Approaches for Achieving Broadband Achromatic Phase Shifts for Visible Nulling Coronagraphy
NASA Technical Reports Server (NTRS)
Bolcar, Matthew R.; Lyon, Richard G.
2012-01-01
Visible nulling coronagraphy is one of the few approaches to the direct detection and characterization of Jovian and Terrestrial exoplanets that works with segmented aperture telescopes. Jovian and Terrestrial planets require at least 10(exp -9) and 10(exp -10) image plane contrasts, respectively, within the spectral bandpass and thus require a nearly achromatic pi-phase difference between the arms of the interferometer. An achromatic pi-phase shift can be achieved by several techniques, including sequential angled thick glass plates of varying dispersive materials, distributed thin-film multilayer coatings, and techniques that leverage the polarization-dependent phase shift of total-internal reflections. Herein we describe two such techniques: sequential thick glass plates and Fresnel rhomb prisms. A viable technique must achieve the achromatic phase shift while simultaneously minimizing the intensity difference, chromatic beam spread and polarization variation between each arm. In this paper we describe the above techniques and report on efforts to design, model, fabricate, align the trades associated with each technique that will lead to an implementations of the most promising one in Goddard's Visible Nulling Coronagraph (VNC).
Phase shifting diffraction interferometer
Sommargren, Gary E.
1996-01-01
An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.
Sommargren, G.E.
1999-08-03
An interferometer is disclosed which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 11 figs.
Sommargren, Gary E.
1999-01-01
An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.
Phase shifting diffraction interferometer
Sommargren, G.E.
1996-08-29
An interferometer which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 8 figs.
Four-phase differential phase shift resolver
NASA Technical Reports Server (NTRS)
Hopkins, P. M.; Wallingford, W. M.
1973-01-01
Two systems have been developed to resolve phase uncertainty without transmitting reference signals. In both methods signal is impressed on carrier as differential, rather than absolute, phase shift. At the receiver four-phase demodulation and logic process unambiguously resolves differential phase shift of input carrier.
Suppressing phase errors from vibration in phase-shifting interferometry
Deck, Leslie L.
2009-07-10
A general method for reducing the influence of vibrations in phase-shifting interferometry corrects the surface phase map through a spectral analysis of a ''phase-error pattern,'' a plot of the interference intensity versus the measured phase, for each phase-shifted image. The method is computationally fast, applicable to any phase-shifting algorithm and interferometer geometry, has few restrictions on surface shape, and unlike spatial Fourier methods, high density spatial carrier fringes are not required, although at least a fringe of phase departure is recommended. Over a 100x reduction in vibrationally induced surface distortion is achieved for small amplitude vibrations on real data.
Dynamic phase-shifting photoelasticity.
Asundi, A; Tong, L; Boay, C G
2001-08-01
The application of phase-shifting photoelasticity to a real-time dynamic event involves simultaneous recording of the four phase-shifted images. Here an instrument, believed to be novel, is developed and described for this purpose. Use of a Multispec Imager is introduced into digital photoelasticity for the first time to our knowledge. This device enables splitting the optical energy of an object into four identical paths, thus permitting recording of the required four phase-shifted images. Experimental demonstration is provided for validation. PMID:18360395
Geometric phase shifting digital holography.
Jackin, Boaz Jessie; Narayanamurthy, C S; Yatagai, Toyohiko
2016-06-01
A new phase shifting digital holographic technique using a purely geometric phase in Michelson interferometric geometry is proposed. The geometric phase in the system does not depend upon either optical path length or wavelength, unlike dynamic phase. The amount of geometric phase generated is controllable through a rotating wave plate. The new approach has unique features and major advantages in holographic measurement of transparent and reflecting three-dimensional (3D) objects. Experimental results on surface shape measurement and imaging of 3D objects are presented using the proposed method. PMID:27244436
Multicolor Holography With Phase Shifting
NASA Technical Reports Server (NTRS)
Vikram, Chandra S.
1996-01-01
Prototype apparatus constructed to test feasibility of two-color holographic interferometric scheme in which data for reconstructing holographic wavefront obtained with help of phase-shifting technique. Provides two sets of data needed to solve equations for effects of temperature and concentration. Concept extended to holography at three or more wavelengths to measure three or more phenomena associated with significant variations in index of refraction
Differential phase shift keyed signal resolver
NASA Technical Reports Server (NTRS)
Hopkins, P. M.; Wallingford, W. M. (Inventor)
1974-01-01
A differential phase shift keyed signal resolver resolves the differential phase shift in the incoming signal to determine the data content thereof overcoming phase uncertainty without requiring a transmitted reference signal.
Confocal simultaneous phase-shifting interferometry
Zhao Chenguang; Tan Jiubin; Tang Jianbo; Liu Tao; Liu Jian
2011-02-10
In order to implement the ultraprecise measurement with large range and long working distance in confocal microscopy, confocal simultaneous phase-shifting interferometry (C-SPSI) has been presented. Four channel interference signals, with {pi}/2 phase shift between each other, are detected simultaneously in C-SPSI. The actual surface height is then calculated by combining the optical sectioning with the phase unwrapping in the main cycle of the interference phase response, and the main cycle is determined using the bipolar property of differential confocal microscopy. Experimental results showed that 1 nm of axial depth resolution was achieved for either low- or high-NA objective lenses. The reflectivity disturbance resistibility of C-SPSI was demonstrated by imaging a typical microcircuit specimen. C-SPSI breaks through the restriction of low NA on the axial depth resolution of confocal microscopy effectively.
A novel phase shifting structured illumination microscopy
NASA Astrophysics Data System (ADS)
Singh, Veena; Dubey, Vishesh; Ahmad, Azeem; Singh, Gyanendra; Mehta, D. S.
2016-03-01
This paper describes a new and novel phase shifting technique for qualitative as well as quantitative measurement in microscopy. We have developed a phase shifting device which is robust, inexpensive and involves no mechanical movement. In this method, phase shifting is implemented using LED array, beam splitters and defocused projection of Ronchi grating. The light from the LEDs are made incident on the beam splitters at spatially different locations. Due to variation in the geometrical distances of LEDs from the Ronchi grating and by sequentially illuminating the grating by switching on one LED at a time the phase shifted grating patterns are generated. The phase shifted structured patterns are projected onto the sample using microscopic objective lens. The phase shifted deformed patterns are recorded by a CCD camera. The initial alignment of the setup involves a simple procedure for the calibration for equal fringe width and intensity such that the phase shifted fringes are at equal phase difference. Three frame phase shifting algorithm is employed for the reconstruction of the phase map. The method described here is fully automated so that the phase shifted images are recorded just by switching of LEDs and has been used for the shape measurement of microscopic industrial objects. The analysis of the phase shifted images provides qualitative as well as quantitative information about the sample. Thus, the method is simple, robust and low cost compared to PZT devices commonly employed for phase shifting.
Tracking a phase-shift-keyed signal
NASA Technical Reports Server (NTRS)
Villarreal, S.; Lenett, S. D.; Kobayashi, H. S.; Pawlowski, J. F.
1977-01-01
In detector, phase shifter is used to generate negative phase shift opposing detected phase angle. This produces converted series sideband and component carrier, with residual carrier signal and converted series sideband and component carrier added together to produce tracking signal.
In-line phase shift tomosynthesis
Hammonds, Jeffrey C.; Price, Ronald R.; Pickens, David R.; Donnelly, Edwin F.
2013-08-15
Purpose: The purpose of this work is to (1) demonstrate laboratory measurements of phase shift images derived from in-line phase-contrast radiographs using the attenuation-partition based algorithm (APBA) of Yan et al.[Opt. Express 18(15), 16074–16089 (2010)], (2) verify that the APBA reconstructed images obey the linearity principle, and (3) reconstruct tomosynthesis phase shift images from a collection of angularly sampled planar phase shift images.Methods: An unmodified, commercially available cabinet x-ray system (Faxitron LX-60) was used in this experiment. This system contains a tungsten anode x-ray tube with a nominal focal spot size of 10 μm. The digital detector uses CsI/CMOS with a pixel size of 50 × 50 μm. The phantoms used consisted of one acrylic plate, two polystyrene plates, and a habanero pepper. Tomosynthesis images were reconstructed from 51 images acquired over a ±25° arc. All phase shift images were reconstructed using the APBA.Results: Image contrast derived from the planar phase shift image of an acrylic plate of uniform thickness exceeded the contrast of the traditional attenuation image by an approximate factor of two. Comparison of the planar phase shift images from a single, uniform thickness polystyrene plate with two polystyrene plates demonstrated an approximate linearity of the estimated phase shift with plate thickness (−1600 rad vs −2970 rad). Tomographic phase shift images of the habanero pepper exhibited acceptable spatial resolution and contrast comparable to the corresponding attenuation image.Conclusions: This work demonstrated the feasibility of laboratory-based phase shift tomosynthesis and suggests that phase shift imaging could potentially provide a new imaging biomarker. Further investigation will be needed to determine if phase shift contrast will be able to provide new tissue contrast information or improved clinical performance.
Deterministic convergence in iterative phase shifting
Luna, Esteban; Salas, Luis; Sohn, Erika; Ruiz, Elfego; Nunez, Juan M.; Herrera, Joel
2009-03-10
Previous implementations of the iterative phase shifting method, in which the phase of a test object is computed from measurements using a phase shifting interferometer with unknown positions of the reference, do not provide an accurate way of knowing when convergence has been attained. We present a new approach to this method that allows us to deterministically identify convergence. The method is tested with a home-built Fizeau interferometer that measures optical surfaces polished to {lambda}/100 using the Hydra tool. The intrinsic quality of the measurements is better than 0.5 nm. Other possible applications for this technique include fringe projection or any problem where phase shifting is involved.
Data for phase angle shift with frequency.
Paul, T; Banerjee, D; Kargupta, K
2016-06-01
Phase angle shift between the current and voltage with frequency has been reported for a single phosphoric acid fuel cell in the cell temperature from 100 °C to 160 °C and the humidifier temperature from 40 °C to 90 °C. An electrochemical workbench is employed to find the shift. The figure of phase angle shift shows a peak in high humidifier temperatures. The peak in phase angle shift directs to lower frequency side with decreasing humidifier temperature. The estimation of electrochemical reaction time is also evaluated in the humidifier temperature zone from 50 °C to 90 °C. PMID:27158655
Data for phase angle shift with frequency
Paul, T.; Banerjee, D.; Kargupta, K.
2016-01-01
Phase angle shift between the current and voltage with frequency has been reported for a single phosphoric acid fuel cell in the cell temperature from 100 °C to 160 °C and the humidifier temperature from 40 °C to 90 °C. An electrochemical workbench is employed to find the shift. The figure of phase angle shift shows a peak in high humidifier temperatures. The peak in phase angle shift directs to lower frequency side with decreasing humidifier temperature. The estimation of electrochemical reaction time is also evaluated in the humidifier temperature zone from 50 °C to 90 °C. PMID:27158655
Energy phase shift as mechanism for catalysis
NASA Astrophysics Data System (ADS)
Beke-Somfai, Tamás; Feng, Bobo; Nordén, Bengt
2012-05-01
Catalysts are agents that by binding reactant molecules lower the energy barriers to chemical reaction. After reaction the catalyst is regenerated, its unbinding energy recruited from the environment, which is associated with an inevitable loss of energy. We show that combining several catalytic sites to become energetically and temporally phase-shifted relative to each other provides a possibility to sustain the overall reaction by internal 'energy recycling', bypassing the need for thermal activation, and in principle allowing the system to work adiabatically. Using an analytical model for superimposed, phase-shifted potentials of F1-ATP synthase provides a description integrating main characteristics of this rotary enzyme complex.
Model-based phase-shifting interferometer
NASA Astrophysics Data System (ADS)
Liu, Dong; Zhang, Lei; Shi, Tu; Yang, Yongying; Chong, Shiyao; Miao, Liang; Huang, Wei; Shen, Yibing; Bai, Jian
2015-10-01
A model-based phase-shifting interferometer (MPI) is developed, in which a novel calculation technique is proposed instead of the traditional complicated system structure, to achieve versatile, high precision and quantitative surface tests. In the MPI, the partial null lens (PNL) is employed to implement the non-null test. With some alternative PNLs, similar as the transmission spheres in ZYGO interferometers, the MPI provides a flexible test for general spherical and aspherical surfaces. Based on modern computer modeling technique, a reverse iterative optimizing construction (ROR) method is employed for the retrace error correction of non-null test, as well as figure error reconstruction. A self-compiled ray-tracing program is set up for the accurate system modeling and reverse ray tracing. The surface figure error then can be easily extracted from the wavefront data in forms of Zernike polynomials by the ROR method. Experiments of the spherical and aspherical tests are presented to validate the flexibility and accuracy. The test results are compared with those of Zygo interferometer (null tests), which demonstrates the high accuracy of the MPI. With such accuracy and flexibility, the MPI would possess large potential in modern optical shop testing.
Xu, Xiaoqing; Wang, Yawei; Xu, Yuanyuan; Jin, Weifeng
2016-06-01
To efficiently promote the phase retrieval in quantitative phase imaging, a new approach of quantitative phase extraction is proposed based on two intensities with dual wavelength after filtering the corresponding dc terms for each wavelength, in which a special phase shift is used. In this approach, only the combination of the phase-shifting technique and subtraction procedures is needed, and no additional algorithms are required. The thickness of the phase object can be achieved from the phase image, which is related to the synthetic beat wavelength. The feasibility of this method is verified by the simulated experiments of the optically transparent objects. PMID:27244381
Accurate phase-shift velocimetry in rock.
Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R; Holmes, William M
2016-06-01
Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models. PMID:27111139
Accurate phase-shift velocimetry in rock
NASA Astrophysics Data System (ADS)
Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R.; Holmes, William M.
2016-06-01
Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models.
Phase-Shifting Zernike Interferometer Wavefront Sensor
NASA Technical Reports Server (NTRS)
Wallace, J. Kent; Rao, Shanti; Jensen-Clem, Rebecca M.
2011-01-01
The canonical Zernike phase-contrast technique transforms a phase object in one plane into an intensity object in the conjugate plane. This is done by applying a static pi/2 phase shift to the central core (approx. lambda/diameter) of the PSF which is intermediate between the input and output plane. Here we present a new architecture for this sensor. First, the optical system is simple and all reflective, and second the phase shift in the central core of the PSF is dynamic and can be made arbitrarily large. This common-path, all-reflective design makes it minimally sensitive to vibration, polarization and wavelength. We review the theory of operation, describe the optical system, summarize numerical simulations and sensitivities and review results from a laboratory demonstration of this novel instrument.
Phase-Shifting Zernike Interferometer Wavefront Sensor
NASA Technical Reports Server (NTRS)
Wallace, J. Kent; Rao, Shanti; Jensen-Clemb, Rebecca M.; Serabyn, Gene
2011-01-01
The canonical Zernike phase-contrast technique1,2,3,4 transforms a phase object in one plane into an intensity object in the conjugate plane. This is done by applying a static pi/2 phase shift to the central core (approx. lambda/D) of the PSF which is intermediate between the input and output planes. Here we present a new architecture for this sensor. First, the optical system is simple and all reflective. Second, the phase shift in the central core of the PSF is dynamic and or arbitrary size. This common-path, all-reflective design makes it minimally sensitive to vibration, polarization and wavelength. We review the theory of operation, describe the optical system, summarize numerical simulations and sensitivities and review results from a laboratory demonstration of this novel instrument
Improved phase-shift-keyed detector
NASA Technical Reports Server (NTRS)
Chandler, J.
1969-01-01
Improved phase-shift-keyed detector contains an active filter circuit which uses an operational amplifier and resistor-capacitor network. The detector is used in the Saturn space vehicle and Apollo telescope mount command systems to translate an analog signal from the command receiver into digital information for the command decoder.
The Phase Shift in the Jumping Ring
ERIC Educational Resources Information Center
Jeffery, Rondo N.; Amiri, Farhang
2008-01-01
The popular physics demonstration experiment known as Thomson's Jumping Ring (JR) has been variously explained as a simple example of Lenz's law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenz's law explanation is shown by the time the ring takes to jump and by levitation.…
Photonic downconversion with tunable wideband phase shift.
