is equipped with dual magnetron systems (type RM by FEP). Concepts regarding machine design, process technology and process control as well as in situ monitoring are presented to realize the high demands on uniformity, accuracy and reproducibility. Results of gradient and multilayer type precision optical coatings are presented. Application examples are edge filters and special antireflective coatings for the backlight of 3D displays with substrate size up to 300 x 400mm. The machine allows deposition of rugate type gradient layers by rotating a rotary table with substrates between two sources of the dual magnetron system. By combination of the precision drive (by LSA) for the substrate movement and a special pulse parameter variation during the deposition process (available with the pulse unit UBS-C2 of FEP), it is possible to adjust the deposition rate as a function of the substrate position exactly. The aim of a current development is a technology for the uniform coating of 3D-substrates and freeform components as well as laterally graded layers.

  6. Precision holographic optical elements in Bayfol HX photopolymer

    NASA Astrophysics Data System (ADS)

    Bruder, Friedrich-Karl; Bang, Hyungseok; Fäcke, Thomas; Hagen, Rainer; Hönel, Dennis; Orselli, Enrico; Rewitz, Christian; Rölle, Thomas; Vukicevic, Dalibor; Walze, Günther

    2016-03-01

    The versatility of Volume Holographic Optical Elements (vHOE) is high, especially because of their tunable angular and spectral Bragg selectivity. Those unique lightweight, thin and flat optical elements are enabled by the new instant developing photopolymer film Bayfol® HX technology, which allows to mass produce cost effective diffractive optics due to its simplified and robust holographic recording process. From a pure scientific point of view volume holography is well established. In practice though, commercially available optical design software is not adapted to handle the specific characteristics of photopolymer diffractive optical elements and their recording. To achieve high quality vHOE precision optics, the recording setup needs to accommodate several aspects that will be covered in this paper. We report on means how to deal with photopolymer shrinkage and average refractive index changes of the recording media. An important part in diffractive optics design is the compensation of different conditions between the holographic recording setup and in a final product containing the vHOE. Usually substrates might need to be changed (in material, in refractive index) as well the illumination sources are using incoherent light having angular and spectral emission profiles with finite bandwidth. Recently special in- and out-coupling vHOEs are becoming attractive e.g. in near eye displays and in compact lighting devices. We will report on design considerations and adjustments to the recording condition for a specific in-coupling vHOE and demonstrate the effects of pre-compensation on this example.

  7. Optical micro-angiography reveals depth-resolved muscular microcirculation

    NASA Astrophysics Data System (ADS)

    Jia, Yali; Wang, Ruikang K.

    2011-03-01

    Impaired muscular microcirculation in lower extremities is common in many peripheral vascular diseases (PVD), especially the peripheral arterial disease (PAD). There is a need for an imaging method that can be used to noninvasively visualize depth-resolved microcirculation within muscle tissues. Optical microangiography (OMAG) is a recently developed label-free imaging method capable of producing 3D images of dynamic blood perfusion within micro-circulatory tissue beds at an imaging depth up to ~2 mm, with an imaging sensitivity to the blood flow at ~160 μm/s. In this paper, we demonstrate the utility of OMAG in imaging the detailed blood flow distributions, at microcirculatory level resolution, within skeletal muscles in mice. By use of the mouse model of hind-limb ischemia, we show OMAG can assess the perfusion changes caused by ligation. These findings indicate that OMAG is a promising technique to effectively study skeletal muscle-related vascular disease and their pharmacologic therapies.

  8. Measurement of aerosol optical depth and sub-visual cloud detection using the optical depth sensor (ODS)

    NASA Astrophysics Data System (ADS)

    Toledo, D.; Rannou, P.; Pommereau, J.-P.; Sarkissian, A.; Foujols, T.

    2016-02-01

    A small and sophisticated optical depth sensor (ODS) has been designed to work in the atmosphere of Mars. The instrument measures alternatively the diffuse radiation from the sky and the attenuated direct radiation from the Sun on the surface. The principal goals of ODS are to retrieve the daily mean aerosol optical depth (AOD) and to detect very high and optically thin clouds, crucial parameters in understanding the Martian meteorology and climatology. The detection of clouds is undertaken at twilight, allowing the detection and characterization of clouds with opacities below 0.03 (sub-visual clouds). In addition, ODS is capable to retrieve the aerosol optical depth during nighttime from moonlight measurements. Recently, ODS has been selected at the METEO meteorological station on board the ExoMars 2018 Lander. In order to study the performance of ODS under Mars-like conditions as well as to evaluate the retrieval algorithms for terrestrial measurements, ODS was deployed in Ouagadougou (Africa) between November 2004 and October 2005, a Sahelian region characterized by its high dust aerosol load and the frequent occurrence of Saharan dust storms. The daily average AOD values retrieved by ODS were compared with those provided by a CIMEL sunphotometer of the AERONET (Aerosol Robotic NETwork) network localized at the same location. Results represent a good agreement between both ground-based instruments, with a correlation coefficient of 0.77 for the whole data set and 0.94 considering only the cloud-free days. From the whole data set, a total of 71 sub-visual cirrus (SVC) were detected at twilight with opacities as thin as 1.10-3 and with a maximum of occurrence at altitudes between 14 and 20 km. Although further optimizations and comparisons of ODS terrestrial measurements are required, results indicate the potential of these measurements to retrieve the AOD and detect sub-visual clouds.

  9. Measurement of aerosol optical depth and sub-visual cloud detection using the optical depth sensor (ODS)

    NASA Astrophysics Data System (ADS)

    Toledo, D.; Rannou, P.; Pommereau, J.-P.; Sarkissian, A.; Foujols, T.

    2015-09-01

    A small and sophisticated optical depth sensor (ODS) has been designed to work in the atmosphere of Earth and Mars. The instrument measures alternatively the diffuse radiation from the sky and the attenuated direct radiation from the sun on the surface. The principal goals of ODS are to retrieve the daily mean aerosol optical depth (AOD) and to detect very high and optically thin clouds, crucial parameters in understanding the Martian and Earth meteorology and climatology. The detection of clouds is undertaken at twilight, allowing the detection and characterization of clouds with opacities below 0.03 (sub-visual clouds). In addition, ODS is capable to retrieve the aerosol optical depth during night-time from moonlight measurements. In order to study the performance of ODS under Mars-like conditions as well as to evaluate the retrieval algorithms for terrestrial measurements, ODS was deployed in Ouagadougou (Africa) between November 2004 and October 2005, a sahelian region characterized by its high dust aerosol load and the frequent occurrence of Saharan dust storms. The daily average AOD values retrieved by ODS were compared with those provided by a CIMEL Sun-photometer of the AERONET (Aerosol Robotic NETwork) network localized at the same location. Results represent a good agreement between both ground-based instruments, with a correlation coefficient of 0.79 for the whole data set and 0.96 considering only the cloud-free days. From the whole dataset, a total of 71 sub-visual cirrus (SVC) were detected at twilight with opacities as thin as 1.10-3 and with a maximum of occurrence at altitudes between 14 and 20 km. Although further analysis and comparisons are required, results indicate the potential of ODS measurements to detect sub-visual clouds.

  10. Constraints on the Optical Depth of Galaxy Groups and Clusters

    NASA Astrophysics Data System (ADS)

    Flender, Samuel; Nagai, Daisuke; McDonald, Michael

    2017-03-01

    Future data from galaxy redshift surveys, combined with high-resolutions maps of the cosmic microwave background, will enable measurements of the pairwise kinematic Sunyaev–Zel’dovich (kSZ) signal with unprecedented statistical significance. This signal probes the matter-velocity correlation function, scaled by the average optical depth (τ) of the galaxy groups and clusters in the sample, and is thus of fundamental importance for cosmology. However, in order to translate pairwise kSZ measurements into cosmological constraints, external constraints on τ are necessary. In this work, we present a new model for the intracluster medium, which takes into account star formation, feedback, non-thermal pressure, and gas cooling. Our semi-analytic model is computationally efficient and can reproduce results of recent hydrodynamical simulations of galaxy cluster formation. We calibrate the free parameters in the model using recent X-ray measurements of gas density profiles of clusters, and gas masses of groups and clusters. Our observationally calibrated model predicts the average {τ }500 (i.e., the integrated τ within a disk of size R 500) to better than 6% modeling uncertainty (at 95% confidence level). If the remaining uncertainties associated with other astrophysical uncertainties and X-ray selection effects can be better understood, our model for the optical depth should break the degeneracy between optical depth and cluster velocity in the analysis of future pairwise kSZ measurements and improve cosmological constraints with the combination of upcoming galaxy and CMB surveys, including the nature of dark energy, modified gravity, and neutrino mass.

  11. Constraints on the optical depth of galaxy groups and clusters

    DOE PAGES

    Flender, Samuel; Nagai, Daisuke; McDonald, Michael

    2017-03-10

    Here, future data from galaxy redshift surveys, combined with high-resolutions maps of the cosmic microwave background, will enable measurements of the pairwise kinematic Sunyaev–Zel'dovich (kSZ) signal with unprecedented statistical significance. This signal probes the matter-velocity correlation function, scaled by the average optical depth (τ) of the galaxy groups and clusters in the sample, and is thus of fundamental importance for cosmology. However, in order to translate pairwise kSZ measurements into cosmological constraints, external constraints on τ are necessary. In this work, we present a new model for the intracluster medium, which takes into account star formation, feedback, non-thermal pressure, and gas cooling. Our semi-analytic model is computationally efficient and can reproduce results of recent hydrodynamical simulations of galaxy cluster formation. We calibrate the free parameters in the model using recent X-ray measurements of gas density profiles of clusters, and gas masses of groups and clusters. Our observationally calibrated model predicts the averagemore » $${\\tau }_{500}$$ (i.e., the integrated τ within a disk of size R 500) to better than 6% modeling uncertainty (at 95% confidence level). If the remaining uncertainties associated with other astrophysical uncertainties and X-ray selection effects can be better understood, our model for the optical depth should break the degeneracy between optical depth and cluster velocity in the analysis of future pairwise kSZ measurements and improve cosmological constraints with the combination of upcoming galaxy and CMB surveys, including the nature of dark energy, modified gravity, and neutrino mass.« less

  12. RANDOM WALKS AND EFFECTIVE OPTICAL DEPTH IN RELATIVISTIC FLOW

    SciTech Connect

    Shibata, Sanshiro; Tominaga, Nozomu; Tanaka, Masaomi

    2014-05-20

    We investigate the random walk process in relativistic flow. In the relativistic flow, photon propagation is concentrated in the direction of the flow velocity due to the relativistic beaming effect. We show that in the pure scattering case, the number of scatterings is proportional to the size parameter ξ ≡ L/l {sub 0} if the flow velocity β ≡ v/c satisfies β/Γ >> ξ{sup –1}, while it is proportional to ξ{sup 2} if β/Γ << ξ{sup –1}, where L and l {sub 0} are the size of the system in the observer frame and the mean free path in the comoving frame, respectively. We also examine the photon propagation in the scattering and absorptive medium. We find that if the optical depth for absorption τ{sub a} is considerably smaller than the optical depth for scattering τ{sub s} (τ{sub a}/τ{sub s} << 1) and the flow velocity satisfies β≫√(2τ{sub a}/τ{sub s}), then the effective optical depth is approximated by τ{sub *} ≅ τ{sub a}(1 + β)/β. Furthermore, we perform Monte Carlo simulations of radiative transfer and compare the results with the analytic expression for the number of scatterings. The analytic expression is consistent with the results of the numerical simulations. The expression derived in this study can be used to estimate the photon production site in relativistic phenomena, e.g., gamma-ray burst and active galactic nuclei.

  13. Strategies for Improved CALIPSO Aerosol Optical Depth Estimates

    NASA Technical Reports Server (NTRS)

    Vaughan, Mark A.; Kuehn, Ralph E.; Tackett, Jason L.; Rogers, Raymond R.; Liu, Zhaoyan; Omar, A.; Getzewich, Brian J.; Powell, Kathleen A.; Hu, Yongxiang; Young, Stuart A.; Avery, Melody A.; Winker, David M.; Trepte, Charles R.

    2010-01-01

    In the spring of 2010, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) project will be releasing version 3 of its level 2 data products. In this paper we describe several changes to the algorithms and code that yield substantial improvements in CALIPSO's retrieval of aerosol optical depths (AOD). Among these are a retooled cloud-clearing procedure and a new approach to determining the base altitudes of aerosol layers in the planetary boundary layer (PBL). The results derived from these modifications are illustrated using case studies prepared using a late beta version of the level 2 version 3 processing code.

  14. Depth resolved detection of lipid using spectroscopic optical coherence tomography

    PubMed Central

    Fleming, Christine P.; Eckert, Jocelyn; Halpern, Elkan F.; Gardecki, Joseph A.; Tearney, Guillermo J.

    2013-01-01

    Optical frequency domain imaging (OFDI) can identify key components related to plaque vulnerability but can suffer from artifacts that could prevent accurate identification of lipid rich regions. In this paper, we present a model of depth resolved spectral analysis of OFDI data for improved detection of lipid. A quadratic Discriminant analysis model was developed based on phantom compositions known chemical mixtures and applied to a tissue phantom of a lipid-rich plaque. We demonstrate that a combined spectral and attenuation model can be used to predict the presence of lipid in OFDI images. PMID:24009991

  15. The Navy Precision Optical Interferometer for SSA: A Progress Report

    NASA Astrophysics Data System (ADS)

    Restaino, S.; Andrews, J. R.; Armstrong, J. T.; Baines, E. K.; Clark, J. H.; Schmitt, H. R.

    2014-09-01

    The Navy Precision Optical Interferometer (NPOI) has been involved in studying how a long-baseline optical interferometer can be used to deliver high angular resolution imagery of geostationary satellites and other deep space man-made objects. We have previously reported on the first ever measurements of a geosatellite glint with an optical interferometer. In this paper we report the progress that has been made in the past year. We have commissioned more imaging stations, both for longer baselines to obtain increased resolution, and for shorter baselines for measuring the lower spatial frequencies. We have also implemented beam combiner improvements that will enable multiple-baseline bootstrapping. This technique is essential for integrating the signal on the longest baselines where the fringe visibilities, especially for man-made objects, are so low that direct fringe tracking is impossible.

  16. The precision of binocular and monocular depth judgments in natural settings.

    PubMed

    McKee, Suzanne P; Taylor, Douglas G

    2010-08-01

    We measured binocular and monocular depth thresholds for objects presented in a real environment. Observers judged the depth separating a pair of metal rods presented either in relative isolation, or surrounded by other objects, including a textured surface. In the isolated setting, binocular thresholds were greatly superior to the monocular thresholds by as much as a factor of 18. The presence of adjacent objects and textures improved the monocular thresholds somewhat, but the superiority of binocular viewing remained substantial (roughly a factor of 10). To determine whether motion parallax would improve monocular sensitivity for the textured setting, we asked observers to move their heads laterally, so that the viewing eye was displaced by 8-10 cm; this motion produced little improvement in the monocular thresholds. We also compared disparity thresholds measured with the real rods to thresholds measured with virtual images in a standard mirror stereoscope. Surprisingly, for the two naive observers, the stereoscope thresholds were far worse than the thresholds for the real rods-a finding that indicates that stereoscope measurements for unpracticed observers should be treated with caution. With practice, the stereoscope thresholds for one observer improved to almost the precision of the thresholds for the real rods.

  17. The precision of binocular and monocular depth judgments in natural settings

    PubMed Central

    McKee, Suzanne P.; Taylor, Douglas G.

    2010-01-01

    We measured binocular and monocular depth thresholds for objects presented in a real environment. Observers judged the depth separating a pair of metal rods presented either in relative isolation, or surrounded by other objects, including a textured surface. In the isolated setting, binocular thresholds were greatly superior to the monocular thresholds by as much as a factor of 18. The presence of adjacent objects and textures improved the monocular thresholds somewhat, but the superiority of binocular viewing remained substantial (roughly a factor of 10). To determine whether motion parallax would improve monocular sensitivity for the textured setting, we asked observers to move their heads laterally, so that the viewing eye was displaced by 8–10 cm; this motion produced little improvement in the monocular thresholds. We also compared disparity thresholds measured with the real rods to thresholds measured with virtual images in a standard mirror stereoscope. Surprisingly, for the two naive observers, the stereoscope thresholds were far worse than the thresholds for the real rods—a finding that indicates that stereoscope measurements for unpracticed observers should be treated with caution. With practice, the stereoscope thresholds for one observer improved to almost the precision of the thresholds for the real rods. PMID:20884470

  18. Seasonal variability of aerosol optical depth over Indian subcontinent

    USGS Publications Warehouse

    Prasad, A.K.; Singh, R.P.; Singh, A.; Kafatos, M.

    2005-01-01

    Ganga basin extends 2000 km E-W and about 400 km N-S and is bounded by Himalayas in the north. This basin is unequivocally found to be affected by high aerosols optical depth (AOD) (>0.6) throughout the year. Himalayas restricts movement of aerosols toward north and as a result dynamic nature of aerosol is seen over the Ganga basin. High AOD in this region has detrimental effects on health of more than 460 million people living in this part of India besides adversely affecting clouds formation, monsoonal rainfall pattern and Normalized Difference Vegetation Index (NDVI). Severe drought events (year 2002) in Ganga basin and unexpected failure of monsoon several times, occurred in different parts of Indian subcontinent. Significant rise in AOD (18.7%) over the central part of basin (Kanpur region) have been found to cause substantial decrease in NDVI (8.1%) since 2000. A negative relationship is observed between AOD and NDVI, magnitude of which differs from region to region. Efforts have been made to determine general distribution of AOD and its dominant departure in recent years spatially using Moderate Resolution Imaging Spectroradiometer (MODIS) data. The seasonal changes in aerosol optical depth over the Indo-Gangetic basin is found to very significant as a result of the increasing dust storm events in recent years. ?? 2005 IEEE.

  19. All-optical relative intensity noise suppression method for the high precision fiber optic gyroscope

    NASA Astrophysics Data System (ADS)

    Zheng, Yue; Zhang, Chunxi; Li, Lijing; Song, Lailiang; Zhang, Yuhui

    2016-10-01

    The relative intensity noise (RIN) is a main factor that limits the detection accuracy of the high precision fiber optic gyroscope (FOG). The RIN spectrum is determined by the normalized autocorrelation of the optical spectrum of the broadband source and is intrinsically different from other fundamental noises. In this paper, we propose an all-optical technique to suppress the RIN. With the power addition of the optical waves from the signal optical path and the reference optical path, the RIN is effectively eliminated at the eigen frequency of the FOG, which is also the demodulation window for the rotation rate signal. Compared with the traditional optical configuration of the FOG, there is only one additional optical component. Experimental results show that, with this method, we can achieve a nearly 3-fold improvement in the angular random walk coefficient. The improved optical configuration for RIN suppression is simple to realize and suitable for engineering application.

  20. Smartphone-Based Android app for Determining UVA Aerosol Optical Depth and Direct Solar Irradiances.

    PubMed

    Igoe, Damien P; Parisi, Alfio; Carter, Brad

    2014-01-01

    This research describes the development and evaluation of the accuracy and precision of an Android app specifically designed, written and installed on a smartphone for detecting and quantifying incident solar UVA radiation and subsequently, aerosol optical depth at 340 and 380 nm. Earlier studies demonstrated that a smartphone image sensor can detect UVA radiation and the responsivity can be calibrated to measured direct solar irradiance. This current research provides the data collection, calibration, processing, calculations and display all on a smartphone. A very strong coefficient of determination of 0.98 was achieved when the digital response was recalibrated and compared to the Microtops sun photometer direct UVA irradiance observations. The mean percentage discrepancy for derived direct solar irradiance was only 4% and 6% for observations at 380 and 340 nm, respectively, lessening with decreasing solar zenith angle. An 8% mean percent difference discrepancy was observed when comparing aerosol optical depth, also decreasing as solar zenith angle decreases. The results indicate that a specifically designed Android app linking and using a smartphone image sensor, calendar and clock, with additional external narrow bandpass and neutral density filters can be used as a field sensor to evaluate both direct solar UVA irradiance and low aerosol optical depths for areas with low aerosol loads. © 2013 The American Society of Photobiology.

  1. Precision glass molding of high-resolution diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans P.; Plöger, Sven; Hermerschmidt, Andreas

    2016-04-01

    The demand of high resolution diffractive optical elements (DOE) is growing. Smaller critical dimensions allow higher deflection angles and can fulfill more demanding requirements, which can only be met by using electron-beam lithography. Replication techniques are more economical, since the high cost of the master can be distributed among a larger number of replicas. The lack of a suitable mold material for precision glass molding has so far prevented an industrial use. Glassy Carbon (GC) offers a high mechanical strength and high thermal strength. No anti-adhesion coatings are required in molding processes. This is clearly an advantage for high resolution, high aspect ratio microstructures, where a coating with a thickness between 10 nm and 200 nm would cause a noticeable rounding of the features. Electron-beam lithography was used to fabricate GC molds with highest precision and feature sizes from 250 nm to 2 μm. The master stamps were used for precision glass molding of a low Tg glass L-BAL42 from OHARA. The profile of the replicated glass is compared to the mold with the help of SEM images. This allows discussion of the max. aspect-ratio and min. feature size. To characterize optical performances, beamsplitting elements are fabricated and their characteristics were investigated, which are in excellent agreement to theory.

  2. Integrating an optical tool inspection system to a precision lathe

    NASA Astrophysics Data System (ADS)

    Barkman, W. E.; Babelay, E. F., Jr.; Williams, R. R.

    1992-03-01

    Optical inspection systems are readily available for the bench-top inspection of a variety of subjects including cutting tools. However, the integration of optical tool inspection techniques into precision machining operations requires the consideration of several factors. Some of the questions that must be answered include: What kinds of tools will be used? What tool characteristics are important to measure? How are these characteristics expressed in a meaningful form that will enhance the quality of the manufacturing process? What will be done with the tool inspection data? Will the inspection be performed on-line, in real-time, to what resolution and accuracy, etc.? This paper describes the integration of an on-machine optical tool inspection/compensation system (OTICS) to a precision turning machine at the Oak Ridge Y-12 Plant. OTICS is an IBM personal computer (PC) based system that uses a vision interface board to collect cutting tool form data. This information is used by the PC to prepare a compensated part program that avoids the workpiece errors that are associated with imperfect cutting tools. Machining tests have demonstrated the system's ability to produce workpiece contour accuracies of 0.0002 in. when using cutting tools with errors as large as 0.0046 in.

  3. Combining confocal microscopy with precise force-scope optical tweezers

    NASA Astrophysics Data System (ADS)

    Richardson, Andrew C.; Reihani, Nader; Oddershede, Lene B.

    2006-08-01

    We demonstrate an example of 'confocal-tweezers' wherein confocal images and precise optical force measurements, using photodiodes, are obtained simultaneously in the x-y plane without moving the objective lens. The optical trap is produced using a 1.064μm cw laser and is combined with Leica's TCS SP5 broadband confocal microscope to trap and image living cells. The unique method by which the confocal images are created facilitates the acquisition of images in areas far from the trapping location. In addition, because the scanning process involves moving galvanic mirrors independently of the objective, the trap is held stable in position and is not subject to any error in position for the x-y scan. We have successfully trapped and confocally imaged 80nm gold colloids, 150nm gold colloids and 1μm polystyrene beads whilst making quantitative measurements of the force applied by the trap on each bead. To the best of our knowledge this is the first time that anyone has combined precise force measuring optical tweezers with confocal microscopy. We also discuss some of the technical challenges involved in advancing the experimental set up to make quantitative force measurements in combination with 3D stacking. Having proven the potential of this system in 2D, we hope to develop it further to investigate the nano-mechanics of cell division through the attachment of gold beads to fluorescently labelled organelles in S. pombe yeast cells.

  4. All-fiber bidirectional optical parametric oscillator for precision sensing.

    PubMed

    Gowda, R; Nguyen, N; Diels, J-C; Norwood, R A; Peyghambarian, N; Kieu, K

    2015-05-01

    We present the design and operation of an all-fiber, synchronously pumped, bidirectional optical parametric oscillator (OPO) for precision sensing applications. The fiber-based OPO (FOPO) generates two frequency combs with identical repetition rates but different carrier offset frequencies. A narrow beatnote was observed with full-width at half-maximum (FWHM) linewidth of <10  Hz when the two frequency combs were overlapped on a photodetector. The all-fiber design removes the need for free-space alignment and adjustment. In addition, an external delay line to overlap the two pulse trains in time on the detector is not needed since our unique design provides automatic delay compensation. We expect the novel FOPO to find important applications in precision measurements including rotation sensing with ultra-large sensing area and sensitivity.

  5. Navy precision optical interferometer measurements of 10 stellar oscillators

    SciTech Connect

    Baines, Ellyn K.; Armstrong, J. Thomas; Schmitt, Henrique R.; Benson, James A.; Zavala, R. T.; Van Belle, Gerard T.

    2014-02-01

    Using the Navy Precision Optical Interferometer, we measured the angular diameters of 10 stars that have previously measured solar-like oscillations. Our sample covered a range of evolutionary stages but focused on evolved subgiant and giant stars. We combined our angular diameters with Hipparcos parallaxes to determine the stars' physical radii, and used photometry from the literature to calculate their bolometric fluxes, luminosities, and effective temperatures. We then used our results to test the scaling relations used by asteroseismology groups to calculate radii and found good agreement between the radii measured here and the radii predicted by stellar oscillation studies. The precision of the relations is not as well constrained for giant stars as it is for less evolved stars.

  6. Derivation of Aerosol Columnar Mass from MODIS Optical Depth

    NASA Technical Reports Server (NTRS)

    Gasso, Santiago; Hegg, Dean A.

    2003-01-01

    In order to verify performance, aerosol transport models (ATM) compare aerosol columnar mass (ACM) with those derived from satellite measurements. The comparison is inherently indirect since satellites derive optical depths and they use a proportionality constant to derive the ACM. Analogously, ATMs output a four dimensional ACM distribution and the optical depth is linearly derived. In both cases, the proportionality constant requires a direct intervention of the user by prescribing the aerosol composition and size distribution. This study introduces a method that minimizes the direct user intervention by making use of the new aerosol products of MODIS. A parameterization is introduced for the derivation of columnar aerosol mass (AMC) and CCN concentration (CCNC) and comparisons between sunphotometer, MODIS Airborne Simulator (MAS) and in-measurements are shown. The method still relies on the scaling between AMC and optical depth but the proportionality constant is dependent on the MODIS derived r$_{eff}$,\\eta (contribution of the accumulation mode radiance to the total radiance), ambient RH and an assumed constant aerosol composition. The CCNC is derived fkom a recent parameterization of CCNC as a function of the retrieved aerosol volume. By comparing with in-situ data (ACE-2 and TARFOX campaigns), it is shown that retrievals in dry ambient conditions (dust) are improved when using a proportionality constant dependent on r$ {eff}$ and \\eta derived in the same pixel. In high humidity environments, the improvement inthe new method is inconclusive because of the difficulty in accounting for the uneven vertical distribution of relative humidity. Additionally, two detailed comparisons of AMC and CCNC retrieved by the MAS algorithm and the new method are shown. The new method and MAS retrievals of AMC are within the same order of magnitude with respect to the in-situ measurements of aerosol mass. However, the proposed method is closer to the in-situ measurements than

  7. Astrophysical Adaptation of Points, the Precision Optical Interferometer in Space

    NASA Technical Reports Server (NTRS)

    Reasenberg, Robert D.; Babcock, Robert W.; Murison, Marc A.; Noecker, M. Charles; Phillips, James D.; Schumaker, Bonny L.; Ulvestad, James S.; McKinley, William; Zielinski, Robert J.; Lillie, Charles F.

    1996-01-01

    POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometric measurements from space, yielding submicroarcsecond astrometric results from the mission. It comprises a pair of independent Michelson stellar interferometers and a laser metrology system that measures both the critical starlight paths and the angle between the baselines. The instrument has two baselines of 2 m, each with two subapertures of 35 cm; by articulating the angle between the baselines, it observes targets separated by 87 to 93 deg. POINTS does global astrometry, i.e., it measures widely separated targets, which yields closure calibration, numerous bright reference stars, and absolute parallax. Simplicity, stability, and the mitigation of systematic error are the central design themes. The instrument has only three moving-part mechanisms, and only one of these must move with sub-milliradian precision; the other two can tolerate a precision of several tenths of a degree. Optical surfaces preceding the beamsplitter or its fold flat are interferometrically critical; on each side of the interferometer, there are only three such. Thus, light loss and wavefront distortion are minimized. POINTS represents a minimalistic design developed ab initio for space. Since it is intended for astrometry, and therefore does not require the u-v-plane coverage of an imaging, instrument, each interferometer need have only two subapertures. The design relies on articulation of the angle between the interferometers and body pointing to select targets; the observations are restricted to the 'instrument plane.' That plane, which is fixed in the pointed instrument, is defined by the sensitive direction for the two interferometers. Thus, there is no need for siderostats and moving delay lines, which would have added many precision mechanisms with rolling and sliding parts that would be required to function throughout the mission. Further, there is no need for a third interferometer

  8. Precision optical pointing and tracking from spacecraft with vibrational noise

    NASA Technical Reports Server (NTRS)

    Held, K. J.; Barry, J. D.

    1986-01-01

    The results of an investigation of the performance of three basic precision pointing and tracking control subsystems considered for application to satellite to satellite optical communication missions are discussed. The three-control subsystems include: (1) gyro-stabilized, (2) mass-stabilized and (3) complementary filter. The sources of error included in the analysis included: (1) sensor noise from the optical detector, (2) host satellite baseframe vibrational noise and (3) frictional and bearing noise. The measured vibrational and disturbance data from the LANDSAT satellite was used to generate the power spectral density parameter needed to model the baseframe noise environments of the two satellites used for the evaluation. The results of the study indicate that the 1 microradian rms pointing and tracking accuracy may be achieved with either the gyro-stabilized or the complementary filter approach.

  9. Highly precise and robust packaging of optical components

    NASA Astrophysics Data System (ADS)

    Leers, Michael; Winzen, Matthias; Liermann, Erik; Faidel, Heinrich; Westphalen, Thomas; Miesner, Jörn; Luttmann, Jörg; Hoffmann, Dieter

    2012-03-01

    In this paper we present the development of a compact, thermo-optically stable and vibration and mechanical shock resistant mounting technique by soldering of optical components. Based on this technique a new generation of laser sources for aerospace applications is designed. In these laser systems solder technique replaces the glued and bolted connections between optical component, mount and base plate. Alignment precision in the arc second range and realization of long term stability of every single part in the laser system is the main challenge. At the Fraunhofer Institute for Laser Technology ILT a soldering and mounting technique has been developed for high precision packaging. The specified environmental boundary conditions (e.g. a temperature range of -40 °C to +50 °C) and the required degrees of freedom for the alignment of the components have been taken into account for this technique. In general the advantage of soldering compared to gluing is that there is no outgassing. In addition no flux is needed in our special process. The joining process allows multiple alignments by remelting the solder. The alignment is done in the liquid phase of the solder by a 6 axis manipulator with a step width in the nm range and a tilt in the arc second range. In a next step the optical components have to pass the environmental tests. The total misalignment of the component to its adapter after the thermal cycle tests is less than 10 arc seconds. The mechanical stability tests regarding shear, vibration and shock behavior are well within the requirements.

  10. Parameterization of cirrus optical depth and cloud fraction

    SciTech Connect

    Soden, B.

    1995-09-01

    This research illustrates the utility of combining satellite observations and operational analysis for the evaluation of parameterizations. A parameterization based on ice water path (IWP) captures the observed spatial patterns of tropical cirrus optical depth. The strong temperature dependence of cirrus ice water path in both the observations and the parameterization is probably responsible for the good correlation where it exists. Poorer agreement is found in Southern Hemisphere mid-latitudes where the temperature dependence breaks down. Uncertainties in effective radius limit quantitative validation of the parameterization (and its inclusion into GCMs). Also, it is found that monthly mean cloud cover can be predicted within an RMS error of 10% using ECMWF relative humidity corrected by TOVS Upper Troposphere Humidity. 1 ref., 2 figs.

  11. Aerosol Optical Depth: A study using Thailand based Brewer Spectrophotometers

    NASA Astrophysics Data System (ADS)

    Kumharn, Wilawan; Sudhibrabha, Sumridh; Hanprasert, Kesrin

    2015-12-01

    The Aerosol Optical Depth (AOD) was retrieved from the direct-sun Brewer observation by the application of the Beer's law for the years 1997-2011 at two monitoring sites in Thailand (Bangkok and Songkhla). AOD values measured in Bangkok exhibited higher values than Songkhla. In addition, AOD values were higher in the morning and evening in Bangkok. In contrast, the AOD values in Songkhla were slightly lower during the mornings and late afternoons. The variation of AOD was seasonal in Bangkok, with the higher values found in summer (from Mid-February to Mid-May) compared with rainy season (Mid-May to Mid-October), whilst there was no clear seasonal pattern of AOD in Songkhla.

  12. Single atom visibility in STEM optical depth sectioning

    DOE PAGES

    Ishikawa, Ryo; Pennycook, Stephen J.; Lupini, Andrew R.; ...

    2016-10-19

    The continuing development of aberration correctors for the scanning transmission electron microscope (STEM) offers the possibility of locating single atoms in crystals in 3D via optical depth sectioning. The main factors that determine the feasibility of such an approach are visibility and dose requirements. In this paper, we show how Poisson's statistics can be quantitatively incorporated into STEM image simulations and demonstrate that the 3D location of single cerium atoms in wurtzite-type aluminum nitride is indeed feasible under large-angle illumination conditions with a relatively low dose. We also show that chromatic aberration does not presently represent a limitation provided amore » cold field emission source is used. Finally, these results suggest efforts into improved aberration corrector designs for larger illumination angles that offer significant potential for 3D structure determination of materials.« less

  13. Single atom visibility in STEM optical depth sectioning

    SciTech Connect

    Ishikawa, Ryo; Pennycook, Stephen J.; Lupini, Andrew R.; Findlay, Scott D.; Shibata, Naoya; Ikuhara, Yuichi

    2016-10-19

    The continuing development of aberration correctors for the scanning transmission electron microscope (STEM) offers the possibility of locating single atoms in crystals in 3D via optical depth sectioning. The main factors that determine the feasibility of such an approach are visibility and dose requirements. In this paper, we show how Poisson's statistics can be quantitatively incorporated into STEM image simulations and demonstrate that the 3D location of single cerium atoms in wurtzite-type aluminum nitride is indeed feasible under large-angle illumination conditions with a relatively low dose. We also show that chromatic aberration does not presently represent a limitation provided a cold field emission source is used. Finally, these results suggest efforts into improved aberration corrector designs for larger illumination angles that offer significant potential for 3D structure determination of materials.

  14. Neutron diffraction optics of films with noncollinear magnetic depth structures

    NASA Astrophysics Data System (ADS)

    Korneev, Daniel A.; Chernenko, L. P.

    1992-11-01

    A model of a thin film with depth inhomogeneous or noncollinear magnetization is used to describe its neutron-optical, diffraction, and polarization properties. A quantum mechanical method of calculation is developed based on a numerical solution of the Pauli equation for a neutron in inhomogeneous matter with boundary conditions. This solution permits the uniform calculation of intensities and the polarization vector of the scattered beam over a wide range of conditions from specular reflection to neutron diffraction. The method is applied to certain model structures. Examples of its application to model structures (ferromagnetic spirals, long- period soliton) are given and the calculation can be programmed for a personal computer, taking a few seconds for each value of the incident neutron wave vector.

  15. Single atom visibility in STEM optical depth sectioning

    NASA Astrophysics Data System (ADS)

    Ishikawa, Ryo; Pennycook, Stephen J.; Lupini, Andrew R.; Findlay, Scott D.; Shibata, Naoya; Ikuhara, Yuichi

    2016-10-01

    The continuing development of aberration correctors for the scanning transmission electron microscope (STEM) offers the possibility of locating single atoms in crystals in 3D via optical depth sectioning. The main factors that determine the feasibility of such an approach are visibility and dose requirements. Here, we show how Poisson's statistics can be quantitatively incorporated into STEM image simulations and demonstrate that the 3D location of single cerium atoms in wurtzite-type aluminum nitride is indeed feasible under large-angle illumination conditions with a relatively low dose. We also show that chromatic aberration does not presently represent a limitation provided a cold field emission source is used. These results suggest efforts into improved aberration corrector designs for larger illumination angles that offer significant potential for 3D structure determination of materials.

  16. Precision glass molding: Toward an optimal fabrication of optical lenses

    NASA Astrophysics Data System (ADS)

    Zhang, Liangchi; Liu, Weidong

    2017-03-01

    It is costly and time consuming to use machining processes, such as grinding, polishing and lapping, to produce optical glass lenses with complex features. Precision glass molding (PGM) has thus been developed to realize an efficient manufacture of such optical components in a single step. However, PGM faces various technical challenges. For example, a PGM process must be carried out within the super-cooled region of optical glass above its glass transition temperature, in which the material has an unstable non-equilibrium structure. Within a narrow window of allowable temperature variation, the glass viscosity can change from 105 to 1012 Pas due to the kinetic fragility of the super-cooled liquid. This makes a PGM process sensitive to its molding temperature. In addition, because of the structural relaxation in this temperature window, the atomic structure that governs the material properties is strongly dependent on time and thermal history. Such complexity often leads to residual stresses and shape distortion in a lens molded, causing unexpected changes in density and refractive index. This review will discuss some of the central issues in PGM processes and provide a method based on a manufacturing chain consideration from mold material selection, property and deformation characterization of optical glass to process optimization. The realization of such optimization is a necessary step for the Industry 4.0 of PGM.

  17. Precision glass molding: Toward an optimal fabrication of optical lenses

    NASA Astrophysics Data System (ADS)

    Zhang, Liangchi; Liu, Weidong

    2016-12-01

    It is costly and time consuming to use machining processes, such as grinding, polishing and lapping, to produce optical glass lenses with complex features. Precision glass molding (PGM) has thus been developed to realize an efficient manufacture of such optical components in a single step. However, PGM faces various technical challenges. For example, a PGM process must be carried out within the super-cooled region of optical glass above its glass transition temperature, in which the material has an unstable non-equilibrium structure. Within a narrow window of allowable temperature variation, the glass viscosity can change from 105 to 1012 Pas due to the kinetic fragility of the super-cooled liquid. This makes a PGM process sensitive to its molding temperature. In addition, because of the structural relaxation in this temperature window, the atomic structure that governs the material properties is strongly dependent on time and thermal history. Such complexity often leads to residual stresses and shape distortion in a lens molded, causing unexpected changes in density and refractive index. This review will discuss some of the central issues in PGM processes and provide a method based on a manufacturing chain consideration from mold material selection, property and deformation characterization of optical glass to process optimization. The realization of such optimization is a necessary step for the Industry 4.0 of PGM.

  18. Effect of probe geometry and optical properties on the sampling depth for diffuse reflectance spectroscopy.

    PubMed

    Hennessy, Ricky; Goth, Will; Sharma, Manu; Markey, Mia K; Tunnell, James W

    2014-01-01

    The sampling depth of light for diffuse reflectance spectroscopy is analyzed both experimentally and computationally. A Monte Carlo (MC) model was used to investigate the effect of optical properties and probe geometry on sampling depth. MC model estimates of sampling depth show an excellent agreement with experimental measurements over a wide range of optical properties and probe geometries. The MC data are used to define a mathematical expression for sampling depth that is expressed in terms of optical properties and probe geometry parameters.

  19. Precise Stabilization of the Optical Frequency of WGMRs

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Matsko, Andrey; Matsko, Andrey; Yu, Nan; Maleki, Lute; Iltchenko, Vladimir

    2009-01-01

    Crystalline whispering gallery mode resonators (CWGMRs) made of crystals with axial symmetry have ordinary and extraordinary families of optical modes. These modes have substantially different thermo-refractive constants. This results in a very sharp dependence of differential detuning of optical frequency on effective temperature. This frequency difference compared with clock gives an error signal for precise compensation of the random fluctuations of optical frequency. Certain crystals, like MgF2, have turnover points where the thermo-refractive effect is completely nullified. An advantage for applications using WGMRs for frequency stabilization is in the possibility of manufacturing resonators out of practically any optically transparent crystal. It is known that there are crystals with negative and zero thermal expansion at some specific temperatures. Doping changes properties of the crystals and it is possible to create an optically transparent crystal with zero thermal expansion at room temperature. With this innovation s stabilization technique, the resultant WGMR will have absolute frequency stability The expansion of the resonator s body can be completely compensated for by nonlinear elements. This results in compensation of linear thermal expansion (see figure). In three-mode, the MgF2 resonator, if tuned at the turnover thermal point, can compensate for all types of random thermal-related frequency drift. Simplified dual-mode method is also available. This creates miniature optical resonators with good short- and long-term stability for passive secondary frequency ethalon and an active resonator for active secondary frequency standard (a narrowband laser with long-term stability).

  20. Peripheral Processing Facilitates Optic Flow-Based Depth Perception

    PubMed Central

    Li, Jinglin; Lindemann, Jens P.; Egelhaaf, Martin

    2016-01-01

    Flying insects, such as flies or bees, rely on consistent information regarding the depth structure of the environment when performing their flight maneuvers in cluttered natural environments. These behaviors include avoiding collisions, approaching targets or spatial navigation. Insects are thought to obtain depth information visually from the retinal image displacements (“optic flow”) during translational ego-motion. Optic flow in the insect visual system is processed by a mechanism that can be modeled by correlation-type elementary motion detectors (EMDs). However, it is still an open question how spatial information can be extracted reliably from the responses of the highly contrast- and pattern-dependent EMD responses, especially if the vast range of light intensities encountered in natural environments is taken into account. This question will be addressed here by systematically modeling the peripheral visual system of flies, including various adaptive mechanisms. Different model variants of the peripheral visual system were stimulated with image sequences that mimic the panoramic visual input during translational ego-motion in various natural environments, and the resulting peripheral signals were fed into an array of EMDs. We characterized the influence of each peripheral computational unit on the representation of spatial information in the EMD responses. Our model simulations reveal that information about the overall light level needs to be eliminated from the EMD input as is accomplished under light-adapted conditions in the insect peripheral visual system. The response characteristics of large monopolar cells (LMCs) resemble that of a band-pass filter, which reduces the contrast dependency of EMDs strongly, effectively enhancing the representation of the nearness of objects and, especially, of their contours. We furthermore show that local brightness adaptation of photoreceptors allows for spatial vision under a wide range of dynamic light

  1. Eight-year climatology of dust optical depth on Mars

    NASA Astrophysics Data System (ADS)

    Montabone, L.; Forget, F.; Millour, E.; Wilson, R. J.; Lewis, S. R.; Cantor, B.; Kass, D.; Kleinböhl, A.; Lemmon, M. T.; Smith, M. D.; Wolff, M. J.

    2015-05-01

    We have produced a multiannual climatology of airborne dust from martian year 24-31 using multiple datasets of retrieved or estimated column optical depths. The datasets are based on observations of the martian atmosphere from April 1999 to July 2013 made by different orbiting instruments: the Thermal Emission Spectrometer (TES) aboard Mars Global Surveyor, the Thermal Emission Imaging System (THEMIS) aboard Mars Odyssey, and the Mars Climate Sounder (MCS) aboard Mars Reconnaissance Orbiter (MRO). The procedure we have adopted consists of gridding the available retrievals of column dust optical depth (CDOD) from TES and THEMIS nadir observations, as well as the estimates of this quantity from MCS limb observations. Our gridding method calculates averages and uncertainties on a regularly spaced spatio-temporal grid, using an iterative procedure that is weighted in space, time, and retrieval quality. The lack of observations at certain times and locations introduces missing grid points in the maps, which therefore may result in irregularly gridded (i.e. incomplete) fields. In order to evaluate the strengths and weaknesses of the resulting gridded maps, we compare with independent observations of CDOD by PanCam cameras and Mini-TES spectrometers aboard the Mars Exploration Rovers "Spirit" and "Opportunity", by the Surface Stereo Imager aboard the Phoenix lander, and by the Compact Reconnaissance Imaging Spectrometer for Mars aboard MRO. We have statistically analyzed the irregularly gridded maps to provide an overview of the dust climatology on Mars over eight years, specifically in relation to its interseasonal and interannual variability, in addition to provide a basis for instrument intercomparison. Finally, we have produced regularly gridded maps of CDOD by spatially interpolating the irregularly gridded maps using a kriging method. These complete maps are used as dust scenarios in the Mars Climate Database (MCD) version 5, and are useful in many modeling

  2. Depth-resolved 3D visualization of coronary microvasculature with optical microangiography

    NASA Astrophysics Data System (ADS)

    Qin, Wan; Roberts, Meredith A.; Qi, Xiaoli; Murry, Charles E.; Zheng, Ying; Wang, Ruikang K.

    2016-11-01

    In this study, we propose a novel implementation of optical coherence tomography-based angiography combined with ex vivo perfusion of fixed hearts to visualize coronary microvascular structure and function. The extracorporeal perfusion of Intralipid solution allows depth-resolved angiographic imaging, control of perfusion pressure, and high-resolution optical microangiography. The imaging technique offers new opportunities for microcirculation research in the heart, which has been challenging due to motion artifacts and the lack of independent control of pressure and flow. With the ability to precisely quantify structural and functional features, this imaging platform has broad potential for the study of the pathophysiology of microvasculature in the heart as well as other organs.

  3. Algorithm research of high-precision optical interferometric phase demodulation based on FPGA

    NASA Astrophysics Data System (ADS)

    Zhi, Chunxiao; Sun, Jinghua

    2012-11-01

    Optical interferometric phase demodulation algorithm is provided based on the principle of phase generated carrier (PGC), which can realize the optical interference measurement of high-precision signal demodulation, applied to optical fiber displacement, vibration sensor. Modulated photoelectric detection signal is performanced by interval 8 frequency multiplication sampling. The samples calculate the phase modulation depth and phase error through a feedback loop to achieve optimum working point control. On the other hand the results of sampling calculate precision of numerical of the phase. The algorithm uses the addition and subtraction method instead of correlation filtering and other related complex calculation process of the traditional PGC digital demodulation, making full use of FPGA data processing with advantage of high speed and parallel; This method can give full play to the advantage of FPGA performance. Otherwise, the speed at the same time, FPGA can also ensure that the phase demodulation precision, wide dynamic range, and give full play to the advantage of completing the data access by single clock cycle.

  4. The Optical Depth Sensor (ODS) for Mars atmosphere

    NASA Astrophysics Data System (ADS)

    Toledo, D.; Rannou, P.; Pommereau, J.-P.; Sarkissian, A.; Foujols, T.

    2013-09-01

    A small and sophisticated optical depth sensor (ODS) has been designed to work in the martian atmosphere. The principal goal of ODS is to carry out the opacity due to the Martian dust as well as to characterize the high altitude clouds at twilight, crucial parameters in understanding of Martian meteorology. The instrument was initially designed for the failed MARS96 Russian mission, and also was included in the payload of several other missions [1]. Until recently, it was selected (NASA/ESA AO) in the payload of the atmospheric package DREAMS onboard the MARS 2016 mission. But following a decision of the CNES, it is no more included in the payload. In order to study the performance of ODS under a wide range of conditions as well as its capable to provide daily measurements of both dust optical thickness and high altitude clouds, the instrument has participated in different terrestrial campaigns. A good performance of ODS prototype (Figure 1) on cirrus clouds detection and in dust opacity estimation was previously archived in Africa during 2004-2005 and in Brasil from 2012 to nowadays. Moreover, a campaign in the arctic is expected before 2016 where fifteen ODSs will be part of an integrated observing system over the Arctic Ocean, allowing test the ODS performance in extreme conditions. In this presentation we present main principle of the retrieval, the instrumental concept, the result of the tests performed and the principal objectives of ODS in Mars.

  5. The Optical Depth Sensor (ODS) for Mars atmosphere

    NASA Astrophysics Data System (ADS)

    Toledo, D.; Rannou, P.; Pommereau, J.-P.; Sarkissian, A.; Foujols, T.

    2015-10-01

    A small and sophisticated optical depth sensor (ODS) has been designed to work in both Martian and Earth environments. The principal goal of ODS is to carry out the opacity due to the Martian dust as well as to characterize the high altitude clouds at twilight, crucial parameters in understanding of Martian meteorology. The instrument was initially designed for the failed MARS96 Russian mission, and also was included in the payload of several other missions [1]. Until recently, it was selected (NASA/ESA AO) in the payload of the atmospheric package DREAMS onboard the MARS 2016 mission. But following a decision of the CNES, it is no more included in the payload. In order to study the performance of ODS under a wide range of conditions as well as its capable to provide daily measurements of both dust optical thickness and high altitude clouds properties, the instrument has participated in different terrestrial campaigns. A good performance of ODS prototype (Figure 1) on cirrus clouds detection and in dust opacity estimation was previously archived in Africa during 2004-2005 and in Brasil from 2012 to nowadays. Moreover, a campaign in the arctic is expected before 2016 where fifteen ODSs will be part of an integrated observing system over the Arctic Ocean, allowing test the ODS performance in extreme conditions. In this presentation we present main principle of the retrieval, the instrumental concept, the result of the tests performed and the principal objectives of ODS in Mars.

  6. A novel precision face grinder for advanced optic manufacture

    NASA Astrophysics Data System (ADS)

    Guo, Y.; Peng, Y.; Wang, Z.; Yang, W.; Bi, G.; Ke, X.; Lin, X.

    2010-10-01

    In this paper, a large-scale NC precision face grinding machine is developed. This grinding machine can be used to the precision machining of brittle materials. The base and the machine body are independent and the whole structure is configured as a "T" type. The vertical column is seat onto the machine body at the middle center part through a double of precision lead rails. The grinding wheel is driven with a hydraulic dynamic and static spindle. The worktable is supported with a novel split thin film throttle hydrostatic lead rails. Each of motion-axis of the grinding machine is equipped with a Heidenhain absolute linear encoder, and then a closed feedback control system is formed with the adopted Fanuc 0i-MD NC system. The machine is capable of machining extremely flat surfaces on workpiece up to 800mmx600mm. The maximums load bearing of the work table is 620Kg. Furthermore, the roughness of the machined surfaces should be smooth (Ra<50nm-100nm), and the form accuracy less than 2μm (+/-1μm)/200x200mm. After the assembly and debugging of the surface grinding machine, the worktable surface has been self-ground with 60# grinding wheel and the form accuracy is 3μm/600mm×800mm. Then the grinding experiment was conduct on a BK7 flat optic glass element (400mmx250mm) and a ceramic disc (Φ100mm) with 60# grinding wheel, and the measuring results show the surface roughness and the form accuracy of the optic glass device are 0.07μm and 1.56μm/200x200mm, and these of the ceramic disc are 0.52μm and 1.28μm respectively.

  7. High precision optical finishing of lightweight silicon carbide aspheric mirror

    NASA Astrophysics Data System (ADS)

    Kong, John; Young, Kevin

    2010-10-01

    Critical to the deployment of large surveillance optics into the space environment is the generation of high quality optics. Traditionally, aluminum, glass and beryllium have been used; however, silicon carbide becomes of increasing interest and availability due to its high strength. With the hardness of silicon carbide being similar to diamond, traditional polishing methods suffer from slow material removal rates, difficulty in achieving the desired figure and inherent risk of causing catastrophic damage to the lightweight structure. Rather than increasing structural capacity and mass of the substrate, our proprietary sub-aperture aspheric surface forming technology offers higher material removal rates (comparable to that of Zerodur or Fused Silica), a deterministic approach to achieving the desired figure while minimizing contact area and the resulting load on the optical structure. The technology performed on computer-controlled machines with motion control software providing precise and quick convergence of surface figure, as demonstrated by optically finishing lightweight silicon carbide aspheres. At the same time, it also offers the advantage of ideal pitch finish of low surface micro-roughness and low mid-spatial frequency error. This method provides a solution applicable to all common silicon carbide substrate materials, including substrates with CVD silicon carbide cladding, offered by major silicon carbide material suppliers. This paper discusses a demonstration mirror we polished using this novel technology. The mirror is a lightweight silicon carbide substrate with CVD silicon carbide cladding. It is a convex hyperbolic secondary mirror with 104mm diameter and approximately 20 microns aspheric departure from best-fit sphere. The mirror has been finished with surface irregularity of better than 1/50 wave RMS @632.8 nm and surface micro-roughness of under 2 angstroms RMS. The technology has the potential to be scaled up for manufacturing capabilities of

  8. Precision 3-D microscopy with intensity modulated fibre optic scanners

    NASA Astrophysics Data System (ADS)

    Olmos, P.

    2016-01-01

    Optical 3-D imagers constitute a family of precision and useful instruments, easily available on the market in a wide variety of configurations and performances. However, besides their cost they usually provide an image of the object (i.e. a more or less faithful representation of the reality) instead of a truly object's reconstruction. Depending on the detailed working principles of the equipment, this reconstruction may become a challenging task. Here a very simple yet reliable device is described; it is able to form images of opaque objects by illuminating them with an optical fibre and collecting the reflected light with another fibre. Its 3-D capability comes from the spatial filtering imposed by the fibres together with their movement (scanning) along the three directions: transversal (surface) and vertical. This unsophisticated approach allows one to model accurately the entire optical process and to perform the desired reconstruction, finding that information about the surface which is of interest: its profile and its reflectance, ultimately related to the type of material.

  9. Precision laser processing for micro electronics and fiber optic manufacturing

    NASA Astrophysics Data System (ADS)

    Webb, Andrew; Osborne, Mike; Foster-Turner, Gideon; Dinkel, Duane W.

