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Sample records for micron coherent doppler

  1. Compact, Engineered 2-Micron Coherent Doppler Wind Lidar Prototype for Field and Airborne Evaluation

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Amzajerdian, Farzin; Koch, Grady J.

    2006-01-01

    The state-of-the-art 2-micron coherent Doppler wind lidar breadboard at NASA/LaRC will be engineered and compactly packaged consistent with future aircraft flights. The packaged transceiver will be integrated into a coherent Doppler wind lidar system test bed at LaRC. Atmospheric wind measurements will be made to validate the packaged technology. This will greatly advance the coherent part of the hybrid Doppler wind lidar solution to the need for global tropospheric wind measurements.

  2. Wind Measurements with High Energy 2 Micron Coherent Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Barnes, Bruce W.; Koch, Grady J.; Petros, Mulugeta; Beyon, Jeffrey Y.; Amzajerdian, Farzin; Yu, Ji-Rong; Kavaya, Michael J.; Singh, Upendra N.

    2004-01-01

    A coherent Doppler lidar based on an injection seeded Ho:Tm:YLF pulsed laser was developed for wind measurements. A transmitted pulse energy over 75 mJ at 5 Hz repetition rate has been demonstrated. Designs are presented on the laser, injection seeding, receiver, and signal processing subsystems. Sample data of atmospheric measurements are presented including a wind profile extending from the atmospheric boundary layer (ABL) to the free troposphere.

  3. 2-Micron Coherent Doppler Lidar Instrument Advancements for Tropospheric Wind Measurement

    NASA Technical Reports Server (NTRS)

    Petros, Mulugeta; Singh, U. N.; Yu, J.; Kavaya, M. J.; Koch, G.

    2014-01-01

    Knowledge derived from global tropospheric wind measurement is an important constituent of our overall understanding of climate behavior [1]. Accurate weather prediction saves lives and protects properties from destructions. High-energy 2-micron laser is the transmitter of choice for coherent Doppler wind detection. In addition to the eye-safety, the wavelength of the transmitter suitably matches the aerosol size in the lower troposphere. Although the technology of the 2-micron laser has been maturing steadily, lidar derived wind data is still a void in the global weather database. In the last decade, researchers at NASA Langley Research Center (LaRC) have been engaged in this endeavor, contributing to the scientific database of 2-micron lidar transmitters. As part of this effort, an in depth analysis of the physics involved in the workings of the Ho: Tm laser systems have been published. In the last few years, we have demonstrated lidar transmitter with over1Joule output energy. In addition, a large body of work has been done in characterizing new laser materials and unique crystal configurations to enhance the efficiency and output energy of the 2-micron laser systems. At present 2-micron lidar systems are measuring wind from both ground and airborne platforms. This paper will provide an overview of the advancements made in recent years and the technology maturity levels attained.

  4. Compact, Engineered, 2-Micron Coherent Doppler Wind Lidar Prototype: A New NASA Instrument Incubator Program Project

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Koch, Grady J.; Yu, Jirong; Singh, Upendra N.; Amzajerdian, Farzin; Wang, Jinxue; Petros, Mulugeta

    2005-01-01

    A new project, selected in 2005 by NASA s Science Mission Directorate (SMD) under the Instrument Incubator Program (IIP), will be described. The 3-year effort is intended to design, fabricate, and demonstrate a packaged, rugged, compact, space-qualifiable coherent Doppler wind lidar (DWL) transceiver capable of future validation in an aircraft and/or Unmanned Aerial Vehicle (UAV). The packaged DWL will utilize the numerous advances in pulsed, solid-state, 2-micron laser technology at NASA s Langley Research Center (LaRC) in such areas as crystal composition, architecture, efficiency, cooling techniques, pulse energy, and beam quality. The extensive experience of Raytheon Space and Airborne Systems (RSAS) in coherent lidar systems, in spacebased sensors, and in packaging rugged lidar systems will be applied to this project. The packaged transceiver will be as close to an envisioned space-based DWL system as the resources and technology readiness allow. We will attempt to facilitate a future upgrade to a coherent lidar system capable of simultaneous wind and CO2 concentration profile measurements. Since aerosol and dust concentration is also available from the lidar signal, the potential for a triple measurement lidar system is attractive for both Earth and Mars remote sensing. A key follow on step after the IIP will be to add a telescope, scanner, and software for aircraft validation. This IIP should also put us in a position to begin a parallel formulation study in the 2006-2007 timeframe for a space-based DWL demonstration mission early next decade.

  5. Compact, High Energy 2-micron Coherent Doppler Wind Lidar Development for NASA's Future 3-D Winds Measurement from Space

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Koch, Grady; Yu, Jirong; Petros, Mulugeta; Beyon, Jeffrey; Kavaya, Michael J.; Trieu, Bo; Chen, Songsheng; Bai, Yingxin; Petzar, paul; Modlin, Edward A.; Barnes, Bruce W.; Demoz, Belay B.

    2010-01-01

    This paper presents an overview of 2-micron laser transmitter development at NASA Langley Research Center for coherent-detection lidar profiling of winds. The novel high-energy, 2-micron, Ho:Tm:LuLiF laser technology developed at NASA Langley was employed to study laser technology currently envisioned by NASA for future global coherent Doppler lidar winds measurement. The 250 mJ, 10 Hz laser was designed as an integral part of a compact lidar transceiver developed for future aircraft flight. Ground-based wind profiles made with this transceiver will be presented. NASA Langley is currently funded to build complete Doppler lidar systems using this transceiver for the DC-8 aircraft in autonomous operation. Recently, LaRC 2-micron coherent Doppler wind lidar system was selected to contribute to the NASA Science Mission Directorate (SMD) Earth Science Division (ESD) hurricane field experiment in 2010 titled Genesis and Rapid Intensification Processes (GRIP). The Doppler lidar system will measure vertical profiles of horizontal vector winds from the DC-8 aircraft using NASA Langley s existing 2-micron, pulsed, coherent detection, Doppler wind lidar system that is ready for DC-8 integration. The measurements will typically extend from the DC-8 to the earth s surface. They will be highly accurate in both wind magnitude and direction. Displays of the data will be provided in real time on the DC-8. The pulsed Doppler wind lidar of NASA Langley Research Center is much more powerful than past Doppler lidars. The operating range, accuracy, range resolution, and time resolution will be unprecedented. We expect the data to play a key role, combined with the other sensors, in improving understanding and predictive algorithms for hurricane strength and track. 1

  6. Wind Profiling from a New Compact, Pulsed, 2-Micron, Coherent-Detection Doppler Lidar Transceiver during Wind Measurement Intercomparison

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Koch, Grady J.; Kavaya, Michael J.; Yu, Jirong; Beyon, Jeffrey Y.; Demoz, B.; Veneable, D.

    2009-01-01

    NASA Langley Research Center has a long history of developing 2-micron laser transmitter for wind sensing. With support from NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement. This lidar system was recently deployed at Howard University facility in Beltsville, Maryland, along with other wind lidar systems. Coherent Doppler wind lidar ground-based wind measurements and comparisons with other lidars and other sensors will be presented.

  7. Long-duration Operation of 2-micron Coherent Doppler Lidar in Space

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Baker, Nathaniel R.; Baggot, Rene P.; Kavaya, Michael J.; Singh, Upendra N.

    2005-01-01

    The reliability and lifetime of laser remote sensing systems that can operate autonomously over a sufficiently long period are mainly constrained by the laser diode arrays (LDAs) used for pumping their laser transmitters. The lifetime of a 2-micron coherent lidar operating in space is particularly of concern in lieu of required pump pulse duration of Thulium and Holmium solid state lasers (approx. 1msec) that are considerably longer than those of more widely used 1-micron lasers (< 0.2 msec). A factor of 5 to 10 times longer pulse duration can easily translate to over an order of magnitude shorter lifetime for a typical commercially available high-power 2-D array. Therefore, it is imperative to address the lifetime and reliability of LDAs for pumping 2-micron lasers by exploring all the potential options that significantly prolong their life meeting the required operational lifetime of space-based coherent Doppler lidars. The leading causes of sudden failure and premature degradation of LDAs are intrinsic semiconductor defects, optical facet breakdown resulting from excessive localized heating, and thermo-mechanical stresses due to the extreme thermal cycling of the laser active regions1-2. Long pulse operation grossly amplifies the impact of these failure/degradation causes, particularly the thermo-mechanical stresses due to pulse-to-pulse thermal cycling. Therefore, several experimental setups have been developed to investigate each of the failure mechanisms and causes of premature degradation in order to evaluate various package designs, define the best operating parameters, and to guide the technology advancement, leading to highly reliable and very long lifetime LDAs5. Several areas of improvement in the packaging and fabrication process of laser diodes have already been identified and efforts towards implementing these improvements are well underway. These efforts include the use of advanced high thermal conductivity materials for packaging of laser diode

  8. Airborne Wind Profiling With the Data Acquisition and Processing System for a Pulsed 2-Micron Coherent Doppler Lidar System

    NASA Technical Reports Server (NTRS)

    Beyon, Jeffrey Y.; Koch, Grady J.; Kavaya, Michael J.

    2012-01-01

    A pulsed 2-micron coherent Doppler lidar system at NASA Langley Research Center in Virginia flew on the NASA's DC-8 aircraft during the NASA Genesis and Rapid Intensification Processes (GRIP) during the summer of 2010. The participation was part of the project Doppler Aerosol Wind Lidar (DAWN) Air. Selected results of airborne wind profiling are presented and compared with the dropsonde data for verification purposes. Panoramic presentations of different wind parameters over a nominal observation time span are also presented for selected GRIP data sets. The realtime data acquisition and analysis software that was employed during the GRIP campaign is introduced with its unique features.

  9. Data Acquisition and Processing System for Airborne Wind Profiling with a Pulsed, 2-Micron, Coherent-Detection, Doppler Lidar System

    NASA Technical Reports Server (NTRS)

    Beyon, J. Y.; Koch, G. J.; Kavaya, M. J.

    2010-01-01

    A data acquisition and signal processing system is being developed for a 2-micron airborne wind profiling coherent Doppler lidar system. This lidar, called the Doppler Aerosol Wind Lidar (DAWN), is based on a Ho:Tm:LuLiF laser transmitter and 15-cm diameter telescope. It is being packaged for flights onboard the NASA DC-8, with the first flights in the summer of 2010 in support of the NASA Genesis and Rapid Intensification Processes (GRIP) campaign for the study of hurricanes. The data acquisition and processing system is housed in a compact PCI chassis and consists of four components such as a digitizer, a digital signal processing (DSP) module, a video controller, and a serial port controller. The data acquisition and processing software (DAPS) is also being developed to control the system including real-time data analysis and display. The system detects an external 10 Hz trigger pulse and initiates the data acquisition and processing process, and displays selected wind profile parameters such as Doppler shift, power distribution, wind directions and velocities. Doppler shift created by aircraft motion is measured by an inertial navigation/GPS sensor and fed to the signal processing system for real-time removal of aircraft effects from wind measurements. A general overview of the system and the DAPS as well as the coherent Doppler lidar system is presented in this paper.

  10. Noise Whitening in Airborne Wind Profiling With a Pulsed 2-Micron Coherent Doppler Lidar at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Beyon, Jeffrey Y.; Arthur, Grant E.; Koch, Grady J.; Kavaya, Michael J.

    2012-01-01

    Two different noise whitening methods in airborne wind profiling with a pulsed 2-micron coherent Doppler lidar system at NASA Langley Research Center in Virginia are presented. In order to provide accurate wind parameter estimates from the airborne lidar data acquired during the NASA Genesis and Rapid Intensification Processes (GRIP) campaign in 2010, the adverse effects of background instrument noise must be compensated properly in the early stage of data processing. The results of the two methods are presented using selected GRIP data and compared with the dropsonde data for verification purposes.

  11. Qualification Testing of Laser Diode Pump Arrays for a Space-Based 2-micron Coherent Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Singh, Upendra N.; Kavaya, Michael J.

    2007-01-01

    The 2-micron thulium and holmium-based lasers being considered as the transmitter source for space-based coherent Doppler lidar require high power laser diode pump arrays operating in a long pulse regime of about 1 msec. Operating laser diode arrays over such long pulses drastically impact their useful lifetime due to the excessive localized heating and substantial pulse-to-pulse thermal cycling of their active regions. This paper describes the long pulse performance of laser diode arrays and their critical thermal characteristics. A viable approach is then offered that allows for determining the optimum operational parameters leading to the maximum attainable lifetime.

  12. Development of the Data Acquisition and Processing System for a Pulsed 2-Micron Coherent Doppler Lidar System

    NASA Technical Reports Server (NTRS)

    Beyon, Jeffrey Y.; Koch, Grady J.; Kavaya, Michael J.

    2010-01-01

    A general overview of the development of a data acquisition and processing system is presented for a pulsed, 2-micron coherent Doppler Lidar system located in NASA Langley Research Center in Hampton, Virginia, USA. It is a comprehensive system that performs high-speed data acquisition, analysis, and data display both in real time and offline. The first flight missions are scheduled for the summer of 2010 as part of the NASA Genesis and Rapid Intensification Processes (GRIP) campaign for the study of hurricanes. The system as well as the control software is reviewed and its requirements and unique features are discussed.

  13. Compact, Engineered, 2-Micron Coherent Doppler Wind Lidar Prototype for Field and Airborne Validation: Doppler Aerosol WiNd Lidar (DAWN). Interim Review #1 (6 months)

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Singh, Upendra N.; Koch, Grady J.; Yu, Jirong; Amzajerdian, Farzin; Trieu, Bo C.; Petros, Mulugeta

    2006-01-01

    A new project, selected in 2005 by NASA's Science Mission Directorate (SMD), under the Instrument Incubator Program (IIP), will be described. The 3-year effort is intended to design, fabricate, and demonstrate a packaged, rugged, compact, space-qualifiable coherent Doppler wind lidar (DWL) transceiver capable of future validation in an aircraft and/or Unmanned Aerial Vehicle (UAV). The state-of-the-art 2-micron coherent DWL breadboard at NASA/LaRC will be engineered and compactly packaged consistent with future aircraft flights. The packaged transceiver will be integrated into a coherent DWL system test bed at LaRC. Atmospheric wind measurements will be made to validate the packaged technology. This will greatly advance the coherent part of the hybrid DWL solution to the need for global tropospheric wind measurements.

  14. Airborne Wind Profiling Algorithms for the Pulsed 2-Micron Coherent Doppler Lidar at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Beyon, Jeffrey Y.; Koch, Grady J.; Kavaya, Michael J.; Ray, Taylor J.

    2013-01-01

    Two versions of airborne wind profiling algorithms for the pulsed 2-micron coherent Doppler lidar system at NASA Langley Research Center in Virginia are presented. Each algorithm utilizes different number of line-of-sight (LOS) lidar returns while compensating the adverse effects of different coordinate systems between the aircraft and the Earth. One of the two algorithms APOLO (Airborne Wind Profiling Algorithm for Doppler Wind Lidar) estimates wind products using two LOSs. The other algorithm utilizes five LOSs. The airborne lidar data were acquired during the NASA's Genesis and Rapid Intensification Processes (GRIP) campaign in 2010. The wind profile products from the two algorithms are compared with the dropsonde data to validate their results.

  15. Wind Profiling from a High Energy, Pulsed, 2-Micron, Coherent-Detection Doppler Lidar during Field Campaign

    NASA Astrophysics Data System (ADS)

    Singh, U. N.; Koch, G. J.; Kavaya, M. J.; Yu, J.; Beyon, J. Y.; Demoz, B.

    2009-12-01

    NASA Langley Research Center has a long history of developing 2-micron laser transmitter for wind sensing. With support from NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement. The transmitter portion of the transceiver employs the high-pulse-energy, Ho:Tm:LuLiF, partially conductively cooled laser technology developed at NASA Langley. The transceiver is capable of 250 mJ pulses at 10 Hz. It is very similar to the technology envisioned for coherent Doppler lidar wind measurements from Earth and Mars orbit. The transceiver is coupled to the large optics and data acquisition system in the NASA Langley VALIDAR mobile trailer. The large optics consists of a 15-cm off-axis beam expanding telescope, and a full-hemispheric scanner. Vertical and horizontal vector winds are measured, as well as relative backscatter. The data acquisition system employs frequency domain velocity estimation and pulse accumulation. It permits real-time display of the processed winds and archival of all data. The LaRC mobile lidar was deployed at Howard University facility in Beltsville, Maryland as part of NASA HQ funded (ROSES-2007, Wind Lidar Science Proposal entitled “Intercomparison of Multiple Lidars for Wind Measurements). During the campaign, testing of the lidar was combined with a field campaign to operate a 2-μm coherent lidar alongside a 355-nm direct detection lidar to demonstrate the hybrid wind lidar concept. Besides lidar, many other meteorological sensors were located at the campaign site, including wind measuring balloon sondes, sonic and propeller anemometers mounted on a tower, and a 915-MHz radio acoustic sounding system. Comparisons among these wind measurement sensors are currently being analyzed and should be available for presentation at the Conference.

  16. Wind Measurements from a High Energy, Pulsed, 2-Micron, Coherent-Detection Doppler Lidar and Intercomparison with other sensors deployed during Field Campaign

    NASA Astrophysics Data System (ADS)

    Singh, Upendra; Koch, Grady; Kavaya, Michael; Yu, Jirong; Beyon, Jeffrey; Demoz, Belay

    2010-05-01

    This paper presents an overview of 2-micron laser transmitter development at NASA Langley Research Center (LaRC) for coherent-detection lidar profiling of winds. The novel high-energy, 2-micron, Ho:Tm:LuLiF laser technology developed at NASA Langley was employed to study laser technology currently envisioned by NASA for future global coherent Doppler lidar winds measurement. The 250 mJ, 10 Hz laser was designed as an integral part of a compact lidar transceiver developed for future aircraft flight. Ground-based wind profiles made with this transceiver will be presented. NASA Langley is currently funded to build complete Doppler lidar systems using this transceiver for the DC-8 and WB-57 aircraft. The WB-57 flights will present a more severe environment and will require autonomous operation of the lidar system. The DC-8 lidar system is a likely component of future NASA hurricane research. It will include real-time data processing and display, as well as full data archiving. The LaRC mobile lidar was deployed at Howard University facility in Beltsville, Maryland as part of NASA HQ funded (ROSES-2007, Wind Lidar Science Proposal entitled "Intercomparison of Multiple Lidars for Wind Measurements). During the campaign, testing of the lidar was combined with a field campaign to operate a 2-micron coherent lidar alongside a 355-nm direct detection lidar to demonstrate the hybrid wind lidar concept. Besides lidar, many other meteorological sensors were located at the campaign site, including wind measuring balloon sondes, sonic and propeller anemometers mounted on a tower, and a 915-MHz radio acoustic sounding system. Comparisons among these wind measurement sensors will be presented at the conference.

  17. Development of a Compact, Pulsed, 2-Micron, Coherent-Detection, Doppler Wind Lidar Transceiver; and Plans for Flights on NASA's DC-8 and WB-57 Aircraft

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Singh, Upendra N.; Koch, Grady J.; Yu, Jirong; Trieu, Bo C.; Petros, Mulugeta; Petzar, Paul J.

    2009-01-01

    We present results of a recently completed effort to design, fabricate, and demonstrate a compact lidar transceiver for coherent-detection lidar profiling of winds. The novel high-energy, 2-micron, Ho:Tm:LuLiF laser technology developed at NASA Langley was employed to permit study of the laser technology currently envisioned by NASA for global coherent Doppler lidar measurement of winds in the future. The 250 mJ, 10 Hz compact transceiver was also designed for future aircraft flight. Ground-based wind profiles made with this transceiver will be presented. NASA Langley is currently funded to build complete Doppler lidar systems using this transceiver for the DC-8 and WB-57 aircraft. The WB-57 flights will present a more severe environment and will require autonomous operation of the lidar system. The DC-8 lidar system is a likely component of future NASA hurricane research. It will include real-time data processing and display, as well as full data archiving. We will attempt to co-fly on both aircraft with a direct-detection Doppler wind lidar system being prepared by NASA Goddard Space Flight Center.

  18. Validar: a testbed for advanced 2-micron Doppler lidar

    NASA Astrophysics Data System (ADS)

    Koch, Grady J.; Petros, Mulugeta; Barnes, Bruce W.; Beyon, Jeffrey Y.; Amzajerdian, Farzin; Yu, Jirong; Kavaya, Michael J.; Singh, Upendra N.

    2004-09-01

    High-energy 2-micron lasers have been incorporated in a breadboard coherent Doppler lidar to test component technologies and explore applications for remote sensing of the atmosphere. Design of the lidar is presented including aspects in the laser transmitter, receiver, photodetector, and signal processing. Sample data is presented on wind profiling and CO2 concentration measurements.

  19. Validar: A Testbed for Advanced 2-Micron Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Petros, Mulugeta; Barnes, Bruce W.; Beyon, Jeffrey Y.; Amzajerdian, Farzin; Yu, Jirong; Kavaya, Michael J.; Singh, Upendra N.

    2004-01-01

    High-energy 2-microns lasers have been incorporated in a breadboard coherent Doppler lidar to test component technologies and explore applications for remote sensing of the atmosphere. Design of the lidar is presented including aspects in the laser transmitter, receiver, photodetector, and signal processing. Sample data is presented on wind profiling and CO2 concentration measurements.

  20. IIP Update: A Packaged Coherent Doppler Wind Lidar Transceiver. Doppler Aerosol WiNd Lidar (DAWN)

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Koch, Grady J.; Yu, Jirong; Trieu, Bo C.; Amzajerdian, Farzin; Singh, Upendra N.; Petros, Mulugeta

    2006-01-01

    The state-of-the-art 2-micron coherent Doppler wind lidar breadboard at NASA/LaRC will be engineered and compactly packaged consistent with future aircraft flights. The packaged transceiver will be integrated into a coherent Doppler wind lidar system test bed at LaRC. Atmospheric wind measurements will be made to validate the packaged technology. This will greatly advance the coherent part of the hybrid Doppler wind lidar solution to the need for global tropospheric wind measurements.

  1. Doppler Optical Coherence Tomography

    PubMed Central

    Leitgeb, Rainer A.; Werkmeister, René M.; Blatter, Cedric; Schmetterer, Leopold

    2014-01-01

    Optical Coherence Tomography (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood velocity and blood flow from tissues. A common problem with the technique is that the Doppler angle is not known and several approaches have been realized to obtain absolute velocity and flow data from the retina. Additional studies are required to elucidate which of these techniques is most promising. In the recent years, however, several groups have shown that data can be obtained with high validity and reproducibility. In addition, several groups have published values for total retinal blood flow. Another promising application relates to non-invasive angiography. As compared to standard techniques such as fluorescein and indocyanine-green angiography the technique offers two major advantages: no dye is required and depth resolution is required is provided. As such Doppler OCT has the potential to improve our abilities to diagnose and monitor ocular vascular diseases. PMID:24704352

  2. Application of coherent 10 micron imaging lidar

    SciTech Connect

    Simpson, M.L.; Hutchinson, D.P.; Richards, R.K.; Bennett, C.A.

    1997-04-01

    With the continuing progress in mid-IR array detector technology and high bandwidth fan-outs, i.f. electronics, high speed digitizers, and processing capability, true coherent imaging lidar is becoming a reality. In this paper experimental results are described using a 10 micron coherent imaging lidar.

  3. Potential for coherent Doppler wind velocity lidar using neodymium lasers

    NASA Technical Reports Server (NTRS)

    Kane, T. J.; Byer, R. L.; Zhou, B.

    1984-01-01

    Existing techniques for the frequency stabilization of Nd:YAG lasers operating at 1.06 micron, and the high-gain amplification of radiation at that wavelength, make possible the construction of a coherent Doppler wind velocity lidar using Nd:YAG. Velocity accuracy and range resolution are better at 1.06 micron than at 10.6 microns at the same level of the SNR. Backscatter from the atmosphere at 1.06 micron is greater than that at 10.6 microns by about 2 orders of magnitude, but the quantum-limited noise is higher by 100 also. Near-field attenuation and turbulent effects are more severe at 1.06 micron. In some configurations and environments, the 1.06-micron wavelength may be the better choice, and there may be technological advantages favoring the use of solid-state lasers in satellite systems.

  4. Coherent Doppler Laser Radar: Technology Development and Applications

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Arnold, James E. (Technical Monitor)

    2000-01-01

    NASA's Marshall Space Flight Center has been investigating, developing, and applying coherent Doppler laser radar technology for over 30 years. These efforts have included the first wind measurement in 1967, the first airborne flights in 1972, the first airborne wind field mapping in 1981, and the first measurement of hurricane eyewall winds in 1998. A parallel effort at MSFC since 1982 has been the study, modeling and technology development for a space-based global wind measurement system. These endeavors to date have resulted in compact, robust, eyesafe lidars at 2 micron wavelength based on solid-state laser technology; in a factor of 6 volume reduction in near diffraction limited, space-qualifiable telescopes; in sophisticated airborne scanners with full platform motion subtraction; in local oscillator lasers capable of rapid tuning of 25 GHz for removal of relative laser radar to target velocities over a 25 km/s range; in performance prediction theory and simulations that have been validated experimentally; and in extensive field campaign experience. We have also begun efforts to dramatically improve the fundamental photon efficiency of the laser radar, to demonstrate advanced lower mass laser radar telescopes and scanners; to develop laser and laser radar system alignment maintenance technologies; and to greatly improve the electrical efficiency, cooling technique, and robustness of the pulsed laser. This coherent Doppler laser radar technology is suitable for high resolution, high accuracy wind mapping; for aerosol and cloud measurement; for Differential Absorption Lidar (DIAL) measurements of atmospheric and trace gases; for hard target range and velocity measurement; and for hard target vibration spectra measurement. It is also suitable for a number of aircraft operations applications such as clear air turbulence (CAT) detection; dangerous wind shear (microburst) detection; airspeed, angle of attack, and sideslip measurement; and fuel savings through

  5. Coherent Doppler Laser Radar: Technology Development and Applications

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Arnold, James E. (Technical Monitor)

    2000-01-01

    NASA's Marshall Space Flight Center has been investigating, developing, and applying coherent Doppler laser radar technology for over 30 years. These efforts have included the first wind measurement in 1967, the first airborne flights in 1972, the first airborne wind field mapping in 1981, and the first measurement of hurricane eyewall winds in 1998. A parallel effort at MSFC since 1982 has been the study, modeling and technology development for a space-based global wind measurement system. These endeavors to date have resulted in compact, robust, eyesafe lidars at 2 micron wavelength based on solid-state laser technology; in a factor of 6 volume reduction in near diffraction limited, space-qualifiable telescopes; in sophisticated airborne scanners with full platform motion subtraction; in local oscillator lasers capable of rapid tuning of 25 GHz for removal of relative laser radar to target velocities over a 25 km/s range; in performance prediction theory and simulations that have been validated experimentally; and in extensive field campaign experience. We have also begun efforts to dramatically improve the fundamental photon efficiency of the laser radar, to demonstrate advanced lower mass laser radar telescopes and scanners; to develop laser and laser radar system alignment maintenance technologies; and to greatly improve the electrical efficiency, cooling technique, and robustness of the pulsed laser. This coherent Doppler laser radar technology is suitable for high resolution, high accuracy wind mapping; for aerosol and cloud measurement; for Differential Absorption Lidar (DIAL) measurements of atmospheric and trace gases; for hard target range and velocity measurement; and for hard target vibration spectra measurement. It is also suitable for a number of aircraft operations applications such as clear air turbulence (CAT) detection; dangerous wind shear (microburst) detection; airspeed, angle of attack, and sideslip measurement; and fuel savings through

  6. 2-Micron Diode-Pumped Pulsed Laser Transmitter for SPARCLE: A Coherent Wind Lidar Shuttle Mission

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Barnes, Norman P.; Phillips, Mark W.

    1998-01-01

    To enable a tropospheric vector wind velocity profiling from space with a pulsed Doppler lidar, a diode-pumped, room temperature Ho:Tm:YLF coherent pulsed transmitter has been developed at NASA Langley Research Center. This pulsed laser transmitter will be a part of coherent wind lidar shuttle mission SPARCLE. The acronym stands for SPAce Readiness Coherent Lidar Experiment and is primarily a technology demonstration mission and is expected to fly in 2001 as NASA's New Millennium Program (NMP) second Earth Orbiter (EO-2) mission. The laser transmitter for SPARCLE is a Ho:Tm:YLF power oscillator operating at eye-safe wavelength of 2.05 microns. The Q-switched output energy is 125 mJ at six Hz, and it has a near-transform limited beam with a pulse width of 170 ns. The high power and high beam quality of this laser makes it well suited as a coherent wind lidar transmitter on a space platform. When the output of this power oscillator is amplified by using four diode-pumped Ho:Tm:YLF amplifiers, an output energy of 600 mJ at 10 Hz is achieved. This is the highest energy ever produced at 10 Hz, and is at least an order of magnitude greater than previously achieved for a 2-micron diode-pumped laser at room temperature.

  7. 2-Micron Diode-Pumped Pulsed Laser Transmitter for SPARCLE: A Coherent Wind Lidar Shuttle Mission

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Barnes, Norman P.; Phillips, Mark W.

    1998-01-01

    To enable a tropospheric vector wind velocity profiling from space with a pulsed Doppler lidar, a diode-pumped, room temperature Ho:Tm:YLF coherent pulsed transmitter has been developed at NASA Langley Research Center. This pulsed laser transmitter will be a part of coherent wind lidar shuttle mission SPARCLE. The acronym stands for SPAce Readiness Coherent Lidar Experiment and is primarily a technology demonstration mission and is expected to fly in 2001 as NASA's New Millennium Program (NMP) second Earth Orbiter (EO-2) mission. The laser transmitter for SPARCLE is a Ho:Tm:YLF power oscillator operating at eye-safe wavelength of 2.05 microns. The Q-switched output energy is 125 mJ at six Hz, and it has a near-transform limited beam with a pulse width of 170 ns. The high power and high beam quality of this laser makes it well suited as a coherent wind lidar transmitter on a space platform. When the output of this power oscillator is amplified by using four diode-pumped Ho:Tm:YLF amplifiers, an output energy of 600 mJ at 10 Hz is achieved. This is the highest energy ever produced at 10 Hz, and is at least an order of magnitude greater than previously achieved for a 2-micron diode-pumped laser at room temperature.

  8. Applications of Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Xu, Zhiqiang

    A major development in biomedical imaging in the last decade has been optical coherence tomography (OCT). This technique enables microscale resolution, depth resolved imaging of the detailed morphology of transparent and nontransparent biological tissue in a noncontact and quasi-noninvasive way. In the first part of this dissertation, we will describe the development and the performance of our home-made OCT systems working with different wavelength regions based on free-space and optical fiber Michelson interferometers. The second part will focus on Doppler OCT (DOCT), an important extension of OCT, which enables the simultaneous evaluation of the structural information and of the fluid flow distribution at a localized position beneath the sample surface. Much effort has been spent during the past few years in our laboratory aimed at providing more accurate velocity measurements with an extended dynamic range. We also applied our technique in different research areas such as microfluidics and hemodynamics. Investigations on the optical properties of the biological tissues (such as absorption and scattering) corresponding to different center wavelengths, have been performed in our laboratory. We used a 10 femtosecond Ti:sapphire laser centered at about 810 nm associated with a free-space Michelson interferometer. The infrared sources were centered at about 1310 and 1560 nm with all-fiber interferometers. Comparative studies using three different sources for several in vitro biological tissues based on a graphical method illustrated how the optical properties affect the quality of the OCT images in terms of the penetration depth and backscattering intensity. We have shown the advantage of working with 810-nm emission wavelength for good backscattering amplitude and contrast, while sources emitting at 1570 nm give good penetration depth. The 1330-nm sources provide a good compromise between the two. Therefore, the choice of the source will ultimately determine the

  9. A Two Micron Coherent Differential Absorption Lidar Development

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Bai, Yingxin; Petzar, Paul J.; Trieu, Bo C.; Koch, Grady J.; Beyon, Jeffrey Y.; VanValkenburg, Randal L.; Kavaya, Michael J.; Singh, Upendra N.

    2010-01-01

    A pulsed, 2-micron coherent Differential Absorption Lidar (DIAL)/Integrated Path Differential Absorption (IPDA) transceiver, developed under the Laser Risk Reduction Program (LRRP) at NASA, is integrated into a fully functional lidar instrument. This instrument measures atmospheric CO2 profiles (by DIAL) from a ground platform. It allows the investigators to pursue subsequent in science-driven deployments, and provides a unique tool for Active Sensing of CO2 Emissions over Night, Days, and Seasons (ASCENDS) validation that was strongly advocated in the recent ASCENDS Workshop. Keywords: Differential Absorption Lidar, Near Infrared Laser,

  10. Doppler optical coherence tomography in cardiovascular physiology

    NASA Astrophysics Data System (ADS)

    Bonesi, M.; Meglinski, I.; Matcher, S.

    2008-09-01

    The study of flow dynamics in complex geometry vessels is highly important in many biomedical applications where the knowledge of the mechanic interactions between the moving fluid and the housing media plays a key role for the determination of the parameters of interest, including the effect of blood flow on the possible rupture of atherosclerotic plaques. Doppler Optical Coherence Tomography (DOCT), as a functional extension of Optical Coherence Tomography (OCT), is an optic, non-contact, non-invasive technique able to achieve detailed analysis of the flow/vessel interactions. It allows simultaneous high resolution imaging (10 μm typical) of the morphology and composition of the vessel and determination of the flow velocity distribution along the measured cross-section. We applied DOCT system to image high-resolution one-dimensional and multi-dimensional velocity distribution profiles of Newtonian and non-Newtonian fluids flowing in vessels with complex geometry, including Y-shaped and T-shaped vessels, vessels with aneurism, bifurcated vessels with deployed stent and scaffolds. The phantoms were built to mimic typical shapes of human blood vessels, enabling preliminary analysis of the interaction between flow dynamics and the (complex) geometry of the vessels and also to map the related velocity profiles at several inlet volume flow rates. Feasibility studies for quantitative observation of the turbulence of flows arising within the complex geometry vessels are discussed. In addition, DOCT technique was also applied for monitoring cerebral mouse blood flow in vivo. Two-dimensional DOCT images of complex flow velocity profiles in blood vessel phantoms and in vivo sub-cranial mouse blood flow velocities distributions are presented.

  11. Doppler optical coherence tomography in cardiovascular applications

    NASA Astrophysics Data System (ADS)

    Bonesi, M.; Matcher, S.; Meglinski, I.

    2010-06-01

    The study of flow dynamics in complex geometry vessels is highly important in various biomedical applications where the knowledge of the mechanic interactions between the moving fluid and the housing media plays a key role for the determination of the parameters of interest, including the effect of blood flow on the possible rupture of atherosclerotic plaques. Doppler Optical Coherence Tomography (DOCT), as a functional extension of Optical Coherence Tomography (OCT), is an optic, non-contact, noninvasive technique able to achieve detailed analysis of the flow/vessel interactions. It allows simultaneous high resolution imaging (˜10 µm typical) of the morphology and composition of the vessel and determination of the flow velocity distribution along the measured cross-section. We applied DOCT system to image high-resolution one-dimensional and multi-dimensional velocity distribution profiles of Newtonian and non-Newtonian fluids flowing in vessels with complex geometry, including Y-shaped and T-shaped vessels, vessels with aneurism, bifurcated vessels with deployed stent and scaffolds. The phantoms were built to mimic typical shapes of human blood vessels, enabling preliminary analysis of the interaction between flow dynamics and the (complex) geometry of the vessels and also to map the related velocity profiles at several inlet volume flow rates. Feasibility studies for quantitative observation of the turbulence of flows arising within the complex geometry vessels are discussed. In addition, DOCT technique was also applied for monitoring cerebral mouse blood flow in vivo. Two-dimensional DOCT images of complex flow velocity profiles in blood vessel phantoms and in vivo sub-cranial mouse blood flow velocities distributions are presented.

  12. Micron-scale coherence in interphase chromatin dynamics

    PubMed Central

    Zidovska, Alexandra; Weitz, David A.; Mitchison, Timothy J.

    2013-01-01

    Chromatin structure and dynamics control all aspects of DNA biology yet are poorly understood, especially at large length scales. We developed an approach, displacement correlation spectroscopy based on time-resolved image correlation analysis, to map chromatin dynamics simultaneously across the whole nucleus in cultured human cells. This method revealed that chromatin movement was coherent across large regions (4–5 µm) for several seconds. Regions of coherent motion extended beyond the boundaries of single-chromosome territories, suggesting elastic coupling of motion over length scales much larger than those of genes. These large-scale, coupled motions were ATP dependent and unidirectional for several seconds, perhaps accounting for ATP-dependent directed movement of single genes. Perturbation of major nuclear ATPases such as DNA polymerase, RNA polymerase II, and topoisomerase II eliminated micron-scale coherence, while causing rapid, local movement to increase; i.e., local motions accelerated but became uncoupled from their neighbors. We observe similar trends in chromatin dynamics upon inducing a direct DNA damage; thus we hypothesize that this may be due to DNA damage responses that physically relax chromatin and block long-distance communication of forces. PMID:24019504

  13. Coherent laser radar at 2 microns using solid-state lasers

    NASA Technical Reports Server (NTRS)

    Henderson, Sammy W.; Suni, Paul J. M.; Hale, Charley P.; Hannon, Stephen M.; Magee, James R.; Bruns, Dale L.; Yuen, Eric H.

    1993-01-01

    Coherent laser radar systems using 2-micron Tm- and Tm, Ho-doped solid-state lasers are useful for the remote range-resolved measurement of atmospheric winds, aerosol backscatter, and DIAL measurements of atmospheric water vapor and CO2 concentrations. Recent measurements made with a 2-micron coherent laser radar system, advances in the laser technology, and atmospheric propagation effects on 2-micron coherent lidar performance are described.

  14. Comparison of 2 micron Ho and 10 micron CO2 lidar for atmospheric backscatter and Doppler windshear detection

    NASA Technical Reports Server (NTRS)

    Killinger, Dennis

    1991-01-01

    The development of eye-safe, solid-state Lidar systems is discussed, with an emphasis on Coherent Doppler Lidar for Atmospheric Wind Measurements. The following subject areas are covered: tunable Ho DIAL (Differential Absorption Lidar)/lidar atmospheric measurements; atmospheric turbulence measurements and detector arrays; diurnal measurements of C(sub n)(sup 2) for KSC lidar measurements; and development of single-frequency Ho laser/lidar.

  15. Compact and Rugged Transceiver for Coherent Doppler Wind Lidar Applications in Space

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Koch, Grady J.; Yu, Jirong; Amzajerdian, Farzin; Singh, Upendra N.; Trieu, Bo C.; Modlin, Ed A.; Petros, Mulugeta; Bai, Yingxin; Reithmaier, Karl; Petzar, Paul J.

    2007-01-01

    High-accuracy, vertical profiles of the horizontal vector wind in earth s atmosphere, with the global coverage of an orbiting sensor, are a highly desired measurement of NASA, NOAA, and many other agencies and countries. It is the consensus of NASA and NOAA that the most cost effective, lowest risk measurement method with the earliest achievable mission date is the hybrid Doppler lidar method which utilizes both coherent- and direct-detection Doppler lidars to obtain the desired profiles. NASA Langley Research Center (LaRC) has advanced the 2-micron pulsed solid-state laser greatly over the past 15 years and has recently demonstrated 1.2 J of pulse energy whereas the requirement for a 400-km hybrid Doppler lidar mission is only 0.25 J. The IIP project reported here is an effort to increase the ruggedness and to compactly package the LaRC state-of-the-art laser technology.

  16. 2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Bai, Yingxin; Yu, Jirong

    2009-01-01

    Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed in NASA Langley Research Center. This laser system is capable of making a vertical profiling of CO2 from ground and column measurement of CO2 from air and space-borne platform. The transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. A Ho:YLF laser operating in the range of 2.05 micrometers can be tuned over several characteristic lines of CO2 absorption. Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of CO2 with a repetition rate of 5 Hz and pulse energy of 75 mJ. For coherent detection, high repetition rate is required for speckle averaging to obtain highly precise measurements. However, a diode pumped Ho:Tm:YLF laser can not operate in high repetition rate due to the large heat loading and up-conversion. A Tm:fiber laser pumped Ho:YLF laser with low heat loading can operate in high repetition rate. A theoretical model has been established to simulate the performance of Tm:fiber laser pumped Ho:YLF lasers. For continuous wave (CW) operation, high pump intensity with small beam

  17. 2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Bai, Yingxin; Yu, Jirong

    2009-01-01

    Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed in NASA Langley Research Center. This laser system is capable of making a vertical profiling of CO2 from ground and column measurement of CO2 from air and space-borne platform. The transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. A Ho:YLF laser operating in the range of 2.05 micrometers can be tuned over several characteristic lines of CO2 absorption. Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of CO2 with a repetition rate of 5 Hz and pulse energy of 75 mJ. For coherent detection, high repetition rate is required for speckle averaging to obtain highly precise measurements. However, a diode pumped Ho:Tm:YLF laser can not operate in high repetition rate due to the large heat loading and up-conversion. A Tm:fiber laser pumped Ho:YLF laser with low heat loading can operate in high repetition rate. A theoretical model has been established to simulate the performance of Tm:fiber laser pumped Ho:YLF lasers. For continuous wave (CW) operation, high pump intensity with small beam

  18. Low Cost Coherent Doppler Lidar Data Acquisition and Processing

    NASA Technical Reports Server (NTRS)

    Barnes, Bruce W.; Koch, Grady J.

    2003-01-01

    The work described in this paper details the development of a low-cost, short-development time data acquisition and processing system for a coherent Doppler lidar. This was done using common laboratory equipment and a small software investment. This system provides near real-time wind profile measurements. Coding flexibility created a very useful test bed for new techniques.

  19. Coherent Doppler Lidar for Precision Navigation of Spacecrafts

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Pierrottet, Diego; Petway, Larry; Hines, Glenn; Lockhard, George; Barnes, Bruce

    2011-01-01

    A fiber-based coherent Doppler lidar, utilizing an FMCW technique, has been developed and its capabilities demonstrated through two successful helicopter flight test campaigns. This Doppler lidar is expected to play a critical role in future planetary exploration missions because of its ability in providing the necessary data for soft landing on the planetary bodies and for landing missions requiring precision navigation to the designated location on the ground. Compared with radars, the Doppler lidar can provide significantly higher precision velocity and altitude data at a much higher rate without concerns for measurement ambiguity or target clutter. Future work calls for testing the Doppler lidar onboard a rocket-powered free-flyer platform operating in a closed-loop with the vehicle s guidance, navigation, and control (GN&C) unit.

  20. Ultrahigh-velocity resolution imaging of the microcirculation in-vivo using color Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yazdanfar, Siavash; Rollins, Andrew M.; Izatt, Joseph A.

    2001-05-01

    Color Doppler optical coherence tomography (CDOCT) is a method for noninvasive cross-sectional imaging of blood flow in vivo. In previous implementations, velocity estimates were obtained by measuring the frequency shift of discrete depth-resolved backscatter spectra, resulting in a velocity resolution on the order of 1 mm/s. We present a novel processing method that detects Doppler shifts calculated across sequential axial scans, enabling ultrahigh velocity resolution (~1 micron/s) flow measurement in scattering media. This method of sequential scan processing was calibrated with a moving mirror mounted on a precision motorized translator. Latex microspheres suspended in deuterium oxide were used as a highly scattering test phantom. Laminar flow profiles down to ~15 micron/s centerline velocity (0.02 cc/hr) were observed with a sensitivity of 1.2 micron/s. Finally, vessels on the order of 10 microns in diameter were imaged in living human skin, with a relative frequency sensitivity less than 4 x 10-5. To our knowledge, these results are the lowest velocities ever measured with CDOCT.

  1. Ge's Mobile, Coherent Doppler Lidar Test/Ealuation Facilities

    NASA Technical Reports Server (NTRS)

    Sroga, J. T.; Scott, J. W.; Kiernan, S. C.; Weaver, F. J.; Trotta, J. E.; Petheram, J. C.

    1992-01-01

    The primary objective of this independent research and development (IR and D) program in support of the Laser Atmospheric Wind Sounder (LAWS) program is to develop and evaluate technologies with direct applications to spaceborne laser wind sensing, and to develop system level engineering experience in designing, operating, and modeling a coherent Doppler lidar. GE is developing a mobile, ground based coherent Doppler lidar as an end-to-end system level test facility to evaluate applicable technologies, verify system level performance issues, perform instrument calibration, and validate end-to-end system performance model predictions. Here, the primary focus is on a description of the ground based lidar system and the performance during the initial shakedown operation after system integration.

  2. Performance of a 1-micron, 1-joule Coherent Launch Site Atmospheric Wind Sounder

    NASA Technical Reports Server (NTRS)

    Hawley, James G.; Targ, Russell; Bruner, Richard; Henderson, Sammy W.; Hale, Charles P.; Vetorino, Steven; Lee, R. W.; Harper, Scott; Khan, Tayyab

    1992-01-01

    The paper describes the design and performance of the Coherent Launch Site Atmospheric Wind Sounder (CLAWS), which is a test and demonstration program designed for monitoring winds with a solid-state lidar in real time for the launch site vehicle guidance and control application. Analyses were conducted to trade off CO2 (9.11- and 10.6-microns), Ho:YAG (2.09 microns), and Nd:YAG (1.06-micron) laser-based lidars. The measurements set a new altitude record (26 km) for coherent wind measurements in the stratosphere.

  3. Performance of a 1-micron, 1-joule Coherent Launch Site Atmospheric Wind Sounder

    NASA Technical Reports Server (NTRS)

    Hawley, James G.; Targ, Russell; Bruner, Richard; Henderson, Sammy W.; Hale, Charles P.; Vetorino, Steven; Lee, R. W.; Harper, Scott; Khan, Tayyab

    1992-01-01

    The paper describes the design and performance of the Coherent Launch Site Atmospheric Wind Sounder (CLAWS), which is a test and demonstration program designed for monitoring winds with a solid-state lidar in real time for the launch site vehicle guidance and control application. Analyses were conducted to trade off CO2 (9.11- and 10.6-microns), Ho:YAG (2.09 microns), and Nd:YAG (1.06-micron) laser-based lidars. The measurements set a new altitude record (26 km) for coherent wind measurements in the stratosphere.

  4. Evaluation of the MV (CAPON) Coherent Doppler Lidar Velocity Estimator

    NASA Technical Reports Server (NTRS)

    Lottman, B.; Frehlich, R.

    1997-01-01

    The performance of the CAPON velocity estimator for coherent Doppler lidar is determined for typical space-based and ground-based parameter regimes. Optimal input parameters for the algorithm were determined for each regime. For weak signals, performance is described by the standard deviation of the good estimates and the fraction of outliers. For strong signals, the fraction of outliers is zero. Numerical effort was also determined.

  5. Phase-referenced Doppler optical coherence tomography in scattering media.

    PubMed

    Pedersen, Cameron J; Yazdanfar, Siavash; Westphal, Volker; Rollins, Andrew M

    2005-08-15

    We present a fiber-based, low-coherence interferometer that significantly reduces phase noise by incorporating a second, narrowband, continuous-wave light source as a phase reference. By incorporating this interferometer into a Doppler OCT system, we demonstrate significant velocity noise reduction in reflective and scattering samples using processing techniques amenable to real-time implementation. We also demonstrate 90% suppression of velocity noise in a flow phantom.

  6. The Novel Nonlinear Adaptive Doppler Shift Estimation Technique and the Coherent Doppler Lidar System Validation Lidar

    NASA Technical Reports Server (NTRS)

    Beyon, Jeffrey Y.; Koch, Grady J.

    2006-01-01

    The signal processing aspect of a 2-m wavelength coherent Doppler lidar system under development at NASA Langley Research Center in Virginia is investigated in this paper. The lidar system is named VALIDAR (validation lidar) and its signal processing program estimates and displays various wind parameters in real-time as data acquisition occurs. The goal is to improve the quality of the current estimates such as power, Doppler shift, wind speed, and wind direction, especially in low signal-to-noise-ratio (SNR) regime. A novel Nonlinear Adaptive Doppler Shift Estimation Technique (NADSET) is developed on such behalf and its performance is analyzed using the wind data acquired over a long period of time by VALIDAR. The quality of Doppler shift and power estimations by conventional Fourier-transform-based spectrum estimation methods deteriorates rapidly as SNR decreases. NADSET compensates such deterioration in the quality of wind parameter estimates by adaptively utilizing the statistics of Doppler shift estimate in a strong SNR range and identifying sporadic range bins where good Doppler shift estimates are found. The authenticity of NADSET is established by comparing the trend of wind parameters with and without NADSET applied to the long-period lidar return data.

  7. Coherent Doppler Lidar Data Products from Space-Based Platforms

    NASA Technical Reports Server (NTRS)

    Frehlich, Rod

    1999-01-01

    Coherent Doppler lidar is a promising technique for the global measurements of winds using a space-based platform. Doppler lidar produces estimates of the radial component of the velocity vector averaged over the resolution volume of the measurement. Profiles of the horizontal vector winds are produced by scanning the lidar beam or stepping the lidar beam through a sequence of different angles (step-stare). The first design for space-based measurements proposed a conical scan which requires a high power laser to produce acceptable signal levels for every laser pulse. Performance is improved by fixing the laser beam and accumulating the signal from many lidar pulses for each range-gate. This also improves the spatial averaging of the wind estimates and reduces the threshold signal energy required for a good estimate. Coherent Doppler lidar performance for space-based operation is determined using computer simulations and including the wind variability over the measurement volume as well as the variations of the atmospheric aerosol backscatter.

  8. Volumetric Doppler angle correction for ultrahigh-resolution optical coherence Doppler tomography

    NASA Astrophysics Data System (ADS)

    You, Jiang; Li, Ang; Du, Congwu; Pan, Yingtian

    2017-01-01

    Ultrahigh-resolution optical coherence Doppler tomography (μODT) demonstrates great potential for quantitative blood flow imaging owing to its large field of view and capillary resolution. However, μODT only detects the axial flow velocity and requires Doppler angle correction to retrieve the absolute velocity. Although methods for Doppler angle tracking of single or few large vessels have been reported, a method that enables angle correction of the entire 3D microvascular networks remains a challenge. Here, we present a method based on eigenvalue analysis of 3D Hessian matrix to retrieve the orientation of each tubular vessel. As the algorithm is voxel based, it is suitable for effective tracking of Doppler angle matrix and restoring the absolute flow over the 3D vascular flow networks. We present results on simulation and flow phantom studies to show its efficacy for accurate 3D angle tracking and absolute flow correction. Then, we perform an in vivo validation study on mouse micro-circulatory cerebral blood flow (CBF) networks, which clearly demonstrates the capability of this method for tracking the Doppler angle matrix of the highly complex 3D CBF networks.

  9. Coherent Doppler Lidar Deployment in the Canopy Horizontal Array Turbulence Study

    DTIC Science & Technology

    2008-02-06

    REPORT Coherent Doppler Lidar Deployment in the Canopy Horizontal Array Turbulence Study 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: The PI’s and ASU...students/staff deployed their coherent Doppler lidar from May 9, 2007 to June 11, 2007 in support of the Canopy Horizontal Array Turbulence Study...DATES COVERED (From - To) 29-Mar-2007 Standard Form 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 - 28-Dec-2007 Coherent Doppler Lidar Deployment in

  10. Coherent Doppler lidar signal covariance including wind shear and wind turbulence

    NASA Technical Reports Server (NTRS)

    Frehlich, R. G.

    1993-01-01

    The performance of coherent Doppler lidar is determined by the statistics of the coherent Doppler signal. The derivation and calculation of the covariance of the Doppler lidar signal is presented for random atmospheric wind fields with wind shear. The random component is described by a Kolmogorov turbulence spectrum. The signal parameters are clarified for a general coherent Doppler lidar system. There are two distinct physical regimes: one where the transmitted pulse determines the signal statistics and the other where the wind field dominates the signal statistics. The Doppler shift of the signal is identified in terms of the wind field and system parameters.

  11. Aerosol/Cloud Measurements Using Coherent Wind Doppler Lidars

    NASA Astrophysics Data System (ADS)

    Royer, Philippe; Boquet, Matthieu; Cariou, Jean-Pierre; Sauvage, Laurent; Parmentier, Rémy

    2016-06-01

    The accurate localization and characterization of aerosol and cloud layers is crucial for climate studies (aerosol indirect effect), meteorology (Planetary Boundary Layer PBL height), site monitoring (industrial emissions, mining,…) and natural hazards (thunderstorms, volcanic eruptions). LEOSPHERE has recently developed aerosol/cloud detection and characterization on WINDCUBE long range Coherent Wind Doppler Lidars (CWDL). These new features combine wind and backscatter intensity informations (Carrier-to-Noise Ratio CNR) in order to detect (aerosol/cloud base and top, PBL height) and to characterize atmospheric structures (attenuated backscatter, depolarization ratio). For each aerosol/cloud functionality the method is described, limitations are discussed and examples are given to illustrate the performances.

  12. Microvascular anastomosis in rodent model evaluated by Fourier domain Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Huang, Yong; Tong, Dedi; Zhu, Shan; Wu, Lehao; Ibrahim, Zuhaib; Lee, WP Andrew; Brandacher, Gerald; Kang, Jin U.

    2014-03-01

    Vascular and microvascular anastomosis are critical components of reconstructive microsurgery, vascular surgery and transplant surgery. Imaging modality that provides immediate, real-time in-depth view and 3D structure and flow information of the surgical site can be a great valuable tool for the surgeon to evaluate surgical outcome following both conventional and innovative anastomosis techniques, thus potentially increase the surgical success rate. Microvascular anastomosis for vessels with outer diameter smaller than 1.0 mm is extremely challenging and effective evaluation of the outcome is very difficult if not impossible using computed tomography (CT) angiograms, magnetic resonance (MR) angiograms and ultrasound Doppler. Optical coherence tomography (OCT) is a non-invasive high-resolution (micron level), high-speed, 3D imaging modality that has been adopted widely in biomedical and clinical applications. Phaseresolved Doppler OCT that explores the phase information of OCT signals has been shown to be capable of characterizing dynamic blood flow clinically. In this work, we explore the capability of Fourier domain Doppler OCT as an evaluation tool to detect commonly encountered post-operative complications that will cause surgical failure and to confirm positive result with surgeon's observation. Both suture and cuff based techniques were evaluated on the femoral artery and vein in the rodent model.

  13. Coherent Laser Spectroscopy and Doppler Lidar Sensing in the Atmosphere

    NASA Astrophysics Data System (ADS)

    Vaughan, J. M.

    The principles of coherent laser spectroscopy are briefly reviewed in which a signal beam is heterodyned with an optical local oscillator beam. The frequency and single mode selectivity this provides is shown to be very advantageous. This is illustrated by recent work on the properties of different classes of light field, including the fractal character of Gaussian-Lorentzian light, and by several aspects of laser physics. In equivalent practical applications to remote sensing in the atmosphere, coherent Doppler lidar provides a powerful technique. This is illustrated by measurements of wind fields and aircraft wake vortices. Airborne equipments have been used for measurements of true airspeed, wind shear warning and atmospheric backscatter levels. Future space-borne lidars could potentially measure the global wind field - of great benefit for numerical weather forecasting and climate studies.

  14. In vivo feasibility of endovascular Doppler optical coherence tomography

    PubMed Central

    Sun, Cuiru; Nolte, Felix; Cheng, Kyle H. Y.; Vuong, Barry; Lee, Kenneth K. C.; Standish, Beau A.; Courtney, Brian; Marotta, Thomas R.; Mariampillai, Adrian; Yang, Victor X. D.

    2012-01-01

    Feasibility of detecting intravascular flow using a catheter based endovascular optical coherence tomography (OCT) system is demonstrated in a porcine carotid model in vivo. The effects of A-line density, radial distance, signal-to-noise ratio, non-uniform rotational distortion (NURD), phase stability of the swept wavelength laser and interferometer system on Doppler shift detection limit were investigated in stationary and flow phantoms. Techniques for NURD induced phase shift artifact removal were developed by tracking the catheter sheath. Detection of high flow velocity (~51 cm/s) present in the porcine carotid artery was obtained by phase unwrapping techniques and compared to numerical simulation, taking into consideration flow profile distortion by the eccentrically positioned imaging catheter. Using diluted blood in saline mixture as clearing agent, simultaneous Doppler OCT imaging of intravascular flow and structural OCT imaging of the carotid artery wall was feasible. To our knowledge, this is the first in vivo demonstration of Doppler imaging and absolute measurement of intravascular flow using a rotating fiber catheter in carotid artery. PMID:23082299

  15. Method and apparatus for generating coherent near 14 and near 16 micron radiation

    DOEpatents

    Krupke, William F.

    1977-01-01

    A method and apparatus for producing coherent radiation in CO.sub.2 vibrational-rotational transitions at wavelengths near 14 and 16 microns. This is accomplished by passing a mixture of N.sub.2 and Ar through a glow discharge producing a high vibrational temperature in the N.sub.2, passing the excited N.sub.2 through a nozzle bank creating a supersonic flow thereof, injecting the CO.sub.2 in the supersonic flow creating a population inversion in the CO.sub.2, and directing the saturating pulse of radiation near 10.6 or 9.6 microns into the excited CO.sub.2 creating a population inversion producing coherent radiation at 14 or 16 microns, respectively.

  16. Study of coherent clutter model for airborne pulse-Doppler radar

    NASA Astrophysics Data System (ADS)

    Chen, Xingyu; Guan, Yifu

    2017-08-01

    This paper gives an efficient coherent clutter model for airborne pulse-Doppler radar in arbitrary posture. The ground is separated by range rings and angle units instead of range rings with Doppler units so as to reduce the computation cost. The MATLAB simulation gives the range-Doppler map of the clutter and the result proves the effectiveness of the clutter model.

  17. High resolution Fourier domain Optical Coherence Tomography at 2 microns for painted objects

    NASA Astrophysics Data System (ADS)

    Liang, H.; Cheung, C. S.; Daniel, J. M. O.; Tokurakawa, M.; Clarkson, W. A.; Spring, M.

    2015-06-01

    Optical Coherence Tomography has been successfully applied to the non-invasive imaging of subsurface microstructure of a variety of materials from biological tissues to painted objects of art. One of the limitations of the technique is the low depth of penetration due to the strong scattering and absorption in the material. Previous studies found that for paint materials, the optimum window for large depth of penetration is around 2.2 microns. This is also true for many other materials with low water content. We have previously demonstrated OCT systems in this wavelength regime for imaging with improved depth of penetration. In this paper, we present an improved 2 micron high resolution Fourier domain OCT system using a broadband supercontinuum source. The system achieved a depth resolution of 9 microns in air (or 6 microns in paint or any polymer).

  18. Atmospheric wind sensing with a 1 and 2 micron coherent lidar

    NASA Technical Reports Server (NTRS)

    Huffaker, R. Milton; Henderson, Sammy W.

    1992-01-01

    The majority of coherent lidar remote sensing performed to date has utilized carbon dioxide gas laser technology at wavelengths of 9 to 11 microns. However, the use of rapidly developing solid state laser technology and the shorter wavelengths offers many potential advantages. These advantages include low mass, small size, long shelf and operating lifetimes, the absence of consumables, and in many cases, increased atmospheric transmission. The shorter wavelengths of solid state lasers allow velocity measurements having better range resolution for equivalent wind velocity resolution. Coherent Technologies, Inc. has developed a 1.06 and 2.1 micron coherent lidar system for remote wind field measurements. This system is described, and some performance data are given.

  19. Coherent Flow Power Doppler (CFPD): Flow Detection using Spatial Coherence Beamforming

    PubMed Central

    Li, You Leo; Dahl, Jeremy J.

    2015-01-01

    Power Doppler imaging is a widely used method of flow detection for tissue perfusion monitoring, inflammatory hyperemia detection, deep vein thrombosis diagnosis, and other clinical applications. However, thermal noise and clutter limit its sensitivity and ability to detect slow flow. In addition, large ensembles are required to obtain sufficient sensitivity, which limits frame rate and yields flash artifacts during moderate tissue motion. We propose an alternative method of flow detection using the spatial coherence of backscattered ultrasound echoes. The method enhances slow flow detection and frame rate, while maintaining or improving the signal quality of conventional power Doppler techniques. The feasibility of this method is demonstrated with simulations, flow-phantom experiments, and an in-vivo human thyroid study. In comparison to conventional power Doppler imaging, the proposed method can produce Doppler images with 15-30 dB SNR improvement. Therefore, it is able to detect flow with velocities approximately 50% lower than conventional power Doppler, or improve the frame rate by a factor of 3 with comparable image quality. The results show promise for clinical applications of the method. PMID:26067037

  20. Optical coherence Doppler tomography for quantitative cerebral blood flow imaging

    PubMed Central

    You, Jiang; Du, Congwu; Volkow, Nora D.; Pan, Yingtian

    2014-01-01

    Optical coherence Doppler tomography (ODT) is a promising neurotechnique that permits 3D imaging of the cerebral blood flow (CBF) network; however, quantitative CBF velocity (CBFv) imaging remains challenging. Here we present a simple phase summation method to enhance slow capillary flow detection sensitivity without sacrificing dynamic range for fast flow and vessel tracking to improve angle correction for absolute CBFv quantification. Flow phantom validation indicated that the CBFv quantification accuracy increased from 15% to 91% and the coefficient of variation (CV) decreased 9.3-fold; in vivo mouse brain validation showed that CV decreased 4.4-/10.8- fold for venular/arteriolar flows. ODT was able to identify cocaine-elicited microischemia and quantify CBFv disruption in branch vessels and capillaries that otherwise would have not been possible. PMID:25401033

  1. Coherent Doppler lidar signal spectrum with wind turbulence.

    PubMed

    Frehlich, R; Cornman, L

    1999-12-20

    The average signal spectrum (periodogram) for coherent Doppler lidar is calculated for a turbulent wind field. Simple approximations are compared with the exact calculation. The effects of random errors in the zero velocity reference, the effects of averaging spectral estimates by use of multiple lidar pulses, and the effects of the range dependence of the lidar signal power over the range gate are included. For high spatial resolution measurements the lidar signal power is concentrated around one spectral estimate (spectral bin), and correct interpretation of the contribution from turbulence is difficult because of the effects of spectral leakage. For range gates that are larger than the lidar pulse volume, the signal power is contained in many spectral bins and the effects of turbulence can be determined accurately for constant signal power over the range gate and for the far-field range dependence of the signal power.

  2. Coherent Doppler lidars: Current US 9-11 micrometer systems

    NASA Technical Reports Server (NTRS)

    Hall, Freeman F., Jr.

    1985-01-01

    To gain a proper perspective of the potential of coherent Doppler lidars for global wind sensing sometime in the future, we need to examine where we are, how we got here, and the expectations for future lidar system development. First we give a brief review of lidar developments leading to our present technology. Next we survey present U.S. infrared systems with particular attention to the pulsed systems since they are the ones that will have sufficient range to operate from satellites. Finally we comment on trends and probable future developments. Only unclassified lidars are considered. The considerable DoD support for classified applications certainly enhances future developments in components and subsystems.