Jiang, Tianwei; Yu, Song; Wu, Ruihuan; Wang, Dongsheng; Gu, Wanyi
2016-06-01
A microwave photonic frequency downconversion system with wideband and continuous phase-shift function is proposed and experimentally demonstrated. In the proposed system, a radio frequency (RF) and a local oscillator (LO) signal drive two arms of a dual-drive Mach-Zehnder modulator (DMZM). A fiber Bragg grating (FBG) is used for reflecting the first-order sidebands of both RF and LO signals. Due to phase independence between RF and LO optical sidebands, the phase-shifting operation for an output intermediate frequency (IF) signal can be implemented either by adjusting the bias voltage of DMZM or by controlling the optical wavelength of laser. Experimental results demonstrate a full 0° to 360° phase shift, while an RF signal between 12 GHz to 20 GHz is downconverted to IFs below 4 GHz. The phase deviation is measured less than 2°, and the fluctuation of magnitude response is measured less than ±1 dB over a wideband frequency range. PMID:27244434
Transitional Bubble in Periodic Flow Phase Shift
NASA Technical Reports Server (NTRS)
Talan, M.; Hourmouziadis, Jean
2004-01-01
One particular characteristic observed in unsteady shear layers is the phase shift relative to the main flow. In attached boundary layers this will have an effect both on the instantaneous skin friction and heat transfer. In separation bubbles the contribution to the drag is dominated by the pressure distribution. However, the most significant effect appears to be the phase shift on the transition process. Unsteady transition behaviour may determine the bursting of the bubble resulting in an un-recoverable full separation. An early analysis of the phase shift was performed by Stokes for the incompressible boundary layer of an oscillating wall and an oscillating main flow. An amplitude overshoot within the shear layer as well as a phase shift were observed that can be attributed to the relatively slow diffusion of viscous stresses compared to the fast change of pressure. Experiments in a low speed facility with the boundary layer of a flat plate were evaluated in respect to phase shift. A pressure distribution similar to that on the suction surface of a turbomachinery aerofoil was superimposed generating a typical transitional separation bubble. A periodically unsteady main flow in the suction type wind tunnel was introduced via a rotating flap downstream of the test section. The experiments covered a range of the three similarity parameters of momentum-loss-thickness Reynolds-number of 92 to 226 and Strouhal-number (reduced frequency) of 0.0001 to 0.0004 at the separation point, and an amplitude range up to 19 %. The free stream turbulence level was less than 1% .Upstream of the separation point the phase shift in the laminar boundary layer does not appear to be affected significantly bay either of the three parameters. The trend perpendicular to the wall is similar to the Stokes analysis. The problem scales well with the wave velocity introduced by Stokes, however, the lag of the main flow near the wall is less than indicated analytically. The separation point
Inhomogeneous phase shifting: an algorithm for nonconstant phase displacements
Tellez-Quinones, Alejandro; Malacara-Doblado, Daniel
2010-11-10
In this work, we have developed a different algorithm than the classical one on phase-shifting interferometry. These algorithms typically use constant or homogeneous phase displacements and they can be quite accurate and insensitive to detuning, taking appropriate weight factors in the formula to recover the wrapped phase. However, these algorithms have not been considered with variable or inhomogeneous displacements. We have generalized these formulas and obtained some expressions for an implementation with variable displacements and ways to get partially insensitive algorithms with respect to these arbitrary error shifts.
Controllable optical phase shift over one radian from a single isolated atom.
Jechow, A; Norton, B G; Händel, S; Blūms, V; Streed, E W; Kielpinski, D
2013-03-15
Fundamental optics such as lenses and prisms work by applying phase shifts of several radians to incoming light, and rapid control of such phase shifts is crucial to telecommunications. However, large, controllable optical phase shifts have remained elusive for isolated quantum systems. We have used a single trapped atomic ion to induce and measure a large optical phase shift of 1.3±0.1 radians in light scattered by the atom. Spatial interferometry between the scattered light and unscattered illumination light enables us to isolate the phase shift in the scattered component. The phase shift achieves the maximum value allowed by atomic theory over the accessible range of laser frequencies, pointing out new opportunities in microscopy and nanophotonics. Single-atom phase shifts of this magnitude open up new quantum information protocols, in particular long-range quantum phase-shift-keying cryptography. PMID:25166534
Polarization phase shifting dispersed fringe sensor.
Olczak, Gene
2012-02-13
The dispersed fringe sensor (DFS) has been demonstrated as an effective means of measuring mirror segment piston error for telescopes with primary mirror apertures below 10 meters. With larger proposed telescopes such as The Thirty Meter Telescope (TMT) and The European Large Telescope (ELT) including ever more segments, there is a need for improvement in the co-phasing capability for segmented primary mirrors. In this paper a novel DFS that employs polarization phase shifting technology is introduced. This novel technology provides system designers and engineers with a new tool to extend the dynamic range of a DFS. PMID:22418128
Phase-shifting point diffraction interferometer phase grating designs
Naulleau, Patrick
2001-01-01
Diffraction phase gratings are employed in phase-shifting point diffraction interferometers to improve the interferometric fringe contrast. The diffraction phase grating diffracts a zeroth-order diffraction of light at a first power level to the test-beam window of a mask that is positioned at the image plane and a first-order diffraction at a second power to the reference-beam pinhole. The diffraction phase grating is preferably selected to yield a desired ratio of the first power level to second power level.
Phase-Shifted Laser Feedback Interferometry
NASA Technical Reports Server (NTRS)
Ovryn, Benjie
1999-01-01
Phase-shifted, laser feedback interferometry is a new diagnostic tool developed at the NASA Lewis Research Center under the Advanced Technology Development (ATD) Program directed by NASA Headquarters Microgravity Research Division. It combines the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce an instrument that can quantify both optical path length changes and sample reflectivity variations. In a homogenous medium, the optical path length between two points is the product of the index of refraction and the geometric distance between the two points. LFI differs from other forms of interferometry by using the laser as both the source and the phase detector. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. The combination of PSI and LFI has produced a robust instrument, based on a low-power helium-neon (HeNe) gas laser, with a high dynamic range that can be used to measure either static or oscillatory changes of the optical path length. Small changes in optical path length are limited by the fraction of a fringe that can be measured; we can measure nonoscillatory changes with a root mean square (rms) error of the wavelength/1000 without averaging.
Color deflectometry for phase retrieval using phase-shifting methods
NASA Astrophysics Data System (ADS)
Flores, Jorge L.; Legarda-Saenz, Ricardo; Garcia-Torales, G.
2015-01-01
In this paper, we propose a technique based on a color fringe pattern used on deflectometry experiment. The advantages of using color fringe patterns together with phase shifting techniques on deflectometry experiment are presented. An experimental wavefront reconstruction of a progressive lens shows the accuracy and simplicity of these techniques used to process the deflection measurements.
Chemical Shift Induced Phase Errors in Phase Contrast MRI
Middione, Matthew J.; Ennis, Daniel B.
2012-01-01
Phase contrast magnetic resonance imaging (PC-MRI) is subject to numerous sources of error, which decrease clinical confidence in the reported measures. This work outlines how stationary perivascular fat can impart a significant chemical shift induced PC-MRI measurement error using computational simulations, in vitro, and in vivo experiments. This chemical shift error does not subtract in phase difference processing, but can be minimized with proper parameter selection. The chemical shift induced phase errors largely depend on both the receiver bandwidth (BW) and the TE. Both theory and an in vivo comparison of the maximum difference in net forward flow between vessels with and without perivascular fat indicated that the effects of chemically shifted perivascular fat are minimized by the use of high BW (814 Hz/px) and an in-phase TE (HBW-TEIN). In healthy volunteers (N=10) HBW-TEIN significantly improves intrapatient net forward flow agreement compared to low BW (401 Hz/px) and a mid-phase TE as indicated by significantly decreased measurement biases and limits of agreement for the ascending aorta (1.8±0.5 mL vs. 6.4±2.8 mL, P=0.01), main pulmonary artery (2.0±0.9 mL vs. 11.9±5.8 mL, P=0.04), the left pulmonary artery (1.3±0.9 mL vs. 5.4±2.5 mL, P=0.003), and all vessels (1.7±0.8 mL vs. 7.2±4.4 mL, P=0.001). PMID:22488490
Phase-shifting point diffraction interferometer
Medecki, Hector
1998-01-01
Disclosed is a point diffraction interferometer for evaluating the quality of a test optic. In operation, the point diffraction interferometer includes a source of radiation, the test optic, a beam divider, a reference wave pinhole located at an image plane downstream from the test optic, and a detector for detecting an interference pattern produced between a reference wave emitted by the pinhole and a test wave emitted from the test optic. The beam divider produces separate reference and test beams which focus at different laterally separated positions on the image plane. The reference wave pinhole is placed at a region of high intensity (e.g., the focal point) for the reference beam. This allows reference wave to be produced at a relatively high intensity. Also, the beam divider may include elements for phase shifting one or both of the reference and test beams.
Phase-shifting point diffraction interferometer
Medecki, H.
1998-11-10
Disclosed is a point diffraction interferometer for evaluating the quality of a test optic. In operation, the point diffraction interferometer includes a source of radiation, the test optic, a beam divider, a reference wave pinhole located at an image plane downstream from the test optic, and a detector for detecting an interference pattern produced between a reference wave emitted by the pinhole and a test wave emitted from the test optic. The beam divider produces separate reference and test beams which focus at different laterally separated positions on the image plane. The reference wave pinhole is placed at a region of high intensity (e.g., the focal point) for the reference beam. This allows reference wave to be produced at a relatively high intensity. Also, the beam divider may include elements for phase shifting one or both of the reference and test beams. 8 figs.
Phase shifting interferometry using a spatial light modulator to measure optical thin films.
Villalobos-Mendoza, Brenda; Granados-Agustín, Fermín S; Aguirre-Aguirre, Daniel; Cornejo-Rodríguez, Alejandro
2015-09-10
This work describes a process for measuring thin film steps, using phase shifting interferometry (PSI). The phase shifts are applied only in the region where the thin film steps are located. The phase shift is achieved by displaying different gray levels on a spatial light modulator (SLM Holoeye LC2012) placed in one arm of a Twyman-Green (T-G) interferometer. Before measuring the thin film steps, it was necessary to quantify the phase shifts achieved with this SLM by measuring the fringe shifts in experimental interferograms. The phase shifts observed in the interference patterns were produced by displaying the different gray levels on the SLM one by one, from 0 to 255. The experimental interferograms and the thicknesses of the thin film steps were successfully quantified, proving that this method can be used to measure thin films by applying the PSI method only on the region occupied by them. PMID:26368976
Phase-shifting behaviour revisited: An alternative measure
NASA Astrophysics Data System (ADS)
Kang, Bo Soo; Ryu, Doojin; Ryu, Doowon
2014-05-01
This study re-examines the recently documented phase-shifting behaviour of financial markets using an alternative measure, an intraday return-based measure. While most previous studies on phase-shifting behaviour adopt the volume-imbalance measure proposed by Plerou et al. (2003), we find that our return-based measure successfully captures phase-shifting behaviour, and moreover exhibits a unique pattern of phase-shifting that is not detected when the classical volume imbalance measure is used. By analysing a high-frequency dataset of KOSPI200 futures, we also find that large trades reveal phase-shifting behaviour more clearly and significantly than smaller trades.
Phase shift estimation in interferograms with unknown phase step
NASA Astrophysics Data System (ADS)
Dalmau, Oscar; Rivera, Mariano; Gonzalez, Adonai
2016-08-01
We first present two closed formulas for computing the phase shift in interferograms with unknown phase step. These formulas obtain theoretically the exact phase step in fringe pattern without noise and only require the information in two pixels of the image. The previous formulas allows us to define a functional that yields an estimate of the phase step in interferograms corrupted by noise. In the experiment we use the standard Least Square formulation which also yields a closed formula, although the general formulation admits a robust potential. We provide two possible implementations of our approach, one in which the sites can be randomly selected and the other in which we can scan the whole image. The experiments show that the proposed algorithm presents the best results compared with state of the art algorithms.
High-durability phase-shift film with variable transmittance
NASA Astrophysics Data System (ADS)
Nozawa, Osamu; Shishido, Hiroaki; Kajiwara, Takenori
2015-10-01
In order to maintain the lithographic margin and to have sufficient image resolution, attenuated phase shift masks are widely used as a resolution enhancement technique. To improve the radiation durability of the phase shift film, we have developed low oxidation MoSi shifters, such as A6L2, as one option for improving radiation durability. But to provide the best radiation durability, we have developed a new approach eliminating the molybdenum from the phase shift film and introduced a Silicon-Nitride (Si-N) based attenuated phase shift film. Traditionally the transmittance of the phase shift layer is usually around 6%. In the case of a pure Si3N4 film, the transmittance with 180 degree phase shift is around 18%. But, by controlling film structure with a combination of Si-N the transmittance can be tuned to the customers desired transmission value for high durability Mo free attenuated phase shift films.
Random phase-shifting interferometry based on independent component analysis
NASA Astrophysics Data System (ADS)
Xu, Xiaofei; Lu, Xiaoxu; Tian, Jindong; Shou, Junwei; Zheng, Dejin; Zhong, Liyun
2016-07-01
In random phase-shifting interferometry, a novel phase retrieval algorithm is proposed based on the independent component analysis (ICA). By performing the recombination of pixel position, a sequence of phase-shifting interferograms with random phase shifts are decomposed into a group of mutual independent components, and then the background and the measured phase of interferogram can obtained with a simple arctangent operation. Compared with the conventional advanced iterative algorithm (AIA) with high accuracy, both the simulation and the experimental results demonstrate that the proposed ICA algorithm reveals high accuracy, rapid convergence, and good noise-tolerance in random phase-shifting interferometry.
Fast three-step phase-shifting algorithm
Huang, Peisen S.; Zhang Song
2006-07-20
We propose a new three-step phase-shifting algorithm, which is much faster than the traditional three-step algorithm. We achieve the speed advantage by using a simple intensity ratio function to replace the arc tangent function in the traditional algorithm. The phase error caused by this new algorithm is compensated for by use of a lookup table. Our experimental result sshow that both the new algorithm and the traditional algorithm generate similar results, but the new algorithm is 3.4 times faster. By implementing this new algorithm in a high-resolution, real-time three-dimensional shape measurement system,we were able to achieve a measurement speed of 40 frames per second ata resolution of 532x500 pixels, all with an ordinary personal computer.
NASA Astrophysics Data System (ADS)
Jia, Chuanwu; Chang, Jun; Wang, Fupeng; Jiang, Hao; Zhu, Cunguang; Wang, Pengpeng
2016-06-01
A phase shift demodulation technique based on subtraction capable of measuring 0.03 phase degree limit between sinusoidal signals is presented in this paper. A self-gain module and a practical subtracter act the kernel parts of the phase shift demodulation system. Electric signals in different phases are used to verify the performance of the system. In addition, a new designed optical source, laser fiber differential source (LFDS), capable of generating mini phase is used to further verify the system reliability. R-square of 0.99997 in electric signals and R-square of 0.99877 in LFDS are achieved, and 0.03 degree measurement limit is realized in experiments. Furthermore, the phase shift demodulation system is applied to the fluorescence phase based oxygen sensors to realize the fundamental function. The experimental results reveal that a good repetition and better than 0.02% oxygen concentration measurement accuracy are realized. In addition, the phase shift demodulation system can be easily integrated to other applications.
Anomalous phase shifts in drift wave fluctuations
NASA Astrophysics Data System (ADS)
Diallo, Ahmed; Skiff, Fred
2003-10-01
Ion phase space density fluctuation measurements are performed in a linearly magnetized device using Laser Induced Fluorescence(LIF). An ICP source produces an 8cm diameter plasma column that drifts in a cylindrical vessel whose diameter and length are 40 cm and 3 m, respectively. These experiments are performed using a CW singly ionized Argon plasma that is immersed in a 1kG magnetic field along the axis of the cylinder. A density of the order of 10^9 cm-3 is obtained under a regulated neutral background pressure of 2.× 10-4 torr. The electron and ion temperature are respectively 2 eV and 0.1 eV. LIF is carried out by pumping the Ar II metastable (3d^1)^2G_9/2, using a CW tunable laser centered at 611.6653 nm scanned over 6 GHz, to metastable (4p^1)F_7/2, and then detecting the 460nm photons emitted from its transition to (4s^1)^2F_5/2. This collection is made possible using two low f-umber periscopes that are directed to PMTs. Here we present measurements of the complex two-point correlation function < f(v_i_allel),z_1,ω)f(v_i_allel,z_2,ω)> as a function of the spatial separation of two LIF detection systems Δ d = z_2-z_1, the ion parallel velocity v_i_allel and the frequency ω. Preliminary results show ion particle velocity dependent phase shifts at the drift wave frequency.
Hybrid parallel computing architecture for multiview phase shifting
NASA Astrophysics Data System (ADS)
Zhong, Kai; Li, Zhongwei; Zhou, Xiaohui; Shi, Yusheng; Wang, Congjun
2014-11-01
The multiview phase-shifting method shows its powerful capability in achieving high resolution three-dimensional (3-D) shape measurement. Unfortunately, this ability results in very high computation costs and 3-D computations have to be processed offline. To realize real-time 3-D shape measurement, a hybrid parallel computing architecture is proposed for multiview phase shifting. In this architecture, the central processing unit can co-operate with the graphic processing unit (GPU) to achieve hybrid parallel computing. The high computation cost procedures, including lens distortion rectification, phase computation, correspondence, and 3-D reconstruction, are implemented in GPU, and a three-layer kernel function model is designed to simultaneously realize coarse-grained and fine-grained paralleling computing. Experimental results verify that the developed system can perform 50 fps (frame per second) real-time 3-D measurement with 260 K 3-D points per frame. A speedup of up to 180 times is obtained for the performance of the proposed technique using a NVIDIA GT560Ti graphics card rather than a sequential C in a 3.4 GHZ Inter Core i7 3770.
Frequency-multiplying microwave photonic phase shifter for independent multichannel phase shifting.
Zhang, Yamei; Pan, Shilong
2016-03-15
A frequency-multiplying microwave photonic phase shifter with independent multichannel phase shifting capability is proposed and demonstrated using an integrated polarization division multiplexing dual-parallel Mach-Zehnder modulator (PDM-DPMZM) and a polarizer. By building a proper power distribution network to drive the PDM-DPMZM, two sidebands along two orthogonal polarization directions are generated with a spacing of two or four times the frequency of the driving signal. Leading the signal to a polarizer and a photodetector, a frequency-doubled or frequency-quadrupled signal with its phase adjusted by the polarization direction of the polarizer is achieved. The magnitude of the signal remains almost unchanged when the phase is adjusted. The proposed approach features compact configuration, scalable independent phase-shift channels and wide bandwidth, which can find applications in beam forming and analog signal processing for millimeter-wave or terahertz applications. PMID:26977684
Generalized phase shifting interferometry based on Lissajous calibration technology
NASA Astrophysics Data System (ADS)
Liu, Fengwei; Wu, Yongqian; Wu, Fan; Song, Weihong
2016-08-01
The feasibility and limitation of directly using the Lissajous figure and ellipse fitting technology to correct the phase extraction error in generalized data reduction algorithm (GDRA) for phase extraction of randomly phase-shifted interferograms are analyzed and discussed. By combining Lissajous calibration technology, which represents the transformative process of Lissajous ellipse to circle (ETC), with advanced iterative algorithm (AIA) we propose a novel generalized phase shifting algorithm (GPSA), and here it is abbreviated as ETCI method. The phase distribution and phase shifts that extracted from randomly phase shifted interferograms by use of ETCI are more accurate and the whole process is far faster than AIA. Additionally, proposed method is less sensitive to non-uniform background intensity and modulation amplitude. Numerical simulations are conducted to evaluate the performance of ETCI, and some influential factors are elaborated. The experimental results further indicate proposed method is suitable for truly random phase shifted interferograms.