    2008-02-01

    The application of laser based materials processing for precision micro scale manufacturing in the electronics and fiber optic industry is becoming increasingly widespread and accepted. This presentation will review latest laser technologies available and discuss the issues to be considered in choosing the most appropriate laser and processing parameters. High repetition rate, short duration pulsed lasers have improved rapidly in recent years in terms of both performance and reliability enabling flexible, cost effective processing of many material types including metal, silicon, plastic, ceramic and glass. Demonstrating the relevance of laser micromachining, application examples where laser processing is in use for production will be presented, including miniaturization of surface mount capacitors by applying a laser technique for demetalization of tracks in the capacitor manufacturing process and high quality laser machining of fiber optics including stripping, cleaving and lensing, resulting in optical quality finishes without the need for traditional polishing. Applications include telecoms, biomedical and sensing. OpTek Systems was formed in 2000 and provide fully integrated systems and sub contract services for laser processes. They are headquartered in the UK and are establishing a presence in North America through a laser processing facility in South Carolina and sales office in the North East.

  10. Monitoring plant water status and rooting depth for precision irrigation in the vineyards of Classic Karst

    NASA Astrophysics Data System (ADS)

    Savi, Tadeja; Moretti, Elisa; Dal Borgo, Anna; Petruzzellis, Francesco; Stenni, Barbara; Bertoncin, Paolo; Dreossi, Giuliano; Zini, Luca; Martellos, Stefano; Nardini, Andrea

    2017-04-01

    The extreme summer drought and heat waves that occurred in South-Europe in 2003 and 2012 have led to the loss of more than 50% of winery production in the Classic Karst (NE Italy). The irrigation of vineyards in this area is not appropriately developed and, when used, it does not consider the actual water status and needs of plants, posing risks of inappropriate or useless usage of large water volumes. The predicted future increase in frequency and severity of extreme climate events poses at serious risk the local agriculture based on wine business. We monitored seasonal trends of pre-dawn (Ψpd) and minimum (Ψmin) leaf water potential, and stomatal conductance (gL) of 'Malvasia' grapevine in one mature (MV, both in 2015 and 2016) and one young vineyard (YV, in 2016). Moreover, we extracted xylem sap form plant stems and soil water from samples collected in nearby caves, by cryo-vacuum distillation. We also collected precipitation and irrigation water in different months. Oxygen isotope composition (δ18O) of atmospheric, plant, soil and irrigation water was analyzed to get information about rooting depth. In 2015, at the peak of summer aridity, two irrigation treatments were applied according to traditional management practices. The treatments were performed in a sub-area of the MV, followed by physiological analysis and yield measurements at grape harvest. In 2016, the soil water potential (Ψsoil) at 50 cm depth was also monitored throughout the season. Under harsh environmental conditions the apparently deep root system ensured relatively favorable plant water status in both MV and YV and during both growing seasons. The Ψsoil at 50 cm depth gradually decreased as drought progressed, reaching a minimum value of about -1.7 MPa, far more negative than Ψpd recorded in plants (about -0.5 MPa). In July, significant stomatal closure was observed, but Ψmin never surpassed the critical threshold of -1.3 MPa, indicating that irrigation was not needed. The xylem sap

  11. Study on manufacturing method of optical surface with high precision in angle and surface

    NASA Astrophysics Data System (ADS)

    Yu, Xin; Li, Xin; Yu, Ze; Zhao, Bin; Zhang, Xuebin; Sun, Lipeng; Tong, Yi

    2016-10-01

    This paper studied a manufacturing processing of optical surface with high precision in angel and surface. By theoretical analysis of the relationships between the angel precision and surface, the measurement conversion of the technical indicators, optical-cement method application, the optical-cement tooling design, the experiment has been finished successfully, the processing method has been verified, which can be also used in the manufacturing of the optical surface with similar high precision in angle and surface.

  12. Precision targeting with a tracking adaptive optics scanning laser ophthalmoscope

    NASA Astrophysics Data System (ADS)

    Hammer, Daniel X.; Ferguson, R. Daniel; Bigelow, Chad E.; Iftimia, Nicusor V.; Ustun, Teoman E.; Noojin, Gary D.; Stolarski, David J.; Hodnett, Harvey M.; Imholte, Michelle L.; Kumru, Semih S.; McCall, Michelle N.; Toth, Cynthia A.; Rockwell, Benjamin A.

    2006-02-01

    Precise targeting of retinal structures including retinal pigment epithelial cells, feeder vessels, ganglion cells, photoreceptors, and other cells important for light transduction may enable earlier disease intervention with laser therapies and advanced methods for vision studies. A novel imaging system based upon scanning laser ophthalmoscopy (SLO) with adaptive optics (AO) and active image stabilization was designed, developed, and tested in humans and animals. An additional port allows delivery of aberration-corrected therapeutic/stimulus laser sources. The system design includes simultaneous presentation of non-AO, wide-field (~40 deg) and AO, high-magnification (1-2 deg) retinal scans easily positioned anywhere on the retina in a drag-and-drop manner. The AO optical design achieves an error of <0.45 waves (at 800 nm) over +/-6 deg on the retina. A MEMS-based deformable mirror (Boston Micromachines Inc.) is used for wave-front correction. The third generation retinal tracking system achieves a bandwidth of greater than 1 kHz allowing acquisition of stabilized AO images with an accuracy of ~10 μm. Normal adult human volunteers and animals with previously-placed lesions (cynomolgus monkeys) were tested to optimize the tracking instrumentation and to characterize AO imaging performance. Ultrafast laser pulses were delivered to monkeys to characterize the ability to precisely place lesions and stimulus beams. Other advanced features such as real-time image averaging, automatic highresolution mosaic generation, and automatic blink detection and tracking re-lock were also tested. The system has the potential to become an important tool to clinicians and researchers for early detection and treatment of retinal diseases.

  13. Atomically precise metal nanoclusters: stable sizes and optical properties

    NASA Astrophysics Data System (ADS)

    Jin, Rongchao

    2015-01-01

    Controlling nanoparticles with atomic precision has long been a major dream of nanochemists. Breakthroughs have been made in the case of gold nanoparticles, at least for nanoparticles smaller than ~3 nm in diameter. Such ultrasmall gold nanoparticles indeed exhibit fundamentally different properties from those of the plasmonic counterparts owing to the quantum size effects as well as the extremely high surface-to-volume ratio. These unique nanoparticles are often called nanoclusters to distinguish them from conventional plasmonic nanoparticles. Intense work carried out in the last few years has generated a library of stable sizes (or stable stoichiometries) of atomically precise gold nanoclusters, which are opening up new exciting opportunities for both fundamental research and technological applications. In this review, we have summarized the recent progress in the research of thiolate (SR)-protected gold nanoclusters with a focus on the reported stable sizes and their optical absorption spectra. The crystallization of nanoclusters still remains challenging; nevertheless, a few more structures have been achieved since the earlier successes in Au102(SR)44, Au25(SR)18 and Au38(SR)24 nanoclusters, and the newly reported structures include Au20(SR)16, Au24(SR)20, Au28(SR)20, Au30S(SR)18, and Au36(SR)24. Phosphine-protected gold and thiolate-protected silver nanoclusters are also briefly discussed in this review. The reported gold nanocluster sizes serve as the basis for investigating their size dependent properties as well as the development of applications in catalysis, sensing, biological labelling, optics, etc. Future efforts will continue to address what stable sizes are existent, and more importantly, what factors determine their stability. Structural determination and theoretical simulations will help to gain deep insight into the structure-property relationships.

  14. Atomically precise metal nanoclusters: stable sizes and optical properties.

    PubMed

    Jin, Rongchao

    2015-02-07

    Controlling nanoparticles with atomic precision has long been a major dream of nanochemists. Breakthroughs have been made in the case of gold nanoparticles, at least for nanoparticles smaller than ∼3 nm in diameter. Such ultrasmall gold nanoparticles indeed exhibit fundamentally different properties from those of the plasmonic counterparts owing to the quantum size effects as well as the extremely high surface-to-volume ratio. These unique nanoparticles are often called nanoclusters to distinguish them from conventional plasmonic nanoparticles. Intense work carried out in the last few years has generated a library of stable sizes (or stable stoichiometries) of atomically precise gold nanoclusters, which are opening up new exciting opportunities for both fundamental research and technological applications. In this review, we have summarized the recent progress in the research of thiolate (SR)-protected gold nanoclusters with a focus on the reported stable sizes and their optical absorption spectra. The crystallization of nanoclusters still remains challenging; nevertheless, a few more structures have been achieved since the earlier successes in Au102(SR)44, Au25(SR)18 and Au38(SR)24 nanoclusters, and the newly reported structures include Au20(SR)16, Au24(SR)20, Au28(SR)20, Au30S(SR)18, and Au36(SR)24. Phosphine-protected gold and thiolate-protected silver nanoclusters are also briefly discussed in this review. The reported gold nanocluster sizes serve as the basis for investigating their size dependent properties as well as the development of applications in catalysis, sensing, biological labelling, optics, etc. Future efforts will continue to address what stable sizes are existent, and more importantly, what factors determine their stability. Structural determination and theoretical simulations will help to gain deep insight into the structure-property relationships.

  15. Optical sensor for precision in-situ spindle health monitoring

    NASA Astrophysics Data System (ADS)

    Zhao, Rui

    An optical sensor which can record in-situ measurements of the dynamic runout of a precision miniature spindle system in a simple and low-cost manner is proposed in this dissertation. Spindle error measurement technology utilizes a cylindrical or spherical target artifact attached to the miniature spindle with non-contact sensors, typically capacitive sensors which are calibrated with a flat target surface not a curved target surface. Due to the different behavior of an electric field between a flat plate and a curved surface and an electric field between two flat plates, capacitive sensors is not suitable for measuring target surfaces smaller than its effective sensing area. The proposed sensor utilizes curved-edge diffraction (CED), which uses the effect of cylindrical surface curvature on the diffraction phenomenon in the transition regions adjacent to shadow, transmission, and reflection boundaries. The laser diodes light incident on the cylindrical surface of precision spindle and photodetectors collect the total field produced by the diffraction around the target surface. Laser diode in the different two direction are incident to the spindle shaft edges along the X and Y axes, four photodetectors collect the total fields produced by interference of multiple waves due to CED around the spindle shaft edges. The X and Y displacement can be obtained from the total fields using two differential amplifier configurations, respectively. Precision miniature spindle (shaft φ5.0mm) runout was measured, and the proposed sensor can perform curve at the different speed of rotation from 1500rpm to 8000rpm in the X and Y axes, respectively. On the other hand, CED also show changes for different running time and temperature of spindle. These results indicate that the proposed sensor promises to be effective for in-situ monitoring of the miniature spindle's health with high resolution, wide bandwidth, and low-cost.

  16. Aerosol optical depth trend over the Middle East

    NASA Astrophysics Data System (ADS)

    Klingmueller, Klaus; Pozzer, Andrea; Metzger, Swen; Abdelkader, Mohamed; Stenchikov, Georgiy; Lelieveld, Jos

    2016-04-01

    We use the combined Dark Target/Deep Blue aerosol optical depth (AOD) satellite product of the Moderate-resolution Imaging Spectroradiometer (MODIS) collection 6 to study trends over the Middle East between 2000 and 2015. Our analysis corroborates a previously identified positive AOD trend over large parts of the Middle East during the period 2001 to 2012. By relating the annual AOD to precipitation, soil moisture and surface wind, being the main factors controlling the dust cycle, we identify regions where these attributes are significantly correlated to the AOD over Saudi Arabia, Iraq and Iran. The Fertile Crescent turns out to be of prime importance for the AOD trend over these countries. Using multiple linear regression we show that AOD trend and interannual variability can be attributed to the above mentioned dust cycle parameters, confirming that the AOD increase is predominantly driven by dust. In particular, the positive AOD trend relates to a negative soil moisture trend. This suggests that increasing temperature and decreasing relative humidity in the last decade have promoted soil drying, leading to increased dust emissions and AOD; consequently an AOD increase is expected due to climate change. Based on simulations using the ECHAM/MESSy atmospheric chemistry-climate model (EMAC), we interpret the correlations identified in the observational data in terms of causal relationships.

  17. An observationally constrained estimate of global dust aerosol optical depth

    SciTech Connect

    Ridley, David A.; Heald, Colette L.; Kok, Jasper F.; Zhao, Chun

    2016-12-06

    Here, the role of mineral dust in climate and ecosystems has been largely quantified using global climate and chemistry model simulations of dust emission, transport, and deposition. However, differences between these model simulations are substantial, with estimates of global dust aerosol optical depth (AOD) that vary by over a factor of 5. Here we develop an observationally based estimate of the global dust AOD, using multiple satellite platforms, in situ AOD observations and four state-of-the-science global models over 2004–2008. We estimate that the global dust AOD at 550 nm is 0.030 ± 0.005 (1σ), higher than the AeroCom model median (0.023) and substantially narrowing the uncertainty. The methodology used provides regional, seasonal dust AOD and the associated statistical uncertainty for key dust regions around the globe with which model dust schemes can be evaluated. Exploring the regional and seasonal differences in dust AOD between our observationally based estimate and the four models in this study, we find that emissions in Africa are often overrepresented at the expense of Asian and Middle Eastern emissions and that dust removal appears to be too rapid in most models.

  18. An observationally constrained estimate of global dust aerosol optical depth

    DOE PAGES

    Ridley, David A.; Heald, Colette L.; Kok, Jasper F.; ...

    2016-12-06

    Here, the role of mineral dust in climate and ecosystems has been largely quantified using global climate and chemistry model simulations of dust emission, transport, and deposition. However, differences between these model simulations are substantial, with estimates of global dust aerosol optical depth (AOD) that vary by over a factor of 5. Here we develop an observationally based estimate of the global dust AOD, using multiple satellite platforms, in situ AOD observations and four state-of-the-science global models over 2004–2008. We estimate that the global dust AOD at 550 nm is 0.030 ± 0.005 (1σ), higher than the AeroCom model medianmore » (0.023) and substantially narrowing the uncertainty. The methodology used provides regional, seasonal dust AOD and the associated statistical uncertainty for key dust regions around the globe with which model dust schemes can be evaluated. Exploring the regional and seasonal differences in dust AOD between our observationally based estimate and the four models in this study, we find that emissions in Africa are often overrepresented at the expense of Asian and Middle Eastern emissions and that dust removal appears to be too rapid in most models.« less

  19. [C II] 158 um optical depth and self-absorption

    NASA Astrophysics Data System (ADS)

    Guevara, Cristian

    2015-10-01

    Recent observations with SOFIA/GREAT at very high velocity resolution have shown for two prototype PDR sources (Orion B and M17 SW) that the [CII] line has much higher opacities, ranging from 1 to 3, than predicted by simple PDR models and is heavily affected by self-absorption. Under these conditions, line ratios of fine structure lines derived from spectrally unresolved observations and line-integrated intensities, when blindly used to derive physical source properties such as UV-intensity and density in both Galactic and extragalactic environments, give questionable results. In order to understand in what fraction of sources the [CII] emission is affected, and if so, how strongly it is affected by such high, unexpected optical depth and self-absorption, we propose to use the high sensitivity and resolving power of the new upGREAT receiver array for a systematic study of the [CII] opacity and the possible effects of self-absorption with deep integrations of the [13CII] line, by observing several PDR sources covering a range of physical properties and conditions.

  20. Developing Geostationary Satellite Imaging at the Navy Precision Optical Interferometer

    NASA Astrophysics Data System (ADS)

    van Belle, G.; von Braun, K.; Armstrong, J. T.; Baines, E. K.; Schmitt, H. R.; Jorgensen, A. M.; Elias, N.; Mozurkewich, D.; Oppenheimer, R.; Restaino, S.

    The Navy Precision Optical Interferometer (NPOI) is a six-beam long-baseline optical interferometer, located in Flagstaff, Arizona; the facility is operated by a partnership between Lowell Observatory, the US Naval Observatory, and the Naval Research Laboratory. NPOI operates every night of the year (except holidays) in the visible with baselines between 8 and 100 meters (up to 432m is available), conducting programs of astronomical research and technology development for the partners. NPOI is the only such facility as yet to directly observe geostationary satellites, enabling milliarcsecond resolution of these objects. To enhance this capability towards true imaging of geosats, a program of facility upgrades will be outlined. These upgrades include AO-assisted large apertures feeding each beam line, new visible and near-infrared instrumentation on the back end, and infrastructure supporting baseline-wavelength bootstrapping which takes advantage of the spectral and morphological features of geosats. The large apertures will enable year-round observations of objects brighter than 10th magnitude in the near-IR. At its core, the system is enabled by a approach that tracks the low-resolution (and thus, high signal-to-noise), bright near-IR fringes between aperture pairs, allowing multi-aperture phasing for high-resolution visible light imaging. A complementary program of visible speckle and aperture masked imaging at Lowell's 4.3-m Discovery Channel Telescope, for constraining the low-spatial frequency imaging information, will also be outlined, including results from a pilot imaging study.

  1. Precision Assembly of Complex Cellular Microenvironments using Holographic Optical Tweezers

    PubMed Central

    Kirkham, Glen R.; Britchford, Emily; Upton, Thomas; Ware, James; Gibson, Graham M.; Devaud, Yannick; Ehrbar, Martin; Padgett, Miles; Allen, Stephanie; Buttery, Lee D.; Shakesheff, Kevin

    2015-01-01

    The accurate study of cellular microenvironments is limited by the lack of technologies that can manipulate cells in 3D at a sufficiently small length scale. The ability to build and manipulate multicellular microscopic structures will facilitate a more detailed understanding of cellular function in fields such as developmental and stem cell biology. We present a holographic optical tweezers based technology to accurately generate bespoke cellular micro-architectures. Using embryonic stem cells, 3D structures of varying geometries were created and stabilized using hydrogels and cell-cell adhesion methods. Control of chemical microenvironments was achieved by the temporal release of specific factors from polymer microparticles positioned within these constructs. Complex co-culture micro-environmental analogues were also generated to reproduce structures found within adult stem cell niches. The application of holographic optical tweezers-based micromanipulation will enable novel insights into biological microenvironments by allowing researchers to form complex architectures with sub-micron precision of cells, matrices and molecules. PMID:25716032

  2. Precision assembly of complex cellular microenvironments using holographic optical tweezers.

    PubMed

    Kirkham, Glen R; Britchford, Emily; Upton, Thomas; Ware, James; Gibson, Graham M; Devaud, Yannick; Ehrbar, Martin; Padgett, Miles; Allen, Stephanie; Buttery, Lee D; Shakesheff, Kevin

    2015-02-26

    The accurate study of cellular microenvironments is limited by the lack of technologies that can manipulate cells in 3D at a sufficiently small length scale. The ability to build and manipulate multicellular microscopic structures will facilitate a more detailed understanding of cellular function in fields such as developmental and stem cell biology. We present a holographic optical tweezers based technology to accurately generate bespoke cellular micro-architectures. Using embryonic stem cells, 3D structures of varying geometries were created and stabilized using hydrogels and cell-cell adhesion methods. Control of chemical microenvironments was achieved by the temporal release of specific factors from polymer microparticles positioned within these constructs. Complex co-culture micro-environmental analogues were also generated to reproduce structures found within adult stem cell niches. The application of holographic optical tweezers-based micromanipulation will enable novel insights into biological microenvironments by allowing researchers to form complex architectures with sub-micron precision of cells, matrices and molecules.

  3. An Atmospheric Radiation Measurement Value-Added Product to Retrieve Optically Thin Cloud Visible Optical Depth using Micropulse Lidar

    SciTech Connect

    Lo, C; Comstock, JM; Flynn, C

    2006-10-01

    The purpose of the Micropulse Lidar (MPL) Cloud Optical Depth (MPLCOD) Value-Added Product (VAP) is to retrieve the visible (short-wave) cloud optical depth for optically thin clouds using MPL. The advantage of using the MPL to derive optical depth is that lidar is able to detect optically thin cloud layers that may not be detected by millimeter cloud radar or radiometric techniques. The disadvantage of using lidar to derive optical depth is that the lidar signal becomes attenuation limited when τ approaches 3 (this value can vary depending on instrument specifications). As a result, the lidar will not detect optically thin clouds if an optically thick cloud obstructs the lidar beam.

  4. Precise ablation milling with ultrashort pulsed Nd:YAG lasers by optical and acoustical process control

    NASA Astrophysics Data System (ADS)

    Schulze, Volker; Weber, Patricia

    2010-02-01

    Laser ablation milling with ultra short pulsed Nd:YAG lasers enables micro structuring in nearly all kinds of solid materials like metals, ceramics and polymers. A precise machining result with high surface quality requires a defined ablation process. Problems arise through the scatter in the resulting ablation depth of the laser beam machining process where material is removed in layers. Since the ablated volume may change due to varying absorption properties in single layers and inhomogeneities in the material, the focal plane might deviate from the surface of the work piece when the next layer is machined. Thus the focal plane has to be adjusted after each layer. A newly developed optical and acoustical process control enables an in-process adjustment of the focal plane that leads to defined process conditions and thus to better ablation results. The optical process control is realized by assistance of a confocal white light sensor. It enables an automated work piece orientation before machining and an inline ablation depth monitoring. The optical device can be integrated for an online or offline process control. Both variants will be presented and discussed. A further approach for adjustment of the focal plane is the acoustical process control. Acoustic emissions are detected while laser beam machining. A signal analysis of the airborne sound spectrum emitted by the process enables conclusions about the focal position of the laser beam. Based on this correlation an acoustic focus positioning is built up. The focal plane can then be adjusted automatically before ablation.

  5. MatLab program for precision calibration of optical tweezers

    NASA Astrophysics Data System (ADS)

    Tolić-Nørrelykke, Iva Marija; Berg-Sørensen, Kirstine; Flyvbjerg, Henrik

    2004-06-01

    Optical tweezers are used as force transducers in many types of experiments. The force they exert in a given experiment is known only after a calibration. Computer codes that calibrate optical tweezers with high precision and reliability in the ( x, y)-plane orthogonal to the laser beam axis were written in MatLab (MathWorks Inc.) and are presented here. The calibration is based on the power spectrum of the Brownian motion of a dielectric bead trapped in the tweezers. Precision is achieved by accounting for a number of factors that affect this power spectrum. First, cross-talk between channels in 2D position measurements is tested for, and eliminated if detected. Then, the Lorentzian power spectrum that results from the Einstein-Ornstein-Uhlenbeck theory, is fitted to the low-frequency part of the experimental spectrum in order to obtain an initial guess for parameters to be fitted. Finally, a more complete theory is fitted, a theory that optionally accounts for the frequency dependence of the hydrodynamic drag force and hydrodynamic interaction with a nearby cover slip, for effects of finite sampling frequency (aliasing), for effects of anti-aliasing filters in the data acquisition electronics, and for unintended "virtual" filtering caused by the position detection system. Each of these effects can be left out or included as the user prefers, with user-defined parameters. Several tests are applied to the experimental data during calibration to ensure that the data comply with the theory used for their interpretation: Independence of x- and y-coordinates, Hooke's law, exponential distribution of power spectral values, uncorrelated Gaussian scatter of residual values. Results are given with statistical errors and covariance matrix. Program summaryTitle of program: tweezercalib Catalogue identifier: ADTV Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland. Program Summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTV Computer for

  6. Depth-resolved ballistic imaging in a low-depth-of-field optical Kerr gated imaging system

    NASA Astrophysics Data System (ADS)

    Zheng, Yipeng; Tan, Wenjiang; Si, Jinhai; Ren, YuHu; Xu, Shichao; Tong, Junyi; Hou, Xun

    2016-09-01

    We demonstrate depth-resolved imaging in a ballistic imaging system, in which a heterodyned femtosecond optical Kerr gate is introduced to extract useful imaging photons for detecting an object hidden in turbid media and a compound lens is proposed to ensure both the depth-resolved imaging capability and the long working distance. Two objects of about 15-μm widths hidden in a polystyrene-sphere suspension have been successfully imaged with approximately 600-μm depth resolution. Modulation-transfer-function curves with the object in and away from the object plane have also been measured to confirm the depth-resolved imaging capability of the low-depth-of-field (low-DOF) ballistic imaging system. This imaging approach shows potential for application in research of the internal structure of highly scattering fuel spray.

  7. Depth-resolved ballistic imaging in a low-depth-of-field optical Kerr gated imaging system

    SciTech Connect

    Zheng, Yipeng; Tan, Wenjiang Si, Jinhai; Ren, YuHu; Xu, Shichao; Hou, Xun; Tong, Junyi

    2016-09-07

    We demonstrate depth-resolved imaging in a ballistic imaging system, in which a heterodyned femtosecond optical Kerr gate is introduced to extract useful imaging photons for detecting an object hidden in turbid media and a compound lens is proposed to ensure both the depth-resolved imaging capability and the long working distance. Two objects of about 15-μm widths hidden in a polystyrene-sphere suspension have been successfully imaged with approximately 600-μm depth resolution. Modulation-transfer-function curves with the object in and away from the object plane have also been measured to confirm the depth-resolved imaging capability of the low-depth-of-field (low-DOF) ballistic imaging system. This imaging approach shows potential for application in research of the internal structure of highly scattering fuel spray.

  8. Programmable diffractive optical elements for extending the depth of focus in ophthalmic optics

    NASA Astrophysics Data System (ADS)

    Romero, Lenny A.; Millán, María. S.; Jaroszewicz, Zbigniew; Kołodziejczyk, Andrzej

    2015-01-01

    The depth of focus (DOF) defines the axial range of high lateral resolution in the image space for object position. Optical devices with a traditional lens system typically have a limited DOF. However, there are applications such as in ophthalmology, which require a large DOF in comparison to a traditional optical system, this is commonly known as extended DOF (EDOF). In this paper we explore Programmable Diffractive Optical Elements (PDOEs), with EDOF, as an alternative solution to visual impairments, especially presbyopia. These DOEs were written onto a reflective liquid cystal on silicon (LCoS) spatial light modulator (SLM). Several designs of the elements are analyzed: the Forward Logarithmic Axicon (FLAX), the Axilens (AXL), the Light sword Optical Element (LSOE), the Peacock Eye Optical Element (PE) and Double Peacock Eye Optical Element (DPE). These elements focus an incident plane wave into a segment of the optical axis. The performances of the PDOEs are compared with those of multifocal lenses. In all cases, we obtained the point spread function and the image of an extended object. The results are presented and discussed.

  9. Ice Cloud Optical Depth Retrievals from CRISM Multispectral Images

    NASA Astrophysics Data System (ADS)

    Klassen, David R.

    2014-11-01

    cubes.Presented here are the results of this PCA/TT work to find the singular set of spectral endmembers and their use in recovering ice cloud optical depth from the MRO-CRISM multispectral image cubes.

  10. Aerosol optical depth increase in partly cloudy conditions

    NASA Astrophysics Data System (ADS)

    Chand, Duli; Wood, Robert; Ghan, Steven J.; Wang, Minghuai; Ovchinnikov, Mikhail; Rasch, Philip J.; Miller, Steven; Schichtel, Bret; Moore, Tom

    2012-09-01

    Remote sensing observations of aerosol from surface and satellite instruments are extensively used for atmospheric and climate research. From passive sensors, the apparent cloud-free atmosphere in the vicinity of clouds often appears to be brighter than further away from the clouds, leading to an increase in the retrieved aerosol optical depth (τ). Mechanisms contributing to this enhancement or increase, including contamination by undetected clouds, hygroscopic growth of aerosol particles, and meteorological conditions, have been debated in recent literature, but the extent to which each of these factors influence the observed enhancement (Δτ) is poorly known. Here we used 11 years of daily global observations at 10 × 10 km2 resolution from the MODIS on the NASA Terra satellite to quantify τ as a function of cloud fraction (CF). Our analysis reveals that, averaged over the globe, the clear sky τ is enhanced by Δτ = 0.05 in cloudy conditions (CF = 0.8-0.9). This enhancement in Δτ corresponds to relative enhancement of 25% in cloudy conditions (CF = 0.8-0.9) compared with relatively clear conditions (CF = 0.1-0.2). Unlike the absolute enhancement Δτ, the relative increase in τis rather consistent in all seasons and is 25-35% in the subtropics and 15-25% at mid and higher latitudes. Using a simple Gaussian probability density function model to connect cloud cover and the distribution of relative humidity, we argue that much of the enhancement is consistent with aerosol hygroscopic growth in the humid environment surrounding clouds. Consideration of these cloud-dependentτeffects will facilitate understanding aerosol-cloud interactions and reduce the uncertainty in estimates of aerosol radiative forcing by global climate models.

  11. Intercomparison of Desert Dust Optical Depth from Satellite Measurements

    NASA Technical Reports Server (NTRS)

    Carboni, E.; Thomas, G. E.; Sayer, A. M.; Siddans, R.; Poulsen, C. A.; Grainger, R. G.; Ahn, C.; Antoine, D.; Bevan, S.; Braak, R.; hide

    2012-01-01

    This work provides a comparison of satellite retrievals of Saharan desert dust aerosol optical depth (AOD) during a strong dust event through March 2006. In this event, a large dust plume was transported over desert, vegetated, and ocean surfaces. The aim is to identify the differences between current datasets. The satellite instruments considered are AATSR, AIRS, MERIS, MISR, MODIS, OMI, POLDER, and SEVIRI. An interesting aspect is that the different algorithms make use of different instrument characteristics to obtain retrievals over bright surfaces. These include multi-angle approaches (MISR, AATSR), polarisation measurements (POLDER), single-view approaches using solar wavelengths (OMI, MODIS), and the thermal infrared spectral region (SEVIRI, AIRS). Differences between instruments, together with the comparison of different retrieval algorithms applied to measurements from the same instrument, provide a unique insight into the performance and characteristics of the various techniques employed. As well as the intercomparison between different satellite products, the AODs have also been compared to co-located AERONET data. Despite the fact that the agreement between satellite and AERONET AODs is reasonably good for all of the datasets, there are significant differences between them when compared to each other, especially over land. These differences are partially due to differences in the algorithms, such as assumptions about aerosol model and surface properties. However, in this comparison of spatially and temporally averaged data, it is important to note that differences in sampling, related to the actual footprint of each instrument on the heterogeneous aerosol field, cloud identification and the quality control flags of each dataset can be an important issue.

  12. Aerosol optical depths and their contributing sources in Taiwan

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Chan, K. L.

    2017-01-01

    In this paper, we present a quantitative investigation of the contributions of different aerosols to the aerosol optical depths (AODs) in Taiwan using a global chemical transport model (GEOS-Chem) and remote sensing measurements. The study focus is on the period from June 2012 to October 2013. Five different types of aerosols are investigated: sea salt, dust, sulfate, organic carbon and black carbon. Three of these aerosols, namely sulfate, organic carbon and black carbon, have significant anthropogenic sources. Model simulation results were compared with both ground based sun photometer measurements and MODerate resolution Imaging Spectroradiometer (MODIS) satellite observations. The model data shows good agreement with satellite observations (R = 0.72) and moderate correlation with sun photometer measurements (R = 0.52). Simulation results show the anthropogenic aerosols contribute ∼65% to the total AOD in Taipei, while natural originated aerosols only show a minor impact (∼35%). Among all the aerosols, sulfate is the dominating species, contributing 62.4% to the annual average total AOD. Organic carbon and black carbons respectively contribute 7.3% and 1.5% to the annual averaged total AOD. The annual average contributions of sea salt and dust aerosols to the total AOD are 26.4% and 2.4%, respectively. A sensitivity study was performed to identify the contributions of anthropogenic aerosol sources in each region to the AODs in Taipei. North-East Asia was identified as the major contributing source region of anthropogenic aerosols to Taipei, accounting for more than 50% of total sulfate, 32% of total organic carbon and 51% of total black carbon aerosols. South-East Asia is the second largest contributing source region, contributing 35%, 24% and 34% of total sulfate, organic carbon and black carbon aerosols, respectively. The aerosols from continents other than Asia only show minor impacts to the aerosol load in Taipei. In addition, a case study of a biomass

  13. Aerosol optical depth increase in partly cloudy conditions

    SciTech Connect

    Chand, Duli; Wood, R.; Ghan, Steven J.; Wang, Minghuai; Ovchinnikov, Mikhail; Rasch, Philip J.; Miller, Steven D.; Schichtel, Bret; Moore, Tom

    2012-09-14

    Remote sensing observations of aerosol from surface and satellite instruments are extensively used for atmospheric and climate research. From passive sensors, the apparent cloud-free atmosphere in the vicinity of clouds often appears to be brighter then further away from the clouds, leading to an enhancement in the retrieved aerosol optical depth. Mechanisms contributing to this enhancement, including contamination by undetected clouds, hygroscopic growth of aerosol particles, and meteorological conditions, have been debated in recent literature, but an extent to which each of these factors influence the observed enhancement is poorly known. Here we used 11 years of daily global observations at 10x10 km2 resolution from the MODIS on the NASA Terra satellite to quantify as a function of cloud fraction (CF). Our analysis reveals that, averaged over the globe, the clear sky is enhanced by ? = 0.05 which corresponds to relative enhancements of 25% in cloudy conditions (CF=0.8-0.9) compared with relatively clear conditions (CF=0.1-0.2). Unlike the absolute enhancement ?, the relative increase in ? is rather consistent in all seasons and is 25-35% in the subtropics and 15-25% at mid and higher latitudes. Using a simple Gaussian probability density function model to connect cloud cover and the distribution of relative humidity, we argue that much of the enhancement is consistent with aerosol hygroscopic growth in the humid environment surrounding clouds. Consideration of these cloud-dependent effects will facilitate understanding aerosol-cloud interactions and reduce the uncertainty in estimates of aerosol radiative forcing by global climate models.

  14. Design of Optical Systems with Extended Depth of Field: An Educational Approach to Wavefront Coding Techniques

    ERIC Educational Resources Information Center

    Ferran, C.; Bosch, S.; Carnicer, A.

    2012-01-01

    A practical activity designed to introduce wavefront coding techniques as a method to extend the depth of field in optical systems is presented. The activity is suitable for advanced undergraduate students since it combines different topics in optical engineering such as optical system design, aberration theory, Fourier optics, and digital image…

  15. Design of Optical Systems with Extended Depth of Field: An Educational Approach to Wavefront Coding Techniques

    ERIC Educational Resources Information Center

    Ferran, C.; Bosch, S.; Carnicer, A.

    2012-01-01

    A practical activity designed to introduce wavefront coding techniques as a method to extend the depth of field in optical systems is presented. The activity is suitable for advanced undergraduate students since it combines different topics in optical engineering such as optical system design, aberration theory, Fourier optics, and digital image…

  16. Random depth access full-field heterodyne low-coherence interferometry utilizing acousto-optic modulation and a complementary metaloxide semiconductor camera.

    PubMed

    Egan, Patrick; Connelly, Michael J; Lakestani, Fereydoun; Whelan, Maurice P

    2006-04-01

    With analog scanning, time-domain low-coherence interferometry lacks precise depth information, and optical carrier generation demands a linear scanning speed. Full-field heterodyne low-coherence interferometry that uses a logarithmic complementary metal-oxide semiconductor camera, acousto-optic modulation, and digital depth stepping is reported, with which random regions of interest, lateral and axial, can be accessed. Furthermore, nanometer profilometry is possible through heterodyne phase retrieval of the interference signal. The approach demonstrates inexpensive yet high-precision functional machine vision offering true digital random access in three dimensions.

  17. Depth sensitivity of frequency domain optical measurements in diffusive media

    PubMed Central

    Sassaroli, Angelo; Torricelli, Alessandro; Spinelli, Lorenzo; Farina, Andrea; Durduran, Turgut; Cavalieri, Stefano; Pifferi, Antonio

    2017-01-01

    The depth sensitivity functions for AC amplitude, phase (PH) and DC intensity signals have been obtained in the frequency domain (where the source amplitude is modulated at radio-frequencies) by making use of analytical solutions of the photon diffusion equation in an infinite slab geometry. Furthermore, solutions for the relative contrast of AC, PH and DC signals when a totally absorbing plane is placed at a fixed depth of the slab have also been obtained. The solutions have been validated by comparisons with gold standard Monte Carlo simulations. The obtained results show that the AC signal, for modulation frequencies < 200 MHz, has a depth sensitivity with similar characteristics to that of the continuous-wave (CW) domain (source modulation frequency of zero). Thus, the depth probed by such a signal can be estimated by using the formula of penetration depth for the CW domain (Sci. Rep. 6, 27057 (2016)27256988). However, the PH signal has a different behavior compared to the CW domain, showing a larger depth sensitivity at shallow depths and a less steep relative contrast as a function of depth. These results mark a clear difference in term of depth sensitivity between AC and PH signals, and highlight the complexity of the estimation of the actual depth probed in tissue spectroscopy. PMID:28663921

  18. Depth sensitivity of frequency domain optical measurements in diffusive media.

    PubMed

    Binzoni, Tiziano; Sassaroli, Angelo; Torricelli, Alessandro; Spinelli, Lorenzo; Farina, Andrea; Durduran, Turgut; Cavalieri, Stefano; Pifferi, Antonio; Martelli, Fabrizio

    2017-06-01

    The depth sensitivity functions for AC amplitude, phase (PH) and DC intensity signals have been obtained in the frequency domain (where the source amplitude is modulated at radio-frequencies) by making use of analytical solutions of the photon diffusion equation in an infinite slab geometry. Furthermore, solutions for the relative contrast of AC, PH and DC signals when a totally absorbing plane is placed at a fixed depth of the slab have also been obtained. The solutions have been validated by comparisons with gold standard Monte Carlo simulations. The obtained results show that the AC signal, for modulation frequencies < 200 MHz, has a depth sensitivity with similar characteristics to that of the continuous-wave (CW) domain (source modulation frequency of zero). Thus, the depth probed by such a signal can be estimated by using the formula of penetration depth for the CW domain (Sci. Rep.6, 27057 (2016)). However, the PH signal has a different behavior compared to the CW domain, showing a larger depth sensitivity at shallow depths and a less steep relative contrast as a function of depth. These results mark a clear difference in term of depth sensitivity between AC and PH signals, and highlight the complexity of the estimation of the actual depth probed in tissue spectroscopy.

  19. Tissue diagnostics by depth profiling of optical characteristics using broadband fiber optic interferometry

    NASA Astrophysics Data System (ADS)

    Splinter, Robert; Farahi, Faramarz; Raja, M. Yasin A.; Svenson, Robert H.

    1996-02-01

    A broadband interferometer is used to acquire scattered light as a function of depth in biological media. The `tissue-light-signature' that is obtained by this depth scan can be correlated with the computer simulated light distributions for well defined tissue parameters, and wavelengths of specific interest. In theory, the collimated irradiation of heart tissue, by low coherence light will generate a statistically significant different light signature for respective myocardial tissues, and pathological tissue conditions. Interferometric axial scanning of in vitro myocardial tissues confirmed the statistically significant difference between normal, coagulated myocardium, and aneurysm at the 790 nm wavelength. The scanning depth however is presented limited by the intensity of the illumination and the choice of detection scheme. Identification of the local optical characteristics as a function of depth directly underneath the target zone will provide discrimination between healthy and pathological conditions in addition to real time assessment of laser dosimetry. Theoretically the scanning depth is limited to a maximum of 4 mm. The beam profile of the irradiation source significantly affects the ability to distinguish between certain tissues. Broadband interferometric axial tissue scanning, will provide a tool for an accurate light energy delivery guided by the desired outcome, while being able to verify the appropriate target location, in real time.

  20. Assessment of Optic Nerve Head Drusen Using Enhanced Depth Imaging and Swept Source Optical Coherence Tomography

    PubMed Central

    Silverman, Anna L.; Tatham, Andrew J.; Medeiros, Felipe A.; Weinreb, Robert N.

    2015-01-01

    Background Optic nerve head drusen (ONHD) are calcific deposits buried or at the surface of the optic disc. Although ONHD may be associated with progressive visual field defects, the mechanism of drusen-related field loss is poorly understood. Methods for detecting and imaging disc drusen include B-scan ultrasonography, fundus autofluorescence, and optical coherence tomography (OCT). These modalities are useful for drusen detection but are limited by low resolution or poor penetration of deep structures. This review was designed to assess the potential role of new OCT technologies in imaging ONHD. Evidence Acquisition Critical appraisal of published literature and comparison of new imaging devices to established technology. Results The new imaging modalities of enhanced depth imaging optical coherence tomography (EDI-OCT) and swept source optical coherence tomography (SS-OCT) are able to provide unprecedented in vivo detail of ONHD. Using these devices it is now possible to quantify optic disc drusen dimensions and assess integrity of neighboring retinal structures, including the retinal nerve fiber layer. Conclusions EDI-OCT and SS-OCT have the potential to allow better detection of longitudinal changes in drusen and neural retina and improve our understanding of drusen-related visual field loss. PMID:24662838

  1. Ion microscopy with resonant ionization mass spectrometry : time-of-flight depth profiling with improved isotopic precision.

    SciTech Connect

    Pellin, M. J.; Veryovkin, I. V.; Levine, J.; Zinovev, A.; Davis, A. M.; Stephan, T.; Tripa, C. E.; King, B. V.; Savina, M. R.

    2010-01-01

    There are four generally mutually exclusive requirements that plague many mass spectrometric measurements of trace constituents: (1) the small size (limited by the depth probed) of many interesting materials requires high useful yields to simply detect some trace elements, (2) the low concentrations of interesting elements require efficient discrimination from isobaric interferences, (3) it is often necessary to measure the depth distribution of elements with high surface and low bulk contributions, and (4) many applications require precise isotopic analysis. Resonant ionization mass spectrometry has made dramatic progress in addressing these difficulties over the past five years.

  2. Surface micro-structuring of glassy carbon for precision glass molding of diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Hermerschmidt, Andreas

    2014-09-01

    Glassy carbon is used nowadays for a variety of applications because of its mechanical strength, thermal stability and non-sticking adhesion properties. This makes it also a suitable candidate as mold material for precision compression molding of low and high glass-transition temperature materials. To fabricate molds for diffractive optics a highresolution structuring technique is needed. We introduce a process that allows the micro-structuring of glassy carbon by reactive ion etching. Key parameters such as uniformity, surface roughness, edge definition and lateral resolution are discussed. They are the most relevant parameters for a stamp in optical applications. The use of titanium as a hard mask makes it possible to achieve a reasonable selectivity of 4:1, which has so far been one of the main problems in microstructuring of glassy carbon. We investigate the titanium surface structure with its 5-10 nm thick layer of TiO2 grains and its influence on the shape of the hard mask. In our fabrication procedure we were able to realize optically flat diffractive structures with slope angles of more than 80° at typical feature sizes of 5 μm and at 700 nm depth. The fabricated glassy carbon molds were applied to thermal imprinting onto different glasses. Glassy carbon molds with 1 mm thickness were tested with binary optical structures. Our experiments show the suitability of glassy carbon as molds for cost efficient mass production with a high quality.

  3. Precision of light intensity measurement in biological optical microscopy.

    PubMed

    Bernas, Tytus; Barnes, David; Asem, Elikplimi K; Robinson, J Paul; Rajwa, Bartek

    2007-05-01

    Standardization and calibration of optical microscopy systems have become an important issue owing to the increasing role of biological imaging in high-content screening technology. The proper interpretation of data from high-content screening imaging experiments requires detailed information about the capabilities of the systems, including their available dynamic range, sensitivity and noise. Currently available techniques for calibration and standardization of digital microscopes commonly used in cell biology laboratories provide an estimation of stability and measurement precision (noise) of an imaging system at a single level of signal intensity. In addition, only the total noise level, not its characteristics (spectrum), is measured. We propose a novel technique for estimation of temporal variability of signal and noise in microscopic imaging. The method requires registration of a time series of images of any stationary biological specimen. The subsequent analysis involves a multi-step process, which separates monotonic, periodic and random components of every pixel intensity change in time. The technique allows simultaneous determination of dark, photonic and multiplicative components of noise present in biological measurements. Consequently, a respective confidence interval (noise level) is obtained for each level of signal. The technique is validated using test sets of biological images with known signal and noise characteristics. The method is also applied to assess uncertainty of measurement obtained with two CCD cameras in a wide-field microscope.

  4. Progress in the expansion of the Navy Precision Optical Interferometer

    NASA Astrophysics Data System (ADS)

    Armstrong, J. T.; Restaino, S. R.; Clark, J. H.; Schmitt, H. R.; Baines, E. K.; Hutter, D. J.; Benson, J. A.; Zavala, R. T.; Shankland, P. D.; van Belle, G.; Jorgensen, A. M.

    2014-01-01

    Over the past three years, the Navy Precision Optical Interferometer (NPOI) has been undergoing significant expansion toward its ultimate design goal of six siderostats that can be moved among up to 30 stations. The additional stations that will become available by next spring include E7 (98 m baseline with W7), plus E10 and W10 (432 m baseline between them). Several other close-in stations will produce baselines as short as 7 m tailored to large-scale targets. Significant upgrades to the NPOI backend are also under way. The VISION beam combiner, based on single-mode fiber spatial filtering and a photon-counting CCD and very similar in design to the MIRC combiner at the CHARA array, has been installed and is on its shakedown cruise. The NPOI's current "Classic" combiner is undergoing firmware improvements that will increase both the spectral range and the number of baselines simultaneously available. Coupled with concurrent improvements to the delay line controllers, these developments should significantly increase data quality and instrumental efficiency. Finally, many of the the initial preparations for adding four 1.8 m telescopes (the former Keck outrigger telescopes, now owned by USNO) have been completed, and funding for the first installations is anticipated.

  5. The new classic instrument for the navy precision optical interferometer

    NASA Astrophysics Data System (ADS)

    Jorgensen, A. M.; Schmitt, H. R.; Armstrong, J. T.; Baines, E. K.; Hindsley, R.; Mozurkewich, D.; van Belle, G. T.

    2016-08-01

    The New Classic instrument was built as a electronics and computer upgrade to the existing Classic beam combiner at the Navy Precision Optical Interferometer (NPOI). The classic beam combiner is able to record 32 of 96 available channels and has a data throughput limitation which results in a low duty cycle. Additionally the computing power of the Classic system limited the amount of fringe tracking that was possible. The New Classic system implements a high-throughput data acquisition system which is capable of recording all 96 channels continuously. It also has a modern high-speed computer for data management and data processing. The computer is sufficiently powerful to implement more sophisticated fringe-tracking algorithms than the Classic system, including multi-baseline bootstrapping. In this paper we described the New Classic hardware and software, including the fringe-tracking algorithm, performance, and the user interface. We also show some initial results from the first 5-station, 4-baseline bootstrapping carried out in January 2015.

  6. Surface errors in the course of machining precision optics

    NASA Astrophysics Data System (ADS)

    Biskup, H.; Haberl, A.; Rascher, R.

    2015-08-01

    Precision optical components are usually machined by grinding and polishing in several steps with increasing accuracy. Spherical surfaces will be finished in a last step with large tools to smooth the surface. The requested surface accuracy of non-spherical surfaces only can be achieved with tools in point contact to the surface. So called mid-frequency errors (MSFE) can accumulate with zonal processes. This work is on the formation of surface errors from grinding to polishing by conducting an analysis of the surfaces in their machining steps by non-contact interferometric methods. The errors on the surface can be distinguished as described in DIN 4760 whereby 2nd to 3rd order errors are the so-called MSFE. By appropriate filtering of the measured data frequencies of errors can be suppressed in a manner that only defined spatial frequencies will be shown in the surface plot. It can be observed that some frequencies already may be formed in the early machining steps like grinding and main-polishing. Additionally it is known that MSFE can be produced by the process itself and other side effects. Beside a description of surface errors based on the limits of measurement technologies, different formation mechanisms for selected spatial frequencies are presented. A correction may be only possible by tools that have a lateral size below the wavelength of the error structure. The presented considerations may be used to develop proposals to handle surface errors.

  7. Effect of probe geometry and optical properties on the sampling depth for diffuse reflectance spectroscopy

    PubMed Central

    Hennessy, Ricky; Goth, Will; Sharma, Manu; Markey, Mia K.; Tunnell, James W.

    2014-01-01

    Abstract. The sampling depth of light for diffuse reflectance spectroscopy is analyzed both experimentally and computationally. A Monte Carlo (MC) model was used to investigate the effect of optical properties and probe geometry on sampling depth. MC model estimates of sampling depth show an excellent agreement with experimental measurements over a wide range of optical properties and probe geometries. The MC data are used to define a mathematical expression for sampling depth that is expressed in terms of optical properties and probe geometry parameters. PMID:25349033

  8. Secchi depth analysis using bio-optical parameters measured in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Suresh, T.; Naik, Puneeta; Bandishte, Mangesh; Desa, Elgar; Mascaranahas, Antonio; Matondkar, S. G. P.

    2006-12-01

    Secchi depth provides the oceanographer with the first hand information about transparency and penetration of light in the water. Here we present results of the Secchi depth and the optical properties measured in the Arabian Sea. Our analyses show spatial and temporal variability of Secchi depth and their dependence on the optical properties beam attenuation and diffuse attenuation the biological parameter of Chlorophyll. The in-situ measured inherent and apparent optical properties have been used to understand the underwater light properties and their relations to the Secchi depth in various water types. The Secchi depth model is validated using the measured optical properties. We also present an empirical method to determine Secchi depth from the satellite ocean color sensor, and the application of the same to the IRS-P4 OCM is found to provide comparable results to the measured values.

  9. Aerosol Optical Depth over Africa retrieved from AATSR

    NASA Astrophysics Data System (ADS)

    Sogacheva, Larisa; de Leeuw, Gerrit; Kolmonen, Pekka; Sundström, Anu-Maija; Rodriques, Edith

    2010-05-01

    Aerosols produced over the African continent have important consequences for climate. In particular, large amounts of desert dust are produced over the Sahara and transported across the North Atlantic where desert dust deposition influences the eco system by iron fertilization, and further North over Europe with outbreaks as far as Scandinavia. Biomass burning occurs in most of the African continent south of the Sahara and causes a net positive radiating forcing resulting in local warming of the atmosphere layers. These effects have been studied during large field campaigns. Satellites can systematically provide information on aerosols over a large area such as Africa and beyond. To this end, we retrieved the Aerosol Optical Depth (AOD) at three wavelengths (555nm, 670nm, and 1600nm) over Africa from the reflectance measured at the top of the atmosphere by the AATSR (Advances Along Track Scanning Radiometer) flying on ENVISAT, for one year (1 May 2008 to 30 April 2009) to obtain information on the seasonal and spatial behaviour of the AOD, episodes of high AOD events and connect the retrieved AOD with the ground-based aerosol measurements. The AOD retrieval algorithm, which is applied to cloud-free pixels over land, is based on the comparison of the measured and modeled reflectance at the top of the atmosphere (TOA). The algorithm uses look-up-tables (LUTs) to compute the modeled TOA reflectance. For AOD retrieval, an aerosol in the atmosphere is assumed to be an external mixture of fine and coarse mode particles. The two aerosol types are mixed such that the spectral behavior of the reflectance due to aerosol best fits the measurements. Comparison with AERONET (Aerosol Roboric NETwork), which is a network of ground-based sun photometers which measure atmospheric aerosol properties, shows good agreement but with some overestimation of the AATSR retrieved AOD. Different aerosol models have been used to improve the comparison. The lack of AERONET stations in Africa

  10. [Effects of sensor's laying depth for precision irrigation on growth characteristics of maturate grapes].

    PubMed

    Wang, Yu-Ning; Fan, Jun; Li, Shi-Qing; Zheng, Chen; Wang, Quan-Jiu

    2012-08-01

    In order to approach the appropriate laying depth of soil moisture sensor to control irrigation amount, the sensors were laid at different soil depth to measure the soil moisture content, with the effects of definite irrigation amount on the growth characteristics of maturate grapes studied. The results showed that using the sensor laying at the soil depth 40 cm (SF40) to control irrigation amount, the biological characteristics of the grapes, including photosynthesis, grape yield, and water use efficiency were superior than those when the sensor was laid at the depth 20 cm (SF20) and under conventional furrow irrigation (CK). The grape brix degree in treatment SF40 was slightly lower than that in treatments SF20 and CK, but was still near 20%. In treatment SF40, the irrigated water could infiltrate or redistribute in the soil layers where the main roots of the grapes existed. It was suggested that laying soil moisture sensor at the depth 40 cm could better control the irrigation amount for the maturate grapes in the study area.

  11. Small optic suspensions for Advanced LIGO input optics and other precision optical experiments.

    PubMed

    Ciani, G; Arain, M A; Aston, S M; Feldbaum, D; Fulda, P; Gleason, J; Heintze, M; Martin, R M; Mueller, C L; Nanda Kumar, D M; Pele, A; Reitze, D H; Sainathan, P; Tanner, D B; Williams, L F; Mueller, G

    2016-11-01

    We report on the design and performance of small optic suspensions developed to suppress seismic motion of out-of-cavity optics in the input optics subsystem of the Advanced Laser Interferometer Gravitational Wave Observatory. These compact single stage suspensions provide isolation in all six degrees of freedom of the optic, local sensing and actuation in three of them, and passive damping for the other three.

  12. Depth-of-field effects in wiggler radiation sources: Geometrical versus wave optics

    NASA Astrophysics Data System (ADS)

    Walker, Richard P.

    2017-02-01

    A detailed analysis is carried out of the optical properties of synchrotron radiation emitted by multipole wigglers, concentrating on the effective source size and brightness and the so-called "depth of field" effects, concerning which there has been some controversy in the literature. By comparing calculations made with both geometrical optics and wave optics methods we demonstrate that the two approaches are not at variance, and that the wave optics results tend towards those of geometrical optics under well-defined conditions.

  13. Ultra-Precision Linear Actuator for optical systems

    NASA Astrophysics Data System (ADS)

    Nalbandian, Ruben

    2000-10-01

    The Ultra-Precision Linear Actuator presented in this paper was developed for the Next Generation Space Telescopes' (NGST) primary mirror surface figure control. The development was a joint effort between Alson E. Hatheway, Inc (AEH) and Moog, Schaeffer Magnetics Division (SMD). The goal of this project was to demonstrate an extremely light weight, relatively high stiffness actuator capable of operating uniformly well over the range of 2- degree(s)K to 300 degree(s)K and achieving diffraction-limited performance (+/- 10 nm) in the optical band for weeks at a time, while consuming no electrical power and dissipating no heat. The essence of the design challenge was to develop a lightweight, high stiffness, low power, thermally stable linear positioning mechanism. Actuation systems with resolutions comparable to that of this design normally are operated in a closed-loop control system to compensate for any non-linearities and hysteresis inherent in their enabling technologies, such as piezoelectric and magnetostrictive transducers. These technologies require continuous application of power and therefore are not low power consumption devices. The development challenge was met through the use of Alson E. Hatheway's (AEH) patented Rubicontm elastic transducer which consists of two elastic elements; a soft spring and a stiff flexural member. Deflection of the soft spring applies a force input to the stiff flexure, which responds with a proportionally reduced output deflection. To maintain linearity, the displacements, and hence the stresses, developed in both elastic members are kept well below the elastic yield strength of the material. The AEH transducer is inherently linear and hysteresis free.