  3. Coherent Doppler Lidar for Wind and Cloud Measurements on Venus from an Orbiting or Floating/Flying Platform

    NASA Astrophysics Data System (ADS)

    Singh, Upendra; Limaye, Sanjay; Emmitt, George; Kavaya, Michael; Yu, Jirong; Petros, Mulugeta

    Abstract Given the presence of clouds and haze in the upper portion of the Venus atmosphere, it is reasonable to consider a Doppler wind lidar (DWL) for making remote measurements of the 3D winds within the tops of clouds and the overlying haze layer. Assuming an orbit altitude of 250 km and cloud tops at 60km (within the “upper cloud layer”), an initial performance assessment of an orbiting DWL was made using a numerical instrument and atmospheres model developed for both Earth and Mars. The threshold aerosol backscatter for 2-micron was taken to be 1.0*10-6 msr-1. This backscatter value is between 1 and 2 orders of magnitude lower than that expected for clouds with optical depths greater than 2.0. Cloud composition was assumed to be mixture of dust, frozen CO2 and sulfuric acid. Based on the DWL assessment and simulation, it is reasonable to expect vertical profiles of the 3D wind speed with 1 km vertical resolution and horizontal spacing of 25 km to several 100 kms depending upon the desired integration times. These profiles would begin somewhere just below the tops of the highest clouds and extend into the overlying haze layer to some TBD height. Getting multiple layers of cloud returns is also possible with no negative impact on velocity measurement accuracy. With support from the NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed 2-micron coherent Doppler lidar system for wind measurement in the Earth’s atmosphere [1-3]. The knowledge and expertise for developing coherent Doppler wind lidar technologies and techniques for Earth related mission at NASA LaRC is being leveraged to develop an appropriate system suitable for wind measurement around Venus. We are considering a fiber laser based lidar system of high efficiency and smaller size and advancing the technology level to meet the requirements for DWL system for Venus from

  4. High Power Laser Diode Arrays for 2-Micron Solid State Coherent Lidars Applications

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron; Kavaya, Michael J.; Singh, Upendra; Sudesh, Vikas; Baker, Nathaniel

    2003-01-01

    Laser diode arrays are critical components of any diode-pumped solid state laser systems, constraining their performance and reliability. Laser diode arrays (LDAs) are used as the pump source for energizing the solid state lasing media to generate an intense coherent laser beam with a high spatial and spectral quality. The solid state laser design and the characteristics of its lasing materials define the operating wavelength, pulse duration, and power of the laser diodes. The pump requirements for high pulse energy 2-micron solid state lasers are substantially different from those of more widely used 1-micron lasers and in many aspects more challenging [1]. Furthermore, the reliability and lifetime demanded by many coherent lidar applications, such as global wind profiling from space and long-range clear air turbulence detection from aircraft, are beyond the capability of currently available LDAs. In addition to the need for more reliable LDAs with longer lifetime, further improvement in the operational parameters of high power quasi-cw LDAs, such as electrical efficiency, brightness, and duty cycle, are also necessary for developing cost-effective 2-micron coherent lidar systems for applications that impose stringent size, heat dissipation, and power constraints. Global wind sounding from space is one of such applications, which is the main driver for this work as part of NASA s Laser Risk Reduction Program. This paper discusses the current state of the 792 nm LDA technology and the technology areas being pursued toward improving their performance. The design and development of a unique characterization facility for addressing the specific issues associated with the LDAs for pumping 2-micron coherent lidar transmitters and identifying areas of technological improvement will be described. Finally, the results of measurements to date on various standard laser diode packages, as well as custom-designed packages with potentially longer lifetime, will be reported.

  5. Observations of Wind Profile of Marine Atmosphere Boundary Layer by Shipborne Coherent Doppler Lidar

    NASA Astrophysics Data System (ADS)

    Wu, Songhua; Yin, Jiaping; Liu, Bingyi; Liu, Jintao; Zhang, Hongwei; Song, Xiaoquan; Zhang, Kailin

    2016-06-01

    Pulsed Coherent Doppler Lidar (CDL) system is so good as to prove the feasibility of the marine atmosphere boundary layer detection. A ship-mounted Coherent Doppler lidar was used to measure the wind profile and vertical velocity in the boundary layer over the Yellow sea in 2014. Furthermore, for the purpose of reducing the impact of vibration during movement and correcting the LOS velocity, the paper introduces the attitude correction algorithm and comparison results.

  6. Coherent Doppler Lidar for Boundary Layer Studies and Wind Energy

    NASA Astrophysics Data System (ADS)

    Choukulkar, Aditya

    This thesis outlines the development of a vector retrieval technique, based on data assimilation, for a coherent Doppler LIDAR (Light Detection and Ranging). A detailed analysis of the Optimal Interpolation (OI) technique for vector retrieval is presented. Through several modifications to the OI technique, it is shown that the modified technique results in significant improvement in velocity retrieval accuracy. These modifications include changes to innovation covariance portioning, covariance binning, and analysis increment calculation. It is observed that the modified technique is able to make retrievals with better accuracy, preserves local information better, and compares well with tower measurements. In order to study the error of representativeness and vector retrieval error, a lidar simulator was constructed. Using the lidar simulator a thorough sensitivity analysis of the lidar measurement process and vector retrieval is carried out. The error of representativeness as a function of scales of motion and sensitivity of vector retrieval to look angle is quantified. Using the modified OI technique, study of nocturnal flow in Owens' Valley, CA was carried out to identify and understand uncharacteristic events on the night of March 27th 2006. Observations from 1030 UTC to 1230 UTC (0230 hr local time to 0430 hr local time) on March 27 2006 are presented. Lidar observations show complex and uncharacteristic flows such as sudden bursts of westerly cross-valley wind mixing with the dominant up-valley wind. Model results from Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS RTM) and other in-situ instrumentations are used to corroborate and complement these observations. The modified OI technique is used to identify uncharacteristic and extreme flow events at a wind development site. Estimates of turbulence and shear from this technique are compared to tower measurements. A formulation for equivalent wind speed in the presence of variations in wind speed

  7. Coherent laser radar at 1.06 micron using Nd:YAG lasers

    NASA Technical Reports Server (NTRS)

    Kane, Thomas J.; Kozlovsky, W. J.; Byer, Robert L.; Byvik, Charles E.

    1987-01-01

    A coherent laser radar system operating at the 1.06 micron Nd:YAG laser wavelength has been built and operated. A laser-diode-pumped monolithic ring laser served as the master oscillator. A single flash-lamp-pumped zigzag slab amplified the oscillator output to a power of 2.3 kW. Single-mode optical fiber was used to collect and mix the return signal with the local-oscillator output. Signals from clouds at a range of 2.7 km and from atmospheric aerosols at a range of 600 m were detected.

  8. Intraluminal fiber-optic Doppler imaging catheter for structural and functional optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Li, Xingde; Ko, Tony H.; Fujimoto, James G.

    2001-12-01

    We describe a miniature fiber-optic Doppler imaging catheter for integrated functional and structural optical coherence tomography (OCT) imaging. The Doppler catheter can map blood flow within a vessel as well as image vessel wall structures. A prototype Doppler catheter has been developed and demonstrated for measuring the intraluminal velocity profile in a vessel phantom (conduit). A simple mathematical model is demonstrated to estimate the total flow rate. This estimation technique also enables the spatial range of flow measurements to be extended by approximately two times the normal OCT image-penetration depth. The Doppler OCT catheter could be a powerful device for cardiovascular imaging.

  9. Momentum and heat flux estimation in the planetary boundary layer (PBL) with a 10.6-micron Doppler lidar

    NASA Technical Reports Server (NTRS)

    Gal-Chen, Tzvi; Xu, Mei; Eberhard, Wynn

    1991-01-01

    The mean wind, its standard deviation, and the momentum fluxes in the PBL are estimated with a 10.6-micron Doppler lidar. Spectral analysis of the radial velocities was performed, from which, by examining the amplitude of the power spectrum at the inertial range, the kinetic energy dissipation was deduced. The statistical form of the Navier-Stokes equations was used to derive the surface heat flux as the residual balance between the vertical gradient of the third moment of the vertical velocity and the kinetic energy dissipation.

  10. Noninvasive vascular imaging of ruptured retinal arterial macroaneurysms by Doppler optical coherence tomography.

    PubMed

    Miura, Masahiro; Muramatsu, Daisuke; Hong, Young-Joo; Yasuno, Yoshiaki; Itami, Ayako; Iwasaki, Takuya; Goto, Hiroshi

    2015-07-22

    To describe Doppler optical coherence tomography (OCT) imaging of ruptured retinal arterial macroaneurysms (RAMs). Four eyes of four patients with ruptured RAMs were prospectively studied. Vascular imaging was obtained using swept-source Doppler OCT, and compared with indocyanine green angiography images. En face projection of Doppler OCT images clearly showed RAMs at the corresponding locations of lesions in the indocyanine green angiography images. In Doppler OCT images, RAMs were located in the inner retina in three eyes and in the medium layer of the retina in one eye. In one eye, detection of RAMs by standard OCT was difficult because of the presence of inner retinal hemorrhage. In one eye, disappearance of blood flow after direct laser photocoagulation could be confirmed by Doppler OCT images. Doppler OCT imaging may potentially function as a noninvasive complementary procedure with indocyanine green angiography.

  11. Noninvasive vascular imaging of polypoidal choroidal vasculopathy by Doppler optical coherence tomography.

    PubMed

    Miura, Masahiro; Muramatsu, Daisuke; Hong, Young-Joo; Yasuno, Yoshiaki; Iwasaki, Takuya; Goto, Hiroshi

    2015-05-01

    To noninvasively investigate the vascular architecture of polypoidal lesions in polypoidal choroidal vasculopathy (PCV) using Doppler optical coherence tomography (OCT), and to evaluate the clinical usefulness of Doppler OCT for the assessment of therapeutic effects in PCV. Fifteen eyes of 15 patients with treatment-naïve PCV were prospectively studied. Vascular imaging was obtained using 1060-nm swept-source Doppler OCT, and compared with indocyanine green angiography (ICGA) images. The therapeutic effect of three consecutive intravitreal aflibercept injections was evaluated with ICGA and Doppler OCT. In Doppler OCT images, polypoidal lesions were clearly detected at the corresponding locations of lesions in the ICGA images. By being insensitive to dye leakage, Doppler OCT identified the complicated vascular structure in the polypoidal lesions. The identified mean area of the polypoidal lesions in the Doppler OCT images (0.04 mm(2)) was significantly smaller than that of the ICGA images (0.13 mm(2)). Polypoidal lesions were located in the retinal pigment epithelial detachment in 13 eyes, in the choroid in one eye, and in both the retinal pigment epithelial detachment and choroid in one eye. After intravitreal aflibercept treatment, areas of polypoidal lesions in the ICGA images were decreased in 14 of 15 eyes. This therapeutic effect was clearly confirmed in the Doppler OCT images. Doppler OCT imaging clearly detected fine vascular structures at the polypoidal lesions in PCV. Doppler OCT might be useful for the diagnosis and evaluation of therapeutic effects in PCV.

  12. Doppler optical coherence microscopy and tomography applied to inner ear mechanics

    SciTech Connect

    Page, Scott; Freeman, Dennis M.; Ghaffari, Roozbeh

    2015-12-31

    While it is clear that cochlear traveling waves underlie the extraordinary sensitivity, frequency selectivity, and dynamic range of mammalian hearing, the underlying micromechanical mechanisms remain unresolved. Recent advances in low coherence measurement techniques show promise over traditional laser Doppler vibrometry and video microscopy, which are limited by low reflectivities of cochlear structures and restricted optical access. Doppler optical coherence tomography (DOCT) and Doppler optical coherence microscopy (DOCM) both utilize a broadband source to limit constructive interference of scattered light to a small axial depth called a coherence gate. The coherence gate can be swept axially to image and measure sub-nanometer motions of cochlear structures throughout the cochlear partition. The coherence gate of DOCT is generally narrower than the confocal gate of the focusing optics, enabling increased axial resolution (typically 15 μm) within optical sections of the cochlear partition. DOCM, frequently implemented in the time domain, centers the coherence gate on the focal plane, achieving enhanced lateral and axial resolution when the confocal gate is narrower than the coherence gate. We compare these two complementary systems and demonstrate their utility in studying cellular and micromechanical mechanisms involved in mammalian hearing.

  13. Design of Control Software for a High-Speed Coherent Doppler Lidar System for CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Vanvalkenburg, Randal L.; Beyon, Jeffrey Y.; Koch, Grady J.; Yu, Jirong; Singh, Upendra N.; Kavaya, Michael J.

    2010-01-01

    The design of the software for a 2-micron coherent high-speed Doppler lidar system for CO2 measurement at NASA Langley Research Center is discussed in this paper. The specific strategy and design topology to meet the requirements of the system are reviewed. In order to attain the high-speed digitization of the different types of signals to be sampled on multiple channels, a carefully planned design of the control software is imperative. Samples of digitized data from each channel and their roles in data analysis post processing are also presented. Several challenges of extremely-fast, high volume data acquisition are discussed. The software must check the validity of each lidar return as well as other monitoring channel data in real-time. For such high-speed data acquisition systems, the software is a key component that enables the entire scope of CO2 measurement studies using commercially available system components.

  14. Pulsed Compression for Aerosol Ranging with Coherent Pulse-Doppler Lidar Systems

    DTIC Science & Technology

    1990-12-01

    as well as conventional Doppler radar hard-target applications. Accord- ing to Menzies and Hardesty , the accuracy of Doppler lidar velocity...density expressed in Equation (80). As Hardesty and Menzies explain, if a lidar of a single carrier frequency f illuminates a volume of dense, randomly...ham, WA: SPIE, 1988. 14. Hardesty , Michael R. Measurement of Range-Resolved Water Vapor Concentra- tion by Coherent C0 2 Differential Absorption Lidar

  15. Intraluminal fiber-optic Doppler imaging catheter for structural and functional optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Li, Xing D.; Ko, Tony H.; Fujimoto, James G.

    2002-06-01

    A miniature fiber Doppler imaging catheter for integrated functional and structural optical coherence tomography (OCT) imaging has been developed. The Doppler catheter can be used to map blood flow profile within a vessel as well as image vessel wall structures. The prototype Doppler catheter was demonstrated in measuring the intraluminal velocity profile in a vessel phantom (conduit). A simple mathematical model can be used to estimate the flow profile outside of normal OCT beam penetration. By extending the spatial range of the flow measurements to approximately two times the normal OCT image penetration depth, the total flow rate can then be calculated from the estimated velocity profiles. The measured total flow rate in the vessel phantom obtained from the Doppler imaging catheter correlates well with the calibrated flow values. The Doppler OCT catheter's ability to simultaneously obtain both structural and functional information makes it a potentially powerful device of cardiovascular imaging.

  16. Gold Nanorods as a Contrast Agent for Doppler Optical Coherence Tomography

    PubMed Central

    Wang, Bo; Kagemann, Larry; Schuman, Joel S.; Ishikawa, Hiroshi; Bilonick, Richard A.; Ling, Yun; Sigal, Ian A.; Nadler, Zach; Francis, Andrew; Sandrian, Michelle G.; Wollstein, Gadi

    2014-01-01

    Purpose To investigate gold nanorods (GNRs) as a contrast agent to enhance Doppler optical coherence tomography (OCT) imaging of the intrascleral aqueous humor outflow. Methods A serial dilution of GNRs was scanned with a spectral-domain OCT device (Bioptigen, Durham, NC) to visualize Doppler signal. Doppler measurements using GNRs were validated using a controlled flow system. To demonstrate an application of GNR enhanced Doppler, porcine eyes were perfused at constant pressure with mock aqueous alone or 1.0×1012 GNR/mL mixed with mock aqueous. Twelve Doppler and volumetric SD-OCT scans were obtained from the limbus in a radial fashion incremented by 30°, forming a circular scan pattern. Volumetric flow was computed by integrating flow inside non-connected vessels throughout all 12 scans around the limbus. Results At the GNR concentration of 0.7×1012 GNRs/mL, Doppler signal was present through the entire depth of the testing tube without substantial attenuation. A well-defined laminar flow profile was observed for Doppler images of GNRs flowing through the glass capillary tube. The Doppler OCT measured flow profile was not statistically different from the expected flow profile based upon an autoregressive moving average model, with an error of −0.025 to 0.037 mm/s (p = 0.6435). Cross-sectional slices demonstrated the ability to view anterior chamber outflow ex-vivo using GNR-enhanced Doppler OCT. Doppler volumetric flow measurements were comparable to flow recorded by the perfusion system. Conclusions GNRs created a measureable Doppler signal within otherwise silent flow fields in OCT Doppler scans. Practical application of this technique was confirmed in a constant pressure ex-vivo aqueous humor outflow model in porcine eyes. PMID:24595044

  17. Combined 2-micron Dial and Doppler Lidar: Application to the Atmosphere of Earth or Mars

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Koch, Grady J.; Ismail, Syed; Kavaya, Michael; Yu, Jirong; Wood, Sidney A.; Emmitt, G. David

    2006-01-01

    A concept is explored for combining the Doppler and DIAL techniques into a single, multifunctional instrument. Wind, CO2 concentration, and aerosol density can all be measured. Technology to build this instrument is described, including the demonstration of a prototype lidar. Applications are described for use in the Earth science. The atmosphere of Mars can also be studied, and results from a recently-developed simulation model of performance in the Martian atmosphere are presented.

  18. Coherent summation of spatially distorted Doppler lidar signals using a two-dimensional heterodyne detector array

    NASA Technical Reports Server (NTRS)

    Chan, Kin Pui; Killinger, Dennis K.

    1992-01-01

    We have investigated the improvement in the signal-to-noise ratio for a coherent Doppler lidar through the use of a multi-element heterodyne detector array. Such an array enables the spatial summation of atmospheric refractive turbulence induced speckles, and time varying target speckles. Our recent experiments have shown that the non-coherent summation of the lidar signals from a heterodyne detector array can enhance the heterodyne mixing efficiency and thus the signal-to-noise ratio. In this paper, we expand this work to include the coherent summation of array signals. The digitized heterodyne signals were stored in a personal computer. Fast Fourier transforms were performed on both the non-coherent and coherent summations of the detector array signals. It was found that the coherent summation greatly enhanced the accuracy in the Doppler frequency estimate. A theoretical analysis was performed and indicated good agreement with experimental results. We have also applied these results to the more general lidar applications including atmospheric wind sensing, and have found that in most lidar applications the Doppler frequency estimate is increased through the use of the heterodyne detector array.

  19. Coherent summation of spatially distorted laser Doppler signals by using a two-dimensional heterodyne detector array

    NASA Technical Reports Server (NTRS)

    Chan, Kin P.; Killinger, Dennis K.

    1992-01-01

    Phase-sensitive coherent summation of individual heterodyne detector array signals was demonstrated for the enhanced detection of spatially distorted laser Doppler returns. With the use of a 2 x 2 heterodyne detector array, the phase and amplitude of a time-varying speckle pattern was detected, and the signal-to-noise ratio of the Doppler shift estimate was shown to be improved by a factor of 2, depending on the extent of spatial coherence loss. These results are shown to agree with a first-order analysis and indicate the advantage of coherent summation for both short-range laser Doppler velocimetry and long-range atmospheric coherent lidar.

  20. Very low-phase noise, coherent 94GHz radar for micro-Doppler and vibrometry studies

    NASA Astrophysics Data System (ADS)

    Robertson, Duncan A.; Brooker, Graham M.; Beasley, Patrick D. L.

    2014-05-01

    Micro-Doppler and vibrometry measurements require coherent radars with low phase noise. We report the development of a novel, very low phase noise 94 GHz radar, called T-220, which offers superior performance for micro-Doppler and vibrometry studies compared with our previous work. The radar uses a combination of direct digital synthesis (DDS) chirp generation, frequency upconversion and frequency multiplication to yield very low phase noise and rapid, contiguous chirps, necessary for Doppler studies and other coherent processing applications. Dual fan beam antennas are used to achieve negligible transmit-receive leakage, with fine azimuth resolution and modest elevation coverage. The resulting PPI imagery is very high fidelity with little or no evidence of phase noise effects.

  1. Heterodyne Doppler 1-micron lidar measurement of reduced effective telescope aperture due to atmospheric turbulence

    NASA Technical Reports Server (NTRS)

    Chan, Kin Pui; Killinger, Dennis K.; Sugimoto, Nobuo

    1991-01-01

    A pulsed Nd:YAG bistatic focused-beam lidar allowing simultaneous heterodyne and direct detection of the same lidar returns has been experimentally employed to ascertain the effect of atmospheric turbulence on heterodyne and direct-detection lidar at 1 micron, by measuring the average carrier-to-noise ratio and statistical fluctuation level in the return signals under various experimental and atmospheric conditions. Atmospheric turbulence is found capable of reducing the lidar receiver's effective telescope aperture and heterodyne detection efficiency. This observed effective-aperture limitation functionally resembles predictions based on the Clifford and Wandzura (1981) heterodyne wavefront detection theory.

  2. The effects of wavelength on coherent Doppler lidar performance

    NASA Technical Reports Server (NTRS)

    Lawrence, T. R.

    1985-01-01

    Hitherto, long-range wind-sensing coherent (heterodyne) lidars have utilized CO2 lasers (operating at a 10-micrometer wavelength) since these were the only high-power single-mode (spatial and axial) pulsed sources available. This property ensures temporal coherence over the required spatial resolution, e.g., the pulse length. Recent developments in Nd:YAG lasers makes possible the consideration of a 1.06-micrometer source (Kane et al., 1984). The relative merit of operation at various wavelengths is a function of system parameter, backscattering cross section, signal processing, beam propagation, and practical and eye safety considerations. These factors are discussed in the context of a global wind-sensing coherent lidar.

  3. A compact high repetition rate CO2 coherent Doppler lidar

    NASA Technical Reports Server (NTRS)

    Alejandro, S.; Frelin, R.; Dix, B.; Mcnicholl, P.

    1992-01-01

    As part of its program to develop coherent heterodyne detection lidar technology for space, airborne, and ground based applications, the Optical Environment Division of the USAF's Phillips Laboratory developed a compact coherent CO2 TEA lidar system. Although originally conceived as a high altitude balloon borne system, the lidar is presently integrated into a trailer for ground based field measurements of aerosols and wind fields. In this role, it will also serve as a testbed for signal acquisition and processing development for planned future airborne and space based solid state lidar systems. The system has also found significance in new areas of interest to the Air Force such as cloud studies and coherent Differential Absorption Lidar (DIAL) systems.

  4. A compact high repetition rate CO2 coherent Doppler lidar

    NASA Technical Reports Server (NTRS)

    Alejandro, S.; Frelin, R.; Dix, B.; Mcnicholl, P.

    1992-01-01

    As part of its program to develop coherent heterodyne detection lidar technology for space, airborne, and ground based applications, the Optical Environment Division of the USAF's Phillips Laboratory developed a compact coherent CO2 TEA lidar system. Although originally conceived as a high altitude balloon borne system, the lidar is presently integrated into a trailer for ground based field measurements of aerosols and wind fields. In this role, it will also serve as a testbed for signal acquisition and processing development for planned future airborne and space based solid state lidar systems. The system has also found significance in new areas of interest to the Air Force such as cloud studies and coherent Differential Absorption Lidar (DIAL) systems.

  5. The effects of wavelength on coherent Doppler lidar performance

    NASA Technical Reports Server (NTRS)

    Lawrence, T. R.

    1985-01-01

    Hitherto, long-range wind-sensing coherent (heterodyne) lidars have utilized CO2 lasers (operating at a 10-micrometer wavelength) since these were the only high-power single-mode (spatial and axial) pulsed sources available. This property ensures temporal coherence over the required spatial resolution, e.g., the pulse length. Recent developments in Nd:YAG lasers makes possible the consideration of a 1.06-micrometer source (Kane et al., 1984). The relative merit of operation at various wavelengths is a function of system parameter, backscattering cross section, signal processing, beam propagation, and practical and eye safety considerations. These factors are discussed in the context of a global wind-sensing coherent lidar.

  6. Flux estimation of the FIFE planetary boundary layer (PBL) with 10.6 micron Doppler lidar

    NASA Technical Reports Server (NTRS)

    Gal-Chen, Tzvi; Xu, Mei; Eberhard, Wynn

    1990-01-01

    A method is devised for calculating wind, momentum, and other flux parameters that characterize the planetary boundary layer (PBL) and thereby facilitate the calibration of spaceborne vs. in situ flux estimates. Single Doppler lidar data are used to estimate the variance of the mean wind and the covariance related to the vertically pointing fluxes of horizontal momentum. The skewness of the vertical velocity and the range of kinetic energy dissipation are also estimated, and the surface heat flux is determined by means of a statistical Navier-Stokes equation. The conclusion shows that the PBL structure combines both 'bottom-up' and 'top-down' processes suggesting that the relevant parameters for the atmospheric boundary layer be revised. The conclusions are of significant interest to the modeling techniques used in General Circulation Models as well as to flux estimation.

  7. High Repetition Rate Pulsed 2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Uprendra N.; Bai, Yingxin; Yu, Jirong; Petros, Mulugeta; Petzar, Paul J.; Trieu, Bo C.; Lee, Hyung

    2009-01-01

    A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed at NASA Langley Research Center. Such a laser transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of approximately 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. The measured standard deviation of the laser frequency jitter is about 3 MHz.

  8. Radiation damage in a micron-sized protein crystal studied via reciprocal space mapping and Bragg coherent diffractive imaging

    DOE PAGES

    Coughlan, H. D.; Darmanin, C.; Phillips, N. W.; ...

    2015-04-29

    For laboratory and synchrotron based X-ray sources, radiation damage has posed a significant barrier to obtaining high-resolution structural data from biological macromolecules. The problem is particularly acute for micron-sized crystals where the weaker signal often necessitates the use of higher intensity beams to obtain the relevant data. Here, we employ a combination of techniques, including Bragg coherent diffractive imaging to characterise the radiation induced damage in a micron-sized protein crystal over time. The approach we adopt here could help screen for potential protein crystal candidates for measurement at X-ray free election laser sources.

  9. Radiation damage in a micron-sized protein crystal studied via reciprocal space mapping and Bragg coherent diffractive imaging

    PubMed Central

    Coughlan, H. D.; Darmanin, C.; Phillips, N. W.; Hofmann, F.; Clark, J. N.; Harder, R. J.; Vine, D. J.; Abbey, B.

    2015-01-01

    For laboratory and synchrotron based X-ray sources, radiation damage has posed a significant barrier to obtaining high-resolution structural data from biological macromolecules. The problem is particularly acute for micron-sized crystals where the weaker signal often necessitates the use of higher intensity beams to obtain the relevant data. Here, we employ a combination of techniques, including Bragg coherent diffractive imaging to characterise the radiation induced damage in a micron-sized protein crystal over time. The approach we adopt here could help screen for potential protein crystal candidates for measurement at X-ray free election laser sources. PMID:26798804

  10. Stokes-Doppler coherence imaging for ITER boundary tomography

    NASA Astrophysics Data System (ADS)

    Howard, J.; Kocan, M.; Lisgo, S.; Reichle, R.

    2016-11-01

    An optical coherence imaging system is presently being designed for impurity transport studies and other applications on ITER. The wide variation in magnetic field strength and pitch angle (assumed known) across the field of view generates additional Zeeman-polarization-weighting information that can improve the reliability of tomographic reconstructions. Because background reflected light will be somewhat depolarized analysis of only the polarized fraction may be enough to provide a level of background suppression. We present the principles behind these ideas and some simulations that demonstrate how the approach might work on ITER. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

  11. A study of atmospheric optical scattering parameters at 1.5 and 2 micron region for solid state Doppler lidar applications

    NASA Technical Reports Server (NTRS)

    Margalit, Eli; Amzajerdian, Farzin; Benoist, Rodney; Dubinsky, Richard

    1992-01-01

    The increasing interest in the development of an eye-safe, solid state, Doppler lidar for avionic applications has created the need for a quantitative evaluation of atmospheric effects on performance. Theoretical calculations were completed for optical scattering parameters to be compared with the field measurements. Computer codes were developed for the required calculations and designed to be interactive and user friendly in order to support comparison with experimental results and, thus, provide the basis for evaluation of eye-safe Doppler lidar over a wide range of atmospheric conditions and geographical locations. A holmium Doppler lidar operating at 2.09 microns was constructed for atmospheric backscattering, attenuation, and wind velocity measurements. Theoretical calculations and field studies were performed for backscatter coefficients. The selected wavelengths correspond to Er:glass, Tm:YAG, and Tm,Ho:YAG solid state lasers that are suitable for use in an eye-safe Doppler lidar system.

  12. Sub-micron resolution high-speed spectral domain optical coherence tomography in quality inspection for printed electronics

    NASA Astrophysics Data System (ADS)

    Czajkowski, J.; Lauri, J.; Sliz, R.; Fält, P.; Fabritius, T.; Myllylä, R.; Cense, B.

    2012-04-01

    We present the use of sub-micron resolution optical coherence tomography (OCT) in quality inspection for printed electronics. The device used in the study is based on a supercontinuum light source, Michelson interferometer and high-speed spectrometer. The spectrometer in the presented spectral-domain optical coherence tomography setup (SD-OCT) is centered at 600 nm and covers a 400 nm wide spectral region ranging from 400 nm to 800 nm. Spectra were acquired at a continuous rate of 140,000 per second. The full width at half maximum of the point spread function obtained from a Parylene C sample was 0:98 m. In addition to Parylene C layers, the applicability of sub-micron SD-OCT in printed electronics was studied using PET and epoxy covered solar cell, a printed RFID antenna and a screen-printed battery electrode. A commercial SD-OCT system was used for reference measurements.

  13. Detection on micro-Doppler effect based on 1550 nm laser coherent radar

    NASA Astrophysics Data System (ADS)

    Jun, Zhang; Yang, Sun; Zenghui, Cao; Tengfei, Sun; Tiantian, Zheng

    2014-01-01

    A laser coherent detection system of 1550 nm wavelength was presented, and experimental research on detecting micro-Doppler effect in a dynamic target was developed. In this paper, the return signal in the time domain is decomposed into a set of components in different wavelet-scales by multi-resolution analysis, and the components are associated with the vibrational motions in a target. The micro-Doppler signatures are extracted by applying the reconstruction (inverse wavelet transform). During the course of the final data processing frequency analysis and time-frequency analysis are applied to analyze the vibrational signals and estimate the motion parameters successfully. The experimental results indicate that the micro-Doppler information in a moving can be effectively detected, and tiny vibrational signatures also can be acquired effectively by wavelet multi-resolution analysis and time-frequency analysis.

  14. Influence of laser coherence on reference-matched laser Doppler velocimetry.

    PubMed

    Beuth, Thorsten; Fox, Maik; Stork, Wilhelm

    2016-03-10

    The probe length is investigated under the influence of the coherence length of Gaussian and Lorentzian spectra for the case that the focal point and the point of highest interference are matched in a strongly focused laser Doppler velocimetry setup (LDV). Isosurfaces of a -3  dB drop of the intensity maximum are estimated and suggested as an alternative, comprehensible way to define probe volumes. In the end, the equations are applied for an exemplary lidar setup to show the reduction of requirements for the coherence length of the laser source in comparison to unmatched cases.

  15. Method and system to measure temperature of gases using coherent anti-stokes doppler spectroscopy

    DOEpatents

    Rhodes, Mark

    2013-12-17

    A method of measuring a temperature of a noble gas in a chamber includes providing the noble gas in the chamber. The noble gas is characterized by a pressure and a temperature. The method also includes directing a first laser beam into the chamber and directing a second laser beam into the chamber. The first laser beam is characterized by a first frequency and the second laser beam is characterized by a second frequency. The method further includes converting at least a portion of the first laser beam and the second laser beam into a coherent anti-Stokes beam, measuring a Doppler broadening of the coherent anti-Stokes beam, and computing the temperature using the Doppler broadening.

  16. Detection of the Aircraft Vortex Wake with the Aid of a Coherent Doppler Lidar

    NASA Astrophysics Data System (ADS)

    Penkin, M. S.; Boreisho, A. S.; Konyaev, M. A.; Orlov, A. E.; Baranov, N. A.

    2017-07-01

    The results of the first measurements in Russia of the vortex wakes left by different types of airplanes with the aid of 1.5-μm range home-made commercially manufactured coherent Doppler lidars are presented. The characteristic features of the measurement of vortex wakes by such lidars are considered. The dynamics of the vortex wake left by a Boeing 737-800 is shown.

  17. Wind sensing in an atmospheric boundary layer by means of micropulse coherent Doppler lidars

    NASA Astrophysics Data System (ADS)

    Banakh, V. A.; Smalikho, I. N.

    2016-07-01

    An algorithm is developed and computer simulation of wind sensing by means of micropulse coherent Doppler lidars (CDLs) in the atmospheric boundary layer is conducted for low values of the signalto- noise (SNR) ratio. The accuracy of lidar wind measurements is studied numerically for parameters of micropulse Stream Line CDLs. Optimal parameters of the measurements and processing data obtained at low SNR, which allow reconstructing vertical profiles of the wind velocity vector with required accuracy within an entire atmospheric boundary layer, are determined.

  18. Large-Eddy Simulation-Based Retrieval of Dissipation from Coherent Doppler Lidar Data

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, Raghavendra; Calhoun, Ronald; Fernando, Harindra

    2010-07-01

    Accurate estimation of dissipation rate is important in understanding and analyzing turbulent flows found in environment and engineering processes. Many previous studies have focused on measuring the local dissipation rate at a single point or averaged dissipation rate over a suitable area. Since coherent Doppler lidar is capable of providing multi-point measurements covering a large spatial extent, it is well-suited for examining the distribution of dissipation in the atmosphere. In this paper, an approach is presented that is based on retrieving the dissipation rate from coherent Doppler lidar data using large-eddy simulation. Two Coherent Doppler lidars performed range height indicator (RHI) scans of a vertical/cross-barrier plane during the Terrain-induced Rotor Experiment (T-REX). Two-dimensional velocity vectors were retrieved using a least squares method. The velocity vectors retrieved from co-planar RHI scans are used to estimate subgrid scale (SGS) quantities through a known SGS parameterization. For the T-REX datasets analyzed, the dissipation rate was found to increase in the presence of rotors, subrotors, and, as expected, in regions of high wind shear. Owing to the presence of sharper gradients in subrotors, their dissipation rate is generally larger than that of rotors.

  19. Real-time bulk-motion-correction free Doppler variance optical coherence tomography for choroidal capillary vasculature imaging

    PubMed Central

    Liu, Gangjun; Qi, Wenjuan; Yu, Lingfeng; Chen, Zhongping

    2011-01-01

    In this paper, we analyze the retinal and choroidal blood vasculature in the posterior segment of the human eye with optimized color Doppler and Doppler variance optical coherence tomography. Depth-resolved structure, color Doppler and Doppler variance images are compared. Blood vessels down to the capillary level were detected and visualized with the optimized optical coherence color Doppler and Doppler variance method. For in-vivo imaging of human eyes, bulk-motion induced bulk phase must be identified and removed before using the color Doppler method. It was found that the Doppler variance method is not sensitive to bulk-motion and the method can be used without correcting the bulk-motion when the sample-movement-induced velocity changes gradually. Real-time processing and displaying of the structure and blood vessel images are very interesting and is demonstrated using a dual quad-core Central Processing Unit (CPU) workstation. High resolution images of choroidal capillary of the vasculature network with phased-resolved color Doppler and Doppler variance are shown. PMID:21369191

  20. Coherent 1-micron lidar measurements of atmospheric-turbulence-induced spatial decorrelation using a multielement heterodyne detector array

    NASA Technical Reports Server (NTRS)

    Chan, Kin P.; Killinger, Dennis K.

    1992-01-01

    A coherent 1-micron Nd:YAG lidar system is employed to measure directly the reduced spatial coherence length rho 0 of the lidar returns caused by atmospheric turbulence. The experiments were conducted by using a 2 x 2 heterodyne detector array, which permitted real-time spatial correlation measurements of the lidar returns at two different detector spacings. The spatial correlation coefficients and spatial coherence length of the lidar returns from a hard target were measured during a day-to-night time period when the atmospheric turbulence parameter, Cn-squared, was measured to vary from 2 x 10 exp -13 to 2 x 10 exp -4 m exp -2/3. These directly measured values of rho 0 as a function of Cn-squared were found to be in good agreement with theoretical predictions.

  1. Microvascular anastomosis guidance and evaluation using real-time three-dimensional Fourier-domain Doppler optical coherence tomography

    PubMed Central

    Ibrahim, Zuhaib; Tong, Dedi; Zhu, Shan; Mao, Qi; Pang, John; Andrew Lee, Wei Ping; Brandacher, Gerald; Kang, Jin U.

    2013-01-01

    Abstract. Vascular and microvascular anastomoses are critical components of reconstructive microsurgery, vascular surgery, and transplant surgery. Intraoperative surgical guidance using a surgical imaging modality that provides an in-depth view and three-dimensional (3-D) imaging can potentially improve outcome following both conventional and innovative anastomosis techniques. Objective postoperative imaging of the anastomosed vessel can potentially improve the salvage rate when combined with other clinical assessment tools, such as capillary refill, temperature, blanching, and skin turgor. Compared to other contemporary postoperative monitoring modalities—computed tomography angiograms, magnetic resonance (MR) angiograms, and ultrasound Doppler—optical coherence tomography (OCT) is a noninvasive high-resolution (micron-level), high-speed, 3-D imaging modality that has been adopted widely in biomedical and clinical applications. For the first time, to the best of our knowledge, the feasibility of real-time 3-D phase-resolved Doppler OCT (PRDOCT) as an assisted intra- and postoperative imaging modality for microvascular anastomosis of rodent femoral vessels is demonstrated, which will provide new insights and a potential breakthrough to microvascular and supermicrovascular surgery. PMID:23856833

  2. Coherent optical transients observed in rubidium atomic line filtered Doppler velocimetry experiments

    NASA Astrophysics Data System (ADS)

    Fajardo, Mario E.; Molek, Christopher D.; Vesely, Annamaria L.

    2015-10-01

    We report the first successful results from our novel Rubidium Atomic Line Filtered (RALF) Doppler velocimetry apparatus, along with unanticipated oscillatory signals due to coherent optical transients generated within pure Rb vapor cells. RALF is a high-velocity and high-acceleration extension of the well-known Doppler Global Velocimetry (DGV) technique for constructing multi-dimensional flow velocity vector maps in aerodynamics experiments [H. Komine, U.S. Patent No. 4,919,536 (24 April 1990)]. RALF exploits the frequency dependence of pressure-broadened Rb atom optical absorptions in a heated Rb/N2 gas cell to encode the Doppler shift of reflected near-resonant (λ0 ≈ 780.24 nm) laser light onto the intensity transmitted by the cell. The present RALF apparatus combines fiber optic and free-space components and was built to determine suitable operating conditions and performance parameters for the Rb/N2 gas cells. It yields single-spot velocities of thin laser-driven-flyer test surfaces and incorporates a simultaneous Photonic Doppler Velocimetry (PDV) channel [Strand et al., Rev. Sci. Instrum. 77, 083108 (2006)] for validation of the RALF results, which we demonstrate here over the v = 0 to 1 km/s range. Both RALF and DGV presume the vapor cells to be simple Beer's Law optical absorbers, so we were quite surprised to observe oscillatory signals in experiments employing low pressure pure Rb vapor cells. We interpret these oscillations as interference between the Doppler shifted reflected light and the Free Induction Decay (FID) coherent optical transient produced within the pure Rb cells at the original laser frequency; this is confirmed by direct comparison of the PDV and FID signals. We attribute the different behaviors of the Rb/N2 vs. Rb gas cells to efficient dephasing of the atomic/optical coherences by Rb-N2 collisions. The minimum necessary N2 buffer gas density ≈0.3 amagat translates into a smallest useful velocity range of 0 to 2 km/s, which can

  3. Coherent optical transients observed in rubidium atomic line filtered Doppler velocimetry experiments

    SciTech Connect

    Fajardo, Mario E. Molek, Christopher D.; Vesely, Annamaria L.

    2015-10-14

    We report the first successful results from our novel Rubidium Atomic Line Filtered (RALF) Doppler velocimetry apparatus, along with unanticipated oscillatory signals due to coherent optical transients generated within pure Rb vapor cells. RALF is a high-velocity and high-acceleration extension of the well-known Doppler Global Velocimetry (DGV) technique for constructing multi-dimensional flow velocity vector maps in aerodynamics experiments [H. Komine, U.S. Patent No. 4,919,536 (24 April 1990)]. RALF exploits the frequency dependence of pressure-broadened Rb atom optical absorptions in a heated Rb/N{sub 2} gas cell to encode the Doppler shift of reflected near-resonant (λ{sub 0} ≈ 780.24 nm) laser light onto the intensity transmitted by the cell. The present RALF apparatus combines fiber optic and free-space components and was built to determine suitable operating conditions and performance parameters for the Rb/N{sub 2} gas cells. It yields single-spot velocities of thin laser-driven-flyer test surfaces and incorporates a simultaneous Photonic Doppler Velocimetry (PDV) channel [Strand et al., Rev. Sci. Instrum. 77, 083108 (2006)] for validation of the RALF results, which we demonstrate here over the v = 0 to 1 km/s range. Both RALF and DGV presume the vapor cells to be simple Beer's Law optical absorbers, so we were quite surprised to observe oscillatory signals in experiments employing low pressure pure Rb vapor cells. We interpret these oscillations as interference between the Doppler shifted reflected light and the Free Induction Decay (FID) coherent optical transient produced within the pure Rb cells at the original laser frequency; this is confirmed by direct comparison of the PDV and FID signals. We attribute the different behaviors of the Rb/N{sub 2} vs. Rb gas cells to efficient dephasing of the atomic/optical coherences by Rb-N{sub 2} collisions. The minimum necessary N{sub 2} buffer gas density ≈0.3 amagat translates into a smallest

  4. Improved Contrast-Enhanced Power Doppler Using a Coherence-Based Estimator.

    PubMed

    Tremblay-Darveau, Charles; Bar-Zion, Avinoam; Williams, Ross; Sheeran, Paul S; Milot, Laurent; Loupas, Thanasis; Adam, Dan; Bruce, Matthew; Burns, Peter N

    2017-09-01

    While plane-wave imaging can improve the performance of power Doppler by enabling much longer ensembles than systems using focused beams, the long-ensemble averaging of the zero-lag autocorrelation R(0) estimates does not directly decrease the mean noise level, but only decreases its variance. Spatial variation of the noise due to the time-gain compensation and the received beamforming aperture ultimately limits sensitivity. In this paper, we demonstrate that the performance of power Doppler imaging can be improved by leveraging the higher lags of the autocorrelation [e.g., R(1), R(2),…] instead of the signal power (R(0)). As noise is completely uncorrelated from pulse-to-pulse while the flow signal remains correlated significantly longer, weak signals just above the noise floor can be made visible through the reduction of the noise floor. Finally, as coherence decreases proportionally with respect to velocity, we demonstrate how signal coherence can be targeted to separate flows of different velocities. For instance, we show how long-time-range coherence of microbubble contrast-enhanced flow specifically isolates slow capillary perfusion (as opposed to conduit flow).

  5. Doppler cooling with coherent trains of laser pulses and a tunable velocity comb

    SciTech Connect

    Ilinova, Ekaterina; Ahmad, Mahmoud; Derevianko, Andrei

    2011-09-15

    We explore the possibility of decelerating and Doppler cooling an ensemble of two-level atoms by a coherent train of short, nonoverlapping laser pulses. We derive analytical expressions for mechanical force exerted by the train. In frequency space the force pattern reflects the underlying frequency comb structure. The pattern depends strongly on the ratio of the atomic lifetime to the repetition time between the pulses and pulse area. For example, in the limit of short lifetimes, the frequency-space peaks of the optical force wash out. We propose to tune the carrier-envelope offset frequency to follow the Doppler-shifted detuning as atoms decelerate; this leads to compression of atomic velocity distribution about comb teeth and results in a ''velocity comb''--a series of narrow equidistant peaks in the velocity space.

  6. High speed, wide velocity dynamic range Doppler optical coherence tomography (Part IV): split spectrum processing in rotary catheter probes.

    PubMed

    Vuong, Barry; Lee, Anthony M D; Luk, Timothy W H; Sun, Cuiru; Lam, Stephen; Lane, Pierre; Yang, Victor X D

    2014-04-07

    We report a technique for blood flow detection using split spectrum Doppler optical coherence tomography (ssDOCT) that shows improved sensitivity over existing Doppler OCT methods. In ssDOCT, the Doppler signal is averaged over multiple sub-bands of the interferogram, increasing the SNR of the Doppler signal. We explore the parameterization of this technique in terms of number of sub-band windows, width and overlap of the windows, and their effect on the Doppler signal to noise in a flow phantom. Compared to conventional DOCT, ssDOCT processing has increased flow sensitivity. We demonstrate the effectiveness of ssDOCT in-vivo for intravascular flow detection within a porcine carotid artery and for microvascular vessel detection in human pulmonary imaging, using rotary catheter probes. To our knowledge, this is the first report of visualizing in-vivo Doppler flow patterns adjacent to stent struts in the carotid artery.

  7. Demonstration of a low bandwidth 1.06-micron optical phase-locked loop for coherent homodyne communication

    NASA Technical Reports Server (NTRS)

    Day, T.; Farinas, A. D.; Byer, R. L.

    1990-01-01

    A type II 1.06-micron optical phase-locked loop (OPLL) for use in a coherent homodyne receiver is discussed. Diode-laser-pumped solid-state lasers are used for both the local oscillator and transmitter, because their phase noise is significantly lower than that of diode lasers. Closed-loop RMS phase noise of less than 12 mrad (0.69 deg) is achieved, and modulation-demodulation in bulk modulators at rates from 20 kHz to 20 MHz with less than 19 deg of modulation depth is demonstrated.

  8. Neural network analysis of pulp flow speed in low coherence Doppler flowmetry measurement

    NASA Astrophysics Data System (ADS)

    Hannula, Manne; Alarousu, Erkki; Prykäri, Tuukka; Myllylä, Risto

    2007-03-01

    Low Coherence Doppler Flowmetry (LCDF) measurement produces a signal, which frequency domain characteristics are in connection to the speed of the flow. In this study a LCDF measurement data of pulp flow in a capillary was analyzed with a simple Artificial Neural Network (ANN) method to estimate the flow speed. The accuracy of the method proved to be good, validation of the method resulted in absolute error of 14 +/- 11 percentage units (mean+/-std) in flow speed estimation. The results of the study can be utilized in development of industrial pulp flow speed measurement instruments.

  9. Coherent Doppler Lidar for Measuring Velocity and Altitude of Space and Arial Vehicles

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Pierrottet, Diego; Hines, Glenn D.; Petway, Larry; Barnes, Bruce W.

    2016-01-01

    A coherent Doppler lidar has been developed to support future NASA missions to planetary bodies. The lidar transmits three laser beams and measures line-of-sight range and velocity along each beam using a frequency modulated continuous wave (FMCW) technique. Accurate altitude and velocity vector data, derived from the line-of-sight measurements, enables the landing vehicle to precisely navigate from several kilometers above the ground to the designated location and execute a gentle touchdown. The same lidar sensor can also benefit terrestrial applications that cannot rely on GPS or require surface-relative altitude and velocity data.

  10. Complex flow characterisation of a porous tissue scaffold measured by Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Tomlins, Peter H.; Wang, Yiwei; Zhang, Bufa; Tedaldi, Matthew; Tomlins, Paul E.

    2008-02-01

    The flow of culture medium through a mechanically stimulated cell-seeded tissue scaffold is a factor influencing not only the transport of essential nutrients and waste product removal but also impacting on the degradation kinetics of the scaffold. Being able to map spatial and temporal changes in fluid flow behaviour is key to the development of improved bioreactors and tissue scaffold designs, especially for the new generation of multiple tissue reactors. In this paper we demonstrate the excellent metrological benefits of fast Doppler optical coherence tomography for time-lapse characterisation of tissue scaffolds placed in a dynamic flow environment.

  11. Doppler coherence imaging and tomography of flows in tokamak plasmas (invited)

    SciTech Connect

    Howard, J.; Diallo, A.; Creese, M.; Blackwell, B. D.; Allen, S. L.; Ellis, R. M.; Porter, G. D.; Meyer, W.; Fenstermacher, M. E.; Brooks, N. H.; Van Zeeland, M. E.; Boivin, R. L.

    2010-10-15

    This article describes the results of spatial heterodyne Doppler ''coherence imaging'' of carbon ion flows in the divertor region of the DIII-D tokamak. Spatially encoded interferometric projections of doubly ionized carbon emission at 465 nm have been demodulated and tomographically inverted to obtain the spatial distribution of the carbon ion parallel flow and emissivity. The operating principles of the new instruments are described, and the link between measured properties and line integrals of the flow field are established. An iterative simultaneous arithmetic reconstruction procedure is applied to invert the interferometric phase shift projections, and the reconstructed parallel flow field amplitudes are found to be in reasonable agreement with UEDGE modeling.

  12. Total retinal blood flow measurement by three beam Doppler optical coherence tomography

    PubMed Central

    Haindl, Richard; Trasischker, Wolfgang; Wartak, Andreas; Baumann, Bernhard; Pircher, Michael; Hitzenberger, Christoph K.

    2016-01-01

    We present measurements of total retinal blood flow in healthy volunteers using a three beam Doppler optical coherence tomography (D-OCT) technique. This technology has the advantage of a precise determination of the flow vector without the use of any a-priori information on the vessel geometry. Circular D-OCT scans around the optic disc were recorded and venous as well as arterial total blood flow was determined and compared for each subject. The reproducibility of the method was assessed in 6 subjects by repeated measurements. Only small deviations of around 6% between the measurements were found which indicates the high precision of the proposed method. PMID:26977340

  13. Aerosol Backscatter and Extinction Retrieval from Airborne Coherent Doppler Wind Lidar Measurements

    NASA Astrophysics Data System (ADS)

    Chouza, F.; Reitebuch, O.; Groß, S.; Rahm, S.; Freudenthaler, V.; Toledano, C.; Weinzierl, B.

    2016-06-01

    A novel method for coherent Doppler wind lidars (DWLs) calibration is shown in this work. Concurrent measurements of a ground based aerosol lidar operating at 532 nm and an airborne DWL at 2 μm are used in combination with sun photometer measurements for the retrieval of backscatter and extinction profiles. The presented method was successfully applied to the measurements obtained during the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE: http://www.pa.op.dlr.de/saltrace), which aimed to characterize the Saharan dust long range transport between Africa and the Caribbean.

  14. Data Analysis of a Pulsed 2-micron Coherent Differential Absorption Lidar For Atmospheric CO2 Measurements

    NASA Astrophysics Data System (ADS)

    Lu, J.; Yu, J.

    2013-12-01

    The study of climate change requires precise measurement of the production, migration, and sinking of greenhouse gases. Carbon Dioxide (CO2) is one of the principal greenhouse gases. NASA Langley Research Center (LARC) has developed a pulsed 2-micron coherent differential absorption lidar (DiAL) for CO2 measurement, operating on the R30 absorption line. On April 5, 2010, the lidar instrument transmitted alternating On-line and Off-line pulses from LARC into a residential area in Poquoson, Virginia; while a passive in-situ sensor measured the local CO2 concentration. This paper outlines a procedure to estimate CO2 concentration from atmospheric lidar return signal using the DiAL method; our calculation produced results in line with the in-situ measurement and matched the current state of DiAL instrument accuracy. Data from April 5 is part of a series of experiments validating the measurement accuracy and precision of this lidar. After a summative verification, a packaged lidar may be installed on research aircraft to perform CO2 studies at a great range of latitudes throughout the year, and to discover sources, sinks, and migration trends for this key greenhouse gas. The following procedure is used to estimate CO2 concentration from atmospheric lidar return using the DiAL method. First, MATLAB software developed at LARC sorts the lidar return into On-only and Off-only files containing pulses of only that type. The sorted pulses are reexamined for quality based on the center frequency, energy, and power - unsatisfactory pulses are removed. A 512-point Fast Fourier Transform (FFT) with 256-point shift is performed on each pulse to discretize the atmospheric return signal according to 63 distance 'bins'. Next, comparing decay rates of the On-line and Off-line atmospheric return intensity with distance yields the Differential Absorption Optical Slope (DAOD), which is proportional to the concentration of the desired gas. Then, in-situ meteorological data - pressure

  15. Doppler imaging with dual-detection full-range frequency domain optical coherence tomography

    PubMed Central

    Meemon, Panomsak; Lee, Kye-Sung; Rolland, Jannick P.

    2010-01-01

    Most of full-range techniques for Frequency Domain Optical Coherence Tomography (FD-OCT) reported to date utilize the phase relation between consecutive axial lines to reconstruct a complex interference signal and hence may exhibit degradation in either mirror image suppression performance or detectable velocity dynamic range or both when monitoring a moving sample such as flow activity. We have previously reported a technique of mirror image removal by simultaneous detection of the quadrature components of a complex spectral interference called a Dual-Detection Frequency Domain OCT (DD-FD-OCT) [Opt. Lett. 35, 1058-1060 (2010)]. The technique enables full range imaging without any loss of acquisition speed and is intrinsically less sensitive to phase errors generated by involuntary movements of the subject. In this paper, we demonstrate the application of the DD-FD-OCT to a phase-resolved Doppler imaging without degradation in either mirror image suppression performance or detectable velocity dynamic range that were observed in other full-range Doppler methods. In order to accommodate for Doppler imaging, we have developed a fiber-based DD-FD-OCT that more efficiently utilizes the source power compared with the previous free-space DD-FD-OCT. In addition, the velocity sensitivity of the phase-resolved DD-FD-OCT was investigated, and the relation between the measured Doppler phase shift and set flow velocity of a flow phantom was verified. Finally, we demonstrate the Doppler imaging using the DD-FD-OCT in a biological sample. PMID:21258488

  16. Absolute Retinal Blood Flow Measurement With a Dual-Beam Doppler Optical Coherence Tomography

    PubMed Central

    Dai, Cuixia; Liu, Xiaojing; Zhang, Hao F.; Puliafito, Carmen A.; Jiao, Shuliang

    2013-01-01

    Purpose. To test the capability of a novel dual-beam Doppler optical coherence tomography (OCT) technique for simultaneous in vivo measurement of the Doppler angle and, thus, the absolute retinal blood velocity and the retinal flow rate, without the influence of motion artifacts. Methods. A novel dual-beam Doppler spectral domain OCT (SD-OCT) was developed. The two probing beams are separated with a controllable distance along an arbitrary direction, both of which are controlled by two independent 2D optical scanners. Two sets of optical Doppler tomography (ODT) images are acquired simultaneously. The Doppler angle of each blood vessel segment is calculated from the relative coordinates of the centers of the blood vessel in the two corresponding ODT images. The absolute blood flow velocity and the volumetric blood flow rate can then be calculated. To measure the total retinal blood flow, we used a circular scan pattern centered at the optic disc to obtain two sets of concentric OCT/ODT images simultaneously. Results. We imaged two normal human subjects at ages of 48 and 34 years. The total retinal blood flow rates of the two human subjects were calculated to be 47.01 μL/min (older subject) and 51.37 μL/min (younger subject), respectively. Results showed that the performance of this imaging system is immune to eye movement, since the two sets of ODT images were acquired simultaneously. Conclusions. The dual-beam OCT/ODT system is successful in measuring the absolute retinal blood velocity and the volumetric flow rate. The advantage of the technique is that the two sets of ODT images used for the calculation are acquired simultaneously, which eliminates the influence of eye motion and ensures the accuracy of the calculated hemodynamic parameters. PMID:24222303

  17. Useful receiver telescope diameter of ground-based and airborne 1-, 2-, and 10-micron coherent lidars in the presence of atmospheric refractive turbulence

    NASA Technical Reports Server (NTRS)

    Chan, Kin P.; Killinger, Dennis K.

    1992-01-01

    Calculations of the integrated effect of atmospheric refractive turbulence on 1-, 2-, and 10-micron coherent lidar performance are presented for a series of different lidar propagation geometries. The effective lidar receiver telescope diameter is evaluated for each case. The results indicate that atmospheric turbulence should not be a significant factor in the performance of a downward-looking high-altitude or satellite-borne coherent lidar system. It is also shown that ground-based 1-2-micron coherent lidars may be limited in their useful telescope aperture, especially for horizontal or nearly horizontal path measurements near the ground.

  18. Multi-spacecraft coherent Doppler and ranging for interplanetary-navigation

    NASA Technical Reports Server (NTRS)

    Pollmeier, Vincent M.

    1995-01-01

    Future plans for planetary exploration currently include using multiple spacecraft to simultaneously explore one planet. This never before encountered situation places new demands on tracking systems used to support navigation. One possible solution to the problem of heavy ground resource conflicts is the use of multispacecraft coherent radio metric data, also known as, bent-pipe data. Analysis of the information content of these data types show that the information content of multi-spacecraft Doppler is dependent only on the frequency of the final downlink leg and is independent of the frequencies used on other legs. Numerical analysis shows that coherent bent-pipe data can provide significantly better capability to estimate the location of a lander on the surface of Mars than can direct lander to Earth radio metric data. However, this is complicated by difficulties in separating the effect of a lander position error from that of an orbiter position error for single passes of data.

  19. Measuring hemodynamics in the developing heart tube with four-dimensional gated Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Jenkins, Michael W.; Peterson, Lindsy; Gu, Shi; Gargesha, Madhusudhana; Wilson, David L.; Watanabe, Michiko; Rollins, Andrew M.

    2010-11-01

    Hemodynamics is thought to play a major role in heart development, yet tools to quantitatively assess hemodynamics in the embryo are sorely lacking. The especially challenging analysis of hemodynamics in the early embryo requires new technology. Small changes in blood flow could indicate when anomalies are initiated even before structural changes can be detected. Furthermore, small changes in the early embryo that affect blood flow could lead to profound abnormalities at later stages. We present a demonstration of 4-D Doppler optical coherence tomography (OCT) imaging of structure and flow, and present several new hemodynamic measurements on embryonic avian hearts at early stages prior to the formation of the four chambers. Using 4-D data, pulsed Doppler measurements could accurately be attained in the inflow and outflow of the heart tube. Also, by employing an en-face slice from the 4-D Doppler image set, measurements of stroke volume and cardiac output are obtained without the need to determine absolute velocity. Finally, an image plane orthogonal to the blood flow is used to determine shear stress by calculating the velocity gradient normal to the endocardium. Hemodynamic measurements will be crucial to identifying genetic and environmental factors that lead to congenital heart defects.

  20. Fully distributed absolute blood flow velocity measurement for middle cerebral arteries using Doppler optical coherence tomography

    PubMed Central

    Qi, Li; Zhu, Jiang; Hancock, Aneeka M.; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D.; Chen, Zhongping

    2016-01-01

    Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it is related to vessel geometry. In this paper, we present a volumetric vessel reconstruction approach that is capable of measuring the absolute BFV distributed along the entire middle cerebral artery (MCA) within a large field-of-view. The Doppler angle at each point of the MCA, representing the vessel geometry, is derived analytically by localizing the artery from pure DOCT images through vessel segmentation and skeletonization. Our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches. Experiments on rodents using swept-source optical coherence tomography showed that our approach was able to reveal the consequences of permanent MCA occlusion with absolute BFV measurement. PMID:26977365

  1. Visualization of Small-Diameter Vessels by Reduction of Incoherent Reverberation With Coherent Flow Power Doppler.

    PubMed

    Li, You Leo; Hyun, Dongwoon; Abou-Elkacem, Lotfi; Willmann, Juergen Karl; Dahl, Jeremy J

    2016-11-01

    Power Doppler (PD) imaging is a widely used technique for flow detection. Despite the wide use of Doppler ultrasound, limitations exist in the ability of Doppler ultrasound to assess slow flow in the small-diameter vasculature, such as the maternal spiral arteries and fetal villous arteries of the placenta and focal liver lesions. The sensitivity of PD in small vessel detection is limited by the low signal produced by slow flow and the noise associated with small vessels. The noise sources include electronic noise, stationary or slowly moving tissue clutter, reverberation clutter, and off-axis scattering from tissue, among others. In order to provide more sensitive detection of slow flow in small diameter vessels, a coherent flow imaging technique, termed coherent flow PD (CFPD), is characterized and evaluated with simulation, flow phantom experiment studies, and an in vivo animal small vessel detection study. CFPD imaging was introduced as a technique to detect slow blood flow. It has been demonstrated to detect slow flow below the detection threshold of conventional PD imaging using identical pulse sequences and filter parameters. In this paper, we compare CFPD with PD in the detection of blood flow in small-diameter vessels. The results from the study suggest that CFPD is able to provide a 7.5-12.5-dB increase in the signal-to-noise ratio (SNR) over PD images for the same physiological conditions and is less susceptible to reverberation clutter and thermal noise. Due to the increase in SNR, CFPD is able to detect small vessels in high channel noise cases, for which PD was unable to generate enough contrast to observe the vessel.

  2. Noninvasive microstructural and velocity imaging in humans by color Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yazdanfar, Siavash

    The objective of this dissertation is to develop the optical instrumentation, electronics, and signal processing for high-resolution blood flow imaging using optical coherence tomography (OCT) in human subjects. In particular, in vivo OCT blood flow imaging, termed color Doppler OCT (CDOCT), is applied for the first time to measurements in human vasculature of the retina and skin. CDOCT is similar to color Doppler ultrasound, whereas depth-resolved flow information is extracted from reflectivity profiles obtained from phase-sensitive, low-coherence interferometry. Although CDOCT has been demonstrated in tissue-mimicking phantoms and in living animal models, the technique has not yet been extended to blood flow imaging in humans. In this project, CDOCT was integrated with a modified slit lamp biomicroscope for imaging of retinal blood flow, and additional technical requirements necessary for retinal flow imaging were met. This system was used to acquire the first high resolution, cross-sectional images of blood flow with OCT in humans. The image acquisition rate was increased to examine retinal hemodynamics in normal subjects. A method was introduced for improving the velocity resolution by approximately two orders of magnitude, down to ˜1 micrometer/sec, by calculating the change in the phase across sequential scans. This technique was used to achieve the highest velocity resolution to date in scattering media, and applied to imaging the human microvasculature down to the capillary level. Finally, a modification of CDOCT based on differential phase contrast was introduced for high resolution imaging in the presence of motion artifact. This technique measures the differential Doppler frequency between two beams of orthogonal polarization states that are laterally displaced on the sample. Using polarization diversity detection, the common-mode noise was removed, enabling the measurement of flow in scattering media down to the theoretical frequency resolution.

  3. Spectral radiative transfer for the 4.0- to 5.0-micron bands of CO and CO2 with mild vibrational relaxation and Doppler shift

    NASA Astrophysics Data System (ADS)

    Limbaugh, C. C.; Hiers, R. S., III; Phillips, W. J.

    1990-06-01

    This paper presents representative results for line-by-line spectral calculations of the 4.3-micron band of CO2 and the 5.0-micron band of CO in a nozzle-constrained, vibrationally relaxing combustion flow. The effects of property gradients are included, with special emphasis on the effects of the frequency shift of the radiation and absorption due to the component of velocity along the line of sight. Broadband spectra resulting from the convolution of the line-by-line results with a broadband filter are examined. It is shown that the effect of the Doppler shift is to broaden the individual spectral features with an attendant increase in the emitted radiation. Spectral detail is lost because of the broadening, and the greatest effect on the magnitude of the emission is for those lines which are optically thick.

  4. Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length

    SciTech Connect

    Liu, Wenzhong; Yi, Ji; Chen, Siyu; Jiao, Shuliang; Zhang, Hao F.