Etched-multilayer phase shifting masks for EUV lithography
Chapman, Henry N.; Taylor, John S.
2005-04-05
A method is disclosed for the implementation of phase shifting masks for EUV lithography. The method involves directly etching material away from the multilayer coating of the mask, to cause a refractive phase shift in the mask. By etching into the multilayer (for example, by reactive ion etching), rather than depositing extra material on the top of the multilayer, there will be minimal absorption loss associated with the phase shift.
Phase-Shift Interferometry with a Digital Photocamera
ERIC Educational Resources Information Center
Vannoni, Maurizio; Trivi, Marcelo; Molesini, Giuseppe
2007-01-01
A phase-shift interferometry experiment is proposed, working on a Twyman-Green optical configuration with additional polarization components. A guideline is provided to modern phase-shift interferometry, using concepts and laboratory equipment at the level of undergraduate optics courses. (Contains 5 figures.)
EUV phase-shifting masks and aberration monitors
NASA Astrophysics Data System (ADS)
Deng, Yunfei; Neureuther, Andrew R.
2002-07-01
Rigorous electromagnetic simulation with TEMPEST is used to examine the use of phase-shifting masks in EUV lithography. The effects of oblique incident illumination and mask patterning by ion-mixing of multilayers are analyzed. Oblique incident illumination causes streamers at absorber edges and causes position shifting in aerial images. The diffraction waves between ion-mixed and pristine multilayers are observed. The phase-shifting caused by stepped substrates is simulated and images show that it succeeds in creation of phase-shifting effects. The diffraction process at the phase boundary is also analyzed. As an example of EUV phase-shifting masks, a coma pattern and probe based aberration monitor is simulated and aerial images are formed under different levels of coma aberration. The probe signal rises quickly as coma increases as designed.
Achromatic phase shifts utilizing dielectric plates for nulling interferometery
NASA Astrophysics Data System (ADS)
Morgan, R. M.; Burge, J. M.
1998-12-01
Schemes for detecting planets around other stars using interferometery have been developed which rely on a half wave phase delay to shift the central constructive fringe of an interferometer to a deep, destructive null fringe. To achieve the sensitivity and spectroscopy desired for exo-planets observations, such a null must be achromatic over a broad spectral region. One method for creating such a half wave phase delay achromatically involves the use of pairs of dielectric, plane parallel plates, analogous to the use of two types of glass in an achromatic lens. An analysis of the technique is presented with solutions using single plates to achieve null fringes to a cancellation of 10 exp -4 in the visible, near infrared, and mid infrared for null. Solutions using two matched materials show that nulls to a depth of 10 exp -6 are achievable in 2 um bands in the 7-17 um regime, or to a depth of 10 exp -5 over the entire 7-17 um band. Experimental results using a single plate of BK7 in the visible spectrum verify the technique.
Cavity Attenuated Phase Shift-Based Monitoring of Atmospheric Species
NASA Astrophysics Data System (ADS)
Kebabian, P. L.; Onasch, T. B.; Herndon, S. C.; Wood, E. C.; Wormhoudt, J.; Freedman, A.
2009-06-01
We are developing compact instruments for the monitoring of ambient atmospheric species, specifically nitrogen dioxide and particles, using cavity attenuated phase shift spectroscopy. The sensor, which detects the optical absorption of nitrogen dioxide within a 20 nm bandpass band centered at 440 nm, comprises a blue light emitting diode, an enclosed metal measurement cell (26 cm in length) incorporating a resonant optical cavity of near-confocal design and a vacuum photodiode detector. An analog heterodyne detection scheme is used to measure the phase shift in the waveform of the modulated light transmitted through the cell induced by the presence of nitrogen dioxide and/or particles within the cell. The entire apparatus is encased within a standard 19-inch rack-mounted enclosure. Levels of detection (1 s, 3 σ ) for nitrogen dioxide of 0.2 ppb and for aerosols of 3.5 Mm^{-1} have been achieved. Examples of high resolution field measurements and comparisons with other instrumentation will be presented.
Application of principal component analysis in phase-shifting photoelasticity.
Quiroga, Juan A; Gómez-Pedrero, José A
2016-03-21
Principal component analysis phase shifting (PCA) is a useful tool for fringe pattern demodulation in phase shifting interferometry. The PCA has no restrictions on background intensity or fringe modulation, and it is a self-calibrating phase sampling algorithm (PSA). Moreover, the technique is well suited for analyzing arbitrary sets of phase-shifted interferograms due to its low computational cost. In this work, we have adapted the standard phase shifting algorithm based on the PCA to the particular case of photoelastic fringe patterns. Compared with conventional PSAs used in photoelasticity, the PCA method does not need calibrated phase steps and, given that it can deal with an arbitrary number of images, it presents good noise rejection properties, even for complicated cases such as low order isochromatic photoelastic patterns. PMID:27136792
Multiplicative phase-shifting interferometry using optical flow.
Vargas, J; Quiroga, J Antonio; Sorzano, C O S; Estrada, J C; Servín, M
2012-08-20
Fringe patterns with a multiplicative phase shift among them appear in experimental techniques as photoelasticity and RGB shadow moiré, among others. These patterns cannot be processed using standard phase-shifting demodulation techniques. In this work, we propose to use a multiframe regularized optical flow algorithm to obtain the interesting modulating phase. The proposed technique has been applied to simulated and experimental interferograms obtaining satisfactory results. PMID:22907020
Two-step phase-shifting fringe projection profilometry: intensity derivative approach
Yang Fujun; He Xiaoyuan
2007-10-10
A new two-step phase-shifting fringe projection profilometry is proposed. The slowly variable background intensity of fringe patterns is removed by the use of an intensity differential algorithm. The high-resolution differential algorithm is achieved based on global interpolation of fringe gray level on a subpixel scale. Compared with the traditional three- or four-step phase-shifting method, the profile measurement is sped up with this approach.Computer simulation and experimental performance are evaluated to demonstrate the validity of the proposed measurement method. The experimental results compared with those of the four-step phase-shifting method are presented.
Passive fathometer reflector identification with phase shift modeling.
Michalopoulou, Zoi-Heleni; Gerstoft, Peter
2016-07-01
In passive fathometer processing, the presence of wavelets in the estimate of the medium's Green's function corresponds to the location of reflectors in the seabed; amplitudes are related to seabed properties. Bayesian methods have been successful in identifying reflectors that define layer interfaces. Further work, however, revealed that phase shifts are occasionally present in the wavelets and hinder accurate layer identification for some reflectors. With a Gibbs sampler that computes probability densities of reflector depths, strengths of the reflections, and wavelet phase shifts, the significance of phase shift modeling in successful estimation of reflectors and their strengths is demonstrated. PMID:27475201
Process validation: achieving the Operational Qualification phase.
Buffaloe, Vera
2004-01-01
The OQ phase of process validation is very important and is where the complete understanding of the process is determined by experimentation. This understanding is useful to: * establish optimal process parameters * understand variation that affect the process * aid in investigating process deviations. OQ is an important part of the entire process validation activity and essential to understanding a manufacturing process. The benefits of completing the OQ and overall process validation are the reasons that it makes business sense and receive the long-term benefits of producing high quality product and achieving customer satisfaction. PMID:15521514
Coding for slow frequency hopped differential phase shift keying
NASA Astrophysics Data System (ADS)
Wang, Qiang; Gulliver, T. A.; Mason, Lloyd J.; Blake, Ian F.
The performance of Reed-Solomon (RS) error-correcting codes with slow frequency hopped (SFH) differential phase shift keying (DPSK) signaling is analyzed and evaluated under worst-case partial-band noise (PBN) and worst-case multitone (MT) jamming. The results of a study of the bit error rate (BER) performance of this coded system are presented. A representative set of the performance curves is shown. SFH is used because the differential signaling required only the phase of the previous received signal as a reference. Using DPSK eliminates the need to establish a phase reference for the hop, as with coherent signaling. From the results it is clear that the number of codeword symbols per hop must be small in order for the RS code to provide protection against jamming. Otherwise, no improvement over uncoded DPSK is gained. Lowering the symbols per hop can be achieved either by reducing the number of bits per hop, or interleaving the RS codewords to a depth determined by the hop length and RS code parameters.
Qiu, Xiang; Zhong, Liyun; Xiong, Jiaxiang; Zhou, Yunfei; Tian, Jindong; Li, Dong; Lu, Xiaoxu
2016-06-13
In simultaneous phase-shifting dual-wavelength interferometry, by matching both the phase-shifting period number and the fringe number in interferogram of two wavelengths to the integers, the phase with high accuracy can be retrieved through combining the principle component analysis (PCA) and least-squares iterative algorithm (LSIA). First, by using the approximate ratio of two wavelengths, we can match both the temporal phase-shifting period number and the spatial fringe number in interferogram of two wavelengths to the integers. Second, using above temporal and spatial hybrid matching condition, we can achieve accurate phase shifts of single-wavelength of phase-shifting interferograms through using PCA algorithm. Third, using above phase shifts to perform the iterative calculation with the LSIA method, the wrapped phases of single-wavelength can be determined. Both simulation calculation and experimental research demonstrate that by using the temporal and spatial hybrid matching condition, the PCA + LSIA based phase retrieval method possesses significant advantages in accuracy, stability and processing time. PMID:27410297
Differential phase shift of partially reflected radio waves.
NASA Technical Reports Server (NTRS)
Connolly, D. J.
1971-01-01
The addition of phase difference measurements to differential absorption experiments is shown to be both feasible and desirable. The phase information can provide a more sensitive measurement of electron density above about 75 km. The differential phase shift is only weakly dependent on collision frequency in this range, and so an accurate collision frequency profile is not a prerequisite. The differential phase shift and differential absorption measurements taken together can provide both electron density and collision frequency data from about 70 to 90 km.
Full 360 deg phase shifting of injection-locked oscillators
NASA Astrophysics Data System (ADS)
Zhang, Xiangdong; Daryoush, Afshin S.
1993-01-01
A novel design is presented to produce analog phase shifts of 0 deg to 360 deg in optically controlled oscillators which are subharmonically injection-locked. The proposed concept was analytically described and experimentally demonstrated by producing a 360 deg phase shift in an 8 GHz oscillator that is indirectly optically injection-locked to a 4 GHz subharmonic frequency. This design concept could eliminate the need for switched delay-line phase shifters in T/R modules of optically controlled phased array antennas, thus making the T/R module more compact and efficient.
Improving the accuracy of phase-shifting techniques
NASA Astrophysics Data System (ADS)
Cruz-Santos, William; López-García, Lourdes; Redondo-Galvan, Arturo
2015-05-01
The traditional phase-shifting profilometry technique is based on the projection of digital interference patterns and computation of the absolute phase map. Recently, a method was proposed that used phase interpolation to the corner detection, at subpixel accuracy in the projector image for improving the camera-projector calibration. We propose a general strategy to improve the accuracy in the search for correspondence that can be used to obtain high precision three-dimensional reconstruction. Experimental results show that our strategy can outperform the precision of the phase-shifting method.
Asymmetrical phase-shifted full-bridge
Fiedler, A.; Grotstollen, H.
1995-12-31
In comparison to forward-converters bridge topologies make use of parasitic components for resonant transition without need of additional clamping circuitry. Thus, they are privileged in building high frequency high power converters, even if high efficiency is required. This paper introduces a new modulation scheme for H-bridges, which combines PWM and phase-modulation. An analysis of the ideal circuit is presented together with design guidelines. Some experimental data for a converter prototype are given for 300V/5V--750W, 250 kHz.
Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics
NASA Astrophysics Data System (ADS)
Griffin, DeVon W.; Marshall, Keneth L.
2002-11-01
The initial focus of this project was to eliminate both of these problems in the Liquid Crystal Point-Diffraction Interferometer (LCPDI). Progress toward that goal will be described, along with the demonstration of a phase shifting Liquid Crystal Shearing Interferometer (LCSI) that was developed as part of this work. The latest LCPDI, other than a lens to focus the light from a test section onto a diffracting microsphere within the interferometer and a collimated laser for illumination, the pink region contained within the glass plates on the rod-mounted platform is the complete interferometer. The total width is approximately 1.5 inches with 0.25 inches on each side for bonding the electrical leads. It is 1 inch high and there are only four diffracting microspheres within the interferometer. As a result, it is very easy to align, achieving the first goal. The liquid crystal electro-optical response time is a function of layer thickness, with thinner devices switching faster due to a reduction in long-range viscoelastic forces between the LC molecules. The LCPDI has a liquid crystal layer thickness of 10 microns, which is controlled by plastic or glass microspheres embedded in epoxy 'pads' at the corners of the device. The diffracting spheres are composed of polystyrene/divinyl benzene polymer with an initial diameter of 15 microns. The spheres deform slightly when the interferometer is assembled to conform to the spacing produced by the microsphere-filled epoxy spacer pads. While the speed of this interferometer has not yet been tested, previous LCPDIs fabricated at the Laboratory for Laser Energetics switched at a rate of approximately 3.3 Hz, a factor of 10 slower than desired. We anticipate better performance when the speed of these interferometers is tested since they are approximately three times thinner. Phase shifting in these devices is a function of the AC voltage level applied to the liquid crystal. As the voltage increases, the dye in the liquid crystal
Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics
NASA Technical Reports Server (NTRS)
Griffin, DeVon W.; Marshall, Keneth L.
2002-01-01
The initial focus of this project was to eliminate both of these problems in the Liquid Crystal Point-Diffraction Interferometer (LCPDI). Progress toward that goal will be described, along with the demonstration of a phase shifting Liquid Crystal Shearing Interferometer (LCSI) that was developed as part of this work. The latest LCPDI, other than a lens to focus the light from a test section onto a diffracting microsphere within the interferometer and a collimated laser for illumination, the pink region contained within the glass plates on the rod-mounted platform is the complete interferometer. The total width is approximately 1.5 inches with 0.25 inches on each side for bonding the electrical leads. It is 1 inch high and there are only four diffracting microspheres within the interferometer. As a result, it is very easy to align, achieving the first goal. The liquid crystal electro-optical response time is a function of layer thickness, with thinner devices switching faster due to a reduction in long-range viscoelastic forces between the LC molecules. The LCPDI has a liquid crystal layer thickness of 10 microns, which is controlled by plastic or glass microspheres embedded in epoxy 'pads' at the corners of the device. The diffracting spheres are composed of polystyrene/divinyl benzene polymer with an initial diameter of 15 microns. The spheres deform slightly when the interferometer is assembled to conform to the spacing produced by the microsphere-filled epoxy spacer pads. While the speed of this interferometer has not yet been tested, previous LCPDIs fabricated at the Laboratory for Laser Energetics switched at a rate of approximately 3.3 Hz, a factor of 10 slower than desired. We anticipate better performance when the speed of these interferometers is tested since they are approximately three times thinner. Phase shifting in these devices is a function of the AC voltage level applied to the liquid crystal. As the voltage increases, the dye in the liquid crystal
Enhanced two-frequency phase-shifting method.
Hyun, Jae-Sang; Zhang, Song
2016-06-01
One of the major challenges of employing a two-frequency (or two-wavelength) phase-shifting algorithm for absolute three-dimensional shape measurement is its sensitivity to noise. Therefore, three- or more-frequency phase-shifting algorithms are often used in lieu of a two-frequency phase-shifting algorithm for applications where the noise is severe. This paper proposes a method to use geometric constraints of digital fringe projection system to substantially reduce the noise impact by allowing the use of more than one period of equivalent phase map for temporal phase unwrapping. Experiments successfully verified the enhanced performance of the proposed method without increasing the number of patterns. PMID:27411193
Phase-shifting point-diffraction interferometry at EUV wavelengths
Goldberg, K.A.; Tejnil, E.; Sang Lee
1997-04-01
A novel phase-shifting point-diffraction interferometer (PS/PDI) operating at the Advanced Light Source (ALS) is being used to perform wavefront-measuring metrology at 13.4-nm wavelength to characterize aberrations in a multilayer-coated 10x Schwarzschild objective designed for extreme ultraviolet (EUV) projection lithography experiments. To achieve 0.1-micron critical dimension pattern transfer with EUV projection lithography at 13.4-nm wavelength, nearly diffraction-limited all-reflective multilayer-coated optical systems with 0.1 numerical aperture are required. The EUV wavefront, determined by the mirror surfaces and the reflective multilayer coatings, is measurable only at the operational wavelength of the system. The authors goal is to measure the EUV wavefront to an accuracy of 0.01 waves rms (0.13 nm). The PS/PDI is a type of point-diffraction interferometer, modified for significantly improved throughput and phase-shifting capability. The interferometer design utilizes a grating beamsplitter and pinhole spatial filters in the object and image planes of the optical system under test. The 10x-reduction Schwarzschild objective, with image-side numerical aperture of 0.08, is illuminated by a sub-micron pinhole in the object plane. A coarse, 20-micron pitch grating placed between the illumination pinhole and the Schwarzschild system serves a dual role as a small-angle beam-splitter and a phase-shifting element. The first-order diffracted beam from the grating is spatially filtered in the image plane of the Schwarzschild with a sub-100-nm pinhole and becomes the `D reference` wave in the interferometer. The zero-order beam is the `test` wave, and it passes unobstructed through a 4.5-{mu}m window in the image plane. The test and reference beams are separated by several microns in the image plane to minimize beam overlap. The interference fringes are recorded with a CCD detector placed about 12 cm from the Schwarzschild image plane.