  14. Imaging of Stellar Surfaces with the Navy Precision Optical Interferometer

    NASA Astrophysics Data System (ADS)

    Jorgensen, A.; Schmitt, H. R.; van Belle, G. T.; Hutter, Clark; Mozurkewich, D.; Armstrong, J. T.; Baines, E. K.; Restaino, S. R.

    The Navy Precision Optical Interferometer (NPOI) has a unique layout which is particularly well-suited for high-resolution interferometric imaging. By combining the NPOI layout with a new data acquisition and fringe tracking system we are progressing toward a imaging capability which will exceed any other interferometer in operation. The project, funded by the National Science Foundation, combines several existing advances and infrastructure at NPOI with modest enhancements. For optimal imaging there are several requirements that should be fulfilled. The observatory should be capable of measuring visibilities on a wide range of baseline lengths and orientations, providing complete UV coverage in a short period of time. It should measure visibility amplitudes with good SNR on all baselines as critical imaging information is often contained in low-amplitude visibilities. It should measure the visibility phase on all baselines. The technologies which can achieve this are the NPOI Y-shaped array with (nearly) equal spacing between telescopes and an ability for rapid configuration. Placing 6-telescopes in a row makes it possible to measure visibilities into the 4th lobe of the visibility function. By arranging the available telescopes carefully we will be able to switch, every few days, between 3 different 6-station chains which provide symmetric coverage in the UV (Fourier) plane without moving any telescopes, only by moving beam relay mirrors. The 6-station chains are important to achieve the highest imaging resolution, and switching rapidly between station chains provides uniform coverage. Coherent integration techniques can be used to obtain good SNR on very small visibilities. Coherently integrated visibilities can be used for imaging with standard radio imaging packages such as AIPS. The commissioning of one additional station, the use of new data acquisition hardware and fringe tracking algorithms are the enhancements which make this project possible.

  15. Validation of MODIS aerosol optical depth over the Mediterranean Coast

    NASA Astrophysics Data System (ADS)

    Díaz-Martínez, J. Vicente; Segura, Sara; Estellés, Víctor; Utrillas, M. Pilar; Martínez-Lozano, J. Antonio

    2013-04-01

    Atmospheric aerosols, due to their high spatial and temporal variability, are considered one of the largest sources of uncertainty in different processes affecting visibility, air quality, human health, and climate. Among their effects on climate, they play an important role in the energy balance of the Earth. On one hand they have a direct effect by scattering and absorbing solar radiation; on the other, they also have an impact in precipitation, modifying clouds, or affecting air quality. The application of remote sensing techniques to investigate aerosol effects on climate has advanced significatively over last years. In this work, the products employed have been obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS is a sensor located onboard both Earth Observing Systems (EOS) Terra and Aqua satellites, which provide almost complete global coverage every day. These satellites have been acquiring data since early 2000 (Terra) and mid 2002 (Aqua) and offer different products for land, ocean and atmosphere. Atmospheric aerosol products are presented as level 2 products with a pixel size of 10 x 10 km2 in nadir. MODIS aerosol optical depth (AOD) is retrieved by different algorithms depending on the pixel surface, distinguishing between land and ocean. For its validation, ground based sunphotometer data from AERONET (Aerosol Robotic Network) has been employed. AERONET is an international operative network of Cimel CE318 sky-sunphotometers that provides the most extensive aerosol data base globally available of ground-based measurements. The ground sunphotometric technique is considered the most accurate for the retrieval of radiative properties of aerosols in the atmospheric column. In this study we present a validation of MODIS C051 AOD employing AERONET measurements over different Mediterranean coastal sites centered over an area of 50 x 50 km2, which includes both pixels over land and ocean. The validation is done comparing spatial

  16. Underwater optical wireless communications: depth dependent variations in attenuation.

    PubMed

    Johnson, Laura J; Green, Roger J; Leeson, Mark S

    2013-11-20

    Depth variations in the attenuation coefficient for light in the ocean were calculated using a one-parameter model based on the chlorophyll-a concentration C(c) and experimentally-determined Gaussian chlorophyll-depth profiles. The depth profiles were related to surface chlorophyll levels for the range 0-4  mg/m², representing clear, open ocean. The depth where C(c) became negligible was calculated to be shallower for places of high surface chlorophyll; 111.5 m for surface chlorophyll 0.8depth is the absolute minimum attenuation for underwater ocean communication links, calculated to be 0.0092  m⁻¹ at a wavelength of 430 nm. By combining this with satellite surface-chlorophyll data, it is possible to quantify the attenuation between any two locations in the ocean, with applications for low-noise or secure underwater communications and vertical links from the ocean surface.

  17. Estimating nocturnal opaque ice cloud optical depth from MODIS multispectral infrared radiances using a neural network method

    NASA Astrophysics Data System (ADS)

    Minnis, Patrick; Hong, Gang; Sun-Mack, Szedung; Smith, William L.; Chen, Yan; Miller, Steven D.

    2016-05-01

    Retrieval of ice cloud properties using IR measurements has a distinct advantage over the visible and near-IR techniques by providing consistent monitoring regardless of solar illumination conditions. Historically, the IR bands at 3.7, 6.7, 11.0, and 12.0 µm have been used to infer ice cloud parameters by various methods, but the reliable retrieval of ice cloud optical depth τ is limited to nonopaque cirrus with τ < 8. The Ice Cloud Optical Depth from Infrared using a Neural network (ICODIN) method is developed in this paper by training Moderate Resolution Imaging Spectroradiometer (MODIS) radiances at 3.7, 6.7, 11.0, and 12.0 µm against CloudSat-estimated τ during the nighttime using 2 months of matched global data from 2007. An independent data set comprising observations from the same 2 months of 2008 was used to validate the ICODIN. One 4-channel and three 3-channel versions of the ICODIN were tested. The training and validation results show that IR channels can be used to estimate ice cloud τ up to 150 with correlations above 78% and 69% for all clouds and only opaque ice clouds, respectively. However, τ for the deepest clouds is still underestimated in many instances. The corresponding RMS differences relative to CloudSat are ~100 and ~72%. If the opaque clouds are properly identified with the IR methods, the RMS differences in the retrieved optical depths are ~62%. The 3.7 µm channel appears to be most sensitive to optical depth changes but is constrained by poor precision at low temperatures. A method for estimating total optical depth is explored for estimation of cloud water path in the future. Factors affecting the uncertainties and potential improvements are discussed. With improved techniques for discriminating between opaque and semitransparent ice clouds, the method can ultimately improve cloud property monitoring over the entire diurnal cycle.

  18. Application of simple all-sky imagers for the estimation of aerosol optical depth

    NASA Astrophysics Data System (ADS)

    Kazantzidis, Andreas; Tzoumanikas, Panagiotis; Nikitidou, Efterpi; Salamalikis, Vasileios; Wilbert, Stefan; Prahl, Christoph

    2017-06-01

    Aerosol optical depth is a key atmospheric constituent for direct normal irradiance calculations at concentrating solar power plants. However, aerosol optical depth is typically not measured at the solar plants for financial reasons. With the recent introduction of all-sky imagers for the nowcasting of direct normal irradiance at the plants a new instrument is available which can be used for the determination of aerosol optical depth at different wavelengths. In this study, we are based on Red, Green and Blue intensities/radiances and calculations of the saturated area around the Sun, both derived from all-sky images taken with a low-cost surveillance camera at the Plataforma Solar de Almeria, Spain. The aerosol optical depth at 440, 500 and 675nm is calculated. The results are compared with collocated aerosol optical measurements and the mean/median difference and standard deviation are less than 0.01 and 0.03 respectively at all wavelengths.

  19. A method to improve accuracy and precision of water surface identification for photon depth dose measurementsa)

    PubMed Central

    Ververs, J. D.; Schaefer, M. J.; Kawrakow, I.; Siebers, J. V.

    2009-01-01

    The objective of this study is to present a method to reduce the setup error inherent in clinical depth dose measurements and, in doing so, to improve entrance dosimetry measurement reliability. Ionization chamber (IC) depth dose measurements are acquired with the depth scan extended into the air above the water surface. An inflection region is obtained in each resulting percent depth ionization (PDI) curve that can be matched against other measurements or to an inflection region obtained from an analogous Monte Carlo (MC) simulation. Measurements are made with various field sizes for the 6 and 18MV photon beams, with and without a Pb foil in the beam, to determine the sensitivity of the dose inflection region to the beam conditions. The offset between reference and test data set inflection regions is quantified using two separate methods. When comparing sets of measured data, maxima in the second derivative of ionization are compared. When comparing measured data to MC simulation, the offset that minimizes the sum of squared differences between the reference and test curves in the ionization inflection region is found. These methods can be used to quantify the offset between an initial setup (test) position and the true surface (reference) position. The ionization inflection location is found to be insensitive to changes in field size, electron contamination, and beam energy. Data from a single reference condition should be sufficient to identify the surface location. The method of determining IC offsets is general and should be applicable to any IC and other radiation sources. The measurement method could reduce the time and effort required in the initial IC setup at a water surface as setup errors can be corrected offline. Given a reliable set of reference data to compare with, this method could increase the ability of quality assurance (QA) measurements to detect discrepancies in beam output as opposed to discrepancies in IC localization. Application of the

  20. Impact of simulated three-dimensional perception on precision of depth judgements, technical performance and perceived workload in laparoscopy.

    PubMed

    Sakata, S; Grove, P M; Hill, A; Watson, M O; Stevenson, A R L

    2017-07-01

    This study compared precision of depth judgements, technical performance and workload using two-dimensional (2D) and three-dimensional (3D) laparoscopic displays across different viewing distances. It also compared the accuracy of 3D displays with natural viewing, along with the relationship between stereoacuity and 3D laparoscopic performance. A counterbalanced within-subjects design with random assignment to testing sequences was used. The system could display 2D or 3D images with the same set-up. A Howard-Dolman apparatus assessed precision of depth judgements, and three laparoscopic tasks (peg transfer, navigation in space and suturing) assessed performance (time to completion). Participants completed tasks in all combinations of two viewing modes (2D, 3D) and two viewing distances (1 m, 3 m). Other measures administered included the National Aeronautics and Space Administration Task Load Index (perceived workload) and the Randot(®) Stereotest (stereoacuity). Depth judgements were 6·2 times as precise at 1 m and 3·0 times as precise at 3 m using 3D versus 2D displays (P < 0·001). Participants performed all laparoscopic tasks faster in 3D at both 1 and 3 m (P < 0.001), with mean completion times up to 64 per cent shorter for 3D versus 2D displays. Workload was lower for 3D displays (up to 34 per cent) than for 2D displays at both viewing distances (P < 0·001). Greater viewing distance inhibited performance for two laparoscopic tasks, and increased perceived workload for all three (P < 0·001). Higher stereoacuity was associated with shorter completion times for the navigating in space task performed in 3D at 1 m (r = - 0·40, P = 0·001). 3D displays offer large improvements over 2D displays in precision of depth judgements, technical performance and perceived workload. © 2017 The Authors. BJS published by John Wiley & Sons Ltd on behalf of BJS Society Ltd.

  1. Some relationships between Secchi depth and inherent optical properties of natural waters

    NASA Technical Reports Server (NTRS)

    Gordon, H. R.; Wouters, A. W.

    1978-01-01

    Relationships between the inherent and optical properties of the ocean (Gorden et al., 1975 and Preisendorfer, 1961) are combined with the Duntley-Preisendorfer equation to show the dependence of these properties on the depth at which a Secchi disk disappears from view. An expression relating the Secchi depth to the limiting contrast of the disk is derived in terms of the average beam attenuation coefficient, the average diffuse attenuation coefficient for downwelling irradiance, the albedo of the disk, and the reflectance functions at the Secchi depth and just below the surface. It is shown that combining Secchi depth observations with other optical properties yields significant information about the constituents of the medium.

  2. Egocentric Depth Judgements in Optical, See-Through Augmented Reality

    DTIC Science & Technology

    2007-06-01

    order design that repeated modulo eight subjects. Within each environment protocol block, our control program generated a list of 3 ðdistanceÞ 4...pp. 15-19, 2006. [18] M.S. Landy, L.T. Maloney, E.B. Johnston, and M. Young , “Measurement and Modeling of Depth Cue Combination: In Defense of Weak

  3. Aerosol optical depth in clean marine and continental northeast Atlantic air

    NASA Astrophysics Data System (ADS)

    Mulcahy, J. P.; O'Dowd, C. D.; Jennings, S. G.

    2009-10-01

    The aerosol optical depth (AOD) and Ångström exponent for the period 2002-2004 is evaluated for clean marine and continentally influenced air masses over the northeast Atlantic region. Measurements were carried out at the Mace Head atmospheric research station on the west coast of Ireland using a precision filter radiometer which measures the aerosol optical depth at four wavelengths centered at 368, 412, 500, and 862 nm. The clean marine AOD at 500 nm is characterized by a mean value of 0.14 ± 0.06, exhibiting relatively small temporal variability. The Ångström exponent was less than 1 for the majority of cases, having an average value of 0.40 ± 0.29 in clean marine conditions. The latter is consistent with the presence of relatively large supermicron particles, such as sea salt dominating the marine aerosol size distribution. The Ångström exponent shows a distinct seasonal cycle in clean marine air, with maximum values being derived in the summer months and minimum values in the winter. In continental air masses, while the range and standard deviation of the AOD is larger than in clean marine conditions, the overall mean AOD (τ500 = 0.19 ± 0.12) is comparable with the clean marine AOD. The continental Ångström exponent is larger, having a mean value of 1.07 ± 0.32. This is attributed to a dominating accumulation mode in the presence of urban-industrial aerosol particles originating mainly from continental Europe. These results demonstrate how the natural marine AOD can rival polluted AOD over the northeast Atlantic region and highlight the importance of the natural marine aerosol contribution over oceans.

  4. Updating Mars-GRAM to Increase the Accuracy of Sensitivity Studies at Large Optical Depths

    NASA Technical Reports Server (NTRS)

    Justh, Hiliary L.; Justus, C. G.; Badger, Andrew M.

    2010-01-01

    The Mars Global Reference Atmospheric Model (Mars-GRAM) is an engineering-level atmospheric model widely used for diverse mission applications. Mars-GRAM s perturbation modeling capability is commonly used, in a Monte-Carlo mode, to perform high fidelity engineering end-to-end simulations for entry, descent, and landing (EDL). During the Mars Science Laboratory (MSL) site selection process, it was discovered that Mars-GRAM, when used for sensitivity studies for MapYear=0 and large optical depth values such as tau=3, is less than realistic. From the surface to 80 km altitude, Mars-GRAM is based on the NASA Ames Mars General Circulation Model (MGCM). MGCM results that were used for Mars-GRAM with MapYear set to 0 were from a MGCM run with a fixed value of tau=3 for the entire year at all locations. This has resulted in an imprecise atmospheric density at all altitudes. As a preliminary fix to this pressure-density problem, density factor values were determined for tau=0.3, 1 and 3 that will adjust the input values of MGCM MapYear 0 pressure and density to achieve a better match of Mars-GRAM MapYear 0 with Thermal Emission Spectrometer (TES) observations for MapYears 1 and 2 at comparable dust loading. Currently, these density factors are fixed values for all latitudes and Ls. Results will be presented from work being done to derive better multipliers by including variation with latitude and/or Ls by comparison of MapYear 0 output directly against TES limb data. The addition of these more precise density factors to Mars-GRAM 2005 Release 1.4 will improve the results of the sensitivity studies done for large optical depths.

  5. Depth-resolved photothermal optical coherence tomography by local optical path length change measurement (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Makita, Shuichi; Hong, Young-Joo; Li, En; Yasuno, Yoshiaki

    2016-03-01

    Photothermal OCT has been emerged to contrast absorbers in biological tissues. The tissues response to photothermal excitation as change of thermal strain and refractive index. To resolve the depth of absorption agents, the measurements of the local thermal strain change and local refractive index change due to photothermal effect is required. In this study, we developed photothermal OCT for depth-resolved absorption contrast imaging. The phase-resolved OCT can measure the axial strain change and local refractive index change as local optical path length change. A swept-source OCT system is used with a wavelength swept laser at 1310 nm with a scanning rate of 50 kHz. The sensitivity of 110 dB is achieved. At the sample arm, the excitation beam from a fiber-coupled laser diode of 406 nm wavelength is combined with the OCT probe beam co-linearly. The slowly modulated excitation beam around 300 Hz illuminate biological tissues. M-mode scan is applied during one-period modulation duration. The local optical path length change is measured by temporal and axial phase difference. The theoretical prediction of the photothermal response is derived and in good agreement with experimental results. In the case of slow modulation, the delay of photothermal response can be neglected. The local path length changes are averaged over the half period of the excitation modulation, and then demodulated. This method exhibits 3-dB gain in the sensitivity of the local optical path length change measurement over the direct Fourier transform method. In vivo human skin imaging of endogenous absorption agent will be demonstrated.

  6. Effect of Thin Cirrus Clouds on Dust Optical Depth Retrievals From MODIS Observations

    NASA Technical Reports Server (NTRS)

    Feng, Qian; Hsu, N. Christina; Yang, Ping; Tsay, Si-Chee

    2011-01-01

    The effect of thin cirrus clouds in retrieving the dust optical depth from MODIS observations is investigated by using a simplified aerosol retrieval algorithm based on the principles of the Deep Blue aerosol property retrieval method. Specifically, the errors of the retrieved dust optical depth due to thin cirrus contamination are quantified through the comparison of two retrievals by assuming dust-only atmospheres and the counterparts with overlapping mineral dust and thin cirrus clouds. To account for the effect of the polarization state of radiation field on radiance simulation, a vector radiative transfer model is used to generate the lookup tables. In the forward radiative transfer simulations involved in generating the lookup tables, the Rayleigh scattering by atmospheric gaseous molecules and the reflection of the surface assumed to be Lambertian are fully taken into account. Additionally, the spheroid model is utilized to account for the nonsphericity of dust particles In computing their optical properties. For simplicity, the single-scattering albedo, scattering phase matrix, and optical depth are specified a priori for thin cirrus clouds assumed to consist of droxtal ice crystals. The present results indicate that the errors in the retrieved dust optical depths due to the contamination of thin cirrus clouds depend on the scattering angle, underlying surface reflectance, and dust optical depth. Under heavy dusty conditions, the absolute errors are comparable to the predescribed optical depths of thin cirrus clouds.

  7. Effect of Thin Cirrus Clouds on Dust Optical Depth Retrievals From MODIS Observations

    NASA Technical Reports Server (NTRS)

    Feng, Qian; Hsu, N. Christina; Yang, Ping; Tsay, Si-Chee

    2011-01-01

    The effect of thin cirrus clouds in retrieving the dust optical depth from MODIS observations is investigated by using a simplified aerosol retrieval algorithm based on the principles of the Deep Blue aerosol property retrieval method. Specifically, the errors of the retrieved dust optical depth due to thin cirrus contamination are quantified through the comparison of two retrievals by assuming dust-only atmospheres and the counterparts with overlapping mineral dust and thin cirrus clouds. To account for the effect of the polarization state of radiation field on radiance simulation, a vector radiative transfer model is used to generate the lookup tables. In the forward radiative transfer simulations involved in generating the lookup tables, the Rayleigh scattering by atmospheric gaseous molecules and the reflection of the surface assumed to be Lambertian are fully taken into account. Additionally, the spheroid model is utilized to account for the nonsphericity of dust particles In computing their optical properties. For simplicity, the single-scattering albedo, scattering phase matrix, and optical depth are specified a priori for thin cirrus clouds assumed to consist of droxtal ice crystals. The present results indicate that the errors in the retrieved dust optical depths due to the contamination of thin cirrus clouds depend on the scattering angle, underlying surface reflectance, and dust optical depth. Under heavy dusty conditions, the absolute errors are comparable to the predescribed optical depths of thin cirrus clouds.

  8. Towards the development of a 30 year record of remotely sensed vegetation optical depth

    NASA Astrophysics Data System (ADS)

    de Jeu, Richard A. M.; Holmes, Thomas R. H.; van der Werf, Guido

    2009-09-01

    The framework for the development of a 30 year global record of remotely sensed vegetation optical depth is presented. The vegetation data set is derived from passive microwave observations and spans the period from November 1978 through the end of 2008. Different satellite sensor observations (i.e. Nimbus-7 SMMR, DMSP SSM/I, TRMM TMI, and AQUA AMSR-E). are used in a radiative transfer model to derive vegetation optical depth. Vegetation optical depth can directly be related to vegetation water content and is a function of biomass. The retrieval model is described and the quality of the retrieved vegetation optical depth is discussed. The new dataset will be merged into one consistent global product for the entire period of data record. To explore the potential to use this new product for long term vegetation modeling, the product was compared to total biomass from the biogeochemical model CASA. The results indicate that the vegetation optical depth can be an important contribution to the derivation of biophysical properties like biomass. It can also increase the reliability of optical sensor derived vegetation indices, because the microwave vegetation optical depth can be derived under cloudy conditions. This unique feature could create the possibility to improve the temporal resolution of other biophysical data products. The entire vegetation density dataset will be made available for download by the general science community and could give a significant contribution in climate research.

  9. Micro-optical system based 3D imaging for full HD depth image capturing

    NASA Astrophysics Data System (ADS)

    Park, Yong-Hwa; Cho, Yong-Chul; You, Jang-Woo; Park, Chang-Young; Yoon, Heesun; Lee, Sang-Hun; Kwon, Jong-Oh; Lee, Seung-Wan

    2012-03-01

    20 Mega-Hertz-switching high speed image shutter device for 3D image capturing and its application to system prototype are presented. For 3D image capturing, the system utilizes Time-of-Flight (TOF) principle by means of 20MHz high-speed micro-optical image modulator, so called 'optical shutter'. The high speed image modulation is obtained using the electro-optic operation of the multi-layer stacked structure having diffractive mirrors and optical resonance cavity which maximizes the magnitude of optical modulation. The optical shutter device is specially designed and fabricated realizing low resistance-capacitance cell structures having small RC-time constant. The optical shutter is positioned in front of a standard high resolution CMOS image sensor and modulates the IR image reflected from the object to capture a depth image. Suggested novel optical shutter device enables capturing of a full HD depth image with depth accuracy of mm-scale, which is the largest depth image resolution among the-state-of-the-arts, which have been limited up to VGA. The 3D camera prototype realizes color/depth concurrent sensing optical architecture to capture 14Mp color and full HD depth images, simultaneously. The resulting high definition color/depth image and its capturing device have crucial impact on 3D business eco-system in IT industry especially as 3D image sensing means in the fields of 3D camera, gesture recognition, user interface, and 3D display. This paper presents MEMS-based optical shutter design, fabrication, characterization, 3D camera system prototype and image test results.

  10. Optical transfer of master hologram with 20-meter depth

    NASA Astrophysics Data System (ADS)

    Jepsen, Mary Lou; Dawson, Paula H.

    1993-03-01

    The optical transfer of a large-scale synthetic holographic master stereogram via Benton rainbow technique is discussed. The limits of this technique when the volume the rainbow hologram fills is increased to 8000 cubic meters are evaluated. Blur and accommodation present the primary difficulties. The choice of imagery plays a crucial role in minimizing these effects.

  11. Precision Control of Ultracold Molecules in Optical Lattices

    DTIC Science & Technology

    2011-07-20

    control and precision. For example, a Stark-cancellation, or magic frequency , technique has enabled state-of-the-art neutral atom clocks. This approach...NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON a. REPORT b. ABSTRACT c. THIS PAGE 17. LIMITATION OF ABSTRACT Standard Form 298...precision frequency measurements with the goal to find evidence for a possible time variation of the electron-proton mass ratio. The proposal also included

  12. Retrieval of the optical depth using an all-sky CCD camera.

    PubMed

    Olmo, Francisco J; Cazorla, Alberto; Alados-Arboledas, Lucas; López-Alvarez, Miguel A; Hernández-Andrés, Javier; Romero, Javier

    2008-12-01

    A new method is presented for retrieval of the aerosol and cloud optical depth using a CCD camera equipped with a fish-eye lens (all-sky imager system). In a first step, the proposed method retrieves the spectral radiance from sky images acquired by the all-sky imager system using a linear pseudoinverse algorithm. Then, the aerosol or cloud optical depth at 500 nm is obtained as that which minimizes the residuals between the zenith spectral radiance retrieved from the sky images and that estimated by the radiative transfer code. The method is tested under extreme situations including the presence of nonspherical aerosol particles. The comparison of optical depths derived from the all-sky imager with those retrieved with a sunphotometer operated side by side shows differences similar to the nominal error claimed in the aerosol optical depth retrievals from sunphotometer networks.

  13. A COMPARISON OF AEROSOL OPTICAL DEPTH SIMULATED USING CMAQ WITH SATELLITE ESTIMATES

    EPA Science Inventory

    Satellite data provide new opportunities to study the regional distribution of particulate matter. The aerosol optical depth (AOD) - a derived estimate from the satellite measured irradiance, can be compared against model derived estimate to provide an evaluation of the columnar ...

  14. Temporal variations in atmospheric water vapor and aerosol optical depth determined by remote sensing

    NASA Technical Reports Server (NTRS)

    Pitts, D. E.; Mcallum, W. E.; Heidt, M.; Jeske, K.; Lee, J. T.; Demonbrun, D.; Morgan, A.; Potter, J.

    1977-01-01

    By automatically tracking the sun, a four-channel solar radiometer was used to continuously measure optical depth and atmospheric water vapor. The design of this simple autotracking solar radiometer is presented. A technique for calculating the precipitable water from the ratio of a water band to a nearby nonabsorbing band is discussed. Studies of the temporal variability of precipitable water and atmospheric optical depth at 0.610, 0.8730 and 1.04 microns are presented. There was good correlation between the optical depth measured using the autotracker and visibility determined from National Weather Service Station data. However, much more temporal structure was evident in the autotracker data than in the visibility data. Cirrus clouds caused large changes in optical depth over short time periods. They appear to be the largest deleterious atmospheric effect over agricultural areas that are remote from urban pollution sources.

  15. A COMPARISON OF AEROSOL OPTICAL DEPTH SIMULATED USING CMAQ WITH SATELLITE ESTIMATES

    EPA Science Inventory

    Satellite data provide new opportunities to study the regional distribution of particulate matter. The aerosol optical depth (AOD) - a derived estimate from the satellite measured irradiance, can be compared against model derived estimate to provide an evaluation of the columnar ...

  16. Temporal variations in atmospheric water vapor and aerosol optical depth determined by remote sensing

    NASA Technical Reports Server (NTRS)

    Pitts, D. E.; Mcallum, W. E.; Heidt, M.; Jeske, K.; Lee, J. T.; Demonbrun, D.; Morgan, A.; Potter, J.

    1977-01-01

    By automatically tracking the sun, a four-channel solar radiometer was used to continuously measure optical depth and atmospheric water vapor. The design of this simple autotracking solar radiometer is presented. A technique for calculating the precipitable water from the ratio of a water band to a nearby nonabsorbing band is discussed. Studies of the temporal variability of precipitable water and atmospheric optical depth at 0.610, 0.8730 and 1.04 microns are presented. There was good correlation between the optical depth measured using the autotracker and visibility determined from National Weather Service Station data. However, much more temporal structure was evident in the autotracker data than in the visibility data. Cirrus clouds caused large changes in optical depth over short time periods. They appear to be the largest deleterious atmospheric effect over agricultural areas that are remote from urban pollution sources.

  17. Constraining the low-cloud optical depth feedback at middle and high latitudes using satellite observations

    SciTech Connect

    Terai, C. R.; Klein, S. A.; Zelinka, M. D.

    2016-08-26

    The increase in cloud optical depth with warming at middle and high latitudes is a robust cloud feedback response found across all climate models. This study builds on results that suggest the optical depth response to temperature is timescale invariant for low-level clouds. The timescale invariance allows one to use satellite observations to constrain the models' optical depth feedbacks. Three passive-sensor satellite retrievals are compared against simulations from eight models from the Atmosphere Model Intercomparison Project (AMIP) of the 5th Coupled Model Intercomparison Project (CMIP5). This study confirms that the low-cloud optical depth response is timescale invariant in the AMIP simulations, generally at latitudes higher than 40°. Compared to satellite estimates, most models overestimate the increase in optical depth with warming at the monthly and interannual timescales. Many models also do not capture the increase in optical depth with estimated inversion strength that is found in all three satellite observations and in previous studies. The discrepancy between models and satellites exists in both hemispheres and in most months of the year. A simple replacement of the models' optical depth sensitivities with the satellites' sensitivities reduces the negative shortwave cloud feedback by at least 50% in the 40°–70°S latitude band and by at least 65% in the 40°–70°N latitude band. Furthermore, based on this analysis of satellite observations, we conclude that the low-cloud optical depth feedback at middle and high latitudes is likely too negative in climate models.

  18. Anomalous Dispersion in Gases Derived from the Optical Depth. Theoretical Treatment: Line by Line Calculations

    DTIC Science & Technology

    1991-06-28

    AD-A238 853 ANOMALOUS DISPERSION IN GASES DERIVED FROM THE OPTICAL DEPTH. THEORETICAL TREATMENT; LINE BY LINE CALCULATIONS BY EGIL BINGEN . BJ0RNAR...06054 917 1 04 ANOMALOUS DISPERSION IN GASES DERIVED FROM THE OPTICAL DEPTH. THEORETICAL TREATMENT; LINE BY LINE CALCULATIONS by - EGII, BINGEN . BJORNAR... BINGEN Egil, YSTAD Bjornar 61 DISTRIBUTION STATEMENT Approved for pub’ic release. Distribution unlimited (Offentlig tilgjengelig) 7) INDEXING TERMS IN

  19. Constraining the low-cloud optical depth feedback at middle and high latitudes using satellite observations

    DOE PAGES

    Terai, C. R.; Klein, S. A.; Zelinka, M. D.

    2016-08-26

    The increase in cloud optical depth with warming at middle and high latitudes is a robust cloud feedback response found across all climate models. This study builds on results that suggest the optical depth response to temperature is timescale invariant for low-level clouds. The timescale invariance allows one to use satellite observations to constrain the models' optical depth feedbacks. Three passive-sensor satellite retrievals are compared against simulations from eight models from the Atmosphere Model Intercomparison Project (AMIP) of the 5th Coupled Model Intercomparison Project (CMIP5). This study confirms that the low-cloud optical depth response is timescale invariant in the AMIPmore » simulations, generally at latitudes higher than 40°. Compared to satellite estimates, most models overestimate the increase in optical depth with warming at the monthly and interannual timescales. Many models also do not capture the increase in optical depth with estimated inversion strength that is found in all three satellite observations and in previous studies. The discrepancy between models and satellites exists in both hemispheres and in most months of the year. A simple replacement of the models' optical depth sensitivities with the satellites' sensitivities reduces the negative shortwave cloud feedback by at least 50% in the 40°–70°S latitude band and by at least 65% in the 40°–70°N latitude band. Furthermore, based on this analysis of satellite observations, we conclude that the low-cloud optical depth feedback at middle and high latitudes is likely too negative in climate models.« less

  20. Constraining the low-cloud optical depth feedback at middle and high latitudes using satellite observations

    SciTech Connect

    Terai, C. R.; Klein, S. A.; Zelinka, M. D.

    2016-08-26

    The increase in cloud optical depth with warming at middle and high latitudes is a robust cloud feedback response found across all climate models. This study builds on results that suggest the optical depth response to temperature is timescale invariant for low-level clouds. The timescale invariance allows one to use satellite observations to constrain the models' optical depth feedbacks. Three passive-sensor satellite retrievals are compared against simulations from eight models from the Atmosphere Model Intercomparison Project (AMIP) of the 5th Coupled Model Intercomparison Project (CMIP5). This study confirms that the low-cloud optical depth response is timescale invariant in the AMIP simulations, generally at latitudes higher than 40°. Compared to satellite estimates, most models overestimate the increase in optical depth with warming at the monthly and interannual timescales. Many models also do not capture the increase in optical depth with estimated inversion strength that is found in all three satellite observations and in previous studies. The discrepancy between models and satellites exists in both hemispheres and in most months of the year. A simple replacement of the models' optical depth sensitivities with the satellites' sensitivities reduces the negative shortwave cloud feedback by at least 50% in the 40°–70°S latitude band and by at least 65% in the 40°–70°N latitude band. Furthermore, based on this analysis of satellite observations, we conclude that the low-cloud optical depth feedback at middle and high latitudes is likely too negative in climate models.

  1. Measurements of the thermal coefficient of optical attenuation at different depth regions of in vivo human skins using optical coherence tomography: a pilot study.

    PubMed

    Su, Ya; Yao, X Steve; Li, Zhihong; Meng, Zhuo; Liu, Tiegen; Wang, Longzhi

    2015-02-01

    We present detailed measurement results of optical attenuation's thermal coefficients (referenced to the temperature of the skin surface) in different depth regions of in vivo human forearm skins using optical coherence tomography (OCT). We first design a temperature control module with an integrated optical probe to precisely control the surface temperature of a section of human skin. We propose a method of using the correlation map to identify regions in the skin having strong correlations with the surface temperature of the skin and find that the attenuation coefficient in these regions closely follows the variation of the surface temperature without any hysteresis. We observe a negative thermal coefficient of attenuation in the epidermis. While in dermis, the slope signs of the thermal coefficient of attenuation are different at different depth regions for a particular subject, however, the depth regions with a positive (or negative) slope are different in different subjects. We further find that the magnitude of the thermal coefficient of attenuation coefficient is greater in epidermis than in dermis. We believe the knowledge of such thermal properties of skins is important for several noninvasive diagnostic applications, such as OCT glucose monitoring, and the method demonstrated in this paper is effective in studying the optical and biological properties in different regions of skin.

  2. Measurements of the thermal coefficient of optical attenuation at different depth regions of in vivo human skins using optical coherence tomography: a pilot study

    PubMed Central

    Su, Ya; Yao, X. Steve; Li, Zhihong; Meng, Zhuo; Liu, Tiegen; Wang, Longzhi

    2015-01-01

    We present detailed measurement results of optical attenuation’s thermal coefficients (referenced to the temperature of the skin surface) in different depth regions of in vivo human forearm skins using optical coherence tomography (OCT). We first design a temperature control module with an integrated optical probe to precisely control the surface temperature of a section of human skin. We propose a method of using the correlation map to identify regions in the skin having strong correlations with the surface temperature of the skin and find that the attenuation coefficient in these regions closely follows the variation of the surface temperature without any hysteresis. We observe a negative thermal coefficient of attenuation in the epidermis. While in dermis, the slope signs of the thermal coefficient of attenuation are different at different depth regions for a particular subject, however, the depth regions with a positive (or negative) slope are different in different subjects. We further find that the magnitude of the thermal coefficient of attenuation coefficient is greater in epidermis than in dermis. We believe the knowledge of such thermal properties of skins is important for several noninvasive diagnostic applications, such as OCT glucose monitoring, and the method demonstrated in this paper is effective in studying the optical and biological properties in different regions of skin. PMID:25780740

  3. In-process optical metrology for precision machining

    SciTech Connect

    Langenbeck, P.

    1987-01-01

    This book contains papers divided among the following sections: Optical technology in the Netherlands; Shape and microfinish as a function of machine performance and stiffness; Repsonse of material to ideal micromachining and diamond tools; Micromachined components in optical systems, scanning interferometry; Contactless microtopography and profilometry; and Automated interferometric validation scatterometry, ellipsometry.

  4. Optical and thermal depth profile reconstructions of inhomogeneous photopolymerization in dental resins using photothermal waves

    NASA Astrophysics Data System (ADS)

    Martínez-Torres, P.; Mandelis, A.; Alvarado-Gil, J. J.

    2010-09-01

    Photopolymerization is a process that depends, among other factors, on the optical properties of polymerized materials. In turn, this process affects longitudinal light transport in these materials, thereby altering their optical absorption coefficient which is thus expected to exhibit depth dependence. Furthermore, polymerization affects the thermal properties of these materials. A robust theoretical approach to the study of the depth-dependent optical absorption coefficient, β(x ), and thermal diffusivity, α(x ), in materials exhibiting depth profiles of these parameters has been developed through the photothermal inverse problem based on the concept of the thermal-harmonic oscillator. Using this concept in the frequency-domain nonhomogeneous photothermal-wave boundary-value problem, the simultaneous reconstruction of arbitrary simultaneous optical and thermal depth profiles was achieved using a multiparameter fitting method to the experimental amplitude and phase. As a first application of the theory to partially polymerized Alert Composite (shade A3) dental resin, with curing induced by a blue light-emitting diode, the β(x ) and α(x ) depth profiles were reconstructed from photothermal radiometric frequency-scanned data. A strong anticorrelation of these two depth profiles was observed and was interpreted in terms of photochemical processes occurring during the optical (photocuring) creation of long polymeric chains in the resin. The photothermally reconstructed depth profiles may have implications for the optimization of blue light curing methods using such resins in dental clinical practice.

  5. Measuring fast optical depth variations in cloud edges with a CCD-array spectrometer

    NASA Astrophysics Data System (ADS)

    González, Josep-Abel; Calbó, Josep; Sanchez-Romero, Alejandro

    2017-02-01

    High frequency measurements of direct solar flux have been performed with a CCD spectrometer in six narrowband channels along the visible range. Measurements were performed in 1-sec intervals for conditions ranging from clear sky to scattered-to-broken cloud fields. The comparison between close time measurements allows obtaining information on the fast changes in optical depth associated to the pass of clouds or other changes in atmospheric conditions and constituents. The method used does not depend on the absolute calibration of the instrument, and minimizes the effects of changes in instrumental conditions (as temperature) and in air mass. The variations in optical depth in the sight direction can be associated to cloud and/or aerosol optical depth, provided that other atmospheric constituents, as ozone, remain constant. The aerosol exponent is used to characterize the spectral dependence of the changes in optical depth and for describing the evolution of the conglomerate of particles (either cloud droplets or aerosol particles) along the measurement periods. We found that rates in optical depth variations above 0.1/sec have to be attributed to sunlight occultation by cloud edges, as the spectral exponent drops to values near zero or even slightly negative. Variations in optical depth at rates below 0.01/sec are mainly related to aerosol effects.

  6. Distributed optical multiplexing with precise frequency allocation using fiber frequency conversion

    NASA Astrophysics Data System (ADS)

    Kato, Tomoyuki; Okabe, Ryo; Watanabe, Shigeki

    2013-12-01

    Effective utilization of fiber capacity in optical communication networks is required to keep up with the increasing traffic demand. Precise optical frequency allocation among carriers is essential for improving the spectral efficiency to utilize the limited spectral resource. In this paper, we show a distributed optical multiplexing scheme, in which data signals are sequentially multiplexed by frequency-division multiplexing on a single-wavelength optical carrier using fiber frequency conversion with locally provided optical subcarrier signals. The scheme achieves dense packing of distributed multi-channel signals with precise frequency allocation using free-running lasers. Using the scheme we demonstrate a precise multiplexing of coherent-optical orthogonal frequency-division multiplexing and Nyquist wavelength-division multiplexing.

  7. High-precision steering of multipleholographic optical traps

    NASA Astrophysics Data System (ADS)

    Schmitz, Christian H. J.; Spatz, Joachim P.; Curtis, Jennifer E.

    2005-10-01

    Locating and steering entire ensembles of microscopic objects has become extremely practical with the emergence of holographic optical tweezers. Application of this technology to single molecule experiments requires great accuracy in the spatial positioning of optical traps. This paper calculates the theoretical position resolution of a single holographic beam, predicting that sub-nanometer resolution is easily achieved. Experimental corroboration of the spatial resolution's inverse dependence on the hologram's number of pixels and phase levels is presented. To at least a nanometer range position resolution, multiple optical tweezers created by complex superposition holograms also follow the theoretical predictions for a single beam.

  8. Method for making precisely configured flakes useful in optical devices

    DOEpatents

    Trajkovska-Petkoska, Anka; Jacobs, Stephen D.; Kosc, Tanya Z.; Marshall, Kenneth L.

    2007-07-03

    Precisely configured, especially of geometric shape, flakes of liquid crystal material are made using a mechanically flexible polymer mold with wells having shapes which are precisely configured by making the mold with a photolithographically manufactured or laser printed master. The polymer liquid crystal is poured into the wells in the flexible mold. When the liquid crystal material has solidified, the flexible mold is bent and the flakes are released and collected for use in making an electrooptical cell utilizing the liquid crystal flakes as the active element therein.

  9. Ultrabroadband optical chirp linearization for precision metrology applications.

    PubMed

    Roos, Peter A; Reibel, Randy R; Berg, Trenton; Kaylor, Brant; Barber, Zeb W; Babbitt, Wm Randall

    2009-12-01

    We demonstrate precise linearization of ultrabroadband laser frequency chirps via a fiber-based self-heterodyne technique to enable extremely high-resolution, frequency-modulated cw laser-radar (LADAR) and a wide range of other metrology applications. Our frequency chirps cover bandwidths up to nearly 5 THz with frequency errors as low as 170 kHz, relative to linearity. We show that this performance enables 31-mum transform-limited LADAR range resolution (FWHM) and 86 nm range precisions over a 1.5 m range baseline. Much longer range baselines are possible but are limited by atmospheric turbulence and fiber dispersion.

  10. Post-depositional remanent magnetization lock-in depth in precisely dated varved sediments assessed by archaeomagnetic field models

    NASA Astrophysics Data System (ADS)

    Mellström, Anette; Nilsson, Andreas; Stanton, Tania; Muscheler, Raimund; Snowball, Ian; Suttie, Neil

    2015-01-01

    Accurate and precise chronologies are needed to evaluate the existence and effect of a post-depositional remanent magnetization lock-in process on sedimentary palaeomagnetic records. Here we present lock-in modelling results of two palaeomagnetic records from varved lake sediments (lakes Kälksjön and Gyltigesjön) in Sweden by using model predictions based on archaeomagnetic data. We used the 14C wiggle-match dating technique to improve the precision of the Kälksjön varve chronology in the period between 3000 and 2000 cal BP, which is characterized by pronounced palaeomagnetic secular variation. This method allowed us to infer an age model with uncertainties of ±20 years (95.4% probability range). Furthermore, we compared the palaeomagnetic record of Kälksjön to Gyltigesjön, which has a corresponding 14C wiggle-matched chronology. The ages of palaeomagnetic features derived from the wiggle-matched varve chronologies are older than those predicted by the archaeomagnetic models. Lock-in modelling was performed with different filter functions to explain the temporal offset and the amplitude of the lake sediment palaeomagnetic data. The analyses suggest that a linear lock-in function with lock-in depths (the depth below which no more natural magnetic remanence is acquired) that range between 30 and 80 cm in Kälksjön and 50 and 160 cm in Gyltigesjön are most appropriate to explain the data. These relatively deep lock-in depths in sediments without a bioturbated 'mixed-zone' can be attributed to the relatively high organic contents and low density of the lake sediments, which contribute to a thick unconsolidated upper zone of the sediment sequence in which re-alignment of magnetic particles can take place.

  11. 3D elemental mapping with nanometer scale depth resolution via electron optical sectioning

    DOE PAGES

    Pennycook, Timothy J.; Yang, Hao; Jones, Lewys; ...

    2016-12-05

    Electron energy loss spectroscopy in the scanning transmission electron microscope has long been used to perform elemental mapping but has not previously exhibited depth sensitivity. The key to depth resolution with optical sectioning is the transfer of sufficiently high lateral spatial frequencies. By performing spectrum imaging with atomic resolution we achieve in this paper nanometer scale depth resolution, enabling us to optically section an oxide heterostructure spectroscopically. Finally, such 3D elemental mapping is sensitive to atomic scale changes in structure and composition and is more interpretable than Z-contrast imaging alone.

  12. Chromatic error correction of diffractive optical elements at minimum etch depths

    NASA Astrophysics Data System (ADS)

    Barth, Jochen; Gühne, Tobias

    2014-09-01

    The integration of diffractive optical elements (DOE) into an optical design opens up new possibilities for applications in sensing and illumination. If the resulting optics is used in a larger spectral range we must correct not only the chromatic error of the conventional, refractive, part of the design but also of the DOE. We present a simple but effective strategy to select substrates which allow the minimum etch depths for the DOEs. The selection depends on both the refractive index and the dispersion.

  13. Cloud Optical Depth Retrievals from Solar Background "signal" of Micropulse Lidars

    NASA Technical Reports Server (NTRS)

    Chiu, J. Christine; Marshak, A.; Wiscombe, W.; Valencia, S.; Welton, E. J.

    2007-01-01

    Pulsed lidars are commonly used to retrieve vertical distributions of cloud and aerosol layers. It is widely believed that lidar cloud retrievals (other than cloud base altitude) are limited to optically thin clouds. Here we demonstrate that lidars can retrieve optical depths of thick clouds using solar background light as a signal, rather than (as now) merely a noise to be subtracted. Validations against other instruments show that retrieved cloud optical depths agree within 10-15% for overcast stratus and broken clouds. In fact, for broken cloud situations one can retrieve not only the aerosol properties in clear-sky periods using lidar signals, but also the optical depth of thick clouds in cloudy periods using solar background signals. This indicates that, in general, it may be possible to retrieve both aerosol and cloud properties using a single lidar. Thus, lidar observations have great untapped potential to study interactions between clouds and aerosols.

  14. Cloud Optical Depth Measured with Ground-Based, Uncooled Infrared Imagers

    NASA Technical Reports Server (NTRS)

    Shaw, Joseph A.; Nugent, Paul W.; Pust, Nathan J.; Redman, Brian J.; Piazzolla, Sabino

    2012-01-01

    Recent advances in uncooled, low-cost, long-wave infrared imagers provide excellent opportunities for remotely deployed ground-based remote sensing systems. However, the use of these imagers in demanding atmospheric sensing applications requires that careful attention be paid to characterizing and calibrating the system. We have developed and are using several versions of the ground-based "Infrared Cloud Imager (ICI)" instrument to measure spatial and temporal statistics of clouds and cloud optical depth or attenuation for both climate research and Earth-space optical communications path characterization. In this paper we summarize the ICI instruments and calibration methodology, then show ICI-derived cloud optical depths that are validated using a dual-polarization cloud lidar system for thin clouds (optical depth of approximately 4 or less).

  15. Precision optical slit for high heat load or ultra high vacuum

    DOEpatents

    Andresen, N.C.; DiGennaro, R.S.; Swain, T.L.

    1995-01-24

    This invention relates generally to slits used in optics that must be precisely aligned and adjusted. The optical slits of the present invention are useful in x-ray optics, x-ray beam lines, optical systems in which the entrance slit is critical for high wavelength resolution. The invention is particularly useful in ultra high vacuum systems where lubricants are difficult to use and designs which avoid the movement of metal parts against one another are important, such as monochromators for high wavelength resolution with ultra high vacuum systems. The invention further relates to optical systems in which temperature characteristics of the slit materials is important. The present invention yet additionally relates to precision slits wherein the opposing edges of the slit must be precisely moved relative to a center line between the edges with each edge retaining its parallel orientation with respect to the other edge and/or the center line. 21 figures.

  16. Precision optical slit for high heat load or ultra high vacuum

    DOEpatents

    Andresen, Nord C.; DiGennaro, Richard S.; Swain, Thomas L.

    1995-01-01

    This invention relates generally to slits used in optics that must be precisely aligned and adjusted. The optical slits of the present invention are useful in x-ray optics, x-ray beam lines, optical systems in which the entrance slit is critical for high wavelength resolution. The invention is particularly useful in ultra high vacuum systems where lubricants are difficult to use and designs which avoid the movement of metal parts against one another are important, such as monochrometers for high wavelength resolution with ultra high vacuum systems. The invention further relates to optical systems in which temperature characteristics of the slit materials is important. The present invention yet additionally relates to precision slits wherein the opposing edges of the slit must be precisely moved relative to a center line between the edges with each edge retaining its parallel orientation with respect to the other edge and/or the center line.

  17. Challenges in mold manufacturing for high precision molded diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Pongs, Guido; Bresseler, Bernd; Schweizer, Klaus; Bergs, Thomas

    2016-09-01

    Isothermal precision glass molding of imaging optics is the key technology for mass production of precise optical elements. Especially for numerous consumer applications (e.g. digital cameras, smart phones, …), high precision glass molding is applied for the manufacturing of aspherical lenses. The usage of diffractive optical elements (DOEs) can help to further reduce the number of lenses in the optical systems which will lead to a reduced weight of hand-held optical devices. But today the application of molded glass DOEs is limited due to the technological challenges in structuring the mold surfaces. Depending on the application submicrometer structures are required on the mold surface. Furthermore these structures have to be replicated very precisely to the glass lens surface. Especially the micro structuring of hard and brittle mold materials such as Tungsten Carbide is very difficult and not established. Thus a multitude of innovative approaches using diffractive optical elements cannot be realized. Aixtooling has investigated in different mold materials and different suitable machining technologies for the micro- and sub-micrometer structuring of mold surfaces. The focus of the work lays on ultra-precision grinding to generate the diffractive pattern on the mold surfaces. This paper presents the latest achievements in diffractive structuring of Tungsten Carbide mold surfaces by ultra-precision grinding.

  18. Precise annealing of focal plane arrays for optical detection

    DOEpatents

    Bender, Daniel A.

    2015-09-22

    Precise annealing of identified defective regions of a Focal Plane Array ("FPA") (e.g., exclusive of non-defective regions of the FPA) facilitates removal of defects from an FPA that has been hybridized and/or packaged with readout electronics. Radiation is optionally applied under operating conditions, such as under cryogenic temperatures, such that performance of an FPA can be evaluated before, during, and after annealing without requiring thermal cycling.

  19. Precise evaluation of the Helmholtz equation for optical propagation.

    PubMed

    Pond, John E; Sutton, George W

    2015-01-01

    A precise computational integration of the Helmholtz equation was performed for laser propagation of an electromagnetic wave with no approximations or linearization. This computation integration was performed using 64-bit processors. This is illustrated for a uniform monochromatic beam from a circular aperture that has a uniform intensity. It predicts many Arago spots and near-field intensity fluctuations for a large ratio of aperture size to wavelength and converges to the usual Airy pattern in the far field.

  20. Precision optical metrology with alkali-atom isoclinic points

    NASA Astrophysics Data System (ADS)

    Wells, Nathan; Driskell, Travis; Camparo, James

    2016-06-01

    Vapour-phase spectroscopy rarely involves transitions between well-isolated atomic states. Routinely, the spectra comprise overlapped Doppler/pressure-broadened resonances, which leads to a “pulling” of the spectral peaks from their true atomic resonance frequencies. This pulling gives the absorption resonances a temperature sensitivity, which limits their utility for precision spectroscopy when sub-Doppler techniques are not viable. Here, we discuss the use of alkali isoclinic points as a solution to this problem.

  1. Insitu monitored engineering of inverted nanoporous anodic alumina funnels: on the precise generation of 3D optical nanostructures

    NASA Astrophysics Data System (ADS)

    Santos, Abel; Kumeria, Tushar; Wang, Ye; Losic, Dusan

    2014-08-01

    Herein, we present an innovative approach to generate a novel type of 3D optical nanostructures based on nanoporous anodic alumina (NAA), the so-called inverted nanoporous anodic alumina funnels (INAAFs). This electrochemical approach takes advantage of the differential dissolution rate of NAA with the annealing temperature, which enables the in-depth engineering of nanopores. The structural engineering of these 3D nanostructures is monitored in situ by reflectometric interference spectroscopy through changes in the effective optical thickness of NAA, making it possible to precisely control the formation of INAAFs in real-time. The resulting INAAFs are optical nanostructures featuring a stratified structure of well-defined cylindrical nanopores with increasing pore diameter from top to bottom. As a result of their geometric characteristics and optical properties, INAAFs are envisaged for replicating novel nanostructures and developing optical and photonic devices.Herein, we present an innovative approach to generate a novel type of 3D optical nanostructures based on nanoporous anodic alumina (NAA), the so-called inverted nanoporous anodic alumina funnels (INAAFs). This electrochemical approach takes advantage of the differential dissolution rate of NAA with the annealing temperature, which enables the in-depth engineering of nanopores. The structural engineering of these 3D nanostructures is monitored in situ by reflectometric interference spectroscopy through changes in the effective optical thickness of NAA, making it possible to precisely control the formation of INAAFs in real-time. The resulting INAAFs are optical nanostructures featuring a stratified structure of well-defined cylindrical nanopores with increasing pore diameter from top to bottom. As a result of their geometric characteristics and optical properties, INAAFs are envisaged for replicating novel nanostructures and developing optical and photonic devices. Electronic supplementary information (ESI

  2. Estimating vegetation optical depth using L-band passive microwave airborne data in HiWATER

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Chai, Linna

    2014-11-01

    In this study, a relationship between polarization differences of soil emissivity at different incidence angles was constructed from a large quantity of simulated soil emissivity based on the Advanced Integrated Emission Model (AIEM) input parameters include: a frequency of 1.4 GHz (L-band), incident angles varying from 1°to 60° at a 1° interval, a wide range of soil moisture content and land surface roughness parameters. Then, we used this relationship and the ω-τ zero-order radiation transfer model to develop an inversion method of low vegetation optical depth at L-band, this work were under the assumption that there was no significant polarization difference between the vegetation signals. Based on this inversion method of low vegetation optical depth, we used the land surface passive microwave brightness temperature of Heihe Watershed obtained by airborne Polarimetric L-band Multibeam Radiometer (PLMR) in 2012 Heihe Watershed Allied Telemetry Experimental Research (HiWATER) to retrieve the corn optical depth in the flight areas, then the results were compared with the measured corn LAI. Results show that the retrieved corn optical depths were consisted with the measured LAI of corn. It proved that the corn optical depth inversion method proposed in this study was feasible. Moreover, the method was promising to apply to the satellite observations.