    2015-09-15

    Purpose: Doppler optical coherence tomography (OCT) is widely used for measuring retinal blood flow. Existing Doppler OCT methods require the eyeball axial length, in which empirical values are usually used. However, variations in the axial length can create a bias unaccounted for in the retinal blood flow measurement. The authors plan to develop a Doppler OCT method that can measure the total retinal blood flow rate without requiring the eyeball axial length. Methods: The authors measured the retinal blood flow rate using a dual-ring scanning protocol. The small and large scanning rings entered the eye at different incident angles (small ring: 4°; large ring: 6°), focused on different locations on the retina, and detected the projected velocities/phase shifts along the probing beams. The authors calculated the ratio of the projected velocities between the two rings, and then used this ratio to estimate absolute flow velocity. The authors tested this method in both Intralipid phantoms and in vivo rats. Results: In the Intralipid flow phantom experiments, the preset and measured flow rates were consistent with the coefficient of determination as 0.97. Linear fitting between preset and measured flow rates determined the fitting slope as 1.07 and the intercept as −0.28. In in vivo rat experiments, the measured average total retinal blood flow was 7.02 ± 0.31μl/min among four wild-type rats. The authors’ measured flow rates were consistent with results in the literature. Conclusions: By using a dual-ring scanning protocol with carefully controlled incident angle difference between the two scanning rings in Doppler OCT, the authors demonstrated that it is feasible to measure the absolute retinal blood flow without knowing the eyeball axial length.

  5. Measuring Tropospheric Winds from Space Using a Coherent Doppler Lidar Technique

    NASA Technical Reports Server (NTRS)

    Miller, Timothy L.; Kavaya, Michael J.; Emmitt, G. David

    1999-01-01

    The global measurement of tropospheric wind profiles has been cited by the operational meteorological community as the most important missing element in the present and planned observing system. The most practical and economical method for obtaining this measurement is from low earth orbit, utilizing a Doppler lidar (laser radar) technique. Specifically, this paper will describe the coherent Doppler wind lidar (CDWL) technique, the design and progress of a current space flight project to fly such a system on the Space Shuttle, and plans for future flights of similar instruments. The SPARCLE (SPAce Readiness Coherent Lidar Experiment) is a Shuttle-based instrument whose flight is targeted for March, 2001. The objectives of SPARCLE are three-fold: Confirm that the coherent Doppler lidar technique can measure line-of-sight winds to within 1-2 m/s accuracy; Collect data to permit validation and improvement of instrument performance models to enable better design of future missions; and Collect wind and backscatter data for future mission optimization and for atmospheric studies. These objectives reflect the nature of the experiment and its program sponsor, NASA's New Millennium Program. The experiment is a technology validation mission whose primary purpose is to provide a space flight validation of this particular technology. (It should be noted that the CDWL technique has successfully been implemented from ground-based and aircraft-based platforms for a number of years.) Since the conduct of the SPARCLE mission is tied to future decisions on the choice of technology for free-flying, operational missions, the collection of data is intrinsically tied to the validation and improvement of instrument performance models that predict the sensitivity and accuracy of any particular present or future instrument system. The challenges unique to space flight for an instrument such as SPARCLE and follow-ons include: Obtaining the required lidar sensitivity from the long distance

  6. Estimation of aircraft wake vortex parameters from data measured with a 1.5-μm coherent Doppler lidar.

    PubMed

    Smalikho, I N; Banakh, V A

    2015-07-15

    A strategy of measurement by a 1.5-μm pulsed coherent Doppler lidar "Stream Line" has been developed, and a method for estimation of aircraft wake vortices from the lidar data has been proposed. The principal possibility of obtaining the information about the vortex situation over an airport airfield with the Stream-Line lidar has been demonstrated.

  7. Coherent Doppler Wind Lidar Development at NASA Langley Research Center for NASA Space-Based 3-D Winds Mission

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Kavaya, Michael J.; Yu, Jirong; Koch, Grady J.

    2012-01-01

    We review the 20-plus years of pulsed transmit laser development at NASA Langley Research Center (LaRC) to enable a coherent Doppler wind lidar to measure global winds from earth orbit. We briefly also discuss the many other ingredients needed to prepare for this space mission.

  8. New Insight into Rheology and Flow Properties of Complex Fluids with Doppler Optical Coherence Tomography

    NASA Astrophysics Data System (ADS)

    Salmela, Juha; Haavisto, Sanna; Koponen, Antti

    2014-05-01

    Flow properties of complex fluids such as colloidal suspensions, polymer solutions, fiber suspensions and blood have a vital function in many technological applications and biological systems. Yet, the basic knowledge on their properties is inadequate for many practical purposes. One important reason for this has been the lack of effective experimental methods that would allow detailed study of the flow behavior of especially opaque multi-phase fluids. Optical Coherence Tomography (OCT) is an emerging technique capable of simultaneous measurement of the internal structure and motion of most opaque materials, with resolution in the micrometer scale and measurement frequency up to 100 kHz. This mini-review will examine the recent results on the use of Doppler-OCT in the context of flows and rheological properties of complex fluids outside biomedical field.

  9. Doppler mapping of an alternating-sign flow with complex geometry using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Proskurin, S. G.; Potlov, A. Yu; Frolov, S. V.

    2014-01-01

    The method of sign-sensitive mapping of the given range of velocities in a flow with complex geometry based on the principles of optical coherence tomography is described. To produce an alternating-sign flow, the 1% aqueous intralipid solution and the tilted capillary entry with the contraction coefficient 4:1 are used. The mapping is controlled using two parameters, the value of one specific velocity (OSV) for mapping and the accuracy of its determination. The structure image and two OSV images (for positive and negative direction of motion) are obtained as a result of selecting and processing the relevant parts of the signal spectrum. The final image is a result of summing these three images and can be used as a Doppler equivelocity contour map.

  10. Doppler mapping of an alternating-sign flow with complex geometry using optical coherence tomography

    SciTech Connect

    Proskurin, S G; Potlov, A Yu; Frolov, S V

    2014-01-31

    The method of sign-sensitive mapping of the given range of velocities in a flow with complex geometry based on the principles of optical coherence tomography is described. To produce an alternating-sign flow, the 1% aqueous intralipid solution and the tilted capillary entry with the contraction coefficient 4:1 are used. The mapping is controlled using two parameters, the value of one specific velocity (OSV) for mapping and the accuracy of its determination. The structure image and two OSV images (for positive and negative direction of motion) are obtained as a result of selecting and processing the relevant parts of the signal spectrum. The final image is a result of summing these three images and can be used as a Doppler equivelocity contour map. (radiation scattering)

  11. Adaptive anisotropic diffusion for noise reduction of phase images in Fourier domain Doppler optical coherence tomography.

    PubMed

    Xia, Shaoyan; Huang, Yong; Peng, Shizhao; Wu, Yanfeng; Tan, Xiaodi

    2016-08-01

    Phase image in Fourier domain Doppler optical coherence tomography offers additional flow information of investigated samples, which provides valuable evidence towards accurate medical diagnosis. High quality phase images are thus desirable. We propose a noise reduction method for phase images by combining a synthetic noise estimation criteria based on local noise estimator (LNE) and distance median value (DMV) with anisotropic diffusion model. By identifying noise and signal pixels accurately and diffusing them with different coefficients respectively and adaptive iteration steps, we demonstrated the effectiveness of our proposed method in both phantom and mouse artery images. Comparison with other methods such as filtering method (mean, median filtering), wavelet method, probabilistic method and partial differential equation based methods in terms of peak signal-to-noise ratio (PSNR), equivalent number of looks (ENL) and contrast-to-noise ratio (CNR) showed the advantages of our method in reserving image energy and removing noise.

  12. New insight into rheology and flow properties of complex fluids with Doppler optical coherence tomography.

    PubMed

    Haavisto, Sanna; Koponen, Antti I; Salmela, Juha

    2014-01-01

    Flow properties of complex fluids such as colloidal suspensions, polymer solutions, fiber suspensions and blood have a vital function in many technological applications and biological systems. Yet, the basic knowledge on their properties is inadequate for many practical purposes. One important reason for this has been the lack of effective experimental methods that would allow detailed study of the flow behavior of especially opaque multi-phase fluids. Optical Coherence Tomography (OCT) is an emerging technique capable of simultaneous measurement of the internal structure and motion of most opaque materials, with resolution in the micrometer scale and measurement frequency up to 100 kHz. This mini-review will examine the recent results on the use of Doppler-OCT in the context of flows and rheological properties of complex fluids outside biomedical field.

  13. New insight into rheology and flow properties of complex fluids with Doppler optical coherence tomography

    PubMed Central

    Haavisto, Sanna; Koponen, Antti I.; Salmela, Juha

    2014-01-01

    Flow properties of complex fluids such as colloidal suspensions, polymer solutions, fiber suspensions and blood have a vital function in many technological applications and biological systems. Yet, the basic knowledge on their properties is inadequate for many practical purposes. One important reason for this has been the lack of effective experimental methods that would allow detailed study of the flow behavior of especially opaque multi-phase fluids. Optical Coherence Tomography (OCT) is an emerging technique capable of simultaneous measurement of the internal structure and motion of most opaque materials, with resolution in the micrometer scale and measurement frequency up to 100 kHz. This mini-review will examine the recent results on the use of Doppler-OCT in the context of flows and rheological properties of complex fluids outside biomedical field. PMID:24904920

  14. Adaptive anisotropic diffusion for noise reduction of phase images in Fourier domain Doppler optical coherence tomography

    PubMed Central

    Xia, Shaoyan; Huang, Yong; Peng, Shizhao; Wu, Yanfeng; Tan, Xiaodi

    2016-01-01

    Phase image in Fourier domain Doppler optical coherence tomography offers additional flow information of investigated samples, which provides valuable evidence towards accurate medical diagnosis. High quality phase images are thus desirable. We propose a noise reduction method for phase images by combining a synthetic noise estimation criteria based on local noise estimator (LNE) and distance median value (DMV) with anisotropic diffusion model. By identifying noise and signal pixels accurately and diffusing them with different coefficients respectively and adaptive iteration steps, we demonstrated the effectiveness of our proposed method in both phantom and mouse artery images. Comparison with other methods such as filtering method (mean, median filtering), wavelet method, probabilistic method and partial differential equation based methods in terms of peak signal-to-noise ratio (PSNR), equivalent number of looks (ENL) and contrast-to-noise ratio (CNR) showed the advantages of our method in reserving image energy and removing noise. PMID:27570687

  15. Signal to Noise Ratio Characterization of Coherent Doppler Lidar Backscattered Signals

    NASA Astrophysics Data System (ADS)

    Abdelazim, Sameh; Santoro, David; Arend, Mark; Moshary, Fred; Ahmed, Sam

    2016-06-01

    An eye-safe coherent Doppler Lidar (CDL) system for wind measurement was developed and tested at the Remote Sensing Laboratory of the City College of New York (CCNY). The system employs a 1542 nm fiber laser to leverage components' availability and affordability of the telecommunication industry. A balanced detector with a bandwidth extending from dc to 125 MHz is used to eliminate the common mode relative intensity noise (RIN). The system is shot noise limited i.e., the dominant component of received signals' noise is the shot noise. Wind velocity can be measured under nominal aerosol loading and atmospheric turbulence conditions for ranges up to 3 km while pointing vertically with 0.08 m/s precision.

  16. Retinal Blood Flow Response to Hyperoxia Measured With En Face Doppler Optical Coherence Tomography

    PubMed Central

    Pechauer, Alex D.; Tan, Ou; Liu, Liang; Jia, Yali; Hou, Vivian; Hills, William; Huang, David

    2016-01-01

    Purpose To use multiplane en face Doppler optical coherence tomography (OCT) to measure the change in total retinal blood flow (TRBF) in response to hyperoxia. Methods One eye of each healthy human participant (n = 8) was scanned with a commercial high-speed (70-kHz) spectral OCT system. Three repeated scans were captured at baseline and after 10 minutes of oxygen (hyperoxia) by open nasal mask. The procedure was performed twice on day 1 and once more on day 2. Blood flow of each vein was estimated using Doppler OCT at an optimized en face plane. The TRBF was summed from all veins at the optic disc. The TRBF hyperoxic response was calculated as the TRBF percent change from baseline. Results Participants experienced a 23.6% ± 10.7% (mean ± standard deviation [SD]) decrease (P < 0.001, paired t-test) in TRBF during hyperoxia. The within-day repeatability of baseline TRBF was 4.1% and the between-day reproducibility was 10.9% coefficient of variation (CV). Between-grader reproducibility was 3.9% CV. The repeatability and reproducibility (pooled SD) of hyperoxic response were 6.1% and 6.4%, respectively. Conclusions The multiplane en face Doppler OCT algorithm was able to detect, in all participants, a decreased TRBF in response to hyperoxia. The response magnitude for each participant varied among repeated trials, and the averaging of multiple trials was helpful in establishing the individual response. This technique shows good potential for the clinical investigation of vascular autoregulation. PMID:27409465

  17. Doppler Fourier Domain Optical Coherence Tomography for Label-Free Tissue Angiography

    NASA Astrophysics Data System (ADS)

    Leitgeb, Rainer A.; Szkulmowski, Maciej; Blatter, Cedric; Wojtkowski, Maciej

    Information about tissue perfusion and the vascular structure is certainly most important for assessment of tissue state or personal health and the diagnosis of any pathological conditions. It is therefore of key medical interest to have tools available for both quantitative blood flow assessment as well as qualitative vascular imaging. The strength of optical techniques is the unprecedented level of detail even for small capillary structures or microaneurysms and the possibility to combine different techniques for additional tissue spectroscopy giving insight into tissue metabolism. There is an immediate diagnostic and pharmacological demand for high-resolution, label-free, tissue angiography and flow assessment that in addition allow for precise depth gating of flow information. The most promising candidate is Doppler optical coherence tomography (DOCT) being noncontact, label free, and without employing hazardous radiation. DOCT provides fully quantitative volumetric information about blood flow together with the vascular and structural anatomy. Besides flow quantification, analysis of OCT signal fluctuations allows to contrast moving scatterers in tissue such as red blood cells from static tissue. This allows for non-invasive optical angiography and yields high resolution even for smallest capillaries. Because of the huge potential of DOCT and lable-free optical angiography for diagnosis, the last years saw a rapid increase of publications in this field with many different approaches. The present chapter gives an overview over existing Doppler OCT approaches and angiography techniques. It furthermore discusses limitations and noise issues, and gives examples for angiography in the eye and the skin.

  18. In vivo endoscopic Doppler optical coherence tomography imaging of mouse colon

    NASA Astrophysics Data System (ADS)

    Welge, Weston A.; Barton, Jennifer K.

    2016-03-01

    Colorectal cancer remains the second deadliest cancer in the United States, despite the high sensitivity and specificity of colonoscopy and sigmoidoscopy. While these standard imaging procedures can accurately detect medium and large polyps, some studies have shown miss rates up to 25% for polyps less than 5 mm in diameter. An imaging modality capable of detecting small lesions could potentially improve patient outcomes. Optical coherence tomography (OCT) has been shown to be a powerful imaging modality for adenoma detection in a mouse model of colorectal cancer. While previous work has focused on analyzing the structural OCT images based on thickening of the mucosa and changes in light attenuation in depth, imaging the microvasculature of the colon may enable earlier detection of polyps. The structure and function of vessels grown to support tumor growth are markedly different from healthy vessels. Doppler OCT is capable of imaging microvessels in vivo. We developed a method of processing raw fringe data from a commercial swept-source OCT system using a lab-built miniature endoscope to extract microvessels. This method can be used to measure vessel count and density and to measure flow velocities. This may improve early detection and aid in the development of new chemopreventive and chemotherapeutic drugs. We present, to the best of our knowledge, the first endoscopic Doppler OCT images of in vivo mouse colon.

  19. Wind profiling for a coherent wind Doppler lidar by an auto-adaptive background subtraction approach.

    PubMed

    Wu, Yanwei; Guo, Pan; Chen, Siying; Chen, He; Zhang, Yinchao

    2017-04-01

    Auto-adaptive background subtraction (AABS) is proposed as a denoising method for data processing of the coherent Doppler lidar (CDL). The method is proposed specifically for a low-signal-to-noise-ratio regime, in which the drifting power spectral density of CDL data occurs. Unlike the periodogram maximum (PM) and adaptive iteratively reweighted penalized least squares (airPLS), the proposed method presents reliable peaks and is thus advantageous in identifying peak locations. According to the analysis results of simulated and actually measured data, the proposed method outperforms the airPLS method and the PM algorithm in the furthest detectable range. The proposed method improves the detection range approximately up to 16.7% and 40% when compared to the airPLS method and the PM method, respectively. It also has smaller mean wind velocity and standard error values than the airPLS and PM methods. The AABS approach improves the quality of Doppler shift estimates and can be applied to obtain the whole wind profiling by the CDL.

  20. Four-dimensional structural and Doppler optical coherence tomography imaging on graphics processing units.

    PubMed

    Sylwestrzak, Marcin; Szlag, Daniel; Szkulmowski, Maciej; Gorczynska, Iwona; Bukowska, Danuta; Wojtkowski, Maciej; Targowski, Piotr

    2012-10-01

    The authors present the application of graphics processing unit (GPU) programming for real-time three-dimensional (3-D) Fourier domain optical coherence tomography (FdOCT) imaging with implementation of flow visualization algorithms. One of the limitations of FdOCT is data processing time, which is generally longer than data acquisition time. Utilizing additional algorithms, such as Doppler analysis, further increases computation time. The general purpose computing on GPU (GPGPU) has been used successfully for structural OCT imaging, but real-time 3-D imaging of flows has so far not been presented. We have developed software for structural and Doppler OCT processing capable of visualization of two-dimensional (2-D) data (2000 A-scans, 2048 pixels per spectrum) with an image refresh rate higher than 120 Hz. The 3-D imaging of 100×100 A-scans data is performed at a rate of about 9 volumes per second. We describe the software architecture, organization of threads, and optimization. Screen shots recorded during real-time imaging of a flow phantom and the human eye are presented.

  1. Evaluation of hemodynamics changes during interventional stent placement using Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Vuong, Barry; Genis, Helen; Wong, Ronnie; Ramjist, Joel; Jivraj, Jamil; Farooq, Hamza; Sun, Cuiru; Yang, Victor X. D.

    2015-03-01

    Carotid atherosclerosis is a critical medical concern that can lead to ischemic stroke. Local hemodynamic patterns have also been associated with the development of atherosclerosis, particularly in regions with disturbed flow patterns such as bifurcations. Traditionally, this disease was treated using carotid endarterectomy, however recently there is an increasing trend of carotid artery stenting due to its minimally invasive nature. It is well known that this interventional technique creates changes in vasculature geometry and hemodynamic patterns due to the interaction of stent struts with arterial lumen, and is associated with complications such as distal emboli and restenosis. Currently, there is no standard imaging technique to evaluate regional hemodynamic patterns found in stented vessels. Doppler optical coherence tomography (DOCT) provides an opportunity to identify in vivo hemodynamic changes in vasculature using high-resolution imaging. In this study, blood flow profiles were examined at the bifurcation junction in the internal carotid artery (ICA) in a porcine model following stent deployment. Doppler imaging was further conducted using pulsatile flow in a phantom model, and then compared to computational fluid dynamics (CFD) simulation of a virtual bifurcation to assist with the interpretation of emphin vivo results.

  2. One-micron resolution optical coherence tomography (OCT) in vivo for cellular level imaging

    NASA Astrophysics Data System (ADS)

    Cui, Dongyao; Liu, Xinyu; Zhang, Jing; Yu, Xiaojun; Sun, Ding; Luo, Yuemei; Gu, Jun; Shum, Ping; Liu, Linbo

    2015-03-01

    We developed a spectral domain OCT system combining two NIR, CW light sources of different spectral range. Its resolving power is validated by visualizing the cellular structures of zebra fish larvae in vivo. An NIR extended illumination from 755-1100 nm is achieved. The axial resolution is 1.27 μm in air, corresponding to 0.93μm in tissue (n=1.36), which is the highest axial resolution using NIR, CW laser sources up to date to the best of our knowledge. In vivo imaging is conducted to demonstrate the resolving power of proposed one-micron resolution OCT system. The top and bottom surfaces of individual disk-like red blood cell is reliably visualized, as well as flat, spindle shaped endothelial cells lining along the luminal surface of the blood vessel wall. This study provides a viable solution for cellular and subcellular level OCT imaging system which is also very competitive in cost.

  3. A comparison between coherent and noncoherent mobile systems in large Doppler shift, delay spread, and C/I environment

    NASA Technical Reports Server (NTRS)

    Feher, Kamilo

    1993-01-01

    The performance and implementation complexity of coherent and of noncoherent QPSK and GMSK modulation/demodulation techniques in a complex mobile satellite systems environment, including large Doppler shift, delay spread, and low C/I, are compared. We demonstrate that for large f(sub d)T(sub b) products, where f(sub d) is the Doppler shift and T(sub b) is the bit duration, noncoherent (discriminator detector or differential demodulation) systems have a lower BER floor than their coherent counterparts. For significant delay spreads, e.g., tau(sub rms) greater than 0.4 T(sub b), and low C/I, coherent systems outperform noncoherent systems. However, the synchronization time of coherent systems is longer than that of noncoherent systems. Spectral efficiency, overall capacity, and related hardware complexity issues of these systems are also analyzed. We demonstrate that coherent systems have a simpler overall architecture (IF filter implementation-cost versus carrier recovery) and are more robust in an RF frequency drift environment. Additionally, the prediction tools, computer simulations, and analysis of coherent systems is simpler. The threshold or capture effect in low C/I interference environment is critical for noncoherent discriminator based systems. We conclude with a comparison of hardware architectures of coherent and of noncoherent systems, including recent trends in commercial VLSI technology and direct baseband to RF transmit, RF to baseband (0-IF) receiver implementation strategies.

  4. All-Fiber Airborne Coherent Doppler Lidar to Measure Wind Profiles

    NASA Astrophysics Data System (ADS)

    Liu, Jiqiao; Zhu, Xiaopeng; Diao, Weifeng; Zhang, Xin; Liu, Yuan; Bi, Decang; Jiang, Liyuan; Shi, Wei; Zhu, Xiaolei; Chen, Weibiao

    2016-06-01

    An all-fiber airborne pulsed coherent Doppler lidar (CDL) prototype at 1.54μm is developed to measure wind profiles in the lower troposphere layer. The all-fiber single frequency pulsed laser is operated with pulse energy of 300μJ, pulse width of 400ns and pulse repetition rate of 10kHz. To the best of our knowledge, it is the highest pulse energy of all-fiber eye-safe single frequency laser that is used in airborne coherent wind lidar. The telescope optical diameter of monostatic lidar is 100 mm. Velocity-Azimuth-Display (VAD) scanning is implemented with 20 degrees elevation angle in 8 different azimuths. Real-time signal processing board is developed to acquire and process the heterodyne mixing signal with 10000 pulses spectra accumulated every second. Wind profiles are obtained every 20 seconds. Several experiments are implemented to evaluate the performance of the lidar. We have carried out airborne wind lidar experiments successfully, and the wind profiles are compared with aerological theodolite and ground based wind lidar. Wind speed standard error of less than 0.4m/s is shown between airborne wind lidar and balloon aerological theodolite.

  5. Field performance of an all-semiconductor laser coherent Doppler lidar.

    PubMed

    Rodrigo, Peter John; Pedersen, Christian

    2012-06-15

    We implement and test what, to our knowledge, is the first deployable coherent Doppler lidar (CDL) system based on a compact, inexpensive all-semiconductor laser (SL). To demonstrate the field performance of our SL-CDL remote sensor, we compare a 36 h time series of averaged radial wind speeds measured by our instrument at an 80 m distance to those simultaneously obtained from an industry-standard sonic anemometer (SA). An excellent degree of correlation (R2=0.994 and slope=0.996) is achieved from a linear regression analysis of the CDL versus SA wind speed data. The lidar system is capable of providing high data availability, ranging from 85% to 100% even under varying outdoor (temperature and humidity) conditions during the test period. We also show the use of our SL-CDL for monitoring the dependence of aerosol backscatter on relative humidity. This work points to the feasibility of a more general class of low-cost, portable remote sensors based on all-SL emitters for applications that require demanding laser stability and coherence.

  6. Dual-frequency laser Doppler velocimeter for speckle noise reduction and coherence enhancement.

    PubMed

    Cheng, Chih-Hao; Lee, Chia-Wei; Lin, Tzu-Wei; Lin, Fan-Yi

    2012-08-27

    We study the characteristics of a dual-frequency laser Doppler velocimeter (DF-LDV) based on an optically injected semiconductor laser. The laser operated in a period-one (P1) dynamical state with two optical frequencies separated by 11.25 GHz is used as the dual-frequency light source. With a microwave beat signal carried by the light, the DF-LDV possesses both the advantages of good directionality, high intensity, and high spatial resolution from the light and low speckle noise and good coherence from the microwave, respectively. By phase-locking the two frequency components with a microwave signal, the coherence of the dual-frequency light source can be further improved and the detection range can be much extended. In this paper, velocity resolutions of the DF-LDV with different amounts of speckle noise and at different detection ranges are experimentally measured and analyzed. Compared with the conventional single-frequency LDV (SF-LDV), the velocity resolution of the DF-LDV is improved by 8 × 10(3) times from 2.5 m/s to 0.31 mm/s for a target with a longitudinal velocity vz = 4 cm/s, a transverse velocity vt = 5 m/s, and at a detection range of 108 m.

  7. Micro-Doppler measurement of insect wing-beat frequencies with W-band coherent radar.

    PubMed

    Wang, Rui; Hu, Cheng; Fu, Xiaowei; Long, Teng; Zeng, Tao

    2017-05-03

    The wingbeat frequency of insect migrant is regarded potentially valuable for species identification and has long drawn widespread attention in radar entomology. Principally, the radar echo signal can be used to extract wingbeat information, because both the signal amplitude and phase could be modulated by wing-beating. With respect to existing entomological radars, signal amplitude modulation has been used for wingbeat frequency measurement of large insects for many years, but the wingbeat frequency measurement of small insects remains a challenge. In our research, W-band and S-band coherent radars are used to measure the insect wingbeat frequency. The results show that the wingbeat-induced amplitude modulation of W-band radar is more intense than that of the S-band radar and the W-band radar could measure the wingbeat frequency of smaller insects. In addition, it is validated for the first time that the signal phase could also be used to measure the insect wingbeat frequency based on micro-Doppler effect. However, whether the wingbeat frequency measurement is based on the amplitude or phase modulation, it is found that the W-band coherent radar has better performance on both the measurement precision and the measurable minimum size of the insect.

  8. Remote sensing of multi-level wind fields with high-energy airborne scanning coherent Doppler lidar.

    PubMed

    Rothermel, J; Olivier, L; Banta, R; Hardesty, R M; Howell, J; Cutten, D; Johnson, S; Menzies, R; Tratt, D M

    1998-01-19

    The atmospheric lidar remote sensing groups of NOAA Environmental Technology Laboratory, NASA Marshall Space Flight Center, and Jet Propulsion Laboratory have developed and flown a scanning, 1 Joule per pulse, CO2 coherent Doppler lidar capable of mapping a three-dimensional volume of atmospheric winds and aerosol backscatter in the planetary boundary layer, free troposphere, and lower stratosphere. Applications include the study of severe and non-severe atmospheric flows, intercomparisons with other sensors, and the simulation of prospective satellite Doppler lidar wind profilers. Examples of wind measurements are given for the marine boundary layer and near the coastline of the western United States.

  9. Remote Sensing of Multi-Level Wind Fields with High-Energy Airborne Scanning Coherent Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry; Olivier, Lisa D.; Banta, Robert M.; Hardesty, R. Michael; Howell, James N.; Cutten, Dean R.; Johnson, Steven C.; Menzies, Robert T.; Tratt, David M.

    1997-01-01

    The atmospheric lidar remote sensing groups of NOAA Environmental Technology Laboratory, NASA Marshall Space Flight Center, and Jet Propulsion Laboratory have developed and flown a scanning, 1 Joule per pulse, CO2 coherent Doppler lidar capable of mapping a three-dimensional volume of atmospheric winds and aerosol backscatter in the troposphere and lower stratosphere. Applications include the study of severe and non-severe atmospheric flows, intercomparisons with other sensors, and the simulation of prospective satellite Doppler lidar wind profilers. Examples of wind measurements are given for the marine boundary layer and near the coastline of the western United States.

  10. Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Choma, Michael A.; Suter, Melissa J.; Vakoc, Benjamin J.; Bouma, Brett E.; Tearney, Guillermo J.

    2010-09-01

    Drosophila melanogaster (fruit fly) is a central organism in biology and is becoming increasingly important in the cardiovascular sciences. Prior work in optical imaging of the D. melanogaster heart has focused on static and dynamic structural anatomy. In the study, it is demonstrated that Doppler optical coherence tomography can quantify dynamic heart wall velocity and hemolymph flow in adult D. melanogaster. Since hemolymph is optically transparent, a novel exogenous contrast technique is demonstrated to increase the backscatter-based intracardiac Doppler flow signal. The results presented here open up new possibilities for functional cardiovascular phenotyping of normal and mutant D. melanogaster.

  11. Remote Sensing of Multi-Level Wind Fields with High-Energy Airborne Scanning Coherent Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry; Olivier, Lisa D.; Banta, Robert M.; Hardesty, R. Michael; Howell, James N.; Cutten, Dean R.; Johnson, Steven C.; Menzies, Robert T.; Tratt, David M.

    1997-01-01

    The atmospheric lidar remote sensing groups of NOAA Environmental Technology Laboratory, NASA Marshall Space Flight Center, and Jet Propulsion Laboratory have developed and flown a scanning, 1 Joule per pulse, CO2 coherent Doppler lidar capable of mapping a three-dimensional volume of atmospheric winds and aerosol backscatter in the troposphere and lower stratosphere. Applications include the study of severe and non-severe atmospheric flows, intercomparisons with other sensors, and the simulation of prospective satellite Doppler lidar wind profilers. Examples of wind measurements are given for the marine boundary layer and near the coastline of the western United States.

  12. A simulation environment for assisting system design of coherent laser doppler wind sensor for active wind turbine pitch control

    NASA Astrophysics Data System (ADS)

    Shinohara, Leilei; Pham Tran, Tuan Anh; Beuth, Thorsten; Umesh Babu, Harsha; Heussner, Nico; Bogatscher, Siegwart; Danilova, Svetlana; Stork, Wilhelm

    2013-05-01

    In order to assist a system design of laser coherent Doppler wind sensor for active pitch control of wind turbine systems (WTS), we developed a numerical simulation environment for modeling and simulation of the sensor system. In this paper we present this simulation concept. In previous works, we have shown the general idea and the possibility of using a low cost coherent laser Doppler wind sensing system for an active pitch control of WTS in order to achieve a reduced mechanical stress, increase the WTS lifetime and therefore reduce the electricity price from wind energy. Such a system is based on a 1.55μm Continuous-Wave (CW) laser plus an erbium-doped fiber amplifier (EDFA) with an output power of 1W. Within this system, an optical coherent detection method is chosen for the Doppler frequency measurement in megahertz range. A comparatively low cost short coherent length laser with a fiber delay line is used for achieving a multiple range measurement. In this paper, we show the current results on the improvement of our simulation by applying a Monte Carlo random generation method for positioning the random particles in atmosphere and extend the simulation to the entire beam penetrated space by introducing a cylindrical co-ordinate concept and meshing the entire volume into small elements in order to achieve a faster calculation and gain more realistic simulation result. In addition, by applying different atmospheric parameters, such as particle sizes and distributions, we can simulate different weather and wind situations.

  13. Accuracy of a pulse-coherent acoustic Doppler profiler in a wave-dominated flow

    USGS Publications Warehouse

    Lacy, J.R.; Sherwood, C.R.

    2004-01-01

    The accuracy of velocities measured by a pulse-coherent acoustic Doppler profiler (PCADP) in the bottom boundary layer of a wave-dominated inner-shelf environment is evaluated. The downward-looking PCADP measured velocities in eight 10-cm cells at 1 Hz. Velocities measured by the PCADP are compared to those measured by an acoustic Doppler velocimeter for wave orbital velocities up to 95 cm s-1 and currents up to 40 cm s-1. An algorithm for correcting ambiguity errors using the resolution velocities was developed. Instrument bias, measured as the average error in burst mean speed, is -0.4 cm s-1 (standard deviation = 0.8). The accuracy (root-mean-square error) of instantaneous velocities has a mean of 8.6 cm s-1 (standard deviation = 6.5) for eastward velocities (the predominant direction of waves), 6.5 cm s-1 (standard deviation = 4.4) for northward velocities, and 2.4 cm s-1 (standard deviation = 1.6) for vertical velocities. Both burst mean and root-mean-square errors are greater for bursts with ub ??? 50 cm s-1. Profiles of burst mean speeds from the bottom five cells were fit to logarithmic curves: 92% of bursts with mean speed ??? 5 cm s-1 have a correlation coefficient R2 > 0.96. In cells close to the transducer, instantaneous velocities are noisy, burst mean velocities are biased low, and bottom orbital velocities are biased high. With adequate blanking distances for both the profile and resolution velocities, the PCADP provides sufficient accuracy to measure velocities in the bottom boundary layer under moderately energetic inner-shelf conditions.

  14. Demonstration of coherent Doppler lidar for navigation in GPS-denied environments

    NASA Astrophysics Data System (ADS)

    Amzajerdian, Farzin; Hines, Glenn D.; Pierrottet, Diego F.; Barnes, Bruce W.; Petway, Larry B.; Carson, John M.

    2017-05-01

    A coherent Doppler lidar has been developed to address NASA's need for a high-performance, compact, and cost-effective velocity and altitude sensor onboard its landing vehicles. Future robotic and manned missions to solar system bodies require precise ground-relative velocity vector and altitude data to execute complex descent maneuvers and safe, soft landing at a pre-designated site. This lidar sensor, referred to as a Navigation Doppler Lidar (NDL), meets the required performance of the landing missions while complying with vehicle size, mass, and power constraints. Operating from up to four kilometers altitude, the NDL obtains velocity and range precision measurements reaching 2 cm/sec and 2 meters, respectively, dominated by the vehicle motion. Terrestrial aerial vehicles will also benefit from NDL data products as enhancement or replacement to GPS systems when GPS is unavailable or redundancy is needed. The NDL offers a viable option to aircraft navigation in areas where the GPS signal can be blocked or jammed by intentional or unintentional interference. The NDL transmits three laser beams at different pointing angles toward the ground to measure range and velocity along each beam using a frequency modulated continuous wave (FMCW) technique. The three line-of-sight measurements are then combined in order to determine the three components of the vehicle velocity vector and its altitude relative to the ground. This paper describes the performance and capabilities that the NDL demonstrated through extensive ground tests, helicopter flight tests, and onboard an autonomous rocket-powered test vehicle while operating in closedloop with a guidance, navigation, and control (GN and C) system.

  15. MEMS-Based Handheld Fourier Domain Doppler Optical Coherence Tomography for Intraoperative Microvascular Anastomosis Imaging

    PubMed Central

    Huang, Yong; Furtmüller, Georg J.; Tong, Dedi; Zhu, Shan; Lee, W. P. Andrew; Brandacher, Gerald; Kang, Jin U.

    2014-01-01

    Purpose To demonstrate the feasibility of a miniature handheld optical coherence tomography (OCT) imager for real time intraoperative vascular patency evaluation in the setting of super-microsurgical vessel anastomosis. Methods A novel handheld imager Fourier domain Doppler optical coherence tomography based on a 1.3-µm central wavelength swept source for extravascular imaging was developed. The imager was minimized through the adoption of a 2.4-mm diameter microelectromechanical systems (MEMS) scanning mirror, additionally a 12.7-mm diameter lens system was designed and combined with the MEMS mirror to achieve a small form factor that optimize functionality as a handheld extravascular OCT imager. To evaluate in-vivo applicability, super-microsurgical vessel anastomosis was performed in a mouse femoral vessel cut and repair model employing conventional interrupted suture technique as well as a novel non-suture cuff technique. Vascular anastomosis patency after clinically successful repair was evaluated using the novel handheld OCT imager. Results With an adjustable lateral image field of view up to 1.5 mm by 1.5 mm, high-resolution simultaneous structural and flow imaging of the blood vessels were successfully acquired for BALB/C mouse after orthotopic hind limb transplantation using a non-suture cuff technique and BALB/C mouse after femoral artery anastomosis using a suture technique. We experimentally quantify the axial and lateral resolution of the OCT to be 12.6 µm in air and 17.5 µm respectively. The OCT has a sensitivity of 84 dB and sensitivity roll-off of 5.7 dB/mm over an imaging range of 5 mm. Imaging with a frame rate of 36 Hz for an image size of 1000(lateral)×512(axial) pixels using a 50,000 A-lines per second swept source was achieved. Quantitative vessel lumen patency, lumen narrowing and thrombosis analysis were performed based on acquired structure and Doppler images. Conclusions A miniature handheld OCT imager that can be used for

  16. Aerosol backscatter measurements at 10.6 microns with airborne and ground-based CO2 Doppler lidars over the Colorado High Plains. I - Lidar intercomparison

    NASA Technical Reports Server (NTRS)

    Bowdle, David A.; Rothermel, Jeffry; Vaughan, J. Michael; Brown, Derek W.; Post, Madison J.

    1991-01-01

    An airborne continuous-wave (CW) focused CO2 Doppler lidar and a ground-based pulsed CO2 Doppler lidar were to obtain seven pairs of comparative measurements of tropospheric aerosol backscatter profiles at 10.6-micron wavelength, near Denver, Colorado, during a 20-day period in July 1982. In regions of uniform backscatter, the two lidars show good agreement, with differences usually less than about 50 percent near 8-km altitude and less than a factor of 2 or 3 elsewhere but with the pulsed lidar often lower than the CW lidar. Near sharp backscatter gradients, the two lidars show poorer agreement, with the pulsed lidar usually higher than the CW lidar. Most discrepancies arise from a combination of atmospheric factors and instrument factors, particularly small-scale areal and temporal backscatter heterogeneity above the planetary boundary layer, unusual large-scale vertical backscatter structure in the upper troposphere and lower stratosphere, and differences in the spatial resolution, detection threshold, and noise estimation for the two lidars.

  17. Aerosol backscatter measurements at 10.6 microns with airborne and ground-based CO2 Doppler lidars over the Colorado High Plains. I - Lidar intercomparison

    NASA Technical Reports Server (NTRS)

    Bowdle, David A.; Rothermel, Jeffry; Vaughan, J. Michael; Brown, Derek W.; Post, Madison J.

    1991-01-01

    An airborne continuous-wave (CW) focused CO2 Doppler lidar and a ground-based pulsed CO2 Doppler lidar were to obtain seven pairs of comparative measurements of tropospheric aerosol backscatter profiles at 10.6-micron wavelength, near Denver, Colorado, during a 20-day period in July 1982. In regions of uniform backscatter, the two lidars show good agreement, with differences usually less than about 50 percent near 8-km altitude and less than a factor of 2 or 3 elsewhere but with the pulsed lidar often lower than the CW lidar. Near sharp backscatter gradients, the two lidars show poorer agreement, with the pulsed lidar usually higher than the CW lidar. Most discrepancies arise from a combination of atmospheric factors and instrument factors, particularly small-scale areal and temporal backscatter heterogeneity above the planetary boundary layer, unusual large-scale vertical backscatter structure in the upper troposphere and lower stratosphere, and differences in the spatial resolution, detection threshold, and noise estimation for the two lidars.

  18. Graphics processor unit acceleration enables realtime endovascular Doppler optical coherence tomography imaging

    NASA Astrophysics Data System (ADS)

    Barrows, Dexter; Vuong, Barry; Lee, Kenneth; Jivraj, Jamil; Yang, Victor X. D.

    2017-02-01

    Endovascular Optical Coherence Tomography (OCT) has previously been used in both bench-top and clinical environments to produce vascular images, and can be helpful in characterizing, among other pathologies, plaque build-up and impedances to normal blood ow. The raw data produced can also be processed to yield high- resolution blood velocity information, but this computation is expensive and has previously only been available a posteriori using post-processing software. Real-time Doppler OCT (DOCT) imaging has been demonstrated before in the skin and eye, but this capability has not been available to vascular surgeons. Graphics Processing Units (GPUs) can be used to dramatically accelerate this type of distributed computation. In this paper we present a software package capable of real-time DOCT processing and circular image display using GPU acceleration designed to operate with catheter-based clinical OCT systems. This image data is overlayed onto structural images providing clinicians with live, high-resolution blood velocity information to complement anatomical data.

  19. Parabolic BM-scan technique for full range Doppler spectral domain optical coherence tomography.

    PubMed

    Jaillon, Franck; Makita, Shuichi; Yabusaki, Masaki; Yasuno, Yoshiaki

    2010-01-18

    A full range spectral domain optical coherence tomography (SD-OCT) technique that relies on the linear phase modulation of one of the interferometer arms has been widely utilized. Although this method is useful, the mirror image elimination is not perfect for samples in which regions with high axial motion exist. In this paper, we introduce a new modulation pattern to overcome this mirror image elimination failure. This new modulation is a parabolic phase modulation in the transverse scanning direction, and is applied to the SD-OCT reference beam by an electro-optic modulator. Flow phantom and in vivo experiments demonstrate that for moving structures with large velocities, this parabolic phase modulation technique presents better mirror image elimination than a standard linear phase modulation method. A direct consequence of this enhanced mirror image removal is an improved velocity range obtained with phase-resolved Doppler imaging. Consequently, applying the proposed technique in retinal blood flow measurements may be useful for ophthalmologic diagnosis.

  20. Doppler optical coherence tomography imaging of local fluid flow and shear stress within microporous scaffolds

    NASA Astrophysics Data System (ADS)

    Jia, Yali; Bagnaninchi, Pierre O.; Yang, Ying; Haj, Alicia El; Hinds, Monica T.; Kirkpatrick, Sean J.; Wang, Ruikang K.

    2009-05-01

    Establishing a relationship between perfusion rate and fluid shear stress in a 3D cell culture environment is an ongoing and challenging task faced by tissue engineers. We explore Doppler optical coherence tomography (DOCT) as a potential imaging tool for in situ monitoring of local fluid flow profiles inside porous chitosan scaffolds. From the measured fluid flow profiles, the fluid shear stresses are evaluated. We examine the localized fluid flow and shear stress within low- and high-porosity chitosan scaffolds, which are subjected to a constant input flow rate of 0.5 ml.min-1. The DOCT results show that the behavior of the fluid flow and shear stress in micropores is strongly dependent on the micropore interconnectivity, porosity, and size of pores within the scaffold. For low-porosity and high-porosity chitosan scaffolds examined, the measured local fluid flow and shear stress varied from micropore to micropore, with a mean shear stress of 0.49+/-0.3 dyn.cm-2 and 0.38+/-0.2 dyn.cm-2, respectively. In addition, we show that the scaffold's porosity and interconnectivity can be quantified by combining analyses of the 3D structural and flow images obtained from DOCT.

  1. Comparison of Kasai Autocorrelation and Maximum Likelihood Estimators for Doppler Optical Coherence Tomography

    PubMed Central

    Chan, Aaron C.; Srinivasan, Vivek J.

    2013-01-01

    In optical coherence tomography (OCT) and ultrasound, unbiased Doppler frequency estimators with low variance are desirable for blood velocity estimation. Hardware improvements in OCT mean that ever higher acquisition rates are possible, which should also, in principle, improve estimation performance. Paradoxically, however, the widely used Kasai autocorrelation estimator’s performance worsens with increasing acquisition rate. We propose that parametric estimators based on accurate models of noise statistics can offer better performance. We derive a maximum likelihood estimator (MLE) based on a simple additive white Gaussian noise model, and show that it can outperform the Kasai autocorrelation estimator. In addition, we also derive the Cramer Rao lower bound (CRLB), and show that the variance of the MLE approaches the CRLB for moderate data lengths and noise levels. We note that the MLE performance improves with longer acquisition time, and remains constant or improves with higher acquisition rates. These qualities may make it a preferred technique as OCT imaging speed continues to improve. Finally, our work motivates the development of more general parametric estimators based on statistical models of decorrelation noise. PMID:23446044

  2. Electrostatic forward-viewing scanning probe for Doppler optical coherence tomography using a dissipative polymer catheter.

    PubMed

    Munce, Nigel R; Mariampillai, Adrian; Standish, Beau A; Pop, Mihaela; Anderson, Kevan J; Liu, George Y; Luk, Tim; Courtney, Brian K; Wright, Graham A; Vitkin, I Alex; Yang, Victor X D

    2008-04-01

    A novel flexible scanning optical probe is constructed with a finely etched optical fiber strung through a platinum coil in the lumen of a dissipative polymer. The packaged probe is 2.2 mm in diameter with a rigid length of 6mm when using a ball lens or 12 mm when scanning the fiber proximal to a gradient-index (GRIN) lens. Driven by constant high voltage (1-3 kV) at low current (< 5 microA), the probe oscillates to provide wide forward-viewing angle (13 degrees and 33 degrees with ball and GRIN lens designs, respectively) and high-frame-rate (10-140 fps) operation. Motion of the probe tip is observed with a high-speed camera and compared with theory. Optical coherence tomography (OCT) imaging with the probe is demonstrated with a wavelength-swept source laser. Images of an IR card as well as in vivo Doppler OCT images of a tadpole heart are presented. This optomechanical design offers a simple, inexpensive method to obtain a high-frame-rate forward-viewing scanning probe.

  3. Doppler optical coherence tomography imaging of local fluid flow and shear stress within microporous scaffolds

    PubMed Central

    Jia, Yali; Bagnaninchi, Pierre O.; Yang, Ying; Haj, Alicia El; Hinds, Monica T.; Kirkpatrick, Sean J.; Wang, Ruikang K.

    2009-01-01

    Establishing a relationship between perfusion rate and fluid shear stress in a 3-dimensional cell culture environment is an ongoing and challenging task faced by tissue engineers. In this study, we explore Doppler optical coherence tomography (DOCT) as a potential imaging tool for in situ monitoring of local fluid flow profiles inside porous chitosan scaffolds. From the measured fluid flow profiles, the fluid shear stresses are evaluated. We examine the localized fluid flow and shear stress within low and high porosity chitosan scaffolds, which are subjected to a constant input flow rate of 0.5 ml·min-1. The DOCT results show that the behaviour of the fluid flow and shear stress in micropores is strongly dependent on the micropore interconnectivity, porosity, and size of pores within the scaffold. For low porosity and high porosity chitosan scaffolds examined, the measured local fluid flow and shear stress varied from micropore to micropore with a mean shear stress of 0.49±0.3 dyn·cm-2 and 0.38±0.2 dyn·cm-2, respectively. In addition, we show that the scaffold’s porosity and interconnectivity can be quantified by combining analyses of the 3-dimensional structural and flow images obtained from DOCT. PMID:19566307

  4. Coherent population trapping resonances at lower atomic levels of Doppler broadened optical lines

    SciTech Connect

    Şahin, E; Hamid, R; Çelik, M; Özen, G; Izmailov, A Ch

    2014-11-30

    We have detected and analysed narrow high-contrast coherent population trapping (CPT) resonances, which are induced in absorption of a weak monochromatic probe light beam by counterpropagating two-frequency pump radiation in a cell with rarefied caesium vapour. The experimental investigations have been performed by the example of nonclosed three level Λ-systems formed by spectral components of the D{sub 2} line of caesium atoms. The applied method allows one to analyse features of the CPT phenomenon directly at a given low long-lived level of the selected Λ-system even in sufficiently complicated spectra of atomic gases with large Doppler broadening. We have established that CPT resonances in transmission of the probe beam exhibit not only a higher contrast but also a much lesser width in comparison with well- known CPT resonances in transmission of the corresponding two-frequency pump radiation. The results obtained can be used in selective photophysics, photochemistry and ultra-high resolution atomic (molecular) spectroscopy. (laser applications and other topics in quantum electronics)

  5. An all-fiber image-reject homodyne coherent Doppler wind lidar.

    PubMed

    Abari, Cyrus F; Pedersen, Anders T; Mann, Jakob

    2014-10-20

    In this paper, we present an alternative approach to the down-conversion (translation) of the received optical signals collected by the antenna of an all-fiber coherent Doppler lidar (CDL). The proposed method, widely known as image-reject, quadrature detection, or in-phase/quadrature-phase detection, utilizes the advances in fiber optic communications such that the received signal can be optically down-converted into baseband where not only the radial velocity but also the direction of the movement can be inferred. In addition, we show that by performing a cross-spectral analysis, enabled by the presence of two independent signal observations with uncorrelated noise, various noise sources can be suppressed and a more simplified velocity estimation algorithm can be employed in the spectral domain. Other benefits of this architecture include, but are not limited to, a more reliable measurement of radial velocities close to zero and an improved bandwidth. The claims are verified through laboratory implementation of a continuous wave CDL, where measurements both on a hard and diffuse target have been performed and analyzed.

  6. Coherent Doppler lidar observation and numerical simulation of gap wind Kiyokawa-dashi in Japan

    NASA Astrophysics Data System (ADS)

    Sasaki, K.; Ishii, S.; Mizutani, K.; Kanno, H.; Matsushima, D.; Sha, W.; Iwasaki, T.

    2006-12-01

    This study presents the coherent Doppler lidar (CDL) observations and numerical simulations of local strong easterly wind Kiyokawa-dashi, which is most famous gap wind in Japan. Main goal of this study is to clarify the three dimensional structure and dynamics of Kiyokawa-dashi under the different synoptic situations. Observations were conducted in August 29 and 30, 2004. A 2μm eye-safe airborne CDL developed by the National Institute of Information and Communications Technology (NICT) established at the exit of the narrow valley of Mogami-River. The vertical scanning of CDL with the velocity-azimuth display technique shows that the easterly wind was confined below 600 m, which is almost same or slightly lower than the crest, and accelerated at the down stream side. The upper layer above the easterly wind was weak westerly and these vertical structures were common to the all of the events. Horizontal scanning sounds the line-of-sight (LOS) wind velocity up to 6 km of downstream and presents detailed temporal wind shift within 5-10 minutes. Numerical simulations have been performed with non hydrostatic atmospheric model (MRINPD NHM) with horizontal grid spacing down to 1 km. Many of the observed structures were realistically simulated, but it still has a bias that the detailed temporal evolution wasn't shown in the numerical simulation. The CDL captured the fine structure and temporal variations of Kiyokawa-dashi. It is a powerful and useful system for studying the wind field.

  7. A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar.

    PubMed

    Hyun, Eugin; Jin, Young-Seok; Lee, Jong-Hun

    2016-01-20

    For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW) radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT) is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method.

  8. A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar

    PubMed Central

    Hyun, Eugin; Jin, Young-Seok; Lee, Jong-Hun

    2016-01-01

    For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW) radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT) is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method. PMID:26805835

  9. Staging of Macular Telangiectasia: Power-Doppler Optical Coherence Tomography and Macular Pigment Optical Density

    PubMed Central

    Chin, Eric K.; Kim, Dae Yu; Hunter, Allan A.; Pilli, Suman; Wilson, Machelle; Zawadzki, Robert J.; Werner, John S.; Park, Susanna S.

    2013-01-01

    Purpose. Two methods were used to study the stages of macular telangiectasia (MacTel): Power-Doppler optical coherence tomography (PD-OCT), which allows imaging of the retinal circulation in three dimensions, and macular pigment optical density (MPOD), which quantifies the distribution of macular carotenoids. Methods. Among 49 patients with MacTel identified, 12 eyes (6 patients) with MacTel and 7 age-matched control eyes (7 patients) were imaged with a custom-built Fourier-domain OCT instrument to acquire PD-OCT images. MPOD was measured using heterochromatic flicker photometry in 10 eyes (5 patients) with MacTel and compared with 44 age-matched control eyes (44 patients). Clinical staging of MacTel was based on best-corrected visual acuity, fundus biomicroscopy, fluorescein angiography, and OCT. Results. Stage 1 eyes (n = 2) had subtle punctate vascular signal confined to the inner portion of the outer plexiform layer (OPL) on PD-OCT. Stage 2 (n = 2) showed larger oblique vascular signal extending into deeper OPL. Stage 3 (n = 5) had disruption of outer retinal layers with abnormal vasculature extending into the outer nuclear layer. Stage 4 (n = 3) showed diffuse blurring of the retinal layers with vascular channels extending the full thickness of the retina. MPOD values in four eyes with stage 1 or 2 MacTel correlated well with age-matched controls. Six eyes with stage 3 or 4 MacTel had loss of MPOD especially at the fovea. Conclusions. PD-OCT shows penetration of the retinal capillaries into the deeper retinal layers in early stages of MacTel, with full thickness vascular proliferation in advanced disease. MPOD is commonly depleted but may appear normal in early stage MacTel. PMID:23716628

  10. High-speed swept source optical coherence Doppler tomography for deep brain microvascular imaging

    NASA Astrophysics Data System (ADS)

    Chen, Wei; You, Jiang; Gu, Xiaochun; Du, Congwu; Pan, Yingtian

    2016-12-01

    Noninvasive microvascular imaging using optical coherence Doppler tomography (ODT) has shown great promise in brain studies; however, high-speed microcirculatory imaging in deep brain remains an open quest. A high-speed 1.3 μm swept-source ODT (SS-ODT) system is reported which was based on a 200 kHz vertical-cavity-surface-emitting laser. Phase errors induced by sweep-trigger desynchronization were effectively reduced by spectral phase encoding and instantaneous correlation among the A-scans. Phantom studies have revealed a significant reduction in phase noise, thus an enhancement of minimally detectable flow down to 268.2 μm/s. Further in vivo validation was performed, in which 3D cerebral-blood-flow (CBF) networks in mouse brain over a large field-of-view (FOV: 8.5 × 5 × 3.2 mm3) was scanned through thinned skull. Results showed that fast flows up to 3 cm/s in pial vessels and minute flows down to 0.3 mm/s in arterioles or venules were readily detectable at depths down to 3.2 mm. Moreover, the dynamic changes of the CBF networks elicited by acute cocaine such as heterogeneous responses in various vessel compartments and at different cortical layers as well as transient ischemic events were tracked, suggesting the potential of SS-ODT for brain functional imaging that requires high flow sensitivity and dynamic range, fast frame rate and a large FOV to cover different brain regions.

  11. High-speed swept source optical coherence Doppler tomography for deep brain microvascular imaging

    PubMed Central

    Chen, Wei; You, Jiang; Gu, Xiaochun; Du, Congwu; Pan, Yingtian

    2016-01-01

    Noninvasive microvascular imaging using optical coherence Doppler tomography (ODT) has shown great promise in brain studies; however, high-speed microcirculatory imaging in deep brain remains an open quest. A high-speed 1.3 μm swept-source ODT (SS-ODT) system is reported which was based on a 200 kHz vertical-cavity-surface-emitting laser. Phase errors induced by sweep-trigger desynchronization were effectively reduced by spectral phase encoding and instantaneous correlation among the A-scans. Phantom studies have revealed a significant reduction in phase noise, thus an enhancement of minimally detectable flow down to 268.2 μm/s. Further in vivo validation was performed, in which 3D cerebral-blood-flow (CBF) networks in mouse brain over a large field-of-view (FOV: 8.5 × 5 × 3.2 mm3) was scanned through thinned skull. Results showed that fast flows up to 3 cm/s in pial vessels and minute flows down to 0.3 mm/s in arterioles or venules were readily detectable at depths down to 3.2 mm. Moreover, the dynamic changes of the CBF networks elicited by acute cocaine such as heterogeneous responses in various vessel compartments and at different cortical layers as well as transient ischemic events were tracked, suggesting the potential of SS-ODT for brain functional imaging that requires high flow sensitivity and dynamic range, fast frame rate and a large FOV to cover different brain regions. PMID:27934907

  12. A comparison of two embedded programming techniques for high rep rate coherent Doppler lidars

    NASA Astrophysics Data System (ADS)

    Arend, Mark F.; Abdelazim, Sameh; Lopez, Miguel; Moshary, Fred

    2013-05-01

    Two FPGA embedded programming approaches are considered and compared for a 20 kHz pulse repetition rate coherent Doppler lidar system which acquires return signals at 400 Msamples/second and operates with signal to noise ratios as low as -20 dB. In the first approach, the acquired return signal is gated in time and the square modulus of the fast Fourier transform is accumulated for each of the range gates, producing a series of power spectra as a function of range. Wind speed decisions based on numerical estimators can then be made after transferring the range gated accumulated power spectra to a host computer, enabling the line of sight wind speed as a function of range gate to be calculated and stored for additional processing. In the second FPGA approach, a digital IQ demodulator and down sampler reduces the data flow requirements so that an autocorrelation matrix representing a pre-selected number of lags can be accumulated, allowing for the process of range gating to be explored on the host computer. The added feature of the second approach is that it allows for an additional capability to adjust the range gate period dynamically as the state of the atmospheric boundary layer (e.g. backscatter coefficient and stability condition) changes. A simple manual beam scanning technique is used to calculate the wind field vector which is graphically displayed on time-height cross section plots. A comparison to other observed and modeled information is presented suggesting the usefulness for the characterization of microscale meteorology.

  13. AR (Autoregressive) Modeling of Coherence in Time Delay and Doppler Estimation

    DTIC Science & Technology

    1988-12-01

    Authoriy 3 Distribution Availabilhtv of Report 2b Declassifica’ion Downgrading Schedule Approved for public release: distribution is unlimited. 4 Performira...2 C. COHERENCE ESTIMATION ................................. 3 D. COHERENCE OF NARROW BAND SIGNALS WITH DIFFERENTIAL TIME DELAY AND DIFFERENTIAL...5 Figure 2. Coherence estimation block diagram (reinterpretation) ............. 5 Figure 3 . Coherence estimation block diagram using the FFT

  14. Assessment of total retinal blood flow using Doppler Fourier Domain Optical Coherence Tomography during systemic hypercapnia and hypocapnia.

    PubMed

    Shahidi, Ayda M; Patel, Sunni R; Huang, David; Tan, Ou; Flanagan, John G; Hudson, Chris

    2014-07-01

    The purpose of this study was to investigate changes in total retinal blood flow (RBF) using Doppler Fourier Domain Optical Coherence Tomography (Doppler FD-OCT) in response to the manipulation of systemic partial pressure of CO2 (PETCO2). Double circular Doppler blood flow scans were captured in nine healthy individuals (mean age ± standard deviation: 27.1 ± 4.1, six males) using the RTVue(™) FD-OCT (Optovue). PETCO2 was manipulated using a custom-designed computer-controlled gas blender (RespirAct(™)) connected to a sequential gas delivery rebreathing circuit. Doppler FD-OCT measurements were captured at baseline, during stages of hypercapnia (+5/+10/+15 mmHg PETCO2), return to baseline and during stages of hypocapnia (-5/-10/-15 mmHg PETCO2). Repeated measures analysis of variance (reANOVA) and Tukey's post hoc analysis were used to compare Doppler FD-OCT measurements between the various PETCO2 levels relative to baseline. The effect of PETCO2 on TRBF was also investigated using linear regression models. The average RBF significantly increased by 15% (P < 0.0001) with an increase in PETCO2 and decreased significantly by 10% with a decrease in PETCO2 (P = 0.001). Venous velocity significantly increased by 3.11% from baseline to extreme hypercapnia (P < 0.001) and reduced significantly by 2.01% at extreme hypocapnia (P = 0.012). No significant changes were found in the average venous area measurements under hypercapnia (P = 0.36) or hypocapnia (P = 0.40). Overall, increased and decreased PETCO2 values had a significant effect on RBF outcomes (P < 0.002). In healthy individuals, altered end-tidal CO2 levels significantly changed RBF as measured by Doppler FD-OCT. © 2014 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

  15. Design study for a spatial heterodyne Doppler coherence imaging system for flow measurements on NSTX-U

    NASA Astrophysics Data System (ADS)

    Schwartz, Jacob; Jaworski, M. A.; Diallo, A.; Kaita, R.; Nichols, J. H.

    2015-11-01

    Measuring the flow of impurities in the SOL of NSTX-U can lead to understanding of main ion flow and heat transport. Spatial heterodyne Doppler coherence imaging is a technique that allows a single camera frame to record both the brightness and Doppler shift of an emitted spectral line over the entire field of view. With a tangential view on NSTX-U it is possible to tomographically reconstruct 2d (r-z) profiles of emissivity and flow velocity for an imaged impurity ion by assuming axisymmetry and field-aligned flow. One can derive the main ion parallel flow velocity by making four measurements and using additional assumptions. Imaging of two spectral lines each from two ion species allows solving for ne, Te, and the density of the two ion species by using ADAS emissivity tables. Since measurements of the velocity of two impurities are planned, it is possible to derive a main ion parallel velocity by using a reconstructed ni and Ti (from other diagnostics), a 1d conduction-limited SOL model, and a 1d model of forces on impurities. With fewer than four measurements, it is possible to derive the main ion velocity if the impurities are entrained in the flow. A design study for such a spatial heterodyne Doppler coherence imaging system on NSTX-U will be presented. Supported by U.S. DOE Contract No. DE-AC02-09CH11466.

  16. Aerosol backscatter measurements at 10.6 microns with airborne and ground-based CO2 Doppler lidars over the Colorado High Plains. II - Backscatter structure

    NASA Technical Reports Server (NTRS)

    Bowdle, David A.; Rothermel, Jeffry; Vaughan, J. Michael; Post, Madison J.

    1991-01-01

    Measurements of tropospheric aerosol volume backscatter coefficients at 10.6-microns wavelength were obtained with airborne continuous wave and ground-based pulsed CO2 Doppler lidars over the Colorado High Plains during a 20-day period in summer 1982. A persistent 'background' layer was found between 6- and 10-km altitude, with a generally uniform backscatter mixing ratio of about 10 to the -10th sq m/kg per sr. The upper boundary of this background layer varied with the tropopause height; the lower boundary varied with the strength and diurnal cycle of convective mixing in the planetary boundary layer (PBL). For quiescent meteorological conditions, the transition from the PBL to the background layer was usually very sharp, with backscatter decreases sometimes as large as 3 decades in about 70 m. Sharp gradients were also found at the boundaries of shallow (tens of meters) subvisible cirrus clouds. For less stable conditions, associated with vertical aerosol transport by deep cumuliform clouds, backscatter tended to decrease exponentially with altitude.

  17. In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

    PubMed Central

    Blatter, Cedric; Meijer, Eelco F. J.; Nam, Ahhyun S.; Jones, Dennis; Bouma, Brett E.; Padera, Timothy P.; Vakoc, Benjamin J.

    2016-01-01

    Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence tomography platform that allows direct, label-free quantification of lymph velocity and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph velocity at sufficiently high temporal resolution to resolve the dynamic pulsatile flow in collecting lymphatic vessels. PMID:27377852

  18. In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Blatter, Cedric; Meijer, Eelco F. J.; Nam, Ahhyun S.; Jones, Dennis; Bouma, Brett E.; Padera, Timothy P.; Vakoc, Benjamin J.

    2016-07-01

    Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence tomography platform that allows direct, label-free quantification of lymph velocity and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph velocity at sufficiently high temporal resolution to resolve the dynamic pulsatile flow in collecting lymphatic vessels.

  19. Quantification of optical Doppler broadening and optical path lengths of multiply scattered light by phase modulated low coherence interferometry

    NASA Astrophysics Data System (ADS)

    Varghese, B.; Rajan, V.; van Leeuwen, T. G.; Steenbergen, W.

    2007-07-01

    We show experimental validation of a novel technique to measure optical path length distributions and path length resolved Doppler broadening in turbid media for different reduced scattering coefficients and anisotropies. The technique involves a phase modulated low coherence Mach-Zehnder interferometer, with separate fibers for illumination and detection. Water suspensions of Polystyrene microspheres with high scattering and low absorption levels are used as calibrated scattering phantoms. The path length dependent diffusion broadening or Doppler broadening of scattered light is shown to agree with Diffusive Wave Spectroscopy within 5%. The optical path lengths are determined experimentally from the zero order moment of the phase modulation peak around the modulation frequency in the power spectrum and the results are validated with Monte Carlo simulations.