NASA Astrophysics Data System (ADS)
Barcelata-Pinzon, A.; Meneses Fabian, C.; Juarez-Salazar, R.; Durán-Sánchez, M.; Alvarez-Tamayo, R. I.; Robledo-Sánchez, C. I.; Muñoz-Mata, J. L.; Casco-Vázquez, J. F.
2016-05-01
Numerical results are presented to show the characterization of an electromechanical actuator capable to achieve equally spaced phase shifts and fraction linear wavelength displacements aided by an interface and a computational system. Measurements were performed by extracting the phase with consecutive interference patterns obtained in a Michelson arrangement setup. This paper is based in the use of inexpensive resources on stability adverse conditions to achieve similar results to those obtained with high-grade systems.
NASA Astrophysics Data System (ADS)
Sivakumar, N. R.; Tan, B.; Venkatakrishnan, K.
2006-01-01
In-process measurement has been the requirement of the precision industries, but due to vibrations while manufacturing, in-process measurement has been difficult to achieve. There is little work on in-process measurement using phase shifting interferometry, as phase shifting is extremely sensitive to vibrations. In this work, the advantage of the developed non-mechanical and instantaneous phase shifting interferometry is felt while measuring surface profile of large flat surfaces under vibrating conditions which can be extended for in-process measurement of surface profile. A near common path optical configuration is achieved and the effect of the environment is reduced. Moreover, the measurement of phase is instantaneous which increases the versatility of this technique for measuring vibrating objects. Profile measurements were carried out on a smooth mirror surface excited with vibrations of different frequencies and the technique was found to be immune to vibrations of up to 1000 Hz.
Toto-Arellano, Noel-Ivan; Rodriguez-Zurita, Gustavo; Meneses-Fabian, Cruz; Vazquez-Castillo, Jose F
2008-11-10
Among several techniques, phase shifting interferometry can be implemented with a grating used as a beam divider to attain several interference patterns around each diffraction order. Because each pattern has to show a different phase-shift, a suitable shifting technique must be employed. Phase gratings are attractive to perform the former task due to their higher diffraction efficiencies. But as is very well known, the Fourier coefficients of only-phase gratings are integer order Bessel functions of the first kind. The values of these real-valued functions oscillate around zero, so they can adopt negative values, thereby introducing phase shifts of pi at certain diffraction orders. Because this almost trivial fact seems to have been overlooked in the literature regarding its practical implications, in this communication such phase shifts are stressed in the description of interference patterns obtained with grating interferometers. These patterns are obtained by placing two windows in the object plane of a 4f system with a sinusoidal grating/grid in the Fourier plane. It is shown that the corresponding experimental observations of the fringe modulation, as well as the corresponding phase measurements, are all in agreement with the proposed description. A one-shot phase shifting interferometer is finally proposed taking into account these properties after proper incorporation of modulation of polarization. PMID:19582027
Correlated errors in phase-shifting laser Fizeau interferometry.
de Groot, Peter J
2014-07-01
High-performance data processing algorithms for phase-shifting interferometry accommodate adjustment errors in the phase shift increment as well as harmonic distortions in the interference signal. However, a widely overlooked error source is the combination of these two imperfections. Phase shift tuning errors increase the sensitivity of phase estimation algorithms to second-order and higher harmonics present in Fizeau interference signals. I derive an analytical formula for evaluating these errors more realistically, in part to identify the characteristics of the optimal PSI algorithm. Even for advanced algorithms, it is found that multiple reflections increase the error contribution of detuning by orders of magnitude compared with the two-beam calculation and impose a practical limit of 30% in tuning error for sub-nm metrology in a 4%-4% Fizeau cavity. Consequently, a preferred approach for high precision spherical cavities is to use either wavelength tuning in place of mechanical phase shifting or an iterative solver that accommodates unknown phase shifts as a function of field position. PMID:25089998
Voltage-controlled attenuator with low phase shift
NASA Technical Reports Server (NTRS)
Lutes, G. F., Jr.
1980-01-01
Five megahertz RF (radiofrequency) signal attenuator utilizing RF quadrature hybrid, and optically viable-resistance load controlled by lamp circuit exhibits little phase shift. Circuit is designed to help distribute standard RF signal of controlled amplitude, and phase throughout complex of facilities could be useful in application to precision test equipment and communication electronics.
Crosstalk Cancellation for a Simultaneous Phase Shifting Interferometer
NASA Technical Reports Server (NTRS)
Olczak, Eugene (Inventor)
2014-01-01
A method of minimizing fringe print-through in a phase-shifting interferometer, includes the steps of: (a) determining multiple transfer functions of pixels in the phase-shifting interferometer; (b) computing a crosstalk term for each transfer function; and (c) displaying, to a user, a phase-difference map using the crosstalk terms computed in step (b). Determining a transfer function in step (a) includes measuring intensities of a reference beam and a test beam at the pixels, and measuring an optical path difference between the reference beam and the test beam at the pixels. Computing crosstalk terms in step (b) includes computing an N-dimensional vector, where N corresponds to the number of transfer functions, and the N-dimensional vector is obtained by minimizing a variance of a modulation function in phase shifted images.
Phase-shifting real-time holography with photorefractive crystals
NASA Astrophysics Data System (ADS)
Gesualdi, M. R. R.; Soga, D.; Muramatsu, M.
2006-01-01
The phase-shifting interferometry techniques is a well-known technique which has been used with great success in optical profilers, micro-displacements, micro-deformations and others applications in Non-Destructive Test in basic research, engineering and biotechnology areas. This work presents our Advances in Phase-Shifting Real-Time Holography using Photorefractive Sillenite. And we have obtained quantitative results in many applications in measurements of micro-rotation, micro-displacements, deformation, surface contouring and whole lens wave-optics. The real-time holography process is doing using the photorefractive Bi 12SiO 20 crystal recording medium, where the phase-shifting 4-frames method for obtained the phase map, this was filtered by sin/cos filter and was applied the unwrapping process. The experimental results agree with the expected one in these applications and with promises potentialities of this method for studies with in situ visualization, monitoring and analysis.
Vibration-resistance technology of phase-shifting interferometry
NASA Astrophysics Data System (ADS)
Wu, Dong; Chen, Jinbang; Chen, Lei; Wu, Ziming; Lee, Wulantuya
2002-09-01
A vibration-resistance phase-shifting interferometer (PSI) was recently constructed and demonstrated. In this instrument, we have developed a method for actively compensating for vibration using a closed-loop phase servo system. An essential feature of this is phase modulating interference fringes fractionizing technology. This method can detect the fringe movement at 1/400 fringe interval, so fringes phase can be locked by the closed-loop feedback within 0.005 π. And the instrument implements phase shifting with the same piezoelectric transducer (PZT) that also compensates for vibration as feedback device. A microprogrammed control unit (MCU) is used to process phase information from photoelectric receiver, and then output the control signal to PZT driver. Experiments show that this solution is unique.
Can small shifts in circadian phase affect performance?
Burgess, Helen J.; Legasto, Carlo S.; Fogg, Louis F.; Smith, Mark R.
2012-01-01
Small shifts in circadian timing occur frequently as a result of daylight saving time or later weekend sleep. These subtle shifts in circadian phase have been shown to influence subjective sleepiness, but it remains unclear if they can significantly affect performance. In a retrospective analysis we examined performance on the Psychomotor Vigilance Test before bedtime and after wake time in 11 healthy adults on fixed sleep schedules based on their habitual sleep times. The dim light melatonin onset, a marker of circadian timing, was measured on two occasions. An average 1.1 hour shift away from a proposed optimal circadian phase angle (6 hours between melatonin onset and midpoint of sleep) significantly slowed mean, median and fastest 10% reaction times before bedtime and after wake time (p<0.05). These results add to previous reports that suggest that humans may be sensitive to commonly occurring small shifts in circadian timing. PMID:22695081
Fast pixel shifting phase unwrapping algorithm in quantitative interferometric microscopy
NASA Astrophysics Data System (ADS)
Xu, Mingfei; Shan, Yanke; Yan, Keding; Xue, Liang; Wang, Shouyu; Liu, Fei
2014-11-01
Quantitative interferometric microscopy is an important method for observing biological samples such as cells and tissues. In order to obtain continuous phase distribution of the sample from the interferogram, phase extracting and phase unwrapping are both needed in quantitative interferometric microscopy. Phase extracting includes fast Fourier transform method and Hilbert transform method, etc., almost all of them are rapid methods. However, traditional unwrapping methods such as least squares algorithm, minimum network flow method, etc. are time-consuming to locate the phase discontinuities which lead to low processing efficiency. Other proposed high-speed phase unwrapping methods always need at least two interferograms to recover final phase distributions which cannot realize real time processing. Therefore, high-speed phase unwrapping algorithm for single interferogram is required to improve the calculation efficiency. Here, we propose a fast phase unwrapping algorithm to realize high-speed quantitative interferometric microscopy, by shifting mod 2π wrapped phase map for one pixel, then multiplying the original phase map and the shifted one, then the phase discontinuities location can be easily determined. Both numerical simulation and experiments confirm that the algorithm features fast, precise and reliable.
Precise determination of lattice phase shifts and mixing angles
NASA Astrophysics Data System (ADS)
Lu, Bing-Nan; Lähde, Timo A.; Lee, Dean; Meißner, Ulf-G.
2016-09-01
We introduce a general and accurate method for determining lattice phase shifts and mixing angles, which is applicable to arbitrary, non-cubic lattices. Our method combines angular momentum projection, spherical wall boundaries and an adjustable auxiliary potential. This allows us to construct radial lattice wave functions and to determine phase shifts at arbitrary energies. For coupled partial waves, we use a complex-valued auxiliary potential that breaks time-reversal invariance. We benchmark our method using a system of two spin-1/2 particles interacting through a finite-range potential with a strong tensor component. We are able to extract phase shifts and mixing angles for all angular momenta and energies, with precision greater than that of extant methods. We discuss a wide range of applications from nuclear lattice simulations to optical lattice experiments.
Fourier transform infrared phase shift cavity ring down spectrometer
NASA Astrophysics Data System (ADS)
Schundler, Elizabeth; Mansur, David J.; Vaillancourt, Robert; Benedict-Gill, Ryan; Newbry, Scott P.; Engel, James R.; Rentz Dupuis, Julia
2013-05-01
We report on our current status towards the development of a prototype Fourier transform infrared phase shift cavity ring down spectrometer (FTIR-PS-CRDS) system under a U.S. EPA SBIR contract. Our system uses the inherent wavelength-dependent modulation imposed by the FTIR on a broadband thermal source for the phase shift measurement. This spectrally-dependent phase shift is proportional to the spectrally-dependent ring down time, which is proportional to the losses of the cavity including those due to molecular absorption. Our approach is a broadband and spectral range enhancement to conventional CRDS which is typically done in the near IR at a single wavelength; at the same time our approach is a sensitivity enhancement to traditional FTIR owing to the long effective path of the resonant cavity. In this paper we present a summary of the theory including performance projections and the design details of the prototype FTIR-PS-CRDS system.
In-plane displacement measurement using optical vortex phase shifting.
Sun, Haibin; Wang, Xinghai; Sun, Ping
2016-07-20
In this paper, we propose a new method for in-plane displacement measurement by application of phase shifting based on an optical vortex. The phase shifts are obtained by displaying computer-generated fork holograms on the screen of a liquid-crystal spatial light modulator (LC-SLM). Furthermore, the vortex beam that is generated by the LC-SLM can be used as a reference light in the experiment. Eight speckle patterns with phase-shift increments of 0, π/2, π, and 3π/2 were captured by a CCD camera before and after the deformation. The displacement of the deformed object was obtained by unwrapping. Experimental results demonstrated the efficacy of the proposed method for in-plane displacement measurement. PMID:27463914
An in situ method for diagnosing phase shifting interferometry
NASA Astrophysics Data System (ADS)
Shao, J.; Ma, D.; Zhang, H.; Xie, Y.
2016-05-01
Current diagnosing phase shifting interferometry is a time and funds consuming process. Hence a brief and effective method is necessary to satisfy the real-time testing. In this paper, mathematical solutions for errors were deduced from the difference of intensity patterns. Based on the diversity of error distributions, an effective method for distinguishing and diagnosing the error sources is proposed and verified by an elaborative designed simulation. In the actual comparison experiment, vibration, phase-shift error and intensity fluctuation were imposed to demonstrate this method. The results showed that this method can be applied into the real-time measurement and provide an in situ diagnosing technique.
Quantum-dot-induced phase shift in a pillar microcavity
Young, A. B.; Hu, C. Y.; Rarity, J. G.; Oulton, R.; Thijssen, A. C. T.; Schneider, C.; Reitzenstein, S.; Kamp, M.; Hoefling, S.; Worschech, L.; Forchel, A.
2011-07-15
We perform high-resolution reflection spectroscopy of a quantum dot resonantly coupled to a pillar microcavity. We show the change in reflectivity as the quantum dot is tuned through the cavity resonance and measure the quantum-dot-induced phase shift using an ultrastable interferometer. The macroscopic phase shift we measure could be extended to the study of charged quantum dot pillar microcavity systems, where it could be exploited to realize a high-efficiency spin photon interface for hybrid quantum information schemes.
Phase shifts of the paired wings of butterfly diagrams
NASA Astrophysics Data System (ADS)
Li, Ke-Jun; Liang, Hong-Fei; Feng, Wen
2010-11-01
Sunspot groups observed by the Royal Greenwich Observatory/US Air Force/NOAA from 1874 May to 2008 November and the Carte Synoptique solar filaments from 1919 March to 1989 December are used to investigate the relative phase shift of the paired wings of butterfly diagrams of sunspot and filament activities. Latitudinal migration of sunspot groups (or filaments) does asynchronously occur in the northern and southern hemispheres, and there is a relative phase shift between the paired wings of their butterfly diagrams in a cycle, making the paired wings spatially asymmetrical on the solar equator. It is inferred that hemispherical solar activity strength should evolve in a similar way within the paired wings of a butterfly diagram in a cycle, demonstrating the paired wings phenomenon and showing the phase relationship between the northern and southern hemispherical solar activity strengths, as well as a relative phase shift between the paired wings of a butterfly diagram, which should bring about almost the same relative phase shift of hemispheric solar activity strength.
Full phase-shifting methodology for 65-nm node lithography
NASA Astrophysics Data System (ADS)
Pierrat, Christophe; Driessen, Frank A. J. M.; Vandenberghe, Geert
2003-06-01
A new methodology for completely phase-shifting a poly layout without creating local phase conflicts was proposed for lithographic techniques combining one phase-shifting mask and one binary mask exposure1. Critical and non-critical areas of the layout are identified and phase conflicts are avoided by splitting the shifter regions from non-critical areas to non-critical areas without crossing critical areas. The out-of-phase splits of the shifter regions are removed using the binary exposure. Simulation results and experimental data collected for 90nm technology node show no sign of process latitude loss around the areas where the shifters are split. The overlay latitude is commensurate with 90nm technology scanner requirements (tool to itself). Simulation work shows that the two exposures are balancing each other out of focus in the 45-degree cut regions thus ensuring large focus latitude. The focus latitude reported is larger than the main feature process latitude; this result was confirmed experimentally. A set of phase-shifting design rules commensurate with an aggressive 65nm node technology (140nm pitch) was put together. Under these conditions, we have identified certain types of cuts that should be avoided during the generation of the phase-shifting layout; this is primarily the case for cuts in "elbow" structures which exhibit limited process latitude. Other cuts like line-end cuts will have to be modified. In this case we have proposed a side cut when the line-end is facing a perpendicular line with a minimum spacing. Despite these restrictions, test structures for the 65nm technology node were successfully converted with no phase conflicts. Experimental verification done on test structures using a 0.75 NA, 193nm scanner demonstrates 0.33 k1 capability using the full phase methodology.
Focus shift and process latitude of contact holes on attenuated phase-shifting masks
NASA Astrophysics Data System (ADS)
Wong, Alfred K. K.; Ferguson, Richard A.; Martino, Ronald M.; Neureuther, Andrew R.
1995-05-01
Focus shift and process latitude of contact features on both dark-field and light-field attenuated phase-shifting masks and binary intensity masks were examined using experimentally measured aerial images from the Ziess MSM-100 with IBM AIMS software, the scalar and thin-mask approximation in SPLAT, and the rigorous electromagnetic simulator TEMPEST. The dark-field attenuated phase-shifting mask (aPSM) contact holes show the most severe amount of focus shift, although the shift is not much different from that of space openings. Exposure latitude of dark field aPSM features shows a 12% improvement (from 33% to 45%) over conventional binary intensity mask. Depth-of-focus is also improved. under biasing of the mask features can also improve the process latitude of dark-field masks, whereas the contrary is true for light-field mask features. In general, the process latitude of light-field contact features is worse than that of dark-field features, indicating the need for positive deep-UV photoresist technology.