  3. Precise digital demodulation for fiber optic interferometer sensors

    NASA Astrophysics Data System (ADS)

    Medvedev, Andrei; Berezhnoi, Andrei; Kudryashov, Aleksei; Liokumovich, Leonid

    2016-03-01

    Different methods are used in the interferometer sensors for target signal extraction. Digital technologies provide new opportunities for precise signal detection. We have developed the principle of signal demodulation using an additional harmonic phase modulation and digital signal processing. The principle allows implementation of processing algorithms using different ratios between modulation and discretization frequencies. The expressions allowing calculation of the phase difference using the inverse trigonometric functions were derived. The method was realized in LabVIEW programming environment and was demonstrated for various signal shapes.

  4. Fabrication of precision optics using an imbedded reference surface

    DOEpatents

    Folta, James A.; Spiller, Eberhard

    2005-02-01

    The figure of a substrate is very precisely measured and a figured-correcting layer is provided on the substrate. The thickness of the figure-correcting layer is locally measured and compared to the first measurement. The local measurement of the figure-correcting layer is accomplished through a variety of methods, including interferometry and fluorescence or ultrasound measurements. Adjustments in the thickness of the figure-correcting layer are made until the top of the figure-correcting layer matches a desired figure specification.

  5. MM&T: Precision Machining of Optical Components.

    DTIC Science & Technology

    1981-12-01

    Et TABLE OF CONTENTS Paragraph Title Page FOR EWORD 1.0 Task V I 1.1 Foreword 1 1.1.1 Initial Crew Training 1 1.1.2 Precision Machining Crew 1 1.2...GFP Training Machine 2 1.3 Part Fixturing 3 1.4 Chip Removal - Coolant Flow 4 1. 5 Part Quality Determinants 5 1.6 Part Quality 6 1.7 IntOp Aspherical...interim report covers the period of July 1980 to September 1981. A description of the personnel, machinery and results of the crew training program, a

  6. Improving Mars-GRAM: Increasing the Accuracy of Sensitivity Studies at Large Optical Depths

    NASA Technical Reports Server (NTRS)

    Justh, Hilary L.; Justus, C. G.; Badger, Andrew M.

    2010-01-01

    Extensively utilized for numerous mission applications, the Mars Global Reference Atmospheric Model (Mars-GRAM) is an engineering-level atmospheric model. In a Monte-Carlo mode, Mars-GRAM's perturbation modeling capability is used to perform high fidelity engineering end-to-end simulations for entry, descent, and landing (EDL). Mars-GRAM has been found to be inexact when used during the Mars Science Laboratory (MSL) site selection process for sensitivity studies for MapYear=0 and large optical depth values such as tau=3. Mars-GRAM is based on the NASA Ames Mars General Circulation Model (MGCM) from the surface to 80 km altitude. Mars-GRAM with the MapYear parameter set to 0 utilizes results from a MGCM run with a fixed value of tau=3 at all locations for the entire year. Imprecise atmospheric density and pressure at all altitudes is a consequence of this use of MGCM with tau=3. Density factor values have been determined for tau=0.3, 1 and 3 as a preliminary fix to this pressure-density problem. These factors adjust the input values of MGCM MapYear 0 pressure and density to achieve a better match of Mars-GRAM MapYear 0 with Thermal Emission Spectrometer (TES) observations for MapYears 1 and 2 at comparable dust loading. These density factors are fixed values for all latitudes and Ls and are included in Mars-GRAM Release 1.3. Work currently being done, to derive better multipliers by including variations with latitude and/or Ls by comparison of MapYear 0 output directly against TES limb data, will be highlighted in the presentation. The TES limb data utilized in this process has been validated by a comparison study between Mars atmospheric density estimates from Mars-GRAM and measurements by Mars Global Surveyor (MGS). This comparison study was undertaken for locations on Mars of varying latitudes, Ls, and LTST. The more precise density factors will be included in Mars-GRAM 2005 Release 1.4 and thus improve the results of future sensitivity studies done for large

  7. Precision Targeting With a Tracking Adaptive Optics Scanning Laser Ophthalmoscope

    DTIC Science & Technology

    2006-01-01

    galvanometers placed at appropriate conjugates within the path of the adaptive optics scanning laser ophthalmoscope. The input to the “master” control loop is...loop is the scaled position signals from the master galvanometers . The slave tracking mirrors are placed at conjugates to the center of rotation of the...slave systems), and analog-to-digital and digital-to- analog converters (ADC and DACs) to receive reflectometer signals and drive galvanometers . The

  8. Asian dust height and infrared optical depth retrievals over land from hyperspectral longwave infrared radiances

    NASA Astrophysics Data System (ADS)

    Yao, Zhigang; Li, Jun; Han, Hyo-Jin; Huang, Allen; Sohn, B. J.; Zhang, Peng

    2012-10-01

    The dust top height and infrared optical depth over land are retrieved from the Atmospheric Infrared Sounder (AIRS) longwave infrared measurements by using a one-dimensional-variation retrieval algorithm for different Asian dust storms. By combining particle size measurements from a 10-year ground observation data set from the Dunhuang Skynet station located to the east of the Taklimakan Desert in China and the Optical Properties of Aerosols and Clouds data set of optical properties, the mineral dust scattering and absorption coefficients are obtained and then used to compute brightness temperatures with RTTOV 9.3. The retrieved dust thermal infrared optical depths are compared with the Ozone Monitoring Instrument and Moderate Resolution Imaging Spectroradiometer (MODIS) products. The retrieved dust top heights are compared against the extinction backscatter profiles obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization lidar. Infrared optical depths from AIRS correlate favorably with visible optical depths from MODIS, and dust top heights agree reasonably with lidar observations for the single-layered dust storms over the Taklimakan Desert.

  9. High precision wavelength meter with Fabry-Perot optics

    NASA Astrophysics Data System (ADS)

    Konishi, N.; Suzuki, T.; Taira, Y.; Kato, H.; Kasuya, T.

    1981-07-01

    A high precision wavelength meter in the visible is described, which is based on a Fabry-Perot interferometer with several etalons of different resolution. The interference fringe pattern projected on a photo-diode array detector is computationally processed to give a stepwise refinement of the wavelength value to any adjusted accuracy. The present model intends to provide digital and real-time values of high precision wavelength for dye-laser spectroscopy, and to serve as a monitor or as a pilot for wavelength control of a dye-laser source of nanosecond pulses. The model is, therefore, designed with particular emphasis on its short-pulse capability and on-line mode of operation as well as on its high sensitivity and resolution. Some arrangements of essential necessity are involved therein, such as to avoid an errorneous wavelength readout for a noisy incidence of pulsed field. The ultimate accuracy of wavelength measurement is prescribed by the resolving power of the thickest etalon employed. As applied to the pulsed source, the model determines the wavelength to the accuracy of ±one part in 107 for even a single shot nanosecond incidence of a fraction of μJ energy. The design and performance are described in connection to pulsed dye-laser incidence.

  10. Mechanisms behind low-cloud optical depth response to temperature in ARM site observations

    NASA Astrophysics Data System (ADS)

    Terai, Christopher; Zhang, Yunyan; Klein, Stephen; Zelinka, Mark

    2017-04-01

    Most state-of-the-art climate models predict the cloud optical depth increases with warming in the mid- and high-latitudes. Proposed mechanisms exist in the literature to support this increase in cloud optical depth, and the cloud processes driving the negative cloud feedback have been identified in several climate models. However, recent studies find that this negative cloud feedback in the mid- and high-latitudes is likely overestimated in climate models. For example, an analysis of satellite retrievals suggests that the optical depth of low-level clouds decreases with warming. Less attention has been placed on understanding the cloud processes that drive cloud optical depth changes in observations. In this study, we use ground-based observations from three mid- and high-latitude sites, managed by the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) Program, to determine the mechanisms that drive cloud changes at those sites. We test whether there is evidence in the observations that support three mechanisms that have been proposed to drive a cloud optical depth response to warming. We test a) whether cloud liquid water content increases with warming following changes in the adiabatic lapse rate of the saturated water vapor, as determined by the Clausius-Clapeyron relationship, b) whether the change in phase-partitioning of clouds due to warming increase the optical depth by changing the cloud optical and microphysical properties and processes, and c) whether warming leads to a thinning of clouds by enhancing the drying efficiency of cloud top mixing. We find that although increases in cloud liquid content with warming is consistent with the Clausius-Clapeyron relationship at the one oceanic site, they do not hold over the two continental sites. We also find that the liquid-ice partitioning of total cloud water differs between sites and find evidence that increasing ice fraction leads to clouds with lower LWP. We also test whether the

  11. Studies on aerosol optical depth in biomass burning areas using satellite and ground-based observations

    NASA Astrophysics Data System (ADS)

    Kant, Yogesh; Ghosh, A. B.; Sharma, M. C.; Gupta, Prabhat K.; Prasad, V. Krishna; Badarinath, K. V. S.; Mitra, A. P.

    2000-02-01

    Biomass burning in the tropics is a source of trace gas fluxes and particulate matter. During the last decade, the shifting cultivation practices have been increased in the tropical forest of Eastern Ghats, Andhra Pradesh, India. In order to quantify the fluxes emitted from the biomass burning due to shifting cultivation practices, a field experiment has been conducted on February 16-25, 1999. The present study provides the variation of aerosol optical depth over the shifting cultivation areas of Rampa Revenue Division, Eastern Ghats using a sunphotometer in synchronism with satellite data. Optical depth values increased up to 2.0 during the burning phase and then returned to normal values (0.2-0.5). The atmospheric correction of the satellite data using the optical depth values suggested improvement in the overall contrast of the image and increase in the dynamic range of the normalized difference vegetation index (NDVI) values of various features in the image.

  12. A Comparison of Model- and Satellite-Derived Aerosol Optical Depth and Reflectivity

    NASA Technical Reports Server (NTRS)

    Penner, Joyce E.; Zhang, Sophia Y.; Chin, Mian; Chuang, Catherine C.; Feichter, Johann; Feng, Yan; Geogdzhayev, Igor V.; Ginoux, Paul; Herzog, Michael; Higurashi, Akiko

    2002-01-01

    The determination of an accurate quantitative understanding of the role of tropospheric aerosols in the earth's radiation budget is extremely important because forcing by anthropogenic aerosols presently represents one of the most uncertain aspects of climate models. Here the authors present a systematic comparison of three different analyses of satellite-retrieved aerosol optical depth based on the Advanced Very High Resolution Radiometer (AVHRR)- measured radiances with optical depths derived from six different models. Also compared are the model-derived clear-sky reflected shortwave radiation with satellite-measured reflectivities derived from the Earth Radiation Budget Experiment (ERBE) satellite. The three different satellite-derived optical depths differ by between -0.10 and 0.07 optical depth units in comparison to the average of the three analyses depending on latitude and month, but the general features of the retrievals are similar. The models differ by between -0.09 and +0.16 optical depth units from the average of the models. Differences between the average of the models and the average of the satellite analyses range over -0.11 to +0.05 optical depth units. These differences are significant since the annual average clear-sky radiative forcing associated with the difference between the average of the models and the average of the satellite analyses ranges between -3.9 and 0.7 W m(exp -2) depending on latitude and is -1.7 W m (exp -2) on a global average annual basis. Variations in the source strengths of dimethylsulfide (DMS)-derived aerosols and sea salt aerosols can explain differences between the models, and between the models and satellite retrievals of up to 0.2 optical depth units. The comparison of model-generated reflected shortwave radiation and ERBE-measured shortwave radiation is similar in character as a function of latitude to the analysis of modeled and satellite-retrieved optical depths, but the differences between the modeled clear

  13. Measurement of optical penetration depth and refractive index of human tissue

    NASA Astrophysics Data System (ADS)

    Xie, Shusen; Li, Hui; Li, Buhong

    2003-01-01

    Experimental techniques for measurement of optical penetration depth and refractive index of human tissue are presented, respectively. Optical penetration depth can be obtained from the measurement of the relative fluence-depth distribution inside the target tissue. The depth of normal and carcinomatous human lung tissues irradiated with the wavelengths of 406.7, 632.8 and 674.4 nm in vitro are respectively determined. In addition, a novel simple method based on total internal reflection for measuring the refractive index of biotissue in vivo is developed, and the refractive indices of skin from people of different age, sex and skin color are measured. Their refractive indices are almost same and the average is 1.533.

  14. Precision Targeting with a Tracking adaptive Optics Scanning Laser Ophthalmoscope

    DTIC Science & Technology

    2006-02-01

    in Figure 2) but drives two galvanometers placed at appropriate conjugates within the path of the adaptive optics scanning laser ophthalmoscope...reflectometer. The input to the "slave" control loop is the scaled position signals from the master galvanometers . The slave tracking mirrors are placed at...signals and drive galvanometers . The DSP has a loop rate of 62.5 kHz (compared to 16 kHz in the previously-used real-time processing board) for a

  15. Antenna pointing compensation based on precision optical measurement techniques

    NASA Technical Reports Server (NTRS)

    Schumacher, L. L.; Vivian, H. C.

    1988-01-01

    The pointing control loops of the Deep Space Network 70 meter antennas extend only to the Intermediate Reference Structure (IRS). Thus, distortion of the structure forward of the IRS due to unpredictable environmental loads can result in uncompensated boresight shifts which degrade blind pointing accuracy. A system is described which can provide real time bias commands to the pointing control system to compensate for environmental effects on blind pointing performance. The bias commands are computed in real time based on optical ranging measurements of the structure from the IRS to a number of selected points on the primary and secondary reflectors.

  16. Computer-generated holograms for precision optical testing

    NASA Astrophysics Data System (ADS)

    Wei, Xiaohong; He, Yuhang; Xu, Kaiyuan; Gao, Bo; Li, Qiang; Chai, Liqun

    2016-09-01

    Computer generated holograms (CGHs) are state-of-the-art components in optical systems, and are widely used in combination with standard Fizeau interferometers. The primary role of the CGHs is to generate reference wavefront with any desired shape. A method of interferometrically measuring large convex lens with CGHs is adopted, and the results from a set of experiments that demonstrate the accuracy and simplicity of performing the holographic test are presented. A direct comparison of the CGH measurement with results from a compensation method shows excellent agreement. Finally, measurement uncertainty due to substrate error and hologram fabrication processes is analyzed.

  17. Nocturnal aerosol optical depth measurements with a small-aperture automated photometer using the moon as a light source

    USGS Publications Warehouse

    Berkoff, T.A.; Sorokin, M.; Stone, T.; Eck, T.F.; Hoff, R.; Welton, E.; Holben, B.

    2011-01-01

    A method is described that enables the use of lunar irradiance to obtain nighttime aerosol optical depth (AOD) measurements using a small-aperture photometer. In this approach, the U.S. Geological Survey lunar calibration system was utilized to provide high-precision lunar exoatmospheric spectral irradiance predictions for a ground-based sensor location, and when combined with ground measurement viewing geometry, provided the column optical transmittance for retrievals of AOD. Automated multiwavelength lunar measurements were obtained using an unmodified Cimel-318 sunphotometer sensor to assess existing capabilities and enhancements needed for day/night operation in NASA's Aerosol Robotic Network (AERONET). Results show that even existing photometers can provide the ability for retrievals of aerosol optical depths at night near full moon. With an additional photodetector signal-to-noise improvement of 10-100, routine use over the bright half of the lunar phase and a much wider range of wavelengths and conditions can be achieved. Although the lunar cycle is expected to limit the frequency of observations to 30%-40% compared to solar measurements, nevertheless this is an attractive extension of AERONET capabilities. ?? 2011 American Meteorological Society.

  18. Nocturnal Aerosol Optical Depth Measurements with a Small-Aperture Automated Photometer Using the Moon as a Light Source

    NASA Technical Reports Server (NTRS)

    Berkoff, Timothy A.; Sorokin, Mikail; Stone, Tom; Eck, Thomas F.; Hoff, Raymond; Welton, Ellsworth; Holben, Brent

    2011-01-01

    A method is described that enables the use of lunar irradiance to obtain nighttime aerosol optical depth (AOD) measurements using a small-aperture photometer. In this approach, the U.S. Geological Survey lunar calibration system was utilized to provide high-precision lunar exoatmospheric spectral irradiance predictions for a ground-based sensor location, and when combined with ground measurement viewing geometry, provided the column optical transmittance for retrievals of AOD. Automated multiwavelength lunar measurements were obtained using an unmodified Cimel-318 sunphotometer sensor to assess existing capabilities and enhancements needed for day/night operation in NASA s Aerosol Robotic Network (AERONET). Results show that even existing photometers can provide the ability for retrievals of aerosol optical depths at night near full moon. With an additional photodetector signal-to-noise improvement of 10-100, routine use over the bright half of the lunar phase and a much wider range of wavelengths and conditions can be achieved. Although the lunar cycle is expected to limit the frequency of observations to 30%-40% compared to solar measurements, nevertheless this is an attractive extension of AERONET capabilities.

  19. Nocturnal Aerosol Optical Depth Measurements with a Small-Aperture Automated Photometer Using the Moon as a Light Source

    NASA Technical Reports Server (NTRS)

    Berkoff, Timothy A.; Sorokin, Mikail; Stone, Tom; Eck, Thomas F.; Hoff, Raymond; Welton, Ellsworth; Holben, Brent

    2011-01-01

    A method is described that enables the use of lunar irradiance to obtain nighttime aerosol optical depth (AOD) measurements using a small-aperture photometer. In this approach, the U.S. Geological Survey lunar calibration system was utilized to provide high-precision lunar exoatmospheric spectral irradiance predictions for a ground-based sensor location, and when combined with ground measurement viewing geometry, provided the column optical transmittance for retrievals of AOD. Automated multiwavelength lunar measurements were obtained using an unmodified Cimel-318 sunphotometer sensor to assess existing capabilities and enhancements needed for day/night operation in NASA s Aerosol Robotic Network (AERONET). Results show that even existing photometers can provide the ability for retrievals of aerosol optical depths at night near full moon. With an additional photodetector signal-to-noise improvement of 10-100, routine use over the bright half of the lunar phase and a much wider range of wavelengths and conditions can be achieved. Although the lunar cycle is expected to limit the frequency of observations to 30%-40% compared to solar measurements, nevertheless this is an attractive extension of AERONET capabilities.

  20. Depth-sensitive optical spectroscopy for layered tissue measurements (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Yu, Xiaojun; Liu, Quan; Liu, Linbo; Ong, Yi Hong

    2017-02-01

    Disease diagnosis based on the visual inspection of the pathological presentations or symptoms on the epithelial tissue such as the skin are subjective and highly depend on the experience of the doctors. Vital diagnostic information for the accurate identification of diseases is usually located underneath the surface and its depth distribution is known to be related to disease progression. Although optical spectroscopic measurements are fast and non-invasive, the accurate retrieval of the depth-specific diagnostic information is complicated by the heterogeneous nature of epithelial tissues. The optical signal measured from a tissue is often the result of averaging from a large tissue volume that mixes information from the region of interest and the surrounding tissue region, especially from the overlaying layers. Our group has developed a series of techniques for depth sensitive optical measurements from such layered tissues. We will first review the earlier development of composite fiber-optic probe, in which the source-detector separation and the angles of source and detector fibers are varied to achieve depth sensitive measurements. Then the more recent development of non-contact axicon lens based probes for depth sensitive fluorescence measurements and the corresponding numerical methods for optimization will be introduced. Finally, the most recently developed snapshot axicon lens based probe that can measure Raman spectra from five different depths at the same time will be discussed. Results from tissue phantoms, ex vivo pork samples and in vivo fingernail measurements will be presented, which indicates the great potential of depth sensitive optical spectroscopy for clinical tissue diagnosis.

  1. LINKING Lyα AND LOW-IONIZATION TRANSITIONS AT LOW OPTICAL DEPTH

    SciTech Connect

    Jaskot, A. E.; Oey, M. S.

    2014-08-20

    We suggest that low optical depth in the Lyman continuum (LyC) may relate the Lyα emission, C II and Si II absorption, and C II* and Si II* emission seen in high-redshift galaxies. We base this analysis on Hubble Space Telescope Cosmic Origins Spectrograph spectra of four Green Pea (GP) galaxies, which may be analogs of z > 2 Lyα emitters (LAEs). In the two GPs with the strongest Lyα emission, the Lyα line profiles show reduced signs of resonant scattering. Instead, the Lyα profiles resemble the Hα line profiles of evolved star ejecta, suggesting that the Lyα emission originates from a low column density and similar outflow geometry. The weak C II absorption and presence of non-resonant C II* emission in these GPs support this interpretation and imply a low LyC optical depth along the line of sight. In two additional GPs, weak Lyα emission and strong C II absorption suggest a higher optical depth. These two GPs differ in their Lyα profile shapes and C II* emission strengths, however, indicating different inclinations of the outflows to our line of sight. With these four GPs as examples, we explain the observed trends linking Lyα, C II, and C II* in stacked LAE spectra, in the context of optical depth and geometric effects. Specifically, in some galaxies with strong Lyα emission, a low LyC optical depth may allow Lyα to escape with reduced scattering. Furthermore, C II absorption, C II* emission, and Lyα profile shape can reveal the optical depth, constrain the orientation of neutral outflows in LAEs, and identify candidate LyC emitters.

  2. High-precision optical systems with inexpensive hardware: a unified alignment and structural design approach

    NASA Astrophysics Data System (ADS)

    Winrow, Edward G.; Chavez, Victor H.

    2011-09-01

    High-precision opto-mechanical structures have historically been plagued by high costs for both hardware and the associated alignment and assembly process. This problem is especially true for space applications where only a few production units are produced. A methodology for optical alignment and optical structure design is presented which shifts the mechanism of maintaining precision from tightly toleranced, machined flight hardware to reusable, modular tooling. Using the proposed methodology, optical alignment error sources are reduced by the direct alignment of optics through their surface retroreflections (pips) as seen through a theodolite. Optical alignment adjustments are actualized through motorized, sub-micron precision actuators in 5 degrees of freedom. Optical structure hardware costs are reduced through the use of simple shapes (tubes, plates) and repeated components. This approach produces significantly cheaper hardware and more efficient assembly without sacrificing alignment precision or optical structure stability. The design, alignment plan and assembly of a 4" aperture, carbon fiber composite, Schmidt-Cassegrain concept telescope is presented.

  3. Design and fabrication of an optical probe with a phase filter for extended depth of focus.

    PubMed

    Xing, Jingchao; Kim, Junyoung; Yoo, Hongki

    2016-01-25

    The trade-off between spot size and depth of focus (DOF) often limits the performance of optical systems, such as optical coherence tomography and optical tweezers. Although researchers have proposed various methods to extend the DOF in free-space optics, many are difficult to implement in miniaturized optical probes due to space limitations. In this study, we present an optical probe with an extended DOF using a binary phase spatial filter (BPSF). The BPSF pattern was fabricated on the distal tip of an optical probe with a diameter of 1 mm by replica molding soft lithography, which can be easily implemented in a miniaturized optical probe due to its simple configuration. We optimized the BPSF pattern to enhance DOF, spot diameter, and light efficiency. To evaluate the fabricated endoscopic optical probe, we measured the three-dimensional point spread function of the BPSF probe and compared it with a probe without BPSF. The BPSF probe has a spot diameter of 3.56 μm and a DOF of 199.7 μm, while the probe without BPSF has a spot diameter of 3.69 μm and a DOF of 73.9 μm, representing a DOF gain of 2.7. We anticipate that this optical probe can be used in biomedical applications, including optical imaging and optical trapping techniques.

  4. Increasing the penetration depth for ultrafast laser tissue ablation using glycerol based optical clearing

    NASA Astrophysics Data System (ADS)

    Gabay, Ilan; Subramanian, Kaushik G.; Martin, Chris; Yildirim, Murat; Tuchin, Valery V.; Ben-Yakar, Adela

    2016-03-01

    Background: Deep tissue ablation is the next challenge in ultrafast laser microsurgery. By focusing ultrafast pulses below the tissue surface one can create an ablation void confined to the focal volume. However, as the ablation depth increases in a scattering tissue, increase in the required power can trigger undesired nonlinear phenomena out of focus that restricts our ability to ablate beyond a maximum ablation depth of few scattering lengths. Optical clearing (OC) might reduce the intensity and increase the maximal ablation depth by lowering the refractive index mismatch, and therefore reducing scattering. Some efforts to ablate deeper showed out of focus damage, while others used brutal mechanical methods for clearing. Our clinical goal is to create voids in the scarred vocal folds and inject a biomaterial to bring back the tissue elasticity and restore phonation. Materials and methods: Fresh porcine vocal folds were excised and applied a biocompatible OC agent (75% glycerol). Collimated transmittance was monitored. The tissue was optically cleared and put under the microscope for ablation threshold measurements at different depths. Results: The time after which the tissue was optically cleared was roughly two hours. Fitting the threshold measurements to an exponential decay graph indicated that the scattering length of the tissue increased to 83+/-16 μm, which is more than doubling the known scattering length for normal tissue. Conclusion: Optical clearing with Glycerol increases the tissue scattering length and therefore reduces the energy for ablation and increases the maximal ablation depth. This technique can potentially improve clinical microsurgery.

  5. Analytical Derivation of the Vegetation Optical Depth from the Microwave Polarization Difference Index

    NASA Technical Reports Server (NTRS)

    Meesters, Antoon G. C. A.; DeJeu, Richard A. M.; Owe, Manfred

    2006-01-01

    A numerical solution for the canopy optical depth in an existing microwave-based land surface parameter retrieval model is presented. The optical depth is derived from the microwave polarization difference index and the dielectric constant of the soil. The original procedure used an approximation in the form of a logarithmic decay function to define this relationship, and was derived through a series of lengthy polynomials. These polynomials had to be recalculated when the scattering albedo or antenna incidence angle changes. The new procedure is computationally more efficient and accurate.

  6. Measurements of total column ozone, precipitable water content and aerosol optical depth at Sofia

    NASA Astrophysics Data System (ADS)

    Kaleyna, P.; Kolev, N.; Savov, P.; Evgenieva, Ts.; Danchovski, V.; Muhtarov, P.

    2016-03-01

    This article reports the results of a study related to variations in total ozone content, aerosol optical depth, water vapor content and Ångström coefficients from summer campaign carried out in June-July 2014, at two sites in the city of Sofia (Astronomical Observatory in the Borisova Gradina Park and National Institute of Geophysics, Geodesy and Geography (NIGGG)). The results of data analysis indicate the following: Spectral dependence of aerosol optical depth (AOD); Greater AOD values due to greater portion of aerosols; Inverse relationship between the time variations of AOD or water vapor and ozone.

  7. Composite method for precise freeform optical beam shaping.

    PubMed

    Feng, Zexin; Froese, Brittany D; Liang, Rongguang

    2015-11-01

    We present a composite freeform surface construction method for creating a high-accuracy irradiance distribution from a given incident beam under the influence of diffraction. The main idea is that we first determine a fully continuous freeform surface estimate by solving a standard Monge-Ampère equation and then refine it using an iterative Fourier-transform algorithm associated with over-compensation. Although this method can only be implemented in the paraxial approximation, it can significantly simplify the design and is applicable to many examples that fulfill this restriction. The resulting optical surface, unwrapped from the final phase, is an unusual discontinuous freeform surface that can produce very promising performances in terms of surface roughness and irradiance accuracy.

  8. Precision spectroscopy of acetylene transitions using an optical frequency synthesizer.

    PubMed

    Ahtee, V; Merimaa, M; Nyholm, K

    2009-09-01

    An optical frequency synthesizer is used for saturation spectroscopy of acetylene near 1540 nm. In the synthesizer, a user-specified frequency is generated from an atomic time base by phase locking the second harmonic of a cw near-IR external-cavity diode laser (ECDL) to a Ti:sapphire frequency comb. By stepping the repetition rate of the frequency comb, the ECDL frequency is swept over an acetylene transition in a saturated absorption spectroscopy setup. Hence, a spectral lineshape is measured with an absolute frequency scale. Line-center frequencies determined by fitting theoretical line profiles to the measured data are in good agreement with values measured with the ECDL stabilized to acetylene by third-harmonic locking and with the values recommended by the International Committee for Weights and Measures (CIPM).

  9. Depth Discrimination in Diffuse Optical Transmission Imaging by Planar Scanning Off-Axis Fibers: INITIAL Applications to Optical Mammography

    PubMed Central

    Kainerstorfer, Jana M.; Yu, Yang; Weliwitigoda, Geethika; Anderson, Pamela G.; Sassaroli, Angelo; Fantini, Sergio

    2013-01-01

    We present a method for depth discrimination in parallel-plate, transmission mode, diffuse optical imaging. The method is based on scanning a set of detector pairs, where the two detectors in each pair are separated by a distance δDi along direction δDi within the x-y scanning plane. A given optical inhomogeneity appears shifted by αiδDi (with 0≤ αi ≤1) in the images collected with the two detection fibers of the i-th pair. Such a spatial shift can be translated into a measurement of the depth z of the inhomogeneity, and the depth measurements based on each detector pair are combined into a specially designed weighted average. This depth assessment is demonstrated on tissue-like phantoms for simple inhomogeneities such as straight rods in single-rod or multiple-rod configurations, and for more complex curved structures which mimic blood vessels in the female breast. In these phantom tests, the method has recovered the depth of single inhomogeneities in the central position of the phantom to within 4 mm of their actual value, and within 7 mm for more superficial inhomogeneities, where the thickness of the phantom was 65 mm. The application of this method to more complex images, such as optical mammograms, requires a robust approach to identify corresponding structures in the images collected with the two detectors of a given pair. To this aim, we propose an approach based on the inner product of the skeleton images collected with the two detectors of each pair, and we present an application of this approach to optical in vivo images of the female breast. This depth discrimination method can enhance the spatial information content of 2D projection images of the breast by assessing the depth of detected structures, and by allowing for 3D localization of breast tumors. PMID:23516494

  10. Underwater Depth and Temperature Sensing Based on Fiber Optic Technology for Marine and Fresh Water Applications

    PubMed Central

    Duraibabu, Dinesh Babu; Leen, Gabriel; Toal, Daniel; Newe, Thomas; Lewis, Elfed; Dooly, Gerard

    2017-01-01

    Oceanic conditions play an important role in determining the effects of climate change and these effects can be monitored through the changes in the physical properties of sea water. In fact, Oceanographers use various probes for measuring the properties within the water column. CTDs (Conductivity, Temperature and Depth) provide profiles of physical and chemical parameters of the water column. A CTD device consists of Conductivity (C), Temperature (T) and Depth (D) probes to monitor the water column changes with respect to relative depth. An optical fibre-based point sensor used as a combined pressure (depth) and temperature sensor and the sensor system are described. Measurements accruing from underwater trials of a miniature sensor for pressure (depth) and temperature in the ocean and in fresh water are reported. The sensor exhibits excellent stability and its performance is shown to be comparable with the Sea-Bird Scientific commercial sensor: SBE9Plus. PMID:28555006

  11. Underwater Depth and Temperature Sensing Based on Fiber Optic Technology for Marine and Fresh Water Applications.

    PubMed

    Duraibabu, Dinesh Babu; Leen, Gabriel; Toal, Daniel; Newe, Thomas; Lewis, Elfed; Dooly, Gerard

    2017-05-27

    Oceanic conditions play an important role in determining the effects of climate change and these effects can be monitored through the changes in the physical properties of sea water. In fact, Oceanographers use various probes for measuring the properties within the water column. CTDs (Conductivity, Temperature and Depth) provide profiles of physical and chemical parameters of the water column. A CTD device consists of Conductivity (C), Temperature (T) and Depth (D) probes to monitor the water column changes with respect to relative depth. An optical fibre-based point sensor used as a combined pressure (depth) and temperature sensor and the sensor system are described. Measurements accruing from underwater trials of a miniature sensor for pressure (depth) and temperature in the ocean and in fresh water are reported. The sensor exhibits excellent stability and its performance is shown to be comparable with the Sea-Bird Scientific commercial sensor: SBE9Plus.

  12. Removing the depth-degeneracy in optical frequency domain imaging with frequency shifting

    PubMed Central

    Yun, S. H.; Tearney, G. J.; de Boer, J. F.; Bouma, B. E.

    2009-01-01

    A novel technique using an acousto-optic frequency shifter in optical frequency domain imaging (OFDI) is presented. The frequency shift eliminates the ambiguity between positive and negative differential delays, effectively doubling the interferometric ranging depth while avoiding image cross-talk. A signal processing algorithm is demonstrated to accommodate nonlinearity in the tuning slope of the wavelength-swept OFDI laser source. PMID:19484034

  13. Process influences and correction possibilities for high precision injection molded freeform optics

    NASA Astrophysics Data System (ADS)

    Dick, Lars; Risse, Stefan; Tünnermann, Andreas

    2016-08-01

    Modern injection molding processes offer a cost-efficient method for manufacturing high precision plastic optics for high volume applications. Besides form deviation of molded freeform optics, internal material stress is a relevant influencing factor for the functionality of a freeform optics in an optical system. This paper illustrates dominant influence parameters of an injection molding process relating to form deviation and internal material stress based on a freeform demonstrator geometry. Furthermore, a deterministic and efficient way for 3D mold correcting of systematic, asymmetrical shrinkage errors is shown to reach micrometer range shape accuracy at diameters up to 40 mm. In a second case, a stress-optimized parameter combination using unusual molding conditions was 3D corrected to reach high precision and low stress freeform polymer optics.

  14. Dynamic metrology and data processing for precision freeform optics fabrication and testing

    NASA Astrophysics Data System (ADS)

    Aftab, Maham; Trumper, Isaac; Huang, Lei; Choi, Heejoo; Zhao, Wenchuan; Graves, Logan; Oh, Chang Jin; Kim, Dae Wook

    2017-06-01

    Dynamic metrology holds the key to overcoming several challenging limitations of conventional optical metrology, especially with regards to precision freeform optical elements. We present two dynamic metrology systems: 1) adaptive interferometric null testing; and 2) instantaneous phase shifting deflectometry, along with an overview of a gradient data processing and surface reconstruction technique. The adaptive null testing method, utilizing a deformable mirror, adopts a stochastic parallel gradient descent search algorithm in order to dynamically create a null testing condition for unknown freeform optics. The single-shot deflectometry system implemented on an iPhone uses a multiplexed display pattern to enable dynamic measurements of time-varying optical components or optics in vibration. Experimental data, measurement accuracy / precision, and data processing algorithms are discussed.

  15. Precision molding of optics: a review of its development and applications

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Liu, G.; Zhao, X.; Dambon, Olaf; Klocke, F.; Yi, A. Y.

    2016-09-01

    Compression molding of precision optics is gradually becoming a viable manufacturing process for low cost high performance optical elements. In this process, a glass preform in the form of gob or disk is heated rapidly above its glass transition temperature then pressed between two optical mold halves to finish dimensions. The molded lens is first cooled slowly then at a fast cooling rate to room temperature to complete the process. For more than a decade, the authors have conducted a collaborated research in glass molding using both experiments and numerical modeling. In this presentation, we will discuss the recent work in molding of both conventional glass optics and extreme high temperature glass optics - fused silica material. In addition, development of graphene like coatings for precision glass molding will also be described.

  16. Imaging depths of near-infrared quantum dots in first and second optical windows.

    PubMed

    Won, Nayoun; Jeong, Sanghwa; Kim, Kangwook; Kwag, Jungheon; Park, Joonhyuck; Kim, Sang Geol; Kim, Sungjee

    2012-01-01

    Potential advantages of quantum dot (QD) imaging in the second optical window (SOW) at 1,000 to 1,400 nm over the first optical window (FOW) at 700 to 900 nm have attracted much interest. QDs that emit at 800 nm (800QDs) and QDs that emit at 1,300 nm (1,300QDs) are used to investigate the imaging depths at the FOW and SOW. QD images in biologic tissues are processed binarized via global thresholding method, and the imaging depths are determined using the criteria of contrast to noise ratio and relative apparent size. Owing to the reduced scattering in the SOW, imaging depth in skin can be extended by approximately three times for 1,300QD/SOW over 800QD/FOW. In liver, excitation of 1,300QD/SOW can be shifted to longer wavelengths; thus, the imaging depth can be extended by 1.4 times. Effects of quantum yield (QY), concentration, incidence angle, polarization, and fluence rate F on imaging depth are comprehensively studied. Under F approved by the Food and Drug Administration, 1,300QDs with 50% QY can reach imaging depths of 29.7 mm in liver and 17.5 mm in skin. A time-gated excitation using 1,000 times higher F pulses can obtain the imaging depth of ≈ 5 cm. To validate our estimates, in vivo whole-body imaging experiments are performed using small-animal models.

  17. Optically-Selected Cluster Catalogs As a Precision Cosmology Tool

    SciTech Connect

    Rozo, Eduardo; Wechsler, Risa H.; Koester, Benjamin P.; Evrard, August E.; McKay, Timothy A.; /Michigan U.

    2007-03-26

    We introduce a framework for describing the halo selection function of optical cluster finders. We treat the problem as being separable into a term that describes the intrinsic galaxy content of a halo (the Halo Occupation Distribution, or HOD) and a term that captures the effects of projection and selection by the particular cluster finding algorithm. Using mock galaxy catalogs tuned to reproduce the luminosity dependent correlation function and the empirical color-density relation measured in the SDSS, we characterize the maxBCG algorithm applied by Koester et al. to the SDSS galaxy catalog. We define and calibrate measures of completeness and purity for this algorithm, and demonstrate successful recovery of the underlying cosmology and HOD when applied to the mock catalogs. We identify principal components--combinations of cosmology and HOD parameters--that are recovered by survey counts as a function of richness, and demonstrate that percent-level accuracies are possible in the first two components, if the selection function can be understood to {approx} 15% accuracy.

  18. Precision Calculation of Blackbody Radiation Shifts for Optical Frequency Metrology

    SciTech Connect

    Safronova, M. S.; Kozlov, M. G.; Clark, Charles W.

    2011-09-30

    We show that three group IIIB divalent ions, B{sup +}, Al{sup +}, and In{sup +}, have anomalously small blackbody radiation (BBR) shifts of the ns{sup 2} {sup 1}S{sub 0}-nsnp {sup 3}P{sub 0}{sup o} clock transitions. The fractional BBR shifts for these ions are at least 10 times smaller than those of any other present or proposed optical frequency standards at the same temperature, and are less than 0.3% of the Sr clock shift. We have developed a hybrid configuration-interaction + coupled-cluster method that provides accurate treatment of correlation corrections in such ions and yields a rigorous upper bound on the uncertainty of the final results. We reduce the BBR contribution to the fractional frequency uncertainty of the Al{sup +} clock to 4x10{sup -19} at T=300 K. We also reduce the uncertainties due to this effect at room temperature to 10{sup -18} level for B{sup +} and In{sup +} to facilitate further development of these systems for metrology and quantum sensing.

  19. Measuring changes in the scattering properties of Intralipid at different depths with optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Kinnunen, Matti; Myllylä, Risto

    2007-07-01

    Optical coherence tomography (OCT) is a powerful tool for imaging tissue structure. The images provide information on a micrometer scale. By averaging depth scans, an intensity profile can be formed as a function of depth. The slope of a straight line fitted to the OCT signal depth profile contains information on light attenuation in the sample at different depths. This slope can be used to detect changes in the scattering properties of the sample, especially in a single scattering region. In this article, the effect of fitting the line at different depths on detection sensitivity was studied in Intralipid phantoms with different concentrations. Different glucose concentrations were also used with 5 % Intralipid samples. Different depths were studied because the depth of the dermis and the thicknesses of skin layers in human skin vary in different body locations. The results show that the sensitivity of detecting changes in the scattering properties of Intralipid is better at a depth corresponding to that of the dermis in the human arm (0.166 - 0.276 mm) than at a depth equaling the dermis in the forefinger (0.441 - 0.579 mm). For this reason, the applicability of the single scattering model for fitting the straight line to different depths of the OCT signal is limited, and a more comprehensive model for extracting changes in scattering is recommended at greater depths. This has to be kept in mind when determining the depth position for registering glucose-induced changes in vivo with an OCT-based glucose sensor.

  20. Precision shaping of transparent materials for optical devices with VUV laser radiation

    NASA Astrophysics Data System (ADS)

    Temme, Thorsten; Ostendorf, Andreas; Kulik, Christian J.

    2004-04-01

    The precision machining of glass by laser ablation has been expanded with the short wavelength of the 157 nm of the F2 excimer laser. The high absorption of this wavelength in any optical glass, especially in UV-grade fused silica, offers a new approach to generate high quality surfaces, addressing also micro-optical components. In this paper, the machining of basic diffractive and refractive optical components and the required machining and process technology is presented. Applications that are addressed are cylindrical and rotational symmetrical micro lenses and diffractive optics like phase transmission grating and diffractive optical elements (DOEs). These optical surfaces have been machined into bulk material as well as on fiber end surfaces, to achieve compact (electro)-optical elements with high functionality and packaging density. The short wavelength of 157 nm used in the investigations require either vacuum or high purity inert gas environments. The influence of different ambient conditions is presented.

  1. High precision deflection measurement of microcantilever in an optical pickup head based atomic force microscopy

    SciTech Connect

    Lee, Sang Heon

    2012-11-15

    This paper presents the methodology to measure the precise deflection of microcantilever in an optical pickup head based atomic force microscopy. In this paper, three types of calibration methods have been proposed: full linearization, sectioned linearization, and the method based on astigmatism. In addition, the probe heads for easy calibration of optical pickup head and fast replacement of optical pickup head have been developed. The performances of each method have been compared through a set of experiments and constant height mode operation which was not possible in the optical pickup head based atomic force microscopy has been carried out successfully.

  2. Light storage in a cold atomic ensemble with a high optical depth

    NASA Astrophysics Data System (ADS)

    Park, Kwang-Kyoon; Chough, Young-Tak; Kim, Yoon-Ho

    2017-06-01

    A quantum memory with a high storage efficiency and a long coherence time is an essential element in quantum information applications. Here, we report our recent development of an optical quantum memory with a rubidium-87 cold atom ensemble. By increasing the optical depth of the medium, we have achieved a storage efficiency of 65% and a coherence time of 51 μs for a weak laser pulse. The result of a numerical analysis based on the Maxwell-Bloch equations agrees well with the experimental results. Our result paves the way toward an efficient optical quantum memory and may find applications in photonic quantum information processing.

  3. Inverse problem theory in the optical depth profilometry of thin films

    NASA Astrophysics Data System (ADS)

    Power, J. F.

    2002-12-01

    The problem of nondestructive measurement of composition with depth on the scale of ˜0.1-500 μm, in polymers and related materials, has many applications in traditional and recent areas of thin film processing. This article reviews the optical depth profilometry techniques operating on this scale based on optical absorption, photoluminescence, elastic, and inelastic scattering. These methods include photoacoustic and photothermal imaging (including pulsed laser opto-acoustic profiling), attenuated total reflectance infrared, integrated optical spectroscopy methods (based on excitation of planar waveguide structures), confocal scanning microscopy, and the recent technique of light profile microscopy. The profiling of planar structures is emphasized. A common element of all of these methods is that depth mapping requires the solution of a linear inverse problem, where a map of the sample properties is mathematically reconstructed from a set of experimental measurements. This problem is to some extent ill conditioned in some or all regimes of measurement, with the result that depth maps may show sensitivity to data errors. A method is presented for assessing performance of the above experimental depth profilometry techniques in terms of ill conditioning as indicated by: spatial resolution, sensitivity to data errors, and apparent multiplicity of solutions. This method is applied a priori given a knowledge of the linear response theory and measurement parameters Application is made to individual profiling techniques, the performance of each in applications is reviewed, and an inter-comparison is made based on the conditioning of the inverse problem.

  4. Direct numerical modeling of Saturn's dense rings at high optical depth

    NASA Astrophysics Data System (ADS)

    Richardson, Derek C.; Ballouz, Ronald-Louis; Morishima, Ryuji

    2015-11-01

    Saturn's B ring exhibits complex optical depth structure of uncertain origin. We are investigating the extent to which viscous overstability and/or gravitational wakes can give rise to this structure, via discrete particle numerical simulations. We use the parallelized N-body tree code pkdgrav with a soft-sphere collision model for detailed treatment of particle collisional physics, including multi-point persistent contact with static, sliding, rolling, and twisting friction forces. This enables us to perform local simulations with millions of particles, realistic sizes, and configurable material properties in high-optical-depth ring patches with near-linear scaling across multiple processors. Recent code improvements to the collision search algorithm provide a further roughly factor of 2 speedup. We present results from the first year of this study in which a library of simulations with different optical depths was constructed. Parameters explored include normal (dynamical) optical depths between 0.5 (approximately 100,000 particles) and 4.0 (approximately 8.3 million particles) in ring patches of dimension 6 by 6 critical Toomre wavelengths, using material parameters ranging from highly elastic smooth spheres to rough "gravel"-like particles. We also vary the particle internal densities to enhance (low density)/suppress (high density) viscous overstability in order to compare against gravitational instability in these different regimes. These libraries will be used to carry out simulated observations for comparison with Cassini CIRS temperature measurements and UVIS occulation data of Saturn's dense rings.

  5. A COMPARISON OF AEROSOL OPTICAL DEPTH SIMULATED USING CMAQ WITH SATELLITE ESTIMATES

    EPA Science Inventory

    Satellite data provide new opportunities to study the regional distribution of particulate matter.

    The aerosol optical depth (AOD) - a derived estimate from the satellite-measured radiance, can be compared against model estimates to provide an evaluation of the columnar ae...

  6. Relative skills of soil moisture and vegetation optical depth retrievals for agricultural drought monitoring

    USDA-ARS?s Scientific Manuscript database

    Soil moisture condition is an important indicator for agricultural drought monitoring. Through the Land Parameter Retrieval Model (LPRM), vegetation optical depth (VOD) as well as surface soil moisture (SM) can be retrieved simultaneously from brightness temperature observations from the Advanced Mi...

  7. Aerosol optical depth as observed by the Mars Science Laboratory REMS UV photodiodes

    NASA Astrophysics Data System (ADS)

    Smith, Michael D.; Zorzano, María-Paz; Lemmon, Mark; Martín-Torres, Javier; Mendaza de Cal, Teresa

    2016-12-01

    Systematic observations taken by the REMS UV photodiodes on a daily basis throughout the landed Mars Science Laboratory mission provide a highly useful tool for characterizing aerosols above Gale Crater. Radiative transfer modeling is used to model the approximately 1.75 Mars Years of observations taken to date taking into account multiple scattering from aerosols and the extended field of view of the REMS UV photodiodes. The retrievals show in detail the annual cycle of aerosol optical depth, which is punctuated with numerous short timescale events of increased optical depth. Dust deposition onto the photodiodes is accounted for by comparison with aerosol optical depth derived from direct imaging of the Sun by Mastcam. The effect of dust on the photodiodes is noticeable, but does not dominate the signal. Cleaning of dust from the photodiodes was observed in the season around Ls=270°, but not during other seasons. Systematic deviations in the residuals from the retrieval fit are indicative of changes in aerosol effective particle size, with larger particles present during periods of increased optical depth. This seasonal dependence of aerosol particle size is expected as dust activity injects larger particles into the air, while larger aerosols settle out of the atmosphere more quickly leading to a smaller average particle size over time.

  8. Aerosol Optical Depth as Observed by the Mars Science Laboratory REMS UV Photodiodes

    NASA Astrophysics Data System (ADS)

    Smith, M. D.; Zorzano, M. P.; Lemmon, M. T.; Martín-Torres, J.; Mendaza de Cal, T.

    2016-12-01

    Systematic observations taken by the REMS UV photodiodes on a daily basis throughout the landed Mars Science Laboratory mission provide a highly useful tool for characterizing aerosols above Gale Crater. Radiative transfer modeling is used to model the more than two Mars Years of observations taken to date taking into account multiple scattering from aerosols and the extended field of view of the REMS UV photodiodes. The retrievals show in detail the annual cycle of aerosol optical depth, which is punctuated with numerous short timescale events of increased optical depth. Dust deposition onto the photodiodes is accounted for by comparison with aerosol optical depth derived from direct imaging of the Sun by Mastcam. The effect of dust on the photodiodes is noticeable, but does not dominate the signal. Cleaning of dust from the photodiodes was observed in the season around Ls=270°, but not during other seasons. Systematic deviations in the residuals from the retrieval fit are indicative of changes in aerosol effective particle size, with larger particles present during periods of increased optical depth. This seasonal dependence of aerosol particle size is expected as dust activity injects larger particles into the air, while larger aerosols settle out of the atmosphere more quickly leading to a smaller average particle size over time.

  9. Correction to “Hyperspectral Aerosol Optical Depths from TCAP Flights”

    SciTech Connect

    Shinozuka, Yohei; Johnson, Roy R.; Flynn, Connor J.; Russell, P. B.; Schmid, Beat; Redemann, Jens; Dunagan, Stephen; Kluzek, Celine D.; Hubbe, John M.; Segal-Rosenheimer, Michal; Livingston, J. M.; Eck, T.; Wagener, Richard; Gregory, L.; Chand, Duli; Berg, Larry K.; Rogers, Ray; Ferrare, R. A.; Hair, John; Hostetler, Chris A.; Burton, S. P.

    2014-02-16

    In the paper “Hyperspectral aerosol optical depths from TCAP flights” by Y. Shinozuka et al. (Journal of Geophysical Research: Atmospheres, 118, doi:10.1002/2013JD020596, 2013), Tables 1 and 2 were published with the column heads out of order. Tables 1 and 2 are published correctly here. The publisher regrets the error.

  10. Effects of Aerosol Optical Depth on diffuse UV and visible radiation

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Kim, J.; Cho, H.; Kim, Y.

    2007-12-01

    Ultraviolet radiation (UV, 300-367nm) was measured with a UV-multifilter rotating shadowband radiometer (UV- MFRSR) at Yonsei University, Seoul (37.57°N, 126.97°) for 7 months from January to July 2006 and visible irradiance (400-700 nm) also measured with a MFRSR for 12 months of 2006 at the same station. Spectral UV_AOD and vis_AOD were retrieved using the Langley method and Beer-Bouguer-Lambert's law, and compared with AOD obtained from Skyradiometer to validate their values. The diffuse and direct irradiance were analyzed to investigate the dependence on total optical depth (TOD) and aerosol optical depth (AOD). The direct-horizontal solar irradiance decreases exponentially as the optical depth increases according to the Beer- Bouguer-Lambert's Law. As the TOD and AOD increase, the diffuse-horizontal UV radiation gradually increases and shows a maximum value at some critical optical depth for a given SZA. Similar analysis was performed on the relation between the diffuse irradiance and AOD. RAF(radiation amplification factor) was used to correct the ozone effects on UV. These results provide empirical equations for the amount of diffuse irradiance in UV and visible wavelengths.

  11. INTEGRATING LIDAR AND SATELLITE OPTICAL DEPTH WITH AMBIENT MONITORING FOR 3-DIMENSIONAL PARTICULATE CHARACTERIZATION

    EPA Science Inventory

    A combination of in-situ PM2.5, sunphotometers, upward pointing lidar and satellite aerosol optical depth (AOD) instruments have been employed to better understand variability in the correlation between AOD and PM2.5 at the surface. Previous studies have shown good correlation be...

  12. INTEGRATING LIDAR AND SATELLITE OPTICAL DEPTH WITH AMBIENT MONITORING FOR 3-DIMENSIONAL PARTICULATE CHARACTERIZATION

    EPA Science Inventory

    A combination of in-situ PM2.5, sunphotometers, upward pointing lidar and satellite aerosol optical depth (AOD) instruments have been employed to better understand variability in the correlation between AOD and PM2.5 at the surface. Previous studies have shown good correlation be...

  13. Empirical Relationship between particulate matter and Aerosol Optical Depth over Northern Tien-Shan, Central Asia

    EPA Science Inventory

    Measurements were obtained at two sites in northern Tien-Shan in Central Asia during a 1-year period beginning July 2008 to examine the statistical relationship between aerosol optical depth (AOD) and of fine [PM2.5, particles less than 2.5 μm aerodynamic diameter (AD)] and coars...

  14. Empirical Relationship between particulate matter and Aerosol Optical Depth over Northern Tien-Shan, Central Asia

    EPA Science Inventory

    Measurements were obtained at two sites in northern Tien-Shan in Central Asia during a 1-year period beginning July 2008 to examine the statistical relationship between aerosol optical depth (AOD) and of fine [PM2.5, particles less than 2.5 μm aerodynamic diameter (AD)] and coars...

  15. Total ozone and aerosol optical depths inferred from radiometric measurements in the Chappuis absorption band

    SciTech Connect

    Flittner, D.E.; Herman, B.M.; Thome, K.J.; Simpson, J.M.; Reagan, J.A. )

    1993-04-15

    A second-derivative smoothing technique, commonly used in inversion work, is applied to the problem of inferring total columnar ozone amounts and aerosol optical depths. The application is unique in that the unknowns (i.e., total columnar ozone and aerosol optical depth) may be solved for directly without employing standard inversion methods. It is shown, however, that by employing inversion constraints, better solutions are normally obtained. The current method requires radiometric measurements of total optical depth through the Chappuis ozone band. It assumes no a priori shape for the aerosol optical depth versus wavelength profile and makes no assumptions about the ozone amount. Thus, the method is quite versatile and able to deal with varying total ozone and various aerosol size distributions. The technique is applied first in simulation, then to 119 days of measurements taken in Tucson, Arizona, that are compared to TOMS values for the same dates. The technique is also applied to two measurements taken at Mauna Loa, Hawaii, for which Dobson ozone values are available in addition to the TOMS values, and the results agree to within 15%. It is also shown through simulations that additional information can be obtained from measurements outside the Chappuis band. This approach reduces the bias and spread of the estimates total ozone and is unique in that it uses measurements from both the Chappuis and Huggins absorption bands. 12 refs., 6 figs., 2 tabs.