  20. Quantification of optical Doppler broadening and optical path lengths of multiply scattered light by phase modulated low coherence interferometry.

    PubMed

    Varghese, B; Rajan, V; van Leeuwen, T G; Steenbergen, W

    2007-07-23

    We show experimental validation of a novel technique to measure optical path length distributions and path length resolved Doppler broadening in turbid media for different reduced scattering coefficients and anisotropies. The technique involves a phase modulated low coherence Mach-Zehnder interferometer, with separate fibers for illumination and detection. Water suspensions of Polystyrene microspheres with high scattering and low absorption levels are used as calibrated scattering phantoms. The path length dependent diffusion broadening or Doppler broadening of scattered light is shown to agree with Diffusive Wave Spectroscopy within 5%. The optical path lengths are determined experimentally from the zero order moment of the phase modulation peak around the modulation frequency in the power spectrum and the results are validated with Monte Carlo simulations.

  1. Distribution of mean Doppler shift, spectral width, and skewness of coherent 50-MHz auroral radar backscatter

    SciTech Connect

    Watermann, J.; McNamara, A.G. ); Sofko, G.J.; Koehler, J.A. )

    1989-06-01

    Some 7,700 radio aurora spectra obtained from a six link 50-MHz CW radar network set up on the Canadian prairies were analyzed with respect to the distributions of mean Doppler shift, spectral width and skewness. A comparison with recently published SABRE results obtained at 153 MHz shows substantial differences in the distributions which are probably due to different experimental and geophysical conditions. The spectra are mostly broad with mean Doppler shifts close to zero (type II spectra). The typical groupings of type I and type III spectra are clearly identified. All types appear to be in general much more symmetric than those recorded with SABRE, and the skewness is only weakly dependent on the sign of the mean Doppler shift. Its distribution peaks near zero and shows a weak positive correlation with the type II Doppler shifts while the mostly positive type I Doppler shifts are slightly negatively correlated with the skewness.

  2. Separation of Coherent and Incoherent Scattering Components from Delay/Doppler Altimeter Waveforms over Sea-Ice

    NASA Astrophysics Data System (ADS)

    Egido, A.; Smith, W. H. F.

    2015-12-01

    One of the main benefits of the delay-Doppler altimeter (DDA) is the improved resolution of the system along the satellite track. By means of an unfocussed Synthetic Aperture Radar (SAR) processing technique, the altimeter footprint along the flight direction can be reduced by an order of magnitude with respect to conventional altimeters. However, with the delay-Doppler processing the resolution improvement occurs only on the along-track direction, while the across-track direction remains pulse-limited. The result is an elongated footprint perpendicular to the satellite flight path. The combination of the effects of several scatterers within the footprint can lead to random variations of the DDA waveforms, preventing conventional retracking techniques from retrieving geophysical parameters from altimeter data. This is particularly significant in the case of sea ice, where the coherent response from leads can completely exceed the response from the actual ice surface. We have developed a processing technique that allows the separation of the coherent and incoherent scattering components from SAR altimetry waveforms. The technique is similar to the one used in imaging SAR systems, and is based in the exploitation of the phase history of coherent targets during their illumination period with the antenna beam. For the development of the technique we have used the CryoSat-2 SAR Mode data. The starting point of our processing is the full bit rate (FBR) I/Q complex echo samples. By accounting for the phase evolution of the static targets in the scene, it is possible to correct the phase of the FBR complex echoes along the aperture, which allows to perform an inter-burst coherent averaging, potentially, as long as the target illumination time. This reduces the incoherent components of the radar signal, which results in a radar waveform that contains only the coherent scattering component. The coherent component can later be removed from the original delay-Doppler waveform

  3. Lab Demonstration of the Hybrid Doppler Wind Lidar (HDWL) Transceiver

    NASA Technical Reports Server (NTRS)

    Marx, Catherine T.; Gentry, Bruce; Jordan, Patrick; Dogoda, Peter; Faust, Ed; Kavaya, Michael

    2013-01-01

    The recommended design approach for the 3D Tropospheric Winds mission is a hybrid Doppler lidar which combines the best elements of both a coherent aerosol Doppler lidar operating at 2 micron and a direct detection molecular Doppler lidar operating at 0.355 micron. In support of the mission, we built a novel, compact, light-weighted multi-field of view transceiver where multiple telescopes are used to cover the required four fields of view. A small mechanism sequentially selects both the "transmit" and "receive" fields of view. The four fields are combined to stimulate both the 0.355 micron receiver and the 2 micron receiver. This version is scaled (0.2 micron diameter aperture) from the space-based version but still demonstrates the feasibility of the hybrid approach. The primary mirrors were conventionally light-weighted and coated with dielectric, high reflectivity coatings with high laser damage thresholds at both 2 micron and 0.355 micron. The mechanical structure and mounts were fabricated from composites to achieve dimensional stability while significantly reducing the mass. In the laboratory, we demonstrated the system level functionality at 0.355 micron and at 2 micron raising the Technology Readiness Level (TRL) from 2 to 4.

  4. Method of radial velocities for the estimation of aircraft wake vortex parameters from data measured by coherent Doppler lidar.

    PubMed

    Smalikho, I N; Banakh, V A; Holzäpfel, F; Rahm, S

    2015-09-21

    The method of radial velocities (RV) is applied to estimate aircraft wake vortex parameters from measurements conducted with pulsed coherent Doppler lidar (PCDL). Operations of the Stream Line lidar and the 2-µm PCDL are simulated numerically to analyze the accuracy of the estimated wake vortex parameters with the RV method. The RV method is also used to estimate wake vortex trajectories and circulation from lidar measurements at Tomsk and Munich airports. The method of velocity envelopes and the RV method are compared employing data gathered with the 2-µm PCDL. The domain of applicability of the RV method is determined.

  5. Doppler Optical Coherence Tomography Signals: Analysis in Low and High Scattering Media

    NASA Astrophysics Data System (ADS)

    Bykov, Alexander V.; Kalkman, Jeroen

    In this chapter, Doppler OCT signals (OCT magnitude and flow velocity profile) for low and high scattering media are analyzed. For low scattering media, we demonstrate the use of the single scattering model to determine the optical properties of the sample. For high scattering media, the effects of multiple scattering are stronger and the single scattering description breaks down. An alternative approach, based on Monte Carlo simulations, is proposed as it gives a more appropriate description of the Doppler OCT signal by taking into account multiple scattering effects. Using Monte Carlo simulations, we analyze the deviation of the OCT slope from the value predicted by the single scattering model and analyze the distortions in the measured Doppler OCT flow profile. Monte Carlo simulations are compared to Doppler OCT measurements for Intralipid and blood.

  6. Grader learning effect and reproducibility of Doppler Spectral-Domain Optical Coherence Tomography derived retinal blood flow measurements.

    PubMed

    Rose, Kalpana; Jong, Monica; Yusof, Firdaus; Tayyari, Faryan; Tan, Ou; Huang, David; Sadda, Srinivas R; Flanagan, John G; Hudson, Christopher

    2014-12-01

    To investigate grader learning effect and to quantify intergrader reproducibility of Doppler Spectral-Domain Optical Coherence Tomography (SD-OCT) derived retinal blood flow measurements. Fifteen healthy young subjects (mean age 28.44; SD 3 years) underwent Doppler SD-OCT scans of one eye using the circumpapillary double circular scan protocol of the Optovue RTVue by one of two experienced operators. One trained (i.e. having undergone certification) and one novice (i.e. preliminary training comprising five standard practice data sets) individual then graded a standardized set of scans, consisting of 15 data sets (session 1) using custom Doppler Optical Coherence Tomography of Retinal Circulation (DOCTORC) software. One week later (session 2), the novice grader underwent further training by grading an additional 15 practice data sets and then both graders subsequently regraded the original 15 data sets. Measurements achieved by a novice grader during session 1 showed a trend to be higher in terms of total retinal venous blood flow (TRBF) and also to be significantly (p = 0.03) higher for venous area, compared with a trained grader. Session 2 results were not significantly different for either grader. The mean TRBF for session 2 for the trained and novice grader was 45.29 ± 9.28 μl/min and 44.39 ± 7.36 μl/min, respectively. The coefficient of repeatability (COR) of session 2 TRBF values between the trained and novice grader was 8.09 μl/min. There is a grader learning effect which impacts the venous area measurements. Reproducible and repeatable retinal blood flow measurements were achieved among trained graders using DOCTORC software. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  7. Application of non-coherent Doppler data types for deep space navigation

    NASA Technical Reports Server (NTRS)

    Bhaskaran, Shyam

    1995-01-01

    Recent improvements in computational capability and Deep Space Network technology have renewed interest in examining the possibility of using one-way Doppler data alone to navigate interplanetary spacecraft. The one-way data can be formulated as the standard differenced-count Doppler or as phase measurements, and the data can be received at a single station or differenced if obtained simultaneously at two stations. A covariance analysis is performed which analyzes the accuracy obtainable by combinations of one-way Doppler data and compared with similar results using standard two-way Doppler and range. The sample interplanetary trajectory used was that of the Mars Pathfinder mission to Mars. It is shown that differenced one-way data is capable of determining the angular position of the spacecraft to fairly high accuracy, but has relatively poor sensitivity to the range. When combined with single station data, the position dispersions are roughly an order of magnitude larger in range and comparable in angular position as compared to dispersions obtained with standard data two-way types. It was also found that the phase formulation is less sensitive to data weight variations and data coverage than the differenced-count Doppler formulation.

  8. Lab Demonstration of the Hybrid Doppler Wind Lidar (HDWL) Transceiver

    NASA Technical Reports Server (NTRS)

    Marx, Catherine T.; Gentry, Bruce; Jordan, Patrick; Dogoda, Peter; Faust, Ed; Kavaya, Michael

    2013-01-01

    The recommended design approach for the 3D Tropospheric Winds mission is a hybrid Doppler lidar which combines the best elements of both a coherent aerosol Doppler lidar operating at 2 microns and a direct detection molecular Doppler lidar operating at 0.355 microns. In support of the mission, we built a novel, compact, light-weighted multi-field of view transceiver where multiple telescopes are used to cover the required four fields of view. A small mechanism sequentially selects both the "transmit" and "receive" fields of view. The four fields are combined to stimulate both the 0.355 micron receiver and the 2 micron receiver. This version is scaled (0.2 m diameter aperture) from the space-based version but still demonstrates the feasibility of the hybrid approach. The primary mirrors were conventionally light-weighted and coated with dielectric, high reflectivity coatings with high laser damage thresholds at both 2 microns and 0.355 microns. The mechanical structure and mounts were fabricated from composites to achieve dimensional stability while significantly reducing the mass. In the laboratory, we demonstrated the system level functionality at 0.355 microns and at 2 microns, raising the Technology Readiness Level (TRL) from 2 to 4.

  9. Application of short-range dual-Doppler lidars to evaluate the coherence of turbulence

    NASA Astrophysics Data System (ADS)

    Cheynet, Etienne; Jakobsen, Jasna Bogunović; Snæbjörnsson, Jónas; Mikkelsen, Torben; Sjöholm, Mikael; Mann, Jakob; Hansen, Per; Angelou, Nikolas; Svardal, Benny

    2016-12-01

    Two synchronized continuous wave scanning lidars are used to study the coherence of the along-wind and across-wind velocity components. The goal is to evaluate the potential of the lidar technology for application in wind engineering. The wind lidars were installed on the Lysefjord Bridge during four days in May 2014 to monitor the wind field in the horizontal plane upstream of the bridge deck. Wind records obtained by five sonic anemometers mounted on the West side of the bridge are used as reference data. Single- and two-point statistics of wind turbulence are studied, with special emphasis on the root-coherence and the co-coherence of turbulence. A four-parameter decaying exponential function has been fitted to the measured co-coherence, and a good agreement is observed between data obtained by the sonic anemometers and the lidars. The root-coherence of turbulence is compared to theoretical models. The analytical predictions agree rather well with the measured coherence for the along-wind component. For increasing wavenumbers, larger discrepancies are, however, noticeable between the measured coherence and the theoretical predictions. The WindScanners are observed to slightly overestimate the integral length scales, which could not be explained by the laser beam averaging effect alone. On the other hand, the spatial averaging effect does not seem to have any significant effect on the coherence.

  10. Doppler effect's contribution to ultrasonic modulation of multiply scattered coherent light: Monte Carlo modeling.

    PubMed

    Elazar, Jovan M; Steshenko, Oleg

    2008-01-15

    Modulation of light by ultrasound in turbid media is investigated by modified public domain software based on the Monte Carlo algorithm. Apart from the recognized modulation mechanisms, originating in scatterers' displacements and refractive index modulation, an additional mechanism, evolving from Doppler shift during photon scattering, is considered. Comparison of the relative contributions from all three mechanisms to light modulation by ultrasound is performed for different medium scattering properties and ultrasound frequencies. Refractive index modulation remains the strongest mechanism for light modulation by ultrasound, but for high ultrasound frequencies and for large scattering coefficients the Doppler effect can become dominant.

  11. Calibration of the reflectance of hard targets for a coherent Doppler lidar

    NASA Technical Reports Server (NTRS)

    Anderson, Richard; Bilbro, James W.

    1988-01-01

    Data on the bihemispherical and directional-hemispherical reflectance were measured on a gold standard, a flowers of sulfur secondary standard, glass bead blasted aluminum, and 120 grade aluminum oxide sandpaper. These reflectances were measured for the P(24) and P(20) 10-micron and R(26), R(20), and P(20) 9-micron CO2 lines. The specular and retroreflection character of scattering from aluminum and sandpaper was evident in the measurements. The results agree reasonably well with previous measurements. Also when the sphere is irradiated with polarized light no difference was noted in the reflectance, which indicates that the integrating sphere is a depolarizer.

  12. Live imaging of rat embryos with Doppler swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Larina, Irina V.; Furushima, Kenryo; Dickinson, Mary E.; Behringer, Richard R.; Larin, Kirill V.

    2009-09-01

    The rat has long been considered an excellent system to study mammalian embryonic cardiovascular physiology, but has lacked the extensive genetic tools available in the mouse to be able to create single gene mutations. However, the recent establishment of rat embryonic stem cell lines facilitates the generation of new models in the rat embryo to link changes in physiology with altered gene function to define the underlying mechanisms behind congenital cardiovascular birth defects. Along with the ability to create new rat genotypes there is a strong need for tools to analyze phenotypes with high spatial and temporal resolution. Doppler OCT has been previously used for 3-D structural analysis and blood flow imaging in other model species. We use Doppler swept-source OCT for live imaging of early postimplantation rat embryos. Structural imaging is used for 3-D reconstruction of embryo morphology and dynamic imaging of the beating heart and vessels, while Doppler-mode imaging is used to visualize blood flow. We demonstrate that Doppler swept-source OCT can provide essential information about the dynamics of early rat embryos and serve as a basis for a wide range of studies on functional evaluation of rat embryo physiology.

  13. Live imaging of rat embryos with Doppler swept-source optical coherence tomography

    PubMed Central

    Larina, Irina V.; Furushima, Kenryo; Dickinson, Mary E.; Behringer, Richard R.; Larin, Kirill V.

    2009-01-01

    The rat has long been considered an excellent system to study mammalian embryonic cardiovascular physiology, but has lacked the extensive genetic tools available in the mouse to be able to create single gene mutations. However, the recent establishment of rat embryonic stem cell lines facilitates the generation of new models in the rat embryo to link changes in physiology with altered gene function to define the underlying mechanisms behind congenital cardiovascular birth defects. Along with the ability to create new rat genotypes there is a strong need for tools to analyze phenotypes with high spatial and temporal resolution. Doppler OCT has been previously used for 3-D structural analysis and blood flow imaging in other model species. We use Doppler swept-source OCT for live imaging of early postimplantation rat embryos. Structural imaging is used for 3-D reconstruction of embryo morphology and dynamic imaging of the beating heart and vessels, while Doppler-mode imaging is used to visualize blood flow. We demonstrate that Doppler swept-source OCT can provide essential information about the dynamics of early rat embryos and serve as a basis for a wide range of studies on functional evaluation of rat embryo physiology. PMID:19895102

  14. Atmospheric correlation-time measurements and effects on coherent Doppler lidar

    NASA Technical Reports Server (NTRS)

    Ancellet, Gerard M.; Menzies, Robert T.

    1987-01-01

    The time for which the backscatter from an ensemble of atmospheric aerosol particles remains coherent was studied by using a pulsed TEA CO2 lidar with coherent detection. Experimental results are compared with predictions by using model pulse shapes appropriate for TEA CO2 laser transmitters. The correlation time of the backscatter return signal is important in studies of atmospheric turbulence and its effects on optical propagation and backscatter. Techniques for its measurement are discussed and evaluated.

  15. Visualisation of the oscillation dynamics of cytoplasm in a living cell of Physarum mixomycete plasmodium by the method of optical coherence Doppler tomography

    SciTech Connect

    Bykov, A V; Priezzhev, A V; Lauri, J; Myllylae, Risto

    2009-04-30

    The method of optical coherence Doppler tomography is used for the first time to visualise the oscillatory amoeboid mobility in strands of Physarum polycephalum mixomycete plasmodium and to record periodic radial contractions of the strands and spatiotemporal variations in the velocity of the cytoplasmic flow inside them. (laser biology)

  16. Visualisation of the oscillation dynamics of cytoplasm in a living cell of Physarum mixomycete plasmodium by the method of optical coherence Doppler tomography

    NASA Astrophysics Data System (ADS)

    Bykov, A. V.; Priezzhev, A. V.; Lauri, J.; Myllylä, Risto

    2009-04-01

    The method of optical coherence Doppler tomography is used for the first time to visualise the oscillatory amoeboid mobility in strands of Physarum polycephalum mixomycete plasmodium and to record periodic radial contractions of the strands and spatiotemporal variations in the velocity of the cytoplasmic flow inside them.

  17. Multimodal reconstruction of microvascular-flow distributions using combined two-photon microscopy and Doppler optical coherence tomography

    PubMed Central

    Gagnon, Louis; Sakadžić, Sava; Lesage, Fréderic; Mandeville, Emiri T.; Fang, Qianqian; Yaseen, Mohammad A.; Boas, David A.

    2015-01-01

    Abstract. Computing microvascular cerebral blood flow (μCBF) in real cortical angiograms is challenging. Here, we investigated whether the use of Doppler optical coherence tomography (DOCT) flow measurements in individual vessel segments can help in reconstructing μCBF across the entire vasculature of a truncated cortical angiogram. A μCBF computational framework integrating DOCT measurements is presented. Simulations performed on a synthetic angiogram showed that the addition of DOCT measurements, especially close to large inflowing or outflowing vessels, reduces the impact of pressure boundary conditions and estimated vessel resistances resulting in a more accurate reconstruction of μCBF. Our technique was then applied to reconstruct microvascular flow distributions in the mouse cortex down to 660  μm by combining two-photon laser scanning microscopy angiography with DOCT. PMID:26157987

  18. Multimodal reconstruction of microvascular-flow distributions using combined two-photon microscopy and Doppler optical coherence tomography.

    PubMed

    Gagnon, Louis; Sakadžić, Sava; Lesage, Fréderic; Mandeville, Emiri T; Fang, Qianqian; Yaseen, Mohammad A; Boas, David A

    2015-01-01

    Computing microvascular cerebral blood flow ([Formula: see text]) in real cortical angiograms is challenging. Here, we investigated whether the use of Doppler optical coherence tomography (DOCT) flow measurements in individual vessel segments can help in reconstructing [Formula: see text] across the entire vasculature of a truncated cortical angiogram. A [Formula: see text] computational framework integrating DOCT measurements is presented. Simulations performed on a synthetic angiogram showed that the addition of DOCT measurements, especially close to large inflowing or outflowing vessels, reduces the impact of pressure boundary conditions and estimated vessel resistances resulting in a more accurate reconstruction of [Formula: see text]. Our technique was then applied to reconstruct microvascular flow distributions in the mouse cortex down to [Formula: see text] by combining two-photon laser scanning microscopy angiography with DOCT.

  19. High-flow-velocity and shear-rate imaging by use of color Doppler optical coherence tomography.

    PubMed

    van Leeuwen, T G; Kulkarni, M D; Yazdanfar, S; Rollins, A M; Izatt, J A

    1999-11-15

    Color Doppler optical coherence tomography (CDOCT) is capable of precise velocity mapping in turbid media. Previous CDOCT systems based on the short-time Fourier transform have been limited to maximum flow velocities of the order of tens of millimeters per second. We describe a technique, based on interference signal demodulation at multiple frequencies, to extend the physiological relevance of CDOCT by increasing the dynamic range of measurable velocities to hundreds of millimeters per second. The physiologically important parameter of shear rate is also derived from CDOCT measurements. The measured flow-velocity profiles and shear-rate distributions correlate very well with theoretical predictions. The multiple demodulation technique, therefore, may be useful to monitor blood flow in vivo and to identify regions with high and low shear rates.

  20. Three-beam Doppler optical coherence tomography using a facet prism telescope and MEMS mirror for improved transversal resolution.

    PubMed

    Haindl, R; Trasischker, W; Baumann, B; Pircher, M; Hitzenberger, C K

    An improved three-beam Doppler optical coherence tomography system was developed. It utilizes a custom-made three-facet prism telescope to improve the transversal resolution at the sample. Furthermore, a two-axis gimbal-less MEMS mirror is used to minimize off-pivot beam movement at the pupil of the eye, enabling circular scanning for in vivo retinal measurements. We demonstrate the system's abilities for in vitro circular scanning to measure absolute flow and to reconstruct the full velocity vector on a bifurcation flow phantom. Moreover, in vivo retinal measurements using circular scanning around vessel bifurcations of healthy human volunteers were performed. Measurements of the absolute mean flow and its orientation are in good agreement with the expected values for in vitro measurements. For in vivo measurements, the in- and outflow of blood for retinal vessel bifurcations show an excellent agreement, demonstrating the reliability of the technique.

  1. Three-beam Doppler optical coherence tomography using a facet prism telescope and MEMS mirror for improved transversal resolution

    NASA Astrophysics Data System (ADS)

    Haindl, R.; Trasischker, W.; Baumann, B.; Pircher, M.; Hitzenberger, C. K.

    2015-12-01

    An improved three-beam Doppler optical coherence tomography system was developed. It utilizes a custom-made three-facet prism telescope to improve the transversal resolution at the sample. Furthermore, a two-axis gimbal-less MEMS mirror is used to minimize off-pivot beam movement at the pupil of the eye, enabling circular scanning for in vivo retinal measurements. We demonstrate the system's abilities for in vitro circular scanning to measure absolute flow and to reconstruct the full velocity vector on a bifurcation flow phantom. Moreover, in vivo retinal measurements using circular scanning around vessel bifurcations of healthy human volunteers were performed. Measurements of the absolute mean flow and its orientation are in good agreement with the expected values for in vitro measurements. For in vivo measurements, the in- and outflow of blood for retinal vessel bifurcations show an excellent agreement, demonstrating the reliability of the technique.

  2. Three-beam Doppler optical coherence tomography using a facet prism telescope and MEMS mirror for improved transversal resolution

    PubMed Central

    Haindl, R.; Trasischker, W.; Baumann, B.; Pircher, M.; Hitzenberger, C.K.

    2015-01-01

    An improved three-beam Doppler optical coherence tomography system was developed. It utilizes a custom-made three-facet prism telescope to improve the transversal resolution at the sample. Furthermore, a two-axis gimbal-less MEMS mirror is used to minimize off-pivot beam movement at the pupil of the eye, enabling circular scanning for in vivo retinal measurements. We demonstrate the system’s abilities for in vitro circular scanning to measure absolute flow and to reconstruct the full velocity vector on a bifurcation flow phantom. Moreover, in vivo retinal measurements using circular scanning around vessel bifurcations of healthy human volunteers were performed. Measurements of the absolute mean flow and its orientation are in good agreement with the expected values for in vitro measurements. For in vivo measurements, the in- and outflow of blood for retinal vessel bifurcations show an excellent agreement, demonstrating the reliability of the technique. PMID:26689672

  3. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

    NASA Astrophysics Data System (ADS)

    Werkmeister, René M.; Vietauer, Martin; Knopf, Corinna; Fürnsinn, Clemens; Leitgeb, Rainer A.; Reitsamer, Herbert; Gröschl, Martin; Garhöfer, Gerhard; Vilser, Walthard; Schmetterer, Leopold

    2014-10-01

    A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique. The system was operated with an 841-nm superluminescent diode and a charge-coupled device camera that could be operated at a line rate of 20 kHz. We show that the system is capable of quantifying the response of 100% oxygen breathing on the retinal blood flow. In six rats, we observed a decrease in retinal vessel diameters of 13.2% and a decrease in retinal blood velocity of 42.6%, leading to a decrease in retinal blood flow of 56.7%. Furthermore, in four rats, the response of retinal blood flow during stimulation with diffuse flicker light was assessed. Retinal vessel diameter and blood velocity increased by 3.4% and 28.1%, respectively, leading to a relative increase in blood flow of 36.2%;. The presented technique shows much promise to quantify early changes in retinal blood flow during provocation with various stimuli in rodent models of ocular diseases in rats.

  4. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging.

    PubMed

    Werkmeister, René M; Vietauer, Martin; Knopf, Corinna; Fürnsinn, Clemens; Leitgeb, Rainer A; Reitsamer, Herbert; Gröschl, Martin; Garhöfer, Gerhard; Vilser, Walthard; Schmetterer, Leopold

    2014-01-01

    A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique. The system was operated with an 841-nm superluminescent diode and a charge-coupled device camera that could be operated at a line rate of 20 kHz. We show that the system is capable of quantifying the response of 100% oxygen breathing on the retinal blood flow. In six rats, we observed a decrease in retinal vessel diameters of 13.2% and a decrease in retinal blood velocity of 42.6%, leading to a decrease in retinal blood flow of 56.7%. Furthermore, in four rats, the response of retinal blood flow during stimulation with diffuse flicker light was assessed. Retinal vessel diameter and blood velocity increased by 3.4% and 28.1%, respectively, leading to a relative increase in blood flow of 36.2%. The presented technique shows much promise to quantify early changes in retinal blood flow during provocation with various stimuli in rodent models of ocular diseases in rats.

  5. En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

    PubMed Central

    Tan, Ou; Liu, Gangjun; Liang, Liu; Gao, Simon S.; Pechauer, Alex D.; Jia, Yali; Huang, David

    2015-01-01

    Abstract. An automated algorithm was developed for total retinal blood flow (TRBF) using 70-kHz spectral optical coherence tomography (OCT). The OCT was calibrated for the transformation from Doppler shift to speed based on a flow phantom. The TRBF scan pattern contained five repeated volume scans (2×2  mm) obtained in 3 s and centered on central retinal vessels in the optic disc. The TRBF was calculated using an en face Doppler technique. For each retinal vein, blood flow was measured at an optimal plane where the calculated flow was maximized. The TRBF was calculated by summing flow in all veins. The algorithm tracked vascular branching so that either root or branch veins are summed, but never both. The TRBF in five repeated volumes were averaged to reduce variation due to cardiac cycle pulsation. Finally, the TRBF was corrected for eye length variation. Twelve healthy eyes and 12 glaucomatous eyes were enrolled to test the algorithm. The TRBF was 45.4±6.7  μl/min for healthy control and 34.7±7.6  μl/min for glaucomatous participants (p-value=0.01). The intravisit repeatability was 8.6% for healthy controls and 8.4% for glaucoma participants. The proposed automated method provided repeatable TRBF measurement. PMID:26062663

  6. Development of a phase-resolved Doppler optical coherence tomography system for use in cutaneous microcirculation research

    NASA Astrophysics Data System (ADS)

    Moger, Julian; Matcher, Stephen J.; Shore, Angel C.

    2002-06-01

    Phase-resolved Doppler optical coherence tomography is a recently reported technique for simultaneously imaging tissue structure and blood with high velocity resolution. The optical set-up consists of a fibre-based Michelson interferometer with a 1300nm superluminescent diode in the source arm. The output power is 0.6mW with a bandwidth of 50nm. The reference arm contains a grating-based Fourier domain rapid-scanning delay line with an electro-optic phase modulator to provide a stable reference frequency (800kHz). Ten axial scans sampled, at 400Hz, from the same location are processed to generate structural and velocity data from the reconstructed phase information derived from a Hilbert transform. The sample arm probe focuses light from the fibre into the tissue, producing a beam spot of diameter approximately 20micrometers . The probe is mounted on a linear translation stage, which generates a lateral step of 10micrometers between groups of ten axial scans. The Doppler shift in each pixel is calculated from the average phase shift over the ten sequential scans at each location. The acquisition time for a 100x100 pixel image is approximately 5s. We demonstrate the systems ability to image in-vivo changes in skin perfusion, induced by standard non-invasive physiological techniques.

  7. En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Tan, Ou; Liu, Gangjun; Liang, Liu; Gao, Simon S.; Pechauer, Alex D.; Jia, Yali; Huang, David

    2015-06-01

    An automated algorithm was developed for total retinal blood flow (TRBF) using 70-kHz spectral optical coherence tomography (OCT). The OCT was calibrated for the transformation from Doppler shift to speed based on a flow phantom. The TRBF scan pattern contained five repeated volume scans (2×2 mm) obtained in 3 s and centered on central retinal vessels in the optic disc. The TRBF was calculated using an en face Doppler technique. For each retinal vein, blood flow was measured at an optimal plane where the calculated flow was maximized. The TRBF was calculated by summing flow in all veins. The algorithm tracked vascular branching so that either root or branch veins are summed, but never both. The TRBF in five repeated volumes were averaged to reduce variation due to cardiac cycle pulsation. Finally, the TRBF was corrected for eye length variation. Twelve healthy eyes and 12 glaucomatous eyes were enrolled to test the algorithm. The TRBF was 45.4±6.7 μl/min for healthy control and 34.7±7.6 μl/min for glaucomatous participants (p-value=0.01). The intravisit repeatability was 8.6% for healthy controls and 8.4% for glaucoma participants. The proposed automated method provided repeatable TRBF measurement.

  8. Reduction of phase-induced intensity noise in a fiber-based coherent Doppler lidar using polarization control.

    PubMed

    Rodrigo, Peter John; Pedersen, Christian

    2010-03-01

    Optimization of signal-to-noise ratio is an important aspect in the design of optical heterodyne detection systems such as a coherent Doppler lidar (CDL). In a CDL, optimal performance is achieved when the noise in the detector signal is dominated by local oscillator shot-noise. Most modern CDL systems are built using rugged and cost-efficient fiber optic components. Unfortunately, leakage signals such as residual reflections inherent within fiber components (e.g. circulator) can introduce phase-induced intensity noise (PIIN) to the Doppler spectrum in a CDL. Such excess noise may be a few orders of magnitude above the shot-noise level within the relevant CDL frequency bandwidth--corrupting the measurement of typically weak backscattered signals. In this study, observation of PIIN in a fiber-based CDL with a master-oscillator power-amplifier tapered semiconductor laser source is reported. Furthermore, we experimentally demonstrate what we believe is a newly proposed method using a simple polarization scheme to reduce PIIN by more than an order of magnitude.

  9. Eye-safe coherent laser radar system at 2.1 microns using Tm,Ho:YAG lasers

    NASA Technical Reports Server (NTRS)

    Henderson, Sammy W.; Hale, Charley P.; Magee, James R.; Kavaya, Michael J.; Huffaker, A. V.

    1991-01-01

    An eye-safe pulsed coherent laser radar has been developed by using single-frequency Tm,Ho:YAG lasers and heterodyne detection. Returns from a mountainside located 145 km from the laser radar system and the measurement of wind velocity to ranges exceeding 20 km have been demonstrated with transmitted pulse energies of 22 mJ.

  10. Velocity gradients in spatially-resolved laser Doppler flowmetry and dynamic light scattering with confocal and coherence gating

    PubMed Central

    Uribe-Patarroyo, Néstor; Bouma, Brett E.

    2016-01-01

    Dynamic light scattering (DLS) is widely used to characterize diffusive motion to obtain precise information on colloidal suspensions by calculating the autocorrelation function of the signal from a heterodyne optical system. DLS can also be used to determine the flow velocity field in systems that exhibit mass transport by incorporating the effects of the deterministic motion of scatterers on the autocorrelation function, a technique commonly known as laser Doppler flowmetry. DLS measurements can be localized with confocal and coherence gating techniques such as confocal microscopy and optical coherence tomography, thereby enabling the determination of the spatially-resolved velocity field in three dimensions. It has been thought that spatially-resolved DLS can determine the axial velocity as well as the lateral speed in a single measurement. We demonstrate, however, that gradients in the axial velocity of scatterers exert a fundamental influence on the autocorrelation function even in well-behaved, non-turbulent flow. By obtaining the explicit functional relation between axial-velocity gradients and the autocorrelation function, we show that the velocity field and its derivatives are intimately related and their contributions cannot be separated. Therefore, a single DLS measurement cannot univocally determine the velocity field. Our extended theoretical model was found to be in good agreement with experimental measurements. PMID:27627357

  11. Velocity gradients in spatially resolved laser Doppler flowmetry and dynamic light scattering with confocal and coherence gating

    NASA Astrophysics Data System (ADS)

    Uribe-Patarroyo, Néstor; Bouma, Brett E.

    2016-08-01

    Dynamic light scattering (DLS) is widely used to characterize diffusive motion to obtain precise information on colloidal suspensions by calculating the autocorrelation function of the signal from a heterodyne optical system. DLS can also be used to determine the flow velocity field in systems that exhibit mass transport by incorporating the effects of the deterministic motion of scatterers on the autocorrelation function, a technique commonly known as laser Doppler flowmetry. DLS measurements can be localized with confocal and coherence gating techniques such as confocal microscopy and optical coherence tomography, thereby enabling the determination of the spatially resolved velocity field in three dimensions. It has been thought that spatially resolved DLS can determine the axial velocity as well as the lateral speed in a single measurement. We demonstrate, however, that gradients in the axial velocity of scatterers exert a fundamental influence on the autocorrelation function even in well-behaved, nonturbulent flow. By obtaining the explicit functional relation between axial-velocity gradients and the autocorrelation function, we show that the velocity field and its derivatives are intimately related and their contributions cannot be separated. Therefore, a single DLS measurement cannot univocally determine the velocity field. Our extended theoretical model was found to be in good agreement with experimental measurements.

  12. Design and evaluation of a short coherence length laser-based Doppler wind Lidar system for wind energy applications

    NASA Astrophysics Data System (ADS)

    Shinohara, Leilei; Asche-Tauscher, Julian; Fox, Maik; Beuth, Thorsten; Stork, Wilhelm

    2014-05-01

    Nowadays larger horizontal axis wind turbines (HAWT) are setup in difficult to access locations adding an overhead to the production cost as well as the Operation & Maintenance (O&M) costs. In order to cover those overhead cost, Lidar assisted preview control of wind turbine blade pitch system is prosperous both on research and industry applications. However, there are not a lot of choices to remote sense the wind field inflow. Doppler wind Lidar systems have been proved to be advantageous on such applications. However due to the economical consideration, the state-of-the-art wind Lidar systems are only limited on research. Therefore, developing a cost efficient wind Lidar to support the pitch control of HAWT to reduce the material requirement, lower the O&M cost and decrease the cost of energy (COE) in the long term is our motivation. Our current main focusing of investigations has been laid on the optical design of emitting and receiving system, and the evaluation of the low cost laser system instead of using a high cost fiber laser as a transmitter. The short coherence length lasers brings a higher phase noise into the detection, normally it is not used for the coherent Lidars system. However, such a laser can achieve a higher output power with a low cost which is very important for the market. In order to bring such kind of laser into the application, different sending, receiving, and detection design is simulated and tested. Those testing results are presented in this paper.

  13. In vivo lung microvasculature visualized in three dimensions using fiber-optic color Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lee, Anthony M. D.; Ohtani, Keishi; MacAulay, Calum; McWilliams, Annette; Shaipanich, Tawimas; Yang, Victor X. D.; Lam, Stephen; Lane, Pierre

    2013-05-01

    For the first time, the use of fiber-optic color Doppler optical coherence tomography (CDOCT) to map in vivo the three-dimensional (3-D) vascular network of airway segments in human lungs is demonstrated. Visualizing the 3-D vascular network in the lungs may provide new opportunities for detecting and monitoring lung diseases such as asthma, chronic obstructive pulmonary disease, and lung cancer. Our CDOCT instrument employs a rotary fiber-optic probe that provides simultaneous two-dimensional (2-D) real-time structural optical coherence tomography (OCT) and CDOCT imaging at frame rates up to 12.5 frames per second. Controlled pullback of the probe allows 3-D vascular mapping in airway segments up to 50 mm in length in a single acquisition. We demonstrate the ability of CDOCT to map both small and large vessels. In one example, CDOCT imaging allows assignment of a feature in the structural OCT image as a large (˜1 mm diameter) blood vessel. In a second example, a smaller vessel (˜80 μm diameter) that is indistinguishable in the structural OCT image is fully visualized in 3-D using CDOCT.

  14. Measurement of Retinal Blood Flow in Normal Chinese-American Subjects by Doppler Fourier-Domain Optical Coherence Tomography

    PubMed Central

    Srinivas, Sowmya; Tan, Ou; Wu, Shuang; Nittala, Muneeswar Gupta; Huang, David; Varma, Rohit; Sadda, SriniVas R.

    2015-01-01

    Purpose. To measure total retinal blood flow (TRBF) in normal, healthy Chinese Americans by using semi-automated analysis of Doppler Fourier-domain optical coherence tomography (FD-OCT) scans. Methods. Two hundred sixty-six normal, healthy Chinese-American participants (266 eyes) were enrolled from The Chinese American Eye Study. All participants underwent complete ophthalmic examination, including best-corrected visual acuity, indirect ophthalmoscopy, and Doppler FD-OCT imaging, using the circumpapillary double circular scan protocol. Total retinal blood flow and other vascular parameters (e.g., venous and arterial cross-sectional area and their velocities) were calculated by using Doppler OCT of Retinal Circulation software. Associations between TRBF and other clinical parameters were assessed by using bivariate correlations and linear regression. Results. The mean age of study participants was 57.40 ± 5.60 (range, 50–82) years. The mean TRBF was 49.34 ± 10.08 (range, 27.17–78.08, 95% confidence interval: 25.98–69.10) μL/min. The mean venous area was 0.0548 (±0.0084) mm2. Superior retinal hemispheric blood flow (25.50 ± 6.62 μL/min) was slightly greater than inferior retinal hemispheric blood flow (23.84 ± 7.19 μL/min, P = 0.008). The mean flow velocity was 15.16 ± 3.12 mm/s. There was a weak but significant negative correlation between TRBF and age (r = −0.15, P = 0.012). No significant correlation was found between TRBF and axial length (r = 0.11, P = 0.08). Retinal blood flow was not significantly correlated with any other clinical parameters, including body mass index, systolic blood pressure, diastolic blood pressure, and intraocular pressure. Conclusions. Normal Doppler OCT-derived total retinal blood values in a Chinese-American population showed considerable variability, some of which was explained by age. These observations should help design future studies evaluating TRBF in populations with eye disease. PMID:25670487

  15. Investigation of a Complex Nocturnal Flow in Owens Valley, California Using Coherent Doppler Lidar

    NASA Astrophysics Data System (ADS)

    Choukulkar, Aditya; Calhoun, Ronald; Billings, Brian; Doyle, James

    2012-09-01

    A study of an interesting meteorological episode over the Owens Valley, California, USA during the Terrain-Induced Rotor EXperiment was conducted using a recently adapted statistical interpolation method to retrieve wind-velocity vectors from Doppler lidar data. This vector retrieval method has been adapted from radar data assimilation techniques. Results show that the method allows better preservation of local variations in the flow field than other techniques. In addition, a high resolution Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) run is used to understand the large-scale flow within the valley and compared with lidar retrievals. Observations from 1030 UTC to 1230 UTC (0230 local time to 0430 local time) on March 27, 2006 are presented. Lidar observations show complex and uncharacteristic flows such as sudden bursts of westerly cross-valley wind mixing with the dominant up-valley wind. Model results from COAMPS and other in-situ instrumentation are used to corroborate and complement these observations. The optimal interpolation technique for Doppler lidar data vector retrieval appears well suited for scenarios with complex spatial variations in the flow field.

  16. Computer Simulation of Global Profiles of Carbon Dioxide Using a Pulsed, 2-Micron, Coherent-Detection, Column-Content DIAL System

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Singh, Upendra N.; Koch, Grady J.; Yu, Jirong; Frehlich, Rod G.

    2009-01-01

    We present preliminary results of computer simulations of the error in measuring carbon dioxide mixing ratio profiles from earth orbit. The simulated sensor is a pulsed, 2-micron, coherent-detection lidar alternately operating on at least two wavelengths. The simulated geometry is a nadir viewing lidar measuring the column content signal. Atmospheric absorption is modeled using FASCODE3P software with the HITRAN 2004 absorption line data base. Lidar shot accumulation is employed up to the horizontal resolution limit. Horizontal resolutions of 50, 100, and 200 km are shown. Assuming a 400 km spacecraft orbit, the horizontal resolutions correspond to measurement times of about 7, 14, and 28 s. We simulate laser pulse-pair repetition frequencies from 1 Hz to 100 kHz. The range of shot accumulation is 7 to 2.8 million pulse-pairs. The resultant error is shown as a function of horizontal resolution, laser pulse-pair repetition frequency, and laser pulse energy. The effect of different on and off pulse energies is explored. The results are compared to simulation results of others and to demonstrated 2-micron operating points at NASA Langley.

  17. Coherent Doppler Lidar for Measuring Altitude, Ground Velocity, and Air Velocity of Aircraft and Spaceborne Vehicles

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin (Inventor); Pierrottet, Diego F. (Inventor)

    2015-01-01

    A Doppler lidar sensor system includes a laser generator that produces a highly pure single frequency laser beam, and a frequency modulator that modulates the laser beam with a highly linear frequency waveform. A first portion of the frequency modulated laser beam is amplified, and parts thereof are transmitted through at least three separate transmit/receive lenses. A second portion of the laser beam is used as a local oscillator beam for optical heterodyne detection. Radiation from the parts of the laser beam transmitted via the transmit/receive lenses is received by the respective transmit/receive lenses that transmitted the respective part of the laser beam. The received reflected radiation is compared with the local oscillator beam to calculate the frequency difference there between to determine various navigational data.

  18. 4D shear stress maps of the developing heart using Doppler optical coherence tomography.

    PubMed

    Peterson, Lindsy M; Jenkins, Michael W; Gu, Shi; Barwick, Lee; Watanabe, Michiko; Rollins, Andrew M

    2012-11-01

    Accurate imaging and measurement of hemodynamic forces is vital for investigating how physical forces acting on the embryonic heart are transduced and influence developmental pathways. Of particular importance is blood flow-induced shear stress, which influences gene expression by endothelial cells and potentially leads to congenital heart defects through abnormal heart looping, septation, and valvulogenesis. However no imaging tool has been available to measure shear stress on the endocardium volumetrically and dynamically. Using 4D structural and Doppler OCT imaging, we are able to accurately measure the blood flow in the heart tube in vivo and to map endocardial shear stress throughout the heart cycle under physiological conditions for the first time. These measurements of the shear stress patterns will enable precise titration of experimental perturbations and accurate correlation of shear with the expression of molecules critical to heart development.

  19. Label-free in-vivo measurement of lymph flow velocity using Doppler optical coherence tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Blatter, Cedric; Meijer, Eelco F. J.; Nam, Ahhyun S.; Jones, Dennis; Padera, Timothy P.; Vakoc, Benjamin J.

    2016-03-01

    Alterations in lymphatic network function contribute to the lymphedema development, cancer progression and impairment in regional immune function. However, there are limited tools available to directly measure lymphatic vessel function and transport in vivo. Existing approaches such as fluorescence recovery after photo-bleaching (FRAP) require injection of exogenous labels which intrinsically alter the physiology of the local lymphatic network. A label-free approach to imaging lymph flow in vivo would provide direct and unaltered measurements of lymphatic vessel transport and could catalyze research in lymphatic biology. Here, we demonstrate and validate the use of Doppler optical coherence tomography (DOCT) to measure lymph flow in vivo at speeds as low as 50µm/s. Compared to blood, lymph is relatively acellular (under normal conditions), but contains similar soluble components to blood plasma. We demonstrate that the small but detectable scattering signal from lymph can be used to extract fluid velocity using a dedicated algorithm optimized for Doppler analysis in low signal-to-noise settings (0 to 6 dB typical). We demonstrate the accuracy of this technique by comparing DOCT to FRAP measurements, using an intralipid lymph proxy in microfluidic devices and in vivo in the mouse ear. Finally, we demonstrate the label free measurement of lymph speed in the hind-limb of mice with a temporal resolution of 0.25s that agree well with prior literature reports. We anticipate that DOCT can become a powerful new tool in preclinical lymphatic biology research—including the relationship between lymphatic function and metastasis formation—with the potential to later expand also to clinical settings.

  20. Depth-dependent displacement sensitivity analysis and the influence of Doppler angle for quantitative assessment of mechanical properties using phase-sensitive spectral domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lynch, Gillian; Subhash, Hrebesh; Alexandrov, Sergey; Leahy, Martin

    2016-03-01

    Optical coherence elastography (OCE) asesses the mechanical properties of samples by applying a mechanical stimulation and detecting the resulting sample displacement using optical coherence tomography (OCT). OCE methods which utilise the phase of the OCT signal offer the potential to detect displacements on the sub-nanometre scale. However, the displacement sensitivity achieveable is directly related to the signal-to-noise ratio and phase stability of the underlying OCT system. Furthermore, the estimation of Doppler angle is imperative in accurately measuring the sample displacement. This work evaluates the contributions of each of these parameters for quantitative assessment of mechanical properties using phase-sensitive spectral domain OCT.

  1. Graphics processor unit acceleration enables realtime endovascular Doppler optical coherence tomography imaging: development and validation (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Barrows, Dexter; Ramjist, Joel M.; Vuong, Barry; Lee, Kenneth K.; Jivraj, Jamil; Yang, Victor X. D.

    2017-02-01

    Endovascular Optical Coherence Tomography (OCT) has previously been used in both bench-top and clinical environments to produce vascular images, and can be helpful in characterizing, among other pathologies, plaque build-up and impedances to normal blood flow. The raw data produced can also be processed to yield high-resolution blood velocity information, but this computation is expensive and has previously only been available a posteriori using post-processing software. Real-time Doppler OCT (DOCT) imaging has been demonstrated before in the skin and eye, but this capability has not been available to vascular surgeons. Graphics Processing Units (GPUs) can be used to dramatically accelerate this type of distributed computation. In this paper we present a software package capable of real-time DOCT processing and circular image display using GPU acceleration designed to operate with catheter-based clinical OCT systems. This image data is overlayed onto structural images providing clinicians with live, high-resolution blood velocity information to complement anatomical data. Further, we validated flow data obtained in real time using a carotid flow phantom - constructed using 3D structural OCT data - and controlled flow from an external pump.

  2. In vivo cross-sectional imaging of the phonating larynx using long-range Doppler optical coherence tomography

    PubMed Central

    Coughlan, Carolyn A.; Chou, Li-dek; Jing, Joseph C.; Chen, Jason J.; Rangarajan, Swathi; Chang, Theodore H.; Sharma, Giriraj K.; Cho, Kyoungrai; Lee, Donghoon; Goddard, Julie A.; Chen, Zhongping; Wong, Brian J. F.

    2016-01-01

    Diagnosis and treatment of vocal fold lesions has been a long-evolving science for the otolaryngologist. Contemporary practice requires biopsy of a glottal lesion in the operating room under general anesthesia for diagnosis. Current in-office technology is limited to visualizing the surface of the vocal folds with fiber-optic or rigid endoscopy and using stroboscopic or high-speed video to infer information about submucosal processes. Previous efforts using optical coherence tomography (OCT) have been limited by small working distances and imaging ranges. Here we report the first full field, high-speed, and long-range OCT images of awake patients’ vocal folds as well as cross-sectional video and Doppler analysis of their vocal fold motions during phonation. These vertical-cavity surface-emitting laser source (VCSEL) OCT images offer depth resolved, high-resolution, high-speed, and panoramic images of both the true and false vocal folds. This technology has the potential to revolutionize in-office imaging of the larynx. PMID:26960250

  3. Evaluation of flow velocities after carotid artery stenting through split spectrum Doppler optical coherence tomography and computational fluid dynamics modeling

    PubMed Central

    Vuong, Barry; Genis, Helen; Wong, Ronnie; Ramjist, Joel; Jivraj, Jamil; Farooq, Hamza; Sun, Cuiru; Yang, Victor X.D.

    2014-01-01

    Hemodynamics plays a critical role in the development of atherosclerosis, specifically in regions of curved vasculature such as bifurcations exhibiting irregular blood flow profiles. Carotid atherosclerotic disease can be intervened by stent implantation, but this may result in greater alterations to local blood flow and consequently further complications. This study demonstrates the use of a variant of Doppler optical coherence tomography (DOCT) known as split spectrum DOCT (ssDOCT) to evaluate hemodynamic patterns both before and after stent implantation in the bifurcation junction in the internal carotid artery (ICA). Computational fluid dynamics (CFD) models were constructed to simulate blood velocity profiles and compared to the findings achieved through ssDOCT images. Both methods demonstrated noticeable alterations in hemodynamic patterns following stent implantation, with features such as slow velocity regions at the neck of the bifurcation and recirculation zones at the stent struts. Strong correlation between CFD models and ssDOCT images demonstrate the potential of ssDOCT imaging in the optimization of stent implantation in the clinical setting. PMID:25574447

  4. Evaluation of flow velocities after carotid artery stenting through split spectrum Doppler optical coherence tomography and computational fluid dynamics modeling.

    PubMed

    Vuong, Barry; Genis, Helen; Wong, Ronnie; Ramjist, Joel; Jivraj, Jamil; Farooq, Hamza; Sun, Cuiru; Yang, Victor X D

    2014-12-01

    Hemodynamics plays a critical role in the development of atherosclerosis, specifically in regions of curved vasculature such as bifurcations exhibiting irregular blood flow profiles. Carotid atherosclerotic disease can be intervened by stent implantation, but this may result in greater alterations to local blood flow and consequently further complications. This study demonstrates the use of a variant of Doppler optical coherence tomography (DOCT) known as split spectrum DOCT (ssDOCT) to evaluate hemodynamic patterns both before and after stent implantation in the bifurcation junction in the internal carotid artery (ICA). Computational fluid dynamics (CFD) models were constructed to simulate blood velocity profiles and compared to the findings achieved through ssDOCT images. Both methods demonstrated noticeable alterations in hemodynamic patterns following stent implantation, with features such as slow velocity regions at the neck of the bifurcation and recirculation zones at the stent struts. Strong correlation between CFD models and ssDOCT images demonstrate the potential of ssDOCT imaging in the optimization of stent implantation in the clinical setting.

  5. In vivo cross-sectional imaging of the phonating larynx using long-range Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Coughlan, Carolyn A.; Chou, Li-Dek; Jing, Joseph C.; Chen, Jason J.; Rangarajan, Swathi; Chang, Theodore H.; Sharma, Giriraj K.; Cho, Kyoungrai; Lee, Donghoon; Goddard, Julie A.; Chen, Zhongping; Wong, Brian J. F.

    2016-03-01

    Diagnosis and treatment of vocal fold lesions has been a long-evolving science for the otolaryngologist. Contemporary practice requires biopsy of a glottal lesion in the operating room under general anesthesia for diagnosis. Current in-office technology is limited to visualizing the surface of the vocal folds with fiber-optic or rigid endoscopy and using stroboscopic or high-speed video to infer information about submucosal processes. Previous efforts using optical coherence tomography (OCT) have been limited by small working distances and imaging ranges. Here we report the first full field, high-speed, and long-range OCT images of awake patients’ vocal folds as well as cross-sectional video and Doppler analysis of their vocal fold motions during phonation. These vertical-cavity surface-emitting laser source (VCSEL) OCT images offer depth resolved, high-resolution, high-speed, and panoramic images of both the true and false vocal folds. This technology has the potential to revolutionize in-office imaging of the larynx.

  6. Assessment of hemodynamics of intracranial aneurysms using Doppler optical coherence tomography in patient specific phantoms: preliminary results (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Ramjist, Joel M.; Jivraj, Jamil; Barrows, Dexter; Vuong, Barry; Wong, Ronnie; Yang, Victor X. D.

    2017-02-01

    Intracranial aneurysms affect a large number of individuals every year. Changes to hemodynamics are thought to be a crucial factor in the initial formation and enlargement of intracranial aneurysms. Previously, surgical clipping - an open an invasive procedure, was the standard of care. More recently, minimally invasive, catheter based therapies, specifically stenting and coiling, has been employed for treatment as it is less invasive and poses fewer overall risks. However, these treatments can further alter hemodynamic patterns of patients, affecting efficacy and prognosis. Doppler optical coherence tomography (DOCT) has shown to be useful for the evaluation of changes to hemodynamic patterns in various vascular pathologies, and intravascular DOCT may provide useful insight in the evaluation and changes to hemodynamic patterns before and during the treatment of aneurysms. In this study, we present preliminary results of DOCT imaging used in three patient-specific aneurysm phantoms located within the Circle of Willis both pre and post-treatment. These results are compared with computational fluid dynamics (CFD) simulations and high-speed camera imaging for further interpretation and validation of results.

  7. Spatial-temporal analysis of coherent offshore wind field structures measured by scanning Doppler-lidar

    NASA Astrophysics Data System (ADS)

    Valldecabres, L.; Friedrichs, W.; von Bremen, L.; Kühn, M.

    2016-09-01

    An analysis of the spatial and temporal power fluctuations of a simplified wind farm model is conducted on four offshore wind fields data sets, two from lidar measurements and two from LES under unstable and neutral atmospheric conditions. The integral length scales of the horizontal wind speed computed in the streamwise and the cross-stream direction revealed the elongation of the structures in the direction of the mean flow. To analyse the effect of the structures on the power output of a wind turbine, the aggregated equivalent power of two wind turbines with different turbine spacing in the streamwise and cross-stream direction is analysed at different time scales under 10 minutes. The fact of considering the summation of the power of two wind turbines smooths out the fluctuations of the power output of a single wind turbine. This effect, which is stronger with increasing spacing between turbines, can be seen in the aggregation of the power of two wind turbines in the streamwise direction. Due to the anti-correlation of the coherent structures in the cross-stream direction, this smoothing effect is stronger when the aggregated power is computed with two wind turbines aligned orthogonally to the mean flow direction.

  8. Doppler optical coherence tomography to monitor the effect of photodynamic therapy on tissue morphology and perfusion

    NASA Astrophysics Data System (ADS)

    Aalders, Maurice C. G.; Triesscheijn, Martijn L.; Ruevekamp, Marjan; de Bruin, Daniel M.; Baas, Paul; Faber, Dirk J.; Stewart, Fiona A.

    2006-07-01

    We investigated the feasibility of using optical coherence tomography (OCT) for noninvasive real-time visualization of the vascular effects of photodynamic therapy (PDT) in normal and tumor tissue in mice. Perfusion control measurements were initially performed after administrating vaso-active drugs or clamping of the subcutaneous tumors. Subsequent measurements were made on tumor-bearing mice before and after PDT using the photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC). Tumors were illuminated using either a short drug light interval (D-L, 3h), when mTHPC is primarily located in the tumor vasculature or a long D-L interval (48 h), when the drug is distributed throughout the whole tumor. OCT enabled visualization of the different layers of tumor, and overlying skin with a maximal penetration of ≤ 0.5-1 mm. PDT with a short D-L interval resulted in a significant decrease of perfusion in the tumor periphery, to 20% of pre-treatment values at 160 min, whereas perfusion in the skin initially increased by 10% (at 25 min) and subsequently decreased to 60% of pre-treatment values (at 200 min). PDT with a long D-L interval did not induce significant changes in perfusion. The concept of using noninvasive OCT measurements for monitoring early, treatment-related changes in morphology and perfusion may have applications in evaluating effects of anti-angiogenic or antivascular (cancer) therapy.

  9. Airborne Astronomy with a 150 microns - 400 microns Heterodyne Spectrometer

    NASA Technical Reports Server (NTRS)

    Betz, A. L.

    1995-01-01

    This report summarizes work done under NASA Grant NAG2-753 awarded to the University of Colorado. The project goal was to build a far-infrared heterodyne spectrometer for NASA's Kuiper Airborne Observatory, and to use this instrument to observe atomic and molecular spectral lines from the interstellar medium. This goal was successfully achieved. Detections of particular note have been the 370 micron line of neutral atomic carbon, the 158 micron transition of ionized carbon, many of the high-J rotational lines of CO-12 and CO-13 between J=9-8 and J=22-21, the 119 micron and 163 micron rotational lines of OH, the 219 micron ground-state rotational line of H2D(+), and the 63 micron fine structure line of neutral atomic oxygen. All of these lines were observed at spectral resolutions exceeding 1 part in 10(exp 6) thereby allowing accurate line shapes and Doppler velocities to be measured.

  10. Airborne Astronomy with a 150 micron - 400 micron Heterodyne Spectrometer

    NASA Technical Reports Server (NTRS)

    Betz, A. L.

    1995-01-01

    This report summarizes work done under NASA Grant NAG2-753 awarded to the University of Colorado. The project goal was to build a far-infrared heterodyne spectrometer for NASA's Kuiper Airborne Observatory, and to use this instrument to observe atomic and molecular spectral lines from the interstellar medium. This goal was successfully achieved. Detections of particular note have been the 370 micron line of neutral atomic carbon, the 158 micron transition of ionized carbon, many of the high-J rotational lines of CO-12 and CO-13 between J=9-8 and J=22-21, the 119 micron and 163 micron rotational lines of OH, the 219 micron ground-state rotational line of H2D(+), and the 63 microns fine structure line of neutral atomic oxygen. All of these lines were observed at spectral resolutions exceeding 1 part in 10(exp 6), thereby allowing accurate line shapes and Doppler velocities to be measured.

  11. Ultrawideband coherent noise lidar range-Doppler imaging and signal processing by use of spatial-spectral holography in inhomogeneously broadened absorbers.

    PubMed

    Li, Youzhi; Hoskins, Alan; Schlottau, Friso; Wagner, Kelvin H; Embry, Carl; Babbitt, William Randall

    2006-09-01

    We introduce a new approach to coherent lidar range-Doppler sensing by utilizing random-noise illuminating waveforms and a quantum-optical, parallel sensor based on spatial-spectral holography (SSH) in a cryogenically cooled inhomogeneously broadened absorber (IBA) crystal. Interference between a reference signal and the lidar return in the spectrally selective absorption band of the IBA is used to sense the lidar returns and perform the front-end range-correlation signal processing. Modulating the reference by an array of Doppler compensating frequency shifts enables multichannel Doppler filtering. This SSH sensor performs much of the postdetection signal processing, increases the lidar system sensitivity through range-correlation gain before detection, and is capable of not only Doppler processing but also parallel multibeam reception using the high-spatial resolution of the IBA crystals. This approach permits the use of ultrawideband, high-power, random-noise, cw lasers as ranging waveforms in lidar systems instead of highly stabilized, injection-seeded, and amplified pulsed or modulated laser sources as required by most conventional coherent lidar systems. The capabilities of the IBA media for many tens of gigahertz bandwidth and resolution in the 30-300 kHz regime, while using either a pseudo-noise-coded waveform or just a high-power, noisy laser with a broad linewidth (e.g., a truly random noise lidar) may enable a new generation of improved lidar sensors and processors. Preliminary experimental demonstrations of lidar ranging and simulation on range-Doppler processing are presented.

  12. Advances in Doppler OCT

    PubMed Central

    Liu, Gangjun; Chen, Zhongping

    2014-01-01

    We review the principle and some recent applications of Doppler optical coherence tomography (OCT). The advances of the phase-resolved Doppler OCT method are described. Functional OCT algorithms which are based on an extension of the phase-resolved scheme are also introduced. Recent applications of Doppler OCT for quantification of flow, imaging of microvasculature and vocal fold vibration, and optical coherence elastography are briefly discussed. PMID:24443649

  13. Ionospheric response to magnetar flare: signature of SGR J1550-5418 on coherent ionospheric Doppler radar

    NASA Astrophysics Data System (ADS)

    Mahrous, Ayman

    2017-03-01

    This paper presents observational evidence of frequent ionospheric perturbations caused by the magnetar flare of the source SGR J1550-5418, which took place on 22 January 2009. These ionospheric perturbations are observed in the relative change of the total electron content (ΔTEC/Δt) measurements from the coherent ionospheric Doppler radar (CIDR). The CIDR system makes high-precision measurements of the total electron content (TEC) change along ray-paths from ground receivers to low Earth-orbiting (LEO) beacon spacecraft. These measurements can be integrated along the orbital track of the beacon satellite to construct the relative spatial, not temporal, TEC profiles that are useful for determining the large-scale plasma distribution. The observed spatial TEC changes reveal many interesting features of the magnetar signatures in the ionosphere. The onset phase of the magnetar flare was during the CIDR's nighttime satellite passage. The nighttime small-scale perturbations detected by CIDR, with ΔTEC/Δt ≥ 0.05 TECU s-1, over the eastern Mediterranean on 22 January 2009 were synchronized with the onset phase of the magnetar flare and consistent with the emission of hundreds of bursts detected from the source. The maximum daytime large-scale perturbation measured by CIDR over northern Africa and the eastern Mediterranean was detected after ˜ 6 h from the main phase of the magnetar flare, with ΔTEC/Δt ≤ 0.10 TECU s-1. These ionospheric perturbations resembled an unusual poleward traveling ionospheric disturbance (TID) caused by the extraterrestrial source. The TID's estimated virtual velocity is 385.8 m s-1, with ΔTEC/Δt ≤ 0.10 TECU s-1.

  14. In situ monitoring of localized shear stress and fluid flow within developing tissue constructs by Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Jia, Yali; Bagnaninchi, Pierre O.; Wang, Ruikang K.

    2008-02-01

    Mechanical stimuli can be introduced to three dimensional (3D) cell cultures by use of perfusion bioreactor. Especially in musculoskeletal tissues, shear stress caused by fluid flow generally increase extra-cellular matrix (ECM) production and cell proliferation. The relationship between the shear stress and the tissue development in situ is complicated because of the non-uniform pore distribution within the cell-seeded scaffold. In this study, we firstly demonstrated that Doppler optical coherence tomography (DOCT) is capable of monitoring localized fluid flow and shear stress in the complex porous scaffold by examining their variation trends at perfusion rate of 5, 8, 10 and 12 ml/hr. Then, we developed the 3D porous cellular constructs, cell-seeded chitosan scaffolds monitored during several days by DOCT. The fiber based fourier domain DOCT employed a 1300 nm superluminescent diode with a bandwidth of 52 nm and a xyz resolution of 20×20×15 μm in free space. This setup allowed us not only to assess the cell growth and ECM deposition by observing their different scattering behaviors but also to further investigate how the cell attachment and ECM production has the effect on the flow shear stress and the relationship between flow rate and shear stress in the developing tissue construct. The possibility to monitor continuously the constructs under perfusion will easily indicate the effect of flow rate or shear stress on the cell viability and cell proliferation, and then discriminate the perfusion parameters affecting the pre-tissue formation rate growth.