Filter-less frequency-doubling microwave signal generator with tunable phase shift
NASA Astrophysics Data System (ADS)
Li, Yueqin; Pei, Li; Li, Jing; Wang, Yiqun; Yuan, Jin
2016-07-01
A prototype for frequency-doubling microwave signal generator with tunable phase shift based on a filter-less architecture is proposed and analyzed. In the proposal, one dual parallel polarization modulator is used as the key component to generate two ±1st order sidebands along the orthogonal polarization directions with suppressed carrier. Then the polarization states of the two sidebands are aligned with the principal axes of an electro-optical phase modulator (EOPM). Tunable phase shift is implemented by controlling the direct current voltage applied to the EOPM. Without using any filters or wavelength-dependent components, the system possesses good frequency tunability and it can be applied to multi-wavelength operation. Taking advantage of the ability of frequency multiplication, the frequency tuning range can be wider than the operation bandwidth of the modulator. By theoretical analyses and simulated verifications, a frequency-doubling microwave signal ranging from 22 to 40 GHz with full range phase shift is achieved.
Singular-value demodulation of phase-shifted holograms.
Lopes, Fernando; Atlan, Michael
2015-06-01
We report on phase-shifted holographic interferogram demodulation by singular-value decomposition. Numerical processing of optically acquired interferograms over several modulation periods was performed in two steps: (1) rendering of off-axis complex-valued holograms by Fresnel transformation of the interferograms; and (2) eigenvalue spectrum assessment of the lag-covariance matrix of hologram pixels. Experimental results in low-light recording conditions were compared with demodulation by Fourier analysis, in the presence of random phase drifts. PMID:26030552
A Simple Ultrasonic Experiment Using a Phase Shift Detection Technique.
ERIC Educational Resources Information Center
Yunus, W. Mahmood Mat; Ahmad, Maulana
1996-01-01
Describes a simple ultrasonic experiment that can be used to measure the purity of liquid samples by detecting variations in the velocity of sound. Uses a phase shift detection technique that incorporates the use of logic gates and a piezoelectric transducer. (JRH)
Measurement and Calibration of PSD with Phase-shifting Interferometers
NASA Technical Reports Server (NTRS)
Lehan, J. P.
2008-01-01
We discuss the instrumental aspects affecting the measurement accuracy when determining PSD with phase shifting interferometers. These include the source coherence, optical train effects, and detector effects. The use of a carefully constructed calibration standard will also be discussed. We will end with a recommended measurement and data handling procedure.
Phase-shifting response to light in older adults
Kim, Seong Jae; Benloucif, Susan; Reid, Kathryn Jean; Weintraub, Sandra; Kennedy, Nancy; Wolfe, Lisa F; Zee, Phyllis C
2014-01-01
Abstract Age-related changes in circadian rhythms may contribute to the sleep disruption observed in older adults. A reduction in responsiveness to photic stimuli in the circadian timing system has been hypothesized as a possible reason for the advanced circadian phase in older adults. This project compared phase-shifting responses to 2 h of broad-spectrum white light at moderate and high intensities in younger and older adults. Subjects included 29 healthy young (25.1 ± 4.1 years; male to female ratio: 8: 21) and 16 healthy older (66.5 ± 6.0 years; male to female ratio: 5: 11) subjects, who participated in two 4-night and 3-day laboratory stays, separated by at least 3 weeks. Subjects were randomly assigned to one of three different time-points, 8 h before (−8), 3 h before (−3) or 3 h after (+3) the core body temperature minimum (CBTmin) measured on the baseline night. For each condition, subjects were exposed in a randomized order to 2 h light pulses of two intensities (2000 lux and 8000 lux) during the two different laboratory stays. Phase shifts were analysed according to the time of melatonin midpoint on the nights before and after light exposure. Older subjects in this study showed an earlier baseline phase and lower amplitude of melatonin rhythm compared to younger subjects, but there was no evidence of age-related changes in the magnitude or direction of phase shifts of melatonin midpoint in response to 2 h of light at either 2000 lux or 8000 lux. These results indicate that the acute phase-shifting response to moderate- or high-intensity broad spectrum light is not significantly affected by age. PMID:24144880
A novel phase shift technique in shearography for NDT
NASA Astrophysics Data System (ADS)
Liu, Z.; Gao, J.
2010-06-01
Digital shearography (DS) is a whole-field non-contacting optical method for nondestructive testing (NDT) of subsurface flaws and strain measurement. In this paper, we describe a novel phaseshifting technique in DS for nondestructive evaluation (NDE) and NDT of quasi dynamic behaviour of objects subject to varying loads. A Wollaston lens, a precise wave plate device and a polariser are employed to introduce constant phase differences between two shearing wavefronts. The wave plate device is in front of the polariser, which has a transmissive wavefront distortion of less than 1/8 wavelength. Phase difference can be adjusted by rotating the polariser. The rotation for angle adjusting can be easily carried out according to the requirement of the phase shifting. In this technique, the phase shifting is performed only on the static images of the object before deformation or loading. By setting the angle of the polariser to 0º, -60º and 60º, three speckle patterns with the defined phase differences are captured, and are referred to as initial speckle patterns I1,0, I1,-60 and I1,60. Afterwards, the polariser is reset to 0º before loading. The speckle pattern I0 is treated as a base pattern, and will be subtracted from the subsequent speckle patterns which are captured in the quasi dynamic deformation process. During the quasi dynamic deformation process, the optical path and the entire optical set-up will be kept unchanged, and a series of speckle patterns (Im,0, m=2,3,…..) which carry the deformation information will be quickly captured. In the meantime, fast image subtractions will be performed. The speckle fringes (Im,0 -I1,0) will be displayed in real-time. In detailed post-processing, phase of differences method (PDM) [1] is used to extract phase information from the speckle images Im,0 -I1,0, I1,0, I1,-60 and I1,60. Specifically, when a three phase step technique is employed, the phase of the fringe pattern (Im,0-I1,0) can be calculated from (Im,0 -I1,0)+ I1
Shifted cosmological parameter and shifted dust matter in a two-phase tachyonic field universe
NASA Astrophysics Data System (ADS)
Verma, Murli Manohar; Pathak, Shankar Dayal
2013-04-01
We propose a model of the evolution of the tachyonic scalar field over two phases in the universe. The field components do not interact in phase I, while in the subsequent phase II, they change flavours due to relative suppression of the radiation contribution. In phase II, we allow them to interact mutually with time-independent perturbation in their equations of state, as Shifted Cosmological Parameter (SCP) and Shifted Dust Matter (SDM). We determine the solutions of their scaling with the cosmic redshift in both phases. We further suggest the normalised Hubble function diagnostic, which, together with the low- and high-redshift H( z) data and the concordance values of the present density parameters from the CMBR, BAO statistics etc., constrain the strength of interaction by imposing the viable conditions to break degeneracy in 3-parameter (γ, \\varepsilon, dot{φ}2) space. The range of redshifts ( z=0.1 to z=1.75) is chosen to highlight the role of interaction during structure formation, and it may lead to a future analysis of power spectrum in this model vis a vis Warm Dark Matter (WDM) or ΛCDM models. We further calculate the influence of interaction in determining the age of the universe at the present epoch, within the degeneracy space of model parameters.
Melamine detection using phase-shift fiber-loop ring-down spectroscopy
NASA Astrophysics Data System (ADS)
Zhou, Xinlei; Wang, Xinhui; Chen, Ke; Mao, Xuefeng; Peng, Wei; Yu, Qingxu
2014-12-01
Melamine is an illegal adulteration in milk, infant formula and pet food. Its misuse is toxic to humans and animals, so rapid and reliable screening methods for melamine detection are essential. In this paper, a phase-shift fiber-loop ring-down spectroscopy (PS-FLRDS)-based system is developed and evaluated for the detection and quantification of melamine. In the PS-FLRDS technique, an intensity-modulated continuous-wave (CW) laser is used as the light source, and a phase shift between the incident and emitted light of the fiber loop is introduced due to losses caused by the fiber loop and absorbing sample. By measuring this phase shift, one can readily obtain the concentration information of the measured species. Phase shifts of melamine solutions with different concentrations are measured and the experimental results show that there is a good linear relationship between the phase shift and the melamine concentration in low concentration range and a detection limit of 0.03 mg/mL has been achieved.
Phase-shifted helical long-period grating-based temperature-insensitive optical fiber twist sensors
NASA Astrophysics Data System (ADS)
Gao, Ran; Zhu, Yinian; Krishnaswamy, Sridhar; Yi, Jiang
2015-03-01
In smart structure monitoring, twist angle is one of the most critical mechanical parameters for infrastructure deterioration. A compact temperature-insensitive optical fiber twist sensor based on multi-phase-shifted helical long period fiber grating has been proposed and experimentally demonstrated in this paper. A multi-phase-shifted helical long period fiber grating is fabricated with a multi-period rotation technology. A π / 2 and a 3π / 2 phase shift is introduced in the helical long period fiber grating by changing the period. The helical pitch can be effectively changed with a different twist rate, which is measured by calculating the wavelength difference between two phase shift peaks. Although the wavelength of the phase shift peak also shifts with a change of the temperature, the wavelength difference between two phase shift peaks is constant due to two fixed phase shifts in the helical long period fiber grating, which is extremely insensitive to temperature change for the multi-phase-shifted helical long period fiber grating. The experimental results show that a sensitivity of up to 1.959 nm/(rad/m) is achieved.
Phase shift reflectometry for sub-surface defect detection
NASA Astrophysics Data System (ADS)
Asundi, Anand; Lei, Huang; Eden, Teoh Kang Min; Sreemathy, Parthasarathy; May, Watt Sook
2012-11-01
Phase Shift Reflectometry has recently been seen as a novel alternative to interferometry since it can provide warpage measurement over large areas with no need for large optical components. To confirm its capability and to explore the use of this method for sub-surface defect detection, a Chinese magic mirror is used. This bronze mirror which dates back to the Chinese Han Dynasty appears at first sight to be an ordinary convex mirror. However, unlike a normal mirror, when illuminated by a beam of light, an image is formed onto a screen. It has been hypothesized that there are indentations inside the mirror which alter the path of reflected light rays and hence the reflected image. This paper explores various methods to measure these indentations. Of the methods test Phase Shift Reflectometry (PSR) was found suitable to be the most suitable both in terms of the sensitivity and the field of view.
Phase-shifting point diffraction interferometer mask designs
Goldberg, Kenneth Alan
2001-01-01
In a phase-shifting point diffraction interferometer, different image-plane mask designs can improve the operation of the interferometer. By keeping the test beam window of the mask small compared to the separation distance between the beams, the problem of energy from the reference beam leaking through the test beam window is reduced. By rotating the grating and mask 45.degree., only a single one-dimensional translation stage is required for phase-shifting. By keeping two reference pinholes in the same orientation about the test beam window, only a single grating orientation, and thus a single one-dimensional translation stage, is required. The use of a two-dimensional grating allows for a multiplicity of pinholes to be used about the pattern of diffracted orders of the grating at the mask. Orientation marks on the mask can be used to orient the device and indicate the position of the reference pinholes.
Terahertz single-shot quadrature phase-shifting interferometry.
Földesy, Péter
2012-10-01
A single-shot quadrature phase-shifting interferometry architecture is presented that is applicable to antenna coupled detector technologies. The method is based on orthogonally polarized object and reference beams and on linear and circular polarization sensitive antennas in space-division multiplexing. The technique can be adapted to two-, three-, and four-step and Gabor holography recordings. It is also demonstrated that the space-division multiplexing does not necessarily cause sparse sampling. A sub-THz detector array is presented containing multiple on-chip antennas and FET plasma wave detectors implemented in a 90 nm complementary metal-oxide semiconductor technology. As an example, two-step phase-shifting reconstruction results are given at 360 GHz. PMID:23027273
Coded octal phase shift keying in TDMA satellite communications
NASA Astrophysics Data System (ADS)
Rhodes, S. A.; Fang, R. J.; Chang, P. Y.
The coded octal phase shift-keying (coded OPSK) signalling technique that has been proposed for TDMA satellite communications is presently subjected to a performance assessment for forward error correction (FEC) codes of different complexities. With the maximum likelihood path decoder, coded OPSK provides a coding gain relative to the performance of uncoded quaternary phase shift keying (QPSK). Significant coding gains of coded OPSK were obtained, relative to uncoded QPSK, for both an AWGN channel and a simulated INTELSAT V channel. Computer simulations have demonstrated that, for an FEC code of 64 states, coded OPSK transmitted over an AWGN channel yields a coding gain of about 3 dB and 4 dB at two different bit error probabilities. Corresponding coding gains for coded OPSK transmitted over the INTELSAT V channel were 3.2 dB and 4.5, at the same two bit error probability values.
EEG alpha phase shifts during transition from wakefulness to drowsiness.
Kalauzi, Aleksandar; Vuckovic, Aleksandra; Bojić, Tijana
2012-12-01
Phases of alpha oscillations recorded by EEG were typically studied in the context of event or task related experiments, rarely during spontaneous alpha activity and in different brain states. During wake-to-drowsy transition they change unevenly, depending on the brain region. To explore their dynamics, we recorded ten adult healthy individuals in these two states. Alpha waves were treated as stable frequency and variable amplitude signals with one carrier frequency (CF). A method for calculating their CF phase shifts (CFPS) and CF phase potentials (CFPP) was developed and verified on surrogate signals as more accurate than phase shifts of Fourier components. Probability density estimate (PDE) of CFPS, CFPP and CF phase locking showed that frontal and fronto-temporal areas of the cortex underwent more extensive changes than posterior regions. The greatest differences were found between pairs of channels involving F7, F8, F3 and F4 (PDE of CFPS); F7, F8, T3 and T4 (CFPP); F7, F8, F3, F4, C3, C4 and T3 (decrease in CF phase locking). A topographic distribution of channels with above the average phase locking in the wake state revealed two separate regions occupying anterior and posterior brain areas (with intra regional and inter hemispheric connections). These regions merged and became mutually phase locked longitudinally in the drowsy state. Changes occurring primarily in the frontal and fronto-temporal regions correlated with an early decrease of alertness. Areas of increased phase locking might be correlated with topography of synchronous neuronal assemblies conceptualized within neural correlates of consciousness. PMID:22580156
Nonlocal nonlinear refraction in Hibiscus sabdariffa with large phase shifts.
Ramírez-Martínez, D; Alvarado-Méndez, E; Trejo-Durán, M; Vázquez-Guevara, M A
2014-10-20
In this work we present a study of nonlinear optical properties in organic materials (hibiscus sabdariffa). Our results demonstrate that the medium exhibits a highly nonlocal nonlinear response. We show preliminary numerical results of the transmittance as nonlocal response by considering, simultaneously, the nonlinear absorption and refraction in media. Numerical results are accord to measurement obtained by Z- scan technique where we observe large phase shifts. We also analyze the far field diffraction ring patterns of the sample. PMID:25401548
Phase-shifting point diffraction interferometer grating designs
Naulleau, Patrick; Goldberg, Kenneth Alan; Tejnil, Edita
2001-01-01
In a phase-shifting point diffraction interferometer, by sending the zeroth-order diffraction to the reference pinhole of the mask and the first-order diffraction to the test beam window of the mask, the test and reference beam intensities can be balanced and the fringe contrast improved. Additionally, using a duty cycle of the diffraction grating other than 50%, the fringe contrast can also be improved.
Pixelated mask spatial carrier phase shifting interferometry algorithms and associated errors
Kimbrough, Bradley T
2006-07-01
In both temporal and spatial carrier phase shifting interferometry, the primary source of phase calculation error results from an error in the relative phase shift between sample points. In spatial carrier phase shifting interferometry, this phase shifting error is caused directly by the wave front under test and is unavoidable. In order to minimize the phase shifting error, a pix elated spatial carrier phase shifting technique has been developed by 4D technologies. This new technique allows for the grouping of phase shifted pixels together around a single point in two dimensions,minimizing the phase shift change due to the spatial variation in the test wavefront. A formula for the phase calculation error in spatial carrier phase shifting interferometry is derived. The error associated with the use of linear N-point averaging algorithms is presented and compared with those of the pix elated spatial carrier technique.
Frequency domain phase retrieval of simultaneous multi-wavelength phase-shifting interferometry
NASA Astrophysics Data System (ADS)
Yin, Zhenxing; Zhong, Liyun; Xu, Xiaofei; Zhang, Wangping; Tian, Jindong; Lu, Xiaoxu
2016-05-01
In simultaneous multi-wavelength phase-shifting interferometry, we propose a novel frequency domain phase retrieval (FDPR) algorithm. First, using only a one-time phase-shifting operation, a sequence of simultaneous multi-wavelength phase-shifting interferograms (SPSMWIs) are captured by a monochrome charge-coupled device. Second, by performing a Fourier transform for each pixel of SPSMWIs, the wrapped phases of each wavelength can be retrieved from the complex amplitude located in the spectral peak of each wavelength. Finally, the phase of the synthetic wavelength can be obtained by the subtraction between the wrapped phases of a single wavelength. In this study, the principle and the application condition of the proposed approach are discussed. Both the simulation and the experimental result demonstrate the simple and convenient performance of the proposed FDPR approach.
Two-wavelength phase shift interferometry to characterize ballistic features
NASA Astrophysics Data System (ADS)
Pagano, Glenn W.; Mann, Christopher J.
2014-05-01
We apply two-wavelength phase shifting interferometry to generate 3D surface profile maps of spent bullet cartridge cases. From the captured interferograms, an optimized algorithm was used to calculate a phase profile from which a precise digital surface map of the cartridge casing may be produced. This 3D surface profile is used to enhance a firearms examiner's ability to uniquely identify distinct features or toolmarks imprinted on the casing when the weapon is fired. These features play a key role in the matching process of ballistic forensic examination.