  16. Aerosol Optical Depth as Observed by the Mars Science Laboratory REMS UV Photodiodes

    NASA Technical Reports Server (NTRS)

    Smith, M. D.; Zorzano, M.-P.; Lemmon, M.; Martin-Torres, J.; Mendaza de Cal, T.

    2017-01-01

    Systematic observations taken by the REMS UV photodiodes on a daily basis throughout the landed Mars Science Laboratory mission provide a highly useful tool for characterizing aerosols above Gale Crater. Radiative transfer modeling is used to model the approximately two Mars Years of observations taken to date taking into account multiple scattering from aerosols and the extended field of view of the REMS UV photodiodes. The retrievals show in detail the annual cycle of aerosol optical depth, which is punctuated with numerous short timescale events of increased optical depth. Dust deposition onto the photodiodes is accounted for by comparison with aerosol optical depth derived from direct imaging of the Sun by Mastcam. The effect of dust on the photodiodes is noticeable, but does not dominate the signal. Cleaning of dust from the photodiodes was observed in the season around Ls=270deg, but not during other seasons. Systematic deviations in the residuals from the retrieval fit are indicative of changes in aerosol effective particle size, with larger particles present during periods of increased optical depth. This seasonal dependence of aerosol particle size is expected as dust activity injects larger particles into the air, while larger aerosols settle out of the atmosphere more quickly leading to a smaller average particle size over time. A full description of these observations, the retrieval algorithm, and the results can be found in Smith et al. (2016).

  17. Research on the high-precision non-contact optical detection technology for banknotes

    NASA Astrophysics Data System (ADS)

    Jin, Xiaofeng; Liang, Tiancai; Luo, Pengfeng; Sun, Jianfeng

    2015-09-01

    The technology of high-precision laser interferometry was introduced for optical measurement of the banknotes in this paper. Taking advantage of laser short wavelength and high sensitivity, information of adhesive tape and cavity about the banknotes could be checked efficiently. Compared with current measurement devices, including mechanical wheel measurement device, Infrared measurement device, ultrasonic measurement device, the laser interferometry measurement has higher precision and reliability. This will improve the ability of banknotes feature information in financial electronic equipment.

  18. A study on ultra-precision machining technique for Al6061-T6 to fabricate space infrared optics

    NASA Astrophysics Data System (ADS)

    Ryu, Geun-man; Lee, Gil-jae; Hyun, Sang-won; Sung, Ha-yeong; Chung, Euisik; Kim, Geon-hee

    2014-08-01

    In this paper, analysis of variance on designed experiments with full factorial design was applied to determine the optimized machining parameters for ultra-precision fabrication of the secondary aspheric mirror, which is one of the key elements of the space cryogenic infrared optics. A single point diamond turning machine (SPDTM, Nanotech 4μpL Moore) was adopted to fabricate the material, AL6061-T6, and the three machining parameters of cutting speed, feed rate and depth of cut were selected. With several randomly assigned experimental conditions, surface roughness of each condition was measured by a non-contact optical profiler (NT2000; Vecco). As a result of analysis using Minitab, the optimum cutting condition was determined as following; cutting speed: 122 m/min, feed rate: 3 mm/min and depth of cut: 1 μm. Finally, a 120 mm diameter aspheric secondary mirror was attached to a particularly designed jig by using mixture of paraffin and wax and successfully fabricated under the optimum machining parameters. The profile of machined surface was measured by a high-accuracy 3-D profilometer(UA3P; Panasonic) and we obtained the geometrical errors of 30.6 nm(RMS) and 262.4 nm(PV), which satisfy the requirements of the space cryogenic infrared optics.

  19. Development of Wet-Etching Tools for Precision Optical Figuring

    SciTech Connect

    Rushford, M C; Dixit, S N; Hyde, R; Britten, J A; Nissen, J; Aasen, M; Toeppen, J; Hoaglan, C; Nelson, C; Summers, L; Thomas, I

    2004-01-27

    This FY03 final report on Wet Etch Figuring involves a 2D thermal tool. Its purpose is to flatten (0.3 to 1 mm thickness) sheets of glass faster thus cheaper than conventional sub aperture tools. An array of resistors on a circuit board was used to heat acid over the glass Optical Path Difference (OPD) thick spots and at times this heating extended over the most of the glass aperture. Where the acid is heated on the glass it dissolves faster. A self-referencing interferometer measured the glass thickness, its design taking advantage of the parallel nature and thinness of these glass sheets. This measurement is used in close loop control of the heating patterns of the circuit board thus glass and acid. Only the glass and acid were to be moved to make the tool logistically simple to use in mass production. A set of 4-circuit board, covering 80 x 80-cm aperture was ordered, but only one 40 x 40-cm board was put together and tested for this report. The interferometer measurement of glass OPD was slower than needed on some glass profiles. Sometimes the interference fringes were too fine to resolve which would alias the sign of the glass thickness profile. This also caused the phase unwrapping code (FLYNN) to struggle thus run slowly at times taking hours, for a 10 inch square area. We did extensive work to improve the speed of this code. We tried many different phase unwrapping codes. Eventually running (FLYNN) on a farm of networked computers. Most of the work reported here is therefore limited to a 10-inch square aperture. Researched into fabricating a better interferometer lens from Plexiglas so to have less of the scattered light issues of Fresnel lens groves near field scattering patterns, this set the Nyquest limit. There was also a problem with the initial concept of wetting the 1737 glass on its bottom side with acid. The wetted 1737 glass developed an Achromatic AR coating, spoiling the reflection needed to see glass thickness interference fringes. In response

  20. PAH 8μm Emission as a Diagnostic of HII Region Optical Depth

    NASA Astrophysics Data System (ADS)

    Oey, M. S.; Lopez-Hernandez, J.; Kellar, J. A.; Pellegrini, E. W.; Gordon, Karl D.; Jameson, Katherine; Li, Aigen; Madden, Suzanne C.; Meixner, Margaret; Roman-Duval, Julia; Bot, Caroline; Rubio, Monica; Tielens, A. G. G. M.

    2017-01-01

    PAHs are easily destroyed by Lyman continuum radiation and so in optically thick Stromgren spheres, they tend to be found only on the periphery of HII regions, rather than in the central volume. We therefore expect that in HII regions that are optically thin to ionizing radiation, PAHs would be destroyed beyond the primary nebular structure. Using data from the Spitzer SAGE survey of the Magellanic Clouds, we test whether 8 μm emission can serve as a diagnostic of optical depth in HII regions. We find that 8 μm emission does provide valuable constraints in the Large Magellanic Cloud, where objects identified as optically thick by their atomic ionization structure have 6 times higher median 8 μm surface brightness than optically thin objects. However, in the Small Magellanic Cloud, this differentiation is not observed. This appears to be caused by extremely low PAH production in this low-metallicity environment, such that any differentiation between optically thick and thin objects is washed out by stochastic variations, likely driven by the interplay between dust production and UV destruction. Thus, PAH emission is sensitive to nebular optical depth only at higher metallicities.

  1. Fabrication and Assembly of High-Precision Hinge and Latch Joints for Deployable Optical Instruments

    NASA Technical Reports Server (NTRS)

    Phelps, James E.

    1999-01-01

    Descriptions are presented of high-precision hinge and latch joints that have been co-developed, for application to deployable optical instruments, by NASA Langley Research Center and Nyma/ADF. Page-sized versions of engineering drawings are included in two appendices to describe all mechanical components of both joints. Procedures for assembling the mechanical components of both joints are also presented. The information herein is intended to facilitate the fabrication and assembly of the high-precision hinge and latch joints, and enable the incorporation of these joints into the design of deployable optical instrument systems.

  2. Optical-precision alignment of diffraction grating mold in moire interferometry

    NASA Technical Reports Server (NTRS)

    Joh, D.

    1992-01-01

    A high-precision optical method is presented for aligning diffraction grating molds with the edges of specimens in moire interferometry. The alignment fixture is simple and convenient to operate. The conventional method of grating-mold alignment has a wide band of uncertainty in the range of error which is not compatible with the required precision of high-sensitivity moire interferometry. Following a description of the alignment technique, both the single-edge and parallel-edge guide bar optical alignment methods are introduced and compared.

  3. Optical-precision alignment of diffraction grating mold in moire interferometry

    NASA Technical Reports Server (NTRS)

    Joh, D.

    1992-01-01

    A high-precision optical method is presented for aligning diffraction grating molds with the edges of specimens in moire interferometry. The alignment fixture is simple and convenient to operate. The conventional method of grating-mold alignment has a wide band of uncertainty in the range of error which is not compatible with the required precision of high-sensitivity moire interferometry. Following a description of the alignment technique, both the single-edge and parallel-edge guide bar optical alignment methods are introduced and compared.

  4. High-resolution in-depth imaging of optically cleared thick samples using an adaptive SPIM

    PubMed Central

    Masson, Aurore; Escande, Paul; Frongia, Céline; Clouvel, Grégory; Ducommun, Bernard; Lorenzo, Corinne

    2015-01-01

    Today, Light Sheet Fluorescence Microscopy (LSFM) makes it possible to image fluorescent samples through depths of several hundreds of microns. However, LSFM also suffers from scattering, absorption and optical aberrations. Spatial variations in the refractive index inside the samples cause major changes to the light path resulting in loss of signal and contrast in the deepest regions, thus impairing in-depth imaging capability. These effects are particularly marked when inhomogeneous, complex biological samples are under study. Recently, chemical treatments have been developed to render a sample transparent by homogenizing its refractive index (RI), consequently enabling a reduction of scattering phenomena and a simplification of optical aberration patterns. One drawback of these methods is that the resulting RI of cleared samples does not match the working RI medium generally used for LSFM lenses. This RI mismatch leads to the presence of low-order aberrations and therefore to a significant degradation of image quality. In this paper, we introduce an original optical-chemical combined method based on an adaptive SPIM and a water-based clearing protocol enabling compensation for aberrations arising from RI mismatches induced by optical clearing methods and acquisition of high-resolution in-depth images of optically cleared complex thick samples such as Multi-Cellular Tumour Spheroids. PMID:26576666

  5. Microlensing Optical Depth towards the Galactic Bulge Using Clump Giants from the MACHO Survey

    SciTech Connect

    Popowski, P; Griest, K; Thomas, C L; Cook, K H; Bennett, D P; Becker, A C; Alves, D R; Minniti, D; Drake, A J; Alcock, C; Allsman, R A; Axelrod, T S; Freeman, K C; Geha, M; Lehner, M J; Marshall, S L; Nelson, C A; Peterson, B A; Quinn, P J; Stubbs, C W; Sutherland, W; Vandehei, T; Welch, D

    2005-07-14

    Using 7 years of MACHO survey data, we present a new determination of the optical depth to microlensing towards the Galactic bulge. We select the sample of 62 microlensing events (60 unique) on clump giant sources and perform a detailed efficiency analysis. We use only the clump giant sources because these are bright bulge stars and are not as strongly affected by blending as other events. Using a subsample of 42 clump events concentrated in an area of 4.5 deg{sup 2} with 739000 clump giant stars, we find {tau} = 2.17{sub -0.38}{sup +0.47} x 10{sup -6} at (l,b) = (1{sup o}.50, -2{sup o}.68), somewhat smaller than found in most previous MACHO studies, but in excellent agreement with recent theoretical predictions. We also present the optical depth in each of the 19 fields in which we detected events, and find limits on optical depth for fields with no events. The errors in optical depth in individual fields are dominated by Poisson noise. We measure optical depth gradients of (1.06 {+-} 0.71) x 10{sup -6}deg{sup -1} and (0.29 {+-} 0.43) x 10{sup -6}deg{sup -1} in the galactic latitude b and longitude l directions, respectively. Finally, we discuss the possibility of anomalous duration distribution of events in the field 104 centered on (l,b) = (3{sup o}.11, -3{sup o}.01) as well as investigate spatial clustering of events in all fields.

  6. Cloud-free aerosol optical depth determination over oceans from satellite radiometry

    SciTech Connect

    Wagener, R.; Nemesure, S.; Benkovitz, C.M.; Schwartz, S.E.; Berkowitz, C.M.; Ghan, S.J.

    1993-06-01

    Shortwave radiative forcing of climate by anthropogenic sulfate aerosol has been estimated to be of comparable global-average magnitude, but opposite sign, to longwave forcing by greenhouse gases (Charlson et al., 1992). It is therefore important that this forcing be accurately represented in climate models. Sulfate concentrations calculated by a Global Chemistry Model driven by operational meteorological data (GChM; Benkovitz et al., this meeting) exhibit high spatial and temporal variations that closely reproduce observations at continental sites. However, because of the sparsity of sulfate concentration measurements over oceans, aerosol optical depth determinations from satellite data are needed to evaluate the performance of the model over oceans. Previous studies of aerosol optical depths over oceans have employed Advanced Very High Resolution Radiometer Global Area Coverage (AVHRR GAC) data (Rao et al., 1989; Durkee et al., 1991) that should yield the required information, but the emphasis in these studies has been to produce wide spatial coverage by time averaging for periods of a week to a month, thereby masking the high spatial and temporal variability associated with the data and required for model evaluation. The Rao et al. method is employed in the production of the weekly composite aerosol maps by NOAA since June 1987. The authors report results obtained with a modified Durkee algorithm that provides instantaneous optical depths averaged over individual GChM model grid cells (1.125{degrees} x 1.125{degrees}) for comparison with optical depths predicted by the chemistry model at the same times and places (Berkowitz et al., this meeting). The optical depth retrieval is improved by a more accurate removal of sun-glint contamination, using the formulation of (Cox and Munk, 1956) for sun-glint probability as a function of wind speed, together with the wind speeds available from the operational meteorological data used to drive the chemistry model.

  7. Analytic Inversion of Emission Lines of Arbitrary Optical Depth for the Structure of Supernova Ejecta

    NASA Astrophysics Data System (ADS)

    Ignace, R.; Hendry, M. A.

    2000-07-01

    We derive a method for inverting emission-line profiles formed in supernova ejecta. The derivation assumes spherical symmetry and homologous expansion [i.e., v(r)~r], is analytic, and even takes account of occultation by a pseudophotosphere. Previous inversion methods have been developed that are restricted to optically thin lines, but the particular case of homologous expansion permits an analytic result for lines of arbitrary optical depth. In fact, we show that the quantity that is generically retrieved is the run of line intensity Iλ with radius in the ejecta. This result is quite general and so could be applied to resonance lines, recombination lines, etc. As a specific example, we show how to derive the run of (Sobolev) optical depth τλ with radius in the case of a pure resonance scattering emission line.

  8. In vivo analysis of glaucoma-related features within the optic nerve head using enhanced depth imaging optical coherence tomography.

    PubMed

    Prata, Tiago S; Lopes, Flavio S; Prado, Vitor G; Almeida, Izabela; Matsubara, Igor; Dorairaj, Syril; Furlanetto, Rafael L; Vessani, Roberto M; Paranhos, Augusto

    2017-01-01

    Structural differences between optic nerve head (ONH) parameters in glaucomatous and non-glaucomatous eyes has been documented, however the association between such parameters in patients with different disease stages is yet to be elucidated. We investigated the relationship between different laminar and prelaminar ONH structures using enhanced depth imaging spectral-domain optical coherence tomography (EDI OCT) in a population with and without glaucoma. In this observational case-control study, we prospectively enrolled healthy individuals and glaucomatous patients with different disease stages. All participants underwent EDI OCT imaging (Heidelberg Engineering). Following ONH parameters were measured on serial vertical B-scans by two examiners masked to patient's clinical data: lamina cribrosa (LC) and prelaminar neural tissue (PLNT) thicknesses, Bruch's membrane opening (BMO) and cup depth. Associations between cup depth, and laminar and prelaminar parameters were evaluated controlling for possible confounding factors such as axial length and disc size. Sixty-four eyes of 64 patients were included (30 with glaucoma and 34 controls). Eyes with glaucoma had significantly lower mean LC and PLNT thickness, and greater mean cup depth than controls (p<0.01). There was a significant negative association between PLNT thickness and cup depth in glaucomatous eyes (R2 = 0.158, p = 0.029). In addition, LC thickness correlated significantly with cup depth (R2 = 0.135, p = 0.045). Eyes with thinner LCs presented deeper cups. Overall, cup depth and BMO had the best and LC thickness had the worst intraobserver and interobserver reproducibility grading. In conclusion, significant associations were seen between cup depth, LC and PLNT thickness. Eyes with deeper cups not only had less neural tissue, but also thinner LCs, independent of disc size and axial length. Best reproducibility was found for prelaminar parameters compared to deeper ONH structures.

  9. Extending the effective imaging depth in spectral domain optical coherence tomography by dual spatial frequency encoding

    NASA Astrophysics Data System (ADS)

    Wu, Tong; Wang, Qingqing; Liu, Youwen; Wang, Jiming

    2016-03-01

    We present a spatial frequency domain multiplexing method for extending the imaging depth range of a SDOCT system without any expensive device. This method uses two reference arms with different round-trip optical delay to probe different depth regions within the sample. Two galvo scanners with different pivot-offset distances in the reference arms are used for spatial frequency modulation and multiplexing. While simultaneously driving the galvo scanners in the reference arms and the sample arm, the spatial spectrum of the acquired two-dimensional OCT spectral interferogram corresponding to the shallow and deep depth of the sample will be shifted to the different frequency bands in the spatial frequency domain. After data filtering, image reconstruction and fusion the spatial frequency multiplexing SDOCT system can provide an approximately 1.9 fold increase in the effective ranging depth compared with that of a conventional single-reference-arm full-range SDOCT system.

  10. Depth-resolved multimodal imaging: Wavelength modulated spatially offset Raman spectroscopy with optical coherence tomography.

    PubMed

    Chen, Mingzhou; Mas, Josep; Forbes, Lindsey H; Andrews, Melissa R; Dholakia, Kishan

    2017-07-13

    A major challenge in biophotonics is multimodal imaging to obtain both morphological and molecular information at depth. We demonstrate a hybrid approach integrating optical coherence tomography (OCT) with wavelength modulated spatially offset Raman spectroscopy (WM-SORS). With depth colocalization obtained from the OCT, we can penetrate 1.2-mm deep into strong scattering media (lard) to acquire up to a 14-fold enhancement of a Raman signal from a hidden target (polystyrene) with a spatial offset. Our approach is capable of detecting both Raman and OCT signals for pharmaceutical particles embedded in turbid media and revealing the white matter at depth within a 0.6-mm thick brain tissue layer. This depth resolved label-free multimodal approach is a powerful route to analyze complex biomedical samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Engineering Stark Potentials for Precision Measurements: Optical Lattice Clock and Electrodynamic Surface Trap

    SciTech Connect

    Katori, Hidetoshi; Takamoto, Masao; Hachisu, Hidekazu; Fujiki, Jun; Higashi, Ryoichi; Yasuda, Masami; Kishimoto, Tetsuo

    2005-05-05

    Employing the engineered electric fields, we demonstrate novel platforms for precision measurements with neutral atoms. (1) Applying the light shift cancellation technique, atoms trapped in an optical lattice reveal 50-Hz-narrow optical spectrum, yielding nearly an order of magnitude improvement over existing neutral-atom-based clocks. (2) Surface Stark trap has been developed to manipulate scalar atoms that are intrinsically robust to decoherence.

  12. Flexible, non-contact and high-precision measurements of optical components

    NASA Astrophysics Data System (ADS)

    Beutler, A.

    2016-06-01

    A high-accuracy cylindrical coordinate measuring instrument developed for the measurement of optical components is presented. It is equipped with an optical point sensor system including a high aperture probe. This setup allows measurements to be performed with high accuracy in a flexible way. Applications include the measurement of the topography of high-precision aspheric and freeform lenses and diffractive structures. High measuring speeds guarantee the implementation in a closed-loop production process.

  13. Simulation of miniature optical correlator for future generation of spacecraft precision landing

    NASA Astrophysics Data System (ADS)

    Zhou, Hanying; Chao, Tien-Hsin; Martin, Bryan J.; Villaume, Nate

    2003-08-01

    Future Mars/planets explorations call for precision and even pinpoint landing. Low cost optical correlator is one of the promising enabling technologies for pinpoint landing. JPL has developed a state-of-the-art miniature optical correlator (MOC) to demonstrate its feasibility. In this paper, we describe a simulation testbed under development for measuring MOC"s performance in a high-fidelity entry, descent, and landing environment, and provide our preliminary simulation result.

  14. Precision Narrow-Angle Astrometry of Binary Stars with the Navy Prototype Optical Interferometer

    DTIC Science & Technology

    2004-01-01

    precision into accuracy. Keywords: Optical interferometry, interferometric imaging, NPOI, binary stars, extrasolar planets 1. MOTIVATION As Michelson realized...interferometry, are equivalent to using ≈ 0.5(d/r0)2 baselines, where d is the telescope diameter and r0 is the Fried parameter. Extrasolar planet searches of...Dubarry Ave., Lanham, MD 20706, USA; ABSTRACT The Navy Prototype Optical Interferometry (NPOI) group has started an astrometric search for planets in

  15. Micro-optical fabrication by ultraprecision diamond machining and precision molding

    NASA Astrophysics Data System (ADS)

    Li, Hui; Li, Likai; Naples, Neil J.; Roblee, Jeffrey W.; Yi, Allen Y.

    2017-06-01

    Ultraprecision diamond machining and high volume molding for affordable high precision high performance optical elements are becoming a viable process in optical industry for low cost high quality microoptical component manufacturing. In this process, first high precision microoptical molds are fabricated using ultraprecision single point diamond machining followed by high volume production methods such as compression or injection molding. In the last two decades, there have been steady improvements in ultraprecision machine design and performance, particularly with the introduction of both slow tool and fast tool servo. Today optical molds, including freeform surfaces and microlens arrays, are routinely diamond machined to final finish without post machining polishing. For consumers, compression molding or injection molding provide efficient and high quality optics at extremely low cost. In this paper, first ultraprecision machine design and machining processes such as slow tool and fast too servo are described then both compression molding and injection molding of polymer optics are discussed. To implement precision optical manufacturing by molding, numerical modeling can be included in the future as a critical part of the manufacturing process to ensure high product quality.

  16. Depth-correction algorithm that improves optical quantification of large breast lesions imaged by diffuse optical tomography

    PubMed Central

    Tavakoli, Behnoosh; Zhu, Quing

    2011-01-01

    Optical quantification of large lesions imaged with diffuse optical tomography in reflection geometry is depth dependence due to the exponential decay of photon density waves. We introduce a depth-correction method that incorporates the target depth information provided by coregistered ultrasound. It is based on balancing the weight matrix, using the maximum singular values of the target layers in depth without changing the forward model. The performance of the method is evaluated using phantom targets and 10 clinical cases of larger malignant and benign lesions. The results for the homogenous targets demonstrate that the location error of the reconstructed maximum absorption coefficient is reduced to the range of the reconstruction mesh size for phantom targets. Furthermore, the uniformity of absorption distribution inside the lesions improve about two times and the median of the absorption increases from 60 to 85% of its maximum compared to no depth correction. In addition, nonhomogenous phantoms are characterized more accurately. Clinical examples show a similar trend as the phantom results and demonstrate the utility of the correction method for improving lesion quantification. PMID:21639570

  17. Terminal speed of a gaseous stratus with finite optical depth over a luminous flat source

    NASA Astrophysics Data System (ADS)

    Masuda, Takao; Fukue, Jun

    2016-06-01

    We reexamine the terminal speed of a moving stratus irradiated by an infinite flat source, considering relativistic radiative transfer in the stratus. For the case of a particle, V. Icke (1989, A&A, 216, 294) analytically derived the terminal speed of (4-√{7})c/3 ˜ 0.45 c, whereas the terminal speed of a stratus with finite optical depth is calculated under the Eddington approximation (J. Fukue, 2014, PASJ, 66, 13), and becomes larger up to 0.7 c in the optically thin limit. In this paper, we numerically calculate radiative transfer in the stratus without the Eddington approximation, and obtain the terminal speed. In the optically thick limit the terminal speed approaches 0.47 c. In the optically thin limit, in contrast to the previous analytical study, it becomes small as the optical depth decreases, and approaches 0.26 c. This is due to the anisotropic effect of the radiation field in the optically thin regime.

  18. An Optical Fibre Depth (Pressure) Sensor for Remote Operated Vehicles in Underwater Applications.

    PubMed

    Duraibabu, Dinesh Babu; Poeggel, Sven; Omerdic, Edin; Capocci, Romano; Lewis, Elfed; Newe, Thomas; Leen, Gabriel; Toal, Daniel; Dooly, Gerard

    2017-02-19

    A miniature sensor for accurate measurement of pressure (depth) with temperature compensation in the ocean environment is described. The sensor is based on an optical fibre Extrinsic Fabry-Perot interferometer (EFPI) combined with a Fibre Bragg Grating (FBG). The EFPI provides pressure measurements while the Fibre Bragg Grating (FBG) provides temperature measurements. The sensor is mechanically robust, corrosion-resistant and suitable for use in underwater applications. The combined pressure and temperature sensor system was mounted on-board a mini remotely operated underwater vehicle (ROV) in order to monitor the pressure changes at various depths. The reflected optical spectrum from the sensor was monitored online and a pressure or temperature change caused a corresponding observable shift in the received optical spectrum. The sensor exhibited excellent stability when measured over a 2 h period underwater and its performance is compared with a commercially available reference sensor also mounted on the ROV. The measurements illustrates that the EFPI/FBG sensor is more accurate for depth measurements (depth of ~0.020 m).

  19. Fiber-optic annular detector array for large depth of field photoacoustic macroscopy.

    PubMed

    Bauer-Marschallinger, Johannes; Höllinger, Astrid; Jakoby, Bernhard; Burgholzer, Peter; Berer, Thomas

    2017-03-01

    We report on a novel imaging system for large depth of field photoacoustic scanning macroscopy. Instead of commonly used piezoelectric transducers, fiber-optic based ultrasound detection is applied. The optical fibers are shaped into rings and mainly receive ultrasonic signals stemming from the ring symmetry axes. Four concentric fiber-optic rings with varying diameters are used in order to increase the image quality. Imaging artifacts, originating from the off-axis sensitivity of the rings, are reduced by coherence weighting. We discuss the working principle of the system and present experimental results on tissue mimicking phantoms. The lateral resolution is estimated to be below 200 μm at a depth of 1.5 cm and below 230 μm at a depth of 4.5 cm. The minimum detectable pressure is in the order of 3 Pa. The introduced method has the potential to provide larger imaging depths than acoustic resolution photoacoustic microscopy and an imaging resolution similar to that of photoacoustic computed tomography.

  20. An Optical Fibre Depth (Pressure) Sensor for Remote Operated Vehicles in Underwater Applications

    PubMed Central

    Duraibabu, Dinesh Babu; Poeggel, Sven; Omerdic, Edin; Capocci, Romano; Lewis, Elfed; Newe, Thomas; Leen, Gabriel; Toal, Daniel; Dooly, Gerard

    2017-01-01

    A miniature sensor for accurate measurement of pressure (depth) with temperature compensation in the ocean environment is described. The sensor is based on an optical fibre Extrinsic Fabry-Perot interferometer (EFPI) combined with a Fibre Bragg Grating (FBG). The EFPI provides pressure measurements while the Fibre Bragg Grating (FBG) provides temperature measurements. The sensor is mechanically robust, corrosion-resistant and suitable for use in underwater applications. The combined pressure and temperature sensor system was mounted on-board a mini remotely operated underwater vehicle (ROV) in order to monitor the pressure changes at various depths. The reflected optical spectrum from the sensor was monitored online and a pressure or temperature change caused a corresponding observable shift in the received optical spectrum. The sensor exhibited excellent stability when measured over a 2 h period underwater and its performance is compared with a commercially available reference sensor also mounted on the ROV. The measurements illustrates that the EFPI/FBG sensor is more accurate for depth measurements (depth of ~0.020 m). PMID:28218727

  1. MODA: a new algorithm to compute optical depths in multidimensional hydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Perego, Albino; Gafton, Emanuel; Cabezón, Rubén; Rosswog, Stephan; Liebendörfer, Matthias

    2014-08-01

    Aims: We introduce the multidimensional optical depth algorithm (MODA) for the calculation of optical depths in approximate multidimensional radiative transport schemes, equally applicable to neutrinos and photons. Motivated by (but not limited to) neutrino transport in three-dimensional simulations of core-collapse supernovae and neutron star mergers, our method makes no assumptions about the geometry of the matter distribution, apart from expecting optically transparent boundaries. Methods: Based on local information about opacities, the algorithm figures out an escape route that tends to minimize the optical depth without assuming any predefined paths for radiation. Its adaptivity makes it suitable for a variety of astrophysical settings with complicated geometry (e.g., core-collapse supernovae, compact binary mergers, tidal disruptions, star formation, etc.). We implement the MODA algorithm into both a Eulerian hydrodynamics code with a fixed, uniform grid and into an SPH code where we use a tree structure that is otherwise used for searching neighbors and calculating gravity. Results: In a series of numerical experiments, we compare the MODA results with analytically known solutions. We also use snapshots from actual 3D simulations and compare the results of MODA with those obtained with other methods, such as the global and local ray-by-ray method. It turns out that MODA achieves excellent accuracy at a moderate computational cost. In appendix we also discuss implementation details and parallelization strategies.

  2. Regional Aerosol Optical Depth Characteristics from Satellite Observations: ACE-1, TARFOX and ACE-2 Results

    NASA Technical Reports Server (NTRS)

    Durkee, P. A.; Nielsen, K. E.; Smith, P. J.; Russell, P. B.; Schmid, B.; Livingston, J. M.; Holben, B. N.; Tomasi, C.; Vitale, V.; Collins, D.

    1999-01-01

    Analysis of the aerosol properties during 3 recent international field campaigns ACE-1, TARFOX and ACE-2 are described using satellite retrievals from NOAA AVHRR data. Validation of the satellite retrieval procedure is performed with airborne, shipboard, and land-based sunphotometry during ACE-2. The intercomparison between satellite and surface optical depths has a correlation coefficient of 0.93 for 630 nm wavelength and 0.92 for 860 nm wavelength, The standard error of estimate is 0.025 for 630 nm wavelength and 0.023 for 860 nm wavelength. Regional aerosol properties are examined in composite analysis of aerosol optical properties from the ACE-1, TARFOX and ACE-2 regions. ACE-1 and ACE-2 regions have strong modes in the distribution of optical depth around 0.1, but the ACE-2 tails toward higher values yielding an average of 0.16 consistent with pollution and dust aerosol intrusions. The TARFOX region has a noticeable mode of 0.2, but has significant spread of aerosol optical depth values consistent with the varied continental aerosol constituents off the eastern North American Coast.

  3. Freeform metrology using swept-source optical coherence tomography with custom pupil-relay precision scanning configuration

    NASA Astrophysics Data System (ADS)

    Yao, Jianing; Xu, Di; Zhao, Nan; Rolland, Jannick P.

    2015-10-01

    The recent advances in the optics manufacturing industry to achieve the capability of fabricating rotationally nonsymmetric optical quality surfaces have considerably stimulated the optical designs with freeform components. This opens up new horizons for novel optical systems with larger fields of view and higher performance, or significantly more compact in volume at equal performance compared to conventional systems. A bottleneck to the broad industrial applications of freeform optics remains the lack of a high performance optical metrology tool capable of measuring significant surface departures and slopes of the parts. To address this issue, we have developed a fiber-based swept-source optical coherence tomography (SS-OCT) system for point-cloud freeform metrology, where two-axis galvanometer scanners are leveraged for high-speed lateral scans. We specifically designed a custom all-reflective achromatic pupil relay system to achieve a diffraction-limited scanning configuration. Coupled with a large field-of-view (FOV) telecentric scan lens, the imaging covers 28.9 mm × 28.9 mm FOV with 35 μm lateral resolution and more than 600 μm depth of focus. Freeform metrology is demonstrated for an Alvarez surface of 400 μm surface sag. The high sensitivity of the SS-OCT system allows for capturing the slope variations of the part up to the maximum slope that is 5 degrees in this case. Specific surface reconstruction, rendering and fitting algorithms were developed to evaluate the metrology results and investigate the accuracy and precision of the measurements.

  4. Precision measurement of the nuclear polarization in laser-cooled, optically pumped 37K

    NASA Astrophysics Data System (ADS)

    Fenker, B.; Behr, J. A.; Melconian, D.; Anderson, R. M. A.; Anholm, M.; Ashery, D.; Behling, R. S.; Cohen, I.; Craiciu, I.; Donohue, J. M.; Farfan, C.; Friesen, D.; Gorelov, A.; McNeil, J.; Mehlman, M.; Norton, H.; Olchanski, K.; Smale, S.; Thériault, O.; Vantyghem, A. N.; Warner, C. L.

    2016-07-01

    We report a measurement of the nuclear polarization of laser-cooled, optically pumped 37K atoms which will allow us to precisely measure angular correlation parameters in the {β }+-decay of the same atoms. These results will be used to test the V - A framework of the weak interaction at high precision. At the Triumf neutral atom trap (Trinat), a magneto-optical trap confines and cools neutral 37K atoms and optical pumping spin-polarizes them. We monitor the nuclear polarization of the same atoms that are decaying in situ by photoionizing a small fraction of the partially polarized atoms and then use the standard optical Bloch equations to model their population distribution. We obtain an average nuclear polarization of \\bar{P}=0.9913+/- 0.0009, which is significantly more precise than previous measurements with this technique. Since our current measurement of the β-asymmetry has 0.2 % statistical uncertainty, the polarization measurement reported here will not limit its overall uncertainty. This result also demonstrates the capability to measure the polarization to \\lt 0.1 % , allowing for a measurement of angular correlation parameters to this level of precision, which would be competitive in searches for new physics.

  5. Precision measurement of the nuclear polarization in laser-cooled, optically pumped 37 K

    DOE PAGES

    Fenker, B.; Behr, J. A.; Melconian, D.; ...

    2016-07-13

    We report a measurement of the nuclear polarization of laser-cooled, optically pumped 37K atoms which will allow us to precisely measure angular correlation parameters in themore » $${\\beta }^{+}$$-decay of the same atoms. These results will be used to test the V ₋ A framework of the weak interaction at high precision. At the Triumf neutral atom trap (Trinat), a magneto-optical trap confines and cools neutral 37K atoms and optical pumping spin-polarizes them. We monitor the nuclear polarization of the same atoms that are decaying in situ by photoionizing a small fraction of the partially polarized atoms and then use the standard optical Bloch equations to model their population distribution. We obtain an average nuclear polarization of $$\\bar{P}=0.9913\\pm 0.0009$$, which is significantly more precise than previous measurements with this technique. Since our current measurement of the β-asymmetry has $$0.2 \\% $$ statistical uncertainty, the polarization measurement reported here will not limit its overall uncertainty. This result also demonstrates the capability to measure the polarization to $$\\lt 0.1 \\% $$, allowing for a measurement of angular correlation parameters to this level of precision, which would be competitive in searches for new physics.« less

  6. Precision evaluation of lens systems using a nodal slide/MTF optical bench

    NASA Astrophysics Data System (ADS)

    Doherty, Victor J.; Chapnik, Philip D.

    1992-01-01

    A compact, self-contained production instrument designed to permit the rapid and precise performance characterization of a wide variety of lenses and optical systems has been developed by Eidolon Corporation. The Eidolon Production Nodal Slide/MTF Measurement System can be used to measure effective focal length (EFL), distortion, field curvature, chromatic aberration, spot size, and modulation transfer function (MTF).

  7. Optical depth retrievals from Delta-T SPN1 measurements of broadband solar irradiance at ground

    NASA Astrophysics Data System (ADS)

    Estelles, Victor; Serrano, David; Segura, Sara; Wood, John; Webb, Nick

    2016-04-01

    The SPN1 radiometer, manufactured by Delta-T Devices Ltd., is an instrument designed for the measurement of global solar irradiance and its components (diffuse, direct) at ground level. In the present study, the direct irradiance component has been used to retrieve an effective total optical depth, by applying the Beer-Lambert law to the broadband measurements. The results have been compared with spectral total optical depths derived from two Cimel CE318 and Prede POM01 sun-sky radiometers, located at the Burjassot site in Valencia (Spain), during years 2013 - 2015. The SPN1 is an inexpensive and versatile instrument for the measurement of the three components of the solar radiation without any mobile part and without any need to azimuthally align the instrument to track the sun (http://www.delta-t.co.uk). The three components of the solar radiation are estimated from a combination of measurements performed by 7 different miniature thermopiles. In turn, the Beer-Lambert law has been applied to the broadband direct solar component to obtain an effective total optical depth, representative of the total extinction in the atmosphere. For the assessment of the total optical depth values retrieved with the SPN1, two different sun-sky radiometers (Cimel CE318 and Prede POM01L) have been employed. Both instruments belong to the international networks AERONET and SKYNET. The modified SUNRAD package has been applied in both Cimel and Prede instruments. Cloud affected data has been removed by applying the Smirnov cloud-screening procedure in the SUNRAD algorithm. The broadband SPN1 total optical depth has been analysed by comparison with the spectral total optical depth from the sun-sky radiometer measurements at wavelengths 440, 500, 675, 870 and 1020 nm. The slopes and intercepts have been estimated to be 0.47 - 0.98 and 0.055 - 0.16 with increasing wavelength. The average correlation coefficients and RMSD were 0.80 - 0.83 and 0.034 - 0.036 for all the channels. The

  8. Implications for GCM Modeling of MARCI/TES ACB Optical Depth Differences

    NASA Astrophysics Data System (ADS)

    Klassen, David R.; Kahre, Melinda A.; Wolff, Michael J.; Haberle, Robert; Hollingsworth, Jeffery L.

    2016-10-01

    The Aphelion Cloud Belt (ACB) is a well-studied phenomenon of Mars. HST violet images and microwave observations [e.g. 1-3] helped characterize its seasonal morphology and measure typical optical depths. Follow up, long-term studies by orbiting instruments [e.g. 4-6] characterized the growth and decline of the ACB as well as a baseline set of zonally averaged optical depths as a function of latitude and season. All this work provided ground-truth for the assessment and modification of Mars GCMs and current models provide good agreement with observations [e.g. 7-8].We will present recent analyses of MARCI and TES ACB optical depths that show a wavelength dependance on the timing of the peak zonal-average optical depth that implies a possible evolution in average effective radius of ACB cloud particles as the ACB ages. As we will show, this difference in timing of the optical depth peak between short and long wavelength bands is not seen in the Ames MGCM. In order to begin understanding these differences, we will present retrieved ACB cloud particle sizes from the Ames MGCM to compare to the optical depth observations and calculations and discuss possible model adjustments that may lead to better fits. Aligning model and observation results should lead to a better understanding of what is physically driving the particle size evolution.[1] James, P. B., et al. 1996, JGR, 101, 18883[2] Clancy, R. T., et al. 1996, Icarus, 122, 36[3] Wolff, M. J., et al. 1999, in The Fifth International Conference on Mars, July 19-24, 1999, Pasadena, California, 6173[4] Pearl, J. C., et al. 2001, JGR, 106, 12325[5] Smith, M. D., et al. 2003, JGR-Planets, 108, 1[6] Smith, M. D. 2004, Icarus, 167, 148[7] Montmessin, F., et al. 2004, JGR-Planets, 109, E10004[8] Haberle, R. M., et al. 2010, in BAAS, 42, 1031

  9. Depth-resolved holographic optical coherence imaging using a high-sensitivity photorefractive polymer device

    NASA Astrophysics Data System (ADS)

    Salvador, M.; Prauzner, J.; Köber, S.; Meerholz, K.; Jeong, K.; Nolte, D. D.

    2008-12-01

    We present coherence-gated holographic imaging using a highly sensitive photorefractive (PR) polymer composite as the recording medium. Due to the high sensitivity of the composite holographic recording at intensities as low as 5 mW/cm2 allowed for a frame exposure time of only 500ms. Motivated by regenerative medical applications, we demonstrate optical depth sectioning of a polymer foam for use as a cell culture matrix. An axial resolution of 18 μm and a transverse resolution of 30 μm up to a depth of 600 μm was obtained using an off-axis recording geometry.

  10. Diffuse optical microscopy for quantification of depth-dependent epithelial backscattering in the cervix

    NASA Astrophysics Data System (ADS)

    Bodenschatz, Nico; Lam, Sylvia; Carraro, Anita; Korbelik, Jagoda; Miller, Dianne M.; McAlpine, Jessica N.; Lee, Marette; Kienle, Alwin; MacAulay, Calum

    2016-06-01

    A fiber optic imaging approach is presented using structured illumination for quantification of almost pure epithelial backscattering. We employ multiple spatially modulated projection patterns and camera-based reflectance capture to image depth-dependent epithelial scattering. The potential diagnostic value of our approach is investigated on cervical ex vivo tissue specimens. Our study indicates a strong backscattering increase in the upper part of the cervical epithelium caused by dysplastic microstructural changes. Quantization of relative depth-dependent backscattering is confirmed as a potentially useful diagnostic feature for detection of precancerous lesions in cervical squamous epithelium.

  11. Three-dimensional optical metrology with color-coded extended depth of focus.

    PubMed

    Hasman, E; Keren, S; Davidson, N; Friesem, A A

    1999-04-01

    A novel method of rapid three-dimensional optical metrology that is based on triangulation of a configuration of color-coded light stripes is presented. The method exploits polychromatic illumination and a combined diffractive-refractive element, so the incident light is focused upon a stripe that is axially dispersed, greatly increasing the depth-measuring range without any decrease in the axial or the lateral resolution. The discrimination of each color stripe is further improved by spectral coding and decoding techniques. An 18-fold increase in the depth of focus was experimentally obtained while diffraction-limited light stripes were completely maintained.

  12. Measurement of different types of optical loss using high-precision laser photometer

    NASA Astrophysics Data System (ADS)

    Cao, Zhen; Hu, Guohang; He, Hongbo; Zhao, Yuanan; Wang, Yueliang; Peng, Xiaocong

    2017-06-01

    The development of high-power laser systems requires optical components that function at peak performance. Here, a high-precision, double beam, 1064 nm laser photometer setup was developed to measure the following different forms of optical loss from Nd-glass samples: total loss, volume loss, and the residual reflection and surface loss. The double beam design and a lock-in technique were utilized to decrease the impact of light-source instabilities and signal noise, respectively. The stability of the signal was further improved by decreasing the amount of optical absorption along the light path and by increasing the detection responsivity. Paired samples were symmetrically placed to eliminate beam displacement, and a laser scattering imaging technique was used to determine the influence of surface defects on the optical performance. Using the above techniques, multiple measurements of the transmittance and reflection values of the sample were taken, which showed our transmittance measurement to be highly precise, exhibiting a relative standard deviation of less than 0.06%. Different types of optical loss were distinguished and obtained from the transmittance and reflection measurements of samples with different thicknesses. A comparison of the optical performance from test points with and without surface defects allowed us to determine the influence of surface defects on the optical performance.

  13. Development of an ultra high-precision x-ray telescope with an adaptive optics system

    NASA Astrophysics Data System (ADS)

    Kitamoto, Shunji; Takano, Haruko; Saitoh, Harue; Yamamoto, Norimasa; Kohmura, Takayoshi; Suga, Kazuharu; Sekiguchi, Hiroyuki

    2003-06-01

    We are developing an ultra high precision Soft X-ray telescope. The design of the telescope is a normal incident one for 13.5 nm band using Mo/Si multilayers. Two ideas are introduced. One is the optical measurement system in order to monitor the prevision of the optics system. The other is the adaptive optics system with a deformable mirror. Using an x-ray optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror to compensate the system deformation as a closed loop system. We confirmed that the absolute precision of the wave front sensor was less than 3 nm rms. The preicison of the deformable mirror was roughly 5 nm rms. The shape of the primary mirror was an off-axis paraboloide with an effective diameter of 80mm. This primary mirror was coated by Mo/Si multilayers. The reflectivity of the primary mirror at 13.5 nm was rnaging from 30 to 50%. The x-ray optical separation filter was made from Zr with a thicknness of ~170nm. The transmission of the filter for low energy x-ray was measured and was roughly 50% at 13.5nm.

  14. Ion beam and plasma jet based methods in ultra-precision optics manufacturing

    NASA Astrophysics Data System (ADS)

    Arnold, Th.; Boehm, G.; Paetzelt, H.; Pietag, F.

    2015-01-01

    Ion beam and plasma jet based techniques can be used in alternative machining processes for generating and finishing of ultra-precision optical surfaces. Since atomistic mechanisms are responsible for surface material modification, etching, and deposition, very high accuracy on the atomic level can be achieved. Various advanced techniques like pulse-width modulated ion beam figuring, sub-aperture reactive ion beam etching, or ion beam assisted structuring, planarization and smoothing technologies have been investigated aiming at precision on sub-nanometer height scale and lateral scales ranging over the full spatial wavelength range from nanometers to meters. Additionally, different atmospheric reactive plasma jet processes and plasma jet assisted process chains for generating, correction and smoothing of complex shaped optical surfaces like aspheres with large departures to best fit sphere or free forms exhibiting strong gradients have been developed in the last decade. In the paper an overview to the most recent trends of non-conventional ultra-precision optics processing is given and latest results of optics manufacturing are shown. Specific examples are given to demonstrate that form generation (e.g. for laser beam shaping optics) and surface finishing and polishing using atmospheric plasma jet tools are promising applications exhibiting advantages with respect to process efficiency and flexibility. Furthermore, the capabilities of ion beam surface figure correction using a new approach to control the tool function are demonstrated.

  15. Non-contact precision profile measurement to rough-surface objects with optical frequency combs

    NASA Astrophysics Data System (ADS)

    Onoe, Taro; Takahashi, Satoru; Takamasu, Kiyoshi; Matsumoto, Hirokazu

    2016-12-01

    In this research, we developed a new method for the high precision and contactless profile measurement of rough-surfaced objects using optical frequency combs. The uncertainty of the frequency beats of an optical frequency comb is very small (relative uncertainty is 10-10 in our laboratory). In addition, the wavelengths corresponding to these frequency beats are long enough to measure rough-surfaced objects. We can conduct high-precision measurement because several GHz frequency beats can be used if the capability of the detector permits. Moreover, two optical frequency combs with Rb-stabilized repetition frequencies are used for the measurement instead of an RF frequency oscillator; thus, we can avoid the cyclic error caused by the RF frequency oscillator. We measured the profile of a wood cylinder with a rough surface (diameter is approximately 113.2 mm) and compared the result with that of coordinate measuring machine (CMM).

  16. Ion current as a precise measure of the loading rate of a magneto-optical trap

    SciTech Connect

    Jiang, W.; Bailey, K.; Lu, Z.-T.; Mueller, P.; O'Connor, T. P.; Purtschert, R.

    2014-01-15

    We have demonstrated that the ion current resulting from collisions between metastable krypton atoms in a magneto-optical trap can be used to precisely measure the trap loading rate. We measured both the ion current of the abundant isotope Kr-83 (isotopic abundance = 11%) and the single-atom counting rate of the rare isotope Kr-85 (isotopic abundance similar to 1 x 10(-11)), and found the two quantities to be proportional at a precision level of 0.9%. This work results in a significant improvement in using the magneto-optical trap as an analytical tool for noble-gas isotope ratio measurements, and will benefit both atomic physics studies and applications in the earth sciences. (C) 2014 Optical Society of America

  17. A method for cleaning optical precision surface of laser gyro cavity

    NASA Astrophysics Data System (ADS)

    Cui, Ying; Jiao, Ling Yan; Lin, Na Na; Zhang, Dong

    2016-10-01

    Laser gyro is the only one non-electromechanical high-precision inertial sensitive instruments in aircraft inertial guidance systems. Ultra high vacuum acquisition is a key segment during the manufacturing process of laser gyro. The surface cleanliness and integrity have decisive influence on the sealing performance of ultra-high vacuum. A cleaning technology for the optical surface of laser gyro cavity was found by experiment. Meanwhile, the analysis of the adsorption mechanism of contaminant on the laser gyro cavity surface and overview of common optical element cleaning technology were given. The result showed that the new cleaning technology improved the cleanliness of the cavity optical surface without any damage and provided a reliable solution for chronic leak of high precision laser gyro cavity.

  18. Precision beam pointing control with jitter attenuation by optical deflector exhibiting dynamic hysteresis in COIL

    NASA Astrophysics Data System (ADS)

    Ma, Yan-Hua; Zhang, Zeng-Bao; Zhang, Zhi-Guo; Liu, Qin; He, Xin; Shi, Wen-Bo; Mao, Jian-Qin; Jin, Yu-Qi

    2015-02-01

    Due to the existence of various disturbances during the lasing process of the chemical oxygen iodine laser (COIL), the optical beam pointing performance is severely degraded. In this paper, an adaptive control methodology is proposed for the precise pointing control of the optical beam with active beam jitter rejection using a giant magnetostrictive optical deflector (GMOD) which exhibits severe dynamic hysteresis nonlinearity. In particular, a least square support vector machine (LS-SVM) based fast compensator is employed to eliminate the dynamic hysteresis without the inverse model construction. Then an improved feedforward adaptive filter is developed to deal with jitter attenuation when the full-coherent reference signal is unavailable. To improve the stability and overall robustness of the controller, especially when a large initial bias exists, a PI controller is placed in parallel with the adaptive filter. Experimental results validate the precise pointing ability of the proposed control method.

  19. Ultra-long scan depth optical coherence tomography for imaging the anterior segment of human eye

    NASA Astrophysics Data System (ADS)

    Zhu, Dexi; Shen, Meixiao; Leng, Lin

    2012-12-01

    Spectral domain optical coherence tomography (SD-OCT) was developed in order to image the anterior segment of human eye. The optical path at reference arm was switched to compensate the sensitivity drop in OCT images. An scan depth of 12.28 mm and an axial resolution of 12.8 μm in air were achieved. The anterior segment from cornea to posterior surface of crystalline lens was clearly imaged and measured using this system. A custom designed Badal optometer was coupled into the sample arm to induce the accommodation, and the movement of crystalline lens was traced after the image registration. Our research demonstrates that SD-OCT with ultra-long scan depth can be used to image the human eye for accommodation research.

  20. Depth estimation of laser glass drilling based on optical differential measurements of acoustic response

    NASA Astrophysics Data System (ADS)

    Gorodesky, Niv; Ozana, Nisan; Berg, Yuval; Dolev, Omer; Danan, Yossef; Kotler, Zvi; Zalevsky, Zeev

    2016-09-01

    We present the first steps of a device suitable for characterization of complex 3D micro-structures. This method is based on an optical approach allowing extraction and separation of high frequency ultrasonic sound waves induced to the analyzed samples. Rapid, non-destructive characterization of 3D micro-structures are limited in terms of geometrical features and optical properties of the sample. We suggest a method which is based on temporal tracking of secondary speckle patterns generated when illuminating a sample with a laser probe while applying known periodic vibration using an ultrasound transmitter. In this paper we investigated lasers drilled through glass vias. The large aspect ratios of the vias possess a challenge for traditional microscopy techniques in analyzing depth and taper profiles of the vias. The correlation of the amplitude vibrations to the vias depths is experimentally demonstrated.

  1. Aerosol Optical Depth Distribution in Extratropical Cyclones over the Northern Hemisphere Oceans

    NASA Technical Reports Server (NTRS)

    Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

    2016-01-01

    Using Moderate Resolution Imaging Spectroradiometer and an extratropical cyclone database,the climatological distribution of aerosol optical depth (AOD) in extratropical cyclones is explored based solely on observations. Cyclone-centered composites of aerosol optical depth are constructed for the Northern Hemisphere mid-latitude ocean regions, and their seasonal variations are examined. These composites are found to be qualitatively stable when the impact of clouds and surface insolation or brightness is tested. The larger AODs occur in spring and summer and are preferentially found in the warm frontal and in the post-cold frontal regions in all seasons. The fine mode aerosols dominate the cold sector AODs, but the coarse mode aerosols display large AODs in the warm sector. These differences between the aerosol modes are related to the varying source regions of the aerosols and could potentially have different impacts on cloud and precipitation within the cyclones.

  2. Aerosol Optical Depth Distribution in Extratropical Cyclones over the Northern Hemisphere Oceans

    NASA Technical Reports Server (NTRS)

    Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

    2016-01-01

    Using Moderate Resolution Imaging Spectroradiometer and an extratropical cyclone database,the climatological distribution of aerosol optical depth (AOD) in extratropical cyclones is explored based solely on observations. Cyclone-centered composites of aerosol optical depth are constructed for the Northern Hemisphere mid-latitude ocean regions, and their seasonal variations are examined. These composites are found to be qualitatively stable when the impact of clouds and surface insolation or brightness is tested. The larger AODs occur in spring and summer and are preferentially found in the warm frontal and in the post-cold frontal regions in all seasons. The fine mode aerosols dominate the cold sector AODs, but the coarse mode aerosols display large AODs in the warm sector. These differences between the aerosol modes are related to the varying source regions of the aerosols and could potentially have different impacts on cloud and precipitation within the cyclones.

  3. Aerosol optical depth distribution in extratropical cyclones over the Northern Hemisphere oceans

    NASA Astrophysics Data System (ADS)

    Naud, Catherine M.; Posselt, Derek J.; Heever, Susan C.

    2016-10-01

    Using Moderate Resolution Imaging Spectroradiometer and an extratropical cyclone database, the climatological distribution of aerosol optical depth (AOD) in extratropical cyclones is explored based solely on observations. Cyclone-centered composites of aerosol optical depth are constructed for the Northern Hemisphere midlatitude ocean regions, and their seasonal variations are examined. These composites are found to be qualitatively stable when the impact of clouds and surface insolation or brightness is tested. The larger AODs occur in spring and summer and are preferentially found in the warm frontal and in the postcold frontal regions in all seasons. The fine mode aerosols dominate the cold sector AODs, but the coarse mode aerosols display large AODs in the warm sector. These differences between the aerosol modes are related to the varying source regions of the aerosols and could potentially have different impacts on cloud and precipitation within the cyclones.

  4. Calculation of optical properties of dental composites as a basis for determining color impression and penetration depth of laser light

    NASA Astrophysics Data System (ADS)

    Weniger, Kirsten K.; Muller, Gerhard J.