  15. Comparison of artificial neural network and multilinear regression analysis models in estimation of pulp flow speed from low coherence Doppler flowmetry measurement data

    NASA Astrophysics Data System (ADS)

    Hannula, Manne; Alarousu, Erkki; Prykäri, Tuukka; Myllylä, Risto

    2007-03-01

    Low Coherence Doppler Flowmetry (LCDF) measurement produces a signal, which frequency domain characteristics are in connection to the speed of the flow. In this study performances of Artificial Neural Network (ANN) and Multilinear Regression (MLR) methods in prediction of pulp flow speed from the LCDF measurement data were compared. In the study the pulp flow speed was estimated distinctly from consecutive frequency bands of the LCDF data with both methods. The smallest estimation error in flow speed with the ANN method was 20% and with the MLR method 30%, depending on the selected frequency band. The results indicate the relationship between characteristics of the LCDF measurement and pulp flow speed includes remarkable number of nonlinear components. The result is in line with theoretical calculations about the Doppler shifts occurrence in the LCDF data.

  16. Back Cover: Four-dimensional live imaging of hemodynamics in mammalian embryonic heart with Doppler optical coherence tomography (J. Biophotonics 8/2016).

    PubMed

    Wang, Shang; Lakomy, David S; Garcia, Monica D; Lopez, Andrew L; Larin, Kirill V; Larina, Irina V

    2016-08-01

    Detailed volumetric measurement of hemodynamics in early developing mammalian heart can provide great insights for improved understanding of normal cardiogenesis and management of congenital cardiac disease. In this study, Doppler optical coherence tomography is performed in live mouse embryo culture to obtain the first four-dimensional high-resolution reconstruction and quantitative analysis of hemodynamic features in the mouse embryonic heart. This provides a powerful approach to investigate biomechanical regulation of early mammalian cardiogenesis. Further details can be found in the article by Shang Wang et al. on pp. 837-847. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Doppler Optical Coherence Tomography

    NASA Astrophysics Data System (ADS)

    Chen, Zhongping; Zhang, Jun

    Noninvasive techniques for imaging in vivo blood flow are of great value to biomedical research and clinical diagnostics where many diseases have a vascular etiology or component. In ophthalmology, many diseases involve disturbances in ocular blood flow, including diabetic retinopathy, low tension glaucoma, anterior ischemic optic neuritis, and macular degeneration. Simultaneous imaging of tissue structure and blood flow could provide critical information for early diagnosis of ocular diseases.

  18. Cardiac-Gated En Face Doppler Measurement of Retinal Blood Flow Using Swept-Source Optical Coherence Tomography at 100,000 Axial Scans per Second

    PubMed Central

    Lee, ByungKun; Choi, WooJhon; Liu, Jonathan J.; Lu, Chen D.; Schuman, Joel S.; Wollstein, Gadi; Duker, Jay S.; Waheed, Nadia K.; Fujimoto, James G.

    2015-01-01

    Purpose. To develop and demonstrate a cardiac gating method for repeatable in vivo measurement of total retinal blood flow (TRBF) in humans using en face Doppler optical coherence tomography (OCT) at commercially available imaging speeds. Methods. A prototype swept-source OCT system operating at 100-kHz axial scan rate was developed and interfaced with a pulse oximeter. Using the plethysmogram measured from the earlobe, Doppler OCT imaging of a 1.5- × 2-mm area at the optic disc at 1.8 volumes/s was synchronized to cardiac cycle to improve sampling of pulsatile blood flow. Postprocessing algorithms were developed to achieve fully automatic calculation of TRBF. We evaluated the repeatability of en face Doppler OCT measurement of TRBF in 10 healthy young subjects using three methods: measurement at 100 kHz with asynchronous acquisition, measurement at 100 kHz with cardiac-gated acquisition, and a control measurement using a 400-kHz instrument with asynchronous acquisition. Results. The median intrasubject coefficients of variation (COV) of the three methods were 8.0%, 4.9%, and 6.1%, respectively. All three methods correlated well, without a significant bias. Mean TRBF measured at 100 kHz with cardiac-gated acquisition was 40.5 ± 8.2 μL/min, and the range was from 26.6 to 55.8 μL/min. Conclusions. Cardiac-gated en face Doppler OCT can achieve smaller measurement variability than previously reported methods. Although further validation in older subjects and diseased subjects is required, precise measurement of TRBF using cardiac-gated en face Doppler OCT at commercially available imaging speeds should be feasible. PMID:25744974

  19. Doppler Lidar for Wind Measurements on Venus

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Emmitt, George D.; Yu, Jirong; Kavaya, Michael J.

    2010-01-01

    NASA Langley Research Center has a long history of developing 2-micron laser transmitter for wind sensing. With support from NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement. The transmitter portion of the transceiver employs the high-pulse-energy, Ho:Tm:LuLiF, partially conductively cooled laser technology developed at NASA Langley. The transceiver is capable of 250 mJ pulses at 10 Hz. It is very similar to the technology envisioned for coherent Doppler lidar wind measurements from Earth and Mars orbit. The transceiver is coupled to the large optics and data acquisition system in the NASA Langley VALIDAR mobile trailer. The large optics consists of a 15-cm off-axis beam expanding telescope, and a full-hemispheric scanner. Vertical and horizontal vector winds are measured, as well as relative backscatter. The data acquisition system employs frequency domain velocity estimation and pulse accumulation. It permits real-time display of the processed winds and archival of all data. This lidar system was recently deployed at Howard University facility in Beltsville, Mary-land, along with other wind lidar systems. Coherent Doppler wind lidar ground-based wind measurements and comparisons with other sensors will be presented. A simulation and data product for wind measurement at Venus will be presented.

  20. High speed, wide velocity dynamic range Doppler optical coherence tomography (Part V): Optimal utilization of multi-beam scanning for Doppler and speckle variance microvascular imaging.

    PubMed

    Chen, Chaoliang; Cheng, Kyle H Y; Jakubovic, Raphael; Jivraj, Jamil; Ramjist, Joel; Deorajh, Ryan; Gao, Wanrong; Barnes, Elizabeth; Chin, Lee; Yang, Victor X D

    2017-04-03

    In this paper, a multi-beam scanning technique is proposed to optimize the microvascular images of human skin obtained with Doppler effect based methods and speckle variance processing. Flow phantom experiments were performed to investigate the suitability for combining multi-beam data to achieve enhanced microvascular imaging. To our surprise, the highly variable spot sizes (ranging from 13 to 77 μm) encountered in high numerical aperture multi-beam OCT system imaging the same target provided reasonably uniform Doppler variance and speckle variance responses as functions of flow velocity, which formed the basis for combining them to obtain better microvascular imaging without scanning penalty. In vivo 2D and 3D imaging of human skin was then performed to further demonstrate the benefit of combining multi-beam scanning to obtain improved signal-to-noise ratio (SNR) in microvascular imaging. Such SNR improvement can be as high as 10 dB. To our knowledge, this is the first demonstration of combining different spot size, staggered multiple optical foci scanning, to achieve enhanced SNR for blood flow OCT imaging.

  1. Tm,Ho:YAG laser with tunable range of 2.08-2.12 microns and its applications to spectroscopy

    NASA Technical Reports Server (NTRS)

    Asai, Kazuhiro; Itabe, Toshikazu

    1992-01-01

    In recent advanced lasers, 2 micron solid-state lasers such as Tm:YAG and Ho:YAG lasers are very attractive for laser radar remote sensing technologies because of eye safety, realizations of all solid-state laser pumped by diode laser and smaller dimension, tunability of lasing wavelength, possibility of coherent detection, etc. Featuring these advantages, 2 micron lasers have been candidated as laser transmitters for use in water vapor Differential Absorption Lidar (DIAL), laser altimeter, Doppler wind sensor, Mie lidar, etc. Characterization of a tunable Cr, Tm, Ho:YAG laser and its applications to spectroscopy concerning absorption and reflectance are reported.

  2. Estimation of orbital Doppler shift change due to nutation of attitude for 2-μm coherent Doppler lidar on ISS-JEM (International Space Station-Japanese Experimental Module)

    NASA Astrophysics Data System (ADS)

    Totsuka, Makoto; Asai, Kazuhiro; Iwasaki, Toshiki; Mizutani, Kohei; Itabe, Toshikasu

    2001-02-01

    Coherent Doppler Lidar (CDL), which has a capability of 3-D wind velocity measurements, can realize a global measurement of the wind profile in the troposphere from space. ISS(International Space Station) has been constructing from last year, and JEM(Japanese Experimental Module) attached to ISS is scheduled to be provided as a laboratory in space. We have been making a feasibility study for ISS-JEM/2-micrometer CDL. We expect that the ISS might give some technical problems because of a large scale and a man attended station. On the other hand, a measurement accuracy of 1m/s is required from the atmospheric science. We have to analyze the systematic error with considering the error factors to meet this requirement. There are two factors of the wind measurement errors caused by the nutation of ISS?fs attitude. One of them is a change of receiving power, since it should change distances between CDL and a observing point. In this case, we have already shown that the wind error estimated was only ?}0.05m/s (assumed width of pitching angle ;?}3deg). The other factor is a change of orbital Doppler shift. The accuracy of 1m/s is corresopnding to 1MHz. We calculated a frequency of orbital Doppler shift in case of non conical scanning one when ISS has the nutation of attitude with ?}3deg,as a pitching angle and a rolling angle,respectively. The results obtained in this syudy are very useful to design a frequency agile CW laser as a local oscillator.In this paper, we describe more details for our analysis.

  3. Real-time 3D and 4D Fourier domain Doppler optical coherence tomography based on dual graphics processing units.

    PubMed

    Huang, Yong; Liu, Xuan; Kang, Jin U

    2012-09-01

    We present real-time 3D (2D cross-sectional image plus time) and 4D (3D volume plus time) phase-resolved Doppler OCT (PRDOCT) imaging based on configuration of dual graphics processing units (GPU). A GPU-accelerated phase-resolving processing algorithm was developed and implemented. We combined a structural image intensity-based thresholding mask and average window method to improve the signal-to-noise ratio of the Doppler phase image. A 2D simultaneous display of the structure and Doppler flow images was presented at a frame rate of 70 fps with an image size of 1000 × 1024 (X × Z) pixels. A 3D volume rendering of tissue structure and flow images-each with a size of 512 × 512 pixels-was presented 64.9 milliseconds after every volume scanning cycle with a volume size of 500 × 256 × 512 (X × Y × Z) voxels, with an acquisition time window of only 3.7 seconds. To the best of our knowledge, this is the first time that an online, simultaneous structure and Doppler flow volume visualization has been achieved. Maximum system processing speed was measured to be 249,000 A-scans per second with each A-scan size of 2048 pixels.

  4. Real-time 3D and 4D Fourier domain Doppler optical coherence tomography based on dual graphics processing units

    PubMed Central

    Huang, Yong; Liu, Xuan; Kang, Jin U.

    2012-01-01

    We present real-time 3D (2D cross-sectional image plus time) and 4D (3D volume plus time) phase-resolved Doppler OCT (PRDOCT) imaging based on configuration of dual graphics processing units (GPU). A GPU-accelerated phase-resolving processing algorithm was developed and implemented. We combined a structural image intensity-based thresholding mask and average window method to improve the signal-to-noise ratio of the Doppler phase image. A 2D simultaneous display of the structure and Doppler flow images was presented at a frame rate of 70 fps with an image size of 1000 × 1024 (X × Z) pixels. A 3D volume rendering of tissue structure and flow images—each with a size of 512 × 512 pixels—was presented 64.9 milliseconds after every volume scanning cycle with a volume size of 500 × 256 × 512 (X × Y × Z) voxels, with an acquisition time window of only 3.7 seconds. To the best of our knowledge, this is the first time that an online, simultaneous structure and Doppler flow volume visualization has been achieved. Maximum system processing speed was measured to be 249,000 A-scans per second with each A-scan size of 2048 pixels. PMID:23024910

  5. Measurement of the total retinal blood flow using dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes

    PubMed Central

    Doblhoff-Dier, Veronika; Schmetterer, Leopold; Vilser, Walthard; Garhöfer, Gerhard; Gröschl, Martin; Leitgeb, Rainer A.; Werkmeister, René M.

    2014-01-01

    We present a system capable of measuring the total retinal blood flow using a combination of dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes and a fundus camera-based retinal vessel analyzer. Our results show a high degree of conformity of venous and arterial flows, which corroborates the validity of the measurements. In accordance with Murray’s law, the log-log regression coefficient between vessel diameter and blood flow was found to be ~3. The blood’s velocity scaled linearly with the vessel diameter at higher diameters (> 60 µm), but showed a clear divergence from the linear dependence at lower diameters. Good agreement with literature data and the large range and high measurement sensitivity point to a high potential for further investigations. PMID:24575355

  6. Monte Carlo simulation of an optical coherence Doppler tomograph signal: the effect of the concentration of particles in a flow on the reconstructed velocity profile

    SciTech Connect

    Bykov, A V; Kirillin, M Yu; Priezzhev, A V

    2005-02-28

    Model signals of an optical coherence Doppler tomograph (OCDT) are obtained by the Monte Carlo method from a flow of a light-scattering suspension of lipid vesicles (intralipid) at concentrations from 0.7% to 1.5% with an a priori specified parabolic velocity profile. The velocity profile parameters reconstructed from the OCDT signal and scattering orders of the photons contributing to the signal are studied as functions of the suspension concentration. It is shown that the maximum of the reconstructed velocity profile at high concentrations shifts with respect to the symmetry axis of the flow and its value decreases due to a greater contribution from multiply scattered photons. (papers devoted to the 250th anniversary of the moscow state university)

  7. Monitoring of drug and stimulation induced cerebral blood flow velocity changes in rat sensory cortex using spectral domain Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wang, Chuan; Yang, Yong; Ding, Zhihua; Meng, Jie; Wang, Kai; Yang, Wenwei; Xu, Ying

    2011-04-01

    Doppler optical coherence tomography (DOCT) provides a novel method to measure blood flow velocity in vessels with diameter at micrometer scale. In this study, a developed spectral domain DOCT system is applied to monitor cerebral blood flow velocity changes in a rat. An animal model with a cranial window is used, and by application of a drug, light, and electric stimulations, changes in blood flow velocity of the pial artery in sensory cortex are measured in real time. The results show significant differences in blood flow velocity before and after drug administration or light and electric stimulations, demonstrating the feasibility of DOCT in cerebral microcirculation study. Given its noninvasive nature, high spatial resolution, high velocity sensitivity, and high imaging speed, DOCT shows great promise in brain research by imaging blood flow changes at micrometer scale vessels, which helps to understand the pathogenesis of cerebral diseases and neurodegenerative diseases.

  8. Phase-resolved optical coherence tomography and optical Doppler tomography for imaging blood flow in human skin with fast scanning speed and high velocity sensitivity

    SciTech Connect

    Zhao, Yonghua; Chen, Zhongping; Saxer, Christopher; Xiang, Shaohua; Boer, Johannes F. de; Nelson, J. Stuart

    2000-01-15

    We have developed a novel phase-resolved optical coherence tomography (OCT) and optical Doppler tomography (ODT) system that uses phase information derived from a Hilbert transformation to image blood flow in human skin with fast scanning speed and high velocity sensitivity. Using the phase change between sequential scans to construct flow-velocity imaging, this technique decouples spatial resolution and velocity sensitivity in flow images and increases imaging speed by more than 2 orders of magnitude without compromising spatial resolution or velocity sensitivity. The minimum flow velocity that can be detected with an axial-line scanning speed of 400 Hz and an average phase change over eight sequential scans is as low as 10 {mu}m/s , while a spatial resolution of 10 {mu}m is maintained. Using this technique, we present what are to our knowledge the first phase-resolved OCT/ODT images of blood flow in human skin. (c) 2000 Optical Society of America.

  9. Application of low-coherence optical fiber Doppler anemometry to fluid-flow measurement: optical system considerations

    NASA Astrophysics Data System (ADS)

    Boyle, William J. O.; Grattan, Kenneth T. V.; Palmer, Andrew W.; Meggitt, B. T.

    1991-08-01

    A fiber optic Doppler anemometric (FODA) sensor using an optical delay cavity technique and having the advantage of detecting velocity rather than simple speed is outlined. In this sensor the delay in a sensor cavity formed from light back-reflected from a fiber tip (Fresnel reflection) and light back-reflected from particles flowing in a fluid is balanced by the optical delay when light from this sensor cavity passes through a reference cavity formed by a combination of the zero and first diffraction orders produced by a Bragg cell inserted into the optical arrangement. The performance of an experimental sensor based on this scheme is investigated, and velocity measurements using the Doppler shift data from moving objects are presented. The sensitivity of the scheme is discussed, with reference to the other techniques of fluid flow measurement.

  10. Doppler lidar atmospheric wind sensors - A comparative performance evaluation for global measurement applications from earth orbit

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.

    1986-01-01

    A comparison is made of four prominent Doppler lidar systems, ranging in wavelength from the near UV to the middle IR, which are presently being studied for their potential in an earth-orbiting global tropospheric wind field measurement application. The comparison is restricted to relative photon efficiencies, i.e., the required number of transmitted photons per pulse is calculated for each system for midtropospheric velocity estimate uncertainties ranging from + or - 1 to + or - 4 m/s. The results are converted to laser transmitter pulse energy and power requirements. The analysis indicates that a coherent CO2 Doppler lidar operating at 9.11-micron wavelength is the most efficient.

  11. Expected Characteristics of Global Wind Profile Measurements with a Scanning, Hybrid, Doppler Lidar System

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.

    2008-01-01

    Over 20 years of investigation by NASA and NOAA scientists and Doppler lidar technologists into a global wind profiling mission from earth orbit have led to the current favored concept of an instrument with both coherent- and direct-detection pulsed Doppler lidars (i.e., a hybrid Doppler lidar) and a stepstare beam scanning approach covering several azimuth angles with a fixed nadir angle. The nominal lidar wavelengths are 2 microns for coherent detection, and 0.355 microns for direct detection. The two agencies have also generated two sets of sophisticated wind measurement requirements for a space mission: science demonstration requirements and operational requirements. The requirements contain the necessary details to permit mission design and optimization by lidar technologists. Simulations have been developed that connect the science requirements to the wind measurement requirements, and that connect the wind measurement requirements to the Doppler lidar parameters. The simulations also permit trade studies within the multi-parameter space. These tools, combined with knowledge of the state of the Doppler lidar technology, have been used to conduct space instrument and mission design activities to validate the feasibility of the chosen mission and lidar parameters. Recently, the NRC Earth Science Decadal Survey recommended the wind mission to NASA as one of 15 recommended missions. A full description of the wind measurement product from these notional missions and the possible trades available are presented in this paper.

  12. Advanced 2-micron Solid-state Laser for Wind and CO2 Lidar Applications

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Trieu, Bo C.; Petros, Mulugeta; Bai, Yingxin; Petzar, Paul J.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.

    2006-01-01

    Significant advancements in the 2-micron laser development have been made recently. Solid-state 2-micron laser is a key subsystem for a coherent Doppler lidar that measures the horizontal and vertical wind velocities with high precision and resolution. The same laser, after a few modifications, can also be used in a Differential Absorption Lidar (DIAL) system for measuring atmospheric CO2 concentration profiles. The world record 2-micron laser energy is demonstrated with an oscillator and two amplifiers system. It generates more than one joule per pulse energy with excellent beam quality. Based on the successful demonstration of a fully conductive cooled oscillator by using heat pipe technology, an improved fully conductively cooled 2-micron amplifier was designed, manufactured and integrated. It virtually eliminates the running coolant to increase the overall system efficiency and reliability. In addition to technology development and demonstration, a compact and engineering hardened 2-micron laser is under development. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser is expected to be integrated to a lidar system and take field measurements. The recent achievements push forward the readiness of such a laser system for space lidar applications. This paper will review the developments of the state-of-the-art solid-state 2-micron laser.

  13. Progress on High-Energy 2-micron Solid State Laser for NASA Space-Based Wind and Carbon Dioxide Measurements

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.

    2011-01-01

    Sustained research efforts at NASA Langley Research Center during last fifteen years have resulted in significant advancement of a 2-micron diode-pumped, solid-state laser transmitter for wind and carbon dioxide measurements from ground, air and space-borne platforms. Solid-state 2-micron laser is a key subsystem for a coherent Doppler lidar that measures the horizontal and vertical wind velocities with high precision and resolution. The same laser, after a few modifications, can also be used in a Differential Absorption Lidar system for measuring atmospheric CO2 concentration profiles. Researchers at NASA Langley Research Center have developed a compact, flight capable, high energy, injection seeded, 2-micron laser transmitter for ground and airborne wind and carbon dioxide measurements. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser transmitter was integrated into a mobile trailer based coherent Doppler wind and CO2 DIAL system and was deployed during field measurement campaigns. This paper will give an overview of 2-micron solid-state laser technology development and discuss results from recent ground-based field measurements.

  14. Visually evoked changes in the rat retinal blood flow measured with Doppler optical coherence tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Tan, Bingyao; Mason, Erik; MacLellan, Ben; Bizheva, Kostadinka

    2017-02-01

    Visually evoked changes of retinal blood flow can serve as an important research tool to investigate eye disease such as glaucoma and diabetic retinopathy. In this study we used a combined, research-grade, high-resolution Doppler OCT+ERG system to study changes in the retinal blood flow (RBF) and retinal neuronal activity in response to visual stimuli of different intensities, durations and type (flicker vs single flash). Specifically, we used white light stimuli of 10 ms and 200 ms single flash, 1s and 2s for flickers stimuli of 20% duty cycle. The study was conducted in-vivo in pigmented rats. Both single flash (SF) and flicker stimuli caused increase in the RBF. The 10 ms SF stimulus did not generate any consistent measurable response, while the 200 ms SF of the same intensity generated 4% change in the RBF peaking at 1.5 s after the stimulus onset. Single flash stimuli introduced 2x smaller change in RBF and 30% earlier RBF peak response compared to flicker stimuli of the same intensity and duration. Doubling the intensity of SF or flicker stimuli increased the RBF peak magnitude by 1.5x. Shortening the flicker stimulus duration by 2x increased the RBF recovery rate by 2x, however, had no effect on the rate of RBF change from baseline to peak.

  15. Coherent lidar design and performance verification

    NASA Technical Reports Server (NTRS)

    Frehlich, Rod

    1993-01-01

    refractive turbulence on coherent Doppler lidar systems. The analysis of 2 micron Doppler lidar data from Coherent Technologies, Inc. (CTI) has demonstrated many of the advantages of doppler lidar measurements of boundary layer winds. The effects of wind shear and wind turbulence over the pulse volume are probably the dominant source of the reduced performance. The effects of wind shear and wind turbulence on the statistical description of doppler lidar data has been derived and calculated.

  16. Optical system design and experimental evaluation of a coherent Doppler wind Lidar system for the predictive control of wind turbine

    NASA Astrophysics Data System (ADS)

    Shinohara, Leilei; Tauscher, Julian Asche; Beuth, Thorsten; Heussner, Nico; Fox, Maik; Babu, Harsha Umesh; Stork, Wilhelm

    2014-09-01

    The control of wind turbine blade pitch systems by Lidar assisted wind speed prediction has been proposed to increase the electric power generation and reduce the mechanical fatigue load on wind turbines. However, the sticking point of such Lidar systems is the price. Hence, our objective is to develop a more cost efficient Lidar system to support the pitch control of horizontal axis wind turbines and therefore to reduce the material requirement, lower the operation and maintenance costs and decrease the cost of wind energy in the long term. Compared to the state of the art Lidar systems, a laser with a shorter coherence length and a corresponding fiber delay line is introduced for reducing the costs. In this paper we present the experimental evaluation of different sending and receiving optics designs for such a system from a free space laboratory setup.

  17. Temporal characteristics of coherent flow structures generated over alluvial sand dunes, Mississippi River, revealed by acoustic doppler current profiling and multibeam echo sounding

    USGS Publications Warehouse

    Czuba, John A.; Oberg, Kevin A.; Best, Jim L.; Parsons, Daniel R.; Simmons, S. M.; Johnson, K.K.; Malzone, C.

    2009-01-01

    This paper investigates the flow in the lee of a large sand dune located at the confluence of the Mississippi and Missouri Rivers, USA. Stationary profiles collected from an anchored boat using an acoustic Doppler current profiler (ADCP) were georeferenced with data from a real-time kinematic differential global positioning system. A multibeam echo sounder was used to map the bathymetry of the confluence and provided a morphological context for the ADCP measurements. The flow in the lee of a low-angle dune shows good correspondence with current conceptual models of flow over dunes. As expected, quadrant 2 events (upwellings of low-momentum fluid) are associated with high backscatter intensity. Turbulent events generated in the lower lee of a dune near the bed are associated with periods of vortex shedding and wake flapping. Remnant coherent structures that advect over the lower lee of the dune in the upper portion of the water column, have mostly dissipated and contribute little to turbulence intensities. The turbulent events that occupy most of the water column in the upper lee of the dune are associated with periods of wake flapping.

  18. A Polarization-Diversity Homodyne Image-Reject Optical Tranceiver Architecture for Improved Range and Signal Detection in Coherent Doppler Lidars

    NASA Astrophysics Data System (ADS)

    Abari, C. F.; Chu, X.; Mann, J.

    2014-12-01

    Doppler light detection and ranging (lidar) has been used for a few decades for the characterization of wind fields and turbulence structures in the atmosphere. More recently, due to the advances in fiber optic communications, all-fiber coherent Doppler lidars (CDL) have been developed and widely used as a primary instrument for probing the atmospheric boundary layer wind fields. Due to a variety of reasons, all-fiber CDLs have gradually replaced their counterparts benefiting from technologies other than fiber optics. Most CDLs suffer from a number of drawbacks inherent to their principle of operation. For instance, one of the main challenges in CDLs is extracting the signal information from noisy observations, which is common to most opto-electronic systems. Moreover, it is sometimes challenging to extract the sign of the measured radial velocity. Conventionally, CDLs have benefitted from an intermediate frequency (IF) heterodyne receiver architecture for the determination of the radial velocity. In such systems, either the transmitted or the local oscillator (LO) signal is shifted in frequency. Such architectures may suffer from increased noise and spurious effects due to the employment of additional active components, e.g., acousto-optic modulator (AOM), limited measurement bandwidth (BW), and a more sophisticated electronic front-end for signal detection. On the other hand, one of the main challenges in long-range (pulsed) CDLs is the limitations imposed on the pulse repetition rate (PRR) as well as the available transmit power. These restrictions are more significant in all-fiber pulsed CDLs in which Erbium doped fiber amplifiers (EDFA) are employed for the amplification of the optical pulses. In this study, we propose an alternative reconfigurable opto-electronic front-end transceiver architecture in all-fiber CDLs where there is no compromise in the detection BW. Additionally, by benefiting from a polarization diversity architecture we show that both the PRR

  19. Advances in high-energy solid-state 2-micron laser transmitter development for ground and airborne wind and CO2 measurements

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Kavaya, Michael J.; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Modlin, Edward A.; Koch, Grady; Beyon, Jeffrey

    2010-10-01

    Sustained research efforts at NASA Langley Research Center (LaRC) during last fifteen years have resulted in a significant advancement in 2-micron diode-pumped, solid-state laser transmitter for wind and carbon dioxide measurement from ground, air and space-borne platform. Solid-state 2-micron laser is a key subsystem for a coherent Doppler lidar that measures the horizontal and vertical wind velocities with high precision and resolution. The same laser, after a few modifications, can also be used in a Differential Absorption Lidar (DIAL) system for measuring atmospheric CO2 concentration profiles. Researchers at NASA Langley Research Center have developed a compact, flight capable, high energy, injection seeded, 2-micron laser transmitter for ground and airborne wind and carbon dioxide measurements. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser transmitter was integrated into a mobile trailer based coherent Doppler wind and CO2 DIAL system and was deployed during field measurement campaigns. This paper will give an overview of 2- micron solid-state laser technology development and discuss results from recent ground-based field measurements.

  20. Advances in High Energy Solid-State 2-micron Laser Transmitter Development for Ground and Airborne Wind and CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Kavaya, Michael J.; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Modlin, Edward A.; Koch, Grady; hide

    2010-01-01

    Sustained research efforts at NASA Langley Research Center (LaRC) during last fifteen years have resulted in a significant advancement in 2-micron diode-pumped, solid-state laser transmitter for wind and carbon dioxide measurement from ground, air and space-borne platform. Solid-state 2-micron laser is a key subsystem for a coherent Doppler lidar that measures the horizontal and vertical wind velocities with high precision and resolution. The same laser, after a few modifications, can also be used in a Differential Absorption Lidar (DIAL) system for measuring atmospheric CO2 concentration profiles. Researchers at NASA Langley Research Center have developed a compact, flight capable, high energy, injection seeded, 2-micron laser transmitter for ground and airborne wind and carbon dioxide measurements. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser transmitter was integrated into a mobile trailer based coherent Doppler wind and CO2 DIAL system and was deployed during field measurement campaigns. This paper will give an overview of 2-micron solid-state laser technology development and discuss results from recent ground-based field measurements.

  1. Micro-doppler and vibrometry at millimeter and sub-millimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Robertson, Duncan A.; Cassidy, Scott L.

    2013-05-01

    Micro-Doppler is an emerging technique for the measurement and analysis of target modulation characteristics, rooted in the analysis of X-band radar measurements of people. Despite the advantage of higher Doppler sensitivity, there appears to be little such work reported at (sub-) millimeter wave frequencies. We have developed fully coherent, solid state, FMCW radar systems operating at 94 and 340 GHz, suitable for micro-Doppler and vibrometry studies (as well as SAR/ISAR), which make use of DDS chirp generation combined with upconversion and MMIC or Schottky diode frequency multiplication. Due to the low phase noise architecture, the phase (i.e. displacement) sensitivity can be below 1 micron in distance.

  2. Analysis of Coherent Lidar Data

    DTIC Science & Technology

    2007-11-02

    for understanding and predicting atmospheric processes. Recent advances in solid-state lasers have produced coherent Doppler lidar with improved...for the spatial statistics. The performance of coherent Doppler lidar in the weak signal regime was deter- mined by computer simulations and from data...reliable comparison of coherent Doppler lidar wind measurements. A new theoretical prediction of the effects of the pulse averaging of the wind field

  3. Real-time high-velocity resolution color Doppler OCT

    NASA Astrophysics Data System (ADS)

    Westphal, Volker; Yazdanfar, Siavash; Rollins, Andrew M.; Izatt, Joseph A.

    2001-05-01

    Color Doppler optical coherence tomography (CDOCT), also called Optical Doppler Tomography) is a noninvasive optical imaging technique, which allows for micron-scale physiological flow mapping simultaneous with morphological OCT imaging. Current systems for real-time endoscopic optical coherence tomography (EOCT) would be enhanced by the capability to visualize sub-surface blood flow for applications in early cancer diagnosis and the management of bleeding ulcers. Unfortunately, previous implementations of CDOCT have either been sufficiently computationally expensive (employing Fourier or Hilbert transform techniques) to rule out real-time imaging of flow, or have been restricted to imaging of excessively high flow velocities when used in real time. We have developed a novel Doppler OCT signal-processing strategy capable of imaging physiological flow rates in real time. This strategy employs cross-correlation processing of sequential A-scans in an EOCT image, as opposed to autocorrelation processing as described previously. To measure Doppler shifts in the kHz range using this technique, it was necessary to stabilize the EOCT interferometer center frequency, eliminate parasitic phase noise, and to construct a digital cross correlation unit able to correlate signals of megahertz bandwidth by a fixed lag of up to a few ms. The performance of the color Doppler OCT system was demonstrated in a flow phantom, demonstrating a minimum detectable flow velocity of ~0.8 mm/s at a data acquisition rate of 8 images/second (with 480 A-scans/image) using a handheld probe. Dynamic flow as well as using it freehanded was shown. Flow was also detectable in a phantom in combination with a clinical usable endoscopic probe.

  4. Spontaneous generation of vortex and coherent vector beams from a thin-slice c-cut Nd:GdVO4 laser with wide-aperture laser-diode end pumping: application to highly sensitive rotational and translational Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Otsuka, Kenju; Chu, Shu-Chun

    2017-07-01

    Selective excitation of Laguerre-Gauss modes (optical vortices: helical LG0,2 and LG0,1), reflecting their weak transverse cross-saturation of population inversions against a preceding higher-order Ince-Gauss (IG0,2) or Hermite-Gauss (HG2,1) mode, was observed in a thin-slice c-cut Nd:GdVO4 laser with wide-aperture laser-diode end pumping. Single-frequency coherent vector beams were generated through the transverse mode locking of a pair of orthogonally polarized IG2,0 and LG0,2 or HG2,1 and LG0,1 modes. Highly sensitive self-mixing rotational and translational Doppler velocimetry is demonstrated by using vortex and coherent vector beams.

  5. Analysis of Doppler Lidar Data Acquired During the Pentagon Shield Field Campaign

    DTIC Science & Technology

    2011-04-01

    two coherent Doppler lidars deployed during the Pentagon Shield field campaign are analyzed in conjunction with other sensors to characterize the...Observations from two coherent Doppler lidars deployed during the Pentagon Shield field campaign are analyzed in conjunction with other sensors to... coherent Doppler lidars deployed during the Pentagon Shield field campaign are analyzed in conjunction with other sensors to characterize the overall

  6. Doppler and the Doppler Effect.

    DTIC Science & Technology

    1984-06-01

    Doppler Applications Doppler Effect Roemer Doppler Principle Bradley Relative motion Velocity History Light Velocity 20. ABSTRACT (Continue on reverse...of Colorado, Boulder, CO 11-14 Jan 1984 5 1. Historical Background The astronomer Olaf Roemer determined the velocity of light in 1676 from time...approached Jupiter and longer when it receded from Jupiter. In effect, Roemer used a Doppler method in determining the velocity of light . [2 ] In 1727

  7. Doppler tracking of planetary spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.

    1992-01-01

    This article concerns the measurement of Doppler shift on microwave links that connect planetary spacecraft with the Deep Space Network. Such measurements are made by tracking the Doppler effect with phase-locked loop receivers. A description of equipment and techniques as well as a summary of the appropriate mathematical models are given. The two-way Doppler shift is measured by transmitting a highly-stable microwave (uplink) carrier from a ground station, having the spacecraft coherently transpond this carrier, and using a phase-locked loop receiver at the ground station to track the returned (downlink) carrier. The largest sources of measurement error are usually plasma noise and thermal noise. The plasma noise, which may originate in the ionosphere or the solar corona, is discussed; and a technique to partially calibrate its effect, involving the use of two simultaneous downlink carriers that are coherently related, is described. Range measurements employing Doppler rate-aiding are also described.

  8. Theoretical simulation of a 2 micron airborne solid state laser anemometer

    NASA Technical Reports Server (NTRS)

    Imbert, Beatrice; Cariou, Jean-Pierre

    1992-01-01

    In the near future, military aircraft will need to know precisely their true airspeed in order to optimize flight conditions. In comparison with classical anemometer probes, an airborne Doppler lidar allows measurement of the air velocity without influence from aircraft aerodynamic disturbance. While several demonstration systems of heterodyne detection using a CO2 laser have been reported, improvements in the technology of solid state lasers have recently opened up the possibility that these devices can be used as an alternative to CO2 laser systems. In particular, a diode pumped Tm:Ho:YAG laser allows a reliable compact airborne system with an eye safe wavelength (lambda = 2.09 microns) to be achieved. The theoretical study of performances of a coherent lidar using a solid state diode pumped Tm:Ho:YAG laser, caled SALSA, for measuring aircraft airspeed relative to atmospheric aerosols is described. A computer simulation was developed in order to modelize the Doppler anemometer in the function of atmospheric propagation and optical design. A clever analysis of the power budget on the detector area allows optical characteristic parameters of the system to be calculated, and then it can be used to predict performances of the Doppler system. Estimating signal to noise ratios (SNR) and heterodyne efficiency provides the available energy of speed measurement as well as a useful measurement of the alignment of the backscattered and reference fields on the detector.

  9. Theoretical simulation of a 2 micron airborne solid state laser anemometer

    NASA Technical Reports Server (NTRS)

    Imbert, Beatrice; Cariou, Jean-Pierre

    1992-01-01

    In the near future, military aircraft will need to know precisely their true airspeed in order to optimize flight conditions. In comparison with classical anemometer probes, an airborne Doppler lidar allows measurement of the air velocity without influence from aircraft aerodynamic disturbance. While several demonstration systems of heterodyne detection using a CO2 laser have been reported, improvements in the technology of solid state lasers have recently opened up the possibility that these devices can be used as an alternative to CO2 laser systems. In particular, a diode pumped Tm:Ho:YAG laser allows a reliable compact airborne system with an eye safe wavelength (lambda = 2.09 microns) to be achieved. The theoretical study of performances of a coherent lidar using a solid state diode pumped Tm:Ho:YAG laser, caled SALSA, for measuring aircraft airspeed relative to atmospheric aerosols is described. A computer simulation was developed in order to modelize the Doppler anemometer in the function of atmospheric propagation and optical design. A clever analysis of the power budget on the detector area allows optical characteristic parameters of the system to be calculated, and then it can be used to predict performances of the Doppler system. Estimating signal to noise ratios (SNR) and heterodyne efficiency provides the available energy of speed measurement as well as a useful measurement of the alignment of the backscattered and reference fields on the detector.

  10. Partially coherent radiation from lasers, undulators, and laser produced plasmas

    NASA Astrophysics Data System (ADS)

    Iskander, Nasif; Wang, Nadine

    The coherence properties of several existing and proposed sources of soft X-rays are compared with emphasis on the LLNL Se laser. Average and peak values of spectral brightness and coherent power are calculated and plotted. Coherent power is plotted in units of watts for coherence lengths of 1 micron and 10 microns (two useful lengths of experiments) as well as 200 microns (to illustrate the natural long coherence length of the LLNL Se laser).

  11. 30-micron heterodyne receiver

    NASA Technical Reports Server (NTRS)

    Kostiuk, Theodor; Spears, David L.

    1987-01-01

    Advantages and constraints of remote measurements using heterodyne spectroscopy near 30 microns are discussed. The state of the art of wideband HgCdTe photomixers and PbSnSe diode-laser local oscillators being developed for FIR heterodyne receivers is described. The first compact 30-micron heterodyne radiometer was built, and initial results at 28-microns show about 2-percent mixer efficiency for a 500-MHz-bandwidth receiver. Factors limiting receiver performance are discussed, along with the projected sensitivity of new interdigitated-electrode HgCdTe photoconductor mixers being developed for operation up to 200 microns.

  12. Coherent signal processing in optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Kulkarni, Manish Dinkarrao

    1999-09-01

    Optical coherence tomography (OCT) is a novel method for non-invasive sub-surface imaging of biological tissue micro-structures. OCT achieves high spatial resolution ( ~ 15 m m in three dimensions) using a fiber-optically integrated system which is suitable for application in minimally invasive diagnostics, including endoscopy. OCT uses an optical heterodyne detection technique based on white light interferometry. Therefore extremely faint reflections ( ~ 10 fW) are routinely detected with high spatial localization. The goal of this thesis is twofold. The first is to present a theoretical model for describing image formation in OCT, and attempt to enhance the current level of understanding of this new modality. The second objective is to present signal processing methods for improving OCT image quality. We present deconvolution algorithms to obtain improved longitudinal resolution in OCT. This technique may be implemented without increasing system complexity as compared to current clinical OCT systems. Since the spectrum of the light backscattered from bio-scatterers is closely associated with ultrastructural variations in tissue, we propose a new technique for measuring spectra as a function of depth. This advance may assist OCT in differentiating various tissue types and detecting abnormalities within a tissue. In addition to depth resolved spectroscopy, Doppler processing of OCT signals can also improve OCT image contrast. We present a new technique, termed color Doppler OCT (CDOCT). It is an innovative extension of OCT for performing spatially localized optical Doppler velocimetry. Micron-resolution imaging of blood flow in sub-surface vessels in living tissue using CDOCT is demonstrated. The fundamental issues regarding the trade- off between the velocity estimation precision and image acquisition rate are presented. We also present novel algorithms for high accuracy velocity estimation. In many blood vessels velocities tend to be on the order of a few cm

  13. A Doppler lidar with CO2-laser intracavity detection

    NASA Astrophysics Data System (ADS)

    Godlevskii, A. P.; Gordov, E. P.; Zhiliba, A. I.; Sharin, P. P.

    A version of a high-sensitive Doppler lidar, based on intracavity coherent laser detection is described. The device consists of a CO2 laser, transmitting-receiving optical system, and signal-processing unit. Laser-intensity stabilization is achieved by decreasing the mechanical disturbance of the laser resonator, and the optical tract is formed by a Cassegrain telescope. A portion of the laser beam reflected back by a Breuster window of the gas discharge tube is focused by a spherical mirror onto a photodetector. Results of laboratory and real-atmosphere experiments are reported, and it is shown that vibrations of a retroreflector with an amplitude of 50 micron are detected at distances up to 500 m.

  14. LASER APPLICATIONS IN MEDICINE: Analysis of distortions in the velocity profiles of suspension flows inside a light-scattering medium upon their reconstruction from the optical coherence Doppler tomograph signal

    NASA Astrophysics Data System (ADS)

    Bykov, A. V.; Kirillin, M. Yu; Priezzhev, A. V.

    2005-11-01

    Model signals from one and two plane flows of a particle suspension are obtained for an optical coherence Doppler tomograph (OCDT) by the Monte-Carlo method. The optical properties of particles mimic the properties of non-aggregating erythrocytes. The flows are considered in a stationary scattering medium with optical properties close to those of the skin. It is shown that, as the flow position depth increases, the flow velocity determined from the OCDT signal becomes smaller than the specified velocity and the reconstructed profile extends in the direction of the distant boundary, which is accompanied by the shift of its maximum. In the case of two flows, an increase in the velocity of the near-surface flow leads to the overestimated values of velocity of the reconstructed profile of the second flow. Numerical simulations were performed by using a multiprocessor parallel-architecture computer.

  15. Long-range, wide-field swept-source optical coherence tomography with GPU accelerated digital lock-in Doppler vibrography for real-time, in vivo middle ear diagnostics

    PubMed Central

    MacDougall, Dan; Farrell, Joshua; Brown, Jeremy; Bance, Manohar; Adamson, Robert

    2016-01-01

    We present the design, implementation and validation of a swept-source optical coherence tomography (OCT) system for real-time imaging of the human middle ear in live patients. Our system consists of a highly phase-stable Vernier-tuned distributed Bragg-reflector laser along with a real-time processing engine implemented on a graphics processing unit. We use the system to demonstrate, for the first time in live subjects, real-time Doppler measurements of middle ear vibration in response to sound, video rate 2D B-mode imaging of the middle ear and 3D volumetric B-mode imaging. All measurements were performed non-invasively through the intact tympanic membrane demonstrating that the technology is readily translatable to the clinic. PMID:27896001

  16. The Effect of Doppler Frequency Shift, Frequency Offset of the Local Oscillators, and Phase Noise on the Performance of Coherent OFDM Receivers

    NASA Technical Reports Server (NTRS)

    Xiong, Fuqin; Andro, Monty

    2001-01-01

    This paper first shows that the Doppler frequency shift affects the frequencies of the RF carrier, subcarriers, envelope, and symbol timing by the same percentage in an Orthogonal Frequency Division Multiplexing (OFDM) signal or any other modulated signals. Then the SNR degradation of an OFDM system due to Doppler frequency shift, frequency offset of the local oscillators and phase noise is analyzed. Expressions are given and values for 4-, 16-, 64-, and 256-QAM OFDM systems are calculated and plotted. The calculations show that the Doppler shift of the D3 project is about 305 kHz, and the degradation due to it is about 0.01 to 0.04 dB, which is negligible. The degradation due to frequency offset and phase noise of local oscillators will be the main source of degradation. To keep the SNR degradation under 0.1 dB, the relative frequency offset due to local oscillators must be below 0.01 for the 16 QAM-OFDM. This translates to an offset of 1.55 MHz (0.01 x 155 MHz) or a stability of 77.5 ppm (0.01 x 155 MHz/20 GHz) for the DI project. To keep the SNR degradation under 0.1 dB, the relative linewidth (0) due to phase noise of the local oscillators must be below 0.0004 for the 16 QAM-OFDM. This translates to a linewidth of 0.062 MHz (0.0004 x 155 MHz) of the 20 GHz RIF carrier. For a degradation of 1 dB, beta = 0.04, and the linewidth can be relaxed to 6.2 MHz.

  17. Doppler echocardiography

    SciTech Connect

    Labovitz, A.J.; Williams, G.A.

    1988-01-01

    The authors are successful in presenting a basic book on clinical quantitative Doppler echocardiography. It is not intended to be a comprehensive text, but it does cover clinical applications in a succinct fashion. Only the more common diseases in the adult are considered. The subjects are presented logically and are easy to comprehend. The illustrations are good, and the book is paperbound. The basic principles of Doppler echocardiography are presented briefly. The book ends with chapters on left ventricular function (stroke volume and cardiac output), congenital heart disease, and color Doppler echo-cardiography. There are numerous references and a good glossary and index.

  18. Remote Sensing of Wind Fields and Aerosol Distribution with Airborne Scanning Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry; Cutten, Dean R.; Johnson, Steven C.; Jazembski, Maurice; Arnold, James E. (Technical Monitor)

    2001-01-01

    The coherent Doppler laser radar (lidar), when operated from an airborne platform, is a unique tool for the study of atmospheric and surface processes and features. This is especially true for scientific objectives requiring measurements in optically-clear air, where other remote sensing technologies such as Doppler radar are typically at a disadvantage. The atmospheric lidar remote sensing groups of several US institutions, led by Marshall Space Flight Center, have developed an airborne coherent Doppler lidar capable of mapping the wind field and aerosol structure in three dimensions. The instrument consists of an eye-safe approx. 1 Joule/pulse lidar transceiver, telescope, scanner, inertial measurement unit, and flight computer system to orchestrate all subsystem functions and tasks. The scanner is capable of directing the expanded lidar beam in a variety of ways, in order to extract vertically-resolved wind fields. Horizontal resolution is approx. 1 km; vertical resolution is even finer. Winds are obtained by measuring backscattered, Doppler-shifted laser radiation from naturally-occurring aerosol particles (of order 1 micron diameter). Measurement coverage depends on aerosol spatial distribution and composition. Velocity accuracy has been verified to be approx. 1 meter per second. A variety of applications have been demonstrated during the three flight campaigns conducted during 1995-1998. Examples will be shown during the presentation. In 1995, boundary layer winds over the ocean were mapped with unprecedented resolution. In 1996, unique measurements were made of. flow over the complex terrain of the Aleutian Islands; interaction of the marine boundary layer jet with the California coastal mountain range; a weak dry line in Texas - New Mexico; the angular dependence of sea surface scattering; and in-flight radiometric calibration using the surface of White Sands National Monument. In 1998, the first measurements of eyewall and boundary layer winds within a

  19. Semiconductor Reference Oscillator Development for Coherent Detection Optical Remote Sensing Applications

    NASA Technical Reports Server (NTRS)

    Tratt, David M.; Mansour, Kamjou; Menzies, Robert T.; Qiu, Yueming; Forouhar, Siamak; Maker, Paul D.; Muller, Richard E.

    2001-01-01

    The NASA Earth Science Enterprise Advanced Technology Initiatives Program is supporting a program for the development of semiconductor laser reference oscillators for application to coherent optical remote sensing from Earth orbit. Local oscillators provide the frequency reference required for active spaceborne optical remote sensing concepts that involve heterodyne (coherent) detection. Two recent examples of such schemes are Doppler wind lidar and tropospheric carbon dioxide measurement by laser absorption spectrometry, both of which are being proposed at a wavelength of 2.05 microns. Frequency-agile local oscillator technology is important to such applications because of the need to compensate for large platform-induced Doppler components that would otherwise interfere with data interpretation. Development of frequency-agile local oscillator approaches has heretofore utilized the same laser material as the transmitter laser (Tm,Ho:YLF in the case of the 2.05-micron wavelength mentioned above). However, a semiconductor laser-based frequency-agile local oscillator offers considerable scope for reduced mechanical complexity and improved frequency agility over equivalent crystal laser devices, while their potentially faster tuning capability suggest the potential for greater scanning versatility. The program we report on here is specifically tasked with the development of prototype novel architecture semiconductor lasers with the power, tunability, and spectral characteristics required for coherent Doppler lidar. The baseline approach for this work is the distributed feedback (DFB) laser, in which gratings are etched into the semiconductor waveguide structures along the entire length of the laser cavity. However, typical DFB lasers at the wavelength of interest have linewidths that exhibit unacceptable growth when driven at the high currents and powers that are required for the Doppler lidar application. Suppression of this behavior by means of corrugation pitch

  20. Semiconductor Reference Oscillator Development for Coherent Detection Optical Remote Sensing Applications

    NASA Technical Reports Server (NTRS)

    Tratt, David M.; Mansour, Kamjou; Menzies, Robert T.; Qiu, Yueming; Forouhar, Siamak; Maker, Paul D.; Muller, Richard E.

    2001-01-01

    The NASA Earth Science Enterprise Advanced Technology Initiatives Program is supporting a program for the development of semiconductor laser reference oscillators for application to coherent optical remote sensing from Earth orbit. Local oscillators provide the frequency reference required for active spaceborne optical remote sensing concepts that involve heterodyne (coherent) detection. Two recent examples of such schemes are Doppler wind lidar and tropospheric carbon dioxide measurement by laser absorption spectrometry, both of which are being proposed at a wavelength of 2.05 microns. Frequency-agile local oscillator technology is important to such applications because of the need to compensate for large platform-induced Doppler components that would otherwise interfere with data interpretation. Development of frequency-agile local oscillator approaches has heretofore utilized the same laser material as the transmitter laser (Tm,Ho:YLF in the case of the 2.05-micron wavelength mentioned above). However, a semiconductor laser-based frequency-agile local oscillator offers considerable scope for reduced mechanical complexity and improved frequency agility over equivalent crystal laser devices, while their potentially faster tuning capability suggest the potential for greater scanning versatility. The program we report on here is specifically tasked with the development of prototype novel architecture semiconductor lasers with the power, tunability, and spectral characteristics required for coherent Doppler lidar. The baseline approach for this work is the distributed feedback (DFB) laser, in which gratings are etched into the semiconductor waveguide structures along the entire length of the laser cavity. However, typical DFB lasers at the wavelength of interest have linewidths that exhibit unacceptable growth when driven at the high currents and powers that are required for the Doppler lidar application. Suppression of this behavior by means of corrugation pitch

  1. Laser Doppler And Range Systems For Spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, P. W.; Gagliardi, R. M.

    1990-01-01

    Report discusses two types of proposed laser systems containing active transponders measuring distance (range) and line-of-sight velocity (via Doppler effect) between deep space vehicle and earth-orbiting satellite. Laser system offers diffraction advantage over microwave system. Delivers comparable power to distant receiver while using smaller transmitting and receiving antennas and less-powerful transmitter. Less subject to phase scintillations caused by passage through such inhomogeneous media as solar corona. One type of system called "incoherent" because range and Doppler measurements do not require coherence with laser carrier signals. Other type of system called "coherent" because successful operation requires coherent tracking of laser signals.

  2. WFIRST Needs 3 Microns

    NASA Astrophysics Data System (ADS)

    Wright, Edward L.

    2012-05-01

    The Wide-Field InfraRed Survey Telescope (WFIRST) should work out to 4 microns instead of the current 2 or 2.5 micron cutoff for maximum science return. The signal-to-noise ratio on distant faint galaxies and quasars is maximized in the zodiacal light minimum at 3-4 microns. The SNR for measuring shapes for weak lensing also depends on PSF size relative to the galaxy size, but for an exponential scale length of 0.1" at z=2 (850 pc), the optimum wavelength is in the 2-3 micron range. While the PSF of a 1.3 m telescope at 3 microns has a FWHM of 0.5", this is still smaller than the seeing-limited PSF of LSST which plans to do weak lensing. The scatter in supernova Hubble diagrams is much lower for data taken in the rest frame near-infrared (0.11 mag) compared to rest-frame optical (0.18 mag), so at redshift z=2 one desires photometry at 3.75 microns. So each supernova observed in the rest-frame near-IR is worth 2-3 supernova observed in the rest frame optical. Microlensing is looking at zero redshift stars, and would use a filter to isolate an optimal bandpass, so it would be no worse with a longer detector cutoff wavelength. Slitless spectroscopy to measure Baryon Acoustic Oscillations will concentrate on redshifted H-alpha, and use a filter to select the desired redshift range, so a longer cutoff wavelength just gives more flexibility in targeting the redshift range. Thus the performance of WFIRST with a long cutoff wavelength is either substantially improved (for SNe and the high latitude survey), slightly improved (for weak lensing) or not hurt (for microlensing and BAO), and the overlap with the capabilities of Euclid is much reduced. NASA support for my participation on the WFIRST SDT is acknowledged.

  3. Continuous wave ultrasonic Doppler tomography

    PubMed Central

    Liang, Haidong-Dong; Tsui, Chun Sing Louis; Halliwell, Michael; Wells, Peter N. T.

    2011-01-01

    In continuous wave ultrasonic Doppler tomography (DT), the ultrasonic beam moves relative to the scanned object to acquire Doppler-shifted frequency spectra which correspond to cross-range projections of the scattering and reflecting structures within the object. The relative motion can be circular or linear. These data are then backprojected to reconstruct the two-dimensional image of the object cross section. By using coherent processing, the spatial resolution of ultrasonic DT is close to an order of magnitude better than that of traditional pulse-echo imaging at the same ultrasound frequency. PMID:22866236

  4. ANL Doppler flowmeter

    NASA Astrophysics Data System (ADS)

    Karplus, H. B.; Raptis, A. C.; Lee, S.; Simpson, T.

    1985-10-01

    A flowmeter has been developed for measuring flow velocity in hot slurries. The flowmeter works on an ultrasonic Doppler principle in which ultrasound is injected into the flowing fluid through the solid pipe wall. Isolating waveguides separate the hot pipe from conventional ultrasonic transducers. Special clamp-on high-temperature transducers also can be adapted to work well in this application. Typical flows in pilot plants were found to be laminar, giving rise to broad-band Doppler spectra. A special circuit based on a servomechanism sensor was devised to determine the frequency average of such a broad spectrum. The device was tested at different pilot plants. Slurries with particulates greater than 70 microns (0.003 in.) yielded good signals, but slurries with extremely fine particulates were unpredictable. Small bubbles can replace the coarse particles to provide a good signal if there are not too many. Successful operation with very fine particulate slurries may have been enhanced by the presence of microbubbles.

  5. WIND MEASUREMENTS WITH HIGH-ENERGY DOPPLER LIDAR

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Kavaya, Michael J.; Barnes, Bruce W.; Beyon, Jeffrey Y.; Petros, Mulugeta; Jirong, Yu; Amzajerdian, Farzin; Slingh, Upendra N.

    2006-01-01

    Coherent lidars at 2-micron wavelengths from holmium or thulium solid-state lasers have been in use to measure wind for applications in meteorology, aircraft wake vortex tracking, and turbulence detection [1,2,3] These field-deployed lidars, however, have generally been of a pulse energy of a few millijoules, limiting their range capability or restricting operation to regions of high aerosol concentration such as the atmospheric boundary layer. Technology improvements in the form of high-energy pulsed lasers, low noise detectors, and high optical quality telescopes are being evaluated to make wind measurements to long ranges or low aerosol concentrations. This research is aimed at developing lidar technology for satellite-based observation of wind on a global scale. The VALIDAR project was initiated to demonstrate a high pulse energy coherent Doppler lidar. VALIDAR gets its name from the concept of validation lidar, in that it can serve as a calibration and validation source for future airborne and spaceborne lidar missions. VALIDAR is housed within a mobile trailer for field measurements.

  6. Vertical Velocity Statistics Derived from the New ARM Doppler Lidars

    NASA Astrophysics Data System (ADS)

    Newsom, R. K.

    2012-12-01

    Accurate height-resolved measurements of higher-order statistical moments of vertical velocity fluctuations are crucial for improved understanding of convective initiation and the refinement of turbulence and surface layer parameterization schemes used in large eddy simulations and cloud resolving models. In October 2010 the US Department of Energy's Atmospheric Radiation Measurement (ARM) program added three coherent Doppler lidars to it's extensive suite of ground based instrumentation in order to fill a long-standing observational gap within the ARM program, i.e. measurement of clear-air vertical velocity profiles through the depth of the atmospheric boundary layer. The ARM Doppler lidars operate in the near-IR (1.5 microns) and are sensitive to backscatter from aerosol. The line-of-sight component of air velocity is obtained by measuring the Doppler shift induced by the motion of the aerosols. Vertical velocity measurements are thus obtained when the lidar beam is directed vertically. Under moderate to high signal-to-noise conditions the instruments are capable of making measurements with a precision of better than 10 cm s-1. The new systems have been deployed at ARM's Southern Great Plains (SGP) site in north central Oklahoma, the Tropical Western Pacific site in Darwin, Australia (TWP-Darwin), and the first ARM mobile facility. All three systems have proven to be highly reliable with nearly continuous operation since their initial deployments. The lidars are configured to spend the majority of their time in a vertical staring mode. The resulting datastreams consist of high spatial and temporal resolution, clear-air vertical velocity observations spanning multiple years. In this study, we present vertical velocity statistics derived from more than 18 months of 1 s resolution measurements taken at the two fixed sites, SGP and TWP-Darwin. The vertical structure of variance, skewness and kurtosis, as well as the diurnal and seasonal variability are compared and

  7. Method and apparatus for optical Doppler tomographic imaging of fluid flow velocity in highly scattering media

    DOEpatents

    Nelson, John Stuart; Milner, Thomas Edward; Chen, Zhongping

    1999-01-01

    Optical Doppler tomography permits imaging of fluid flow velocity in highly scattering media. The tomography system combines Doppler velocimetry with high spatial resolution of partially coherent optical interferometry to measure fluid flow velocity at discrete spatial locations. Noninvasive in vivo imaging of blood flow dynamics and tissue structures with high spatial resolutions of the order of 2 to 10 microns is achieved in biological systems. The backscattered interference signals derived from the interferometer may be analyzed either through power spectrum determination to obtain the position and velocity of each particle in the fluid flow sample at each pixel, or the interference spectral density may be analyzed at each frequency in the spectrum to obtain the positions and velocities of the particles in a cross-section to which the interference spectral density corresponds. The realized resolutions of optical Doppler tomography allows noninvasive in vivo imaging of both blood microcirculation and tissue structure surrounding the vessel which has significance for biomedical research and clinical applications.

  8. Periodic, pseudonoise waveforms for multifunction coherent ladar.

    PubMed

    Dierking, Matthew P; Duncan, Bradley D

    2010-04-01

    We report the use of periodic, pseudonoise waveforms in a multifunction coherent ladar system. We exploit the Doppler sensitivity of these waveforms, as well as agile processing, to enable diverse ladar functions, including high range resolution imaging, macro-Doppler imaging, synthetic aperture ladar, and range-resolved micro-Doppler imaging. We present analytic expressions and simulations demonstrating the utility of pseudonoise waveforms for each of the ladar modes. We also discuss a laboratory pseudonoise ladar system that was developed to demonstrate range compression and range-resolved micro-Doppler imaging, as well as the phase recovery common to each of the coherent modes.

  9. Ultraviolet-excimer laser-based incoherent Doppler lidar system

    NASA Technical Reports Server (NTRS)

    Mcdermid, I. Stuart; Laudenslager, James B.; Rees, David

    1985-01-01

    The topics covered include the following: principles of Doppler measurements, laser backscatter, eye safety, demonstration concepts, the wavelength-meter, the interferometer detector, return signal model, and comparison of incoherent and coherent lidars.

  10. Doppler flowmeter

    DOEpatents

    Karplus, Henry H. B.; Raptis, Apostolos C.

    1983-01-01

    A Doppler flowmeter impulses an ultrasonic fixed-frequency signal obliquely into a slurry flowing in a pipe and a reflected signal is detected after having been scattered off of the slurry particles, whereby the shift in frequencies between the signals is proportional to the slurry velocity and hence slurry flow rate. This flowmeter filters the Doppler frequency-shift signal, compares the filtered and unfiltered shift signals in a divider to obtain a ratio, and then further compares this ratio against a preset fractional ratio. The flowmeter utilizes a voltage-to-frequency convertor to generate a pulsed signal having a determinable rate of repetition precisely proportional to the divergence of the ratios. The pulsed signal serves as the input control for a frequency-controlled low-pass filter, which provides thereby that the cutoff frequency of the filtered signal is known. The flowmeter provides a feedback control by minimizing the divergence. With the cutoff frequency and preset fractional ratio known, the slurry velocity and hence flow will also be determinable.

  11. Doppler flowmeter

    DOEpatents

    Karplus, H.H.B.; Raptis, A.C.

    1981-11-13

    A Doppler flowmeter impulses an ultrasonic fixed-frequency signal obliquely into a slurry flowing in a pipe and a reflected signal is detected after having been scattered off of the slurry particles, whereby the shift in frequencies between the signals is proportional to the slurry velocity and hence slurry flow rate. This flowmeter filters the Doppler frequency-shift signal, compares the filtered and unfiltered shift signals in a divider to obtain a ratio, and then further compares this ratio against a preset fractional ratio. The flowmeter utilizes a voltage-to-frequency convertor to generate a pulsed signal having a determinable rate of repetition precisely proportional to the divergence of the ratios. The pulsed signal serves as the input control for a frequency-controlled low-pass filter, which provides thereby that the cutoff frequency of the filtered signal is known. The flowmeter provides a feedback control by minimizing the divergence. With the cutoff frequency and preset fractional ratio known, the slurry velocity and hence flow will also be determinable.

  12. Micronized grinding apparatus

    SciTech Connect

    Williams, R.M.

    1985-06-11

    Apparatus for grinding coal to micron fineness having a grinding chamber with a grinding surface supported by a circumferential wall in the grinding chamber, a plurality of grinding rolls orbiting in the grinding chamber for grinding the coal, air supply bustle surrounding the grinding chamber, air flow restrictor means opening from the air supply bustle to the grinding chamber to create a back pressure in the air supply bustle for substantially evenly distributing the air supplied to the grinding chamber around the circumference of the grinding chamber, and wherein the restrictor means directs the air flow tangentially relative to the circumferential wall of the grinding chamber so that the coal particles are caught up in a cyclonic movement having a large initial horizontally directed force to maintain a body of coal particles in the orbit of the grinding rolls, which horizontal force gradually diminishes as the vertical force component of the air flow lifts the ground coal particles out of the grinding chamber.

  13. Sub-micron filter

    DOEpatents

    Tepper, Frederick [Sanford, FL; Kaledin, Leonid [Port Orange, FL

    2009-10-13

    Aluminum hydroxide fibers approximately 2 nanometers in diameter and with surface areas ranging from 200 to 650 m.sup.2/g have been found to be highly electropositive. When dispersed in water they are able to attach to and retain electronegative particles. When combined into a composite filter with other fibers or particles they can filter bacteria and nano size particulates such as viruses and colloidal particles at high flux through the filter. Such filters can be used for purification and sterilization of water, biological, medical and pharmaceutical fluids, and as a collector/concentrator for detection and assay of microbes and viruses. The alumina fibers are also capable of filtering sub-micron inorganic and metallic particles to produce ultra pure water. The fibers are suitable as a substrate for growth of cells. Macromolecules such as proteins may be separated from each other based on their electronegative charges.

  14. Doppler weather radar with predictive wind shear detection capabilities

    NASA Technical Reports Server (NTRS)

    Kuntman, Daryal

    1991-01-01

    The status of Bendix research on Doppler weather radar with predictive wind shear detection capability is given in viewgraph form. Information is given on the RDR-4A, a fully coherent, solid state transmitter having Doppler turbulence capability. Frequency generation data, plans, modifications, system characteristics and certification requirements are covered.

  15. The NASA/MSFC Coherent Lidar Technology Advisory Team

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.