Fourier transform infrared phase shift cavity ring down spectrometer
NASA Astrophysics Data System (ADS)
Schundler, Elizabeth; Mansur, David J.; Vaillancourt, Robert; Benedict-Gill, Ryan; Newbry, Scott P.; Engel, James R.; Dupuis, Julia Rentz
2014-05-01
OPTRA has developed a Fourier transform infrared phase shift cavity ring down spectrometer (FTIR-PS-CRDS) system under a U.S. EPA SBIR contract. This system uses the inherent wavelength-dependent modulation imposed by the FTIR on a broadband thermal source for the phase shift measurement. This spectrally-dependent phase shift is proportional to the spectrally-dependent ring down time. The spectral dependence of both of these values is introduced by the losses of the cavity including those due to the molecular absorption of the sample. OPTRA's approach allows broadband detection of chemicals across the feature-rich fingerprint region of the long-wave infrared. This represents a broadband and spectral range enhancement to conventional CRDS which is typically done at a single wavelength in the near IR; at the same time the approach is a sensitivity enhancement to traditional FTIR, owing to the long effective path of the resonant cavity. In previous papers1,2, OPTRA has presented a breadboard system aimed at demonstrating the feasibility of the approach and a prototype design implementing performance enhancements based on the results of breadboard testing. In this final paper in the series, we will present test results illustrating the realized performance of the fully assembled and integrated breadboard, thereby demonstrating the utility of the approach.
NASA Astrophysics Data System (ADS)
Montagut, Y. J.; García, J. V.; Jiménez, Y.; March, C.; Montoya, A.; Arnau, A.
2011-06-01
The improvement of sensitivity in quartz crystal microbalance (QCM) applications has been addressed in the last decades by increasing the sensor fundamental frequency, following the increment of the frequency/mass sensitivity with the square of frequency predicted by Sauerbrey. However, this sensitivity improvement has not been completely transferred in terms of resolution. The decrease of frequency stability due to the increase of the phase noise, particularly in oscillators, made impossible to reach the expected resolution. A new concept of sensor characterization at constant frequency has been recently proposed. The validation of the new concept is presented in this work. An immunosensor application for the detection of a low molecular weight contaminant, the insecticide carbaryl, has been chosen for the validation. An, in principle, improved version of a balanced-bridge oscillator is validated for its use in liquids, and applied for the frequency shift characterization of the QCM immunosensor application. The classical frequency shift characterization is compared with the new phase-shift characterization concept and system proposed.
Montagut, Y J; García, J V; Jiménez, Y; March, C; Montoya, A; Arnau, A
2011-06-01
The improvement of sensitivity in quartz crystal microbalance (QCM) applications has been addressed in the last decades by increasing the sensor fundamental frequency, following the increment of the frequency/mass sensitivity with the square of frequency predicted by Sauerbrey. However, this sensitivity improvement has not been completely transferred in terms of resolution. The decrease of frequency stability due to the increase of the phase noise, particularly in oscillators, made impossible to reach the expected resolution. A new concept of sensor characterization at constant frequency has been recently proposed. The validation of the new concept is presented in this work. An immunosensor application for the detection of a low molecular weight contaminant, the insecticide carbaryl, has been chosen for the validation. An, in principle, improved version of a balanced-bridge oscillator is validated for its use in liquids, and applied for the frequency shift characterization of the QCM immunosensor application. The classical frequency shift characterization is compared with the new phase-shift characterization concept and system proposed. PMID:21721715
Lemmel, Hartmut; Wagh, Apoorva G.
2010-09-15
A phase shifter in neutron interferometry creates not only a phase shift but also a spatial displacement of the neutron wave packet, leading to a reduced interference contrast. This wave-packet displacement constitutes a major hindrance in measuring large phase shifts. Here we present a nondispersive configuration with two identical phase shifters placed on one path in successive gaps of a symmetric triple Laue (LLL) interferometer. As compared to a single phase shifter, the dual phase shifter generates double the phase shift, yet a net null displacement of the wave packet. The interferometer thus remains fully focused however large the phase shift or the incident wavelength spread, permitting a white incident neutron beam as in the case of a purely topological phase measurement. Misalignment angles of a monolithic nondispersive dual phase shifter are equal and opposite in the two gaps. Its phase therefore remains nondispersive over a much wider angular range and attains a minimum magnitude at the correct orientation, obviating the need to alternate the phase shifter between the two interferometer paths during its alignment. The setup is hence ideally suited for measuring neutron coherent scattering lengths to ultrahigh precision.
Phase shift facilitation following cyclone disturbance on coral reefs.
Roff, George; Doropoulos, Christopher; Zupan, Mirta; Rogers, Alice; Steneck, Robert S; Golbuu, Yimnang; Mumby, Peter J
2015-08-01
While positive interactions have been observed to influence patterns of recruitment and succession in marine and terrestrial plant communities, the role of facilitation in macroalgal phase shifts is relatively unknown. In December 2012, typhoon Bopha caused catastrophic losses of corals on the eastern reefs of Palau. Within weeks of the typhoon, an ephemeral bloom of monospecific macroalgae (Liagora sp.) was observed, reaching a peak of 38.6% cover in February 2013. At this peak, we observed a proliferation of a second macroalgal species, Lobophora variegata. Lobophora was distributed non-randomly, with higher abundances occurring within the shelter of Liagora canopies than on exposed substrates. Bite rates of two common herbivorous fish (Chlorurus sordidus and Ctenochaetus striatus) were significantly higher outside canopies (2.5- and sixfold, respectively), and cage exclusion resulted in a significant increase in Lobophora cover. Experimental removal of Liagora canopies resulted in a 53.1% decline in the surface area of Lobophora after 12 days, compared to a 51.7% increase within canopies. Collectively, these results indicate that Liagora canopies act as ecological facilitators, providing a 'nursery' exclusion zone from the impact of herbivorous fish, allowing for the establishment of understory Lobophora. While the ephemeral Liagora bloom had disappeared entirely 9 months post-typhoon, the facilitated shift to Lobophora has persisted for over 18 months, dominating ~40% of the reef substrate. While acute disturbance events such as typhoons have been suggested as a mechanism to reverse algal phase shifts, our results suggest that typhoons may also trigger, rather than just reverse, phase shifts. PMID:25761445
Phase-Shifting Liquid Crystal Point-Diffraction Interferometry
NASA Technical Reports Server (NTRS)
Griffin, DeVon W.; Marshall, Kenneth L.; Mercer, Carolyn R.
2000-01-01
, the limited spatial resolution and the methods required for data reduction suggest that a more useful instrument needs to be developed. The category of interferometers known as common path interferometers can eliminate much of the vibration sensitivity associated with traditional interferometry as described above. In these devices, division of the amplitude of the wavefront following the test section produces the reference beam. Examples of these instruments include shearing and point diffraction interferometers. In the latter case, shown schematically, a lens focuses light passing through the test section onto a small diffracting object. Such objects are typically either a circle of material on a high quality glass plate or a small sphere in a glass cell. The size of the focused spot is several times larger than the object so that the light not intercepted by the diffracting object forms the test beam while the diffracted light generates a spherical reference beam. While this configuration is mechanically stable, phase shifting one beam with respect to the other is difficult due to the common path. Phase shifting enables extremely accurate measurements of the phase of the interferogram using only gray scale intensity measurements and is the de facto standard of industry. Mercer and Creath 2 demonstrated phase shifting in a point diffraction interferometer using a spherical spacer in a liquid crystal cell as the diffracting object. By changing the voltage across the cell, they were able to shift the phase of the undiffracted beam relative to the reference beam generated by diffraction from the sphere. While they applied this technology to fluid measurements, the device shifted phase so slowly that it was not useful for studying transient phenomena. We have identified several technical problems that precluded operation of the device at video frame rates and intend to solve them to produce a phase-shifting liquid crystal point-diffraction interferometer operating at
Phase error analysis and compensation for phase shifting profilometry with projector defocusing.
Zheng, Dongliang; Da, Feipeng; Kemao, Qian; Seah, Hock Soon
2016-07-20
Phase shifting profilometry (PSP) using binary fringe patterns with projector defocusing is promising for high-speed 3D shape measurement. To obtain a high-quality phase, the projector usually requires a high defocusing level, which leads to a drastic fall in fringe contrast. Due to its convenience and high speed, PSP using squared binary patterns with small phase shifting algorithms and slight defocusing is highly desirable. In this paper, the phase accuracies of the classical phase shifting algorithms are analyzed theoretically, and then compared using both simulation and experiment. We also adapt two algorithms for PSP using squared binary patterns, which include a Hilbert three-step PSP and a double three-step PSP. Both algorithms can increase phase accuracy, with the latter featuring additional invalid point detection. The adapted algorithms are also compared with the classical algorithms. Based on our analysis and comparison results, proper algorithm selection can be easily made according to the practical requirement. PMID:27463929
Bloemhof, E E
2010-07-15
Surface measurements of precision optics are commonly made with commercially available phase-shifting Fizeau interferometers that provide data relative to flat or spherical reference surfaces whose unknown errors are comparable to those of the surface being tested. A number of ingenious techniques provide surface measurements that are "absolute," rather than relative to any reference surface. Generally, these techniques require numerous measurements and the introduction of additional surfaces, but still yield absolute information only along certain lines over the surface of interest. A very simple alternative is presented here, in which no additional optics are required beyond the surface under test and the transmission flat (or sphere) defining the interferometric reference surface. The optic under test is measured in three positions, two of which have small lateral shifts along orthogonal directions, nominally comparable to the transverse spatial resolution of the interferometer. The phase structure in the reference surface then cancels out when these measurements are subtracted in pairs, providing a grid of absolute surface height differences between neighboring resolution elements of the surface under test. The full absolute surface, apart from overall phase and tip/tilt, is then recovered by standard wavefront reconstruction techniques. PMID:20634825
Photonic radio frequency phase-shift amplification by radio frequency interferometry.
Ayun, Moshe Ben; Schwarzbaum, Arye; Rosenberg, Seva; Pinchas, Monika; Sternklar, Shmuel
2015-11-01
We present a new technique for radio frequency (RF) phase-shift amplification based on RF interferometry and demonstrate it in an optical system. A striking feature of this amplifier is that the input phase noise is not amplified together with the input phase signal, so the phase sensitivity improves with higher phase amplification. We also predict that in the case of correlated amplitude noise, the sensitivity is not affected by the amplitude noise. With 600 MHz of modulated light and a phase amplification of 100, we demonstrate a phase resolution of 0.2 mrad, giving a distance resolution of 8 μm. We postulate that nanometric distance resolution can be achieved with sub-gigahertz modulation. PMID:26512469
Binary encoded computer generated holograms for temporal phase shifting.
Amphawan, Angela
2011-11-01
The trend towards real-time optical applications predicates the need for real-time interferometry. For real-time interferometric applications, rapid processing of computer generated holograms is crucial as the intractability of rapid phase changes may compromise the input to the system. This paper introduces the design of a set of binary encoded computer generated holograms (CGHs) for real-time five-frame temporal phase shifting interferometry using a binary amplitude spatial light modulator. It is suitable for portable devices with constraints in computational power. The new set of binary encoded CGHs is used for measuring the phase of the generated electric field for a real-time selective launch in multimode fiber. The processing time for the new set of CGHs was reduced by up to 65% relative to the original encoding scheme. The results obtained from the new interferometric technique are in good agreement with the results obtained by phase shifting by means of a piezo-driven flat mirror. PMID:22109188
Phase shifting two coupled circadian pacemakers - Implications for jet lag
NASA Technical Reports Server (NTRS)
Gander, P. H.; Kronauer, R. E.; Graeber, R. C.
1985-01-01
Two Van der Pol oscillators with reciprocal linear velocity coupling are utilized to model the response of the human circadian timing system to abrupt displacements of the environmental time cues (zeitgebers). The core temperature rhythm and sleep-wake cycle simulated by the model are examined. The relationship between the masking of circadian rhythms by environmental variables and behavioral and physiological events and the rates of resynchronization is studied. The effects of zeitgeber phase shifts and zeitgeber strength on the resynchronization rates are analyzed. The influence of intrinsic pacemakers periods and coupling strength on resynchronization are investigated. The simulated data reveal that: resynchronization after a time zone shift depends on the magnitude of the shift; the time of day of the shift has little influence on resynchronization; the strength of zeitgebers affects the rate and direction of the resynchronization; the intrinsic pacemaker periods have a significant effect on resynchronization; and increasing the coupling between the oscillators results in an increase in the rate of resynchronization. The model data are compared to transmeridian flight studies data and similar resynchronization patterns are observed.
Optoelectronic information encryption with phase-shifting interferometry.
Tajahuerce, E; Matoba, O; Verrall, S C; Javidi, B
2000-05-10
A technique that combines the high speed and the high security of optical encryption with the advantages of electronic transmission, storage, and decryption is introduced. Digital phase-shifting interferometry is used for efficient recording of phase and amplitude information with an intensity recording device. The encryption is performed by use of two random phase codes, one in the object plane and another in the Fresnel domain, providing high security in the encrypted image and a key with many degrees of freedom. We describe how our technique can be adapted to encrypt either the Fraunhofer or the Fresnel diffraction pattern of the input. Electronic decryption can be performed with a one-step fast Fourier transform reconstruction procedure. Experimental results for both systems including a lensless setup are shown. PMID:18345139
Accuracy enhancement of three-dimensional reconstruction using phase-shifting shadow moiré
NASA Astrophysics Data System (ADS)
Jamali Avilagh, Ali; Rezaie, Amir Hossein
2013-04-01
An iterative algorithm and a denoising method for accuracy enhancement of three-dimensional (3-D) reconstruction processes by shadow moiré is proposed. Using traditional shadow moiré for 3-D reconstruction leads to a nonuniform phase shift error. The proposed iterative algorithm eliminates this error by using three phase-shifted interferograms and obtains precise phase information. Moreover the proposed denoising method, which is based on undecimated wavelet transform, effectively eliminates noise and grating patterns while retaining useful information. The proposed phase shifting shadow moiré method is compared with the structured lighting method, which is a common method for 3-D reconstruction, and it is further compared with traditional shadow moiré. The methods are simulated in a 3ds-Max environment. The simulation results show that the proposed shadow moiré technique achieves greater accuracy in comparison with the traditional shadow moiré and structured lighting techniques and also it has higher accuracy than existing typical phase-shifting algorithms.
Application of ANFIS to Phase Estimation for Multiple Phase Shift Keying
NASA Technical Reports Server (NTRS)
Drake, Jeffrey T.; Prasad, Nadipuram R.
2000-01-01
The paper discusses a novel use of Adaptive Neuro-Fuzzy Inference Systems (ANFIS) for estimating phase in Multiple Phase Shift Keying (M-PSK) modulation. A brief overview of communications phase estimation is provided. The modeling of both general open-loop, and closed-loop phase estimation schemes for M-PSK symbols with unknown structure are discussed. Preliminary performance results from simulation of the above schemes are presented.
Differential-phase-shift quantum key distribution with phase modulation to combat sequential attacks
Kawahara, Hiroki; Oka, Toru; Inoue, Kyo
2011-11-15
Phase-modulated differential-phase-shift (DPS) quantum key distribution (QKD) is presented for combating sequential attacks that most severely restrict the DPS-QKD system distance. Slow phase modulation imposed onto the DPS signal obstructs the optimum unambiguous state discrimination measurement conducted in the sequential attack and improves the QKD distance as a result. The condition with which the phase modulation does not degrade the DPS-QKD system performance is also described.
The phase shift method for studying nonlinear acoustics in a soil
Technology Transfer Automated Retrieval System (TEKTRAN)
In this paper, a phase shift method for studying nonlinear acoustic behaviors of a soil is described. The method uses a phase-lock-in technique to measure the phase shift caused by increments in the amplitude of an excitation. The measured phase shift as a function of dynamic strain amplitude is use...
Application of Phase Shifted, Laser Feedback Interferometry to Fluid Physics
NASA Technical Reports Server (NTRS)
Ovryn, Ben; Eppell, Steven J.; Andrews, James H.; Khaydarov, John
1996-01-01
We have combined the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce a new instrument that can measure both optical path length (OPL) changes and discern sample reflectivity variations. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. LFI can yield a high signal-to-noise ratio even for low reflectivity samples. By combining PSI and LFI, we have produced a robust instrument, based upon a HeNe laser, with high dynamic range that can be used to measure either static (dc) or oscillatory changes along the optical path. As with other forms of interferometry, large changes in OPL require phase unwrapping. Conversely, small phase changes are limited by the fraction of a fringe that can be measured. We introduce the phase shifts with an electro-optic modulator (EOM) and use either the Carre or Hariharan algorithms to determine the phase and visibility. We have determined the accuracy and precision of our technique by measuring both the bending of a cantilevered piezoelectric bimorph and linear ramps to the EOM. Using PSI, sub-nanometer displacements can be measured. We have combined our interferometer with a commercial microscope and scanning piezoelectric stage and have measured the variation in OPL and visibility for drops of PDMS (silicone oil) on coated single crystal silicon. Our measurement of the static contact angle agrees with the value of 68 deg stated in the literature.
Is phase-shift mask technology production-worthy?
NASA Astrophysics Data System (ADS)
Chen, Mung
1991-07-01
The feasibility and potential of Phase-Shift Mask (PSM) for sub- 0.5 urn fabrication have been clearly demonstrated. In the '91 SPIE Microlithography Syrnposium, a total of 18 papers on PSM were presented. Many new, innovative designs have been proposed. However, there is still a myriad of technical and logistic problems, which must be resolved for production implementation. We organized the workshop and panel discussion in the hope that the participants would collectively make an assessment of the maturity of the technology and reach a common understanding of the key issues.