    2005-03-01

    In order to achieve esthetic dental restorations, there should be no visible difference between restorative material and treated teeth. This requires a match of the optical properties of both restorative material and natural teeth. These optical properties are determined by absorption and scattering of light emerging not only on the surface but also inside the material. Investigating different dental composites in several shades, a method has been developed to calculate the optical parameters absorption coefficient μa, scattering coefficient μs, anisotropy factor g and reduced scattering coefficient μs'. The method includes sample preparation and measurements of transmittance and reflectance in an integrating sphere spectrometer, followed by inverse Monte Carlo simulations. Determination of optical properties is more precise and comprehensive than with the previously used Kubelka Munk theory because scattering can be looked at separated into pure scattering with the scattering coefficient μs and its direction with the anisotropy factor g. Moreover the use of the inverse Monte Carlo simulation not only minimizes systematic errors and considers the scattering phase function, but also takes into account the measuring geometry. The compilation of a data pool of optical parameters now enables the application of further calculation models as a basis for optimization of the composition of new materials. For example, a prediction of the general color impression for multiple layers can be carried out as well as the calculation of the wavelength dependent penetration depths of light with regard to photo polymerization. Further applications are possible in the area of laser ablation.

  5. Development of a new process for manufacturing precision gobs out of new developed low Tg optical glasses for precise pressing of aspherical lenses; Technical Digest

    NASA Astrophysics Data System (ADS)

    Jaschek, Rainer; Klein, Christopher; Schenk, Christian; Schneider, Klaus; Freund, Jochen; Simone, Ritter

    2005-05-01

    Aspherical lenses or refractive elements out of optical glass can be produced either by grinding and polishing of glass or by precise molding of glass preforms. The first process is applied for lenses with larger geometries and smaller production quantities. On the other hand, precise molding is used for volume production of lenses within a diameter range between 1 mm and around 30 mm. The addressed products can be found in the consumer markets (digital imaging, digital projection and digital storage). Different preform types can be used for precise molding: polished spherical near shape preforms, polished balls, polished discs and precision gobs. The latter are made directly from the glass melt. This paper describes a newly developed process, which results in fire-polished gobs with very low surface roughness and excellent volume accuracy. Since precision gobs are mostly made for precise molding, they must meet specific process requirements apart form their optical values, such as allowing low molding temperatures and shorter process cycles times. Therefore, this paper also describes the latest results in the development of low Tg glasses, which are designed for the volume production of precision molded optical components. Beside the important parameters like nd, nd as well as Tg, other properties like chemical durability, devitrification resistance, thermal expansion and conductivity coefficients are important for optimizing the precise molding process. The characteristics of three new low Tg glasses in the FK-, PK- as well as SK-region are presented. These glasses are environmentally friendly, since they are free of lead and arsenic.

  6. Measuring Aerosol Optical Depth (AOD) and Aerosol Profiles Simultaneously with a Camera Lidar

    NASA Astrophysics Data System (ADS)

    Barnes, John; Pipes, Robert; Sharma, Nimmi C. P.

    2016-06-01

    CLidar or camera lidar is a simple, inexpensive technique to measure nighttime tropospheric aerosol profiles. Stars in the raw data images used in the CLidar analysis can also be used to calculate aerosol optical depth simultaneously. A single star can be used with the Langley method or multiple star pairs can be used to reduce the error. The estimated error from data taken under clear sky conditions at Mauna Loa Observatory is approximately +/- 0.01.

  7. Burn depth determination in human skin using polarization-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Pierce, Mark C.; Sheridan, Robert L.; Park, Boris H.; Cense, Barry; de Boer, Johannes F.

    2003-07-01

    Accurate evaluation of the depth of injury in burn victims is of considerable practical value to the surgeon, both for initial determination of resuscitation fluid requirements, and in deciding whether excision and closure of the wound is necessary. Currently, burn depth is most accurately evaluated by visual inspection, though decisions concerning treatment may not be possible for a number of days post-injury. As part of our ongoing efforts to provide an objective, quantitative method for burn depth determination, we present here the results of a study using polarization-sensitive optical coherence tomography (PS-OCT) to detect and measure thermally induced changes in collagen birefringence in skin excised from burn patients. We find that PS-OCT is capable of imaging and quantifying significantly reduced birefringence in burned human skin.

  8. Review of mesoscopic optical tomography for depth-resolved imaging of hemodynamic changes and neural activities.

    PubMed

    Tang, Qinggong; Lin, Jonathan; Tsytsarev, Vassiliy; Erzurumlu, Reha S; Liu, Yi; Chen, Yu

    2017-01-01

    Understanding the functional wiring of neural circuits and their patterns of activation following sensory stimulations is a fundamental task in the field of neuroscience. Furthermore, charting the activity patterns is undoubtedly important to elucidate how neural networks operate in the living brain. However, optical imaging must overcome the effects of light scattering in the tissue, which limit the light penetration depth and affect both the imaging quantitation and sensitivity. Laminar optical tomography (LOT) is a three-dimensional (3-D) in-vivo optical imaging technique that can be used for functional imaging. LOT can achieve both a resolution of 100 to [Formula: see text] and a penetration depth of 2 to 3 mm based either on absorption or fluorescence contrast, as well as large field-of-view and high acquisition speed. These advantages make LOT suitable for 3-D depth-resolved functional imaging of the neural functions in the brain and spinal cords. We review the basic principles and instrumentations of representative LOT systems, followed by recent applications of LOT on 3-D imaging of neural activities in the rat forepaw stimulation model and mouse whisker-barrel system.

  9. In-depth fiber optic two-photon polymerization and its applications in micromanipulation

    NASA Astrophysics Data System (ADS)

    Mishra, Yogeshwar N.; Ingle, Ninad D.; Pinto, Mervyn; Mohanty, Samarendra K.

    2011-02-01

    Two photon polymerization (TPP) has enabled three-dimensional microfabrication with sub-diffraction limited spatial resolution. However, depth at which TPP could be achieved, has been limited due to the high numerical aperture microscope objective, used to focus the ultrafast laser beam. Here, we report fiber-optic two photon polymerization (FTP) for in-depth fabrication of microstructures from a photopolymerizable resin. A cleaved single mode optical fiber coupled with tunable femtosecond laser could achieve TPP, forming extended waveguide on the fiber itself. The length of the FTP tip was found to depend on the laser power and exposure duration. Microfabricated fiber tip using FTP was employed to deliver continuous wave laser beam on to polystyrene microspheres in order to transport and manipulate selected particles by scattering force and 2D trapping. Such microstructures formed by TPP on tip of the fiber will also enable puncture and micro-surgery of cellular structures. With use of a cleaved fiber or axicon tip, FTP structures were fabricated on curved surfaces at large depth. The required Power for FTP and the polymerization rate was faster while using an axicon tip optical fiber. This enabled fabrication of complex octopus-like microstructures.

  10. Preliminary results of the aerosol optical depth retrieval in Johor, Malaysia

    NASA Astrophysics Data System (ADS)

    Lim, H. Q.; Kanniah, K. D.; Lau, A. M. S.

    2014-02-01

    Monitoring of atmospheric aerosols over the urban area is important as tremendous amounts of pollutants are released by industrial activities and heavy traffic flow. Air quality monitoring by satellite observation provides better spatial coverage, however, detailed aerosol properties retrieval remains a challenge. This is due to the limitation of aerosol retrieval algorithm on high reflectance (bright surface) areas. The aim of this study is to retrieve aerosol optical depth over urban areas of Iskandar Malaysia; the main southern development zone in Johor state, using Moderate Resolution Imaging Spectroradiometer (MODIS) 500 m resolution data. One of the important steps is the aerosol optical depth retrieval is to characterise different types of aerosols in the study area. This information will be used to construct a Look Up Table containing the simulated aerosol reflectance and corresponding aerosol optical depth. Thus, in this study we have characterised different aerosol types in the study area using Aerosol Robotic Network (AERONET) data. These data were processed using cluster analysis and the preliminary results show that the area is consisting of coastal urban (65%), polluted urban (27.5%), dust particles (6%) and heavy pollution (1.5%) aerosols.

  11. Laser-based ultrasound measurements of optical absorption depth in epoxy resins

    NASA Astrophysics Data System (ADS)

    Stratoudaki, Theodosia; Edwards, Christopher; Dixon, Stephen; Palmer, Stuart B.

    2002-09-01

    Pulsed lasers can generate ultrasound from stresses due to rapid thermal expansion. In this low power thermoelastic regime the material is not damaged. This paper concentrates on epoxy resins and aims to relate the observed amplitude of the longitudinal wave to the optical absorption depth of the epoxy. The ultrasound is generated using a high power pulsed laser and the absolute amplitude of the ultrasound is measured with a Michelson interferometer. In the thermoelastic regime, the laser beam is focused onto the sample, causing rapid expansion in times that are comparable to the rise time of the laser pulse. In metals, the laser radiation is absorbed in the thin electromagnetic skin depth but in non-metals the phenomenon is dominated by the optical absorption depth. The latter can vary from a few microns to several millimetres for materials such as epoxy resins. As a consequence, a bigger volume of the material is affected, the temperature rise is less and the amplitude of the longitudinal wave is greater. This condition is referred to as "a buried thermoelastic source". Two lasers were used in this study: a TEA CO2 and a XeCl excimer laser. The results are compared with optical transmission measurements.

  12. A geostatistical approach for producing daily Level-3 MODIS aerosol optical depth analyses

    NASA Astrophysics Data System (ADS)

    Ruiz-Arias, J. A.; Dudhia, J.; Lara-Fanego, V.; Pozo-Vázquez, D.

    2013-11-01

    The daily Level-3 MODIS (dL3M) aerosol optical depth product is a global daily spatial aggregation of the Level-2 MODIS aerosol optical depth (10-km spatial resolution) into a regular grid with a resolution of 1° × 1°. Aerosol optical depth is a seminal parameter for surface solar radiation assessment, in particular, for those applications involving direct irradiance. However, the dL3M AOD is prone to data gaps originated mostly by the unfeasibility of retrieving reliable estimates under cloudy conditions. In addition, its usability is also constrained by regional biases owing to some other reasons. In this work we propose a methodology for bias reduction and data-gaps removal of the dL3M AOD dataset. The result is a database of daily regularly-gridded AOD suitable for use in surface solar radiation applications and large-scale and long-term studies involving AOD without requiring a previous costly data assimilation process involving numerical weather prediction models. The method consists of an empirical approach to bias reduction, data-gaps removal by kriging interpolation and, finally, where reliable ground observations are available, an optimal interpolation procedure. The method was tested in the North American region, where it was able to reduce the initial mean error from 0.067 to 0.001, the root mean square error from 0.130 to 0.057, and increase the squared correlation coefficient from 23% to 58%, as compared against ground measurements.

  13. Measurements of stratospheric volcanic aerosol optical depth from NOAA TIROS Observational Vertical Sounder (TOVS) observations

    NASA Astrophysics Data System (ADS)

    Pierangelo, CléMence; ChéDin, Alain; Chazette, Patrick

    2004-02-01

    We show that the infrared optical depth of stratospheric volcanic aerosols produced by the eruption of Mount Pinatubo in June 1991 may be retrieved from the observations of the High-Resolution Infrared Radiation Sounder (HIRS-2) on board the polar meteorological satellites of the National Oceanic and Atmospheric Administration (NOAA). Evolution of the concentration in time and in space, in particular the migration of the aerosols from the tropics to the Northern and Southern Hemispheres, is found to be consistent with our knowledge of the consequences of this eruption. The method relies on the analysis of the differences between the satellite observations and simulations from an aerosol-free radiative transfer model using collocated radiosonde data as the prime input. Thus aerosol optical depths are retrieved directly without making assumptions about the aerosol size distribution or absorption coefficient. The aerosol optical depths reached a maximum in August 1991 in the tropical zone (0.055 at 8.3 μm, 0.03 at 4.0 μm, and 0.02 at 11.1 μm). The peak occurred in November 1991 in the southern midlatitudes and in March/April 1992 in the northern midlatitudes. A reanalysis of the almost 25 year archive of NOAA TIROS-N Operational Vertical Sounder (TOVS) observations holds considerable promise for improved knowledge of the atmosphere loading in volcanic aerosols.

  14. The optical depth sensor (ODS) for column dust opacity measurements and cloud detection on martian atmosphere

    NASA Astrophysics Data System (ADS)

    Toledo, D.; Rannou, P.; Pommereau, J.-P.; Foujols, T.

    2016-08-01

    A lightweight and sophisticated optical depth sensor (ODS) able to measure alternatively scattered flux at zenith and the sum of the direct flux and the scattered flux in blue and red has been developed to work in martian environment. The principal goals of ODS are to perform measurements of the daily mean dust opacity and to retrieve the altitude and optical depth of high altitude clouds at twilight, crucial parameters in the understanding of martian meteorology. The retrieval procedure of dust opacity is based on the use of radiative transfer simulations reproducing observed changes in the solar flux during the day as a function of 4 free parameters: dust opacity in blue and red, and effective radius and effective width of dust size distribution. The detection of clouds is undertaken by looking at the time variation of the color index (CI), defined as the ratio between red and blue ODS channels, at twilight. The retrieval of altitude and optical depth of clouds is carried out using a radiative transfer model in spherical geometry to simulate the CI time variation at twilight. Here the different retrieval procedures to analyze ODS signals, as well as the results obtained in different sensitivity analysis are presented and discussed.

  15. Team activity analysis and recognition based on Kinect depth map and optical imagery techniques

    NASA Astrophysics Data System (ADS)

    Elangovan, Vinayak; Bandaru, Vinod K.; Shirkhodaie, Amir

    2012-06-01

    Kinect cameras produce low-cost depth map video streams applicable for conventional surveillance systems. However, commonly applied image processing techniques are not directly applicable for depth map video processing. Kinect depth map images contain range measurement of objects at expense of having spatial features of objects suppressed. For example, typical objects' attributes such as textures, color tones, intensity, and other characteristic attributes cannot be fully realized by processing depth map imagery. In this paper, we demonstrate application of Kinect depth map and optical imagery for characterization of indoor and outdoor group activities. A Casual-Events State Inference (CESI) technique is proposed for spatiotemporal recognition and reasoning of group activities. CESI uses an ontological scheme for representation of casual distinctiveness of a priori known group activities. By tracking and serializing distinctive atomic group activities, CESI allows discovery of more complex group activities. A Modified Sequential Hidden Markov Model (MS-HMM) is implemented for trail analysis of atomic events representing correlated group activities. CESI reasons about five levels of group activities including: Merging, Planning, Cooperation, Coordination, and Dispersion. In this paper, we present results of capability of CESI approach for characterization of group activities taking place both in indoor and outdoor. Based on spatiotemporal pattern matching of atomic activities representing a known group activities, the CESI is able to discriminate suspicious group activity from normal activities. This paper also presents technical details of imagery techniques implemented for detection, tracking, and characterization of atomic events based on Kinect depth map and optical imagery data sets. Various experimental scenarios in indoors and outdoors (e.g. loading and unloading of objects, human-vehicle interactions etc.,) are carried to demonstrate effectiveness and

  16. Precise locating approach of the beacon based on gray gradient segmentation interpolation in satellite optical communications.

    PubMed

    Wang, Qiang; Liu, Yuefei; Chen, Yiqiang; Ma, Jing; Tan, Liying; Yu, Siyuan

    2017-03-01

    Accurate location computation for a beacon is an important factor of the reliability of satellite optical communications. However, location precision is generally limited by the resolution of CCD. How to improve the location precision of a beacon is an important and urgent issue. In this paper, we present two precise centroid computation methods for locating a beacon in satellite optical communications. First, in terms of its characteristics, the beacon is divided into several parts according to the gray gradients. Afterward, different numbers of interpolation points and different interpolation methods are applied in the interpolation area; we calculate the centroid position after interpolation and choose the best strategy according to the algorithm. The method is called a "gradient segmentation interpolation approach," or simply, a GSI (gradient segmentation interpolation) algorithm. To take full advantage of the pixels of the beacon's central portion, we also present an improved segmentation square weighting (SSW) algorithm, whose effectiveness is verified by the simulation experiment. Finally, an experiment is established to verify GSI and SSW algorithms. The results indicate that GSI and SSW algorithms can improve locating accuracy over that calculated by a traditional gray centroid method. These approaches help to greatly improve the location precision for a beacon in satellite optical communications.

  17. Development and Validation of High Precision Thermal, Mechanical, and Optical Models for the Space Interferometry Mission

    NASA Technical Reports Server (NTRS)

    Lindensmith, Chris A.; Briggs, H. Clark; Beregovski, Yuri; Feria, V. Alfonso; Goullioud, Renaud; Gursel, Yekta; Hahn, Inseob; Kinsella, Gary; Orzewalla, Matthew; Phillips, Charles

    2006-01-01

    SIM Planetquest (SIM) is a large optical interferometer for making microarcsecond measurements of the positions of stars, and to detect Earth-sized planets around nearby stars. To achieve this precision, SIM requires stability of optical components to tens of picometers per hour. The combination of SIM s large size (9 meter baseline) and the high stability requirement makes it difficult and costly to measure all aspects of system performance on the ground. To reduce risks, costs and to allow for a design with fewer intermediate testing stages, the SIM project is developing an integrated thermal, mechanical and optical modeling process that will allow predictions of the system performance to be made at the required high precision. This modeling process uses commercial, off-the-shelf tools and has been validated against experimental results at the precision of the SIM performance requirements. This paper presents the description of the model development, some of the models, and their validation in the Thermo-Opto-Mechanical (TOM3) testbed which includes full scale brassboard optical components and the metrology to test them at the SIM performance requirement levels.

  18. Coordinates calibration in precision detection of 3D optical deformation measurement system

    NASA Astrophysics Data System (ADS)

    Lu, Honggang; Hu, Chunsheng; Wang, Xingshu; Gao, Yang; Wu, Wei

    2012-11-01

    In order to validate the detection precision of a three Dimensions Optical Deformation Measure System (3D-OMS), a calibration method of auxiliary coordinate and the optical coordinate base on theodolites has been proposed. The installation method by using theodolites to calibrate the auxiliary coordinate and the optical coordinate has been proposed. Specifically, after the auxiliary mirrors installed, the installation accuracy is detected, then we analyzed the influence of Axis-Error of theodolite under the practical condition of our experiment. Furthermore, the influence of validation precision for the 3D-OMS caused by the misalignment of auxiliary coordinate and optical coordinate is analyzed. According to our theoretical analysis and experiments results, the validation precision of the 3D-OMS can achieve an accuracy of 1″ at the conditions of the coordinate alignment accuracy is no more than 10' and the measuring range of 3D-OMS within +/-3'. Therefore, the proposed method can meet our high accuracy requirement while not sensitive to the installation error of auxiliary mirrors. This method is also available for other similar work.

  19. Extended depth of focus adaptive optics spectral domain optical coherence tomography

    PubMed Central

    Sasaki, Kazuhiro; Kurokawa, Kazuhiro; Makita, Shuichi; Yasuno, Yoshiaki

    2012-01-01

    We present an adaptive optics spectral domain optical coherence tomography (AO-SDOCT) with a long focal range by active phase modulation of the pupil. A long focal range is achieved by introducing AO-controlled third-order spherical aberration (SA). The property of SA and its effects on focal range are investigated in detail using the Huygens-Fresnel principle, beam profile measurement and OCT imaging of a phantom. The results indicate that the focal range is extended by applying SA, and the direction of extension can be controlled by the sign of applied SA. Finally, we demonstrated in vivo human retinal imaging by altering the applied SA. PMID:23082278

  20. Spectral domain optical coherence tomography with extended depth-of-focus by aperture synthesis

    NASA Astrophysics Data System (ADS)

    Bo, En; Liu, Linbo

    2016-10-01

    We developed a spectral domain optical coherence tomography (SD-OCT) with an extended depth-of-focus (DOF) by synthetizing aperture. For a designated Gaussian-shape light source, the lateral resolution was determined by the numerical aperture (NA) of the objective lens and can be approximately maintained over the confocal parameter, which was defined as twice the Rayleigh range. However, the DOF was proportional to the square of the lateral resolution. Consequently, a trade-off existed between the DOF and lateral resolution, and researchers had to weigh and judge which was more important for their research reasonably. In this study, three distinct optical apertures were obtained by imbedding a circular phase spacer in the sample arm. Due to the optical path difference between three distinct apertures caused by the phase spacer, three images were aligned with equal spacing along z-axis vertically. By correcting the optical path difference (OPD) and defocus-induced wavefront curvature, three images with distinct depths were coherently summed together. This system digitally refocused the sample tissue and obtained a brand new image with higher lateral resolution over the confocal parameter when imaging the polystyrene calibration beads.

  1. Retrievals of cloud optical depth and effective radius from Thin-Cloud Rotating Shadowband Radiometer measurements

    SciTech Connect

    Yin B.; Vogelmann A.; Min Q.; Duan M.; Bartholomew M. J.; Turner D. D.

    2011-12-13

    A Thin-Cloud Rotating Shadowband Radiometer (TCRSR) was developed and deployed in a field test at the Atmospheric Radiation Measurement Climate Research Facility's Southern Great Plains site. The TCRSR measures the forward-scattering lobe of the direct solar beam (i.e., the solar aureole) through an optically thin cloud (optical depth < 8). We applied the retrieval algorithm of Min and Duan (2005) to the TCRSR measurements of the solar aureole to derive simultaneously the cloud optical depth (COD) and cloud drop effective radius (DER), subsequently inferring the cloud liquid-water path (LWP). After careful calibration and preprocessing, our results indicate that the TCRSR is able to retrieve simultaneously these three properties for optically thin water clouds. Colocated instruments, such as the MultiFilter Rotating Shadowband Radiometer (MFRSR), atmospheric emitted radiance interferometer (AERI), and Microwave Radiometer (MWR), are used to evaluate our retrieval results. The relative difference between retrieved CODs from the TCRSR and those from the MFRSR is less than 5%. The distribution of retrieved LWPs from the TCRSR is similar to those from the MWR and AERI. The differences between the TCRSR-based retrieved DERs and those from the AERI are apparent in some time periods, and the uncertainties of the DER retrievals are discussed in detail in this article.

  2. A Neural Network Approach to Infer Optical Depth of Thick Ice Clouds at Night

    NASA Technical Reports Server (NTRS)

    Minnis, P.; Hong, G.; Sun-Mack, S.; Chen, Yan; Smith, W. L., Jr.

    2016-01-01

    One of the roadblocks to continuously monitoring cloud properties is the tendency of clouds to become optically black at cloud optical depths (COD) of 6 or less. This constraint dramatically reduces the quantitative information content at night. A recent study found that because of their diffuse nature, ice clouds remain optically gray, to some extent, up to COD of 100 at certain wavelengths. Taking advantage of this weak dependency and the availability of COD retrievals from CloudSat, an artificial neural network algorithm was developed to estimate COD values up to 70 from common satellite imager infrared channels. The method was trained using matched 2007 CloudSat and Aqua MODIS data and is tested using similar data from 2008. The results show a significant improvement over the use of default values at night with high correlation. This paper summarizes the results and suggests paths for future improvement.

  3. Optical depth of molecular gas in starburst galaxies - Is M82 the prototype?

    NASA Technical Reports Server (NTRS)

    Verter, F.; Rickard, L. J.

    1989-01-01

    An attempt is made to survey the CO(2-1) emission toward the centers of 17 IR-luminous galaxies which have previously been detected in CO(1-0). These galaxies span a wide range of size and L(FIR)/L(B) ratio, many have multiple-wavelength studies establishing them as starbursts, and some bear a morphological resemblance to M 82. Nine galaxies are detected and useful upper limits are placed on the remaining eight. Using the CO(2-1)/CO(1-0) ratio of antenna temperature as a diagnostic of optical depth, it is found that all of the galaxies contain predominantly optically thick molecular gas. This implies that the phase of starburst during which the molecular gas is optically thin, currently witnessed in M 82, is either uncommon or short-lived.

  4. Dual-band Fourier domain optical coherence tomography with depth-related compensations

    PubMed Central

    Zhang, Miao; Ma, Lixin; Yu, Ping

    2013-01-01

    Dual-band Fourier domain optical coherence tomography (FD-OCT) provides depth-resolved spectroscopic imaging that enhances tissue contrast and reduces image speckle. However, previous dual-band FD-OCT systems could not correctly give the tissue spectroscopic contrast due to depth-related discrepancy in the imaging method and attenuation in biological tissue samples. We designed a new dual-band full-range FD-OCT imaging system and developed an algorithm to compensate depth-related fall-off and light attenuation. In our imaging system, the images from two wavelength bands were intrinsically overlapped and their intensities were balanced. The processing time of dual-band OCT image reconstruction and depth-related compensations were minimized by using multiple threads that execute in parallel. Using the newly developed system, we studied tissue phantoms and human cancer xenografts and muscle tissues dissected from severely compromised immune deficient mice. Improved spectroscopic contrast and sensitivity were achieved, benefiting from the depth-related compensations. PMID:24466485

  5. Improvement of Aerosol Optical Depth Retrieval over Hong Kong from a Geostationary Meteorological Satellite Using Critical Reflectance with Background Optical Depth Correction

    NASA Technical Reports Server (NTRS)

    Kim, Mijin; Kim, Jhoon; Wong, Man Sing; Yoon, Jongmin; Lee, Jaehwa; Wu, Dong L.; Chan, P.W.; Nichol, Janet E.; Chung, Chu-Yong; Ou, Mi-Lim

    2014-01-01

    Despite continuous efforts to retrieve aerosol optical depth (AOD) using a conventional 5-channelmeteorological imager in geostationary orbit, the accuracy in urban areas has been poorer than other areas primarily due to complex urban surface properties and mixed aerosol types from different emission sources. The two largest error sources in aerosol retrieval have been aerosol type selection and surface reflectance. In selecting the aerosol type from a single visible channel, the season-dependent aerosol optical properties were adopted from longterm measurements of Aerosol Robotic Network (AERONET) sun-photometers. With the aerosol optical properties obtained fromthe AERONET inversion data, look-up tableswere calculated by using a radiative transfer code: the Second Simulation of the Satellite Signal in the Solar Spectrum (6S). Surface reflectance was estimated using the clear sky composite method, awidely used technique for geostationary retrievals. Over East Asia, the AOD retrieved from the Meteorological Imager showed good agreement, although the values were affected by cloud contamination errors. However, the conventional retrieval of the AOD over Hong Kong was largely underestimated due to the lack of information on the aerosol type and surface properties. To detect spatial and temporal variation of aerosol type over the area, the critical reflectance method, a technique to retrieve single scattering albedo (SSA), was applied. Additionally, the background aerosol effect was corrected to improve the accuracy of the surface reflectance over Hong Kong. The AOD retrieved froma modified algorithmwas compared to the collocated data measured by AERONET in Hong Kong. The comparison showed that the new aerosol type selection using the critical reflectance and the corrected surface reflectance significantly improved the accuracy of AODs in Hong Kong areas,with a correlation coefficient increase from0.65 to 0.76 and a regression line change from tMI [basic algorithm] = 0

  6. Non-contact high precision measurement of surface form tolerances and central thickness for optical elements

    NASA Astrophysics Data System (ADS)

    Lou, Ying

    2010-10-01

    The traditional contact measuring methods could not satisfy the current optical elements measuring requirements. Noncontact high precision measuring theory, principle and instrument of the surface form tolerances and central thickness for optical elements were studied in the paper. In comparison with other types of interferometers, such as Twyman-Green and Mach-Zehnder, a Fizeau interferometer has the advantages of having fewer optical components, greater accuracy, and is easier to use. Some relations among the 3/A(B/C), POWER/PV and N/ΔN were studied. The PV with POWER removed can be the reference number of ΔN. The chromatic longitudinal aberration of a special optical probe can be used for non-contanct central thickness measurement.

  7. Fabrication of the Advanced X-ray Astrophysics Facility (AXAF) Optics: A Deterministic, Precision Engineering Approach to Optical Fabrication

    NASA Technical Reports Server (NTRS)

    Gordon, T. E.

    1995-01-01

    The mirror assembly of the AXAF observatory consists of four concentric, confocal, Wolter type 1 telescopes. Each telescope includes two conical grazing incidence mirrors, a paraboloid followed by a hyperboloid. Fabrication of these state-or-the-art optics is now complete, with predicted performance that surpasses the goals of the program. The fabrication of these optics, whose size and requirements exceed those of any previous x-ray mirrors, presented a challenging task requiring the use of precision engineering in many different forms. Virtually all of the equipment used for this effort required precision engineering. Accurate metrology required deterministic support of the mirrors in order to model the gravity distortions which will not be present on orbit. The primary axial instrument, known as the Precision Metrology Station (PMS), was a unique scanning Fizeau interferometer. After metrology was complete, the optics were placed in specially designed Glass Support Fixtures (GSF's) for installation on the Automated Cylindrical Grinder/Polishers (ACG/P's). The GSF's were custom molded for each mirror element to match the shape of the outer surface to minimize distortions of the inner surface. The final performance of the telescope is expected to far exceed the original goals and expectations of the program.

  8. Sub-nanometer interferometry and precision turning for large optical fabrication

    SciTech Connect

    Klingmann, J L; Sommargren, G E

    1999-04-01

    At Lawrence Livermore National Laboratory (LLNL), we have the unique combination of precision turning and metrology capabilities critical to the fabrication of large optical elements. We have developed a self-referenced interferometer to measure errors in aspheric optics to sub- nanometer accuracy over 200-millimeter apertures, a dynamic range of 5{approximately}10. We have utilized diamond turning to figure optics for X-ray to IR wavelengths and, with fast-tool-servo technology, can move optical segments from off-axis to on-axis. With part capacities to 2.3-meters diameter and the metrology described above, segments of very large, ultra-lightweight mirrors can potentially be figured to final requirements. precision of diamond-turning will carryover although the surface finish may be degraded. Finally, the most critical component of a fabrication process is the metrology that enables an accurate part. Well characterized machines are very repeatable and part accuracy must come from proper metrology. A self- referencing interferometer has been developed that can measure accurately to sub-nanometer values. As with traditional interferometers, measurements are fast and post- processed data provides useful feedback to the user. The simplicity of the device allows it to be used on large optics and systems.

  9. Multilevel micro-structuring of glassy carbon for precision glass molding of diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Plöger, Sven; Hermerschmidt, Andreas

    2015-03-01

    A consumer market for diffractive optical elements in glass can only be created if high efficient elements are available at affordable prices. In diffractive optics the efficiency and optical properties increases with the number of levels used, but in the same way the costs are multiplied by the number if fabrication steps. Replication of multilevel diffractive optical elements in glass would allow cost efficient fabrication but a suitable mold material is needed. Glassy carbon shows a high mechanical strength, thermal stability and non-sticking adhesion properties, which makes it an excellent candidate as mold material for precision compression molding of low and high glass-transition temperature materials. We introduce an 8 level micro structuring process for glassy carbon molds with standard photolithography and a Ti layer as hard mask for reactive ion etching. The molds were applied to thermal imprinting onto low and high transition temperature glass. Optical performance was tested for the molded samples with different designs for laser beamsplitters. The results show a good agreement to the design specification. Our result allow us to show limitations of our fabrication technique and we discussed the suitability of precision glass molding for cost efficient mass production with a high quality.

  10. THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE 'GREEN PEA' GALAXIES

    SciTech Connect

    Jaskot, A. E.; Oey, M. S.

    2013-04-01

    Although Lyman-continuum (LyC) radiation from star-forming galaxies likely drove the reionization of the universe, observations of star-forming galaxies at low redshift generally indicate low LyC escape fractions. However, the extreme [O III]/[O II] ratios of the z = 0.1-0.3 Green Pea galaxies may be due to high escape fractions of ionizing radiation. To analyze the LyC optical depths and ionizing sources of these rare, compact starbursts, we compare nebular photoionization and stellar population models with observed emission lines in the Peas' Sloan Digital Sky Survey (SDSS) spectra. We focus on the six most extreme Green Peas, the galaxies with the highest [O III]/[O II] ratios and the best candidates for escaping ionizing radiation. The Balmer line equivalent widths and He I {lambda}3819 emission in the extreme Peas support young ages of 3-5 Myr, and He II {lambda}4686 emission in five extreme Peas signals the presence of hard ionizing sources. Ionization by active galactic nuclei or high-mass X-ray binaries is inconsistent with the Peas' line ratios and ages. Although stacked spectra reveal no Wolf-Rayet (WR) features, we tentatively detect WR features in the SDSS spectra of three extreme Peas. Based on the Peas' ages and line ratios, we find that WR stars, chemically homogeneous O stars, or shocks could produce the observed He II emission. If hot stars are responsible, then the Peas' optical depths are ambiguous. However, accounting for emission from shocks lowers the inferred optical depth and suggests that the Peas may be optically thin. The Peas' ages likely optimize the escape of LyC radiation; they are old enough for supernovae and stellar winds to reshape the interstellar medium, but young enough to possess large numbers of UV-luminous O or WR stars.

  11. THE OPTICAL DEPTH OF H II REGIONS IN THE MAGELLANIC CLOUDS

    SciTech Connect

    Pellegrini, E. W.; Oey, M. S.; Jaskot, A. E.; Zastrow, J.; Winkler, P. F.; Points, S. D.; Smith, R. C.

    2012-08-10

    We exploit ionization-parameter mapping (IPM) as a powerful tool to measure the optical depth of star-forming H II regions. Our simulations using the photoionization code CLOUDY and our new, SURFBRIGHT surface-brightness simulator demonstrate that this technique can directly diagnose most density-bounded, optically thin nebulae using spatially resolved emission-line data. We apply this method to the Large and Small Magellanic Clouds (LMC and SMC), using the data from the Magellanic Clouds Emission Line Survey. We generate new H II region catalogs based on photoionization criteria set by the observed ionization structure in the [S II]/[O III] ratio and H{alpha} surface brightness. The luminosity functions from these catalogs generally agree with those from H{alpha}-only surveys. We then use IPM to crudely classify all the nebulae into optically thick versus optically thin categories, yielding fundamental new insights into Lyman-continuum (LyC) radiation transfer. We find that in both galaxies, the frequency of optically thin objects correlates with H{alpha} luminosity, and that the numbers of these objects dominate above log L/(erg s{sup -1}) {>=} 37.0. The frequencies of optically thin objects are 40% and 33% in the LMC and SMC, respectively. Similarly, the frequency of optically thick regions correlates with H I column density, with optically thin objects dominating at the lowest N(H I). The integrated escape luminosity of ionizing radiation is dominated by the largest regions and corresponds to luminosity-weighted, ionizing escape fractions from the H II region population of {>=}0.42 and {>=}0.40 in the LMC and SMC, respectively. These values correspond to global galactic escape fractions of 4% and 11%, respectively. This is sufficient to power the ionization rate of the observed diffuse ionized gas in both galaxies. Since our optical depth estimates tend to be underestimates, and also omit the contribution from field stars without nebulae, our results suggest

  12. Depth-resolved imaging of colon tumor using optical coherence tomography and fluorescence laminar optical tomography

    PubMed Central

    Tang, Qinggong; Wang, Jianting; Frank, Aaron; Lin, Jonathan; Li, Zhifang; Chen, Chao-wei; Jin, Lily; Wu, Tongtong; Greenwald, Bruce D.; Mashimo, Hiroshi; Chen, Yu

    2016-01-01

    Early detection of neoplastic changes remains a critical challenge in clinical cancer diagnosis and treatment. Many cancers arise from epithelial layers such as those of the gastrointestinal (GI) tract. Current standard endoscopic technology is difficult to detect the subsurface lesions. In this research, we investigated the feasibility of a novel multi-modal optical imaging approach including high-resolution optical coherence tomography (OCT) and high-sensitivity fluorescence laminar optical tomography (FLOT) for structural and molecular imaging. The C57BL/6J-ApcMin/J mice were imaged using OCT and FLOT, and the correlated histopathological diagnosis was obtained. Quantitative structural (scattering coefficient) and molecular (relative enzyme activity) parameters were obtained from OCT and FLOT images for multi-parametric analysis. This multi-modal imaging method has demonstrated the feasibility for more accurate diagnosis with 88.23% (82.35%) for sensitivity (specificity) compared to either modality alone. This study suggested that combining OCT and FLOT is promising for subsurface cancer detection, diagnosis, and characterization. PMID:28018738

  13. Quantitatively Measured Anatomic Location and Volume of Optic Disc Drusen: An Enhanced Depth Imaging Optical Coherence Tomography Study.

    PubMed

    Malmqvist, Lasse; Lindberg, Anne-Sofie Wessel; Dahl, Vedrana Andersen; Jørgensen, Thomas Martini; Hamann, Steffen

    2017-05-01

    Optic disc drusen (ODD) are found in up to 2.4% of the population and are known to cause visual field defects. The purpose of the current study was to investigate how quantitatively estimated volume and anatomic location of ODD influence optic nerve function. Anatomic location, volume of ODD, and peripapillary retinal nerve fiber layer and macular ganglion cell layer thickness were assessed in 37 ODD patients using enhanced depth imaging optical coherence tomography. Volume of ODD was calculated by manual segmentation of ODD in 97 B-scans per eye. Anatomic characteristics were compared with optic nerve function using automated perimetric mean deviation (MD) and multifocal visual evoked potentials. Increased age (P = 0.015); larger ODD volume (P = 0.002); and more superficial anatomic ODD location (P = 0.007) were found in patients with ODD visible by ophthalmoscopy compared to patients with buried ODD. In a multivariate analysis, a worsening of MD was significantly associated with larger ODD volume (P < 0.0001). No association was found between MD and weighted anatomic location, age, and visibility by ophthalmoscopy. Decreased ganglion cell layer thickness was significantly associated with worse MD (P = 0.025) and had a higher effect on MD when compared to retinal nerve fiber layer thickness. Large ODD volume is associated with optic nerve dysfunction. The worse visual field defects associated with visible ODD should only be ascribed to larger ODD volume and not to a more superficial anatomic ODD location.

  14. Depth-resolved imaging of colon tumor using optical coherence tomography and fluorescence laminar optical tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Tang, Qinggong; Frank, Aaron; Wang, Jianting; Chen, Chao-wei; Jin, Lily; Lin, Jon; Chan, Joanne M.; Chen, Yu

    2016-03-01

    Early detection of neoplastic changes remains a critical challenge in clinical cancer diagnosis and treatment. Many cancers arise from epithelial layers such as those of the gastrointestinal (GI) tract. Current standard endoscopic technology is unable to detect those subsurface lesions. Since cancer development is associated with both morphological and molecular alterations, imaging technologies that can quantitative image tissue's morphological and molecular biomarkers and assess the depth extent of a lesion in real time, without the need for tissue excision, would be a major advance in GI cancer diagnostics and therapy. In this research, we investigated the feasibility of multi-modal optical imaging including high-resolution optical coherence tomography (OCT) and depth-resolved high-sensitivity fluorescence laminar optical tomography (FLOT) for structural and molecular imaging. APC (adenomatous polyposis coli) mice model were imaged using OCT and FLOT and the correlated histopathological diagnosis was obtained. Quantitative structural (the scattering coefficient) and molecular imaging parameters (fluorescence intensity) from OCT and FLOT images were developed for multi-parametric analysis. This multi-modal imaging method has demonstrated the feasibility for more accurate diagnosis with 87.4% (87.3%) for sensitivity (specificity) which gives the most optimal diagnosis (the largest area under receiver operating characteristic (ROC) curve). This project results in a new non-invasive multi-modal imaging platform for improved GI cancer detection, which is expected to have a major impact on detection, diagnosis, and characterization of GI cancers, as well as a wide range of epithelial cancers.

  15. Precise measurement of volume of eccrine sweat gland in mental sweating by optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Sugawa, Yoshihiko; Fukuda, Akihiro; Ohmi, Masato

    2015-04-01

    We have demonstrated dynamic analysis of the physiological function of eccrine sweat glands underneath skin surface by optical coherence tomography (OCT). In this paper, we propose a method for extraction of the specific eccrine sweat gland by means of the connected component extraction process and the adaptive threshold method, where the en face OCT images are constructed by the swept-source OCT. In the experiment, we demonstrate precise measurement of the volume of the sweat gland in response to the external stimulus.

  16. On the assimilation of optical reflectances and snow depth observations into a detailed snowpack model

    NASA Astrophysics Data System (ADS)

    Charrois, L.; Cosme, E.; Dumont, M.; Lafaysse, M.; Morin, S.; Libois, Q.; Picard, G.

    2015-12-01

    This paper examines the ability of optical reflectance data assimilation to improve snow depth and snow water equivalent simulations from a detailed multilayer snowpack model. The direct use of reflectance data, instead of higher level snow products, rules out uncertainties due to commonly used retrieval algorithms. Data assimilation is performed with an ensemble-based method, the Sequential Importance Resampling Particle filter, to represent simulation uncertainties. Here, model uncertainties are essentially ascribed to meteorological forcings. An original method of stochastic perturbation is implemented to explicitly simulate the consequences of these uncertainties on the snowpack estimates. The assimilation of spectral reflectances from the MODerate Imaging Spectrometer (MODIS) sensor is examined, through twin experiments based on synthetic observations, over five seasons at the Col du Lautaret, located in the French Alps. Overall, the assimilation of MODIS-like data reduces root mean square errors (RMSE) on snow depth and snow water equivalent by a factor of 2. At this study site, the lack of MODIS data on cloudy days does not affect the assimilation performance significantly. The combined assimilation of MODIS-like reflectances and a few snow depth measurements throughout the 2010/11 season further reduces RMSEs by a factor of roughly 3.5. This work suggests that the assimilation of optical reflectances should become an essential component of spatialized snowpack simulation and forecast systems. The assimilation of real MODIS data will be investigated in future works.

  17. Noncontact depth-resolved micro-scale optical coherence elastography of the cornea

    PubMed Central

    Wang, Shang; Larin, Kirill V.

    2014-01-01

    High-resolution elastographic assessment of the cornea can greatly assist clinical diagnosis and treatment of various ocular diseases. Here, we report on the first noncontact depth-resolved micro-scale optical coherence elastography of the cornea achieved using shear wave imaging optical coherence tomography (SWI-OCT) combined with the spectral analysis of the corneal Lamb wave propagation. This imaging method relies on a focused air-puff device to load the cornea with highly-localized low-pressure short-duration air stream and applies phase-resolved OCT detection to capture the low-amplitude deformation with nano-scale sensitivity. The SWI-OCT system is used here to image the corneal Lamb wave propagation with the frame rate the same as the OCT A-line acquisition speed. Based on the spectral analysis of the corneal temporal deformation profiles, the phase velocity of the Lamb wave is obtained at different depths for the major frequency components, which shows the depthwise distribution of the corneal stiffness related to its structural features. Our pilot experiments on ex vivo rabbit eyes demonstrate the feasibility of this method in depth-resolved micro-scale elastography of the cornea. The assessment of the Lamb wave dispersion is also presented, suggesting the potential for the quantitative measurement of corneal viscoelasticity. PMID:25426312

  18. Examination of Optical Depth Effects on Fluorescence Imaging of Cardiac Propagation

    PubMed Central

    Bray, Mark-Anthony; Wikswo, John P.

    2003-01-01

    Optical mapping with voltage-sensitive dyes provides a high-resolution technique to observe cardiac electrodynamic behavior. Although most studies assume that the fluorescent signal is emitted from the surface layer of cells, the effects of signal attenuation with depth on signal interpretation are still unclear. This simulation study examines the effects of a depth-weighted signal on epicardial activation patterns and filament localization. We simulated filament behavior using a detailed cardiac model, and compared the signal obtained from the top (epicardial) layer of the spatial domain with the calculated weighted signal. General observations included a prolongation of the action upstroke duration, early upstroke initiation, and reduction in signal amplitude in the weighted signal. A shallow filament was found to produce a dual-humped action potential morphology consistent with previously reported observations. Simulated scroll wave breakup exhibited effects such as the false appearance of graded potentials, apparent supramaximal conduction velocities, and a spatially blurred signal with the local amplitude dependent upon the immediate subepicardial activity; the combination of these effects produced a corresponding change in the accuracy of filament localization. Our results indicate that the depth-dependent optical signal has significant consequences on the interpretation of epicardial activation dynamics. PMID:14645100

  19. Automated, Depth-resolved Estimation of the Attenuation Coefficient From Optical Coherence Tomography Data

    PubMed Central

    Smith, Gennifer T.; Dwork, Nicholas; O’Connor, Daniel; Sikora, Uzair; Lurie, Kristen L.; Pauly, John M.; Ellerbee, Audrey K.

    2015-01-01

    We present a method for automated, depth-resolved extraction of the attenuation coefficient from Optical Coherence Tomography (OCT) data. In contrast to previous automated, depth-resolved methods, the Depth-Resolved Confocal (DRC) technique derives an invertible mapping between the measured OCT intensity data and the attenuation coefficient while considering the confocal function and sensitivity fall-off, which are critical to ensure accurate measurements of the attenuation coefficient in practical settings (e.g., clinical endoscopy). We also show that further improvement of the estimated attenuation coefficient is possible by formulating image denoising as a convex optimization problem that we term Intensity Weighted Horizontal Total Variation (iwhTV). The performance and accuracy of DRC alone and DRC+iwhTV are validated with simulated data, optical phantoms, and ex-vivo porcine tissue. Our results suggest that implementation of DRC+iwhTV represents a novel way to improve OCT contrast for better tissue characterization through quantitative imaging. PMID:26126286

  20. Micro-precision control/structure interaction technology for large optical space systems

    NASA Technical Reports Server (NTRS)

    Sirlin, Samuel W.; Laskin, Robert A.

    1993-01-01

    The CSI program at JPL is chartered to develop the structures and control technology needed for sub-micron level stabilization of future optical space systems. The extreme dimensional stability required for such systems derives from the need to maintain the alignment and figure of critical optical elements to a small fraction (typically 1/20th to 1/50th) of the wavelength of detected radiation. The wavelength is about 0.5 micron for visible light and 0.1 micron for ultra-violet light. This lambda/50 requirement is common to a broad class of optical systems including filled aperture telescopes (with monolithic or segmented primary mirrors), sparse aperture telescopes, and optical interferometers. The challenge for CSI arises when such systems become large, with spatially distributed optical elements mounted on a lightweight, flexible structure. In order to better understand the requirements for micro-precision CSI technology, a representative future optical system was identified and developed as an analytical testbed for CSI concepts and approaches. An optical interferometer was selected as a stressing example of the relevant mission class. The system that emerged was termed the Focus Mission Interferometer (FMI). This paper will describe the multi-layer control architecture used to address the FMI's nanometer level stabilization requirements. In addition the paper will discuss on-going and planned experimental work aimed at demonstrating that multi-layer CSI can work in practice in the relevant performance regime.

  1. Restraint of range walk error in a Geiger-mode avalanche photodiode lidar to acquire high-precision depth and intensity information.

    PubMed

    Xu, Lu; Zhang, Yu; Zhang, Yong; Yang, Chenghua; Yang, Xu; Zhao, Yuan

    2016-03-01

    There exists a range walk error in a Geiger-mode avalanche photodiode (Gm-APD) lidar because of the fluctuation in the number of signal photoelectrons. To restrain this range walk error, we propose a new returning-wave signal processing technique based on the Poisson probability response model and the Gaussian functions fitting method. High-precision depth and intensity information of the target at the distance of 5 m is obtained by a Gm-APD lidar using a 6 ns wide pulsed laser. The experiment results show that the range and intensity precisions are 1.2 cm and 0.015 photoelectrons, respectively.

  2. A quantitative assessment of the depth sensitivity of an optical topography system using a solid dynamic tissue-phantom

    NASA Astrophysics Data System (ADS)

    Correia, Teresa; Banga, Anil; Everdell, N. L.; Gibson, Adam P.; Hebden, Jeremy C.

    2009-10-01

    A solid dynamic phantom with tissue-like optical properties is presented, which contains seven discrete targets impregnated with thermochromic pigment located at different depths from the surface. Changes in absorption are obtained in response to localized heating of the targets, simulating haemodynamic changes occurring in the brain and other tissues. The depth sensitivity of a continuous wave optical topography system was assessed successfully using the phantom. Images of the targets have been reconstructed using a spatially variant regularization, and the determined spatial localization in the depth direction is shown to be accurate within an uncertainty of about 3 mm down to a depth of about 30 mm.

  3. Remote sounding of the tropical cirrus cloud temperature and optical depth using 6.5 and 10.5-micron radiometers during STEP

    NASA Technical Reports Server (NTRS)

    Liou, K. N.; Ou, S. C.; Takano, Y.; Valero, F. P. J.; Ackerman, T. P.

    1990-01-01

    A dual-channel retrieval technique involving the water vapor band at 6.5 microns and the window region at 10.5 microns has been developed to infer the temperature and emissivity of tropical anvils. This technique has been applied to data obtained from the ER-2 narrow field-of-view radiometers during two flights in the field observation of the Stratosphere-Troposphere Exchange Project near Darwin, Australia, January-February 1987. The retrieved cloud temperatures are between 190 and 240 K, while the cloud emissivities derived from the retrieval algorithm range from about 0.2 to 1. Moreover, the visible optical depths have been obtained from the cloud emissivity through a theoretical parameterization with values of 0.5-10. A significant portion of tropical cirrus clouds are found to have optical depths greater than about 6. Because of the parameterization, the present technique is unable to precisely determine the optical depth values for optically thick cirrus clouds.

  4. Studies of aerosol optical depth with use of Microtops sun photometers and MODIS detectors

    NASA Astrophysics Data System (ADS)

    Makuch, Przemyslaw; Zawadzka, Olga; Markowicz, Krzystof M.; Zielinski, Tymon; Petelski, Tomasz; Strzalkowska, Agata; Rozwadowska, Anna; Gutowska, Dorota

    2013-04-01

    We would like to describe the results of a research campaign aimed at the studies of aerosol optical properties in the regions of the open Baltic Sea as well as coastal areas. During the campaign we carried out simultaneous measurements of aerosol optical depth at 4 stations with use of the hand-held Microtops II sunphotometers. The studies were complemented with the MODIS aerosol data. In order to obtain the full picture of the aerosol situation over the study area we added air mass back-trajectories at various altitudes and wind fields. Such complex information facilitated the proper conclusions regarding aerosol optical depth and Angstroem exponent for the four locations and discussion of the changes of aerosol properties with distance and meteorological factors. We show that Microtops II sunphotometers are reliable instruments for field campaigns. They are easy to operate and provide good quality results. Acknowledgements: The support for this study was provided by the project Satellite Monitoring of the Baltic Sea Environment - SatBałtyk founded by European Union through European Regional Development Fund contract No. POIG 01.01.02-22-011/09.

  5. Improved accuracy in periodontal pocket depth measurement using optical coherence tomography

    PubMed Central

    2017-01-01

    Purpose The purpose of this study was to examine whether periodontal pocket could be satisfactorily visualized by optical coherence tomography (OCT) and to suggest quantitative methods for measuring periodontal pocket depth. Methods We acquired OCT images of periodontal pockets in a porcine model and determined the actual axial resolution for measuring the exact periodontal pocket depth using a calibration method. Quantitative measurements of periodontal pockets were performed by real axial resolution and compared with the results from manual periodontal probing. Results The average periodontal pocket depth measured by OCT was 3.10±0.15 mm, 4.11±0.17 mm, 5.09±0.17 mm, and 6.05±0.21 mm for each periodontal pocket model, respectively. These values were similar to those obtained by manual periodontal probing. Conclusions OCT was able to visualize periodontal pockets and show attachment loss. By calculating the calibration factor to determine the accurate axial resolution, quantitative standards for measuring periodontal pocket depth can be established regardless of the position of periodontal pocket in the OCT image. PMID:28261520

  6. The stabilization of a multiplexed optical fiber interferometer system for on-line precision measurement

    NASA Astrophysics Data System (ADS)

    Fang, Xie; Chen, Zhi Min

    2008-12-01

    The stabilization of a multiplexed optical fiber interferometer system for on-line displacement precision measurement with a simple electric feedback loop is presented. Based on the characteristics of fiber Bragg gratings, the multiplexed optical fiber interferometer system includes two independent optical fiber Michelson interferometers of which the optical path is almost overlapped. One interferometer is used for the stabilization while the other interferometer is used for the measurement. A feed back signal from the feedback loop is driving a tube PZT on which one arm of the fiber interferometer is wounded. The phase-shift in the two arms of the interferometer resulting from the temperature fluctuations and other types of environmental disturbances is compensated. The bandwidth of the feedback loop is 5kHz. This makes the multiplexed fiber interferometer system stable enough for the on-line precision measurement. An active phase tracking technique is applied for signal processing to achieve high resolution. The measurement resolution of the system is less than 2nm.

  7. Constraints on primordial magnetic fields from the optical depth of the cosmic microwave background

    SciTech Connect

    Kunze, Kerstin E.

    2015-06-01

    Damping of magnetic fields via ambipolar diffusion and decay of magnetohydrodynamical (MHD) turbulence in the post decoupling era heats the intergalactic medium (IGM). Delayed recombination of hydrogen atoms in the IGM yields an optical depth to scattering of the cosmic microwave background (CMB). The optical depth generated at z >> 10 does not affect the ''reionization bump'' of the CMB polarization power spectrum at low multipoles, but affects the temperature and polarization power spectra at high multipoles. Writing the present-day energy density of fields smoothed over the damping scale at the decoupling epoch as ρ{sub B,0}=B{sub 0}{sup 2}/2, we constrain B{sub 0} as a function of the spectral index, n{sub B}. Using the Planck 2013 likelihood code that uses the Planck temperature and lensing data together with the WMAP 9-year polarization data, we find the 95% upper bounds of B{sub 0}<0.63, 0.39, and 0.18 nG for n{sub B}=−2.9, −2.5, and −1.5, respectively. For these spectral indices, the optical depth is dominated by dissipation of the decaying MHD turbulence that occurs shortly after the decoupling epoch. Our limits are stronger than the previous limits ignoring the effects of the fields on ionization history. Inverse Compton scattering of CMB photons off electrons in the heated IGM distorts the thermal spectrum of CMB. Our limits on B{sub 0} imply that the y-type distortion from dissipation of fields in the post decoupling era should be smaller than 10{sup −9}, 4×10{sup −9}, and 10{sup −9}, respectively.