    1999-01-01

    The SPAce Readiness Coherent Lidar Experiment (SPARCLE) mission was proposed as a low cost technology demonstration mission, using a 2-micron, 100-mJ, 6-Hz, 25-cm, coherent lidar system based on demonstrated technology. SPARCLE was selected in late October 1997 to be NASA's New Millennium Program (NMP) second earth-observing (EO-2) mission. To maximize the success probability of SPARCLE, NASA/MSFC desired expert guidance in the areas of coherent laser radar (CLR) theory, CLR wind measurement, fielding of CLR systems, CLR alignment validation, and space lidar experience. This led to the formation of the NASA/MSFC Coherent Lidar Technology Advisory Team (CLTAT) in December 1997. A threefold purpose for the advisory team was identified as: 1) guidance to the SPARCLE mission, 2) advice regarding the roadmap of post-SPARCLE coherent Doppler wind lidar (CDWL) space missions and the desired matching technology development plan 3, and 3) general coherent lidar theory, simulation, hardware, and experiment information exchange. The current membership of the CLTAT is shown. Membership does not result in any NASA or other funding at this time. We envision the business of the CLTAT to be conducted mostly by email, teleconference, and occasional meetings. The three meetings of the CLTAT to date, in Jan. 1998, July 1998, and Jan. 1999, have all been collocated with previously scheduled meetings of the Working Group on Space-Based Lidar Winds. The meetings have been very productive. Topics discussed include the SPARCLE technology validation plan including pre-launch end-to-end testing, the space-based wind mission roadmap beyond SPARCLE and its implications on the resultant technology development, the current values and proposed future advancement in lidar system efficiency, and the difference between using single-mode fiber optical mixing vs. the traditional free space optical mixing.

  16. The NASA/MSFC Coherent Lidar Technology Advisory Team

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.

    1999-01-01

    The SPAce Readiness Coherent Lidar Experiment (SPARCLE) mission was proposed as a low cost technology demonstration mission, using a 2-micron, 100-mJ, 6-Hz, 25-cm, coherent lidar system based on demonstrated technology. SPARCLE was selected in late October 1997 to be NASA's New Millennium Program (NMP) second earth-observing (EO-2) mission. To maximize the success probability of SPARCLE, NASA/MSFC desired expert guidance in the areas of coherent laser radar (CLR) theory, CLR wind measurement, fielding of CLR systems, CLR alignment validation, and space lidar experience. This led to the formation of the NASA/MSFC Coherent Lidar Technology Advisory Team (CLTAT) in December 1997. A threefold purpose for the advisory team was identified as: 1) guidance to the SPARCLE mission, 2) advice regarding the roadmap of post-SPARCLE coherent Doppler wind lidar (CDWL) space missions and the desired matching technology development plan 3, and 3) general coherent lidar theory, simulation, hardware, and experiment information exchange. The current membership of the CLTAT is shown. Membership does not result in any NASA or other funding at this time. We envision the business of the CLTAT to be conducted mostly by email, teleconference, and occasional meetings. The three meetings of the CLTAT to date, in Jan. 1998, July 1998, and Jan. 1999, have all been collocated with previously scheduled meetings of the Working Group on Space-Based Lidar Winds. The meetings have been very productive. Topics discussed include the SPARCLE technology validation plan including pre-launch end-to-end testing, the space-based wind mission roadmap beyond SPARCLE and its implications on the resultant technology development, the current values and proposed future advancement in lidar system efficiency, and the difference between using single-mode fiber optical mixing vs. the traditional free space optical mixing.

  17. Solid-State 2-Micron Laser Transmitter Advancement for Wind and Carbon Dioxide Measurements From Ground, Airborne, and Space-Based Lidar Systems

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Kavaya, Michael J.; Koch, Grady; Yu, Jirong; Ismail, Syed

    2008-01-01

    NASA Langley Research Center has been developing 2-micron lidar technologies over a decade for wind measurements, utilizing coherent Doppler wind lidar technique and carbon dioxide measurements, utilizing Differential Absorption Lidar (DIAL) technique. Significant advancements have been made towards developing state-of-the-art technologies towards laser transmitters, detectors, and receiver systems. These efforts have led to the development of solid-state lasers with high pulse energy, tunablility, wavelength-stability, and double-pulsed operation. This paper will present a review of these technological developments along with examples of high resolution wind and high precision CO2 DIAL measurements in the atmosphere. Plans for the development of compact high power lasers for applications in airborne and future space platforms for wind and regional to global scale measurement of atmospheric CO2 will also be discussed.

  18. Dual Beam Doppler Optical Coherence Angiography

    NASA Astrophysics Data System (ADS)

    Yasuno, Yoshiaki; Makita, Shuichi; Jaillon, Franck

    The ocular vasculature and circulation play a crucial role in the development of several eye diseases including glaucoma [1], diabetic retinopathy [2], and exudative macular diseases [3]. Modalities that are capable of investigating the ocular vasculature and circulation are important for both understanding the mechanisms of the diseases and diagnosing these diseases.

  19. Palmitoylethanolamide: problems regarding micronization, ultra-micronization and additives.

    PubMed

    Kriek, Rutger

    2014-06-01

    It can be established that at least two of the writers of the article published in 'Inflammopharmacology', title: 'Palmitoylethanolamide (PEA), a naturally occurring disease-modifying agent in neuropathic pain' have a direct connection to the companies Epitech and Innovet. These companies produce micronized and ultra-micronized PEA. Therefore it is of eminent importance to determine whether the statements in this paper have also taken into consideration the European guidelines for Good Clinical Practice and the codes of good scientific practices. This is very questionable. A minimum condition in clinical studies for proving the claim that PEA in its micronized and ultra-micronized formulations works better than in its pure form or in other formulations is that a comparison be made between: PEA in pure form or in other formulations, on the one hand; PEA in the micronized and ultra-micronized formulations, on the other hand. This minimum condition is not complied with. Based on additional studies discussed in this commentary and in view of the effects of ultra-micronization on the parameters discussed, as well as the potential side-effects of additives such as excipients and herbal extracts added to the products cited in the article, the preference should be for the time being to treat patients with pure PEA without any of these additives.

  20. Doppler and range determination for deep space vehicles using active optical transponders

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.; Gagliardi, Robert M.

    1988-01-01

    This paper describes and analyzes two types of laser system employing active transponders that could accurately determine Doppler and range to deep space vehicles from earth-orbiting satellites. The first is a noncoherent optical system in which the Doppler effect on an intensity-modulating subcarrier is measured. The second is a coherent optical system in which the Doppler effect of the optical carrier itself is measured. Doppler and range measurement errors are mathematically modeled and, for three example systems, numerically evaluated.

  1. The Impact of Very High Frequency Surface Reverberation on Coherent Acoustic Propagation and Modeling

    DTIC Science & Technology

    2014-09-30

    range of wind-driven conditions. The model will focus on signal coherence, and second-order amplitude and Doppler statistics. The scattering of sound...which inject bubbles into the ocean. The amplitude, Doppler spread and temporal coherence of VHF scattering is important for the performance of high...There are two primary objectives. The first is to study the underlying relationship between the amplitude, Doppler and coherence of VHF acoustic

  2. Advances in High Energy Solid-State Pulsed 2-Micron Lidar Development for Ground and Airborne Wind, Water Vapor and CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Kavaya, Michael J.; Remus, Ruben

    2015-01-01

    NASA Langley Research Center has a long history of developing 2-micron lasers. From fundamental spectroscopy research, theoretical prediction of new materials, laser demonstration and engineering of lidar systems, it has been a very successful program spanning around two decades. Successful development of 2-micron lasers has led to development of a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement with an unprecedented laser pulse energy of 250 millijoules in a rugged package. This high pulse energy is produced by a Ho:Tm:LuLiF laser with an optical amplifier. While the lidar is meant for use as an airborne instrument, ground-based tests were carried out to characterize performance of the lidar. Atmospheric measurements will be presented, showing the lidar's capability for wind measurement in the atmospheric boundary layer and free troposphere. Lidar wind measurements are compared to a balloon sonde, showing good agreement between the two sensors. Similar architecture has been used to develop a high energy, Ho:Tm:YLF double-pulsed 2-micron Integrated Differential Absorption Lidar (IPDA) instrument based on direct detection technique that provides atmospheric column CO2 measurements. This instrument has been successfully used to measure atmospheric CO2 column density initially from a ground mobile lidar trailer, and then it was integrated on B-200 plane and 20 hours of flight measurement were made from an altitude ranging 1500 meters to 8000 meters. These measurements were compared to in-situ measurements and National Oceanic and Atmospheric Administration (NOAA) airborne flask measurement to derive the dry mixing ratio of the column CO2 by reflecting the signal by various reflecting surfaces such as land, vegetation, ocean surface, snow and sand. The lidar measurements when compared showed a very agreement with in-situ and airborne flask measurement. NASA Langley Research Center is currently developing a

  3. Solid-state coherent laser radar wind shear measuring systems

    NASA Technical Reports Server (NTRS)

    Huffaker, R. Milton

    1992-01-01

    Coherent Technologies, Inc. (CTI) was established in 1984 to engage in the development of coherent laser radar systems and subsystems with applications in atmospheric remote sensing, and in target tracking, ranging and imaging. CTI focuses its capabilities in three major areas: (1) theoretical performance and design of coherent laser radar system; (2) development of coherent laser radar systems for government agencies such as DoD and NASA; and (3) development of coherent laser radar systems for commercial markets. The topics addressed are: (1) 1.06 micron solid-state coherent laser radar system; (2) wind measurement using 1.06 micron system; and flashlamp-pumped 2.09 micron solid-state coherent laser radar system.

  4. DOPPLER WEATHER SYSTEM

    SciTech Connect

    Berlin, Gary J.

    2002-08-05

    The SRS Doppler Weather System consists of a Doppler Server, A Master Server (also known as the Weather Server), several Doppler Slave Servers, and client-side software program called the Doppler Radar Client. This system is used to display near rel-time images taken from the SRS Weather Center's Doppler Radar computer. The Doppler Server is software that resides on the SRS Doppler Computer. It gathers raw data, 24-bit color weather images via screen scraping ever five minutes as requested by the Master Server. The Doppler Server then reduces the 24-bit color images to 8-bit color using a fixed color table for analysis and compression. This preserves the fidelity of the image color and arranges the colors in specific order for display. At the time of color reduction, the white color used for the city names on the background images are remapped to a different index (color) of white that the white on the weather scale. The Weather Server places a time stamp on the image, then compresses the image and passes it to all Doppler Slave servers. Each of the Doppler Slave servers mainitain a circular buffer of the eight most current images representing the last 40 minutes of weather data. As a new image is added, the oldest drops off. The Doppler Radar Client is an optional install program for any site-wide workstation. When a Client session is started, the Client requests Doppler Slave server assignment from the Master Server. Upon its initial request to the Slave Server, the Client obtains all eight current images and maintains its own circular buffer, updating its images every five minutes as the Doppler Slave is updated. Three background reference images are stored as part of the Client. The Client brings up the appropriate background image, decompresses the doppler data, and displays the doppler data on the background image.

  5. Doppler Lidar Wind Value-Added Product

    SciTech Connect

    Newsom, R. K.; Sivaraman, C.; Shippert, T. R.; Riihimaki, L. D.

    2015-07-01

    Wind speed and direction, together with pressure, temperature, and relative humidity, are the most fundamental atmospheric state parameters. Accurate measurement of these parameters is crucial for numerical weather prediction. Vertically resolved wind measurements in the atmospheric boundary layer are particularly important for modeling pollutant and aerosol transport. Raw data from a scanning coherent Doppler lidar system can be processed to generate accurate height-resolved measurements of wind speed and direction in the atmospheric boundary layer.

  6. Christian Doppler and the Doppler effect

    NASA Astrophysics Data System (ADS)

    Toman, Kurt

    1984-04-01

    A summary is given of Doppler's life and career. He was born 180 years ago on November 29, 1803, in Salzburg, Austria. He died on March 17, 1853 in Venice. The effect bearing his name was first announced in a presentation before the Royal Bohemian Society of the Sciences in Prague on May 25, 1842. Doppler considered his work a generalization of the aberration theorem as discovered by Bradley. With it came the inference that the perception of physical phenomena can change with the state of motion of the observer. Acceptance of the principle was not without controversy. In 1852, the mathematician Petzval claimed that no useful scientific deductions can be made from Doppler's elementary equations. In 1860, Ernst Mach resolved the misunderstanding that clouded this controversy. The Doppler effect is alive and well. Its role in radio science and related disciplines is enumerated.

  7. Direct femtosecond laser writing system for sub-micron and micron scale patterning

    NASA Astrophysics Data System (ADS)

    Vanagas, Egidijus; Tuzhilin, Dmitry; Zinkou, Michail; Sedunov, Alexander; Vasiliev, Nikolai; Kudryashov, Igor; Kononov, Vladimir; Suruga, Shozi

    2003-11-01

    Commercial femtosecond micromachining system (FMS) has been developed that capable to process the material in sub-micron (< 200 nm) and micron scale. Core of the system are: optical unit, controller unit and software. The other parts: fs-laser system; focusing unit; stage unit can be varied (exchangeable). Two different fs-laser systems already are compatible with core of FMS: Mira/RegA (Coherent) and Hurricane (Spectra-Physics). FMS controller unit allows to control every single fs-pulse delivery on the target. Three possible types of focusing unit are available: microscope type unit, long focal distance lens unit, and axicon lens based unit. Standard stage unit options are: three-axis piezostage, and two-axis air bearing stage combined with Z-axis piezostage. Repeatability for all dimensions is within +/-5 nm. Also, step motor stages are available. The system allows 3D scan with confocal laser-microscope (resolution δr=200nm, δz=540nm) build in optical unit. Software controls all basic functions of the system performance and writing any pattern (including 3D) on or into specimen. The results obtained by direct fs-laser writing method are presented and discussed: bits in the range of 100 - 200 nm sizes, 6 TB/cm3 density optical storage matrix, waveguides fabrication inside transparent materials, high aspect ratio (1:125) patterning of dielectric materials with Gauss-Bessel beam.

  8. Doppler flowmetry in preeclampsia.

    PubMed

    Zahumensky, J

    2009-01-01

    The purpose of this study was to summarize the new published data on the Doppler flowmetry in preeclampsia. We summarize the new published data on the Doppler flowmetry in uteroplacental, fetoplacental and fetal circulation in preeclampsia. The present review summarized the results of clinical research on the Doppler flowmetry in the screening of risk of preclampsia, in the diagnosis of preclampsia and in the fetal risk in preclampsia (Ref. 19). Full Text (Free, PDF) www.bmj.sk.

  9. Advanced Doppler tracking experiments

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.

    1989-01-01

    The Doppler tracking method is currently the only technique available for broadband gravitational wave searches in the approx. 10(exp -4) to 10(exp -1) Hz low frequency band. A brief review is given of the Doppler method, a discussion of the main noise sources, and a review of experience with current spacecraft and the prospects for sensitivity improvements in an advanced Doppler tracking experiment.

  10. The Selection of Q-Switch for a 350mJ Air-borne 2-micron Wind Lidar

    NASA Technical Reports Server (NTRS)

    Petros, Mulugeta; Yu, Jirong; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Singh, Upendra N.

    2008-01-01

    In the process of designing a coherent, high energy 2micron, Doppler wind Lidar, various types of Q-Switch materials and configurations have been investigated for the oscillator. Designing an oscillator with a relatively low gain laser material, presents challenges related to the management high internal circulating fluence due to high reflective output coupler. This problem is compounded by the loss of hold-off. In addition, the selection has to take into account the round trip optical loss in the resonator and the loss of hold-off. For this application, a Brewster cut 5mm aperture, fused silica AO Q-switch is selected. Once the Q-switch is selected various rf frequencies were evaluated. Since the Lidar has to perform in single longitudinal and transverse mode with transform limited line width, in this paper, various seeding configurations are presented in the context of Q-Switch diffraction efficiency. The master oscillator power amplifier has demonstrated over 350mJ output when the amplifier is operated in double pass mode and higher than 250mJ when operated in single pass configuration. The repetition rate of the system is 10Hz and the pulse length 200ns.

  11. Micronized-Coal Burner Facility

    NASA Technical Reports Server (NTRS)

    Calfo, F. D.; Lupton, M. W.

    1986-01-01

    Micronized-coal (coal-in-oil mix) burner facility developed to fulfill need to generate erosion/corrosion data on series of superalloy specimens. In order to successfully operate gas turbine using COM, two primary conditions must be met. First, there must be adequate atomization of COM and second, minimization of coking of burner. Meeting these conditions will be achieved only by clean burning and flame stability.

  12. Fiber-Based Doppler Lidar for Vector Velocity and Altitude Measurements

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Pierrottet, Diego; Hines, Glenn; Petway, Larry; Barnes, Bruce

    2015-01-01

    A coherent Doppler lidar capable of providing accurate velocity and altitude data has been developed and demonstrated for future NASA missions to the solar system bodies requiring precision navigation and controlled soft landing.

  13. High Energy 2-micron Laser Developments

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Trieu, Bo C.; Petros, Mulugeta; Bai, Yingxin; Petzar, Paul J.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.

    2007-01-01

    This viewgraph presentation shows the development of 2-micron solid state lasers. The topics covered include: 1) Overview 2-micron solid state lasers; 2) Modeling and population inversion measurement; 3) Side pump oscillator; and 4) One Joule 2-m Laser.

  14. Miniature Laser Doppler Velocimeter for Measuring Wall Shear

    NASA Technical Reports Server (NTRS)

    Gharib, Morteza; Modarress, Darius; Forouhar, Siamak; Fourguette, Dominique; Taugwalder, Federic; Wilson, Daniel

    2005-01-01

    A miniature optoelectronic instrument has been invented as a nonintrusive means of measuring a velocity gradient proportional to a shear stress in a flow near a wall. The instrument, which can be mounted flush with the wall, is a variant of a basic laser Doppler velocimeter. The laser Doppler probe volume can be located close enough to the wall (as little as 100 micron from the surface) to lie within the viscosity-dominated sublayer of a turbulent boundary layer. The instrument includes a diode laser, the output of which is shaped by a diffractive optical element (DOE) into two beams that have elliptical cross sections with very high aspect ratios.

  15. The Cognitive Doppler.

    ERIC Educational Resources Information Center

    Kozoil, Micah E.

    1989-01-01

    Discusses the learning needs of students in the concrete operational stage in mathematics. Identifies the phenomenon of reduced cognitive performance in an out-of-class environment as the "Cognitive Doppler." Suggests methods of reducing the pronounced effects of the Cognitive Doppler by capitalizing on the students' ability to memorize…

  16. Doppler ultrasound monitoring technology.

    PubMed

    Docker, M F

    1993-03-01

    Developments in the signal processing of Doppler ultrasound used for the detection of fetal heart rate (FHR) have improved the operation of cardiotocographs. These developments are reviewed and the advantages and disadvantages of the various Doppler and signal processing methods are compared.

  17. The Cognitive Doppler.

    ERIC Educational Resources Information Center

    Kozoil, Micah E.

    1989-01-01

    Discusses the learning needs of students in the concrete operational stage in mathematics. Identifies the phenomenon of reduced cognitive performance in an out-of-class environment as the "Cognitive Doppler." Suggests methods of reducing the pronounced effects of the Cognitive Doppler by capitalizing on the students' ability to memorize…

  18. Sizing fine particles with the phase Doppler interferometric technique

    NASA Astrophysics Data System (ADS)

    Sankar, S. V.; Weber, B. J.; Kamemoto, D. Y.; Bachalo, W. D.

    1991-11-01

    A systematic theoretical and experimental study was carried out to investigate the response characteristics of a phase Doppler particle analyzer (PDPA). The theoretical analysis used a model based on the Lorenz-Mie theory; in the experiments the PDPA was used to size fine polystyrene latex particles dispersed in water and in air. The experimental and theoretical results demonstrate that the magnitude of oscillations in the phase vs size calibration curves of the PDPA can be decreased by a proper choice of the optical configuration. Sizing of small particles (less than 10 microns) with a resolution of +/-0.3 to +/-0.4 micron is shown to be possible.

  19. Joint Agency Doppler Technology Tests.

    DTIC Science & Technology

    DOPPLER RADAR, *METEOROLOGICAL RADAR, *EARLY WARNING SYSTEMS, DAMAGE, HAZARDS, NETWORKS, REAL TIME, RADAR, IDENTIFICATION, RELIABILITY, HAIL, AIR FORCE FACILITIES, DOPPLER SYSTEMS, AIRPORTS, WARNING SYSTEMS, TORNADOES .

  20. Double-Pulsed 2-micron Laser Transmitter for Multiple Lidar Applications

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong

    2002-01-01

    A high energy double-pulsed Ho:Tm:YLF 2-micron laser amplifier has been demonstrated. 600 mJ per pulse pair under Q-switch operation is achieved with the gain of 4.4. This solid-state laser source can be used as lidar transmitter for multiple lidar applications such as coherent wind and carbon dioxide measurements.

  1. High-Energy 2-Micrometers Doppler Lidar for Wind Measurements

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Beyon, Jeffrey Y.; Barnes, Bruce W.; Petros, Mulugeta; Yu, Jirong; Amzajerdian, Farzin; Kavaya, Michael J.; Singh, Upendra N.

    2006-01-01

    High-energy 2-micrometer wavelength lasers have been incorporated in a prototype coherent Doppler lidar to test component technologies and explore applications for remote sensing of the atmosphere. Design of the lidar is presented including aspects in the laser transmitter, receiver, photodetector, and signal processing. Calibration tests and sample atmospheric data are presented on wind and aerosol profiling.

  2. 2.5 MHz Line-Width High-energy, 2 Micrometer Coherent Wind Lidar Transmitter

    NASA Technical Reports Server (NTRS)

    Petros, Mulugeta; Yu, Jirong; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Singh, Upendra N.; Reithmaier, Karl

    2007-01-01

    2 micron solid-state lasers are the primary choice for coherent Doppler wind detection. As wind lidars, they are used for wake vortex and clear air turbulence detection providing air transport safety. In addition, 2 micron lasers are one of the candidates for CO2 detection lidars. The rich CO2 absorption line around 2 micron, combined with the long upper state life of time, has made Ho based 2 micron lasers a viable candidate for CO2 sensing DIAL instrument. The design and fabrication of a compact coherent laser radar transmitter for Troposphere wind sensing is under way. This system is hardened for ground as well as airborne applications. As a transmitter for a coherent wind lidar, this laser has stringent spectral line width and beam quality requirements. Although the absolute wavelength does not have to be fixed for wind detection, to maximize return signal, the output wavelength should avoid atmospheric CO2 and H2O absorption lines. The base line laser material is Ho:Tm:LuLF which is an isomorph of Ho:Tm:YLF. LuLF produces 20% more output power than Ho:Tm:YLF. In these materials the Tm absorption cross-section, the Ho emission cross-section, the Tm to Ho energy transfer parameters and the Ho (sup 5) I (sub 7) radiative life time are all identical. However, the improved performance of the LuLF is attributed to the lower thermal population in the (sup 5) I (sub 8) manifold. It also provides higher normal mode to Q-switch conversion than YLF at high pump energy indicating a lower up-conversion. The laser architecture is composed of a seed laser, a ring oscillator, and a double pass amplifier. The seed laser is a single longitudinal mode with a line width of 13 KHz. The 100mJ class oscillator is stretched to 3 meters to accommodate the line-width requirement without compromising the range resolution of the instrument. The amplifier is double passed to produce greater than 300mJ energy.

  3. Doppler radar flowmeter

    DOEpatents

    Petlevich, Walter J.; Sverdrup, Edward F.

    1978-01-01

    A Doppler radar flowmeter comprises a transceiver which produces an audio frequency output related to the Doppler shift in frequency between radio waves backscattered from particulate matter carried in a fluid and the radiated radio waves. A variable gain amplifier and low pass filter are provided for amplifying and filtering the transceiver output. A frequency counter having a variable triggering level is also provided to determine the magnitude of the Doppler shift. A calibration method is disclosed wherein the amplifier gain and frequency counter trigger level are adjusted to achieve plateaus in the output of the frequency counter and thereby allow calibration without the necessity of being able to visually observe the flow.

  4. Office based multi-functional anterior eye segment optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lim, Yiheng; Yamanari, Masahiro; Hong, Young-Joo; Makita, Shuichi; Miura, Masahiro; Yasuno, Yoshiaki

    2012-03-01

    An office based Doppler and polarization sensitive swept-source optical coherence tomography (Doppler-PS-SS-OCT) was developed for diagnosis and evaluation of abnormalities of anterior eye segment in clinic. A healthy eye was measured in vivo by the Doppler PS-OCT. The results showed that the Doppler PS-OCT may have potential to identify blood vessels and discriminate fibrous tissues in abnormalities, such as scarring in bleb, and scleral inflammation.

  5. Doppler Lidar (DL) Handbook

    SciTech Connect

    Newsom, RK

    2012-02-13

    The Doppler lidar (DL) is an active remote sensing instrument that provides range- and time-resolved measurements of radial velocity and attenuated backscatter. The principle of operation is similar to radar in that pulses of energy are transmitted into the atmosphere; the energy scattered back to the transceiver is collected and measured as a time-resolved signal. From the time delay between each outgoing transmitted pulse and the backscattered signal, the distance to the scatterer is inferred. The radial or line-of-sight velocity of the scatterers is determined from the Doppler frequency shift of the backscattered radiation. The DL uses a heterodyne detection technique in which the return signal is mixed with a reference laser beam (i.e., local oscillator) of known frequency. An onboard signal processing computer then determines the Doppler frequency shift from the spectra of the heterodyne signal. The energy content of the Doppler spectra can also be used to determine attenuated backscatter.

  6. Analysis of Sub-Grid Boundary-Layer Processes Observed by the P-3 Doppler Wind Lidar in Support of the Western Pacific Tropical Cyclone Structure 2008 Experiment

    DTIC Science & Technology

    2012-02-02

    flight hours to one significant atmospheric phenomena. OBJECTIVES The P-3 Doppler Wind Lidar (P3DWL) uses the latest version of a coherent ... Doppler transceiver developed at Lockheed Martin Coherent Technologies. The lidar , with the exception of the scanner, is shown on the top in Figure 1...Processes Observed by the P-3 Doppler Wind Lidar in Support of the Western Pacific Tropical Cyclone Structure 2008 Experiment Ralph Foster Applied

  7. Pulse subtraction Doppler

    NASA Astrophysics Data System (ADS)

    Mahue, Veronique; Mari, Jean Martial; Eckersley, Robert J.; Caro, Colin G.; Tang, Meng-Xing

    2010-01-01

    Recent advances have demonstrated the feasibility of molecular imaging using targeted microbubbles and ultrasound. One technical challenge is to selectively detect attached bubbles from those freely flowing bubbles and surrounding tissue. Pulse Inversion Doppler is an imaging technique enabling the selective detection of both static and moving ultrasound contrast agents: linear scatterers generate a single band Doppler spectrum, while non-linear scatterers generate a double band spectrum, one being uniquely correlated with the presence of contrast agents and non-linear tissue signals. We demonstrate that similar spectrums, and thus the same discrimination, can be obtained through a Doppler implementation of Pulse Subtraction. This is achieved by reconstructing a virtual echo using the echo generated from a short pulse transmission. Moreover by subtracting from this virtual echo the one generated from a longer pulse transmission, it is possible to fully suppress the echo from linear scatterers, while for non-linear scatterers, a signal will remain, allowing classical agent detection. Simulations of a single moving microbubble and a moving linear scatterer subject to these pulses show that when the virtual echo and the long pulse echo are used to perform pulsed Doppler, the power Doppler spectrum allows separation of linear and non-linear moving scattering. Similar results are obtained on experimental data acquired on a flow containing either microbubble contrast agents or linear blood mimicking fluid. This new Doppler method constitutes an alternative to Pulse Inversion Doppler and preliminary results suggest that similar dual band spectrums could be obtained by the combination of any non-linear detection technique with Doppler demodulation.

  8. Using an Airborne Doppler Lidar to Evaluate QuikSCAT and RadarSat Derived Winds

    NASA Astrophysics Data System (ADS)

    Emmitt, G. D.; O'Handley, C.; Brown, R. A.; Foster, R.

    2002-12-01

    While near surface winds derived from space-based remote sensing have proven very useful, both operationally and for research, there remain several issues not fully resolved. Besides the persistent wind direction uncertainty, high wind speeds (> 25 m/s) and organized circulations such as those associated with large marine atmospheric boundary layer eddies continue to introduce magnitude and representativeness errors in the data products. The US Navy and the Integrated Program Office of NPOESS have jointly sponsored the installation and use of a scanning Doppler wind lidar on a Navy Twin Otter aircraft. The lidar is a 2 micron coherent system with a side door mounted hemispherical scanner. Returns from aerosols are processed to obtain wind profiles (above and below flight level). The measurement accuracy is on the order of a few cm/sec in speed and a degree or two in direction. The footprint of the lidar beam is < 1 meter and the full profiles are constructed with wind observations over a one l kilometer flight segment. The vertical resolution is usually < 50 meters. In the nadir looking mode, the Doppler lidar can resolve wave structures with < 5 cm/sec vertical motion accuracy and with .5 meter horizontal resolution. In the Spring of 2002, the lidar was flown over Monterey Bay (CA)during QuikSCAT and RadarSat overpasses. Cloud streets were observed from the aircraft and with the lidar in the vicinity of organized patterns in the RadarSAT returns. The lidar data offer detailed insight into the velocity and aerosol structures within the larger footprints of the space-based sensors. Detailed analyses of the collocated lidar, QuikScat and RadarSat data will be presented along with plans for the future use of this new research facility.

  9. Clinical Applications of Doppler OCT and OCT Angiography

    NASA Astrophysics Data System (ADS)

    Tan, Ou; Jia, Yali; Wei, Eric; Huang, David

    Doppler optical coherence tomography (OCT) is a functional extension of OCT that allows for the visualization and measurement of blood flow [1, 2]. Phase-resolved Doppler OCT has become a standard algorithm for measuring Doppler shift with Fourier-domain (FD)-OCT because of its high velocity sensitivity [3]. In ophthalmology, several methods have been developed to measure in vivo retinal blood flow using this algorithm. Since Doppler OCT measures only the velocity component parallel to the OCT probe beam, additional information is needed to calculate absolute velocity and volumetric flow rate. One method is to employ two OCT beams with a fixed offset in incidence angles [4, 5]. However, this approach requires special hardware and is not compatible with commercial single-beam OCT systems. Another approach is to use special scan patterns to measure the Doppler angle (angle between the OCT beam and the blood vessel). Some groups used concentric scan patterns [6, 7], while other groups used raster scan patterns [8, 9]. Finally, Srinivasan et al. developed en face Doppler OCT for cerebral blood flow calculation, which obviated the need for Doppler angle estimation [10]. Bauman et al. adapted the method for total retinal blood flow (TRBF) calculation with ultrafast swept-source OCT [11]. In this chapter, we focus our attention on the double-circular scan pattern developed in our research group, which has been used in a number of clinical studies for preliminary demonstration of utility.

  10. SPAce Readiness Coherent Lidar Experiment: validation of observing system simulations

    NASA Astrophysics Data System (ADS)

    Emmitt, George D.; Miller, Timothy; Kavaya, Michael J.

    1998-12-01

    NASA recently approved a mission to fly a Doppler Wind Lidar on a US Space Shuttle. SPARCLE, managed by Marshall Space Flight Center in Huntsville, AL, is targeted for launch in March 2001. This mission is viewed as a necessary demonstration of a solid state lidar using coherent detection before committing resources to a 3-5 year research or operational mission. While, to many, this shuttle mission is seen as the first step in a series leading to a fully operational wind observing system, to others, it is a chance to validate predictions of performance based upon theoretical models, analyses of airborne and ground-based data and sophisticated observing system simulation experiments. The SPARCLE instrument is a 100 mJ, 6 Hz, diode pumped 2 micron laser with a .25 m telescope using heterodyne mixing in a fiber and an InGaAs detector. A 25 cm silicon wedge scanner will be used in step-stare modes with dwells ranging from 60 seconds to .5 seconds. Pointing knowledge is achieved with a dedicated GPS/INS mounted close to the lidar. NASA's hitchhiker program is providing the instrument enclosures and mission logistics support. An on- board data system in sized to record 80 Gbytes of raw signal from two 400 MHz A/D converters. On-board signal processing will be used to control the frequency of the Master Oscillator. SPARCLE is predicted to have a singleshot backscatter sensitivity near 5 by 10-6 m-1 sr-1. To achieve higher sensitivity, shot accumulation will be employed. Ground-based, 2 micron DWLs have been used to assess the benefits of shot accumulation. Airborne programs like MACAWS have provided good data st for evaluating various sampling strategies and signal processing algorithms. Using these real data to calibrate out simulation models, we can describe when and how well SPARCLE is expected to perform.

  11. Analysis of Optimum Heterodyne Receivers for Coherent Lidar Applications

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin

    2002-01-01

    A full analysis of the combined effects of all the noise sources of optical heterodyne receiver and the interaction between the competing control parameters of the receiver detector and pre-amplifier will be presented. This analysis provides the mean for true optimization of the coherent lidar receiver. The significance of the optimization of heterodyne receiver is shown for 2-micron coherent lidar.

  12. Analysis of Space Coherent LIDAR Wind Mission

    NASA Technical Reports Server (NTRS)

    Spiers, Gary D.

    1997-01-01

    An evaluation of the performance of a coherent Doppler lidar proposed by a team comprising the NASA Marshall Space Flight Center, Lockheed Martin Space Company, University of Wisconsin and Los Alamos National Laboratory to NASA's Earth System Science Pathfinder (ESSP) program was performed. The design went through several iterations and only the performance of the final design is summarized here.

  13. Two target height effects on interferometric synthetic aperture radar coherence

    SciTech Connect

    YOCKY,DAVID A.; JAKOWATZ JR.,CHARLES V.

    2000-03-07

    Useful products generated from interferometric synthetic aperture radar (IFSAR) complex data include height measurement, coherent change detection, and classification. The IFSAR coherence is a spatial measure of complex correlation between two collects, a product of IFSAR signal processing. A tacit assumption in such IFSAR signal processing is that one height target exists in each range-Doppler cell. This paper presents simulations of IFSAR coherence if two targets with different heights exist in a given range-Doppler cell, a condition in IFSAR collections produced by layover. It also includes airborne IFSAR data confirming the simulation results. The paper concludes by exploring the implications of the results on IFSAR classification and height measurements.

  14. Lidar and Mission Parameter Trade Study of Space-Based Coherent Wind Measurement Centered on NASA's 2006 GWOS Wind Mission Study Parameters

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Frehlich, Rod G.

    2007-01-01

    The global measurement of vertical profiles of horizontal vector winds has been highly desired for many years by NASA, NOAA and the Integrated Program Office (IPO) implementing the National Polar-orbiting Operational Environmental Satellite Systems (NPOESS). Recently the global wind mission was one of 15 missions recommended to NASA by the first ever NRC Earth Sciences Decadal Survey. Since before 1978, the most promising method to make this space-based measurement has been pulsed Doppler lidar. The favored technology and technique has evolved over the years from obtaining line-of-sight (LOS) wind profiles from a single laser shot using pulsed CO2 gas laser technology to the current plans to use both a coherent-detection and direct-detection pulsed Doppler wind lidar systems with each lidar employing multiple shot accumulation to produce an LOS wind profile. The idea of using two lidars (hybrid concept) entails coherent detection using the NASA LaRC-developed pulsed 2-micron solid state laser technology, and direct detection using pulsed Nd:YAG laser technology tripled in frequency to 355 nm wavelength.

  15. Statistical parametric mapping of stimuli-evoked changes in quantitative blood flow using extended-focus optical coherence microscopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Marchand, Paul J.; Bouwens, Arno; Shamaei, Vincent; Nguyen, David; Extermann, Jerome; Bolmont, Tristan; Lasser, Theo

    2016-03-01

    Magnetic Resonance Imaging has revolutionised our understanding of brain function through its ability to image human cerebral structures non-invasively over the entire brain. By exploiting the different magnetic properties of oxygenated and deoxygenated blood, functional MRI can indirectly map areas undergoing neural activation. Alongside the development of fMRI, powerful statistical tools have been developed in an effort to shed light on the neural pathways involved in processing of sensory and cognitive information. In spite of the major improvements made in fMRI technology, the obtained spatial resolution of hundreds of microns prevents MRI in resolving and monitoring processes occurring at the cellular level. In this regard, Optical Coherence Microscopy is an ideal instrumentation as it can image at high spatio-temporal resolution. Moreover, by measuring the mean and the width of the Doppler spectra of light scattered by moving particles, OCM allows extracting the axial and lateral velocity components of red blood cells. The ability to assess quantitatively total blood velocity, as opposed to classical axial velocity Doppler OCM, is of paramount importance in brain imaging as a large proportion of cortical vascular is oriented perpendicularly to the optical axis. We combine here quantitative blood flow imaging with extended-focus Optical Coherence Microscopy and Statistical Parametric Mapping tools to generate maps of stimuli-evoked cortical hemodynamics at the capillary level.

  16. Effects of non-spherical drops on a phase Doppler spray analyzer

    NASA Technical Reports Server (NTRS)

    Alexander, D. R.; Wiles, K. J.; Schaub, S. A.; Seeman, M. P.

    1985-01-01

    A phase/Doppler spray analyzer (P/DSA) and a laser imaging system was used to study the response of a P/DSA to nonspherical particles. Methanol particles with an aspect ratio ranging from 0.7 to 1.4 were used in this investigation. Results indicated that the P/DSA was quite sensitive to particle shape. A Berglund-Liu generator was used to produce particles of 98 microns (volumetric diameter). The P/DSA instrument measured particle sizes ranging from 142 microns for a particle of aspect ratio 0.7, to 84 microns for an aspect ratio of 1.4. Particle diameters based on averaged x and y diameters for the laser imaging system ranged from 95 microns to 92 microns over the same range of aspect ratios.

  17. One Micron Laser Technology Advancements at GSFC

    NASA Technical Reports Server (NTRS)

    Heaps, William S.

    2010-01-01

    This slide presentation reviews the advancements made in one micron laser technology at Goddard Space Flight Center. It includes information about risk factors that are being addressed by GSFC, and overviews of the various programs that GSFC is currently managing that are using 1 micron laser technology.

  18. High Energy 2-Micron Laser Developments

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Trieu, Bo C.; Petros, Mulugeta; Bai, Yingxin; Petzar, Paul J.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.

    2007-01-01

    A master oscillator power amplifier, high energy Q-switched 2-micron laser system has been recently demonstrated. The laser and amplifiers are all designed in side-pumped rod configuration, pumped by back-cooled conductive packaged GaAlAs diode laser arrays. This 2-micron laser system provides nearly transform limited beam quality.

  19. Imaging doppler lidar for wind turbine wake profiling

    DOEpatents

    Bossert, David J.

    2015-11-19

    An imaging Doppler lidar (IDL) enables the measurement of the velocity distribution of a large volume, in parallel, and at high spatial resolution in the wake of a wind turbine. Because the IDL is non-scanning, it can be orders of magnitude faster than conventional coherent lidar approaches. Scattering can be obtained from naturally occurring aerosol particles. Furthermore, the wind velocity can be measured directly from Doppler shifts of the laser light, so the measurement can be accomplished at large standoff and at wide fields-of-view.

  20. Penile Doppler ultrasonography revisited.

    PubMed

    Jung, Dae Chul; Park, Sung Yoon; Lee, Joo Yong

    2017-06-10

    Penile Doppler ultrasonography is a high-performing, noninvasive or minimally-invasive imaging modality that allows the depiction of the normal anatomy and macroscopic pathologic changes in real time. Moreover, functional changes in penile blood flow, as seen in erectile dysfunction (ED), can be analyzed using color Doppler ultrasonography (CDUS). This review article describes the normal sonographic anatomy of the penis, the sonographic technique for evaluating ED, the normal phases of erection, and the various causes of ED. Additionally, we describe the interpretation of different parameters and findings on penile CDUS for the diagnosis and classification of ED, priapism, and Peyronie disease.

  1. Doppler ion program description

    SciTech Connect

    Henline, P.

    1980-12-01

    The Doppler spectrometer is a conventional Czerny-Turner grating spectrometer with a 1024 channel multiple detector. Light is dispersed across the detector, and its output yields a spectrum covering approximately 200 A. The width of the spectral peak is directly proportional to the temperature of the emitting ions, and determination of the impurity ion temperature allows one to infer the plasma ion temperature. The Doppler ion software system developed at General Atomic uses a TRACOR Northern 1710-31 and an LSI-11/2. The exact configuration of Doublet III is different from TRACOR Northern systems at other facilities.

  2. Phase Doppler anemometry as an ejecta diagnostic

    NASA Astrophysics Data System (ADS)

    Bell, D. J.; Chapman, D. J.

    2017-01-01

    When a shock wave is incident on a free surface, micron sized pieces of the material can be ejected from that surface. Phase Doppler Anemometry (PDA) is being developed to simultaneously measure the sizes and velocities of the individual shock induced ejecta particles; providing an important insight into ejecta phenomena. The results from experiments performed on the 13 mm bore light gas gun at the Institute of Shock Physics, Imperial College London are presented. Specially grooved tin targets were shocked at pressures of up to 14 GPa, below the melt on release pressure, to generate ejecta particles. These experiments are the first time that PDA has been successfully fielded on dynamic ejecta experiments. The results and current state of the art of the technique are discussed along with the future improvements required to optimise performance and increase usability.

  3. Laser Doppler measurement techniques for spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.; Gagliardi, Robert M.

    1986-01-01

    Two techniques are proposed for using laser links to measure the relative radial velocity of two spacecraft. The first technique determines the relative radial velocity from a measurement of the two-way Doppler shift on a transponded radio-frequency subcarrier. The subcarrier intensity-modulates reciprocating laser beams. The second technique determines the relative radial velocity from a measurement of the two-way Doppler shift on an optical frequency carrier which is transponded between spacecraft using optical Costas loops. The first technique might be used in conjunction with noncoherent optical communications, while the second technique is compatible with coherent optical communications. The first technique simultaneously exploits the diffraction advantage of laser beams and the maturity of radio-frequency phase-locked loop technology. The second technique exploits both the diffraction advantage of laser beams and the large Doppler effect at optical frequencies. The second technique has the potential for greater accuracy; unfortunately, it is more difficult to implement since it involves optical Costas loops.

  4. Method for sampling sub-micron particles

    DOEpatents

    Gay, Don D.; McMillan, William G.

    1985-01-01

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

  5. Sub-micron particle sampler apparatus

    DOEpatents

    Gay, Don D.; McMillan, William G.

    1987-01-01

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

  6. The Doppler Pendulum Experiment

    ERIC Educational Resources Information Center

    Lee, C. K.; Wong, H. K.

    2011-01-01

    An experiment to verify the Doppler effect of sound waves is described. An ultrasonic source is mounted at the end of a simple pendulum. As the pendulum swings, the rapid change of frequency can be recorded by a stationary receiver using a simple frequency-to-voltage converter. The experimental results are in close agreement with the Doppler…

  7. The Doppler Pendulum Experiment

    ERIC Educational Resources Information Center

    Lee, C. K.; Wong, H. K.

    2011-01-01

    An experiment to verify the Doppler effect of sound waves is described. An ultrasonic source is mounted at the end of a simple pendulum. As the pendulum swings, the rapid change of frequency can be recorded by a stationary receiver using a simple frequency-to-voltage converter. The experimental results are in close agreement with the Doppler…

  8. Photonic doppler velocimetry

    SciTech Connect

    Lowry, M E; Molau, N E; Sargis, P D; Strand, O T; Sweider, D

    1999-01-01

    We are developing a novel fiber-optic approach to laser Doppler velocimetry as a diagnostic for high explosives tests. Using hardware that was originally developed for the telecommunications industry, we are able to measure surface velocities ranging from centimeters per second to kilometers per second. Laboratory measurements and field trials have shown excellent agreement with other diagnostics.

  9. Finnish Meteorological Institute Doppler Lidar

    SciTech Connect

    Ewan OConnor

    2015-03-27

    This doppler lidar system provides co-polar and cross polar attenuated backscatter coefficients,signal strength, and doppler velocities in the cloud and in the boundary level, including uncertainties for all parameters. Using the doppler beam swinging DBS technique, and Vertical Azimuthal Display (VAD) this system also provides vertical profiles of horizontal winds.

  10. Ultrasonic colour Doppler imaging

    PubMed Central

    Evans, David H.; Jensen, Jørgen Arendt; Nielsen, Michael Bachmann

    2011-01-01

    Ultrasonic colour Doppler is an imaging technique that combines anatomical information derived using ultrasonic pulse-echo techniques with velocity information derived using ultrasonic Doppler techniques to generate colour-coded maps of tissue velocity superimposed on grey-scale images of tissue anatomy. The most common use of the technique is to image the movement of blood through the heart, arteries and veins, but it may also be used to image the motion of solid tissues such as the heart walls. Colour Doppler imaging is now provided on almost all commercial ultrasound machines, and has been found to be of great value in assessing blood flow in many clinical conditions. Although the method for obtaining the velocity information is in many ways similar to the method for obtaining the anatomical information, it is technically more demanding for a number of reasons. It also has a number of weaknesses, perhaps the greatest being that in conventional systems, the velocities measured and thus displayed are the components of the flow velocity directly towards or away from the transducer, while ideally the method would give information about the magnitude and direction of the three-dimensional flow vectors. This review briefly introduces the principles behind colour Doppler imaging and describes some clinical applications. It then describes the basic components of conventional colour Doppler systems and the methods used to derive velocity information from the ultrasound signal. Next, a number of new techniques that seek to overcome the vector problem mentioned above are described. Finally, some examples of vector velocity images are presented. PMID:22866227

  11. Coherent detectors

    NASA Astrophysics Data System (ADS)

    Lawrence, C. R.; Church, S.; Gaier, T.; Lai, R.; Ruf, C.; Wollack, E.

    2009-03-01

    Coherent systems offer significant advantages in simplicity, testability, control of systematics, and cost. Although quantum noise sets the fundamental limit to their performance at high frequencies, recent breakthroughs suggest that near-quantum-limited noise up to 150 or even 200 GHz could be realized within a few years. If the demands of component separation can be met with frequencies below 200 GHz, coherent systems will be strong competitors for a space CMB polarization mission. The rapid development of digital correlator capability now makes space interferometers with many hundreds of elements possible. Given the advantages of coherent interferometers in suppressing systematic effects, such systems deserve serious study.

  12. Doppler effect in optical velocimetry

    NASA Astrophysics Data System (ADS)

    Rinkevichius, Bronius S.

    1996-02-01

    The current state of the optical metrology based on the Doppler effect has been reviewed. Some historical and scientific information is given, in addition the contemporary optical methods of the velocity measurement using the Doppler effect are analyzed. The Doppler effect applications in astrophysics, plasma physics, investigations of gas and liquid flows, acoustics, mechanics of the deforming solid body and of the rotational motion are considered. The description is presented for the following techniques of the velocity measurement: laser Doppler anemometry, laser Doppler vibrometry, laser gyroscopy.

  13. Tunable diode laser heterodyne spectrometer for remote observations near 8 microns

    NASA Technical Reports Server (NTRS)

    Glenar, D. A.; Kostiuk, T.; Jennings, D. E.; Buhl, D.; Mumma, M. J.

    1982-01-01

    Infrared heterodyne spectroscopy is a passive technique employing coherent optical detection for the study of spectral features in remote sources. It employs optical components such as mirrors and lenses normally associated with incoherent optics, but because of it's coherent nature, it offers the advantages of ultrahigh spectral resolving power, high frequency precision, and diffraction limited field-of-view. Attention is given to the development of an ultrahigh resolution diode laser heterodyne spectrometer for observational and laboratory use. The instrument is designed for operation in the spectral range from 7.5 to 8.5 microns. A PbSe tuneable diode laser (TDL) is employed as local oscillator. A closed-cycle cooler is employed to keep the oscillator at operating temperatures in the range from 12 to 60 K. Attention is given to factors determining the TDL heterodyne sensitivity, the spectrometer design, and a survey of 8 micron observations, SiO could be detected in the sunspot spectrum.

  14. All semiconductor laser Doppler anemometer at 1.55 microm.

    PubMed

    Hansen, René Skov; Pedersen, Christian

    2008-10-27

    We report to our best knowledge the first all semiconductor Laser Doppler Anemometer (LIDAR) for wind speed determination. We will present the design and first experimental results on a focusing coherent cw laser Doppler anemometer for measuring atmospheric wind velocities in the 10 meters to 300 meters distance range. Especially, we will demonstrate that both the output power as well as the demanding coherence properties required from the laser source can be accomplished by an all semiconductor laser. Preliminary tests at a distance of 40 meters indicate a typical signal to noise ratio of 9 dB. This result is obtained at a clear day with an up-date rate of 12 Hz.

  15. Progress in coherent laser radar

    NASA Technical Reports Server (NTRS)

    Vaughan, J. M.

    1986-01-01

    Considerable progress with coherent laser radar has been made over the last few years, most notably perhaps in the available range of high performance devices and components and the confidence with which systems may now be taken into the field for prolonged periods of operation. Some of this increasing maturity was evident at the 3rd Topical Meeting on Coherent Laser Radar: Technology and Applications. Topics included in discussions were: mesoscale wind fields, nocturnal valley drainage and clear air down bursts; airborne Doppler lidar studies and comparison of ground and airborne wind measurement; wind measurement over the sea for comparison with satellite borne microwave sensors; transport of wake vortices at airfield; coherent DIAL methods; a newly assembled Nd-YAG coherent lidar system; backscatter profiles in the atmosphere and wavelength dependence over the 9 to 11 micrometer region; beam propagation; rock and soil classification with an airborne 4-laser system; technology of a global wind profiling system; target calibration; ranging and imaging with coherent pulsed and CW system; signal fluctuations and speckle. Some of these activities are briefly reviewed.

  16. An airborne Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Dimarzio, C. A.

    1980-01-01

    A pulsed CO2 Doppler Lidar, developed for airborne measurements of atmospheric wind fields, is described. In-flight tests show that the device can be successfully utilized in the detection and measurement of mountain-wave turbulence and wind shear, and in the generation of time histories of wind-field variations in smooth flight. This Lidar is in the process of being configured for measurement of the atmospheric flow fields surrounding severe convective storms.

  17. Laser Doppler anemometry

    NASA Technical Reports Server (NTRS)

    Johnson, Dennis A.

    1988-01-01

    The material in this NASA TM is to appear as a chapter on Laser Doppler Anemometry (LDA) in the AGARDograph entitled, A Survey of Measurements and Measuring Techniques in Rapidly Distorted Compressible Turbulent Boundary Layers. The application of LDA (specifically, the dual-beam, burst-counter approach) to compressible flows is discussed. Subjects treated include signal processing, particle light scattering and tracking, data reduction and sampling bias, and three-dimensional measurements.

  18. Optical Doppler tomographic imaging of fluid flow velocity in highly scattering media

    SciTech Connect

    Chen, Z.; Milner, T.E.; Dave, D.; Nelson, J.S.

    1997-01-01

    An optical Doppler tomography (ODT) system that permits imaging of fluid flow velocity in highly scattering media is described. ODT combines Doppler velocimetry with the high spatial resolution of low-coherence optical interferometry to measure fluid flow velocity at discrete spatial locations. Tomographic imaging of particle flow velocity within a circular conduit submerged 1mm below the surface in a highly scattering phantom of Intralipid is demonstrated. {copyright} {ital 1997} {ital Optical Society of America}

  19. Laser double Doppler flowmeter

    NASA Astrophysics Data System (ADS)

    Poffo, L.; Goujon, J.-M.; Le Page, R.; Lemaitre, J.; Guendouz, M.; Lorrain, N.; Bosc, D.

    2014-05-01

    The Laser Doppler flowmetry (LDF) is a non-invasive method for estimating the tissular blood flow and speed at a microscopic scale (microcirculation). It is used for medical research as well as for the diagnosis of diseases related to circulatory system tissues and organs including the issues of microvascular flow (perfusion). It is based on the Doppler effect, created by the interaction between the laser light and tissues. LDF measures the mean blood flow in a volume formed by the single laser beam, that penetrate into the skin. The size of this measurement volume is crucial and depends on skin absorption, and is not directly reachable. Therefore, current developments of the LDF are focused on the use of always more complex and sophisticated signal processing methods. On the other hand, laser Double Doppler Flowmeter (FL2D) proposes to use two laser beams to generate the measurement volume. This volume would be perfectly stable and localized at the intersection of the two laser beams. With FL2D we will be able to determine the absolute blood flow of a specific artery. One aimed application would be to help clinical physicians in health care units.

  20. An investigation of particle turbulence quantities in a dense two-phase pipe flow, using laser Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Cline, Christopher Abbott

    The mean and turbulence statistics for the solid phase of a liquid-sold two-phase turbulent pipe flow were studied for particle concentrations up to 12.5 percent by volume. The Reynolds number based on the pipe diameter and the liquid kinematic viscosity was 14500, while the Reynolds number based on the mixture kinematic viscosity ranged from 9400 to 14500. The test section was 44 pipe diameters downstream of the pipe entrance. Measurements were made as close as one wall unit from the wall, using a two-component laser Doppler velocimeter. The calculated velocity statistics included the mean through fourth order central moments, cross correlation, and triple correlations. The working liquid was an aqueous sodium iodide solution which matched the index of refraction of the acrylic pipe and acrylic test at the wavelengths of the argon-ion laser. The particles had a mean diameter of 150 microns and a size dispersion of 50 to 180 microns. The particles were less dense than the liquid, with a particle-to-liquid density ratio of 0.66. the particle Reynolds number was less than 100. Measurements in an unladen pipe flow were in very good agreement with previous investigations, with the exception of elevated axial and radial turbulence intensities. The elevated values were attributed to the pipe wall or LDV measurement volume vibrating. The particle mean velocity in the particle-laden flow followed the same law of the wall relationship as for an unladen fluid when inner scaling was done based on the bulk mixture properties. All profiles of the particle turbulence quantities were similar in shape and behavior to the unladen liquid profiles, with most profiles being self-similar with particle concentration. This suggests that the particles behave more or less like fluid elements embedded in a continuous fluid. The results also indirectly suggest that the particles are affecting the coherent turbulence structures that are responsible for turbulence production in the wall region.

  1. A dedicated storage ring for Far-IR coherent synchrotron radiation at the ALS

    SciTech Connect

    Barry, W.C.; Baptist, K.M.; Benjegerdes, R.J.; Biocca, A.K.; Byrd, J.M.; Byrne, W.E.; Cambie, D.; Chin, M.J.; Harkins, J.P.; Kwiatkowski, S.; Li, D.; Marks, S.; Martin, M.C.; McKinney, W.R.; Munson, D.V.; Nishimura, H.; Paterson, J.A.; Plate, D.W.; Rex, K.R.; Robin, D.S.; Rossi, S.L.; Sannibale, F.; Scarvie, T.; Schlueter, R.D.; Steier, C.A.; Stover, G.D.; Thur, W.G.; Jung, J.Y.; Zbasnik, J.P.

    2002-05-31

    We present the concepts for a storage ring dedicated to and optimized for the production of stable coherent synchrotron radiation (CSR) over the far-infrared wavelength range from about 200 microns to 1 mm.

  2. The SPAce Readiness Coherent Lidar Experiment (SPARCLE) Space Shuttle Mission

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Emmitt, G. David

    1998-01-01

    For over 20 years researchers have been investigating the feasibility of profiling tropospheric vector wind velocity from space with a pulsed Doppler lidar. Efforts have included theoretical development, system and mission studies, technology development, and ground-based and airborne measurements. Now NASA plans to take the next logical step towards enabling operational global tropospheric wind profiles by demonstrating horizontal wind measurements from the Space Shuttle in early 2001 using a coherent Doppler wind lidar system.

  3. Note: Aligned deposition and modal characterization of micron and submicron poly(methyl methacyrlate) fiber cantilevers.

    PubMed

    Nain, Amrinder S; Filiz, Sinan; Ozdoganlar, O Burak; Sitti, Metin; Amon, Cristina

    2010-01-01

    Polymeric micro-/nanofibers are finding increasing use as sensors for novel applications. Here, we demonstrate the ability to deposit an array of poly(methyl methacyrlate) fibers with micron and submicron diameters in aligned configurations on customized piezoelectric shakers. Using lateral motion of an atomic force microscope tip, fibers are broken to obtain fiber cantilevers of high aspect ratio (length/diameter > 20). The resonant frequencies of fabricated microfiber cantilevers are experimentally measured using a laser Doppler vibrometer. An average Young's modulus of 3.5 GPa and quality factor of 20 were estimated from the experimentally obtained frequency responses.

  4. The Multi-Center Airborne Coherent Atmospheric Wind Sensor: Recent Measurements and Future Applications

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry; Cutten, Dean R.; Howell, Burgess F.; Hardesty, Robert M.; Tratt, David M.; Darby, Lisa S.

    1999-01-01

    The atmospheric lidar remote sensing groups of NOAA Environmental Technology Laboratory, Jet Propulsion Laboratory and NASA Marshall Space Flight Center jointly developed an airborne scanning coherent Doppler Lidar. We describe the system, present recent measurement (including the first wind fields measured within a hurricane using Doppler lidar), and describe prospective instrument improvements and research applications.

  5. In vivo imaging of retinal hemodynamics with OCT angiography and Doppler OCT

    PubMed Central

    Huang, Shenghai; Shen, Meixiao; Zhu, Dexi; Chen, Qi; Shi, Ce; Chen, Zhongping; Lu, Fan

    2016-01-01

    Retinal hemodynamics is important for early diagnosis and precise monitoring in retinal vascular diseases. We propose a novel method for measuring absolute retinal blood flow in vivo using the combined techniques of optical coherence tomography (OCT) angiography and Doppler OCT. Doppler values can be corrected by Doppler angles extracted from OCT angiography images. A three-dimensional (3D) segmentation algorithm based on dynamic programming was developed to extract the 3D boundaries of optic disc vessels, and Doppler angles were calculated from 3D vessel geometry. The accuracy of blood flow from the Doppler OCT was validated using a flow phantom. The feasibility of the method was tested on a subject in vivo. The pulsatile retinal blood flow and the parameters for retinal hemodynamics were successfully obtained. PMID:26977370

  6. Orbit determination singularities in the Doppler tracking of a planetary orbiter

    NASA Technical Reports Server (NTRS)

    Wood, L. J.

    1985-01-01

    On a number of occasions, spacecraft launched by the U.S. have been placed into orbit about the moon, Venus, or Mars. It is pointed out that, in particular, in planetary orbiter missions two-way coherent Doppler data have provided the principal data type for orbit determination applications. The present investigation is concerned with the problem of orbit determination on the basis of Doppler tracking data in the case of a spacecraft in orbit about a natural body other than the earth or the sun. Attention is given to Doppler shift associated with a planetary orbiter, orbit determination using a zeroth-order model for the Doppler shift, and orbit determination using a first-order model for the Doppler shift.

  7. Flow tracing fidelity of scattering aerosol in laser Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Kirsch, K. J.

    1974-01-01

    An experimental method for determinating the flow tracing fidelity of a scattering aerosol used in laser Doppler velocimeters was developed with particular reference to the subsonic turbulence measurements. The method employs the measurement of the dynamic response of a flow seeding aerosol excited by acoustic waves. The amplitude and frequency of excitation were controlled to simulate the corresponding values of fluid turbulence components. Experimental results are presented on the dynamic response of aerosols over the size range from 0.1 to 2.0 microns in diameter and over the frequency range 100 Hz to 100 kHz. It was observed that unit density spherical scatterers with diameters of 0.2 microns followed subsonic air turbulence frequency components up to 100 kHz with 98 percent fidelity.

  8. Flow tracing fidelity of scattering aerosol in laser Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Kirsch, K. J.

    1975-01-01

    An experimental method for the determination of the flow-tracing fidelity of a scattering aerosol used in laser Doppler velocimeters was developed with particular reference to the subsonic turbulence measurements. The method employs the measurement of the dynamic response of a flow-seeding aerosol excited by acoustic waves. The amplitude and frequency of excitation were controlled in order to simulate the corresponding values of fluid turbulence components. Experimental results are presented on the dynamic response of aerosols over the size range from 0.1 to 2.0 microns in diam and over the frequency range 100 Hz to 100 kHz. It was observed that unit-density spherical scatterers with diameters of 0.2 micron followed subsonic air turbulence frequency components up to 100 kHz with 98% fidelity.

  9. An Optical Fiber Communication System Based on Coherent Modulation. Part 1.

    DTIC Science & Technology

    1985-06-01

    Coherent optical communication systems have potential application possibilities which make them a very interesting research area. Compared to present... optical communication systems operating at 1.3 micron or 1.55 micron they can operate with 20 dB’s increase in receiver sensitivity which allows

  10. Crawling wave optical coherence elastography.

    PubMed

    Meemon, Panomsak; Yao, Jianing; Chu, Ying-Ju; Zvietcovich, Fernando; Parker, Kevin J; Rolland, Jannick P

    2016-03-01

    Elastography is a technique that measures and maps the local elastic property of biological tissues. Aiming for detection of micron-scale inclusions, various optical elastography, especially optical coherence elastography (OCE), techniques have been investigated over the past decade. The challenges of current optical elastography methods include the decrease in elastographic resolution as compared with its parent imaging resolution, the detection sensitivity and accuracy, and the cost of the overall system. Here we report for the first time, we believe, on an elastography technique-crawling wave optical coherence elastography (CRW-OCE)-which significantly lowers the requirements on the imaging speed and opens the path to high-resolution and high-sensitivity OCE at relatively low cost. Methods of crawling wave excitation, data acquisition, and crawling wave tracking are presented.

  11. Doppler Feature Based Classification of Wind Profiler Data

    NASA Astrophysics Data System (ADS)

    Sinha, Swati; Chandrasekhar Sarma, T. V.; Lourde. R, Mary

    2017-01-01

    Wind Profilers (WP) are coherent pulsed Doppler radars in UHF and VHF bands. They are used for vertical profiling of wind velocity and direction. This information is very useful for weather modeling, study of climatic patterns and weather prediction. Observations at different height and different wind velocities are possible by changing the operating parameters of WP. A set of Doppler power spectra is the standard form of WP data. Wind velocity, direction and wind velocity turbulence at different heights can be derived from it. Modern wind profilers operate for long duration and generate approximately 4 megabytes of data per hour. The radar data stream contains Doppler power spectra from different radar configurations with echoes from different atmospheric targets. In order to facilitate systematic study, this data needs to be segregated according the type of target. A reliable automated target classification technique is required to do this job. Classical techniques of radar target identification use pattern matching and minimization of mean squared error, Euclidean distance etc. These techniques are not effective for the classification of WP echoes, as these targets do not have well-defined signature in Doppler power spectra. This paper presents an effective target classification technique based on range-Doppler features.

  12. Long duration meteor echoes characterized by Doppler spectrum bifurcation

    NASA Astrophysics Data System (ADS)

    Bourdillon, A.; Haldoupis, C.; Hanuise, C.; Le Roux, Y.; Menard, J.

    2005-03-01

    We report on a new category of long lasting meteor echoes observed occasionally with HF and VHF radars. These meteoric returns, which have lifetimes from many seconds to a few minutes, are characterized by a distinct Doppler spectral signature showing a pronounced Doppler bifurcation which includes narrow bands of discrete Doppler velocities, often of opposite polarity. The large signal to noise ratios and the narrowness of the spectra imply that coherent or Bragg scattering is not of relevance here, therefore these echoes do not associate with the long living meteor-induced backscatter (MIB) from the lower E region. A reasonable interpretation needs to explain both the Doppler spectrum bifurcation and the long echo duration. As such, we propose the idea of a structured vertical wind shear in the lower E region which traps different fragments of a meteor trail plasma in the same way that sporadic E layers form. These trail parts inside the shear-related wind profile may act as relatively long-lasting meteoric reflectors moving with different Doppler velocities, also of opposite polarity.