Experimental demonstration of microring quadrature phase-shift keying modulators.
Dong, Po; Xie, Chongjin; Chen, Long; Fontaine, Nicolas K; Chen, Young-kai
2012-04-01
Advanced optical modulation formats are a key technology to increase the capacity of optical communication networks. Mach-Zehnder modulators are typically used to generate various modulation formats. Here, we report the first experimental demonstration of quadrature phase-shift keying (QPSK) modulation using compact microring modulators. Generation of 20 Gb/s QPSK signals is demonstrated with 30 μm radius silicon ring modulators with drive voltages of ~6 V. These compact QPSK modulators may be used in miniature optical transponders for high-capacity optical data links. PMID:22466187
Phase-Shifting Liquid Crystal Point-Diffraction Interferometry
NASA Technical Reports Server (NTRS)
Griffin, DeVon W.; Marshall, Kenneth L.; Mercer, Carolyn R.
2000-01-01
, the limited spatial resolution and the methods required for data reduction suggest that a more useful instrument needs to be developed. The category of interferometers known as common path interferometers can eliminate much of the vibration sensitivity associated with traditional interferometry as described above. In these devices, division of the amplitude of the wavefront following the test section produces the reference beam. Examples of these instruments include shearing and point diffraction interferometers. In the latter case, shown schematically, a lens focuses light passing through the test section onto a small diffracting object. Such objects are typically either a circle of material on a high quality glass plate or a small sphere in a glass cell. The size of the focused spot is several times larger than the object so that the light not intercepted by the diffracting object forms the test beam while the diffracted light generates a spherical reference beam. While this configuration is mechanically stable, phase shifting one beam with respect to the other is difficult due to the common path. Phase shifting enables extremely accurate measurements of the phase of the interferogram using only gray scale intensity measurements and is the de facto standard of industry. Mercer and Creath 2 demonstrated phase shifting in a point diffraction interferometer using a spherical spacer in a liquid crystal cell as the diffracting object. By changing the voltage across the cell, they were able to shift the phase of the undiffracted beam relative to the reference beam generated by diffraction from the sphere. While they applied this technology to fluid measurements, the device shifted phase so slowly that it was not useful for studying transient phenomena. We have identified several technical problems that precluded operation of the device at video frame rates and intend to solve them to produce a phase-shifting liquid crystal point-diffraction interferometer operating at
Hand held phase-shifting diffraction moire interferometer
Deason, Vance A.; Ward, Michael B.
1994-01-01
An interferometer in which a coherent beam of light is generated within a remote case and transmitted to a hand held unit tethered to said remote case, said hand held unit having optical elements for directing a pair of mutually coherent collimated laser beams at a diffraction grating. Data from the secondary or diffracted beams are then transmitted to a separate video and data acquisition system for recording and analysis for load induced deformation or for identification purposes. Means are also provided for shifting the phase of one incident beam relative to the other incident beam and being controlled from within said remote case.
Hand held phase-shifting diffraction Moire interferometer
Deason, V.A.; Ward, M.B.
1994-09-20
An interferometer is described in which a coherent beam of light is generated within a remote case and transmitted to a hand held unit tethered to said remote case, said hand held unit having optical elements for directing a pair of mutually coherent collimated laser beams at a diffraction grating. Data from the secondary or diffracted beams are then transmitted to a separate video and data acquisition system for recording and analysis for load induced deformation or for identification purposes. Means are also provided for shifting the phase of one incident beam relative to the other incident beam and being controlled from within said remote case. 4 figs.
Two-step phase-shifting fluorescence incoherent holographic microscopy
Qin, Wan; Yang, Xiaoqi; Li, Yingying; Peng, Xiang; Yao, Hai; Qu, Xinghua; Gao, Bruce Z.
2014-01-01
Abstract. Fluorescence holographic microscope (FINCHSCOPE) is a motionless fluorescence holographic imaging technique based on Fresnel incoherent correlation holography (FINCH) that shows promise in reconstructing three-dimensional fluorescence images of biological specimens with three holograms. We report a developing two-step phase-shifting method that reduces the required number of holograms from three to two. Using this method, we resolved microscopic fluorescent beads that were three-dimensionally distributed at different depths with two interferograms captured by a CCD camera. The method enables the FINCHSCOPE to work in conjunction with the frame-straddling technique and significantly enhance imaging speed. PMID:24972355
Phase-integral calculation of phase shifts for a heavy-ion optical potential
Linnaeus, S.
1986-10-01
Phase shifts for an optical potential representing the nuclear scattering of /sup 18/O by /sup 58/Ni at 60 MeV laboratory energy are calculated by means of an arbitrary-order phase-integral formula taking account of two turning points. The results are found to be in excellent agreement with previously published numerical calculations.
Phase-sensitive optical coherence reflectometer with differential phase-shift keying of probe pulses
Alekseev, A E; Vdovenko, V S; Sergachev, I A; Simikin, D E; Gorshkov, B G; Potapov, V T
2014-10-31
We report a new method for reconstructing the signal shape of the external dynamic perturbations along the entire length of the fibre of an optical coherence reflectometer. The method proposed is based on differential phase-shift keying of a probe pulse and demodulation of scattered light by the phase diversity technique. Possibilities of the method are demonstrated experimentally. (fibre-optic sensors)
Channel Acquisition for Massive MIMO-OFDM With Adjustable Phase Shift Pilots
NASA Astrophysics Data System (ADS)
You, Li; Gao, Xiqi; Swindlehurst, A. Lee; Zhong, Wen
2016-03-01
We propose adjustable phase shift pilots (APSPs) for channel acquisition in wideband massive multiple-input multiple-output (MIMO) systems employing orthogonal frequency division multiplexing (OFDM) to reduce the pilot overhead. Based on a physically motivated channel model, we first establish a relationship between channel space-frequency correlations and the channel power angle-delay spectrum in the massive antenna array regime, which reveals the channel sparsity in massive MIMO-OFDM. With this channel model, we then investigate channel acquisition, including channel estimation and channel prediction, for massive MIMO-OFDM with APSPs. We show that channel acquisition performance in terms of sum mean square error can be minimized if the user terminals' channel power distributions in the angle-delay domain can be made non-overlapping with proper phase shift scheduling. A simplified pilot phase shift scheduling algorithm is developed based on this optimal channel acquisition condition. The performance of APSPs is investigated for both one symbol and multiple symbol data models. Simulations demonstrate that the proposed APSP approach can provide substantial performance gains in terms of achievable spectral efficiency over the conventional phase shift orthogonal pilot approach in typical mobility scenarios.
High sensitivity Moire interferometry with phase shifting at nano resolution
NASA Astrophysics Data System (ADS)
Chen, Bicheng
Due to insatiate demand for miniaturization of electronics, there is a need for new techniques to measure full-field strain at micro-scale structures. In addition, Micro-Electronic-Mechanical-Systems (MEMS) require a high resolution and high sensitivity material property characterization technique. In this study, a theoretic model for a high sensitivity Moire Interferometry (MI) for measuring nano-scale strain field has been developed. The study also includes the application of the proposed measurement technique for the study of reliability of next generation nano-electronics/power electronics. The study includes both theoretical and experimental work. In the theoretical part, a far field modeling of a Moire Interferometer (MI) using the mode decomposition method is proposed according to the analytical formulation from the scalar diffraction theory. The wave propagation within the defined MI far field domain is solved analytically for a single frequency surface relieved grating structure following the Rayleigh-Sommerfeld formulation under the paraxial approximation. It is shown that the far-field electrical field and the intensity interferogram can be calculated using the mode decomposition method. Furthermore, the near-field (propagation distance < 1 mum) assumptions are validated using exact electromagnetic (EM) theory; and the EM fields are simulated in a few microns region above the surface of the diffraction grating. The study shows that there is a strong correlation (correlation factor R = 0.869) of spatial frequency response between EM field and strain field at the nanoscale. Experimentally, a 164 nm/pixel spatial resolution Moire Interferometer with automated full strain field calculation is proposed. Accurate full strain field maps are generated automatically by a combination of phase shifting technique (temporal data redundancy) and Continuous Wavelet Transform (CWT) (spatial data redundancy). A thermal experiment on BGA packaging is used to demonstrate
Symmetry types and phase-shift synchrony in networks
NASA Astrophysics Data System (ADS)
Golubitsky, Martin; Matamba Messi, Leopold; Spardy, Lucy E.
2016-04-01
In this paper we discuss what is known about the classification of symmetry groups and patterns of phase-shift synchrony for periodic solutions of coupled cell networks. Specifically, we compare the lists of spatial and spatiotemporal symmetries of periodic solutions of admissible vector fields to those of equivariant vector fields in the three cases of Rn (coupled equations), Tn (coupled oscillators), and (Rk)n where k ≥ 2 (coupled systems). To do this we use the H / K Theorem of Buono and Golubitsky (2001) applied to coupled equations and coupled systems and prove the H / K theorem in the case of coupled oscillators. Josić and Török (2006) prove that the H / K lists for equivariant vector fields and admissible vector fields are the same for transitive coupled systems. We show that the corresponding theorem is false for coupled equations. We also prove that the pairs of subgroups H ⊃ K for coupled equations are contained in the pairs for coupled oscillators which are contained in the pairs for coupled systems. Finally, we prove that patterns of rigid phase-shift synchrony for coupled equations are contained in those of coupled oscillators and those of coupled systems.
A portable intra-oral scanner based on sinusoidal pattern of fast phase-shifting
NASA Astrophysics Data System (ADS)
Jan, Chia-Ming; Lin, Ying-Chieh
2016-03-01
This paper presented our current research about the intra-oral scanner made by MIRDC. Utilizing the sinusoidal pattern for fast phase-shifting technique to deal with 3D digitalization of human dental surface profile, the development of pseudo-phase shifting digital projection can easily achieve one type of full-field scanning instead of the common technique of the laser line scanning. Based on traditional Moiré method, we adopt projecting fringes and retrieve phase reconstruction to forward phase unwrapping. The phase difference between the plane and object can be exactly calculated from the desired fringe images, and the surface profile of object was probably reconstructed by using the phase differences information directly. According to our algorithm of space mapping between projections and capturing orientation exchange of our intra-oral scanning configuration, the system we made certainly can be proved to achieve the required accuracy of +/-10μm to deal with intra-oral scanning on the basis of utilizing active triangulation method. The final purpose aimed to the scanning of object surface profile with its size about 10x10x10mm3.
Ng, T W
1997-11-01
Previous phase-shifting schemes in computer-aided photoelasticity required the processing of six fringe patterns to derive the phase difference due to retardation. A technique in which a carrier fringe is used is demonstrated to reduce to four the number of fringe patterns required. The use of fewer fringe patterns lowers the computation time and the number of phase-step errors. The basis of the technique is outlined in detail, and experimental results are presented as well. PMID:18264365
Improving the resolution in phase-shifting Gabor holography by CCD shift
NASA Astrophysics Data System (ADS)
Granero, L.; Micó, V.; Zalevsky, Z.; García, J.; Javidi, B.
2015-05-01
Holography dates back to the year when Dennis Gabor reported on a method to avoid spherical aberration and to improve image quality in electron microscopy. Gabor's two-step holographic method was pioneer but suffered from three major drawbacks: the reconstructed image is affected by coherent noise, the twin image problem of holography that also affects the final image quality, and a restricted sample range (weak diffraction assumption) for preserving the holographic behavior of the method. Nowadays, most of those drawbacks have been overcome and new capabilities have been added due to the replacement of the classical recording media (photographic plate) by digital sensors (CCD and CMOS cameras). But in the Gabor' regime, holography is restricted to weak diffraction assumptions because otherwise, diffraction prevents an accurate recovery of the object's complex wavefront. In this contribution, we present an experimental approach to overcome such limitation and improve final image resolution. We use the phase-shifting Gabor configuration while the CCD camera is shifted to different off-axis positions in order to capture a bigger portion of the diffracted wavefront. Thus, once the whole image set is recorded and digitally processed for each camera's position, we merge the resulting band-pass images into one image by assembling a synthetic aperture. Finally, a superresolved image is recovered by Fourier transformation of the information contained in the generated synthetic aperture. Experimental results are provided using a USAF resolution test target and validating our concepts for a gain in resolution of close to 2.
NASA Astrophysics Data System (ADS)
Fan, Jingping; Lu, Xiaoxu; Xu, Xiaofei; Zhong, Liyun
2016-05-01
From a sequence of simultaneous multi-wavelength phase-shifting interferograms (SMWPSIs) recorded by a color CMOS, a principal component analysis (PCA) based multi-wavelength interferometry (MWI) is proposed. First, a sequence of SMWPSIs with unknown phase shifts are recorded with a single-chip color CMOS camera. Subsequently, the wrapped phases of single-wavelength are retrieved with the PCA algorithm. Finally, the unambiguous phase of the extended synthetic wavelength is achieved by the subtraction between the wrapped phases of single-wavelength. In addition, to eliminate the additional phase introduced by the microscope and intensity crosstalk among three-color channels, a two-step phase compensation method with and without the measured object in the experimental system is employed. Compared with conventional single-wavelength phase-shifting interferometry, due to no requirements for phase shifts calibration and the phase unwrapping operation, the actual unambiguous phase of the measured object can be achieved with the proposed PCA-based MWI method conveniently. Both numerical simulations and experimental results demonstrate that the proposed PCA-based MWI method can enlarge not only the measuring range, but also no amplification of noise level.
Rapid extraction of the phase shift of the cold-atom interferometer via phase demodulation
NASA Astrophysics Data System (ADS)
Cheng, Bing; Wang, Zhao-Ying; Xu, Ao-Peng; Wang, Qi-Yu; Lin, Qiang
2015-11-01
Generally, the phase of the cold-atom interferometer is extracted from the atomic interference fringe, which can be obtained by scanning the chirp rate of the Raman lasers at a given interrogation time T. If mapping the phase shift for each T with a series of measurements, the extraction time is limited by the protocol of each T measurement, and therefore increases dramatically when doing fine mapping with a small step of T. Here we present a new method for rapid extraction of the phase shift via phase demodulation. By using this method, the systematic shifts can be mapped though the whole interference area. This method enables quick diagnostics of the potential cause of the phase shift in specific time. We demonstrate experimentally that this method is effective for the evaluation of the systematic errors of the cold atomic gravimeter. The systematic phase error induced by the quadratic Zeeman effect in the free-falling region is extracted by this method. The measured results correspond well with the theoretic prediction and also agree with the results obtained by the fringe fitting method for each T. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174249 and 61475139), the Ministry of Science and Technology of China (Grant No. 2011AA060504), the National Basic Research Program of China (Grant No. 2013CB329501), and the Fundamental Research Funds for the Central Universities, China (Grant No. 2015FZA3002).
NASA Astrophysics Data System (ADS)
Yeh, Kwei-Tin; Huang, Chao-Yi
2014-07-01
For 193 nm immersion lithography, it is hard to print clear 4X nm dense images (ex. contact holes) on wafer without any modifications due to lower light intensity. In the past, the most common method is to add the scattering bars, which can enhance the light intensity of contact holes. However, with tinier pattern, the distance between scattering bars and contact holes will get quite close. Hence, the error tolerance for mask making was reduced. On the other hand, this method may also cause the pattern twist which will induce pattern crosslink. To solve this issue, a new design method for lithography mask was proposed, which is named "Phase-shifting Scattering Bar", and it shows better performance in 1D chain array patterns than those with traditional scattering bars. However, for even tinier patterns, it is quite difficult to put these scattering bars on mask. Hence, another special design named "Interlaced Phase-shifting Mask" was proposed to handle such tiny dense patterns. In this design, main patterns are also the scattering bars for adjacent patterns. Hence, there is no need for additional tiny scattering bars, and the mask making requirement can be also relaxed. Both of these two mask design are useful tools to trim and modify light intensity profile on wafer. The image contrast was largely enhanced which means a better resolution and a larger process window can be gained without the cost of new illumination equipments.
A color phase shift profilometry for the fabric defect detection
NASA Astrophysics Data System (ADS)
Song, Li-mei; Li, Zong-yan; Chang, Yu-lan; Xing, Guang-xin; Wang, Peng-qiang; Xi, Jiang-tao; Zhu, Teng-da
2014-07-01
For fabric defect identification in the textile industry, a three-dimensional (3D) color phase shift profilometry (CPSP) method is proposed. The detecting system is mainly composed of one CCD camera and one digital-light-processing (DLP) projector. Before detection, the system should be calibrated to make sure the camera parameters. The CPSP color grating is projected to the measured fabric by DLP projector, and then it is collected by CCD camera to obtain the grating phase. The 3D measurement can be completed by the grating phase difference. In image acquisition, only invariable grating is projected to the object. In order to eliminate the interference from background light during the image acquisition, the brightness correction method is researched for improving the detection accuracy. The experimental results show that the false rate of detecting the fabric defects is 5.78%, the correct rates of detecting the fabric defects of hole and qualified fabric are both 100%, and the correct rates of detecting the fabric defect of scratch and fold are 98% and 96%, respectively. The experiment proves that the proposed method can accurately identify fabric defects.