  8. UVIS ring occultations show F ring feature location and optical depth correlated with Prometheus

    NASA Astrophysics Data System (ADS)

    Meinke, Bonnie K.; Esposito, L. W.; Albers, N.

    2010-05-01

    We find 24 statistically significant features in the F ring occultations using the High Speed Photometer (HSP) channel of the Cassini Ultraviolet Imaging Spectrograph (UVIS). These features are likely transient clumps of material embedded in the ring, each of which attenuates stellar signal during an occultation because the ring material is more densely packed at that location. In fact, two of these features are opaque, indicating they may be solid moonlets. Two trends are evident in the azimuthal location of these 24 F ring features with respect to that of Prometheus. First, the orbital locations of these features are mostly opposite Prometheus, as 11 of the 24 occupy the orbital region separated from Prometheus by 180° ± 20°. Second, average feature optical depth is maximum near the antipode of Prometheus in orbit. Our hypothesis is that these results show aggregation and disaggregation of clumps after Prometheus passes by. As Prometheus passes interior to the F ring, it encounters material once every synodic period, 68 days. Optical depth indicates density of ring material along the line of sight, so as material clumps together, we expect to see higher optical depths. Thus we infer that the encounter stimulates clumping of material that reaches a maximum 180° downstream. This may reinforce similar evidence that Ring-Moon interaction stimulates clumping in the F ring region from Cassini imaging (Beurle, et al., 2010) and at the B ring edge (Esposito, et al., 2010). Esposito, et al. (2010) suggest that the combined mass and velocity evolution of the ring system resembles a predator/prey model. This research was supported by the Cassini Project.

  9. In-depth quantification by using multispectral time-resolved diffuse optical tomography

    NASA Astrophysics Data System (ADS)

    Zouaoui, Judy; Hervé, Lionel; Di Sieno, Laura; Planat-Chrétien, Anne; Berger, Michel; Dalla Mora, Alberto; Pifferi, Antonio; Derouard, Jacques; Dinten, Jean-Marc

    2015-07-01

    Near-infrared diffuse optical tomography (DOT) is a medical imaging which gives the distribution of the optical properties of biological tissues. To obtain endogenous chromophore features in the depth of a scattering medium, a multiwavelength/time-resolved (MW/TR) DOT setup was used. Reconstructions of the three-dimensional maps of chromophore concentrations of probed media were obtained by using a data processing technique which manages Mellin-Laplace Transforms of their MW/TR optical signals and those of a known reference medium. The point was to put a constraint on the medium absorption coefficient by using a material basis composed of a given set of chromophores of known absorption spectra. Experimental measurements were conducted by injecting the light of a picosecond near- infrared laser in the medium of interest and by collecting, for several wavelengths and multiple positions, the backscattered light via two fibers (with a source-detector separation of 15 mm) connected to fast-gated single-photon avalanche diodes (SPAD) and coupled to a time-correlated single-photon counting (TCSPC) system. Validations of the method were performed in simulation in the same configuration as the experiments for different combination of chromophores. Evaluation of the technique in real conditions was investigated on liquid phantoms composed of an homogenous background and a 10 mm depth inclusion formed of combination of intralipid and inks scanned at 30 positions and at three wavelengths. Both numerical and preliminary phantom experiments confirm the potential of this method to determine chromophore concentrations in the depth of biological tissues.

  10. Effect of Binary Source Companions on the Microlensing Optical Depth Determination toward the Galactic Bulge Field

    NASA Astrophysics Data System (ADS)

    Han, Cheongho

    2005-11-01

    Currently, gravitational microlensing survey experiments toward the Galactic bulge field use two different methods of minimizing the blending effect for the accurate determination of the optical depth τ. One is measuring τ based on clump giant (CG) source stars, and the other is using ``difference image analysis'' (DIA) photometry to measure the unblended source flux variation. Despite the expectation that the two estimates should be the same assuming that blending is properly considered, the estimates based on CG stars systematically fall below the DIA results based on all events with source stars down to the detection limit. Prompted by the gap, we investigate the previously unconsidered effect of companion-associated events on τ determination. Although the image of a companion is blended with that of its primary star and thus not resolved, the event associated with the companion can be detected if the companion flux is highly magnified. Therefore, companions work effectively as source stars to microlensing, and thus the neglect of them in the source star count could result in a wrong τ estimation. By carrying out simulations based on the assumption that companions follow the same luminosity function as primary stars, we estimate that the contribution of the companion-associated events to the total event rate is ~5fbi% for current surveys and can reach up to ~6fbi% for future surveys monitoring fainter stars, where fbi is the binary frequency. Therefore, we conclude that the companion-associated events comprise a nonnegligible fraction of all events. However, their contribution to the optical depth is not large enough to explain the systematic difference between the optical depth estimates based on the two different methods.

  11. Retrieval of Aerosol Optical Depth Above Clouds from OMI Observations: Sensitivity Analysis, Case Studies

    NASA Technical Reports Server (NTRS)

    Torres, O.; Jethva, H.; Bhartia, P. K.

    2012-01-01

    A large fraction of the atmospheric aerosol load reaching the free troposphere is frequently located above low clouds. Most commonly observed aerosols above clouds are carbonaceous particles generally associated with biomass burning and boreal forest fires, and mineral aerosols originated in arid and semi-arid regions and transported across large distances, often above clouds. Because these aerosols absorb solar radiation, their role in the radiative transfer balance of the earth atmosphere system is especially important. The generally negative (cooling) top of the atmosphere direct effect of absorbing aerosols, may turn into warming when the light-absorbing particles are located above clouds. The actual effect depends on the aerosol load and the single scattering albedo, and on the geometric cloud fraction. In spite of its potential significance, the role of aerosols above clouds is not adequately accounted for in the assessment of aerosol radiative forcing effects due to the lack of measurements. In this paper we discuss the basis of a simple technique that uses near-UV observations to simultaneously derive the optical depth of both the aerosol layer and the underlying cloud for overcast conditions. The two-parameter retrieval method described here makes use of the UV aerosol index and reflectance measurements at 388 nm. A detailed sensitivity analysis indicates that the measured radiances depend mainly on the aerosol absorption exponent and aerosol-cloud separation. The technique was applied to above-cloud aerosol events over the Southern Atlantic Ocean yielding realistic results as indicated by indirect evaluation methods. An error analysis indicates that for typical overcast cloudy conditions and aerosol loads, the aerosol optical depth can be retrieved with an accuracy of approximately 54% whereas the cloud optical depth can be derived within 17% of the true value.

  12. Long-wavelength optical coherence tomography at 1.7 µm for enhanced imaging depth

    PubMed Central

    Sharma, Utkarsh; Chang, Ernest W.; Yun, Seok H.

    2009-01-01

    Multiple scattering in a sample presents a significant limitation to achieve meaningful structural information at deeper penetration depths in optical coherence tomography (OCT). Previous studies suggest that the spectral region around 1.7 µm may exhibit reduced scattering coefficients in biological tissues compared to the widely used wavelengths around 1.3 µm. To investigate this long-wavelength region, we developed a wavelength-swept laser at 1.7 µm wavelength and conducted OCT or optical frequency domain imaging (OFDI) for the first time in this spectral range. The constructed laser is capable of providing a wide tuning range from 1.59 to 1.75 µm over 160 nm. When the laser was operated with a reduced tuning range over 95 nm at a repetition rate of 10.9 kHz and an average output power of 12.3 mW, the OFDI imaging system exhibited a sensitivity of about 100 dB and axial and lateral resolution of 24 µm and 14 µm, respectively. We imaged several phantom and biological samples using 1.3 µm and 1.7 µm OFDI systems and found that the depth-dependent signal decay rate is substantially lower at 1.7 µm wavelength in most, if not all samples. Our results suggest that this imaging window may offer an advantage over shorter wavelengths by increasing the penetration depths as well as enhancing image contrast at deeper penetration depths where otherwise multiple scattered photons dominate over ballistic photons. PMID:19030057

  13. Scarring occurs at a critical depth of skin injury: precise measurement in a graduated dermal scratch in human volunteers.

    PubMed

    Dunkin, Christopher S J; Pleat, Jonathon M; Gillespie, Patrick H; Tyler, Michael P H; Roberts, Anthony H N; McGrouther, D Angus

    2007-05-01

    The association between scarring and the depth of dermal injury or burn is clinically recognized but not quantified. The authors tested the hypothesis that there is a critical depth beyond which a fibrous scar develops. A novel jig produced a wound that was deep dermal at one end and superficial dermal at the other. Pilot studies in cadaveric and ex vivo breast skin confirmed the depth of injury. Healthy volunteers had a standardized dermal wound made on the lateral aspect of the hip. Digital photography recorded the surface appearance of wound healing and scar development. High-frequency ultrasound demonstrated the depth of the healing wound and subsequent scar in vivo. One hundred thirteen human subjects participated in the clinical study. Mean length of follow up was 28.6 +/- 13.2 weeks. The deep dermal end of the wound healed with a visible scar and the superficial end had no visible residual mark after week 18. The initial length of injury was 51.3 +/- 0.6 mm, which reduced to a scar of 34.9 +/- 1.0 mm at 36 weeks (corresponding areas were 196.6 +/- 7.5 mm and 92.7 +/- 9.4 mm). High-frequency ultrasound analysis showed a gradual reduction in scar thickness at the deep end and no detectable scar at the shallow end. The transition point between scar and no scar marked the threshold depth for scarring. This was calculated as 0.56 +/- 0.03 mm, or 33.1 percent of normal hip skin thickness. The dermal scratch provides a well-tolerated, standardized, and reproducible wound model for investigating the healing response to dermal injury of different depths. There is a threshold depth of dermal injury at which scarring develops.

  14. The rapid and precise determination of the optical thickness of thin coatings in a vacuum.

    PubMed

    van Heel, A C; van Vonno, W

    1967-05-01

    The classical interference experiment with a double slit is adapted for measuring the optical thickness (n - 1)d of transparent and slightly absorbing thin films on transparent or reflecting substrates and for measuring the geometrical thickness d of metal films on reflecting substrates. Also, a method is described for measuring in vacuum the optical thickness of transparent or slightly absorbing thin films on transparent substrates. Results are given of measurements on magnesium fluoride, silicon monoxide, and zinc sulfide films. The influence of admitting air into the vacuum chamber has been investigated. With the available arrangements, a precision of lambda/1000 in the determination of the optical or geometrical thickness is easily obtainable for all film thicknesses. A thickness determination can he completed in about 1 min.

  15. Visible/Infrared Optical Depths of Cirrus as Seen by Satellite and Scanning Lidar

    NASA Technical Reports Server (NTRS)

    Wylie, Donald; Wolf, Walt; Piironen, Paivi; Eloranta, Edwin

    1996-01-01

    The High Spectral Resolution Lidar (HSRL) and the Volume Imaging Lidar (VIL) were combined to produce a quantitative image of the visible optical depth of cirrus clouds. The HSRL was used to calibrate the VIL signal into backscatter cross sections of particulates. The backscatter cross sections were related to extinction by a constant backscatter phase function determined from the HSRL data. This produced a three dimensional image of visual extinction in the cirrus clouds over a one hour period. Two lidar images were constructed from one hour VIL cross section records.

  16. Wave like signatures in aerosol optical depth and associated radiative impacts over the central Himalayan region

    SciTech Connect

    Shukla, K. K.; Phanikumar, D. V.; Kumar, K. Niranjan; Reddy, Kishore; Kotamarthi, V. R.; Newsom, Rob K.; Ouarda, Taha B.M.J.

    2015-10-01

    Doppler Lidar and Multi-Filter Rotating Shadowband Radiometer (MFRSR) observations are utilized to show wave like signatures in aerosol optical depth (AOD) during daytime boundary layer evolution over the Himalayan region. Fourier analysis depicted 60–80 min periods dominant during afternoon hours, implying that observed modulations could be plausible reason for the AOD forenoon–afternoon asymmetry which was previously reported. Inclusion of wave amplitude in diurnal variation of aerosol radiative forcing estimates showed ~40% additional warming in the atmosphere relative to mean AOD. The present observations emphasize the importance of wave induced variations in AOD and radiation budget over the site.

  17. Analysis of the depth of field of integral imaging displays based on wave optics.

    PubMed

    Luo, Cheng-Gao; Xiao, Xiao; Martínez-Corral, Manuel; Chen, Chih-Wei; Javidi, Bahram; Wang, Qiong-Hua

    2013-12-16

    In this paper, we analyze the depth of field (DOF) of integral imaging displays based on wave optics. With considering the diffraction effect, we analyze the intensity distribution of light with multiple micro-lenses and derive a DOF calculation formula for integral imaging display system. We study the variations of DOF values with different system parameters. Experimental results are provided to verify the accuracy of the theoretical analysis. The analyses and experimental results presented in this paper could be beneficial for better understanding and designing of integral imaging displays.

  18. Aerosol optical depth measurements by means of a Sun photometer network in Switzerland

    NASA Astrophysics Data System (ADS)

    Ingold, T.; MäTzler, C.; KäMpfer, N.; Heimo, A.

    2001-11-01

    Within the Swiss Atmospheric Radiation Monitoring program (CHARM) the Swiss Meteorological Institute - MeteoSwiss operates a network of presently six Sun photometer stations. Aerosol optical depths (AOD) at 368, 500, and 778 nm were determined from measurements of the relative direct solar irradiance, primarily to provide climatological information relevant in particular to climate change studies. The six instruments are located at various sites representative of high and low altitudes at the north and south part of the Alps in areas free from urban pollution in Switzerland. AOD time series of recordings back to 1991 are discussed, when data were first collected at Davos. An important aerosol layer is often present over stations at lower sites, showing seasonal variability and regional differences for the observed tropospheric aerosols. A classification scheme for synoptic weather types was applied to separate the AOD data into groups corresponding to different atmospheric transport conditions. On average, lower AODs are measured within advective weather situations than within convective ones. However, at the high Alpine sites such a classification is incomplete for AOD characterization due to orographically induced vertical motion. Monthly averaged values of AOD at 500 nm ranged from 0.05 during winter up to 0.3 in summer. The scale height of the aerosol optical depth is found to be 1-2 km depending on season. The high mountain sites are more suitable to the study stratospheric aerosols, for example, the change of the aerosol content and of its size distribution due to Mount Pinatubo eruption was clearly identified at Davos. In 1996 the aerosol optical depth returned to pre-Pinatubo values. Minimum AODs of ≈0.004-0.007 measured at 500 nm in 1997 are in good agreement with widely reported aerosol optical depth measurements of the stratospheric background aerosols. Besides the Pinatubo-affected period aerosol characterization by means of the Angström power law

  19. Improved Aerosol Optical Depth and Particle Size Index from Satellite Detected Radiance

    DTIC Science & Technology

    1991-12-01

    the central Pacific. Another environmental factor discussed by Benedict (1989) was the eruption of the Kilauea volcano in Hawaii (17°N, 157°W...another near 1O0N. A distinction can be made between an influence from Kilauea volcano at 20°N and DMS production leading to non-sea-salt sulfate...natural dust or anthropogenic pollutants. There is another peak near 8°N. Since Figure 8 revealed little optical depth from the eruption of Kilauea , this

  20. Diffuse Optical Imaging and Spectroscopy of the Human Breast for Quantitative Oximetry with Depth Resolution

    NASA Astrophysics Data System (ADS)

    Yu, Yang

    Near-infrared spectral imaging for breast cancer diagnostics and monitoring has been a hot research topic for the past decade. Here we present instrumentation for diffuse optical imaging of breast tissue with tandem scan of a single source-detector pair with broadband light in transmission geometry for tissue oximetry. The efforts to develop the continuous-wave (CW) domain instrument have been described, and a frequency-domain (FD) system is also used to measure the bulk tissue optical properties and the breast thickness distribution. We also describe the efforts to improve the data processing codes in the 2D spatial domain for better noise suppression, contrast enhancement, and spectral analysis. We developed a paired-wavelength approach, which is based on finding pairs of wavelength that feature the same optical contrast, to quantify the tissue oxygenation for the absorption structures detected in the 2D structural image. A total of eighteen subjects, two of whom were bearing breast cancer on their right breasts, were measured with this hybrid CW/FD instrument and processed with the improved algorithms. We obtained an average tissue oxygenation value of 87% +/- 6% from the healthy breasts, significantly higher than that measured in the diseased breasts (69% +/- 14%) (p < 0.01). For the two diseased breasts, the tumor areas bear hypoxia signatures versus the remainder of the breast, with oxygenation values of 49 +/- 11% (diseased region) vs. 61 +/- 16% (healthy regions) for the breast with invasive ductal carcinoma, and 58 +/- 8% (diseased region) vs 77 +/- 11% (healthy regions) for ductal carcinoma in situ. Our subjects came from various ethnical/racial backgrounds, and two-thirds of our subjects were less than thirty years old, indicating a potential to apply the optical mammography to a broad population. The second part of this thesis covers the topic of depth discrimination, which is lacking with our single source-detector scan system. Based on an off

  1. Strategies to Improve the Accuracy of Mars-GRAM Sensitivity Studies at Large Optical Depths

    NASA Technical Reports Server (NTRS)

    Justh, Hilary L.; Justus, Carl G.; Badger, Andrew M.

    2010-01-01

    The poster provides an overview of techniques to improve the Mars Global Reference Atmospheric Model (Mars-GRAM) sensitivity. It has been discovered during the Mars Science Laboratory (MSL) site selection process that the Mars Global Reference Atmospheric Model (Mars-GRAM) when used for sensitivity studies for TES MapYear = 0 and large optical depth values such as tau = 3 is less than realistic. A preliminary fix has been made to Mars-GRAM by adding a density factor value that was determined for tau = 0.3, 1 and 3.

  2. An ultra-high optical depth cold atomic ensemble for quantum memories

    NASA Astrophysics Data System (ADS)

    Sparkes, B. M.; Bernu, J.; Hosseini, M.; Geng, J.; Glorieux, Q.; Altin, P. A.; Lam, P. K.; Robins, N. P.; Buchler, B. C.

    2013-12-01

    Quantum memories for light lie at the heart of long-distance provably-secure communication. Demand for a functioning quantum memory, with high efficiency and coherence times approaching a millisecond, is therefore at a premium. Here we report on work towards this goal, with the development of a 87Rb magneto-optical trap with a peak optical depth of 1000 for the D2 F = 2 → F' = 3 transition using spatial and temporal dark spots. With this purpose-built cold atomic ensemble we implemented the gradient echo memory (GEM) scheme on the D1 line. Our data shows a memory efficiency of 80 ± 2% and coherence times up to 195 μs.

  3. Gradient echo memory in an ultra-high optical depth cold atomic ensemble

    NASA Astrophysics Data System (ADS)

    Sparkes, B. M.; Bernu, J.; Hosseini, M.; Geng, J.; Glorieux, Q.; Altin, P. A.; Lam, P. K.; Robins, N. P.; Buchler, B. C.

    2013-08-01

    Quantum memories are an integral component of quantum repeaters—devices that will allow the extension of quantum key distribution to communication ranges beyond that permissible by passive transmission. A quantum memory for this application needs to be highly efficient and have coherence times approaching a millisecond. Here we report on work towards this goal, with the development of a 87Rb magneto-optical trap with a peak optical depth of 1000 for the D2 F = 2 → F‧ = 3 transition using spatial and temporal dark spots. With this purpose-built cold atomic ensemble we implemented the gradient echo memory (GEM) scheme on the D1 line. Our data shows a memory efficiency of 80 ± 2% and coherence times up to 195 μs, which is a factor of four greater than previous GEM experiments implemented in warm vapour cells.

  4. An Analytic Inversion of Emission Lines of Arbitrary Optical Depth for the Structure of Supernova Ejecta

    NASA Astrophysics Data System (ADS)

    Ignace, R.; Hendry, M. A.

    2000-05-01

    We have derived a method for inverting emission line profiles formed in supernova ejecta. The derivation assumes spherical symmetry and homologous expansion (i.e., v(r) r). The inversion is analytic and even takes account of occultation by a pseudo-photosphere. Previous inversion methods have been developed which are restricted to optically thin lines, but the particular case of homologous expansion permits an analytic inversion for lines of arbitrary optical depth. In fact, we show that the quantity that is generically retrieved is the run of line intensity Iλ with radius in the ejecta shell. This result could be applied to resonance lines, recombination lines, or lines dominated by collisional de-excitation.

  5. A Lightweight, Precision-Deployable, Optical Bench for High Energy Astrophysics Missions

    NASA Astrophysics Data System (ADS)

    Danner, Rolf; Dailey, D.; Lillie, C.

    2011-09-01

    The small angle of total reflection for X-rays, forcing grazing incidence optics with large collecting areas to long focal lengths, has been a fundamental barrier to the advancement of high-energy astrophysics. Design teams around the world have long recognized that a significant increase in effective area beyond Chandra and XMM-Newton requires either a deployable optical bench or separate X-ray optics and instrument module on formation flying spacecraft. Here, we show that we have in hand the components for a lightweight, precision-deployable optical bench that, through its inherent design features, is the affordable path to the next generation of imaging high-energy astrophysics missions. We present our plans for a full-scale engineering model of a deployable optical bench for Explorer-class missions. We intend to use this test article to raise the technology readiness level (TRL) of the tensegrity truss for a lightweight, precision-deployable optical bench for high-energy astrophysics missions from TRL 3 to TRL 5 through a set of four well-defined technology milestones. The milestones cover the architecture's ability to deploy and control the focal point, characterize the deployed dynamics, determine long-term stability, and verify the stowed load capability. Our plan is based on detailed design and analysis work and the construction of a first prototype by our team. Building on our prior analysis and the high TRL of the architecture components we are ready to move on to the next step. The key elements to do this affordably are two existing, fully characterized, flight-quality, deployable booms. After integrating them into the test article, we will demonstrate that our architecture meets the deployment accuracy, adjustability, and stability requirements. The same test article can be used to further raise the TRL in the future.

  6. Optical gating and streaking of free electrons with sub-optical cycle precision

    PubMed Central

    Kozák, M.; McNeur, J.; Leedle, K. J.; Deng, H.; Schönenberger, N.; Ruehl, A.; Hartl, I.; Harris, J. S.; Byer, R. L.; Hommelhoff, P.

    2017-01-01

    The temporal resolution of ultrafast electron diffraction and microscopy experiments is currently limited by the available experimental techniques for the generation and characterization of electron bunches with single femtosecond or attosecond durations. Here, we present proof of principle experiments of an optical gating concept for free electrons via direct time-domain visualization of the sub-optical cycle energy and transverse momentum structure imprinted on the electron beam. We demonstrate a temporal resolution of 1.2±0.3 fs. The scheme is based on the synchronous interaction between electrons and the near-field mode of a dielectric nano-grating excited by a femtosecond laser pulse with an optical period duration of 6.5 fs. The sub-optical cycle resolution demonstrated here is promising for use in laser-driven streak cameras for attosecond temporal characterization of bunched particle beams as well as time-resolved experiments with free-electron beams. PMID:28120930

  7. [Digital imaging fiber optic transillumination (DIFOTI) method for determining the depth of cavity].

    PubMed

    Yu, J L; Tang, R T; Feng, L; Dong, Y M

    2017-02-18

    To analyze the accuracy of the digital imaging fiber optic transillumination (DIFOTI) on diagnosis of caries lesions depth using DIAGNOcam system. This experiment adopted self-matching design. Seventy-four extracted teeth (molar: sixty-six, premolar: eight) with one caries lesions in proximity which were not damaged in surface marginal ridge were selected. Dental calculus and dental stains were removed from the extracted teeth for standby application. A sign was marked in the middle of the occlusal surface edge at the side of decay. Then the teeth were fixed in the standard model of dentition and cavities were adjacent with the sound tooth surface. Sticky wax was applied to seal the level of 2 mm beyond cemento-enamel junction (CEJ) in the direction of occlusion and interproximal space to imitate gingival margin and gingival papilla. The standard models of dentition was seated in imitation head mold. The lesions depth degree was looked into and checked with DIAGNOcam system. Besides, the pictures on the occlusal surfaces were recorded and saved. The sign above could be seen on the picture. The measuring tool in DIAGNOcam system was used to measure the depth of the caries from the sign (as starting point) to the deepest point of caries in the pictures and its length was recorded for a. The line a was lengthened to the contralateral edge of occlusal surface in the photo and the length was recorded for b. A line from the marked point on the occlusal surface edge of the extracted teeth was draw parallel to the line b on the corresponding photo and its length was recorded for c. The depth of the cavities on the projected images was recorded for d, and calculated d/a=c/b (digital optical fiber measured decay depth/caries damage depth of the image=actual tooth width/tooth width of the image), and d=c/b×a inferred. At last, the teeth were taken out from the standard model dentition. The decay of the tooth was removed completely. The actual depth of the cavity was recorded

  8. Broadband optical mammography instrument for depth-resolved imaging and local dynamic measurements

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, Nishanth; Kainerstorfer, Jana M.; Sassaroli, Angelo; Anderson, Pamela G.; Fantini, Sergio

    2016-02-01

    We present a continuous-wave instrument for non-invasive diffuse optical imaging of the breast in a parallel-plate transmission geometry. The instrument measures continuous spectra in the wavelength range 650-1000 nm, with an intensity noise level <1.5% and a spatial sampling rate of 5 points/cm in the x- and y-directions. We collect the optical transmission at four locations, one collinear and three offset with respect to the illumination optical fiber, to recover the depth of optical inhomogeneities in the tissue. We imaged a tissue-like, breast shaped, silicone phantom (6 cm thick) with two embedded absorbing structures: a black circle (1.7 cm in diameter) and a black stripe (3 mm wide), designed to mimic a tumor and a blood vessel, respectively. The use of a spatially multiplexed detection scheme allows for the generation of on-axis and off-axis projection images simultaneously, as opposed to requiring multiple scans, thus decreasing scan-time and motion artifacts. This technique localizes detected inhomogeneities in 3D and accurately assigns their depth to within 1 mm in the ideal conditions of otherwise homogeneous tissue-like phantoms. We also measured induced hemodynamic changes in the breast of a healthy human subject at a selected location (no scanning). We applied a cyclic, arterial blood pressure perturbation by alternating inflation (to a pressure of 200 mmHg) and deflation of a pneumatic cuff around the subject's thigh at a frequency of 0.05 Hz, and measured oscillations with amplitudes up to 1 μM and 0.2 μM in the tissue concentrations of oxyhemoglobin and deoxyhemoglobin, respectively. These hemodynamic oscillations provide information about the vascular structure and functional integrity in tissue, and may be used to assess healthy or abnormal perfusion in a clinical setting.

  9. Effect of Aerosol Size and Hygroscopicity on Aerosol Optical Depth in the Southeastern United States

    NASA Astrophysics Data System (ADS)

    Brock, Charles; Wagner, Nick; Gordon, Timothy

    2016-04-01

    Aerosol optical depth (AOD) is affected by the size, optical characteristics, and hygroscopicity of particles, confounding attempts to link remote sensing observations of AOD to measured or modeled aerosol mass concentrations. In situ airborne observations of aerosol optical, chemical, microphysical and hygroscopic properties were made in the southeastern United States in the daytime in summer 2013. We use these observations to constrain a simple model that is used to test the sensitivity of AOD to the various measured parameters. As expected, the AOD was found to be most sensitive to aerosol mass concentration and to aerosol water content, which is controlled by aerosol hygroscopicity and the ambient relative humidity. However, AOD was also fairly sensitive to the mean particle diameter and the width of the size distribution. These parameters are often prescribed in global models that use simplified modal parameterizations to describe the aerosol, suggesting that the values chosen could substantially bias the calculated relationship between aerosol mass and optical extinction, AOD, and radiative forcing.

  10. Simple fiber-optic confocal microscopy with nanoscale depth resolution beyond the diffraction barrier.

    PubMed

    Ilev, Ilko; Waynant, Ronald; Gannot, Israel; Gandjbakhche, Amir

    2007-09-01

    A novel fiber-optic confocal approach for ultrahigh depth-resolution (optic confocal microscope approach that is compatible with a differential confocal microscope technique. To improve the dynamic range of the resolving laser power and to achieve a high resolution in the nanometric range, we have designed a simple apertureless reflection confocal microscope with a highly sensitive single-mode-fiber confocal output. The fiber-optic design is an effective alternative to conventional pinhole-based confocal systems and offers a number of advantages in terms of spatial resolution, flexibility, miniaturization, and scanning potential. Furthermore, the design is compatible with the differential confocal pinhole microscope based on the use of the sharp diffraction-free slope of the axial confocal response curve rather than the area around the maximum of that curve. Combining the advantages of ultrahigh-resolution fiber-optic confocal microscopy, we can work beyond the diffraction barrier in the subwavelength (below 200 nm) nanometric range exploiting confocal nanobioimaging of single cell and intracellular analytes.

  11. Injection molding of high precision optics for LED applications made of liquid silicone rubber

    SciTech Connect

    Hopmann, Christian; Röbig, Malte

    2016-03-09

    Light Emitting Diodes (LED) conquer the growing global market of lighting technologies. Due to their advantages, they are increasingly used in consumer products, in lighting applications in the home and in the mobility sector as well as in industrial applications. Particularly, with regard to the increasing use of high-power LED (HP-LED) the materials in the surrounding area of the light emitting semiconductor chip are of utmost importance. While the materials behind the semiconductor chip are optimized for maximum heat dissipation, the materials currently used for the encapsulation of the semiconductor chip (primary optics) and the secondary optics encounter their limits due to the high temperatures. In addition certain amounts of blue UV radiation degrade the currently used materials such as epoxy resins or polyurethanes for primary optics. In the context of an ongoing joint research project with various partners from the industry, an innovative manufacturing method for high precision optics for LED applications made of liquid silicone rubber (LSR) is analyzed at the Institut of Plastics Processing (IKV), Aachen. The aim of this project is to utilize the material-specific advantages of high transparent LSR, especially the excellent high temperature resistance and the great freedom in design. Therefore, a high integrated injection molding process is developed. For the production of combined LED primary and secondary optics a LED board is placed in an injection mold and overmolded with LSR. Due to the integrated process and the reduction of subcomponents like the secondary optics the economics of the production process can be improved significantly. Furthermore combined LED optics offer an improved effectiveness, because there are no losses of the light power at the transition of the primary and secondary optics.

  12. Ship-based Aerosol Optical Depth Measurements in the Atlantic Ocean, Comparison with Satellite Retrievals and GOCART Model

    NASA Astrophysics Data System (ADS)

    Smirnov, A.; Holben, B. N.; Sakerin, S.; Kabanov, D.; Slutsker, I.; Remer, L. A.; Kahn, R.; Ignatov, A.; Chin, M.; Diehl, T. L.; Mishchenko, M.; Liu, L.; Kucsera, T. L.; Giles, D.; Eck, T. F.; Torres, O.; Kopelevich, O.

    2005-12-01

    Aerosol optical depth measurements were made in October -December 2004 aboard of R/V Akademik Sergey Vavilov. The cruise area included the Atlantic transect from North Sea to Cape Town and then a crossing in the South Atlantic to Ushuaia, Argentina. The hand-held Microtops II sunphotometer was used to acquire 314 series of measurements spanning 38 days. The sunphotometer was pre-calibrated at the NASA Goddard Space Flight Center against a master sun/sky radiometer instrument of the Aerosol Robotic Network (AERONET). The direct sun measurements were acquired in five spectral channels: 340, 440, 675, 870 and 940 nm. To retrieve aerosol optical depths we applied AERONET processing algorithm (Version 2) to the raw data. Aerosol optical depth values were close to background oceanic conditions (0.04-0.08) in the open oceanic areas not influenced by continental sources. Spectral dependence can be described as almost neutral (Angstrom parameter was less than 0.6), especially in the Southern Atlantic. A notable latitudinal variability of optical depth was observed between 15N and 21S, which was associated with the aerosol transport from Africa. Correlations between optical depth and meteorological parameters were considered and comparison between ship-based measurements and AERONET sites along the cruise track was made. Aerosol optical depths were compared to the global transport model (GOCART) simulations and satellite retrievals from MODIS, MISR, and AVHRR.

  13. Double Feedforward Control System Based on Precise Disturbance Modeling for Optical Disk

    NASA Astrophysics Data System (ADS)

    Sakimura, Naohide; Nakazaki, Tatsuya; Ohishi, Kiyoshi; Miyazaki, Toshimasa; Koide, Daiichi; Tokumaru, Haruki; Takano, Yoshimichi

    2013-09-01

    Optical disk drive systems must realize high-precision tracking control for their proper operation. For this purpose, we previously proposed a tracking control system that is composed of a high-gain servo controller (HGSC) and a feedforward controller with an equivalent-perfect tracking control (E-PTC) system. However, it is difficult to design the control parameter for actual multi-harmonic disturbances. In this paper, we propose a precise disturbance model of an actual optical disk using the experimental spectrum data of a feedback controller and describe the design of a fine tracking control system. In addition, we propose a double feedforward control (DFFC) system for further high-precision control. The proposed DFFC system is constructed using two zero phase error tracking (ZPET) control systems based on error prediction and trajectory command prediction. Our experimental results confirm that the proposed system effectively suppresses the tracking error at 6000 rpm, which is the disk rotation speed of Digital Versatile Disk Recordable (DVD+R).

  14. Composite axilens-axicon diffractive optical elements for generation of ring patterns with high focal depth

    NASA Astrophysics Data System (ADS)

    Dharmavarapu, Raghu; Vijayakumar, A.; Brunner, R.; Bhattacharya, Shanti

    2016-03-01

    A binary Fresnel Zone Axilens (FZA) is designed for the infinite conjugate mode and the phase profile of a refractive axicon is combined with it to generate a composite Diffractive Optical Element (DOE). The FZA designed for two focal lengths generates a line focus along the propagation direction extending between the two focal planes. The ring pattern generated by the axicon is focused through this distance and the radius of the ring depends on the propagation distance. Hence, the radius of the focused ring pattern can be tuned, during the design process, within the two focal planes. The integration of the two functions was carried out by shifting the location of zones of FZA with respect to the phase profile of the refractive axicon resulting in a binary composite DOE. The FZAs and axicons were designed for different focal depth values and base angles respectively, in order to achieve different ring radii within the focal depth of each element. The elements were simulated using scalar diffraction formula and their focusing characteristics were analyzed. The DOEs were fabricated using electron beam direct writing and evaluated using a fiber coupled diode laser. The tunable ring patterns generated by the DOEs have prospective applications in microdrilling as well as microfabrication of circular diffractive and refractive optical elements.

  15. CALIOP and AERONET Aerosol Optical Depth Comparisons: One Size Fits None

    NASA Technical Reports Server (NTRS)

    Omar, A. H.; Winker, D. M.; Tackett, J. L.; Giles, D. M.; Kar, J.; Liu, Z.; Vaughan, M. A.; Powell, K. A.; Trepte, C. R.

    2013-01-01

    We compare the aerosol optical depths (AOD) retrieved from backscatter measurements of the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) satellite with coincident Aerosol Robotic Network (AERONET) measurements. Overpass coincidence criteria of +/- 2 h and within a 40 km radius are satisfied at least once at 149 globally distributed AERONET sites from 2006 to 2010. Most data pairs (>80%) use AERONET measurements acquired +/- 30 min of the overpass. We examine the differences in AOD estimates between CALIOP and AERONET for various aerosol, environmental, and geographic conditions. Results show CALIOP AOD are lower than AERONET AOD especially at low optical depths as measured by AERONET (500 nm AOD<0.1). Furthermore, the median relative AOD difference between the two measurements is 25% of the AERONET AOD for AOD>0.1. Differences in AOD between CALIOP and AERONET are possibly due to cloud contamination, scene inhomogeneity, instrument view angle differences, CALIOP retrieval errors, and detection limits. Comparison of daytime to nighttime number of 5 km 60m (60m in the vertical) features detected by CALIOP show that there are 20% more aerosol features at night. We find that CALIPSO and AERONET do not agree on the cloudiness of scenes. Of the scenes that meet the above coincidence criteria, CALIPSO finds clouds in more than 45% of the coincident atmospheric columns AERONET classifies as clear.

  16. Aerosol Optical Depth at Cape Grim 1986 - 2014: What does it tell us?

    NASA Astrophysics Data System (ADS)

    Wilson, Stephen

    2015-04-01

    The Cape Grim Baseline Air Pollution Station is located near the northwest tip of Tasmania (Australia), a site chosen to permit measurement of the atmospheric environment over the southern oceans. Atmospheric measurements began in the late 1970s, and observations of Aerosol Optical Depth (AOD) using automated sunphotometers began in 1986. Since then, measurements have continued with a range of different instruments operating at a varying number of wavelengths. The site is challenging for these measurements as it is exposed to a sea-salt laden atmosphere, which presents both instrumental issues (corrosion) and measurement complications (salt fouling of the windows) in addition to the high frequency of cloud. The dataset has been processed to produce a record of half-hourly AOD for the period 1986 - 2014 and investigated for internal consistency. In general the AOD is small (around 0.05 at 500nm). The impact of the Mount Pinatubo eruption in 1991 can be clearly observed, along with a persistent annual cycle. This has been further analyzed fitting to all wavelengths measured to derive an averaged optical depth (at 500 nm) and some preliminary aerosol size distribution information.

  17. THEMIS observations of Mars aerosol optical depth from 2002-2008

    NASA Astrophysics Data System (ADS)

    Smith, Michael D.

    2009-08-01

    We use infrared images obtained by the Thermal Emission Imaging System (THEMIS) instrument on-board Mars Odyssey to retrieve the optical depth of dust and water ice aerosols over more than 3.5 martian years between February 2002 (MY 25, L=330°) and December 2008 (MY 29, L=183°). These data provide an important bridge between earlier TES observations and recent observations from Mars Express and Mars Reconnaissance Orbiter. An improvement to our earlier retrieval [Smith, M.D., Bandfield, J.L., Christensen, P.R., Richardson, M.I., 2003. J. Geophys. Res. 108, doi:10.1029/2003JE002114] to include atmospheric temperature information from THEMIS Band 10 observations leads to much improved retrievals during the largest dust storms. The new retrievals show moderate dust storm activity during Mars Years 26 and 27, although details of the strength and timing of dust storms is different from year to year. A planet-encircling dust storm event was observed during Mars Year 28 near Southern Hemisphere Summer solstice. A belt of low-latitude water ice clouds was observed during the aphelion season during each year, Mars Years 26 through 29. The optical depth of water ice clouds is somewhat higher in the THEMIS retrievals at ˜5:00 PM local time than in the TES retrievals at ˜2:00 PM, suggestive of possible local time variation of clouds.

  18. CALIOP and AERONET Aerosol Optical Depth Comparisons: One Size Fits None

    NASA Technical Reports Server (NTRS)

    Omar, A. H.; Winker, D. M.; Tackett, J. L.; Giles, D. M.; Kar, J.; Liu, Z.; Vaughan, M. A.; Powell, K. A.; Trepte, C. R.

    2013-01-01

    We compare the aerosol optical depths (AOD) retrieved from backscatter measurements of the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) satellite with coincident Aerosol Robotic Network (AERONET) measurements. Overpass coincidence criteria of +/- 2 h and within a 40 km radius are satisfied at least once at 149 globally distributed AERONET sites from 2006 to 2010. Most data pairs (>80%) use AERONET measurements acquired +/- 30 min of the overpass. We examine the differences in AOD estimates between CALIOP and AERONET for various aerosol, environmental, and geographic conditions. Results show CALIOP AOD are lower than AERONET AOD especially at low optical depths as measured by AERONET (500 nm AOD<0.1). Furthermore, the median relative AOD difference between the two measurements is 25% of the AERONET AOD for AOD>0.1. Differences in AOD between CALIOP and AERONET are possibly due to cloud contamination, scene inhomogeneity, instrument view angle differences, CALIOP retrieval errors, and detection limits. Comparison of daytime to nighttime number of 5 km 60m (60m in the vertical) features detected by CALIOP show that there are 20% more aerosol features at night. We find that CALIPSO and AERONET do not agree on the cloudiness of scenes. Of the scenes that meet the above coincidence criteria, CALIPSO finds clouds in more than 45% of the coincident atmospheric columns AERONET classifies as clear.

  19. The Origin and Optical Depth of Ionizing Photons in the Green Pea Galaxies

    NASA Astrophysics Data System (ADS)

    Jaskot, A. E.; Oey, M. S.

    2014-09-01

    Our understanding of radiative feedback and star formation in galaxies at high redshift is hindered by the rarity of similar systems at low redshift. However, the recently identified Green Pea (GP) galaxies are similar to high-redshift galaxies in their morphologies and star formation rates and are vital tools for probing the generation and transmission of ionizing photons. The GPs contain massive star clusters that emit copious amounts of high-energy radiation, as indicated by intense [OIII] 5007 emission and HeII 4686 emission. We focus on six GP galaxies with high ratios of [O III] 5007,4959/[O II] 3727 ~10 or more. Such high ratios indicate gas with a high ionization parameter or a low optical depth. The GP line ratios and ages point to chemically homogeneous massive stars, Wolf-Rayet stars, or shock ionization as the most likely sources of the He II emission. Models including shock ionization suggest that the GPs may have low optical depths, consistent with a scenario in which ionizing photons escape along passageways created by recent supernovae. The GPs and similar galaxies can shed new light on cosmic reionization by revealing how ionizing photons propagate from massive star clusters to the intergalactic medium.

  20. THEMIS Observations of Mars Aerosol Optical Depth from 2002-2008

    NASA Technical Reports Server (NTRS)

    Smith, Michael D.

    2009-01-01

    We use infrared images obtained by the Thermal Emission Imaging System (THEMIS) instrument on-board Mars Odyssey to retrieve the optical depth of dust and water ice aerosols over more than 3.5 martian years between February 2002 (MY 25, Ls=330 ) and December 2008 (MY 29, Ls=183). These data provide an important bridge between earlier TES observations and recent observations from Mars Express and Mars Reconnaissance Orbiter. An improvement to our earlier retrieval to include atmospheric temperature information from THEMIS Band 10 observations leads to much improved retrievals during the largest dust storms. The new retrievals show moderate dust storm activity during Mars Years 26 and 27, although details of the strength and timing of dust storms is different from year to year. A planet-encircling dust storm event was observed during Mars Year 28 near Southern Hemisphere Summer solstice. A belt of low-latitude water ice clouds was observed during the aphelion season during each year, Mars Years 26 through 29. The optical depth of water ice clouds is somewhat higher in the THEMIS retrievals at approximately 5:00 PM local time than in the TES retrievals at approximately 2:00 PM, suggestive of possible local time variation of clouds.

  1. Precise age for the Permian-Triassic boundary in South China from high-precision U-Pb geochronology and Bayesian age-depth modeling

    NASA Astrophysics Data System (ADS)

    Baresel, Björn; Bucher, Hugo; Brosse, Morgane; Cordey, Fabrice; Guodun, Kuang; Schaltegger, Urs

    2017-03-01

    This study is based on zircon U-Pb ages of 12 volcanic ash layers and volcanogenic sandstones from two deep water sections with conformable and continuous formational Permian-Triassic boundaries (PTBs) in the Nanpanjiang Basin (South China). Our dates of single, thermally annealed and chemically abraded zircons bracket the PTB in Dongpan and Penglaitan and provide the basis for a first proof-of-concept study utilizing a Bayesian chronology model comparing the three sections of Dongpan, Penglaitan and the Global Stratotype Section and Point (GSSP) at Meishan. Our Bayesian modeling demonstrates that the formational boundaries in Dongpan (251.939 ± 0.030 Ma), Penglaitan (251.984 ± 0.031 Ma) and Meishan (251.956 ± 0.035 Ma) are synchronous within analytical uncertainty of ˜ 40 ka. It also provides quantitative evidence that the ages of the paleontologically defined boundaries, based on conodont unitary association zones in Meishan and on macrofaunas in Dongpan, are identical and coincide with the age of the formational boundaries. The age model also confirms the extreme condensation around the PTB in Meishan, which distorts the projection of any stratigraphic points or intervals onto other more expanded sections by means of Bayesian age-depth models. Dongpan and Penglaitan possess significantly higher sediment accumulation rates and thus offer a greater potential for high-resolution studies of environmental proxies and correlations around the PTB than Meishan. This study highlights the power of high-resolution radio-isotopic ages that allow a robust intercalibration of patterns of biotic changes and fluctuating environmental proxies and will help recognizing their global, regional or local significance.

  2. High-precision, accurate optical frequency reference using a Fabry-Perót diode laser

    NASA Astrophysics Data System (ADS)

    Chang, Hongrok; Myneni, Krishna; Smith, David D.; Liaghati-Mobarhan, Hassan R.

    2017-06-01

    We show that the optical output of a temperature and current-tuned Fabry-Perót diode laser system, with no external optical feedback and in which the frequency is locked to Doppler-free hyperfine resonances of the 87Rb D2 line, can achieve high frequency stability and accuracy. Experimental results are presented for the spectral linewidth, frequency stability, and frequency accuracy of the source. Although our optical source is limited by a short-term spectral linewidth greater than 2 MHz, beat signal measurements from two such sources demonstrate a frequency stability of 1.1 kHz, or minimum Allan deviation of 4 ×1 0-12, at an integration time τ =15 s and with a frequency accuracy of 60 kHz at τ =300 s. We demonstrate the use of the optical source for the precision measurement of hyperfine level frequency spacings in the 5 P3 /2 excited state of 87Rb and provide an accurate frequency scale for optical spectroscopy.

  3. Precision assembly and alignment of large optic modules for the National Ignition Facility

    SciTech Connect

    Hurst, P.; Grasz, E.

    1998-05-12

    The National Ignition Facility (NIF), currently under design and construction at Lawrence Livermore National Laboratory (LLNL), will be the world`s biggest laser. The optics for the multipass, 192-beam, high-power, neodymium-glass laser will be assembled and aligned in the NIF Optics Assembly Building (OAB), adjacent to the huge Laser and Target Area Building (LTAB), where they will be installed. To accommodate the aggressive schedule for initial installation and activation, rapid assembly and alignment of large aperture optics into line replaceable units (LRUs) will occur through the use of automated handling, semi-autonomous operations, and strict protocols. The OAB will have to maintain rigorous cleanliness levels, achieve both commonality and versatility to handle the various optic types, and allow for just-in-time processing and delivery of the optics into the LTAB without undoing their strict cleanliness and precise alignment. This paper describes the Project`s design philosophy of modularity and hardware commonality and presents the many design challenges encountered. It also describes how, by using a mixture of commercially available and newly designed equipment, we have developed unique systems for assembly and alignment, inspection and verification, and LRU loading and transfer.

  4. Ultra-high modulation depth exceeding 2,400% in optically controlled topological surface plasmons

    PubMed Central

    Sim, Sangwan; Jang, Houk; Koirala, Nikesh; Brahlek, Matthew; Moon, Jisoo; Sung, Ji Ho; Park, Jun; Cha, Soonyoung; Oh, Seongshik; Jo, Moon-Ho; Ahn, Jong-Hyun; Choi, Hyunyong

    2015-01-01

    Modulating light via coherent charge oscillations in solids is the subject of intense research topics in opto-plasmonics. Although a variety of methods are proposed to increase such modulation efficiency, one central challenge is to achieve a high modulation depth (defined by a ratio of extinction with/without light) under small photon-flux injection, which becomes a fundamental trade-off issue both in metals and semiconductors. Here, by fabricating simple micro-ribbon arrays of topological insulator Bi2Se3, we report an unprecedentedly large modulation depth of 2,400% at 1.5 THz with very low optical fluence of 45 μJ cm−2. This was possible, first because the extinction spectrum is nearly zero due to the Fano-like plasmon–phonon-destructive interference, thereby contributing an extremely small denominator to the extinction ratio. Second, the numerator of the extinction ratio is markedly increased due to the photoinduced formation of massive two-dimensional electron gas below the topological surface states, which is another contributor to the ultra-high modulation depth. PMID:26514372

  5. Ultra-high modulation depth exceeding 2,400% in optically controlled topological surface plasmons.

    PubMed

    Sim, Sangwan; Jang, Houk; Koirala, Nikesh; Brahlek, Matthew; Moon, Jisoo; Sung, Ji Ho; Park, Jun; Cha, Soonyoung; Oh, Seongshik; Jo, Moon-Ho; Ahn, Jong-Hyun; Choi, Hyunyong

    2015-10-30

    Modulating light via coherent charge oscillations in solids is the subject of intense research topics in opto-plasmonics. Although a variety of methods are proposed to increase such modulation efficiency, one central challenge is to achieve a high modulation depth (defined by a ratio of extinction with/without light) under small photon-flux injection, which becomes a fundamental trade-off issue both in metals and semiconductors. Here, by fabricating simple micro-ribbon arrays of topological insulator Bi2Se3, we report an unprecedentedly large modulation depth of 2,400% at 1.5 THz with very low optical fluence of 45 μJ cm(-2). This was possible, first because the extinction spectrum is nearly zero due to the Fano-like plasmon-phonon-destructive interference, thereby contributing an extremely small denominator to the extinction ratio. Second, the numerator of the extinction ratio is markedly increased due to the photoinduced formation of massive two-dimensional electron gas below the topological surface states, which is another contributor to the ultra-high modulation depth.

  6. A Precision Optical Calibration Module (POCAM) for IceCube-Gen2

    NASA Astrophysics Data System (ADS)

    Jurkovič, M.; Abraham, K.; Holzapfel, K.; Krings, K.; Resconi, E.; Veenkamp, J.

    2016-04-01

    We present here a new concept of an in-situ self-calibrated isotropic light source for the future IceCube-Gen2 neutrino detector called the Precision Optical Calibration Module (POCAM). IceCube-Gen2 will be a matrix of light sensors buried deep in the ice at the geographic South Pole. The timing, the location, and the amount of Cherenkov light deposited by the secondary charged particles are used to reconstruct the properties of the incident neutrinos. The reconstruction relies on a detailed detector model that includes the response of optical modules to the Cherenkov light, as well as the optical properties of the detector medium - the natural Antarctic ice. To understand these properties, both natural, and artificial light sources are already used for calibration. New calibration devices are being developed in order to improve the precision of these measurements, and reduce systematic errors. The POCAM concept is based on the principle of an inverted integrating sphere. The main components are LEDs emitting light at several wavelengths and solid-state light sensors e.g. calibrated photodiode or silicon photomultipliers to monitor the emitted light intensity. We report on the current status of the POCAM R&D.

  7. Nonisothermal glass molding for the cost-efficient production of precision freeform optics

    NASA Astrophysics Data System (ADS)

    Vu, Anh-Tuan; Kreilkamp, Holger; Dambon, Olaf; Klocke, Fritz

    2016-07-01

    Glass molding has become a key replication-based technology to satisfy intensively growing demands of complex precision optics in the today's photonic market. However, the state-of-the-art replicative technologies are still limited, mainly due to their insufficiency to meet the requirements of mass production. This paper introduces a newly developed nonisothermal glass molding in which a complex-shaped optic is produced in a very short process cycle. The innovative molding technology promises a cost-efficient production because of increased mold lifetime, less energy consumption, and high throughput from a fast process chain. At the early stage of the process development, the research focuses on an integration of finite element simulation into the process chain to reduce time and labor-intensive cost. By virtue of numerical modeling, defects including chill ripples and glass sticking in the nonisothermal molding process can be predicted and the consequent effects are avoided. In addition, the influences of process parameters and glass preforms on the surface quality, form accuracy, and residual stress are discussed. A series of experiments was carried out to validate the simulation results. The successful modeling, therefore, provides a systematic strategy for glass preform design, mold compensation, and optimization of the process parameters. In conclusion, the integration of simulation into the entire nonisothermal glass molding process chain will significantly increase the manufacturing efficiency as well as reduce the time-to-market for the mass production of complex precision yet low-cost glass optics.

  8. On the assimilation of optical reflectances and snow depth observations into a detailed snowpack model

    NASA Astrophysics Data System (ADS)

    Charrois, Luc; Cosme, Emmanuel; Dumont, Marie; Lafaysse, Matthieu; Morin, Samuel; Libois, Quentin; Picard, Ghislain

    2016-05-01

    This paper examines the ability of optical reflectance data assimilation to improve snow depth and snow water equivalent simulations from a chain of models with the SAFRAN meteorological model driving the detailed multilayer snowpack model Crocus now including a two-stream radiative transfer model for snow, TARTES. The direct use of reflectance data, allowed by TARTES, instead of higher level snow products, mitigates uncertainties due to commonly used retrieval algorithms.Data assimilation is performed with an ensemble-based method, the Sequential Importance Resampling Particle filter, to represent simulation uncertainties. In snowpack modeling, uncertainties of simulations are primarily assigned to meteorological forcings. Here, a method of stochastic perturbation based on an autoregressive model is implemented to explicitly simulate the consequences of these uncertainties on the snowpack estimates.Through twin experiments, the assimilation of synthetic spectral reflectances matching the MODerate resolution Imaging Spectroradiometer (MODIS) spectral bands is examined over five seasons at the Col du Lautaret, located in the French Alps. Overall, the assimilation of MODIS-like data reduces by 45 % the root mean square errors (RMSE) on snow depth and snow water equivalent. At this study site, the lack of MODIS data on cloudy days does not affect the assimilation performance significantly. The combined assimilation of MODIS-like reflectances and a few snow depth measurements throughout the 2010/2011 season further reduces RMSEs by roughly 70 %. This work suggests that the assimilation of optical reflectances has the potential to become an essential component of spatialized snowpack simulation and forecast systems. The assimilation of real MODIS data will be investigated in future works.