  13. Clinical applications of doppler ultrasound

    SciTech Connect

    Taylor, K.J.W.; Burns, P.N.; Well, P.N.T.

    1987-01-01

    This book introduces a guide to the physical principles and instrumentation of duplex Doppler ultrasound and its applications in obstetrics, gynecology, neonatology, gastroentology, and evaluation of peripheral vascular disease. The book provides information needed to perform Doppler ultrasound examinations and interpret the results. An introduction to Doppler physics and instrumentation is followed by a thorough review of hemodynamics, which explains the principles underlying interpretation of Doppler signals. Of special note is the state-of-the-art coverage of new applications of Doppler in recognition of high-risk pregnancy, diagnosis of intrauterine growth retardation, investigation of neonatal blood flow, evaluation of first-trimester pregnancy, and diagnosis of gastrointestinal disease. The book also offers guidelines on the use of Doppler ultrasound in diagnosing carotid disease, deep venous thrombosis, and aorta/femoral disease.

  14. 3-D ultrafast Doppler imaging applied to the noninvasive mapping of blood vessels in vivo.

    PubMed

    Provost, Jean; Papadacci, Clement; Demene, Charlie; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

    2015-08-01

    Ultrafast Doppler imaging was introduced as a technique to quantify blood flow in an entire 2-D field of view, expanding the field of application of ultrasound imaging to the highly sensitive anatomical and functional mapping of blood vessels. We have recently developed 3-D ultrafast ultrasound imaging, a technique that can produce thousands of ultrasound volumes per second, based on a 3-D plane and diverging wave emissions, and demonstrated its clinical feasibility in human subjects in vivo. In this study, we show that noninvasive 3-D ultrafast power Doppler, pulsed Doppler, and color Doppler imaging can be used to perform imaging of blood vessels in humans when using coherent compounding of 3-D tilted plane waves. A customized, programmable, 1024-channel ultrasound system was designed to perform 3-D ultrafast imaging. Using a 32 × 32, 3-MHz matrix phased array (Vermon, Tours, France), volumes were beamformed by coherently compounding successive tilted plane wave emissions. Doppler processing was then applied in a voxel-wise fashion. The proof of principle of 3-D ultrafast power Doppler imaging was first performed by imaging Tygon tubes of various diameters, and in vivo feasibility was demonstrated by imaging small vessels in the human thyroid. Simultaneous 3-D color and pulsed Doppler imaging using compounded emissions were also applied in the carotid artery and the jugular vein in one healthy volunteer.

  15. Laser Doppler diagnostics for orthodontia

    NASA Astrophysics Data System (ADS)

    Ryzhkova, Anastasia V.; Lebedeva, Nina G.; Sedykh, Alexey V.; Ulyanov, Sergey S.; Lepilin, Alexander V.; Kharish, Natalia A.

    2004-06-01

    The results of statistical analysis of Doppler spectra of intensity fluctuations of light, scattered from mucous membrane of oral cavity of healthy volunteers and patients, abused by the orthodontic diseases, are presented. Analysis of Doppler spectra, obtained from tooth pulp of patients, is carried out. New approach to monitoring of blood microcirculation in orthodontics is suggested. Influence of own noise of Doppler measuring system on formation of the output signal is studied.

  16. Phototransistor (PT) in the 2 Micron Region

    NASA Technical Reports Server (NTRS)

    Prather, Dennis; Sulima, Oleg V.

    2006-01-01

    Within the framework of the project the University of Delaware has developed InGaAsSb-based heterojunction phototransistors (HPT) structure with a large (1000 micron diameter) photosensitive/photoactive area. Two different compositions of quaternary alloys were used to provide the cutoff wavelength (50% of maximum quantum efficiency) of 2.4 micron (Type 1) and 2.15 micron (Type 2). The Type 1 HPT was composed of Al0.25Ga0.75As0.02Sb0.98 and In0.18Ga0.82As0.17Sb0.83 layers with room-temperature bandgaps of Eg approximates 1.0 eV and Eg approximates 0.54 eV, respectively. The layers are lattice-matched to a GaSb substrate. The growth started with a 0.15micron-thick n+-GaSb buffer layer and was completed with a 0.1 m-thick n+- GaSb contact layer doped with Te. The HPT structure includes a 0.5 m-thick n-type AlGaAsSb emitter, 0.8 micron-thick p-type composite base consisting of AlGaAsSb (0.3 m) and InGaAsSb (0.5 m) layers, and a 1.5micron - thick n type InGaAsSb collector. The Type 2 HPT differed by a higher bandgap In0.16Ga0.84As 0.14Sb0.86 layers with a room-temperature bandgap of Eg approximates 0.555 eV.

  17. Neutrino Induced Doppler Broadening

    PubMed Central

    Jolie, J.; Stritt, N.

    2000-01-01

    When a nucleus undergoes beta decay via the electron capture reaction, it emits an electron neutrino. The neutrino emission gives a small recoil to the atom, which can be experimentally observed as a Doppler broadening on subsequently emitted gamma rays. Using the two-axis flat-crystal spectrometer GAMS4 and the electron capture reaction in 152Eu, the motion of atoms having an excess kinetic energy of 3 eV in the solid state was studied. It is shown how the motion of the atom during the first hundreds of femtoseconds can be reconstructed. The relevance of this knowledge for a new neutrino helicity experiment is discussed. PMID:27551591

  18. Laser Doppler velocimetry primer

    NASA Technical Reports Server (NTRS)

    Bachalo, William D.

    1985-01-01

    Advanced research in experimental fluid dynamics required a familiarity with sophisticated measurement techniques. In some cases, the development and application of new techniques is required for difficult measurements. Optical methods and in particular, the laser Doppler velocimeter (LDV) are now recognized as the most reliable means for performing measurements in complex turbulent flows. And such, the experimental fluid dynamicist should be familiar with the principles of operation of the method and the details associated with its application. Thus, the goals of this primer are to efficiently transmit the basic concepts of the LDV method to potential users and to provide references that describe the specific areas in greater detail.

  19. Coherent Raman spectroscopy for supersonic flow measurments

    NASA Technical Reports Server (NTRS)

    She, C. Y.

    1986-01-01

    In collaboration with NASA/Langley Research Center, a truly nonintrusive and nonseeding method for measuring supersonic molecular flow parameters was proposed and developed at Colorado State University. The feasibility of this Raman Doppler Velocimetry (RDV), currently operated in a scanning mode, was demonstrated not only in a laboratory environment at Colorado State University, but also in a major wind tunnel at NASA/Langley Research Center. The research progress of the RDV development is summarized. In addition, methods of coherent Rayleigh-Brillouin spectroscopy and single-pulse coherent Raman spectroscopy are investigated, respectively, for measurements of high-pressure and turbulent flows.

  20. Exploratory 5-micron spectrum of Uranus

    SciTech Connect

    Orton, G.S.; Kaminski, C.D.

    1989-01-01

    The intensity peak at 4.8 microns characterizing the spectrum observed for the disk of Uranus near 5 microns, in June 1987, exhibits steep declines at shorter and longer wavelength. An exploratory discussion is presented of various models in view of these data; it is noted that some component of the radiation must originate near the 140 K atmospheric irrespective of the radiation's origin in sunlight or thermal emission; physical considerations dictate that it be at least partly thermal in origin. One model consistent with the data requires the presence of a cloud top at the 8-bar level. 30 references.

  1. Spacecraft Doppler tracking with a VLBI antenna

    NASA Astrophysics Data System (ADS)

    Comoretto, G.; Iess, L.; Bertotti, B.; Brenkle, J. P.; Horton, T.

    1990-02-01

    Preliminary results are reported from Doppler-shift measurements to the Voyager-2 spacecraft at a distance of 26 AU, obtained using the 32-m VLBI antenna at Medicina (Italy) during July and August 1988. The apparatus comprises the el-az antenna, an S-X-band receiver, a hydrogen maser to generate the reference signal, a Mark III VLBI terminal, and a digital tone extractor capable of isolating a tone of known frequency from a noisy signal and giving its phase and amplitude. A signal transmitted in S-band from the NASA Deep Space Network (DSN) station in Australia and retransmitted coherently in X-band by Voyager, was received 7 h 6 min later at Medicina and at the DSN station in Madrid. Sample data are presented graphically and shown to be of generally high quality; further in-depth analysis is under way.

  2. Spacecraft Doppler tracking with a VLBI antenna

    NASA Technical Reports Server (NTRS)

    Comoretto, G.; Iess, L.; Bertotti, B.; Brenkle, J. P.; Horton, T.

    1990-01-01

    Preliminary results are reported from Doppler-shift measurements to the Voyager-2 spacecraft at a distance of 26 AU, obtained using the 32-m VLBI antenna at Medicina (Italy) during July and August 1988. The apparatus comprises the el-az antenna, an S-X-band receiver, a hydrogen maser to generate the reference signal, a Mark III VLBI terminal, and a digital tone extractor capable of isolating a tone of known frequency from a noisy signal and giving its phase and amplitude. A signal transmitted in S-band from the NASA Deep Space Network (DSN) station in Australia and retransmitted coherently in X-band by Voyager, was received 7 h 6 min later at Medicina and at the DSN station in Madrid. Sample data are presented graphically and shown to be of generally high quality; further in-depth analysis is under way.

  3. Spacecraft Doppler tracking with a VLBI antenna

    NASA Technical Reports Server (NTRS)

    Comoretto, G.; Iess, L.; Bertotti, B.; Brenkle, J. P.; Horton, T.

    1990-01-01

    Preliminary results are reported from Doppler-shift measurements to the Voyager-2 spacecraft at a distance of 26 AU, obtained using the 32-m VLBI antenna at Medicina (Italy) during July and August 1988. The apparatus comprises the el-az antenna, an S-X-band receiver, a hydrogen maser to generate the reference signal, a Mark III VLBI terminal, and a digital tone extractor capable of isolating a tone of known frequency from a noisy signal and giving its phase and amplitude. A signal transmitted in S-band from the NASA Deep Space Network (DSN) station in Australia and retransmitted coherently in X-band by Voyager, was received 7 h 6 min later at Medicina and at the DSN station in Madrid. Sample data are presented graphically and shown to be of generally high quality; further in-depth analysis is under way.

  4. Theory, design, and micron-scale implementation of fully optical logic gates and optical clock circuits

    NASA Astrophysics Data System (ADS)

    Rahmani Nejad, Akbar

    2009-08-01

    In this paper, it is tried to provide an innovative method to overcome several limitations of state of the art of logical gates and microprocessors, by implementation of micron-scaled optical gates. This technology can overcome such limitations, i.e. processing speed, heat dissipation, electromagnetic radiation and electrical noise immunity. This technology can be fully or partially feasible by substitution of common semiconductor technology with optical logic gates. By implementation of micron-scale optical fiber, optical couplers, fiber optical amplifiers, or fiber lasers, optical attenuators, optical fiber brag grating, femto-second optical lasers, and implementation of fundamental properties of optical coherent light, e.g. superposition, interference, phase delay, etc, it is possible to fabricate micron-scale universal logical gates, i.e. optical NAND gates, optical NOR gates, optical Exclusive-OR, optical exclusive-NOR gates and subsequently fabrication of sequential circuits (optical flip-flops), that all are fundamental blocks of microprocessors. Optical coherent light is produced by femtosecond lasers and is supplied to a network of micron-scaled fiber optics, fiber optical lasers, attenuators, fiber optical couplers, and finally are supplied to opto-couplers that change optical signals to electrical signals to be read by output console or to be written on memory cells. It is also possible to implement a combination of optical and semiconductor gates to decrease above mentioned limitations. The method of fabrication of optical gates is discussed in details and all necessary logical and technical aspects are provided too. The fundamental implemented aspect is superposition of coherent lights in fiber optic couplers. By implementation of femtosecond laser pulses, it is possible to reach to much higher frequencies of about hundreds to thousands of terahertz. Alternative optical method is provided here, e.g. implementation of fiber loops as clock circuit or

  5. Interpreting the 10 micron Astronomical Silicate Feature

    NASA Astrophysics Data System (ADS)

    Bowey, Janet E.

    1998-11-01

    10micron spectra of silicate dust in the diffuse medium towards Cyg OB2 no. 12 and towards field and embedded objects in the Taurus Molecular Cloud (TMC) were obtained with CGS3 at the United Kingdom Infrared Telescope (UKIRT). Cold molecular-cloud silicates are sampled in quiescent lines of sight towards the field stars Taurus-Elias 16 and Elias 13, whilst observations of the embedded young stellar objects HL Tau, Taurus-Elias 7 (Haro6-10) and Elias 18 also include emission from heated dust. To obtain the foreground silicate absorption profiles, featureless continua are estimated using smoothed astronomical and laboratory silicate emissivities. TMC field stars and Cyg OB2 no. 12 are modelled as photospheres reddened by foreground continuum and silicate extinction. Dust emission in the non-photospheric continua of HL Tau and Elias 7 (Haro6-10) is distinguished from foreground silicate absorption using a 10micron disk model, based on the IR-submm model of T Tauri stars by Adams, Lada & Shu (1988), with terms added to represent the foreground continuum and silicate extinction. The absorption profiles of HL Tau and Elias 7 are similar to that of the field star Elias 16. Fitted temperature indices of 0.43 (HL Tau) and 0.33 (Elias 7) agree with Boss' (1996) theoretical models of the 200-300K region, but are lower than those of IR-submm disks (0.5-0.61; Mannings & Emerson 1994); the modelled 10micron emission of HL Tau is optically thin, that of Elias 7 is optically thick. A preliminary arcsecond-resolution determination of the 10micron emissivity near θ1 Ori D in the Trapezium region of Orion and a range of emission temperatures (225-310K) are derived from observations by T. L. Hayward; this Ney-Allen emissivity is 0.6micron narrower than the Trapezium emissivity obtained by Forrest et al. (1975) with a large aperture. Published interstellar grain models, elemental abundances and laboratory studies of Solar System silicates (IDPs, GEMS and meteorites), the 10micron

  6. Wind Field Measurements With Airborne Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Menzies, Robert T.

    1999-01-01

    In collaboration with lidar atmospheric remote sensing groups at NASA Marshall Space Flight Center and National Oceanic and Atmospheric Administration (NOAA) Environmental Technology Laboratory, we have developed and flown the Multi-center Airborne Coherent Atmospheric Wind Sensor (MACAWS) lidar on the NASA DC-8 research aircraft. The scientific motivations for this effort are: to obtain measurements of subgrid scale (i.e. 2-200 km) processes and features which may be used to improve parameterizations in global/regional-scale models; to improve understanding and predictive capabilities on the mesoscale; and to assess the performance of Earth-orbiting Doppler lidar for global tropospheric wind measurements. MACAWS is a scanning Doppler lidar using a pulsed transmitter and coherent detection; the use of the scanner allows 3-D wind fields to be produced from the data. The instrument can also be radiometrically calibrated and used to study aerosol, cloud, and surface scattering characteristics at the lidar wavelength in the thermal infrared. MACAWS was used to study surface winds off the California coast near Point Arena, with an example depicted in the figure below. The northerly flow here is due to the Pacific subtropical high. The coastal topography interacts with the northerly flow in the marine inversion layer, and when the flow passes a cape or point that juts into the winds, structures called "hydraulic expansion fans" are observed. These are marked by strong variation along the vertical and cross-shore directions. The plots below show three horizontal slices at different heights above sea level (ASL). Bottom plots are enlargements of the area marked by dotted boxes above. The terrain contours are in 200-m increments, with the white spots being above 600-m elevation. Additional information is contained in the original.

  7. Monolithic high peak-power coherent Doppler lidar system

    NASA Astrophysics Data System (ADS)

    Kotov, Leonid V.; Töws, Albert; Kurtz, Alfred; Bobkov, Konstantin K.; Aleshkina, Svetlana S.; Bubnov, Mikhail M.; Lipatov, Denis S.; Guryanov, Alexey N.; Likhachev, Mikhail

    2016-03-01

    In this work we present a monolithic lidar system, based on a newly-developed double-clad large mode area (LMA) polarization-maintaining Er-doped fiber and specially designed LMA passive components. Optimization of the fiber designs resulted in as high as 100 W of SBS limited peak power. The amplifier and its passive components (circulator and collimator) were integrated in an existing lidar system. The enhanced lidar system provides three times increase of scanning range compared to one based on standard telecom-grade amplifiers.

  8. Coherent amplified optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Rao, Bin; Chen, Zhongping

    2007-07-01

    A technique to improve the signal-to-noise ratio (SNR) of a high speed 1300 nm swept source optical coherence tomography (SSOCT) system was demonstrated. A semiconductor optical amplifier (SOA) was employed in the sample arm to coherently amplify the weak light back-scattered from sample tissue without increasing laser power illuminated on the sample. The image quality improvement was visualized and quantified by imaging the anterior segment of a rabbit eye at imaging speed of 20,000 A-lines per second. The theory analysis of SNR gain is given followed by the discussion on the technologies that can further improve the SNR gain.

  9. Detection of Fast Moving and Accelerating Targets Compensating Range and Doppler Migration

    DTIC Science & Technology

    2014-06-01

    Radon -Fourier transform has been introduced to realize long- term coherent integration of the moving targets with range migration [8, 9]. Radon ...2010) Long-time coherent integration for radar target detection base on Radon -Fourier transform, in Proceedings of the IEEE Radar Conference, pp...432–436. 9. Xu, J., Yu, J., Peng, Y. & Xia, X. (2011) Radon -Fourier transform for radar target detection, I: Generalized Doppler filter bank, IEEE

  10. Coherence, Pseudo-Coherence, and Non-Coherence.

    ERIC Educational Resources Information Center

    Enkvist, Nils Erik

    Analysis of the factors that make a text coherent or non-coherent suggests that total coherence requires cohesion not only on the textual surface but on the semantic level as well. Syntactic evidence of non-coherence includes lack of formal agreement blocking a potential cross-reference, anaphoric and cataphoric references that do not follow their…

  11. Sub-micron particle sampler apparatus and method for sampling sub-micron particles

    DOEpatents

    Gay, D.D.; McMillan, W.G.

    1984-04-12

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however, the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis. 6 figures.

  12. Differential Laser Doppler based Non-Contact Sensor for Dimensional Inspection with Error Propagation Evaluation

    PubMed Central

    Mekid, Samir; Vacharanukul, Ketsaya

    2006-01-01

    To achieve dynamic error compensation in CNC machine tools, a non-contact laser probe capable of dimensional measurement of a workpiece while it is being machined has been developed and presented in this paper. The measurements are automatically fed back to the machine controller for intelligent error compensations. Based on a well resolved laser Doppler technique and real time data acquisition, the probe delivers a very promising dimensional accuracy at few microns over a range of 100 mm. The developed optical measuring apparatus employs a differential laser Doppler arrangement allowing acquisition of information from the workpiece surface. In addition, the measurements are traceable to standards of frequency allowing higher precision.

  13. Doppler Beats or Interference Fringes?

    ERIC Educational Resources Information Center

    Kelly, Paul S.

    1979-01-01

    Discusses the following: another version of Doppler beats; alternate proof of spin-1 sin-1/2 problems; some mechanisms related to Dirac's strings; Doppler redshift in oblique approach of source and observer; undergraduate experiment on noise thermometry; use of the time evolution operator; resolution of an entropy maximization controversy;…

  14. Doppler Beats or Interference Fringes?

    ERIC Educational Resources Information Center

    Kelly, Paul S.

    1979-01-01

    Discusses the following: another version of Doppler beats; alternate proof of spin-1 sin-1/2 problems; some mechanisms related to Dirac's strings; Doppler redshift in oblique approach of source and observer; undergraduate experiment on noise thermometry; use of the time evolution operator; resolution of an entropy maximization controversy;…

  15. The 11 Micron Emissions of Carbon Stars

    NASA Technical Reports Server (NTRS)

    Goebel, J. H.; Cheeseman, P.; Gerbault, F.

    1995-01-01

    A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing C/O resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this

  16. The 11 Micron Emissions of Cabon Stars

    NASA Technical Reports Server (NTRS)

    Goebel, J. H.; Cheeseman, P.; Gerbault, F.

    1995-01-01

    A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing CIO resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this

  17. Doppler effect induced spin relaxation boom

    PubMed Central

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-01-01

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures. PMID:26996253

  18. Doppler effect induced spin relaxation boom

    NASA Astrophysics Data System (ADS)

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-03-01

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures.

  19. Doppler effect induced spin relaxation boom.

    PubMed

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-03-21

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures.

  20. Doppler lidar sampling strategies and accuracies: Regional scale

    NASA Technical Reports Server (NTRS)

    Emmitt, G. D.

    1985-01-01

    It has been proposed that a Doppler lidar be placed in a polar orbit and scanned to provide estimates of lower tropospheric winds twice per day and with a spatial resolution of 300 km. Initial feasibility studies conducted primarily by NOAA and NASA presented an optimistic outlook for a space based lidar. The technology appeared within reach and initial computer simulations suggested that acceptable accuracies could be obtained. Those early studies exposed, however, several potential problem areas which included: (1) the algorithms for computing the wind vectors did not perform well when there were coherent gradients in the wind fields; and (2) the lifetime and power requirements of the lidar put severe restrictions on the pulse repetition frequency (PRF). These two basic problems are currently being addressed by a Doppler lidar simulation study focussed upon three primary objectives: (1) to develop optimum scan parameters and shot patterns for a satellite-based Doppler lidar; (2) to develop robust algorithms for computing wind vectors from lidar returns; and (3) to evaluate the impact of coherent mesoscale structures (wind gradients, clouds, aerosols) on up-scale wind estimates. An overview is provided of the simulation efforts with particular emphasis upon rationale and methodology. Since this research is currently underway, any results shown are meant only as evidence of progress.

  1. Optical Coherence Tomography

    NASA Astrophysics Data System (ADS)

    Huang, David

    Optical coherence tomography (OCT) is a new method for noninvasive cross-sectional imaging in biological systems. In OCT, the longitudinal locations of tissue structures are determined by measuring the time-of-flight delays of light backscattered from these structures. The optical delays are measured by low coherence interferometry. Information on lateral position is provided by transverse scanning of the probe beam. The two dimensional map of optical scattering from internal tissue microstructures is then represented in a false-color or grayscale image. OCT is the optical analog of ultrasonic pulse-echo imaging, but with greatly improved spatial resolutions (a few microns). This thesis describes the development of this new high resolution tomographic imaging technology and the demonstration of its use in a variety of tissues under both in vitro and in vivo conditions. In vitro OCT ranging and imaging studies were performed using human ocular and arterial tissues, two clinically relevant examples of transparent and turbid media, respectively. In the anterior eye, precise measurements of cornea and anterior chamber dimensions were made. In the arterial specimens, the differentiation between fatty -calcified and fibromuscular tissues was demonstrated. In vivo OCT imaging in the retina and optic nerve head in human subjects was also performed. The delineation of retinal layers, which has not been possible with other noninvasive imaging techniques, is demonstrated in these OCT images. OCT has high spatial resolution but limited penetration into turbid tissue. It has potential for diagnostic applications where high resolution is needed and optical access is available, such as in the eye, skin, surgically exposed tissues, and surfaces that can be reached by various catheters and endoscopic probes. In particular, the measurement of fine retinal structures promises improvements in the diagnosis and management of glaucoma, macular edema and other vitreo-retinal diseases

  2. Requirements and Technology Advances for Global Wind Measurement with a Coherent Lidar: A Shrinking Gap

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Kavaya, Michael J.; Yu, Jirong; Koch, Grady J.; Amzajerdian, Farzin; Singh, Upendra N.; Emmitt, G. David

    2007-01-01

    Early concepts to globally measure vertical profiles of vector horizontal wind from space planned on an orbit height of 525 km, a single pulsed coherent Doppler lidar system to cover the full troposphere, and a continuously rotating telescope/scanner that mandated a vertical line of sight wind profile from each laser shot. Under these conditions system studies found that laser pulse energies of approximately 20 J at 10 Hz pulse repetition rate with a rotating telescope diameter of approximately 1.5 m was required. Further requirements to use solid state laser technology and an eyesafe wavelength led to the relatively new 2-micron solid state laser. With demonstrated pulse energies near 20 mJ at 5 Hz, and no demonstration of a rotating telescope maintaining diffraction limited performance in space, the technology gap between requirements and demonstration was formidable. Fortunately the involved scientists and engineers set out to reduce the gap, and through a combination of clever ideas and technology advances over the last 15 years, they have succeeded. This paper will detail the gap reducing factors and will present the current status.

  3. Neurosurgical hand-held optical coherence tomography (OCT) forward-viewing probe

    NASA Astrophysics Data System (ADS)

    Sun, Cuiru; Lee, Kenneth K. C.; Vuong, Barry; Cusimano, Michael; Brukson, Alexander; Mariampillai, Adrian; Standish, Beau A.; Yang, Victor X. D.

    2012-02-01

    A prototype neurosurgical hand-held optical coherence tomography (OCT) imaging probe has been developed to provide micron resolution cross-sectional images of subsurface tissue during open surgery. This new ergonomic hand-held probe has been designed based on our group's previous work on electrostatically driven optical fibers. It has been packaged into a catheter probe in the familiar form factor of the clinically accepted Bayonet shaped neurosurgical non-imaging Doppler ultrasound probes. The optical design was optimized using ZEMAX simulation. Optical properties of the probe were tested to yield an ~20 um spot size, 5 mm working distance and a 3.5 mm field of view. The scan frequency can be increased or decreased by changing the applied voltage. Typically a scan frequency of less than 60Hz is chosen to keep the applied voltage to less than 2000V. The axial resolution of the probe was ~15 um (in air) as determined by the OCT system. A custom-triggering methodology has been developed to provide continuous stable imaging, which is crucial for clinical utility. Feasibility of this probe, in combination with a 1310 nm swept source OCT system was tested and images are presented to highlight the usefulness of such a forward viewing handheld OCT imaging probe. Knowledge gained from this research will lay the foundation for developing new OCT technologies for endovascular management of cerebral aneurysms and transsphenoidal neuroendoscopic treatment of pituitary tumors.

  4. Digital Doppler measurement with spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.; Hinedi, Sami M.; Labelle, Remi C.; Bevan, Roland P.; Del Castillo, Hector M.; Chong, Dwayne C.

    1991-01-01

    Digital and analog phase-locked loop (PLL) receivers were operated in parallel, each tracking the residual carrier from a spacecraft. The PLL tracked the downlink carrier and measured its instantaneous phase. This information, combined with a knowledge of the uplink carrier and the transponder ratio, permitted the computation of a Doppler observable. In this way, two separate Doppler measurements were obtained for one observation window. The two receivers agreed on the magnitude of the Doppler effect to within 1 mHz. There was less jitter on the data from the digital receiver. This was due to its smaller noise bandwidth. The demonstration and its results are described.

  5. GEOS-3 Doppler difference tracking

    NASA Technical Reports Server (NTRS)

    Rosenbaum, B.

    1977-01-01

    The Doppler difference method as applied to track the GEOS 3 spacecraft is discussed. In this method a pair of 2 GHz ground tracking stations simultaneously track a spacecraft beacon to generate an observable signal in which bias and instability of the carrier frequency cancel. The baselines are formed by the tracking sites at Bermuda, Rosman, and Merritt Island. Measurements were made to evaluate the effectiveness of the Doppler differencing procedure in tracking a beacon target with the high dynamic rate of the GEOS 3 orbit. Results indicate the precision of the differenced data to be at a level comparable to the conventional precise two way Doppler tracking.

  6. Digital Doppler measurement with spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.; Hinedi, Sami M.; Labelle, Remi C.; Bevan, Roland P.; Del Castillo, Hector M.; Chong, Dwayne C.

    1991-01-01

    Digital and analog phase-locked loop (PLL) receivers were operated in parallel, each tracking the residual carrier from a spacecraft. The PLL tracked the downlink carrier and measured its instantaneous phase. This information, combined with a knowledge of the uplink carrier and the transponder ratio, permitted the computation of a Doppler observable. In this way, two separate Doppler measurements were obtained for one observation window. The two receivers agreed on the magnitude of the Doppler effect to within 1 mHz. There was less jitter on the data from the digital receiver. This was due to its smaller noise bandwidth. The demonstration and its results are described.

  7. Micron Accurate Absolute Ranging System: Range Extension

    NASA Technical Reports Server (NTRS)

    Smalley, Larry L.; Smith, Kely L.

    1999-01-01

    The purpose of this research is to investigate Fresnel diffraction as a means of obtaining absolute distance measurements with micron or greater accuracy. It is believed that such a system would prove useful to the Next Generation Space Telescope (NGST) as a non-intrusive, non-contact measuring system for use with secondary concentrator station-keeping systems. The present research attempts to validate past experiments and develop ways to apply the phenomena of Fresnel diffraction to micron accurate measurement. This report discusses past research on the phenomena, and the basis of the use Fresnel diffraction distance metrology. The apparatus used in the recent investigations, experimental procedures used, preliminary results are discussed in detail. Continued research and equipment requirements on the extension of the effective range of the Fresnel diffraction systems is also described.

  8. 3- to 13-micron spectra of Io

    NASA Technical Reports Server (NTRS)

    Noll, Keith S.; Hammel, H. B.; Young, Leslie; Joiner, Joanna; Hackwell, J.; Lynch, D. K.; Russell, R.

    1993-01-01

    The Broadband Array Spectrograph System with the NASA Infrared Telescope Facility was used to obtain 3- to 13-micron spectra of Io on June 14-16, 1991. The extinction correction and its error for each standard star (Alpha Boo, Alpha Lyr, and Mu UMa) were found individually by performing an unweighted linear fit of instrumental magnitude as a function of airmass. The model results indicate two significant trends: (1) modest differences between the two hemispheres at lower background temperatures and (2) a tendency to higher temperatures, smaller areas, and less power from the warm component at higher background temperatures with an increased contrast between the two hemispheres. The increased flux from 8 to 13 microns is due primarily to a greater area on the Loki (trailing) hemisphere for the warm component, although temperature also plays a role.

  9. 3- to 13-micron spectra of Io

    NASA Technical Reports Server (NTRS)

    Noll, Keith S.; Hammel, H. B.; Young, Leslie; Joiner, Joanna; Hackwell, J.; Lynch, D. K.; Russell, R.

    1993-01-01

    The Broadband Array Spectrograph System with the NASA Infrared Telescope Facility was used to obtain 3- to 13-micron spectra of Io on June 14-16, 1991. The extinction correction and its error for each standard star (Alpha Boo, Alpha Lyr, and Mu UMa) were found individually by performing an unweighted linear fit of instrumental magnitude as a function of airmass. The model results indicate two significant trends: (1) modest differences between the two hemispheres at lower background temperatures and (2) a tendency to higher temperatures, smaller areas, and less power from the warm component at higher background temperatures with an increased contrast between the two hemispheres. The increased flux from 8 to 13 microns is due primarily to a greater area on the Loki (trailing) hemisphere for the warm component, although temperature also plays a role.

  10. Doppler shifts of radar return from the sea surface

    NASA Astrophysics Data System (ADS)

    Ermakov, S. A.; Kapustin, I. A.; Molkov, A. A.; Sergievskaya, I. A.; Shomina, O. V.

    2016-10-01

    Investigation of the Doppler shift of radar return from the sea surface is very important for better understanding of capabilities of exploitation of microwave radar for measuring velocities of marine currents. Here new field experiments carried out from a Platform on the Black Sea with a coherent X-band scatterometer, and a Doppler multifrequency (X- /C-/S-band) dual-polarized radar recently designed at IAP RAS are discussed. It is shown that the radar return contains both Bragg (polarized) and non polarized scattering components, presumably giving different contributions to radar Doppler shifts. Radar Doppler shifts were estimated using two different definitions as a) a frequency of the "centre of gravity" of an instantaneous radar return spectrum (ASIS) averaged over periods of dominant wind waves and b) the "centre of gravity" of the averaged over dominant wave periods spectrum (SAS). The ASIS and SAS values for both VV and HH-polarizations are shown to be different due to effects of radar backscatter modulation by dominant (long) wind waves. The radar Modulation Transfer Function (MTF) has been analyzed from experimental data and difference between SAS- and ASIS-values has been satisfactory explained using the measured MTF-values. It is obtained that experimental values of ASIS can be satisfactory described by the Bragg model despite the significant contribution of NP component to the radar backscatter. A physical explanation of the effect is given.

  11. Analysis of multiple scattering effects in optical Doppler tomography

    NASA Astrophysics Data System (ADS)

    Yura, Harold T.; Thrane, Lars; Andersen, Peter E.

    2005-08-01

    Optical Doppler tomography (ODT) combines Doppler velocimetry and optical coherence tomography (OCT) to obtain high-resolution cross-sectional imaging of particle flow velocity in scattering media such as the human retina and skin. Here, we present the results of a theoretical analysis of ODT where multiple scattering effects are included. The purpose of this analysis is to determine how multiple scattering affects the estimation of the depth-resolved localized flow velocity. Depth-resolved velocity estimates are obtained directly from the corresponding mean or standard deviation of the observed Doppler frequency spectrum. Thus, in the present analysis, the dependence of the mean and standard deviation of the Doppler shift on the scattering properties of the flowing medium are obtained. Taking the multiple scattering effects into account, we are able to explain previous measurements of depth-resolved retinal flow profiles where the influence of multiple scattering was observed [Yazdanfar et al., Opt. Lett. 25, 1448 (2000)]. To the best of our knowledge, no analytical model exists that are able to explain these observations.

  12. Analysis of multiple scattering effects in optical Doppler tomography

    NASA Astrophysics Data System (ADS)

    Yura, Harold T.; Thrane, Lars; Andersen, Peter E.

    2005-04-01

    Optical Doppler tomography (ODT) combines Doppler velocimetry and optical coherence tomography (OCT) to obtain high-resolution cross-sectional imaging of particle flow velocity in scattering media such as the human retina and skin. Here, we present the results of a theoretical analysis of ODT where multiple scattering effects are included. The purpose of this analysis is to determine how multiple scattering affects the estimation of the depth-resolved localized flow velocity. Depth-resolved velocity estimates are obtained directly from the corresponding mean or standard deviation of the observed Doppler frequency spectrum. Thus, in the present analysis, the dependence of the mean and standard deviation of the Doppler shift on the scattering properties of the flowing medium are obtained. Taking the multiple scattering effects into account, we are able to explain previous measurements of depth-resolved retinal flow profiles where the influence of multiple scattering was observed [Yazdanfar et al., Opt. Lett. 25, 1448 (2000)]. To the best of our knowledge, no analytical model exists that are able to explain these observations.

  13. Endoscopic Optical Coherence Tomography

    NASA Astrophysics Data System (ADS)

    Zhou, Chao; Fujimoto, James G.; Tsai, Tsung-Han; Mashimo, Hiroshi

    New gastrointestinal (GI) cancers are expected to affect more than 290,200 new patients and will cause more than 144,570 deaths in the United States in 2013 [1]. When detected and treated early, the 5-year survival rate for colorectal cancer increases by a factor of 1.4 [1]. For esophageal cancer, the rate increases by a factor of 2 [1]. The majority of GI cancers begin as small lesions that are difficult to identify with conventional endoscopy. With resolutions approaching that of histopathology, optical coherence tomography (OCT) is well suited for detecting the changes in tissue microstructure associated with early GI cancers. Since the lesions are not endoscopically apparent, however, it is necessary to survey a relatively large area of the GI tract. Tissue motion is another limiting factor in the GI tract; therefore, in vivo imaging must be performed at extremely high speeds. OCT imaging can be performed using fiber optics and miniaturized lens systems, enabling endoscopic OCT inside the human body in conjunction with conventional video endoscopy. An OCT probe can be inserted through the working channel of a standard endoscope, thus enabling depth-resolved imaging of tissue microstructure in the GI tract with micron-scale resolution simultaneously with the endoscopic view (Fig. 68.1).

  14. Supersonic Flows in Micron-Sized Geometries

    NASA Astrophysics Data System (ADS)

    Bayt, Robert; Breuer, Kenneth

    1998-11-01

    The results of experiments and numerical simulations of flows in micromachined converging-diverging nozzles are presented. The nozzles are fabricated using deep Reactive Ion Etching (DRIE) and are typically 20-30 microns at the throat with expansion ratios ranging from 5 to 20. The flow channels are 300 microns deep, resulting in a 10:1 or better aspect ratio at the throat. Experimental measurements of mass flow and thrust vs. pressure ratio are presented demonstrating the presence of choked and supersonic flow in the micron-scale gemoetries. Mass flow and thrust efficiencies are also presented and compared with results from two-dimensional Navier-Stokes simulations. It is found that, while the efficiencies are reasonably large (much better than one might expect, considering the small dimension of the nozzles), the boundary layers have a considerable effect, particularly on the thrust efficiency of the device, due to the relatively large displacement thickness which reduces the effective expansion ratio. The boundary layers at the top and bottom of the nozzles also affect the performance, particularly at low Reynolds numbers. Additional experimental and numerical results are also discussed.

  15. Release of Micronized Copper Particles from Pressure ...

    EPA Pesticide Factsheets

    Micronized copper pressure treated lumber (PTL) has recently been introduced to the consumer market as a replacement for ionized copper PTL. The presence of particulate rather than aqueous copper raises concerns about the exposure of humans as well as the environment to the particles. Two common pathways of exposure, leaching during contact with water and transfer during physical contact, were investigated to gage potential human and environmental risk during intended use of the product. Characterization, leaching tests, and wipe tests were conducted on two representative formulations of micronized copper PTL (micronized copper azole or MCA) to quantify the levels of copper present in the treated material and the amount of copper released during use as well as to determine the form (particle or ion) of the copper after it was released. Additionally, an ionized copper pressure treated wood (alkaline copper azole or ACA) was tested for comparison. The characterization showed that copper carbonate is the primary particle form in the MCA treated wood, but other forms are also present, particularly in the MCA-1 formulation, which contained a large amount of organically complexed copper. Microscopy showed that MCA-1 contained particles roughly half the size of MCA-2. The leaching results indicate that mostly (> ~95%) ionic copper is released from the MCA wood and that the particulate copper that was released is attached to cellulose and not free in solution. A sma

  16. Release of Micronized Copper Particles from Pressure ...

    EPA Pesticide Factsheets

    Micronized copper pressure treated lumber (PTL) has recently been introduced to the consumer market as a replacement for ionized copper PTL. The presence of particulate rather than aqueous copper raises concerns about the exposure of humans as well as the environment to the particles. Two common pathways of exposure, leaching during contact with water and transfer during physical contact, were investigated to gage potential human and environmental risk during intended use of the product. Characterization, leaching tests, and wipe tests were conducted on two representative formulations of micronized copper PTL (micronized copper azole or MCA) to quantify the levels of copper present in the treated material and the amount of copper released during use as well as to determine the form (particle or ion) of the copper after it was released. Additionally, an ionized copper pressure treated wood (alkaline copper azole or ACA) was tested for comparison. The characterization showed that copper carbonate is the primary particle form in the MCA treated wood, but other forms are also present, particularly in the MCA-1 formulation, which contained a large amount of organically complexed copper. Microscopy showed that MCA-1 contained particles roughly half the size of MCA-2. The leaching results indicate that mostly (> ~95%) ionic copper is released from the MCA wood and that the particulate copper that was released is attached to cellulose and not free in solution. A sma

  17. Evaluation of meteorological airborne Doppler radar

    NASA Technical Reports Server (NTRS)

    Hildebrand, P. H.; Mueller, C. K.

    1984-01-01

    This paper will discuss the capabilities of airborne Doppler radar for atmospheric sciences research. The evaluation is based on airborne and ground based Doppler radar observations of convective storms. The capability of airborne Doppler radar to measure horizontal and vertical air motions is evaluated. Airborne Doppler radar is shown to be a viable tool for atmospheric sciences research.

  18. Design of a near-IR Doppler instrument for planet searches

    NASA Astrophysics Data System (ADS)

    Zhao, Bo; Ge, Jian; Nguyen, Duy Cuong; Wang, Ji; Groot, John

    2010-07-01

    Doppler searches are extending to the near infrared to detect and characterize habitable planets around low mass stars. We present an optical design and performance of a near-IR Doppler instrument. This instrument has two operating modes covering 0.8-1.8 microns. One mode is called IRET, which consists of a fix-delay interferometer and a crossdispersed echelle spectrograph to simultaneously cover 0.8-1.35 microns with a spectral resolution of R=22000 on a 2k x 2k H2RG IR array. The other mode is called FIRST, which uses a silicon immersion grating as the main disperser to simultaneously cover 1.4-1.8 microns with a spectral resolution of R=55000 on the same detector as IRET. The triplepass parabola white pupil design is used to restrain background scatter radiation with stable configuration for precision radial velocity measurements. We used high index standard glasses for camera optics and VPH gratings as crossdispersers in both modes. The FIRST mode can be switched in and out conveniently while the IRET mode is kept without moving parts to increase its stability. This instrument is designed to deliver up to 1 m/s Doppler precision RV measurements of nearby bright M dwarfs at the Apache Point Observatory 3.5 meter telescope. The instrument is expected to be operational in the spring 2011.

  19. Partially Coherent Scattering in Stellar Chromospheres. Part 4; Analytic Wing Approximations

    NASA Technical Reports Server (NTRS)

    Gayley, K. G.

    1993-01-01

    Simple analytic expressions are derived to understand resonance-line wings in stellar chromospheres and similar astrophysical plasmas. The results are approximate, but compare well with accurate numerical simulations. The redistribution is modeled using an extension of the partially coherent scattering approximation (PCS) which we term the comoving-frame partially coherent scattering approximation (CPCS). The distinction is made here because Doppler diffusion is included in the coherent/noncoherent decomposition, in a form slightly improved from the earlier papers in this series.

  20. Target Calibration: Retro-Reflection Mechanisms at 2 Micron

    NASA Technical Reports Server (NTRS)

    Haner, David A.; Tratt, David M.

    1999-01-01

    With the growing use of 2-micrometer eye-safe solid-state laser transmitters in coherent Doppler lidar applications, there is increased interest in the reflectance properties of hard target calibration materials at this wavelength. One of the factors to be considered is the polarization characteristic of the transmitter/receiver. The two fundamental lidar systems are either based upon the backscattering of linearly polarized or circularly polarized light. Consequently, the response of calibration materials to the particular state of polarization of the incident radiation is an important consideration. Ideally the calibration materials should have a similar reflectance response to that of the remote scattering medium that is being observed. Also the material should be most efficiently adapted to the polarization characteristics of the lidar system. There are two measurement parameters that are useful in presenting the characteristics of polarization of reflecting materials. The first is the linear polarization ratio: mu (sub l) =I (sub ol)/I (sub sl), where ol denotes opposite linear and sl denotes same linear. The second is circular polarization ratio: mu (sub c) = I (sub sc)/I (sub oc) where ol denotes opposite circular and sc denotes same circular. Notice that the ratios are inverted with respect to same polarization. It is the relative values of these polarization ratios that are used to characterize the retro-reflectance mechanism. Measurement of these parameters is conveniently obtained by using the Stokes vectors corresponding to the polarized backscatter at and near the retro-angle.

  1. Doppler Lidar Vertical Velocity Statistics Value-Added Product

    SciTech Connect

    Newsom, R. K.; Sivaraman, C.; Shippert, T. R.; Riihimaki, L. D.

    2015-07-01

    Accurate height-resolved measurements of higher-order statistical moments of vertical velocity fluctuations are crucial for improved understanding of turbulent mixing and diffusion, convective initiation, and cloud life cycles. The Atmospheric Radiation Measurement (ARM) Climate Research Facility operates coherent Doppler lidar systems at several sites around the globe. These instruments provide measurements of clear-air vertical velocity profiles in the lower troposphere with a nominal temporal resolution of 1 sec and height resolution of 30 m. The purpose of the Doppler lidar vertical velocity statistics (DLWSTATS) value-added product (VAP) is to produce height- and time-resolved estimates of vertical velocity variance, skewness, and kurtosis from these raw measurements. The VAP also produces estimates of cloud properties, including cloud-base height (CBH), cloud frequency, cloud-base vertical velocity, and cloud-base updraft fraction.

  2. Doppler characteristics of sea clutter.

    SciTech Connect

    Raynal, Ann Marie; Doerry, Armin Walter

    2010-06-01

    Doppler radars can distinguish targets from clutter if the target's velocity along the radar line of sight is beyond that of the clutter. Some targets of interest may have a Doppler shift similar to that of clutter. The nature of sea clutter is different in the clutter and exo-clutter regions. This behavior requires special consideration regarding where a radar can expect to find sea-clutter returns in Doppler space and what detection algorithms are most appropriate to help mitigate false alarms and increase probability of detection of a target. This paper studies the existing state-of-the-art in the understanding of Doppler characteristics of sea clutter and scattering from the ocean to better understand the design and performance choices of a radar in differentiating targets from clutter under prevailing sea conditions.

  3. Dual-Doppler Feasibility Study

    NASA Technical Reports Server (NTRS)

    Huddleston, Lisa L.

    2012-01-01

    When two or more Doppler weather radar systems are monitoring the same region, the Doppler velocities can be combined to form a three-dimensional (3-D) wind vector field thus providing for a more intuitive analysis of the wind field. A real-time display of the 3-D winds can assist forecasters in predicting the onset of convection and severe weather. The data can also be used to initialize local numerical weather prediction models. Two operational Doppler Radar systems are in the vicinity of Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS); these systems are operated by the 45th Space Wing (45 SW) and the National Weather Service Melbourne, Fla. (NWS MLB). Dual-Doppler applications were considered by the 45 SW in choosing the site for the new radar. Accordingly, the 45th Weather Squadron (45 WS), NWS MLB and the National Aeronautics and Space Administration tasked the Applied Meteorology Unit (AMU) to investigate the feasibility of establishing dual-Doppler capability using the two existing systems. This study investigated technical, hardware, and software requirements necessary to enable the establishment of a dual-Doppler capability. Review of the available literature pertaining to the dual-Doppler technique and consultation with experts revealed that the physical locations and resulting beam crossing angles of the 45 SW and NWS MLB radars make them ideally suited for a dual-Doppler capability. The dual-Doppler equations were derived to facilitate complete understanding of dual-Doppler synthesis; to determine the technical information requirements; and to determine the components of wind velocity from the equation of continuity and radial velocity data collected by the two Doppler radars. Analysis confirmed the suitability of the existing systems to provide the desired capability. In addition, it is possible that both 45 SW radar data and Terminal Doppler Weather Radar data from Orlando International Airport could be used to alleviate any

  4. Pre-Launch End-to-End Testing Plans for the SPAce Readiness Coherent Lidar Experiment (SPARCLE)

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.

    1999-01-01

    The SPAce Readiness Coherent Lidar Experiment (SPARCLE) mission was proposed as a low cost technology demonstration mission, using a 2-micron, 100-mJ, 6-Hz, 25-cm, coherent lidar system based on demonstrated technology. SPARCLE was selected in late October 1997 to be NASA's New Millennium Program (NMP) second earth-observing (EO-2) mission. To maximize the success probability of SPARCLE, NASA/MSFC desired expert guidance in the areas of coherent laser radar (CLR) theory, CLR wind measurement, fielding of CLR systems, CLR alignment validation, and space lidar experience. This led to the formation of the NASA/MSFC Coherent Lidar Technology Advisory Team (CLTAT) in December 1997. A threefold purpose for the advisory team was identified as: 1) guidance to the SPARCLE mission, 2) advice regarding the roadmap of post-SPARCLE coherent Doppler wind lidar (CDWL) space missions and the desired matching technology development plan 3, and 3) general coherent lidar theory, simulation, hardware, and experiment information exchange. The current membership of the CLTAT is shown. Membership does not result in any NASA or other funding at this time. We envision the business of the CLTAT to be conducted mostly by email, teleconference, and occasional meetings. The three meetings of the CLTAT to date, in Jan. 1998, July 1998, and Jan. 1999, have all been collocated with previously scheduled meetings of the Working Group on Space-Based Lidar Winds. The meetings have been very productive. Topics discussed include the SPARCLE technology validation plan including pre-launch end-to-end testing, the space-based wind mission roadmap beyond SPARCLE and its implications on the resultant technology development, the current values and proposed future advancement in lidar system efficiency, and the difference between using single-mode fiber optical mixing vs. the traditional free space optical mixing. attitude information from lidar and non-lidar sensors, and pointing knowledge algorithms will

  5. Mathematical Models for Doppler Measurements

    NASA Technical Reports Server (NTRS)

    Lear, William M.

    1987-01-01

    Error analysis increases precision of navigation. Report presents improved mathematical models of analysis of Doppler measurements and measurement errors of spacecraft navigation. To take advantage of potential navigational accuracy of Doppler measurements, precise equations relate measured cycle count to position and velocity. Drifts and random variations in transmitter and receiver oscillator frequencies taken into account. Mathematical models also adapted to aircraft navigation, radar, sonar, lidar, and interferometry.

  6. Novel instantaneous laser Doppler velocimeter.

    PubMed

    Avidor, J M

    1974-02-01

    A laser Doppler velocimeter capable of directly measuring instantaneous velocities is described. The new LDV uses a novel detection technique based on the utilization of a static slightly defocused spherical Fabry-Perot interferometer used in conjunction with a special mask for the detection of instantaneous Doppler frequency shifts. The essential characteristics of this LDV are discussed, and such a system recently developed is described. Results of turbulent flow measurements show good agreement with data obtained using hot wire anemometry.

  7. High Resolution Doppler Lidar

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This Grant supported the development of an incoherent lidar system to measure winds and aerosols in the lower atmosphere. During this period the following activities occurred: (1) an active feedback system was developed to improve the laser frequency stability; (2) a detailed forward model of the instrument was developed to take into account many subtle effects, such as detector non-linearity; (3) a non-linear least squares inversion method was developed to recover the Doppler shift and aerosol backscatter without requiring assumptions about the molecular component of the signal; (4) a study was done of the effects of systematic errors due to multiple etalon misalignment. It was discovered that even for small offsets and high aerosol loadings, the wind determination can be biased by as much as 1 m/s. The forward model and inversion process were modified to account for this effect; and (5) the lidar measurements were validated using rawinsonde balloon measurements. The measurements were found to be in agreement within 1-2 m/s.

  8. Adaptive spectral doppler estimation.

    PubMed

    Gran, Fredrik; Jakobsson, Andreas; Jensen, Jørgen Arendt

    2009-04-01

    In this paper, 2 adaptive spectral estimation techniques are analyzed for spectral Doppler ultrasound. The purpose is to minimize the observation window needed to estimate the spectrogram to provide a better temporal resolution and gain more flexibility when designing the data acquisition sequence. The methods can also provide better quality of the estimated power spectral density (PSD) of the blood signal. Adaptive spectral estimation techniques are known to provide good spectral resolution and contrast even when the observation window is very short. The 2 adaptive techniques are tested and compared with the averaged periodogram (Welch's method). The blood power spectral capon (BPC) method is based on a standard minimum variance technique adapted to account for both averaging over slow-time and depth. The blood amplitude and phase estimation technique (BAPES) is based on finding a set of matched filters (one for each velocity component of interest) and filtering the blood process over slow-time and averaging over depth to find the PSD. The methods are tested using various experiments and simulations. First, controlled flow-rig experiments with steady laminar flow are carried out. Simulations in Field II for pulsating flow resembling the femoral artery are also analyzed. The simulations are followed by in vivo measurement on the common carotid artery. In all simulations and experiments it was concluded that the adaptive methods display superior performance for short observation windows compared with the averaged periodogram. Computational costs and implementation details are also discussed.

  9. High Resolution Doppler Imager

    NASA Technical Reports Server (NTRS)

    Hays, Paul B.

    1999-01-01

    This report summarizes the accomplishments of the High Resolution Doppler Imager (HRDI) on UARS spacecraft during the period 4/l/96 - 3/31/99. During this period, HRDI operation, data processing, and data analysis continued, and there was a high level of vitality in the HRDI project. The HRDI has been collecting data from the stratosphere, mesosphere, and lower thermosphere since instrument activation on October 1, 1991. The HRDI team has stressed three areas since operations commenced: 1) operation of the instrument in a manner which maximizes the quality and versatility of the collected data; 2) algorithm development and validation to produce a high-quality data product; and 3) scientific studies, primarily of the dynamics of the middle atmosphere. There has been no significant degradation in the HRDI instrument since operations began nearly 8 years ago. HRDI operations are fairly routine, although we have continued to look for ways to improve the quality of the scientific product, either by improving existing modes, or by designing new ones. The HRDI instrument has been programmed to collect data for new scientific studies, such as measurements of fluorescence from plants, measuring cloud top heights, and lower atmosphere H2O.

  10. Extended dynamic range of Doppler OCT by application of a new method to high density B-scans using a MHz FDML swept laser source (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Elahi, Sahar; Thrane, Lars; Rollins, Andrew M.; Jenkins, Michael W.

    2017-02-01

    The limited dynamic range of optical coherence tomography (OCT) Doppler velocity measurements makes it difficult to conduct experiments on samples requiring a large dynamic range without phase wrapping at high velocities or loss of sensitivity at slow velocities. Hemodynamics and wall motion undergo significant increases in velocity as the embryonic heart develops. Experimental studies indicate that altered hemodynamics in early-stage embryonic hearts can lead to congenital heart diseases (CHDs), motivating close monitoring of blood flow over several stages of development. We have built a high-speed OCT system using an FDML laser (Optores GmbH, Germany) at a sweep rate of 1.68 MHz (axial resolution - 12 μm, sensitivity - 105 dB, phase stability - 17 mrad). The speed of this OCT system allows us to acquire high-density B-scans to obtain an extended velocity dynamic range without sacrificing the frame rate (100 Hz). The extended dynamic range within a frame is achieved by varying the A-scan interval at which the phase difference is found, enabling detection of velocities ranging from tens of microns per second to hundreds of millimeters per second. The extra lines in a frame can also be utilized to improve the structural and Doppler images via complex averaging. In structural images where the presence of blood causes additional scattering, complex averaging helps retrieve features located deeper in the tissue. Moreover, high-density frames can be registered to 4D volumes to determine the orthogonal direction of flow for calculating shear stress as well as estimating the cardiac output. In conclusion, high density B-scans acquired by our high-speed OCT system enable image enhancement and direct measurement of biological parameters in cohort studies.

  11. Development of a Coherent Lidar for Aiding Precision Soft Landing on Planetary Bodies

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Pierrottet, Diego; Tolson, Robert H.; Powell, Richard W.; Davidson, John B.; Peri, Frank

    2005-01-01

    Coherent lidar can play a critical role in future planetary exploration missions by providing key guidance, navigation, and control (GNC) data necessary for navigating planetary landers to the pre-selected site and achieving autonomous safe soft-landing. Although the landing accuracy has steadily improved over time to approximately 35 km for the recent Mars Exploration Rovers due to better approach navigation, a drastically different guidance, navigation and control concept is required to meet future mission requirements. For example, future rovers will require better than 6 km landing accuracy for Mars and better than 1 km for the Moon plus maneuvering capability to avoid hazardous terrain features. For this purpose, an all-fiber coherent lidar is being developed to address the call for advancement of entry, descent, and landing technologies. This lidar will be capable of providing precision range to the ground and approach velocity data, and in the case of landing on Mars, it will also measure the atmospheric wind and density. The lidar obtains high resolution range information from a frequency modulated-continuous wave (FM-CW) laser beam whose instantaneous frequency varies linearly with time, and the ground vector velocity is directly extracted from the Doppler frequency shift. Utilizing the high concentration of aerosols in the Mars atmosphere (approx. two order of magnitude higher than the Earth), the lidar can measure wind velocity with a few watts of optical power. Operating in 1.57 micron wavelength regime, the lidar can use the differential absorption (DIAL) technique to measure the average CO2 concentration along the laser beam using, that is directly proportional to the Martian atmospheric density. Employing fiber optics components allows for the lidar multi-functional operation while facilitating a highly efficient, compact and reliable design suitable for integration into a spacecraft with limited mass, size, and power resources.

  12. A symmetrical laser Doppler velocity meter and its application to turbulence characterization

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.

    1972-01-01

    A symmetrical method of optical heterodyning of the Doppler shifted scattered laser radiation developed for velocity measurements with a minimal instrumental spectral broadening and a high signal-to-noise ratio. The method employs two laser beams incident on the moving scatterer and does not use any reference beam for heterodyning. The Doppler signal frequency is independent of the scattering angle and the signal possesses no receiving aperture broadening. Optical alignment is simple. Typical values of the instrumental spectral broadening were approximately 0.8 percent of the center frequency of the Doppler signal, and the signal-to-noise ratio was approximately 25 dB, obtained from an air flow system using submicron dioctylphthalate scattering aerosol. Experimental and theoretical studies were made on the characteristics of the Doppler signal and the effect of system parameters in turbulent flow measurement. The optimization process involved in the beam optics and in the use of a spatial filter is described. For localized flow measurement in any direction of the three-dimensional orthogonal coordinates, the system, using uncorrected optical components, had a sensing volume which can be described by a sensitive length of 600 microns and a diameter of 100 microns.

  13. Three-photon coherence of Rydberg atomic states

    NASA Astrophysics Data System (ADS)

    Kwak, Hyo Min; Jeong, Taek; Lee, Yoon-Seok; Moon, Han Seb

    2016-05-01

    We investigated three-photon coherence effects of the Rydberg state in a four-level ladder-type atomic system for the 5 S1/2 (F = 3) - 5 P3/2 (F' = 4) - 50 D5/2 - 51 P3/2 transition of 85 Rb atoms. By adding a resonant electric field of microwave (MW) at electromagnetically induced transparency (EIT) in Rydberg state scheme, we observed experimentally that splitting of EIT signal appears under the condition of three-photon resonance in the Doppler-broadened atomic system. Discriminating the two- and three-photon coherence terms from the calculated spectrum in a simple four-level ladder-type Doppler-broadened atomic system, we found that the physical origin of splitting of EIT was three-photon coherence effect, but not three-photon quantum interference phenomena such as three-photon electromagnetically induced absorption (TPEIA).

  14. Coherent spontaneous radiation from highly bunched electron beams

    SciTech Connect

    Berryman, K.W.; Crosson, E.R.; Ricci, K.N.

    1995-12-31

    Coherent spontaneous radiation has now been observed in several FELs, and is a subject of great importance to the design of self-amplified spontaneous emission (SASE) devices. We report observations of coherent spontaneous radiation in both FIREFLY and the mid-infrared FEL at the Stanford Picosecond FEL Center. Coherent emission has been observed at wavelengths as short as 5 microns, and enhancement over incoherent levels by as much as a factor of 4x10{sup 4} has been observed at longer wavelengths. The latter behavior was observed at 45 microns in FIREFLY with short bunches produced by off-peak acceleration and dispersive compression. We present temporal measurements of the highly bunched electron distributions responsible for the large enhancements, using both transition radiation and energy-phase techniques.

  15. Doppler OCT imaging of cytoplasm shuttle flow in Physarum polycephalum.

    PubMed

    Bykov, Alexander V; Priezzhev, Alexander V; Lauri, Janne; Myllylä, Risto

    2009-09-01

    The Doppler optical coherence tomography technique was applied to image the oscillatory dynamics of protoplasm in the strands of the plasmodium of slime mould Physarum polycephalum. Radial contractions of the gel-like walls of the strands and the velocity distributions in the sol-like endoplasm streaming along the plasmodial strands are imaged. The motility inhibitor effect of carbon dioxide on the cytoplasm shuttle flow and strand-wall contraction is shown. The optical attenuation coefficient of cytoplasm is estimated. 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  16. Novel Tests of Gravity Below Fifty Microns

    NASA Astrophysics Data System (ADS)

    Martinez, Gabriela; Johnson, Jeremy; Guerrero, Ian; Hoyle, C. D.

    2016-03-01

    Due to inconsistencies between General Relativity and the Standard Model, tests of gravity remain at the forefront of experimental physics. At Humboldt State University, undergraduates and faculty are designing an experiment sensitive enough to detect gravitational interactions below the 50 micron scale. The experiment measures the twist of a torsion pendulum as an attractor mass is oscillated nearby in a parallel plate configuration, providing time varying gravitational torque on the pendulum. The size and distance dependence of the torque variation will provide a means to determine any deviation from current models of gravity on untested scales. Supported by NSF Grants 1065697 and 1306783.

  17. Can blood flow in separate small tubes be quantitatively assessed by high-resolution laser Doppler imaging?

    PubMed

    Lindén, M

    1997-11-01

    A method is suggested for quantitative flow assessment of whole-blood perfusing tubes with diameters in the range from 500 microns to 1.5 mm, for velocities below 9 mm s-1. The algorithm is based both on the Doppler broadening of backscattered laser light and the magnitude of the diameter of the perfused tube. A bandwidth-modified high-resolution laser Doppler perfusion imaging system is used to record the Doppler broadening. A flow model, consisting of a linearly narrowing tube (inner diameter 620-1330 microns), is connected to a precision infusion pump and perfused by human whole blood of volume flows ranging from 0 to 6.6 mm3 s-1. Empirical data are fitted into a regression model, and the parameters of the algorithm can be determined, resulting in a correlation coefficient of 0.975 between the predicted and true volume flows. Using this algorithm, volume flows in tubes of inner diameters of 500 microns, 750 microns and 1.4 mm are predicted, with accuracies corresponding to correlation coefficients of 0.994, 0.993 and 0.996.

  18. 3-D Ultrafast Doppler Imaging Applied to the Noninvasive and Quantitative Imaging of Blood Vessels in Vivo

    PubMed Central

    Provost, J.; Papadacci, C.; Demene, C.; Gennisson, J-L.; Tanter, M.; Pernot, M.

    2016-01-01

    Ultrafast Doppler Imaging was introduced as a technique to quantify blood flow in an entire 2-D field of view, expanding the field of application of ultrasound imaging to the highly sensitive anatomical and functional mapping of blood vessels. We have recently developed 3-D Ultrafast Ultrasound Imaging, a technique that can produce thousands of ultrasound volumes per second, based on three-dimensional plane and diverging wave emissions, and demonstrated its clinical feasibility in human subjects in vivo. In this study, we show that non-invasive 3-D Ultrafast Power Doppler, Pulsed Doppler, and Color Doppler Imaging can be used to perform quantitative imaging of blood vessels in humans when using coherent compounding of three-dimensional tilted plane waves. A customized, programmable, 1024-channel ultrasound system was designed to perform 3-D Ultrafast Imaging. Using a 32X32, 3-MHz matrix phased array (Vermon, France), volumes were beamformed by coherently compounding successive tilted plane wave emissions. Doppler processing was then applied in a voxel-wise fashion. 3-D Ultrafast Power Doppler Imaging was first validated by imaging Tygon tubes of varying diameter and its in vivo feasibility was demonstrated by imaging small vessels in the human thyroid. Simultaneous 3-D Color and Pulsed Doppler Imaging using compounded emissions were also applied in the carotid artery and the jugular vein in one healthy volunteer. PMID:26276956

  19. Revealing Hidden Coherence in Partially Coherent Light.

    PubMed

    Svozilík, Jiří; Vallés, Adam; Peřina, Jan; Torres, Juan P

    2015-11-27

    Coherence and correlations represent two related properties of a compound system. The system can be, for instance, the polarization of a photon, which forms part of a polarization-entangled two-photon state, or the spatial shape of a coherent beam, where each spatial mode bears different polarizations. Whereas a local unitary transformation of the system does not affect its coherence, global unitary transformations modifying both the system and its surroundings can enhance its coherence, transforming mutual correlations into coherence. The question naturally arises of what is the best measure that quantifies the correlations that can be turned into coherence, and how much coherence can be extracted. We answer both questions, and illustrate its application for some typical simple systems, with the aim at illuminating the general concept of enhancing coherence by modifying correlations.