  9. An optical fiber multiplexing interferometric system for measuring remote and high precision step height

    NASA Astrophysics Data System (ADS)

    Wang, Yunzhi; Xie, Fang; Ma, Sen; Chen, Liang

    2015-02-01

    In this paper, an optical fiber multiplexing interferometric system including a Fizeau interferometer and a Michelson interferometer is designed for remote and high precision step height measurement. The Fizeau interferometer which is inserted in the remote sensing field is used for sensing the measurand, while the Michelson interferometer which is stabilized by a feedback loop works in both modes of low coherence interferometry and high coherence interferometry to demodulate the measurand. The range of the step height is determined by the low coherence interferometry and the value of it is measured precisely by the high coherence interferometry. High precision has been obtained by using the symmetrical peak-searching method to address the peak of the low coherence interferogram precisely and stabilizing the Michelson interferometer with a feedback loop. The maximum step height that could be measured is 6 mm while the measurement resolution is less than 1 nm. The standard deviation of 10 times measurement results of a step height of 1 mm configurated with two gauge blocks is 0.5 nm.

  10. Remote and high precision step height measurement with an optical fiber multiplexing interferometric system

    NASA Astrophysics Data System (ADS)

    Wang, Yunzhi; Xie, Fang; Ma, Sen; Chen, Liang

    2015-03-01

    An optical fiber multiplexing low coherence and high coherence interferometric system, which includes a Fizeau interferometer as the sensing element and a Michelson interferometer as the demodulating element, is designed for remote and high precision step height measurement. The Fizeau interferometer is placed in the remote field for sensing the measurand, while the Michelson interferometer which works in both modes of low coherence interferometry and high coherence interferometry is employed for demodulating the measurand. The range of the step height is determined by the low coherence interferometry and the value of it is measured precisely by the high coherence interferometry. High precision has been obtained by searching precisely the peak of the low coherence interferogram symmetrically from two sides of the low coherence interferogram and stabilizing the Michelson interferometer with a feedback loop. The maximum step height that could be measured is 6 mm while the measurement resolution is less than 1 nm. The standard deviation of 10 times measurement results of a step height of 1 mm configurated with two gauge blocks is 0.5 nm.

  11. Enhanced Depth Imaging of Central Laminar Thickness in Optic Neuropathy: Comparison with Normal Eyes.

    PubMed

    Thitiwichienlert, Suntaree; Ishikawa, Hitoshi; Asakawa, Ken; Ikeda, Tetsuya; Shimizu, Kimiya

    2015-08-01

    The purpose of this study was to compare central laminar thickness (LT) among patients with glaucomatous optic neuropathy (GON), patients with non-GON, and normal subjects using enhanced-depth imaging optical coherence tomography (EDI-OCT). Enrolled were 57 patients (n = 64 eyes), including 30 women and 27 men. Three groups were identified: GON (n = 18 eyes), non-GON (n = 16 eyes), and control (n = 30 eyes). The GON group comprised eyes with primary open-angle glaucoma (POAG) (n = 9) and normal-tension glaucoma (NTG) (n = 9). The non-GON group comprised eyes with demyelinating optic neuritis (n = 9), anterior ischemic optic neuropathy (AION) (n = 2), compressive ON (n = 2), Leber hereditary ON (n = 2), and traumatic ON (n = 1). GON and non-GON groups were further divided into mild, moderate, and severe subgroups. Inclusion in the GON group was based on mean deviations (MDs) of visual fields; inclusion in the non-GON group was based on critical flicker frequency (CFF) responses. Intraclass correlation coefficients (ICCs) were used to verify reproducibility of measurements. LTs of GON and non-GON group eyes were thinner than those of control group eyes (p < 0.01); LTs of GON group eyes were thinner than those of non-GON group eyes (p = 0.01). LTs of severe GON subgroup eyes were thinner than those of moderate and mild GON subgroup eyes (p < 0.001; p = 0.024, respectively). LTs of severe non-GON subgroup eyes were thinner than those of mild non-GON subgroup eyes (p = 0.002). These results show that EDI-OCT is valuable for documenting structural abnormalities in optic neuropathy (ON).

  12. Precise determination of atomic g-factor ratios from a dual isotope magneto-optical trap

    SciTech Connect

    Chan, I.; Barrett, B.; Kumarakrishnan, A.

    2011-09-15

    We demonstrate a technique, for carrying out precise measurements of atomic g-factor ratios, which relies on measurements of Larmor oscillations from coherences between magnetic sublevels in the ground states of {sup 85}Rb and {sup 87}Rb atoms confined in a dual isotope magneto-optical trap. We show that a measurement of g{sub F}{sup (87)}/g{sub F}{sup (85)} with a resolution of 0.69 parts per 10{sup 6} is possible by recording the ratio of Larmor frequencies in the presence of a constant magnetic field. This represents the most precise single measurement of g{sub F}{sup (87)}/g{sub F}{sup (85)} without correcting for systematic effects.

  13. Method of optical coherence tomography with parallel depth-resolved signal reception and fibre-optic phase modulators

    SciTech Connect

    Morozov, A N; Turchin, I V

    2013-12-31

    The method of optical coherence tomography with the scheme of parallel reception of the interference signal (P-OCT) is developed on the basis of spatial paralleling of the reference wave by means of a phase diffraction grating producing the appropriate time delay in the Mach–Zehnder interferometer. The absence of mechanical variation of the optical path difference in the interferometer essentially reduces the time required for 2D imaging of the object internal structure, as compared to the classical OCT that uses the time-domain method of the image construction, the sensitivity and the dynamic range being comparable in both approaches. For the resulting field of the interfering object and reference waves an analytical expression is derived that allows the calculation of the autocorrelation function in the plane of photodetectors. For the first time a method of linear phase modulation by 2π is proposed for P-OCT systems, which allows the use of compact high-frequency (a few hundred kHz) piezoelectric cell-based modulators. For the demonstration of the P-OCT method an experimental setup was created, using which the images of the inner structure of biological objects at the depth up to 1 mm with the axial spatial resolution of 12 μm were obtained. (optical coherence tomography)

  14. RBS measurement of depth profiles of erbium incorporated into lithium niobate for optical amplifier applications

    NASA Astrophysics Data System (ADS)

    Peřina, Vratislav; Vacík, Jiří; Hnatovicz, Vladimír.; Červená, Jarmila; Kolářová, Pavla; Špirková-Hradilová, Jarmila; Schröfel, Josef

    1998-04-01

    Rutherford Backscattering Spectrometry (RBS) was used for the determination of Er 3+ concentration profiles in locally doped lithium niobate. The doped layers are the basic substrates for the fabrication of optical waveguiding structures which may be utilized as planar optical amplifiers and waveguiding lasers making use of the 4I 13/2 → 4I 15/2 transition in Er 3+, which falls into the third low loss telecommunication window (1.5 μm). We present a new aproach of fabrication of locally doped lithium niobate single crystal wafers. The doping occurs under moderate temperature (˜350°C) from reaction melts containing ca. 10 wt% of erbium nitrate. The erbium content in particular cuts varies dramatically between ca. 3 at.% in the Y- and Z-cut up to 20 at.% in the X-cuts. Erbium ions are localized in a 50 nm thick layer, but they can be diffused deeper into the substrate by subsequent annealing at 350°C. The Er concentrations of the samples doped at moderated temperature are compared with the Er concentrations of the samples doped by a standard high-temperature diffusion (>1000°C) from evaporated metal layers. To utilize the Er doped substrates in integrated optic circuits high quality waveguides must be subsequently fabricated. For that we used the Annealed Proton Exchange (APE) method with adipic acid. For the actual fabrication of the waveguides the following order of operation should be kept: the erbium doping should be done before the APE because the substantially changed structure of APE layers prevents the doping process. The APE process is checked by measurements of lithium depth profiles by Neutron Depth Profiling (NDP).

  15. Optical depth of the Martian atmosphere and surface albedo from high-resolution orbiter images

    NASA Astrophysics Data System (ADS)

    Petrova, E. V.; Hoekzema, N. M.; Markiewicz, W. J.; Thomas, N.; Stenzel, O. J.

    2012-01-01

    In this paper we describe and evaluate the so-called shadow method. This method can be used to estimate the optical depth of the Martian atmosphere from the differences in brightness between shadowed and sunlit regions observed from an orbiter. We present elaborate and simplified versions of the method and analyze the capabilities and the sources of errors. It proves essential to choose shadowed and sunlit comparison regions with similar surface properties. Accurate knowledge of the observing geometry, including the slopes of the observed region, is important as well, since the procedure should be corrected for the non-horizontal surface. Moreover, the elaborate version of the shadow method can be sensitive to (i) the optical model of aerosols and (ii) the assumed bi-directional reflectance function of the surface. To obtain reliable estimates, the analyzed images must have a high spatial resolution, which the HiRISE camera onboard the MRO provides. We tested the shadow method on two HiRISE images of Victoria crater (TRA_0873_1780 and PSP_001414_1780) that were taken while this crater was the exploration site of the Opportunity rover. While the rover measured optical depth τ approximately in the ranges from 0.43 to 0.53 and from 0.53 to 0.59 by imaging the sun, our shadow procedure yielded τ about 0.50 and 0.575, respectively (from the HiRISE's red images). Thus, the agreement is quite good. The obtained estimates of the surface albedo are about 0.20 and 0.17, respectively.

  16. Precise in situ etch depth control of multilayered III−V semiconductor samples with reflectance anisotropy spectroscopy (RAS) equipment

    PubMed Central

    Kleinschmidt, Ann-Kathrin; Barzen, Lars; Strassner, Johannes; Doering, Christoph; Bock, Wolfgang; Wahl, Michael; Kopnarski, Michael

    2016-01-01

    Reflectance anisotropy spectroscopy (RAS) equipment is applied to monitor dry-etch processes (here specifically reactive ion etching (RIE)) of monocrystalline multilayered III–V semiconductors in situ. The related accuracy of etch depth control is better than 16 nm. Comparison with results of secondary ion mass spectrometry (SIMS) reveals a deviation of only about 4 nm in optimal cases. To illustrate the applicability of the reported method in every day settings for the first time the highly etch depth sensitive lithographic process to form a film lens on the waveguide ridge of a broad area laser (BAL) is presented. This example elucidates the benefits of the method in semiconductor device fabrication and also suggests how to fulfill design requirements for the sample in order to make RAS control possible. PMID:28144528

  17. Depth discrimination in acousto-optic cerebral blood flow measurement simulation

    NASA Astrophysics Data System (ADS)

    Tsalach, A.; Schiffer, Z.; Ratner, E.; Breskin, I.; Zeitak, R.; Shechter, R.; Balberg, M.

    2016-03-01

    Monitoring cerebral blood flow (CBF) is crucial, as inadequate perfusion, even for relatively short periods of time, may lead to brain damage or even death. Thus, significant research efforts are directed at developing reliable monitoring tools that will enable continuous, bed side, simple and cost-effective monitoring of CBF. All existing non invasive bed side monitoring methods, which are mostly NIRS based, such as Laser Doppler or DCS, tend to underestimate CBF in adults, due to the indefinite effect of extra-cerebral tissues on the obtained signal. If those are to find place in day to day clinical practice, the contribution of extra-cerebral tissues must be eliminated and data from the depth (brain) should be extracted and discriminated. Recently, a novel technique, based on ultrasound modulation of light was developed for non-invasive, continuous CBF monitoring (termed ultrasound-tagged light (UTL or UT-NIRS)), and shown to correlate with readings of 133Xe SPECT and laser Doppler. We have assembled a comprehensive computerized simulation, modeling this acousto-optic technique in a highly scattering media. Using the combination of light and ultrasound, we show how depth information may be extracted, thus distinguishing between flow patterns taking place at different depths. Our algorithm, based on the analysis of light modulated by ultrasound, is presented and examined in a computerized simulation. Distinct depth discrimination ability is presented, suggesting that using such method one can effectively nullify the extra-cerebral tissues influence on the obtained signals, and specifically extract cerebral flow data.

  18. Focusing of photomechanical waves with an optical lens for depth-targeted molecular delivery

    NASA Astrophysics Data System (ADS)

    Shimada, Takuichirou; Sato, Shunichi; Kawauchi, Satoko; Ashida, Hiroshi; Terakawa, Mitsuhiro

    2014-02-01

    We have been developing molecular delivery systems based on photomechanical waves (PMWs), which are generated by the irradiation of a laser absorbing material with nanosecond laser pulses. This method enables highly site-specific delivery in the horizontal plane of the tissue. However, targeting in the vertical direction is a remaining challenge. In this study, we developed a novel PMW focusing device for deeper tissue targeting. A commercial optical concave lens and black natural rubber sheet (laser absorber) were attached to the top and bottom end of a cylindrical spacer, respectively, which was filled with water. A laser pulse was transmitted through the lens and water and hit the rubber sheet to induce a plasma, generating a PMW. The PMW was propagated both downward and upward. The downward wave (1st wave) was diffused, while the upward (2nd wave) wave was reflected with the concave surface of the lens and focused at a depth determined by the geometrical parameters. To attenuate the 1st wave, a small-diameter silicon sponge rubber disk was adhered just under the rubber sheet concentrically with the laser axis. With the lens of f = -40 mm, the 2nd wave was focused to a diameter of 5.7 mm at a targeted depth of 20 mm, which was well agreed with the result of calculation by ray tracing. At a laser fluence of 5.1 J/cm2, peak pressure of the PMW reached ~40 MPa at the depth of 20 mm. Under this condition, we examined depth-targeted gene delivery to the rat skin.

  19. Ultrahigh resolution optical coherence elastography using a Bessel beam for extended depth of field

    NASA Astrophysics Data System (ADS)

    Curatolo, Andrea; Villiger, Martin; Lorenser, Dirk; Wijesinghe, Philip; Fritz, Alexander; Kennedy, Brendan F.; Sampson, David D.

    2016-03-01

    Visualizing stiffness within the local tissue environment at the cellular and sub-cellular level promises to provide insight into the genesis and progression of disease. In this paper, we propose ultrahigh-resolution optical coherence elastography, and demonstrate three-dimensional imaging of local axial strain of tissues undergoing compressive loading. The technique employs a dual-arm extended focus optical coherence microscope to measure tissue displacement under compression. The system uses a broad bandwidth supercontinuum source for ultrahigh axial resolution, Bessel beam illumination and Gaussian beam detection, maintaining sub-2 μm transverse resolution over nearly 100 μm depth of field, and spectral-domain detection allowing high displacement sensitivity. The system produces strain elastograms with a record resolution (x,y,z) of 2×2×15 μm. We benchmark the advances in terms of resolution and strain sensitivity by imaging a suitable inclusion phantom. We also demonstrate this performance on freshly excised mouse aorta and reveal the mechanical heterogeneity of vascular smooth muscle cells and elastin sheets, otherwise unresolved in a typical, lower resolution optical coherence elastography system.

  20. Precise measurement of instantaneous volume of eccrine sweat gland in mental sweating by optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Sugawa, Yoshihiko; Fukuda, Akihiro; Ohmi, Masato

    2015-03-01

    We have demonstrated dynamic analysis of the physiological function of eccrine sweat glands underneath skin surface by optical coherence tomography (OCT). We propose a method for extraction of the target eccrine sweat gland by use of the connected component extraction process and the adaptive threshold method, where the en-face OCT images are constructed by the SS-OCT. Furthermore, we demonstrate precise measurement of instantaneous volume of the sweat gland in response to the external stimulus. The dynamic change of instantaneous volume of eccrine sweat gland in mental sweating is performed by this method during the period of 300 sec with the frame intervals of 3.23 sec.

  1. High precision long-term stable fiber-based optical synchronization system

    NASA Astrophysics Data System (ADS)

    Li, Yurong; Wang, Xiaochao; Jiang, Youen; Qiao, Zhi; Li, Rao; Fan, Wei

    2016-10-01

    A fiber-based high precision long-term stable time synchronization system for multi-channel laser pulses is presented using fiber pulse stacker combined with high-speed optical-electrical conversion and electronics processing technology. This scheme is used to synchronize two individual lasers including a mode-lock laser and a time shaping pulse laser system. The relative timing jitter between two laser pulses achieved with this system is 970 fs (rms) in five minutes and 3.5 ps (rms) in five hours. The synchronization system is low cost and can work at over several tens of MHz repetition rate.

  2. Multiple-Baseline Detection of a Geostationary Satellite with the Navy Precision Optical Interferometer

    NASA Astrophysics Data System (ADS)

    Schmitt, H.; Armstrong, J. T.; Baines, E. K.; Restaino, S. R.; Clark, J. H., III; Benson, J. A.; Hutter, D. J.; Zavala, R. T.

    Using the Navy Precision Optical Interferometer (NPOI), we have made the first multiple-baseline interferometric detection of a satellite. The observations, carried out during the March 2015 glint season, succeeded in detecting the DirecTV-7S satellite with interferometer baseline lengths of 8.8 m and 9.8 m and wavelengths from 850 nm to 550 nm, corresponding to a resolution of ~0.02 arcsec, or 4 m at geostationary altitude. This is the first multiple-baseline interferometric detection of a satellite.

  3. Multiple-baseline detection of a geostationary satellite with the Navy Precision Optical Interferometer

    NASA Astrophysics Data System (ADS)

    Armstrong, J. T.; Baines, Ellyn K.; Schmitt, Henrique R.; Restaino, Sergio R.; Clark, James H.; Benson, James A.; Hutter, Donald J.; Zavala, Robert T.

    2015-09-01

    We describe multi-baseline observations of a geostationary satellite using the Navy Precision Optical Interferometer (NPOI) during the glint season of March 2015. We succeeded in detecting DirecTV-7S with an interferometer baseline length of 8.8 m on two nights, with a brief simultaneous detection at 9.8 m baseline length on the second night. These baseline lengths correspond to a resolution of ~4 m at geostationary altitude. This is the first multiple-baseline interferometric detection of a satellite.

  4. High-precision optical measurement of the 2S hyperfine interval in atomic hydrogen.

    PubMed

    Kolachevsky, N; Fischer, M; Karshenboim, S G; Hänsch, T W

    2004-01-23

    We have applied an optical method to the measurement of the 2S hyperfine interval in atomic hydrogen. The interval has been measured by means of two-photon spectroscopy of the 1S-2S transition on a hydrogen atomic beam shielded from external magnetic fields. The measured value of the 2S hyperfine interval is equal to 177 556 860(16) Hz and represents the most precise measurement of this interval to date. The theoretical evaluation of the specific combination of 1S and 2S hyperfine intervals D21 is in fair agreement (within 1.4 sigma) with the value for D21 deduced from our measurement.

  5. Comparison of Materials for Use in the Precision Grinding of Optical Components

    SciTech Connect

    Evans, Boyd M. III; Miller, Arthur C. Jr.; Egert, Charles M.

    1997-12-31

    Precision grinding of optical components is becoming an accepted practice for rapidly and deterministically fabrication optical surfaces to final or near-final surface finish and figure. In this paper, a comparison of grinding techniques and materials is performed. Flat and spherical surfaces were ground in three different substrate materials: BK7 glass, chemical vapor deposited (CVD) silicon carbide ceramic, and sapphire. Spherical surfaces were used to determine the contouring capacity of the process, and flat surfaces were used for surface finish measurements. The recently developed Precitech Optimum 2800 diamond turning and grinding platform was used to grind surfaces in 40mm diameter substrates sapphire and silicon carbide substrates and 200 mm BK7 glass substrates using diamond grinding wheels. The results of this study compare the surface finish and figure for the three materials.

  6. A new approach on restoration of dynamic measurement uncertainties in optical precision coordinate metrology

    NASA Astrophysics Data System (ADS)

    Holder, S.; Reetz, E.; Linß, G.

    2015-02-01

    This paper presents a new approach to the restoration of dynamic influenced measurement uncertainties in optical precision coordinate metrology (OPCM) using image sensors to measure geometrical features. Dynamic measurements within the context of this paper are based upon relative motion between the imaging setup (CCD-camera and optical system) and the measuring object respectively the measuring scene. The dynamic image acquisition causes image motion blur effects, which downgrades the uncertainties of the measurand. The approach presented deals with a new technique to restore motion degraded images using different methods to analyze important image features by extending the famous state of the art Richardson-Lucy image restoration technique using a new convergence criteria based on the variation of the detectable sub-pixel edge position of each iteration.

  7. A multi-approach to the optical depth of a contrail cirrus cluster

    NASA Astrophysics Data System (ADS)

    Vazquez-Navarro, Margarita; Bugliaro, Luca; Schumann, Ulrich; Strandgren, Johan; Wirth, Martin; Voigt, Christiane

    2017-04-01

    Amongst the individual aviation emissions, contrail cirrus contribute the largest fraction to the aviation effects on climate. To investigate the optical depth from contrail cirrus, we selected a cirrus and contrail cloud outbreak on the 10th April 2014 between the North Sea and Switzerland detected during the ML-CIRRUS experiment (Voigt et al., 2017). The outbreak was not forecast by weather prediction models. We describe its origin and evolution using a combination of in-situ measurements, remote sensing approaches and contrail prediction model prognosis. The in-situ and lidar measurements were carried out with the HALO aircraft, where the cirrus was first identified. Model predictions from the contrail prediction model CoCiP (Schumann et al., 2012) point to an anthropogenic origin. The satellite pictures from the SEVIRI imager on MSG combined with the use of a contrail cluster tracking algorithm enable the automatic assessment of the origin, displacement and growth of the cloud and the correct labeling of cluster pixels. The evolution of the optical depth and particle size of the selected cluster pixels were derived using the CiPS algorithm, a neural network primarily based on SEVIRI images. The CoCiP forecast of the cluster compared to the actual cluster tracking show that the model correctly predicts the occurrence of the cluster and its advection direction although the cluster spreads faster than simulated. The optical depth derived from CiPS and from the airborne high spectral resolution lidar WALES are compared and show a remarkably good agreement. This confirms that the new CiPS algorithm is a very powerful tool for the assessment of the optical depth of even optically thinner cirrus clouds. References: Schumann, U.: A contrail cirrus prediction model, Geosci. Model Dev., 5, 543-580, doi: 10.5194/gmd-5-543-2012, 2012. Voigt, C., Schumann, U., Minikin, A., Abdelmonem, A., Afchine, A., Borrmann, S., Boettcher, M., Buchholz, B., Bugliaro, L., Costa, A

  8. Heritability of ocular component dimensions in mice phenotyped using depth-enhanced swept source optical coherence tomography.

    PubMed

    Wang, Ling; Považay, Boris; Chen, Yen Po; Hofer, Bernd; Drexler, Wolfgang; Guggenheim, Jeremy A

    2011-10-01

    The range of genetic and genomic resources available makes the mouse a powerful model for the genetic dissection of complex traits. Because accurate, high-throughput phenotypic characterisation is crucial to the success of such endeavours, we recently developed an optical coherence tomography (OCT) system with extended depth range scanning capability for measuring ocular component dimensions in mice. In order to test whether the accuracy and reproducibility of our OCT system was sufficient for gene mapping studies, we carried out an experiment designed to estimate the heritability of mouse ocular component dimensions. High-resolution, two dimensional tomograms were obtained for both eyes of 11 pairs of 8 week-old outbred MF1 mice. Subsequently, images were obtained when their offspring were aged 8 weeks. Biometric data were extracted after image segmentation, reconstruction of the geometric shape of each surface, and calculation of intraocular distances. The repeatability of measurements was evaluated for 12 mice scanned on consecutive days. Heritability estimates were calculated using variance components analysis. Sets of tomograms took ∼2 s to acquire. Biometric data could be obtained for 98% of the 130 eyes scanned. The 95% limits of repeatability ranged from ±6 to ±16 μm for the axial ocular component dimensions. The heritability of the axial ocular components was 0.6-0.8, except for corneal thickness, which had a heritability not significantly different from zero. In conclusion, axial ocular component dimensions are highly heritable in mice, as they are in humans. OCT with extended depth range scanning can be used to rapidly phenotype individual mice with sufficient accuracy and precision to permit gene mapping studies.

  9. Ship-based aerosol optical depth measurements in the Atlantic Ocean: Comparison with satellite retrievals and GOCART model

    NASA Astrophysics Data System (ADS)

    Smirnov, A.; Holben, B. N.; Sakerin, S. M.; Kabanov, D. M.; Slutsker, I.; Chin, M.; Diehl, T. L.; Remer, L. A.; Kahn, R.; Ignatov, A.; Liu, L.; Mishchenko, M.; Eck, T. F.; Kucsera, T. L.; Giles, D.; Kopelevich, O. V.

    2006-07-01

    Aerosol optical depth measurements were made in October-December 2004 onboard the R/V Akademik Sergey Vavilov. The cruise area included an Atlantic transect from North Sea to Cape Town and then a crossing in the South Atlantic to Argentina. In the open oceanic areas not influenced by continental sources aerosol optical depth values were close to background oceanic conditions (τa ~ 0.06-0.08). Spectral dependence, especially in the high latitude Southern Atlantic, can be considered as quasi-neutral (Angstrom parameter α was less than 0.4). Back-trajectory analysis allowed statistical division of the aerosol optical parameters and showed similar properties for the North Atlantic polar marine, South Atlantic subtropical marine and South Atlantic polar marine air. Ship-borne aerosol optical depth comparisons to GOCART model and satellite retrievals revealed systematic biases. Satellite retrieved optical depths are generally higher by 0.02-0.07 (depending on the sensor), especially in low τa conditions. GOCART model simulated optical depths correlate well with the ship measurements and, despite overall bias and a notable disparity with the observations in a number of cases, about 30% agree within +/-0.01.

  10. Statistical variability comparison in MODIS and AERONET derived aerosol optical depth over Indo-Gangetic Plains using time series modeling.

    PubMed

    Soni, Kirti; Parmar, Kulwinder Singh; Kapoor, Sangeeta; Kumar, Nishant

    2016-05-15

    A lot of studies in the literature of Aerosol Optical Depth (AOD) done by using Moderate Resolution Imaging Spectroradiometer (MODIS) derived data, but the accuracy of satellite data in comparison to ground data derived from ARrosol Robotic NETwork (AERONET) has been always questionable. So to overcome from this situation, comparative study of a comprehensive ground based and satellite data for the period of 2001-2012 is modeled. The time series model is used for the accurate prediction of AOD and statistical variability is compared to assess the performance of the model in both cases. Root mean square error (RMSE), mean absolute percentage error (MAPE), stationary R-squared, R-squared, maximum absolute percentage error (MAPE), normalized Bayesian information criterion (NBIC) and Ljung-Box methods are used to check the applicability and validity of the developed ARIMA models revealing significant precision in the model performance. It was found that, it is possible to predict the AOD by statistical modeling using time series obtained from past data of MODIS and AERONET as input data. Moreover, the result shows that MODIS data can be formed from AERONET data by adding 0.251627 ± 0.133589 and vice-versa by subtracting. From the forecast available for AODs for the next four years (2013-2017) by using the developed ARIMA model, it is concluded that the forecasted ground AOD has increased trend. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Precision-Deployable, Stable, Optical Benches for Cost-Effective Space Telescopes

    NASA Astrophysics Data System (ADS)

    Danner, Rolf; Pellegrino, S.; Dailey, D.; Marks, G.; Bookbinder, J.

    2012-05-01

    To explore the universe at the arcsecond resolution of Chandra, while increasing collecting area by at least an order of magnitude and maintaining affordability, we will need to make creative use of existing and new technology. Precision-deployable, stable, optical benches that fit inside smaller, lower-cost launch vehicles are a prime example of a technology well within current reach that will yield breakthrough benefits for future astrophysics missions. Deployable optical benches for astrophysical applications have a reputation for complexity; however, we are offering an approach, based on techniques used in space for decades, that reduces overall mission cost. Currently, deployable structures are implemented on JAXA’s Astro-H and NASA’s NuStar high-energy astrophysics missions. We believe it is now time to evolve these structures into precision, stable optical benches that are stiff, lightweight, and suitable for space telescopes with focal lengths of 20 meters or more. Such optical benches are required for advanced observatory class missions and can be scaled to Explorer and medium-class missions. To this end, we have formed a partnership between Space Structures Laboratory (SSL) at the California Institute of Technology, Northrop Grumman Aerospace Systems (NGAS), Northrop Grumman Astro Aerospace (Astro), and Smithsonian Astrophysical Observatory (SAO). Combining the expertise and tools from academia and industry is the most effective approach to take this concept to Technology Readiness Level (TRL) 6. We plan to perform small sub-scale demonstrations, functional tests, and analytical modeling in the academic environment. Using results from SSL, larger prototypes will be developed at facilities at NGAS in Redondo Beach and Carpinteria, CA.

  12. Global and Seasonal Aerosol Optical Depths Derived From Ultraviolet Observations by Satellites (TOMS)

    NASA Technical Reports Server (NTRS)

    Herman, J. R.; Torres, O.

    1999-01-01

    It has been shown that absorbing aerosols (dust, smoke, volcanic ash) can be detected in the ultraviolet wavelengths (331 nm to 380 nm) from satellite observations (TOMS, Total Ozone Mapping Spectrometer) over both land and water. The theoretical basis for these observations and their conversions to optical depths is discussed in terms of an aerosol index AI or N-value residue (assigned positive for absorbing aerosols). The theoretical considerations show that negative values of the AI frequently represent the presence of non-absorbing aerosols (NA) in the troposphere (mostly pollution in the form of sulfates, hydrocarbons, etc., and some natural sulfate aerosols) with particle sizes near 0.1 to 0.2 microns or less. The detection of small-particle non-absorbing aerosols from the measured backscattered radiances is based on the observed wavelength dependence from Mie scattering after the background Rayleigh scattering is subtracted. The Mie scattering from larger particles, 1 micron or more (e.g., cloud water droplets) has too small a wavelength dependence to be detected by this method. In regions that are mostly cloud free, aerosols of all sizes can be seen in the single channel 380 nm or 360 nm radiance data. The most prominent Al feature observed is the strong asymmetry in aerosol amount between the Northern and Southern Hemispheres, with the large majority of NA occurring above 20degN latitude. The maximum values of non-absorbing aerosols are observed over the eastern U.S. and most of western Europe corresponding to the areas of highest industrial pollution. Annual cycles in the amount of NA are observed over Europe and North America with maxima occurring in the summer corresponding to times of minimum wind transport. Similarly, the maxima in the winter over the Atlantic Ocean occurs because of wind borne transport from the land. Most regions of the world have the maximum amount of non-absorbing aerosol in the December to January period except for the eastern

  13. Aerosol optical depth over complex topography: comparison of AVHRR, MERIS and MODIS aerosol products

    NASA Astrophysics Data System (ADS)

    Riffler, Michael; Popp, Christoph; Hauser, Adrian; Wunderle, Stefan

    Aerosols are a key component in the Earth's atmosphere, influencing the radiation budget due to scattering and absorption of solar and terrestrial radiation and changing cloud physics by serving as cloud condensation nuclei. Furthermore, dispersed particles alter visibility and affect human health. Remote sensing techniques are a common means to monitor aerosol variability on large spatial scales. The accuracy of these retrievals is highest over surfaces with well known spectral properties and low reflectance (e.g. oceans). The retrieval over brighter and heterogeneous land surfaces is more demanding, since temporally unstable surface reflectance and a reduced aerosol signal may result in larger errors. Regions with highly complex topography, like the Alps, can exhibit even larger errors, basically due to directional effects caused by the topography, temporal snow coverage, and usually higher cloud amount. Ground validation of remote sensing aerosol products is generally performed using sun photometer measurements from the AErosol RObotic NETwork (AERONET). However, the lack of such sites in the central parts of the Alps renders validation difficult. To study the potential of aerosol remote sensing in regions with complex topography, namely in the Alps, we make use of an unusual situation on one of the major trans-alpine traffic routes in June 2006: A fatal rock fall caused the nearly one month closure of the Gotthard route in the Central Swiss Reuss Valley. Large parts of the traffic were redirected to the San Bernardino route (eastern Switzerland), which had a large impact on the local traffic amount, and thereby on air quality. Herein we compare the performance of three different sensors (AVHRR, MERIS, MODIS) in detecting this obvious change in the aerosol optical depth of the two alpine valleys in summer 2006. First results from AVHRR show a clear reduction (47%) of the aerosol optical depth along the Gotthard route compared to the five year monthly mean (2003

  14. Precision Interferometric Measurements of Mirror Birefringence in High-Finesse Optical Resonators

    PubMed Central

    Fleisher, Adam J.; Long, David A.; Liu, Qingnan; Hodges, Joseph T.

    2016-01-01

    High-finesse optical resonators found in ultrasensitive laser spectrometers utilize supermirrors ideally consisting of isotropic high-reflectivity coatings. Strictly speaking, however, the optical coatings are often non-uniformly stressed during the deposition process and therefore do possess some small amount of birefringence. When physically mounted the cavity mirrors can be additionally stressed in such a way that large optical birefringence is induced. Here we report a direct measurement of optical birefringence in a two-mirror Fabry-Pérot cavity with R = 99.99 % by observing TEM00 mode beating during cavity decays. Experiments were performed at a wavelength of 4.53 μm, with precision limited by both quantum and technical noise sources. We report a splitting of δν = 618(1) Hz, significantly less than the intrinsic cavity linewidth of δcav ≈ 3 kHz. With a cavity free spectral range of 96.9 MHz, the equivalent fractional change in mirror refractive index due to birefringence is therefore Δn/n = 6.38(1) × 10−6. PMID:27088133

  15. Precision interferometric measurements of mirror birefringence in high-finesse optical resonators

    NASA Astrophysics Data System (ADS)

    Fleisher, Adam J.; Long, David A.; Liu, Qingnan; Hodges, Joseph T.

    2016-01-01

    High-finesse optical resonators found in ultrasensitive laser spectrometers utilize supermirrors ideally consisting of isotropic high-reflectivity coatings. Strictly speaking, however, the optical coatings are often nonuniformly stressed during the deposition process and therefore do possess some small amount of birefringence. When physically mounted the cavity mirrors can be additionally stressed in such a way that large optical birefringence is induced. Here we report a direct measurement of optical birefringence in a two-mirror Fabry-Pérot cavity with R =99.99 % by observing TEM00 mode beating during cavity decays. Experiments were performed at a wavelength of 4.53 μ m , with precision limited by both quantum and technical noise sources. We report a splitting of δν=618 (1 ) Hz, significantly less than the intrinsic cavity line width of δcav≈3 kHz. With a cavity free spectral range of 96.9 MHz, the equivalent fractional change in mirror refractive index due to birefringence is therefore Δ n /n =6.38 (1 ) ×10-6 .

  16. Comparison of Precision between Optical and Electromagnetic Navigation Systems in Total Knee Arthroplasty

    PubMed Central

    Rhee, Seung Joon; Park, Shi Hwan; Cho, He Myung

    2014-01-01

    Purpose The purpose of this study is to compare and analyze the precision of optical and electromagnetic navigation systems in total knee arthroplasty (TKA). Materials and Methods We retrospectively reviewed 60 patients who underwent TKA using an optical navigation system and 60 patients who underwent TKA using an electromagnetic navigation system from June 2010 to March 2012. The mechanical axis that was measured on preoperative radiographs and by the intraoperative navigation systems were compared between the groups. The postoperative positions of the femoral and tibial components in the sagittal and coronal plane were assessed. Results The difference of the mechanical axis measured on the preoperative radiograph and by the intraoperative navigation systems was 0.6 degrees more varus in the electromagnetic navigation system group than in the optical navigation system group, but showed no statistically significant difference between the two groups (p>0.05). The positions of the femoral and tibial components in the sagittal and coronal planes on the postoperative radiographs also showed no statistically significant difference between the two groups (p>0.05). Conclusions In TKA, both optical and electromagnetic navigation systems showed high accuracy and reproducibility, and the measurements from the postoperative radiographs showed no significant difference between the two groups. PMID:25505703

  17. Multifocus microscopy with precise color multi-phase diffractive optics applied in functional neuronal imaging

    PubMed Central

    Abrahamsson, Sara; Ilic, Rob; Wisniewski, Jan; Mehl, Brian; Yu, Liya; Chen, Lei; Davanco, Marcelo; Oudjedi, Laura; Fiche, Jean-Bernard; Hajj, Bassam; Jin, Xin; Pulupa, Joan; Cho, Christine; Mir, Mustafa; El Beheiry, Mohamed; Darzacq, Xavier; Nollmann, Marcelo; Dahan, Maxime; Wu, Carl; Lionnet, Timothée; Liddle, J. Alexander; Bargmann, Cornelia I.

    2016-01-01

    Multifocus microscopy (MFM) allows high-resolution instantaneous three-dimensional (3D) imaging and has been applied to study biological specimens ranging from single molecules inside cells nuclei to entire embryos. We here describe pattern designs and nanofabrication methods for diffractive optics that optimize the light-efficiency of the central optical component of MFM: the diffractive multifocus grating (MFG). We also implement a “precise color” MFM layout with MFGs tailored to individual fluorophores in separate optical arms. The reported advancements enable faster and brighter volumetric time-lapse imaging of biological samples. In live microscopy applications, photon budget is a critical parameter and light-efficiency must be optimized to obtain the fastest possible frame rate while minimizing photodamage. We provide comprehensive descriptions and code for designing diffractive optical devices, and a detailed methods description for nanofabrication of devices. Theoretical efficiencies of reported designs is ≈90% and we have obtained efficiencies of > 80% in MFGs of our own manufacture. We demonstrate the performance of a multi-phase MFG in 3D functional neuronal imaging in living C. elegans. PMID:27231594

  18. Development of dual-layer GSO depth-of-interaction block detector using angled optical fiber

    NASA Astrophysics Data System (ADS)

    Okumura, Satoshi; Yamamoto, Seiichi; Watabe, Hiroshi; Kato, Natsuki; Hamamura, Huka

    2015-05-01

    A PET system for small animals requires a small detector ring to obtain high-spatial resolution images. However, when we use a relatively large size of photodetector such as a position-sensitive photomultiplier tube (PSPMT), the detector ring is arranged in a hexagonal- or octagonal-shape, and the PET system has large gaps between the block detectors. The large gaps produce image distortion, and the reconstruction algorithm is difficult. To solve these problems, we proposed to arrange two scintillator blocks on one PSPMT using two angled optical fiber-based image guides. We could set two scintillator blocks angled at 22.5° on a PSPMT so that these scintillator blocks are arranged in a nearly circular (hexadecagonal) shape with eight developed block detectors. We used Gd2SiO5 (GSO) scintillators with Ce concentrations of 1.5 mol% (decay time: 39 ns) and 0.4 mol% (decay time: 63 ns). Sizes of these GSO cells were 1.6×2.4×7.0 mm3 and 1.6×2.4×8.0 mm3 for 1.5 mol% Ce and 0.4 mol% Ce, respectively. These two types of GSO were arranged in an 11×15 matrix and optically coupled in the depth direction to form a depth-of-interaction (DOI) detector. Two GSO blocks and two optical fiber-based image guides were optically coupled to a 2-in. PSPMT (Hamamatsu Photonics H8500: 8×8 anodes). We measured the performances of the block detector with Cs-137 gamma photons (662-keV). We could resolve almost all pixels clearly in a two-dimensional position histogram. The average peak-to-valley ratios (P/Vs) of the two-dimensional position histogram along profiles were 2.6 and 4.8 in horizontal and vertical directions, respectively. The energy resolution was 28.4% full-width at half-maximum (FWHM). The pulse shape spectra showed good separation with a P/V of 5.2. The developed block detector performed well and shows promise for the development of high-sensitivity and high-spatial resolution PET systems.

  19. Initial simulation study on high-precision radio measurements of the depth of shower maximum with SKAI-low

    NASA Astrophysics Data System (ADS)

    Zilles, Anne; Buitink, Stijn; Huege, Tim

    2017-03-01

    As LOFAR has shown, using a dense array of radio antennas for detecting extensive air showers initiated by cosmic rays in the Earth's atmosphere makes it possible to measure the depth of shower maximum for individual showers with a statistical uncertainty less than 20g/cm2. This allows detailed studies of the mass composition in the energy region around 1017 eV where the transition from a Galactic to an Extragalactic origin could occur. Since SKA1-low will provide a much denser and very homogeneous antenna array with a large bandwidth of 50 - 350 MHz it is expected to reach an uncertainty on the Xmax reconstruction of less than 10g/cm2. We present first results of a simulation study with focus on the potential to reconstruct the depth of shower maximum for individual showers to be measured with SKA1-low. In addition, possible influences of various parameters such as the numbers of antennas included in the analysis or the considered frequency bandwidth will be discussed.

  20. Assessment of Error in Aerosol Optical Depth Measured by AERONET Due to Aerosol Forward Scattering

    NASA Technical Reports Server (NTRS)

    Sinyuk, Alexander; Holben, Brent N.; Smirnov, Alexander; Eck, Thomas F.; Slustsker, Ilya; Schafer, Joel S.; Giles, David M.; Sorokin, Michail

    2013-01-01

    We present an analysis of the effect of aerosol forward scattering on the accuracy of aerosol optical depth (AOD) measured by CIMEL Sun photometers. The effect is quantified in terms of AOD and solar zenith angle using radiative transfer modeling. The analysis is based on aerosol size distributions derived from multi-year climatologies of AERONET aerosol retrievals. The study shows that the modeled error is lower than AOD calibration uncertainty (0.01) for the vast majority of AERONET level 2 observations, 99.53%. Only 0.47% of the AERONET database corresponding mostly to dust aerosol with high AOD and low solar elevations has larger biases. We also show that observations with extreme reductions in direct solar irradiance do not contribute to level 2 AOD due to low Sun photometer digital counts below a quality control cutoff threshold.

  1. Measurement of depth-resolved thermal deformation distribution using phase-contrast spectral optical coherence tomography.

    PubMed

    Zhang, Yun; Dong, Bo; Bai, Yulei; Ye, Shuangli; Lei, Zhenkun; Zhou, Yanzhou

    2015-10-19

    An updated B-scan method is proposed for measuring the evolution of thermal deformation fields in polymers. In order to measure the distributions of out-of-plane deformation and normal strain field, phase-contrast spectral optical coherence tomography (PC-SOCT) was performed with the depth range and resolution of 4.3 mm and 10.7 μm, respectively, as thermal loads were applied to three different multilayer samples. The relation between temperature and material refractive index was predetermined before the measurement. After accounting for the refractive index, the thermal deformation fields in the polymer were obtained. The measured thermal expansion coefficient of silicone sealant was approximately equal to its reference value. This method allows correctly assessing the mechanical properties in semitransparent polymers.

  2. Assessment of error in aerosol optical depth measured by AERONET due to aerosol forward scattering

    NASA Astrophysics Data System (ADS)

    Sinyuk, Alexander; Holben, Brent N.; Smirnov, Alexander; Eck, Thomas F.; Slutsker, Ilya; Schafer, Joel S.; Giles, David M.; Sorokin, Mikhail

    2012-12-01

    We present an analysis of the effect of aerosol forward scattering on the accuracy of aerosol optical depth (AOD) measured by CIMEL Sun photometers. The effect is quantified in terms of AOD and solar zenith angle using radiative transfer modeling. The analysis is based on aerosol size distributions derived from multi-year climatologies of AERONET aerosol retrievals. The study shows that the modeled error is lower than AOD calibration uncertainty (0.01) for the vast majority of AERONET level 2 observations, ∼99.53%. Only ∼0.47% of the AERONET database corresponding mostly to dust aerosol with high AOD and low solar elevations has larger biases. We also show that observations with extreme reductions in direct solar irradiance do not contribute to level 2 AOD due to low Sun photometer digital counts below a quality control cutoff threshold.

  3. Atmospheric optical depth effects on angular anisotropy of plant canopy reflectance

    NASA Technical Reports Server (NTRS)

    Deering, Donald W.; Eck, Thomas F.

    1987-01-01

    The effects of varying atmospheric aerosol optical depth on the bidirectional reflectance distribution of vegetation canopies is investigated. The reflectance distributions of two pasture grass canopies and one soya bean canopy under different sky irradiance distributions were measured, and the data were analyzed in the visible and IR spectral bands. It is observed that, for the pasture grass canopies, the change in reflectance is due to the percentage of shadowed area viewed by the sensor, and for the soya bean, the specular reflection effect and increased diffuse irradiance penetration into the canopy cause reflectance changes. It is detected that the reflectivity for the soya bean canopy on a hazy day is lower than on a clear day; however, the opposite change is observed for the pasture grass. It is also detected that the normalized difference vegetation index values differ under clear and hazy conditions for the same vegetation canopy conditions.

  4. Hemispheric aerosol vertical profiles: anthropogenic impacts on optical depth and cloud nuclei.

    PubMed

    Clarke, Antony; Kapustin, Vladimir

    2010-09-17

    Understanding the effect of anthropogenic combustion upon aerosol optical depth (AOD), clouds, and their radiative forcing requires regionally representative aerosol profiles. In this work, we examine more than 1000 vertical profiles from 11 major airborne campaigns in the Pacific hemisphere and confirm that regional enhancements in aerosol light scattering, mass, and number are associated with carbon monoxide from combustion and can exceed values in unperturbed regions by more than one order of magnitude. Related regional increases in a proxy for cloud condensation nuclei (CCN) and AOD imply that direct and indirect aerosol radiative effects are coupled issues linked globally to aged combustion. These profiles constrain the influence of combustion on regional AOD and CCN suitable for challenging climate model performance and informing satellite retrievals.

  5. Spatial and temporal variations in the atmospheric aerosol optical depth at the ARM CART Site

    SciTech Connect

    Nash, T.M.; Cheng, M.D.

    1998-02-01

    In an effort to better characterize the inputs to radiative transfer models and research-grade global climate simulation models (GCMs) the columnar aerosol loading, measured as the aerosol optical depth (AOD), has been computed for five facilities within the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) Site. Characterization of the AOD reported here show clear evidence that the spatial and temporal gradient exists at a much finer linear scale than those of the CART site. The annual variations of median AOD are on the order of 0.30 at all five facilities. The Spearman correlation and varimax-rotated PCA indicated the AOD values vary consistently across the CART site. The Northwest corner facility (EF-1) was the single facility that behaved differently from the rest. This sub-GCM grid variation can not be ignored if the model is to be used to accurately predict future climate change.

  6. Accounting for High-biases in the MODIS Aerosol Optical Depth Retrieval

    NASA Astrophysics Data System (ADS)

    Levy, R. C.; Patadia, F.; Mattoo, S.; Platnick, S. E.

    2015-12-01

    Aerosol optical depth retrieved from observations made by the MODIS instrument, onboard Terra and Aqua satellites, has been extensively validated against ground based AERONET AOD. Global validation of the current Collection 6 (C6) AOD over ocean indicates that 68% of retrieved AOD agrees to within 0.03 ± 10% * AERONET AOD. However there does exist high bias in MODIS AOD retrievals. There are a number of reasons for over-estimation. One is cloud contamination, which is where undetected clouds are retrieved as aerosol. A second is 3D radiative effects, where observed radiance is enhanced due to scattering from clouds. Here we parse out and attempt to quantify the contributions from the cloud contamination in AOD retrieval over ocean. Among other reasons for high bias are wrong aerosol models, improper surface characterization, error in local windspeed data and adjacency effects.

  7. Spatial and temporal variations in the atmospheric aerosol optical depth at the ARM CART Site

    SciTech Connect

    Nash, T.M.; Cheng, M.D.

    1998-12-31

    In an effort to better characterize the inputs to radiative transfer models and research-grade global climate simulation models (GCMs) the columnar aerosol loading, measured as the aerosol optical depth (AOD), has been computed for five facilities within the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) Site. Characterization of the AOD reported here show clear evidence that the spatial and temporal gradient exists at a much finer linear scale than those of the CART site. The annual variations of median AOD are on the order of 0.30 at all five facilities. The Spearman correlation and varimax-rotated PCA indicated the AOD values vary consistently across the CART site. The Northwest corner facility (EF-1) was the single facility that behaved differently from the rest. This sub-GCM grid variation can not be ignored if the model it to be used to accurately predict future climate change.

  8. Determination of Aerosol Optical Depth and Land Surface Directional Reflectances Using Multiangle Imagery

    NASA Technical Reports Server (NTRS)

    Martonchik, John V.

    1997-01-01

    Spectral aerosol optical depths, surface hemispherical-directional reflectance factors, and bihemispherical reflectances (albedos) are retrieved for an area of Glacier National Park using spectral, multiangle imagery obtained with the airborne advanced solid state array spectroradiometer (ASAS). The retrieval algorithms are described and are identical in principle to those being devised for use by the multiangle imaging spectroradiometer (MISR) which will fly on the EOS-AMI spacecraft in 1998. As part of its science mission, MISR will produce global coverage of both aerosol amounts an an surface reflection properties. The results in this paper represent the initial effort in applying the MISR algorithms to real data. These algorithms will undergo additional testing and validation as more multiangle data become available.

  9. SAGE and SAM II measurements of global stratospheric aerosol optical depth and mass loading

    NASA Technical Reports Server (NTRS)

    Kent, G. S.; Mccormick, M. P.

    1984-01-01

    Several volcanic eruptions between November 1979 and April 1981 have injected material into the stratosphere. The SAGE and SAM II satellite systems have measured, with global coverage, the 1-micron extinction produced by this material, and examples of the data product are shown in the form of global maps of stratospheric optical depth and altitude-latitude plots of zonal mean extinction. These data, and that for the volcanically quiet period in early 1979, have been used to determine the changes in the total stratospheric mass loading. Estimates have also been made of the contribution to the total aerosol mass from each eruption. It has been found that between 1979 and mid-1981, the total stratospheric aerosol mass increased from a background level of approximately 570,000 metric tons to a peak of approximately 1,300,000 metric tons.

  10. High resolution coherence domain depth-resolved nailfold capillaroscopy based on correlation mapping optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Subhash, Hrebesh M.; O'Gorman, Sean; Neuhaus, Kai; Leahy, Martin

    2014-03-01

    In this paper we demonstrate a novel application of correlation mapping optical coherence tomography (cm-OCT) for volumetric nailfold capillaroscopy (NFC). NFC is a widely used non-invasive diagnostic method to analyze capillary morphology and microvascular abnormalities of nailfold area for a range of disease conditions. However, the conventional NFC is incapable of providing volumetric imaging, when volumetric quantitative microangiopathic parameters such as plexus morphology, capillary density, and morphologic anomalies of the end row loops most critical. cm-OCT is a recently developed well established coherence domain magnitude based angiographic modality, which takes advantage of the time-varying speckle effect, which is normally dominant in the vicinity of vascular regions compared to static tissue region. It utilizes the correlation coefficient as a direct measurement of decorrelation between two adjacent B-frames to enhance the visibility of depth-resolved microcirculation.

  11. Martian Surface NIR Spectral Modeling for Ice Cloud Optical Depth Retrievals using CRISM Mapping Data

    NASA Astrophysics Data System (ADS)

    Klassen, D. R.

    2011-10-01

    One goal in the study of Mars is to understand its water cycle and the total water budget. As part of this, I am working on trying to measure water ice content in Martian clouds. The catch is that in order to measure the water abundance in clouds using near-infrared (NIR) spectra, one must know the surface spectrum, since it is an input for radiative transfer modeling—but to get the surface spectrum, one must be able to remove the effects of the atmosphere and aerosols. I will present four primary methods of modeling away the surface in order to retrieve the ice cloud (and dust) optical depth and compare and contrast them for both ease-of-use and apparent accuracy.

  12. Optical gesture sensing and depth mapping technologies for head-mounted displays: an overview

    NASA Astrophysics Data System (ADS)

    Kress, Bernard; Lee, Johnny

    2013-05-01

    Head Mounted Displays (HMDs), and especially see-through HMDs have gained renewed interest in recent time, and for the first time outside the traditional military and defense realm, due to several high profile consumer electronics companies presenting their products to hit market. Consumer electronics HMDs have quite different requirements and constrains as their military counterparts. Voice comments are the de-facto interface for such devices, but when the voice recognition does not work (not connection to the cloud for example), trackpad and gesture sensing technologies have to be used to communicate information to the device. We review in this paper the various technologies developed today integrating optical gesture sensing in a small footprint, as well as the various related 3d depth mapping sensors.

  13. Precision Surface-Coupled Optical-Trapping Assay with One-Basepair Resolution

    PubMed Central

    Carter, Ashley R.; Seol, Yeonee; Perkins, Thomas T.

    2009-01-01

    The most commonly used optical-trapping assays are coupled to surfaces, yet such assays lack atomic-scale (∼0.1 nm) spatial resolution due to drift between the surface and trap. We used active stabilization techniques to minimize surface motion to 0.1 nm in three dimensions and decrease multiple types of trap laser noise (pointing, intensity, mode, and polarization). As a result, we achieved nearly the thermal limit (<0.05 nm) of bead detection over a broad range of trap stiffness (kT = 0.05–0.5 pN/nm) and frequency (Δf = 0.03–100 Hz). We next demonstrated sensitivity to one-basepair (0.34-nm) steps along DNA in a surface-coupled assay at moderate force (6 pN). Moreover, basepair stability was achieved immediately after substantial (3.4 pN) changes in force. Active intensity stabilization also led to enhanced force precision (∼0.01%) that resolved 0.1-pN force-induced changes in DNA hairpin unfolding dynamics. This work brings the benefit of atomic-scale resolution, currently limited to dual-beam trapping assays, along with enhanced force precision to the widely used, surface-coupled optical-trapping assay. PMID:19348774

  14. A precise optical transmission spectrum of the inflated exoplanet WASP-52b

    NASA Astrophysics Data System (ADS)

    Louden, Tom; Wheatley, Peter J.; Irwin, Patrick G. J.; Kirk, James; Skillen, Ian

    2017-09-01

    We have measured a precise optical transmission spectrum for WASP-52b, a highly inflated hot Jupiter with an equilibrium temperature of 1300 K. Two transits of the planet were observed spectroscopically at low resolution with the auxiliary-port camera on the William Herschel Telescope, covering a wide range of 4000-8750 Å. We use a Gaussian process approach to model the correlated noise in the multiwavelength light curves, resulting in a high precision relative transmission spectrum with errors of the order of a pressure scaleheight. We attempted to fit a variety of different representative model atmospheres to the transmission spectrum, but did not find a satisfactory match to the entire spectral range. For the majority of the covered wavelength range (4000-7750 Å), the spectrum is flat, and can be explained by an optically thick and grey cloud layer at 0.1 mbar, but this is inconsistent with a slightly d