  20. Revealing Hidden Coherence in Partially Coherent Light

    NASA Astrophysics Data System (ADS)

    Svozilík, Jiří; Vallés, Adam; Peřina, Jan; Torres, Juan P.

    2015-11-01

    Coherence and correlations represent two related properties of a compound system. The system can be, for instance, the polarization of a photon, which forms part of a polarization-entangled two-photon state, or the spatial shape of a coherent beam, where each spatial mode bears different polarizations. Whereas a local unitary transformation of the system does not affect its coherence, global unitary transformations modifying both the system and its surroundings can enhance its coherence, transforming mutual correlations into coherence. The question naturally arises of what is the best measure that quantifies the correlations that can be turned into coherence, and how much coherence can be extracted. We answer both questions, and illustrate its application for some typical simple systems, with the aim at illuminating the general concept of enhancing coherence by modifying correlations.

  1. The 1.2 micron CMOS technology

    NASA Technical Reports Server (NTRS)

    Pina, C. A.

    1985-01-01

    A set of test structures was designed using the Jet Propulsion Laboratory (JPL) test chip assembler and was used to evaluate the first CMOS-bulk foundry runs with feature sizes of 1.2 microns. In addition to the problems associated with the physical scaling of the structures, this geometry provided an additional set of problems, since the design files had to be generated in such a way as to be capable of being processed through p-well, n-well, and twin-well processing lines. This requirement meant that the files containing the geometric design rules as well as the structure design files had to produce process-insensitive designs, a requirement that does not apply to the more mature 3.0-micron CMOS feature size technology. Because of the photolithographic steps required with this feature size, the maximum allowable chip size was 10 x 10 mm, and this chip was divided into 24 project areas, with each area being 1.6 x 1.6 mm in size. The JPL-designed structures occupied 13 out of the 21 allowable project sizes and provided the only test information obtained from these three preliminary runs. The structures were used to successfully evaluate three different manufacturing runs through two separate foundries.

  2. The Two Micron All Sky Survey

    NASA Technical Reports Server (NTRS)

    Kleinmann, S. G.; Lysaght, M. G.; Pughe, W. L.; Schneider, S. E.; Skrutskie, M. F.; Weinberg, M. D.; Price, S. D.; Matthews, K.; Soifer, B. T.; Huchra, J. P.

    1994-01-01

    The Two Micron All Sky Survey (2MASS) will provide a uniform survey of the entire sky at three near-infrared wavebands: J(lambda(sub eff) = 1.25 micrometers), H(lambda(sub eff) = 1.65 micrometers), and K(sub s)(lambda(sub eff) = 2.16 micrometers). A major goal of the survey is to probe large scale structures in the Milky Way and in the Local Universe, exploiting the relatively high transparency of the interstellar medium in the near-infrared, and the high near-infrared luminosities of evolved low- and intermediate-mass stars. A sensitive overview of the near-infrared sky is also an essential next step to maximize the gains achievable with infrared array technology. Our assessment of the astrophysical questions that might be addressed with these new arrays is currently limited by the very bright flux limit of the only preceding large scale near-infrared sky survey, the Two Micron Sky Survey carried out at Caltech in the late 1960's. Near-infrared instruments based on the new array technology have already obtained spectra of objects 1 million times fainter than the limit of the TMSS! This paper summarizes the essential parameters of the 2MASS project and the rationale behind those choices, and gives an overview of results obtained with a prototype camera that has been in operation since May 1992. We conclude with a list of expected data products and a statement of the data release policy.

  3. Research on Doppler frequency in incoherent FM/CW laser detection

    NASA Astrophysics Data System (ADS)

    Liu, Kai; Cui, Zhanzhong

    2010-10-01

    The principle of transmitted and received laser in incoherent FM/CW laser detection is different from the one in coherent FM/CW laser detection. The methods for distance solution in both detections are similar. Incoherent FM/CW laser detection uses subcarrier to modulate the intensity of laser, and the photodetector detects the intensity of received signal. The amplified photocurrent is mixed with local oscillator signal, and the intermediate frequency (IF) signal contains the information of distance from sensor to target. The Doppler frequency for this detection is related with the relative radial velocity between sensor and target. The optical frequency is directly modulated with electro-optic device in coherent FM/CW laser detection and the received laser signal is photomixed with transmitted laser signal. The Doppler frequency in the detection relates to the optical frequency. In distance-measuring lidar, the Doppler frequency affects the solution. The Doppler frequency in incoherent FM/CW laser detection is unrelated with optical frequency, and it is much less than the one in coherent FM/CW laser detection, correspondingly. The error in incoherent FM/CW laser detection is smaller. As a result, the incoherent FM/CW laser detection is more suitable for the use of distance-measuring lidar.

  4. SPARCLE: Validation of Observing System Simulations (SPace Readiness Coherent Lidar Experiment)

    NASA Technical Reports Server (NTRS)

    Emmitt, G. D.; Miller, Timothy L.

    1998-01-01

    NASA recently approved a mission to fly a Doppler Wind Lidar (DWL) on a U.S. Space Shuttle. SPARCLE, managed by Marshall Space Flight Center in Huntsville, AL, is targeted for launch in March 2001. This mission is viewed as a necessary demonstration of a solid state (2 micron) lidar using coherent detection before committing resources to a 3-5 year research or operational mission. While, to many, this shuttle mission is seen as the first step in a series leading to a fully operational wind observing system, to others, it is a chance to validate predictions of performance based upon theoretical models, analyses of airborne and ground-based data, and sophisticated observing system simulation experiments. This paper will be presented in two parts: first a brief overview of the SPARCLE mission and second, a summary of current performance predictions and key contributions from ground- based and airborne DWL research. The SPARCLE instrument is a 100 mJ, 6 Hz, diode-pumped 2-micron laser with a .25 m telescope using heterodyne mixing in a fiber and an InGaAs detector. A 25 cm silicon wedge scanner will be used in step-stare modes with dwells ranging from 60 seconds to .5 seconds. Pointing knowledge is achieved with a dedicated GPS/INS mounted close to the lidar. NASA's Hitchhiker program is providing the instrument enclosures (2 cans) and mission logistics support. An on-board data system is sized to record 150 Gbytes of raw signal from a two 400 MHZ A/D converters. On-board signal processing will be used to control the frequency of the Local Oscillator. SPARCLE is predicted to have a single shot backscatter sensitivity near 1x10(exp -6) m-1 sr-1, To achieve higher sensitivity, shot accumulation will be employed. Ground-based, 2 micron DWLs have been used to assess the benefits of shot accumulation (approximately SQRT for SNR). Airborne programs like MACAWS have provided good datasets for evaluating various sampling strategies and signal processing algorithms. Using these

  5. Real time endoscopic and functional imaging of biological ultrastructure using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Rollins, Andrew Martin

    2000-10-01

    Optical coherence tomography (OCT) is a relatively new, non-invasive optical imaging technique. OCT is well suited to in situ imaging of biological ultrastructure, providing micron-scale resolution in three dimensions to a depth of a few millimeters without contacting the tissue. The objective of this research was to advance the state of the art in OCT imaging in order to enable endoscopic examination of gastrointestinal mucosae, and to explore functional imaging extensions to the technology. We present a high speed OCT system capable of imaging in real time. Issues critical to real time OCT imaging are discussed, with an emphasis on rapid scanning optical delay lines, and real time signal conditioning, acquisition, and display instrumentation. Results of experiments demonstrating real time OCT imaging are presented, including in vivo samples. The real time OCT system was integrated with a custom catheter probe in a prototype endoscopic OCT (EOCT) unit appropriate for clinical studies. We report on the design and initial clinical experience with the real-time EOCT imaging system. Results of initial clinical studies are presented. EOCT imaging clearly delineates the substructure of the mucosa and submucosa in several gastrointestinal organs. Color Doppler optical coherence tomography (CDOCT) is a functional extension of OCT that can image flow in turbid media with micron-scale spatial resolution. We present a real-time CDOCT system that is capable of imaging flow at high frame rates. Imaging of flow in tissue simulating phantom and in vivo in an animal model is demonstrated. Further, we introduce a family of power-conserving fiber- optic interferometer designs for OCT. Simple design equations for optimization of the signal to noise ratio of the interferometers are expressed in terms of relevant signal and noise sources and measurable system parameters. Finally, we discuss a number of future directions for OCT research. The spectroscopic OCT techniques of wavelength

  6. Computer aided diagnosis system for breast cancer based on color Doppler flow imaging.

    PubMed

    Liu, Yan; Cheng, H D; Huang, J H; Zhang, Y T; Tang, X L; Tian, J W; Wang, Y

    2012-12-01

    Color Doppler flow imaging takes a great value in diagnosing and classifying benign and malignant breast lesions. However, scanning of color Doppler sonography is operator-dependent and ineffective. In this paper, a novel breast classification system based on B-Mode ultrasound and color Doppler flow imaging is proposed. First, different feature extraction methods were used to obtain the texture and geometric features from B-Mode ultrasound images. In color Doppler feature extraction stage, several spectrum features are extracted by applying blood flow velocity analysis to Doppler signals. Moreover, a velocity coherent vector method is proposed based on color coherence vector, which is helpful for designing to the optimize detection of flow indices from different blood flow velocity fields automatically. Finally, a support vector machine classifier with selected feature vectors is used to classify breast tumors into benign and malignant. The experimental results demonstrate that the proposed computer-aided diagnosis system is useful for reducing the unnecessary biopsy and death rate.

  7. Planetary Doppler Imaging

    NASA Astrophysics Data System (ADS)

    Murphy, N.; Jefferies, S.; Hart, M.; Hubbard, W. B.; Showman, A. P.; Hernandez, G.; Rudd, L.

    2014-12-01

    Determining the internal structure of the solar system's gas and ice giant planets is key to understanding their formation and evolution (Hubbard et al., 1999, 2002, Guillot 2005), and in turn the formation and evolution of the solar system. While internal structure can be constrained theoretically, measurements of internal density distributions are needed to uncover the details of the deep interior where significant ambiguities exist. To date the interiors of giant planets have been probed by measuring gravitational moments using spacecraft passing close to, or in orbit around the planet. Gravity measurements are effective in determining structure in the outer envelope of a planet, and also probing dynamics (e.g. the Cassini and Juno missions), but are less effective in probing deep structure or the presence of discrete boundaries. A promising technique for overcoming this limitation is planetary seismology (analogous to helioseismology in the solar case), postulated by Vorontsov, 1976. Using trapped pressure waves to probe giant planet interiors allows insight into the density and temperature distribution (via the sound speed) down to the planetary core, and is also sensitive to sharp boundaries, for example at the molecular to metallic hydrogen transition or at the core-envelope interface. Detecting such boundaries is not only important in understanding the overall structure of the planet, but also has implications for our understanding of the basic properties of matter at extreme pressures. Recent Doppler measurements of Jupiter by Gaulme et al (2011) claimed a promising detection of trapped oscillations, while Hedman and Nicholson (2013) have shown that trapped waves in Saturn cause detectable perturbations in Saturn's C ring. Both these papers have fueled interest in using seismology as a tool for studying the solar system's giant planets. To fully exploit planetary seismology as a tool for understanding giant planet structure, measurements need to be made

  8. Coherent catastrophism

    NASA Astrophysics Data System (ADS)

    Asher, D. J.; Clube, S. V. M.; Napier, W. M.; Steel, D. I.

    We review the theoretical and observational evidence that, on timescales relevant to mankind, the prime collision hazard is posed by temporally correlated impacts (coherent catastrophism, Δt ˜ 10 2-10 4 yr) rather than random ones (stochastic catastrophism, Δt ˜ 10 5-10 8 yr). The mechanism whereby coherent incursions into and through the terrestrial atmosphere occur is described as being the result of giant cometary bodies arriving in orbits with perihelia in the inner solar system. Hierarchical fragmentation of such large (100 km-plus) bodies — due to thermal stresses near perihelion, collisions in the asteroid belt, or passages through the Jovian Roche radius — results in numerous ˜kilometre-sized objects being left in short-period orbits, and appearing in telescopic searches as Apollo-type asteroids. Many more smaller objects, in the 10-100 metre size range and only recently observed, by the Spacewatch team, are expected to be in replenished clusters in particular orbits as a result of continuing disintegrations of large, differentiated, cometary objects. Gravitational perturbations by Jupiter bring these clusters around to have a node at 1 AU in a cyclic fashion, leading to impacts at certain times of year every few years during active periods lasting a few centuries, such periods being separated by intervals of a few millennia. Furthermore, fragmentations within the hierarchy result in significant bombardment commensurabilities ( Δt ˜ 10-10 2 yr) during active periods occurring at random intervals ( Δt ˜ 10 2-10 3 yr). It appears that the Earth has been subject to such impacts since the break-up of such a comet ˜2×10 4 years ago; currently we are not passing through a high-risk epoch, although some phenomena originating in the products of this break-up have been observed in the 20th century. This most recent hierarchical disintegration, associated with four well-known meteor showers and termed the Taurid Complex, is now recognized as resulting

  9. Proposal to Simultaneously Profile Wind and CO2 on Earth and Mars With 2-micron Pulsed Lidar Technologies

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Koch, Grady J.; Kavaya, Michael J.; Amzajerdian, Farzin; Ismail, Syed; Emmitt, David

    2005-01-01

    2-micron lidar technology has been in use and under continued improvement for many years toward wind measurements. But the 2-micron wavelength region is also rich in absorption lines of CO2 (and H2O to a lesser extent) that can be exploited with the differential absorption lidar (DIAL) technique to make species concentration measurements. A coherent detection receiver offers the possibility of making combined wind and DIAL measurements with wind derived from frequency shift of the backscatter spectrum and species concentration derived from power of the backscatter spectrum. A combined wind and CO2 measurement capability is of interest for applications on both Earth and Mars. CO2 measurements in the Earth atmosphere are of importance to studies of the global carbon cycle. Data on vertically-resolved CO2 profiles over large geographical observations areas are of particular interest that could potentially be made by deploying a lidar on an aircraft or satellite. By combining CO2 concentration with wind measurements an even more useful data product could be obtained in the calculation of CO2 flux. A challenge to lidar in this application is that CO2 concentration measurements must be made with a high level of precision and accuracy to better than 1%. The Martian atmosphere also presents wind and CO2 measurement problems that could be met with a combined DIAL/Doppler lidar. CO2 concentration in this scenario would be used to calculate atmospheric density since the Martian atmosphere is composed of 95% CO2. The lack of measurements of Mars atmospheric density in the 30-60 km range, dust storm formation and movements, and horizontal wind patterns in the 0-20 km range pose significant risks to aerocapture, and entry, descent, and landing of future robotic and human Mars missions. Systematic measurement of the Mars atmospheric density and winds will be required over several Mars years, supplemented with day-of-entry operational measurements. To date, there have been 5

  10. Proposal to Simultaneously Profile Wind and CO2 on Earth and Mars With 2-micron Pulsed Lidar Technologies

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Koch, Grady J.; Kavaya, Michael J.; Amzajerdian, Farzin; Ismail, Syed; Emmitt, David

    2005-01-01

    2-micron lidar technology has been in use and under continued improvement for many years toward wind measurements. But the 2-micron wavelength region is also rich in absorption lines of CO2 (and H2O to a lesser extent) that can be exploited with the differential absorption lidar (DIAL) technique to make species concentration measurements. A coherent detection receiver offers the possibility of making combined wind and DIAL measurements with wind derived from frequency shift of the backscatter spectrum and species concentration derived from power of the backscatter spectrum. A combined wind and CO2 measurement capability is of interest for applications on both Earth and Mars. CO2 measurements in the Earth atmosphere are of importance to studies of the global carbon cycle. Data on vertically-resolved CO2 profiles over large geographical observations areas are of particular interest that could potentially be made by deploying a lidar on an aircraft or satellite. By combining CO2 concentration with wind measurements an even more useful data product could be obtained in the calculation of CO2 flux. A challenge to lidar in this application is that CO2 concentration measurements must be made with a high level of precision and accuracy to better than 1%. The Martian atmosphere also presents wind and CO2 measurement problems that could be met with a combined DIAL/Doppler lidar. CO2 concentration in this scenario would be used to calculate atmospheric density since the Martian atmosphere is composed of 95% CO2. The lack of measurements of Mars atmospheric density in the 30-60 km range, dust storm formation and movements, and horizontal wind patterns in the 0-20 km range pose significant risks to aerocapture, and entry, descent, and landing of future robotic and human Mars missions. Systematic measurement of the Mars atmospheric density and winds will be required over several Mars years, supplemented with day-of-entry operational measurements. To date, there have been 5

  11. New MBE buffer for micron- and quarter-micron-gateGaAs MESFETs

    NASA Technical Reports Server (NTRS)

    1988-01-01

    A new buffer layer has been developed that eliminates backgating in GaAs MESFETs and substantially reduces short-channel effects in GaAs MESFETs with 0.27-micron-long gates. The new buffer is grown by molecular beam epitaxy (MBE) at a substrate temperature of 200 C using Ga and As sub 4 beam fluxes. The buffer is crystalline, highly resistive, optically inactive, and can be overgrown with high quality GaAs. GaAs MESFETs with a gate length of 0.27 microns that incorporate the new buffer show improved dc and RF properties in comparison with a similar MESFET with a thin undoped GaAs buffer. To demonstrate the backgating performance improvement afforded by the new buffer, MESFETs were fabricated using a number of different buffer layers and structures. A schematic cross section of the MESFET structure used in this study is shown. The measured gate length, gate width, and source-drain spacing of this device are 2,98, and 5.5 microns, respectively. An ohmic contact, isolated from the MESFET by mesa etching, served as the sidegate. The MESFETs were fabricated in MBE n-GaAs layers grown on the new buffer and also in MBE n-GaAs layers grown on buffer layers of undoped GaAs, AlGaAs, and GaAs/AlGaAs superlattices. All the buffer layers were grown by MBE and are 2 microns thick. The active layer is doped to approximately 2 x 10 to the 17th/cu cm with silicon and is 0.3 microns thick.

  12. New MBE buffer for micron- and quarter-micron-gateGaAs MESFETs

    NASA Technical Reports Server (NTRS)

    1988-01-01

    A new buffer layer has been developed that eliminates backgating in GaAs MESFETs and substantially reduces short-channel effects in GaAs MESFETs with 0.27-micron-long gates. The new buffer is grown by molecular beam epitaxy (MBE) at a substrate temperature of 200 C using Ga and As sub 4 beam fluxes. The buffer is crystalline, highly resistive, optically inactive, and can be overgrown with high quality GaAs. GaAs MESFETs with a gate length of 0.27 microns that incorporate the new buffer show improved dc and RF properties in comparison with a similar MESFET with a thin undoped GaAs buffer. To demonstrate the backgating performance improvement afforded by the new buffer, MESFETs were fabricated using a number of different buffer layers and structures. A schematic cross section of the MESFET structure used in this study is shown. The measured gate length, gate width, and source-drain spacing of this device are 2,98, and 5.5 microns, respectively. An ohmic contact, isolated from the MESFET by mesa etching, served as the sidegate. The MESFETs were fabricated in MBE n-GaAs layers grown on the new buffer and also in MBE n-GaAs layers grown on buffer layers of undoped GaAs, AlGaAs, and GaAs/AlGaAs superlattices. All the buffer layers were grown by MBE and are 2 microns thick. The active layer is doped to approximately 2 x 10 to the 17th/cu cm with silicon and is 0.3 microns thick.

  13. Coherent lidar airborne windshear sensor - Performance evaluation

    NASA Technical Reports Server (NTRS)

    Targ, Russell; Kavaya, Michael J.; Huffaker, R. Milton; Bowles, Roland L.

    1991-01-01

    As part of the NASA/FAA National Integrated Windshear Program, a measurable windshear hazard index has been defined that can be remotely sensed from an aircraft, to give the pilot information about the wind conditions along the flight path. A technology analysis and end-to-end performance simulation measuring signal-to-noise ratios and resulting wind velocity errors for competing coherent laser radar (lidar) systems have been carried out. The results show that a Ho:YAG lidar at a wavelength of 2.1 microns and a CO2 lidar at 10.6 microns can give the pilot information about the line-of-sight component of a windshear threat from his present position to a region extending 2-4 km in front of the aircraft. This constitutes a warning time of 20-40 s, even in conditions of moderately heavy precipitation.

  14. Coherent laser radar atmospheric turbulence sensor

    NASA Astrophysics Data System (ADS)

    Gatt, Philip; Frehlich, Rod G.; Hannon, Stephen M.

    1998-09-01

    A single-ended, range-resolved, refractive turbulence sensor concept was investigated for ground-based and airborne platforms. This technology is of interest to the Air Force's Airborne Laser (ABL) program, because it will enable the determination of optimal engagement paths for the weapons laser. In this paper we describe the performance of a range- resolved refractive turbulence profiler which is based upon a coherent laser radar array receiver technology. We present Monte-Carlo simulation performance predictions for several sensor configurations, including a one micron ABL sensor and an eye-safe two micron ground-based sensor. In addition to its refractive turbulence sensing function, this innovative sensor will be capable of measuring wind velocity and characterizing wind turbulence.

  15. Digital signal processor-based real-time optical Doppler tomography system.

    PubMed

    Yan, Shikui; Piao, Daqing; Chen, Yueli; Zhu, Quing

    2004-01-01

    We present a real-time data-processing and display unit based on a custom-designed digital signal processor (DSP) module for imaging tissue structure and Doppler blood flow. The DSP module is incorporated into a conventional optical coherence tomography system. We also demonstrate the flexibility of embedding advanced Doppler processing algorithms in the DSP module. Two advanced velocity estimation algorithms previously introduced by us are incorporated in this DSP module. Experiments on Intralipid flow demonstrate that a pulsatile flow of several hundred pulses per minute can be faithfully captured in M-scan mode by this DSP system. In vivo imaging of a rat's abdominal blood flow is also presented.

  16. Dispersive Doppler measurement of the electron content of the torus of Io

    NASA Technical Reports Server (NTRS)

    Levy, G. S.; Green, D. W.; Royden, H. N.; Wood, G. E.; Tyler, G. L.

    1981-01-01

    As Voyager 1 made its swing-by of Io, it passed through and behind the satellite's plasma torus. The phase paths of the coherent 13 cm and 3.6-cm wavelength signals transmitted from the spacecraft were shortened differentially by the plasma, resulting in the observation of a dispersive Doppler signature in the signals received at the NASA/Jet Propulsion Laboratory (deep space network) stations. Ray path integration through three different models of the electron distribution of the torus of Io (Warwick et al. 1979; Birmingham et al. 1981; Bagenal et al., 1981) have been performed. The results of the integrations are compared with the dispersive Doppler data.

  17. Prospects for detection of gravitational radiation by simultaneous Doppler tracking of several spacecraft

    NASA Technical Reports Server (NTRS)

    Estabrook, F. B.; Wahlquist, H. D.

    1978-01-01

    This paper reports a calculation of the effect of gravitational radiation on the observed Doppler shift of a sinusoidal electromagnetic signal transmitted to, and coherently transponded from, distant spacecraft. It is found that the effect of plane gravitational waves on such observations is not intuitively immediate, and in fact depends sensitively on the spacecraft direction, which suggests the possibility of detecting such plane waves by simultaneous Doppler tracking of several spacecraft. The need for broad band gravitational wave observations, the required stabilities of time keeping standards, and astrophysical sources expected in the Very Low Frequency band are briefly discussed.

  18. Differential Doppler as a diagnostic

    SciTech Connect

    Dzieciuch, M.; Munk, W. )

    1994-10-01

    Differential Doppler compression and travel time of individual peaks in the arrival sequence (relative to an overall average) are measured for the 5500-km acoustic transmissions from a moving source at Heard Island to Christmas (Crab) Island. The differentials cannot be explained by simple adiabatic propagation models. A hybrid theory, coupling polar and temperate models at the Antarctic Front can account for some of the qualitative features. Differential Doppler could be a useful tool for identifying ray arrivals. 10 refs., 11 figs., 3 tabs.

  19. Macular thickness measurements using Copernicus Spectral Domain Optical Coherence Tomography.

    PubMed

    Gella, Laxmi; Raman, Rajiv; Sharma, Tarun

    2015-01-01

    To provide normal macular thickness measurements using Spectral Domain Optical Coherence Tomography (SDOCT, Copernicus, Optopol Technologies, Zawierci, Poland). Fifty-eight eyes of 58 healthy subjects were included in this prospective study. All subjects had comprehensive ophthalmic examination including best-corrected visual acuity (BCVA). All the subjects underwent Copernicus SDOCT. Central foveal thickness (CFT) and photoreceptor layer (PRL) thickness were measured and expressed as mean and standard deviation. Mean retinal thickness for each of the 9 regions defined in the Early Treatment Diabetic Retinopathy Study was reported. The data were compared with published literature in Indians using Stratus and Spectralis OCTs to assess variation in instrument measurements. The mean CFT in the study sample was 173.8 ± 18.16 microns (131-215 microns) and the mean PRL thickness was 65.48 ± 4.23 microns (56-74 microns). No significant difference (p = 0.148) was found between CFT measured automated (179.28 ± 22 microns) and manually (173.83 ± 18.1 microns). CFT was significantly lower in women (167.62 ± 16.36 microns) compared to men (180.03 ± 18 microns) (p = 0.008). Mean retinal thickness reported in this study was significantly different from published literature using Stratus OCT and Spectralis OCT. We report the normal mean retinal thickness in central 1 mm area to be between 138 and 242 microns in Indian population using Copernicus SDOCT. We suggest that different OCT instruments cannot be used interchangeably for the measurement of macular thickness as they vary in segmentation algorithms.

  20. Radiation tolerant 1 micron CMOS technology

    NASA Astrophysics Data System (ADS)

    Crevel, P.; Rodde, K.

    1991-03-01

    Starting from a standard one micron Complementary Metal Oxide Semiconductor (CMOS) for high density, low power memory applications, the degree of radiation tolerance of the baseline process is evaluated. Implemented process modifications to improve latchup sensitivity under heavy ion irradiation as well as total dose effects without changing layout rules are described. By changing doping profiles in Metal Nitride Oxide Semiconductors (MNOS) and P-channel MOS (PMOS) device regions, it is possible to guarantee data sheet specification of a 64 K low power static RAM for total gamma dose up to 35 krad (Si) (and even higher values for the gate array family) without latch up for Linear Energy Transfer LET up to 115 MeV/(mg/cm squared).

  1. Novel Tests of Gravity Below Fifty Microns

    NASA Astrophysics Data System (ADS)

    Johnson, Jeremy; Martinez, Gabriela; Guerrero, Ian; Dunkley, Noah; Sanchez, Anthony; Isachsen, Hilde; Shaw, Duncan; Hoyle, C. D.

    2017-01-01

    Theories which attempt to unify the Standard Model and General Relativity often include features which violate the Weak Equivalence Principle (WEP) and gravitational Inverse-Square Law (ISL). A violation of either the WEP or ISL at any length scale would bring into question our fundamental understanding of gravity. Motivated by these considerations, undergraduates and faculty at Humboldt State University are building an experiment to probe gravitational interactions below the 50-micron length scale. The experiment employs a torsion pendulum with equal masses of different material arranged as a ``composition dipole.'' We measure the twist of the torsion pendulum as an attractor mass is oscillated nearby in a parallel-plate configuration, providing a time varying torque on the pendulum. The size and distance dependence of the torque variation will provide a means to determine any deviation from the WEP or ISL at untested scales. PHY-1065697, PHY-1306783, and PHY-1606988.

  2. 20-micron observations of Cassiopeia A

    NASA Astrophysics Data System (ADS)

    Greidanus, H.; Strom, R. G.

    1991-09-01

    Ground-based observations of a small region on the northern rim of Cas A showing structures down to the resolution limit of 5 sec are discussed. It is shown that the brightness distribution in the area has no correlation with the optical, radio, or X-ray emission. The radiating mass derived is found to be comparable to earlier infrared-based estimates, but substantially smaller than X-ray-derived values; this indicates a very low dust-to-gas ratio or coupling, or a very low filling factor for the hot gas. A detailed comparison between 20-micron and X-ray brightness distributions indicate that the dust is associated with the hottest gas found in the blast wave. This is found to be in contrast with its relative inward location near the cooler gas, that can be interpreted as reverse shocked ejecta.

  3. Micronized progesterone reduces vasoconstriction in the placenta.

    PubMed

    Miller, Nathaniel R; Dolinsky, Brad M; Napolitano, Peter G

    2015-09-01

    To investigate if micronized progesterone (P4) has the ability to attenuate thromboxane mimetic U46619-mediated fetoplacental artery vasoconstriction. Paired cotyledons obtained from the same placenta of five-term subjects were analyzed. The fetal artery and maternal intervillous space of one cotyledon was infused with P4 while another cotyledon was infused with control perfusate. After 30 min, a bolus dose of U44619 was administered to both cotyledons. The change in the measured fetoplacental vascular pressure caused by bolus administration of U46619 was less in the cotyledons infused with P4 (p = 0.009). Continuous treatment with P4 significantly attenuates the U46619-mediated fetoplacental vasoconstriction.

  4. Right Ventricular Tissue Doppler in Space Flight

    NASA Technical Reports Server (NTRS)

    Garcia, Kathleen M.; Hamilton, Douglas R.; Sargsyan, Ashot E.; Ebert, Douglas; Martin, David S.; Barratt, Michael R.; Martin, David S.; Bogomolov, Valery V.; Dulchavsky, Scott A.; Duncan, J. Michael

    2010-01-01

    The presentation slides review normal physiology of the right ventricle in space, general physiology of the right ventricle; difficulties in imaging the heart in space, imaging methods, tissue Doppler spectrum, right ventricle tissue Doppler, and Rt Tei Index.

  5. Doppler Ultrasound: What Is It Used for?

    MedlinePlus

    ... in your neck (carotid artery stenosis) A Doppler ultrasound can estimate how fast blood flows by measuring the rate of change in its pitch (frequency). During a Doppler ultrasound, a technician trained in ultrasound imaging (sonographer) presses ...

  6. Signature stability in laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Iverson, Thomas Z.; Watson, Edward A.

    2017-05-01

    Speckle can complicate signal acquisition in coherent laser systems such as Laser Doppler Vibrometry (LDV). Variations in the speckle pattern at the reliever due to fluctuations in the system such as beam pointing can lead to impulsive events in the signature. The beam size at the object has a direct influence on the size of the speckle at the receiving aperture. Increasing the beam spot size reduces the average speckle size, but also decreases the strength of the signal coupled with the local oscillator in the LDV. In this paper, we derive the relationship between scattering spot size at the object and average speckle size at the receiver. Theory is presented on how increasing the beam diameter at the object can reduce the fluctuations of the heterodyned signal coupled with the Local Oscillator (LO). The Antenna theorem is presented to show the tradeoff between angular field of view and capture area. We show experimental results on the effects of speckle size and decreasing signal strength have on the stability of an LDV signature. We use a kurtosis metric previously reported in the literature to assess the stability and quality of the return signature.

  7. Reducing Spaceborne-Doppler-Radar Rainfall-Velocity Error

    NASA Technical Reports Server (NTRS)

    Tanelli, Simone; Im, Eastwood; Durden, Stephen L.

    2008-01-01

    A combined frequency-time (CFT) spectral moment estimation technique has been devised for calculating rainfall velocity from measurement data acquired by a nadir-looking spaceborne Doppler weather radar system. Prior spectral moment estimation techniques used for this purpose are based partly on the assumption that the radar resolution volume is uniformly filled with rainfall. The assumption is unrealistic in general but introduces negligible error in application to airborne radar systems. However, for spaceborne systems, the combination of this assumption and inhomogeneities in rainfall [denoted non-uniform beam filling (NUBF)] can result in velocity measurement errors of several meters per second. The present CFT spectral moment estimation technique includes coherent processing of a series of Doppler spectra generated in a standard manner from data over measurement volumes that are partially overlapping in the along-track direction. Performance simulation of this technique using high-resolution data from an airborne rain-mapping radar shows that a spaceborne Ku-band Doppler radar operating at signal-to-noise ratios greater than 10 dB can achieve root-mean-square accuracy between 0.5 and 0.6 m/s in vertical-velocity estimates.

  8. Understanding Doppler Broadening of Gamma Rays

    SciTech Connect

    Rawool-Sullivan, Mohini; Sullivan, John P.

    2014-07-03

    Doppler-broadened gamma ray peaks are observed routinely in the collection and analysis of gamma-ray spectra. If not recognized and understood, the appearance of Doppler broadening can complicate the interpretation of a spectrum and the correct identification of the gamma ray-emitting material. We have conducted a study using a simulation code to demonstrate how Doppler broadening arises and provide a real-world example in which Doppler broadening is found. This report describes that study and its results.

  9. Lunar multispectral imaging at 2.26 microns - First results

    NASA Technical Reports Server (NTRS)

    Davies, D. W.; Johnson, T. V.; Matson, D. L.

    1979-01-01

    The first results of line-scan imaging of the moon at 2.26 microns and 0.56 micron are presented. Among the many features observed in the 2.26 micron/0.56 micron ratio image, fresh rock and immature soils stand out as dark (i.e., low ratio) due to their infrared absorption bands. Also notable in this image are several strikingly bright (high 2.26 micron/0.56 micron ratio) areas which are likely to contain pyroclastic, glass-related materials. Some of these bright areas correspond to dark mantling material. Others (e.g., Sulpicius Gallus, Aristarchus Plateau) are distinctly different in their overall spectral reflectance and it is suggested that these localities contain varieties of pyroclastic glass-related materials which were not sampled by Apollo 17 but which are relatively abundant elsewhere on the moon.

  10. Evaluation of selected micronized poloxamers as tablet lubricants.

    PubMed

    Desai, D; Zia, H; Quadir, A

    2007-10-01

    The primary objective of this study was to compare the lubrication properties of micronized poloxamer 188 (Lmicrotrol micro 68) and micronized poloxamer 407 (Lmicrotrol micro 127) with certain conventional lubricants such as magnesium stearate and stearic acid. The secondary objective was to use these micronized poloxamers as water-soluble tablet lubricants in preparation of effervecsent tablets. The results showed that these micronized poloxamers have superior lubrication properties compared with stearic acid, with no negative effect on tablet hardness, friability, disintegration, or dissolution. Moreover, lubricant mixing time had no significant effect on tablet properties when poloxamers were used as lubricants. Effervescent tablets also were produced successfully using micronized poloxamers as lubricants. The micronized poloxamers had a better lubrication effect in comparison with that of water-soluble lubricant l-leucine.

  11. Slow light by coherent hole burnings

    NASA Astrophysics Data System (ADS)

    He, Qiong-Yi; Zhang, Bing; Wei, Xiao-Gang; Wu, Jin-Hui; Kuang, Shang-Qi; Gao, Jin-Yue

    2008-06-01

    We show that the simultaneous application of a copropagating saturating pump and a counterpropagating coherent beam can be used to burn a narrow spectral hole within the absorption line of the optical transition in a Doppler-broadened medium. The large index of refraction of this hole slows down a light pulse by a factor of about 104 . In addition, we propose a method to create two-color slow light pulses with simultaneous gain by employing a bichromatic field to saturate the medium.

  12. 3 micron spectrophotometry of Comet Halley - Evidence for water ice

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse D.; Tielens, A. G. G. M.; Witteborn, Fred C.; Rank, David M.; Wooden, Diane

    1988-01-01

    Structure has been observed in the 3-3.6 micron preperihelion spectrum of Comet Halley consistent with either an absorption band near 3.1 microns or emission near 3.3 microns. The results suggest that a large fraction of the water molecules lost by the comet are initially ejected in the form of small ice particles rather than in the gas phase.

  13. Doppler observations of solar rotation

    NASA Technical Reports Server (NTRS)

    Scherrer, P. H.; Wilcox, J. M.

    1980-01-01

    Daily observations of the photospheric equatorial rotation rate using the Doppler effect are made at the Stanford Solar Observatory. These observations show no variations in the rotation rate that exceed the observational error of about 1%. The average rotation rate is indistinguishable from that of sunspots and large-scale magnetic field structures.

  14. Doppler Imaging of EI Eridani

    NASA Astrophysics Data System (ADS)

    Washuettl, Albert; Strassmeier, Klaus G.; Collier-Cameron, Andrew

    We present Doppler images of the rapidly rotating active close binary star EI Eridani. Several Doppler images have been produced since 1984 making use of different versions of the Doppler imaging technique. They all show high-latitude spots surrounding or covering the rotational pole as well as some smaller spots on lower latitudes. The high-latitude/polar spot seems to be long-lived (at least a decade) but changes its shape on comparatively short timescales (of the order of one month). From time to time spots along the stellar equator also occur, but their lifetimes tend to be relatively short (weeks). Furthermore, long-term photometric observations revealed the existence of a magnetic cycle which has been estimated to be around 11 years. We also present time-resolved Doppler images from EI Eri obtained at McMath/NSO in fall 1996 during 70 consecutive nights. The final aim of this program is to investigate the spot evolution over the whole activity cycle.

  15. Doppler observations of solar rotation

    NASA Technical Reports Server (NTRS)

    Scherrer, P. H.

    1980-01-01

    Daily observations of the photospheric equatorial rotation rate using the Doppler effect mode at the Sanford Solar Observatory are presented. These observations show no variations in the rotation rate that exceed the observational error of about one percent. The average rotation rate is indistinguishable from that of sunspots and large scale magnetic field structures.

  16. Doppler observations of solar rotation

    NASA Technical Reports Server (NTRS)

    Scherrer, P. H.; Wilcox, J. M.

    1980-01-01

    Daily observations of the photospheric equatorial rotation rate using the Doppler effect are made at the Stanford Solar Observatory. These observations show no variations in the rotation rate that exceed the observational error of about 1%. The average rotation rate is indistinguishable from that of sunspots and large-scale magnetic field structures.

  17. The Doppler Effect--A New Approach

    ERIC Educational Resources Information Center

    Allen, J.

    1973-01-01

    Discusses the Doppler effect as it applies to different situations, such as a stationary source of sound with the observer moving, a stationary observer, and the sound source and observer both moving. Police radar, satellite surveillance radar, radar astronomy, and the Doppler navigator, are discussed as applications of Doppler shift. (JR)

  18. The Doppler Effect--A New Approach

    ERIC Educational Resources Information Center

    Allen, J.

    1973-01-01

    Discusses the Doppler effect as it applies to different situations, such as a stationary source of sound with the observer moving, a stationary observer, and the sound source and observer both moving. Police radar, satellite surveillance radar, radar astronomy, and the Doppler navigator, are discussed as applications of Doppler shift. (JR)

  19. Developments in optical coherence microscopy

    NASA Astrophysics Data System (ADS)

    Rolland, J. P.; Meemon, P.; Thompson, K. P.; Murali, S.; Lee, K. S.

    2010-11-01

    Optical Coherence Microscopy (OCM) utilizes a high NA microscope objective in the sample arm to achieve an axially and laterally high resolution OCT image. An increase in NA, however, leads to a dramatically decreased depth of focus (DOF), and hence shortens the imaging depth range so that high lateral resolution is maintained only within a small depth region around the focal plane. One solution to increase the depth of imaging while keeping a high lateral resolution is dynamic-focusing. Utilizing the voltage controlled refocus capability of a liquid lens, we have recently presented a solution for invariant high resolution imaging using the liquid lens embedded within a fixed optics hand-held custom microscope designed specifically for optical imaging systems using a broadband light source centered at 800 nm with a 120 nm bandwidth. Subsequently, we have developed a Gabor-Domain Optical Coherence Microscopy (GD-OCM) that utilizes the high speed imaging of spectral domain OCT, the high lateral resolution of OCM, and the ability of real time refocusing of our custom design variable focus objective. Finally, key developments in Phase-Resolved Doppler OCT (PR-DOCT) are key enablers to combine high-resolution structural imaging with functional imaging. In this paper we review achievements in GD-OCM and detail how portions of in-focus cross-sectional images can be extracted and fused to form an invariant lateral resolution image with multiple cross-sectional images acquired corresponding to a discrete refocusing step along depth enabled by the varifocal device. We demonstrate sub-cellular resolution imaging of an African frog tadpole (Xenopus Laevis) taken from a 500 μm × 500 μm cross-section as well as cellular imaging in in vivo skin. Finally, A novel dual-detection full-range Fourier-domain optical coherence tomography system was developed that provides 7 μm axial resolution (in air) at about 90 kHz axial scan rate for mirror-image phase resolved Doppler imaging

  20. Human polarimetric micro-doppler

    NASA Astrophysics Data System (ADS)

    Tahmoush, David; Silvious, Jerry

    2011-06-01

    Modern radars can pick up target motions other than just the principle target Doppler; they pick out the small micro-Doppler variations as well. These can be used to visually identify both the target type as well as the target activity. We model and measure some of the micro-Doppler motions that are amenable to polarimetric measurement. Understanding the capabilities and limitations of radar systems that utilize micro-Doppler to measure human characteristics is important for improving the effectiveness of these systems at securing areas. In security applications one would like to observe humans unobtrusively and without privacy issues, which make radar an effective approach. In this paper we focus on the characteristics of radar systems designed for the estimation of human motion for the determination of whether someone is loaded. Radar can be used to measure the direction, distance, and radial velocity of a walking person as a function of time. Detailed radar processing can reveal more characteristics of the walking human. The parts of the human body do not move with constant radial velocity; the small micro-Doppler signatures are timevarying and therefore analysis techniques can be used to obtain more characteristics. Looking for modulations of the radar return from arms, legs, and even body sway are being assessed by researchers. We analyze these techniques and focus on the improved performance that fully polarimetric radar techniques can add. We perform simulations and fully polarimetric measurements of the varying micro-Doppler signatures of humans as a function of elevation angle and azimuthal angle in order to try to optimize this type of system for the detection of arm motion, especially for the determination of whether someone is carrying something in their arms. The arm is often bent at the elbow, providing a surface similar to a dihedral. This is distinct from the more planar surfaces of the body and allows us to separate the signals from the arm (and

  1. Near 16 micron CO.sub.2 laser system

    DOEpatents

    Krupke, William F.

    1977-01-01

    Method and apparatus for inducing laser action in CO.sub.2 at a wavelength of 16 microns involving the transition between the 02.sup.0 0 and 01.sup.1 0 states. The population inversion between these two states is achieved by pumping to the 00.sup.0 1 level, suppressing the usual 10.6 micron transition to the 10.sup.0 0 level and encouraging the 9.6 micron transition, thereby populating the 02.sup.0 0 level, as the principal prerequisite for 16 micron laser action between the 02.sup.0 0 and 01.sup.1 0 levels.

  2. Roles of the 2 microns gene products in stable maintenance of the 2 microns plasmid of Saccharomyces cerevisiae.

    PubMed Central

    Reynolds, A E; Murray, A W; Szostak, J W

    1987-01-01

    We have examined the replication and segregation of the Saccharomyces cerevisiae 2 microns circle. The amplification of the plasmid at low copy numbers requires site-specific recombination between the 2 microns inverted repeat sequences catalyzed by the plasmid-encoded FLP gene. No other 2 microns gene products are required. The overexpression of FLP in a strain carrying endogenous 2 microns leads to uncontrolled plasmid replication, longer cell cycles, and cell death. Two different assays show that the level of Flp activity decreases with increasing 2 microns copy number. This regulation requires the products of the REP1 and REP2 genes. These gene products also act together to ensure that 2 microns molecules are randomly segregated between mother and daughter cells at cell division. Images PMID:3316982

  3. The coherent backscattering opposition effect

    NASA Technical Reports Server (NTRS)

    Nelson, R. M.; Hapke, B. W.; Smythe, W. D.; Gharakanian, V.; Herrera, P.

    1993-01-01

    We have measured the opposition effect, the nonlinear surge in reflectance seen in particulate materials as phase angle approaches zero degrees, in a suite of materials of varying particle size and reflectance. These samples were illuminated by linearly and circularly polarized monochromatic radiation at two wavelengths, 0.442 and 0.633 microns. By measuring the linear and circular polarization ratios for each sample, we have found that in highly reflective materials the behavior of the reflected radiation is consistent with the coherent backscattering process which has recently been proposed to explain the opposition surge that is seen in such media. The size and width of the coherent backscattering opposition peak vary as a function of reflectance of the sample. The opposition effect has been observed in particulate materials studied in the laboratory and it is also observed in the radiation reflected from solar system bodies which present a regolith to the earth based observer. The traditional explanation of the opposition effect, the shadow-hiding hypothesis, is that it was caused by the elimination of mutual shadows cast between the regolith grains as the phase angle of the observation became smaller. This shadow-hiding hypothesis, however, is unable to explain the opposition effect seen in highly reflective materials such as magnesium oxide and barium sulfate powders. This is because highly reflective media will multiply scatter the incident radiation between the regolith grains. This causes the shadows to be eliminated. We have measured the angular scattering properties of a suite of materials of different reflectivity. We have observed polarization ratios in reflective particulates that are consistent with coherent backscattering as the principal process which causes the opposition surge.

  4. Overlap junctions for high coherence superconducting qubits

    NASA Astrophysics Data System (ADS)

    Wu, X.; Long, J. L.; Ku, H. S.; Lake, R. E.; Bal, M.; Pappas, D. P.

    2017-07-01

    Fabrication of sub-micron Josephson junctions is demonstrated using standard processing techniques for high-coherence, superconducting qubits. These junctions are made in two separate lithography steps with normal-angle evaporation. Most significantly, this work demonstrates that it is possible to achieve high coherence with junctions formed on aluminum surfaces cleaned in situ by Ar plasma before junction oxidation. This method eliminates the angle-dependent shadow masks typically used for small junctions. Therefore, this is conducive to the implementation of typical methods for improving margins and yield using conventional CMOS processing. The current method uses electron-beam lithography and an additive process to define the top and bottom electrodes. Extension of this work to optical lithography and subtractive processes is discussed.

  5. Sub-micron geochronology by EPMA

    NASA Astrophysics Data System (ADS)

    Jercinovic, M. J.; Williams, M. L.; Berman, R.

    2013-12-01

    Actinide-bearing, geochronologically applicable accessory phases can exhibit remarkably complex internal compositional structures, commonly revealing polygenesis and allowing timing constraints to be placed on the structural and metamorphic evolution of multiply tectonized terrains. These fine-scale mineral domains have been revealed by high resolution compositional mapping by EPMA of natural monazite (LREE PO4), and can exist at nearly all spatial scales, including domains substantially below 1 micron in width. Accurate compositional characterization of such domains by any technique is difficult, but hardware and software developments in EPMA offer some opportunities to approach these challenging but important targets accurately. In this regard, we have analyzed Paloeproterozoic (ca. 1.8 Ga) monazite domains which penetrate along cleavage planes in larger, older monazite grains (ca. 2.55 and 2.37 Ga) from the Boothia peninsula, Nanavut Canada. As such, this represents a successful nanogeochronologic analysis. The direct analytical volume, as defined by the convolution of the error functions resulting from primary (beam) electron scattering and characteristic X-ray generation volume dimensions, can be restricted to considerably less than 1 micron with the use of high brightness sources (LaB6, CeB6, or Schottky) and modest beam energy (15kV or less) in monazite (Z ca. 39). However, the analysis is rendered far more complex by the effects of boundary fluorescence and beam damage. For this analysis, we use a high thermal/electrical conductivity double coating of aluminum and carbon to mitigate sample damage at high current density. Although imperfect (there remains a net loss of P relative to REEs and actinides), this analysis results in relatively minor counting errors relative to the concentrations, and accuracy can be further improved by use of time-dependent count acquisition methods. Reduction of the beam energy substantially below 10kV results in extreme damage

  6. Instrumentation of fiber-based functional optical coherence tomographic imaging system

    NASA Astrophysics Data System (ADS)

    Yu, Xiaofeng; Ding, Zhihua; Chen, Yuheng; Huang, Lina; Wu, Lan; Liu, Xu

    2005-01-01

    Optical coherence tomography (OCT) has been developed not only for morphological imaging, but also for functional imaging. By combining Doppler velocimetry with optical sectioning capability of OCT, we developed one branch of functional OCT (F-OCT) termed optical Doppler tomography (ODT). This newly developed fiber-based F-OCT system can provide structural image and Doppler image simultaneously, and is ready for extension to another branch of F-OCT termed as polarization-sensitive OCT (PS-OCT). Measurements of in vivo human skin and fresh milk flowing inside capillary tube are presented to demonstrate the capability of the developed system.

  7. Deformation Behavior of Sub-micron and Micron Sized Alumina Particles in Compression.

    SciTech Connect

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay; Mook, William; Boyce, Brad; Kotula, Paul Gabriel; McKenzie, Bonnie Beth; Bufford, Daniel Charles; Hall, Aaron Christopher.

    2014-09-01

    The ability to integrate ceramics with other materials has been limited due to high temperature (>800degC) ceramic processing. Recently, researchers demonstrated a novel process , aerosol deposition (AD), to fabricate ceramic films at room temperature (RT). In this process, sub - micro n sized ceramic particles are accelerated by pressurized gas, impacted on the substrate, plastically deformed, and form a dense film under vacuum. This AD process eliminates high temperature processing thereby enabling new coatings and device integration, in which ceramics can be deposited on metals, plastics, and glass. However, k nowledge in fundamental mechanisms for ceramic particle s to deform and form a dense ceramic film is still needed and is essential in advancing this novel RT technology. In this wo rk, a combination of experimentation and atomistic simulation was used to determine the deformation behavior of sub - micron sized ceramic particle s ; this is the first fundamental step needed to explain coating formation in the AD process . High purity, singl e crystal, alpha alumina particles with nominal size s of 0.3 um and 3.0 um were examined. Particle characterization, using transmission electron microscopy (TEM ), showed that the 0.3 u m particles were relatively defect - free single crystals whereas 3.0 u m p articles were highly defective single crystals or particles contained low angle grain boundaries. Sub - micron sized Al 2 O 3 particles exhibited ductile failure in compression. In situ compression experiments showed 0.3um particles deformed plastically, fractured, and became polycrystalline. Moreover, dislocation activit y was observed within the se particles during compression . These sub - micron sized Al 2 O 3 particles exhibited large accum ulated strain (2 - 3 times those of micron - sized particles) before first fracture. I n agreement with the findings from experimentation , a tomistic simulation s of nano - Al 2 O 3 particles showed dislocation slip and

  8. Multifrequency-swept optical coherence microscopy for highspeed full-field tomographic vibrometry in biological tissues

    PubMed Central

    Choi, Samuel; Sato, Keita; Ota, Takeru; Nin, Fumiaki; Muramatsu, Shogo; Hibino, Hiroshi

    2017-01-01

    Because conventional laser Doppler vibrometry or Doppler optical coherence tomography require mechanical scanning probes that cannot simultaneously measure the wide-range dynamics of bio-tissues, a multifrequency-swept optical coherence microscopy with wide-field heterodyne detection technique was developed. A 1024 × 1024 × 2000 voxel volume was acquired with an axial resolution of ~1.8 μm and an acquisition speed of 2 s. Vibration measurements at 10 kHz were performed over a wide field of view. Wide-field tomographic vibration measurements of a mouse tympanic membrane are demonstrated to illustrate the applicability of this method to live animals. PMID:28270971

  9. Amplitude-coded color doppler: clinical applications.

    PubMed

    Turetschek, K; Kollmann, C; Dorffner, R; Wunderbaldinger, P; Mostbeck, G

    1999-01-01

    Amplitude-coded color Doppler sonography (ACD) has become an useful adjunct to gray-scale US and conventional color Doppler sonography (CD) for the assessment of vascular diseases and pathologic conditions that might affect or alter tissue vascularization or perfusion. Basically, all US units that generate conventional color Doppler information through autocorrelation technique are capable of displaying ACD. This technique is also referred to as power Doppler, amplitude-mode color Doppler US, color Doppler energy (CDE), or US angiography. Amplitude-coded color Doppler sonography has already emerged as a valuable adjunct to conventional CD, particularly for evaluating flow in parts of the body where CD signal is weak because of slow flow, small blood vessels, or both.

  10. Doppler laser radar for range and speed measurement of road targets

    NASA Astrophysics Data System (ADS)

    Lin, Yanfang; Mao, Xuesong; Fang, Jianchao; Zhang, Tao

    2016-11-01

    A pulsed coherent vehicle laser radar system basing on the measurement of light flight time and Doppler frequency shift is demonstrated for the first time, which features a simple design that uses one photodiode (PD) as its optical detector. Pseudo random noise (PN) code is used for modulating the amplitude of transmitting light. Correlation function of the received echoes and the local modulating codes is calculated for measuring the light flight time. Due to PN code modulation, beat signal output from PD is piecewise continuous, which causes equidistant sampling of Doppler sine wave not feasible. In order that Doppler frequency be correctly measured by using fast Fourier transform (FFT), a simple signal amplitude modification method is derived from the definition of Fourier transform.

  11. Doppler cooling thermometry of a multilevel ion in the presence of micromotion

    NASA Astrophysics Data System (ADS)

    Sikorsky, Tomas; Meir, Ziv; Akerman, Nitzan; Ben-shlomi, Ruti; Ozeri, Roee

    2017-07-01

    We study the time-dependent fluorescence of an initially hot, multilevel, single atomic ion trapped in a radio-frequency Paul trap during Doppler cooling. We have developed an analytical model that describes the fluorescence dynamics during Doppler cooling which is used to extract the initial energy of the ion. While previous models of Doppler cooling thermometry were limited to atoms with a two-level energy structure and neglected the effect of the trap oscillating electric fields, our model applies to atoms with multilevel energy structure and takes into account the influence of micromotion on the cooling dynamics. This thermometry applies to any initial energy distribution. We experimentally test our model with an ion prepared in coherent, thermal, and Tsallis energy distributions.

  12. In-vivo three-dimensional Doppler variance imaging for tumor angiogenesis on chorioallantoic membrane

    NASA Astrophysics Data System (ADS)

    Qi, Wenjuan; Liu, Gangjun; Chen, Zhongping

    2011-03-01

    Non-invasive tumor microvasculature visualization and characterization play significant roles in the detection of tumors and importantly, for aiding in the development of therapeutic strategies. The feasibility and effectiveness of a Doppler variance standard deviation imaging method for tumor angiogenesis on chorioallantoic membrane were tested in vivo on a rat glioma F98 tumor spheroid. Utilizing a high resolution Doppler Variance Optical Coherence Tomography (DVOCT) system with A-line rate of 20 kHz, three-dimensional mapping of a tumor with a total area of 3×2.5mm2 was completed within 15 seconds. The top-view image clearly visualized the complex vascular perfusion with the detection of capillaries as small as approximately 10μm. The results of the current study demonstrate the capability of the Doppler variance standard deviation imaging method as a non-invasive assessment of tumor angiogenesis, with the potential for its use in clinical settings.

  13. Embedded System for Real-Time Digital Processing of Medical Ultrasound Doppler Signals

    NASA Astrophysics Data System (ADS)

    Ricci, S.; Dallai, A.; Boni, E.; Bassi, L.; Guidi, F.; Cellai, A.; Tortoli, P.

    2008-12-01

    Ultrasound (US) Doppler systems are routinely used for the diagnosis of cardiovascular diseases. Depending on the application, either single tone bursts or more complex waveforms are periodically transmitted throughout a piezoelectric transducer towards the region of interest. Extraction of Doppler information from echoes backscattered from moving blood cells typically involves coherent demodulation and matched filtering of the received signal, followed by a suitable processing module. In this paper, we present an embedded Doppler US system which has been designed as open research platform, programmable according to a variety of strategies in both transmission and reception. By suitably sharing the processing tasks between a state-of-the-art FGPA and a DSP, the system can be used in several medical US applications. As reference examples, the detection of microemboli in cerebral circulation and the measurement of wall _distension_ in carotid arteries are finally presented.

  14. Low-noise III-V metasurface based semiconductor vortex laser and rotational Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Seghilani, Mohamed; Chomet, Baptiste; Myara, Mikhael; Sellahi, Mohamed; Legratiet, Luc; Beaudoin, Gregoire; Sagnes, Isabelle; Lalanne, Philippe; Garnache, Arnaud

    2017-03-01

    We demonstrate a surface-emitting laser, based on III-V semiconductor technology with an integrated metasurface, generating vortex-like coherent state in the Laguerre-Gauss basis.24 We use a first order phase perturbation to introduce a weak orbital anisotropy, based on a dielectric metasurface and non-linear laser dynamics, allowing selecting vortex handedness. Moreover, similarly to linear Doppler Shift, light carrying orbital angular momentum L, scattered by a rotating object at angular velocity, experiences a rotational Doppler shift L. We show that this fundamental light matter interaction can be detected exploiting self-mixing in a vortex laser under Doppler-shifted optical feedback, with quantum noise-limited light detection.25 This will allow us to combine a velocity sensor with optical tweezers for micro-manipulation applications, with high performances, simplicity and compactness. Such high performance laser opens the path to widespread new photonic applications.

  15. Millisecond, micron precision multi-whisker detector.

    PubMed

    Grady, Stephen K; Hoang, Thanh T; Gautam, Shree Hari; Shew, Woodrow L

    2013-01-01

    The neural mechanisms of somatosensory information processing in the rodent vibrissae system are a topic of intense debate and research. Certain hypotheses emphasize the importance of stick-slip whisker motion, high-frequency resonant vibrations, and/or the ability to decode complex textures. Other hypotheses focus on the importance of integrating information from multiple whiskers. Tests of the former require measurements of whisker motion that achieve high spatiotemporal accuracy without altering the mechanical properties of whiskers. Tests of the latter require the ability to monitor the motion of multiple whiskers simultaneously. Here we present a device that achieves both these requirements for two-dimensional whisker motion in the plane perpendicular to the whiskers. Moreover, the system we present is significantly less expensive (<$2.5 k) and simpler to build than alternative devices which achieve similar detection capabilities. Our system is based on two laser diodes and two linear cameras. It attains millisecond temporal precision and micron spatial resolution. We developed automated algorithms for processing the data collected by our device and benchmarked their performance against manual detection by human visual inspection. By this measure, our detection was successful with less than 10 µm deviation between the automated and manual detection, on average. Here, we demonstrate its utility in anesthetized rats by measuring the motion of multiple whiskers in response to an air puff.

  16. Ho-doped Soft Glass Optical Fibers for Coherent Wavelength Sources Above 2 Micron

    DTIC Science & Technology

    2010-12-01

    Politecnico di Torino – Dipartimento di Scienza dei Materiali e Ingegneria Chimica Corso Duca degli Abruzzi, 24 – 10129 Torino Italia tel: +39...Abruzzi, 24 – 10129 Torino Italia tel: +39 011 564 4707 fax: +39 011 564 4699 e-mail: daniel.milanese@polito.it url: www.composites.polito.it...Materiali e Ingegneria Chimica Corso Duca degli Abruzzi, 24 – 10129 Torino Italia tel: +39 011 564 4707 fax: +39 011 564 4699 e-mail

  17. Coherent laser radar at 3.6 microm.

    PubMed

    Hanson, Frank; Lasher, Mark

    2002-12-20

    Coherent laser radar systems in the mid-IR wavelength region can have advantages in low-altitude environment because they are less sensitive to scattering, turbulence, and humidity, which can affect shorter- or longer-wavelength system. We describe a coherent laser radar at 3.6 microm based on a single-frequency optical parametric oscillator and demonstrate the system over short ranges outdoors. The system was used to make micro-Doppler measurements from idling trucks that were processed to give surface vibration spectra.

  18. The calibration of Doppler receivers

    NASA Astrophysics Data System (ADS)

    Jaks, W.

    A study to determine the relative positions of the antennas of two simultaneously operating Doppler receivers and the systematic corrections needed for a given type of receiver is presented. The types of receivers included in the study are listed and results showing the differences between the geocentric coordinates of the antenna phase centers of the receivers are given. It is found that, for DOG receivers, each antenna phase center must be determined separately.

  19. Doppler ultrasound evaluation in preeclampsia

    PubMed Central

    2013-01-01

    Background Worldwide preeclampsia (PE) is the leading cause of maternal death and affects 5 to 8% of pregnant women. PE is characterized by elevated blood pressure and proteinuria. Doppler Ultrasound (US) evaluation has been considered a useful method for prediction of PE; however, there is no complete data about the most frequently altered US parameters in the pathology. The aim of this study was to evaluate the uterine, umbilical, and the middle cerebral arteries using Doppler US parameters [resistance index (RI), pulsatility index (PI), notch (N), systolic peak (SP) and their combinations] in pregnant women, in order to make a global evaluation of hemodynamic repercussion caused by the established PE. Results A total of 102 pregnant Mexican women (65 PE women and 37 normotensive women) were recruited in a cases and controls study. Blood velocity waveforms from uterine, umbilical, and middle cerebral arteries, in pregnancies from 24 to 37 weeks of gestation were recorded by trans-abdominal examination with a Toshiba Ultrasound Power Vision 6000 SSA-370A, with a 3.5 MHz convex transducer. Abnormal general Doppler US profile showed a positive association with PE [odds ratio (OR) = 2.93, 95% confidence interval (CI) = 1.2 - 7.3, P = 0.021)], and a specificity and predictive positive value of 89.2% and 88.6%, respectively. Other parameters like N presence, RI and PI of umbilical artery, as well as the PI of middle cerebral artery, showed differences between groups (P values < 0.05). Conclusion General Doppler US result, as well as N from uterine vessel, RI from umbilical artery, and PI from umbilical and middle cerebral arteries in their individual form, may be considered as tools to determine hemodynamic repercussion caused by PE. PMID:24252303

  20. Doppler ultrasound evaluation in preeclampsia.

    PubMed

    Lopez-Mendez, Maria A; Martinez-Gaytan, Victoria; Cortes-Flores, Raul; Ramos-Gonzalez, Rene M; Ochoa-Torres, Mauro A; Garza-Veloz, Idalia; Martinez-Acuña, Monica I; Badillo-Almaraz, Jose I; Martinez-Fierro, Margarita L

    2013-11-19

    Worldwide preeclampsia (PE) is the leading cause of maternal death and affects 5 to 8% of pregnant women. PE is characterized by elevated blood pressure and proteinuria. Doppler Ultrasound (US) evaluation has been considered a useful method for prediction of PE; however, there is no complete data about the most frequently altered US parameters in the pathology. The aim of this study was to evaluate the uterine, umbilical, and the middle cerebral arteries using Doppler US parameters [resistance index (RI), pulsatility index (PI), notch (N), systolic peak (SP) and their combinations] in pregnant women, in order to make a global evaluation of hemodynamic repercussion caused by the established PE. A total of 102 pregnant Mexican women (65 PE women and 37 normotensive women) were recruited in a cases and controls study. Blood velocity waveforms from uterine, umbilical, and middle cerebral arteries, in pregnancies from 24 to 37 weeks of gestation were recorded by trans-abdominal examination with a Toshiba Ultrasound Power Vision 6000 SSA-370A, with a 3.5 MHz convex transducer. Abnormal general Doppler US profile showed a positive association with PE [odds ratio (OR) = 2.93, 95% confidence interval (CI) = 1.2 - 7.3, P = 0.021)], and a specificity and predictive positive value of 89.2% and 88.6%, respectively. Other parameters like N presence, RI and PI of umbilical artery, as well as the PI of middle cerebral artery, showed differences between groups (P values < 0.05). General Doppler US result, as well as N from uterine vessel, RI from umbilical artery, and PI from umbilical and middle cerebral arteries in their individual form, may be considered as tools to determine hemodynamic repercussion caused by PE.