A new varied continuation step method in seismic migration by phase shift plus interpolation
Guotian, T. )
1992-01-01
In this paper the principle of wave equation migration using phase shift plus interpolation is described briefly. Wave field extrapolation formula in such migration and final imaging equation are properly modified, with downward extrapolation operator redefined, so that the imaging can be achieved by using fast Fourier transform (FFT). A new varied continuation step method is given which is different from usual one in time domain. The new method, which is different from usual varied continuation step method for time domain interpolation in phase shift plus interpolation migration, uses the downward extrapolation continuation step much longer than a quarter of an apparent wave length; therefore, the efficiency of such seismic migration is improved satisfactorily. The processing results of theoretical model, coal field and high dip seismic data show that this new method is a f-k domain migration technique which is economic and suitable to the seismic data collected from the area where there are high dip formations and complicated geological structures.
Imaging 100 nm contacts with high transmission attenuated phase shift masks
NASA Astrophysics Data System (ADS)
Beach, James V.; Petersen, John S.; Eynon, Benjamin G., Jr.; Taylor, Darren; Gerold, Dave J.; Maslow, Mark J.
2002-12-01
This study explores the capability of printing 100 nm contacts through the use of 9% and 15% attenuated phase shift masks and a 0.75 NA 193 nm scanner. The mask designs targeted simultaneous solutions for 100 nm contacts at pitches from 200 nm to 300 nm. The two masks were successfully manufactured from experimental MoSiON embedded-attenuated phase shift mask (EAPSM) blanks. The 100 nm contacts were successfully printed with a depth of focus (DOF) from 0.1-0.7 μm. Overlapping process windows were not achieved but were possible upon adjustment of the mask biases. The observed mask error enhancement factor (MEEF) was approximately 3 for the 220 nm pitch. Side lobe printing was not observed for either mask.
Common path point diffraction interferometer using liquid crystal phase shifting
NASA Technical Reports Server (NTRS)
Mercer, Carolyn R. (Inventor)
1997-01-01
A common path point diffraction interferometer uses dyed, parallel nematic liquid crystals which surround an optically transparent microsphere. Coherent, collimated and polarized light is focused on the microsphere at a diameter larger than that of the microsphere. A portion of the focused light passes through the microsphere to form a spherical wavefront reference beam and the rest of the light is attenuated by the dyed liquid crystals to form an object beam. The two beams form an interferogram which is imaged by a lens onto an electronic array sensor and into a computer which determines the wavefront of the object beam. The computer phase shifts the interferogram by stepping up an AC voltage applied across the liquid crystals without affecting the reference beam.
Low energy scattering phase shifts for meson-baryon systems
NASA Astrophysics Data System (ADS)
Detmold, William; Nicholson, Amy N.
2016-06-01
In this work, we calculate meson-baryon scattering phase shifts in four channels using lattice QCD methods. From a set of calculations at four volumes, corresponding to spatial sizes of 2, 2.5, 3, and 4 fm, and a pion mass of mπ˜390 MeV , we determine the scattering lengths and effective ranges for these systems at the corresponding quark masses. We also perform the calculation at a lighter quark mass, mπ˜230 MeV , on the largest volume. Using these determinations, along with those in previous work, we perform a chiral extrapolation of the scattering lengths to the physical point after correcting for the effective range contributions using the multivolume calculations performed at mπ˜390 MeV .
Hexagonal multiple phase-and-amplitude-shift-keyed signal sets
NASA Technical Reports Server (NTRS)
Simon, M. K.; Smith, J. G.
1973-01-01
Selection of a particular signal set array for a bandwidth-constrained multiple phase-and-amplitude-shift-keyed (MPASK) communication system for a linear additive Gaussian noise channel requires consideration of factors such as average and/or peak power vs symbol error probability, signal amplitude dynamic range, simplicity of generation and detection, and number of bit errors per symbol error (Gray code properties). A simple technique is presented for generating and optimally detecting the honeycomb (hexagonal) signal set, i.e., the signal set that has the tightest sphere-packing properties. The symbol and bit error probability performance of this set is compared to other two-dimensional signal sets that have been investigated in the literature, and is shown to be slightly superior from an average power standpoint. The paper concludes with a comparison of all of these signal sets from the standpoint of the factors listed above.
Potential energy function information from quantum phase shift using the variable phase method.
Lemes, Nelson H T; Braga, João P; Alves, Márcio O; Costa, Éderson D'M
2014-07-01
The present work discusses quantum phase shift sensitivity analysis with respect to the potential energy function. A set of differential equations for the functional derivative of the quantum phase shift with respect to the potential energy function was established and coupled with the variable phase equation. This set of differential equations provides a simple, exact and straightforward way to establish the sensitivity matrix. The present procedure is easier to use than the finite difference approach, in which several direct problems have to be addressed. Furthermore, integration of the established equations can be used to demonstrate how the sensitivity phase shift is accumulated as a function of the interatomic distance. The potential energy function was refined to produce a better quality function. The average error on the phase shift decreased from 9.8% in the original potential function to 0.13% in the recovered potential. The present procedure is an important initial step for further work towards recovering potential energy functions in upper dimensions or to recovering this function from cross sections. PMID:24935112
A Novel Sample Based Quadrature Phase Shift Keying Demodulator
Ali, Sawal Hamid Md
2014-01-01
This paper presents a new practical QPSK receiver that uses digitized samples of incoming QPSK analog signal to determine the phase of the QPSK symbol. The proposed technique is more robust to phase noise and consumes up to 89.6% less power for signal detection in demodulation operation. On the contrary, the conventional QPSK demodulation process where it uses coherent detection technique requires the exact incoming signal frequency; thus, any variation in the frequency of the local oscillator or incoming signal will cause phase noise. A software simulation of the proposed design was successfully carried out using MATLAB Simulink software platform. In the conventional system, at least 10 dB signal to noise ratio (SNR) is required to achieve the bit error rate (BER) of 10−6, whereas, in the proposed technique, the same BER value can be achieved with only 5 dB SNR. Since some of the power consuming elements such as voltage control oscillator (VCO), mixer, and low pass filter (LPF) are no longer needed, the proposed QPSK demodulator will consume almost 68.8% to 99.6% less operational power compared to conventional QPSK demodulator. PMID:25197687
Geometric phase-shifting for low-coherence interference microscopy
NASA Astrophysics Data System (ADS)
Roy, M.; Svahn, P.; Cherel, L.; Sheppard, C. J. R.
2002-06-01
A low-coherence Linnik interference microscope using high numerical aperture optics has been constructed. The system uses a tungsten halogen lamp and Köhler illumination, with separate control over field and aperture stops, so that experiments can be conducted with a range of different operating conditions. The novel feature of the system is the use of an achromatic phase-shifter operating on the principle of the geometric phase, achieved by using a polarising beam splitter, a quarter wave plate and a rotating polariser. Image information is extracted from the visibility of the fringes, the position of the visibility peak along the scanning axis yielding the height of the test surface at the corresponding point.
NASA Astrophysics Data System (ADS)
Singh Mehta, Dalip; Srivastava, Vishal
2012-11-01
We report quantitative phase imaging of human red blood cells (RBCs) using phase-shifting interference microscopy. Five phase-shifted white light interferograms are recorded using colour charge coupled device camera. White light interferograms were decomposed into red, green, and blue colour components. The phase-shifted interferograms of each colour were then processed by phase-shifting analysis and phase maps for red, green, and blue colours were reconstructed. Wavelength dependent refractive index profiles of RBCs were computed from the single set of white light interferogram. The present technique has great potential for non-invasive determination of refractive index variation and morphological features of cells and tissues.
Real-time microscopic phase-shifting profilometry.
Van der Jeught, Sam; Soons, Joris A M; Dirckx, Joris J J
2015-05-20
A real-time microscopic profilometry system based on digital fringe projection and parallel programming has been developed and experimentally tested. Structured light patterns are projected onto an object through one pathway of a stereoscopic operation microscope. The patterns are deformed by the shape of the object and are then recorded with a high-speed CCD camera placed in the other pathway of the microscope. As the optical pathways of both arms are separated and reach the same object point at a relative angle, the recorded patterns allow the full-field object height variations to be calculated and the three-dimensional shape to be reconstructed by employing standard triangulation techniques. Applying proper hardware triggering, the projector-camera system is synchronized to capture up to 120 unique deformed line patterns per second. Using standard four-step phase-shifting profilometry techniques and applying graphics processing unit programming for fast phase wrapping, scaling, and visualization, we demonstrate the capability of the proposed system to generate 30 microscopic height maps per second. This allows the qualitative depth perception of the stereomicroscope operator to be enhanced by live quantitative height measurements with depth resolutions in the micrometer range. PMID:26192534
All-optical logic gates based on cross phase modulation effect in a phase-shifted grating.
Li, Qiliang; Song, Junfeng; Chen, Xin; Bi, Meihua; Hu, Miao; Li, Shuqin
2016-09-01
In this paper, we perform a theoretical study of the all-optical logic gates based on the techniques of cross phase modulation (XPM) in a phase-shifted grating. Here the pumps are used to control the switching of a weak continuous wave (cw). In order to understand the transferring process of the information from the pump light to the cw light, we first study the switching characteristic of the device. Then, by changing the combination between two pumps, in a fiber grating with zero phase shift we have realized NOT, AND, and NAND gates, and in a phase-shifted grating with the phase shift π, the other various logic operations can be realized such as NAND gates and OR gates; when selecting Δφ=3/2π, we can realize XOR gates and XNOR gates. Thus the change of the phase shift of the phase-shifted grating will yield various logic gates. PMID:27607262
NASA Astrophysics Data System (ADS)
Ma, S.; Quan, C.; Zhu, R.; Tay, C. J.
2012-08-01
Digital sinusoidal phase-shifting fringe projection profilometry (DSPFPP) is a powerful tool to reconstruct three-dimensional (3D) surface of diffuse objects. However, a highly accurate profile is often hindered by nonlinear response, color crosstalk and imbalance of a pair of digital projector and CCD/CMOS camera. In this paper, several phase error correction methods, such as Look-Up-Table (LUT) compensation, intensity correction, gamma correction, LUT-based hybrid method and blind phase error suppression for gray and color-encoded DSPFPP are described. Experimental results are also demonstrated to evaluate the effectiveness of each method.
Dispersion and phase shifts of torsional waves in forward models
NASA Astrophysics Data System (ADS)
Cox, G. A.; Livermore, P. W.; Mound, J. E.
2013-12-01
Torsional Alfvén waves have been thought to exist in the Earth's core since their theoretical prediction by Braginsky in 1970. More recently, they have been inferred from observations of secular variation and length of day, and also observed in geodynamo simulations. These inferences from geophysical data have provided an important means of estimating core properties such as viscosity and internal magnetic field strength. We produce 1D forward models of torsional waves in the Earth's core, also known as torsional oscillations, and study their evolution in a cylinder, a full sphere and an equatorially symmetric spherical shell. The key features of torsional waves in our models are: geometric dispersion, phase shifts and internal reflections. In all three core geometries, we find that travelling torsional waves undergo significant geometric dispersion that increases with successive reflections from the boundaries such that an initial wave pulse becomes unidentifiable within three transits of the core. This dispersion partly arises due to low amplitude wakes trailing behind sharply defined pulses during propagation, a phenomenon that is linked to the failure of Huygens' principle in the geometric setting of torsional waves. We investigate the relationship between geometric dispersion and wavelength, concluding that long wavelength features are more dispersive than short wavelength features. This result is particularly important because torsional waves inferred from secular variation are relatively long wavelength, and are therefore likely to undergo significant dispersion within the Earth's core. Torsional waves in all three geometries are reflected at the equator of the core-mantle boundary with the same sign as the incident wave, but display more complicated behaviour at the rotation axis. In a cylindrical core, the analytic solutions to the torsional wave equation are known. We use these to derive an expression for the phase shift that torsional waves undergo upon
The exergy of a phase shift: Ecosystem functioning loss in seagrass meadows of the Mediterranean Sea
NASA Astrophysics Data System (ADS)
Montefalcone, Monica; Vassallo, Paolo; Gatti, Giulia; Parravicini, Valeriano; Paoli, Chiara; Morri, Carla; Bianchi, Carlo Nike
2015-04-01
Sustained functioning of ecosystems is predicted to depend upon the maintenance of their biodiversity, structure and integrity. The large consensus achieved in this regard, however, faces to the objective difficulty of finding appropriate metrics to measure ecosystem functioning. Here, we aim at evaluating functional consequence of the phase shift occurring in meadows of the Mediterranean seagrass Posidonia oceanica, a priority habitat that is undergoing regression in many coastal areas due to multiple human pressures. Structural degradation of the P. oceanica ecosystem, consequent to increasing coastal exploitation and climate change, may result in the progressive replacement of this seagrass by opportunistic macrophytes, either native or alien. Reviewing published information and our personal records, we measured changes in biological habitat provisioning, species richness and biomass associated to each of the alternative states characterizing the phase shift. Then, ecosystem functioning was assessed by computing the exergy associated to each state, exergy being a state variable that measures the ecosystem capacity to produce work. Phase shift was consistently shown to imply loss in habitat provision, species richness, and biomass; structural and compositional loss was parallelled by a reduction of exergy content, thus providing for the first time an objective and integrative measure of the loss of ecosystem functioning following the degradation of healthy seagrass meadows.
Phase shifts and phase π jumps in four-terminal waveguide Aharonov-Bohm interferometers
NASA Astrophysics Data System (ADS)
Kreisbeck, Christoph; Kramer, Tobias; Buchholz, Sven S.; Fischer, Saskia F.; Kunze, Ulrich; Reuter, Dirk; Wieck, Andreas D.
2010-10-01
Quantum coherent properties of electrons can be studied in Aharonov-Bohm (AB) interferometers. We investigate both experimentally and theoretically the transmission phase evolution in a four-terminal quasi-one-dimensional AlGaAs/GaAs-based waveguide AB ring. As main control parameter besides the magnetic field, we tune the Fermi wave number along the pathways using a top-gate. Our experimental results and theoretical calculations demonstrate the strong influence of the measurement configuration upon the AB-resistance-oscillation phase in a four-terminal device. While the nonlocal setup displays continuous phase shifts of the AB oscillations, the phase remains rigid in the local voltage-probe setup. Abrupt phase jumps are found in all measurement configurations. We analyze the phase shifts as functions of the magnetic field and the Fermi energy and provide a detailed theoretical model of the device. Scattering and reflections in the arms of the ring are the source of abrupt phase jumps by π .
Phase Shift of the Circadian Rhythm of Lemna Caused by Pulses of a Leucine Analog, Trifluoroleucine
Kondo, Takao
1988-01-01
Pulses of a fluorinated analog of leucine, 5′,5′,5′-trifluoroleucine, reset the phase of the circadian rhythm of K+ uptake in Lemna gibba G3 under continuous light conditions. The trifluoroleucine pulse caused the largest delay phase-shifts during the early subjective phase but it caused only small phase advances. The action of trifluoroleucine was investigated and the following results were obtained. (a) The uptake of trifluoroleucine was essentially the same at all circadian phases, even though phase shifting was dramatically different at different phases. At effective phases, the magnitude of phase shifting was well correlated with the amount of trifluoroleucine taken up by the duckweed. (b) The trifluoroleucine pulse lowered the endogenous content of valine and leucine but these decreases did not correlate with phase shifting. (c) Protein synthesis was not affected by trifluoroleucine pulses which caused large phase shifts. (d) Pulses of 4-azaleucine, a different structural analog of leucine, also caused phase shifting. However, neither the direction nor the effective times of phase shifting were similar to those of trifluoroleucine. Taken together, these results negate the proposition that trifluoroleucine and azaleucine caused phase shift by disturbing amino acid metabolism and/or inhibiting protein synthesis, but they suggest instead that these analogs are incorporated into some protein(s) which are necessary for normal clock operation. PMID:16666410
Katkovnik, V; Bioucas-Dias, J
2014-08-01
Phase-shifting interferometry is a coherent optical method that combines high accuracy with high measurement speeds. This technique is therefore desirable in many applications such as the efficient industrial quality inspection process. However, despite its advantageous properties, the inference of the object amplitude and the phase, herein termed wavefront reconstruction, is not a trivial task owing to the Poissonian noise associated with the measurement process and to the 2π phase periodicity of the observation mechanism. In this paper, we formulate the wavefront reconstruction as an inverse problem, where the amplitude and the absolute phase are assumed to admit sparse linear representations in suitable sparsifying transforms (dictionaries). Sparse modeling is a form of regularization of inverse problems which, in the case of the absolute phase, is not available to the conventional wavefront reconstruction techniques, as only interferometric phase modulo-2π is considered therein. The developed sparse modeling of the absolute phase solves two different problems: accuracy of the interferometric (wrapped) phase reconstruction and simultaneous phase unwrapping. Based on this rationale, we introduce the sparse phase and amplitude reconstruction (SPAR) algorithm. SPAR takes into full consideration the Poissonian (photon counting) measurements and uses the data-adaptive block-matching 3D (BM3D) frames as a sparse representation for the amplitude and for the absolute phase. SPAR effectiveness is documented by comparing its performance with that of competitors in a series of experiments. PMID:25121537
Measuring rainwater content by radar using propagation differential phase shift
NASA Technical Reports Server (NTRS)
Jameson, A. R.
1994-01-01
While radars measure several quantities closely coupled to the rainfall rate, for frequencies less than 15 GHz, estimates of the rainwater content W are traditionally computed from the radar reflectivity factor Z or the rate of attenuation A--quantities only weakly related to W. Consequently, instantaneous point estimates of W using Z and A are often erroneous. A more natural, alternative parameter for estimating W at these frequencies is the specific polarization propagation differential phase shift phi(sub DP), which is a measure of the change in the difference between phases of vertically (V) and horizontally (H) polarized waves with increasing distance from a radar. It is now well known that W is nearly linearly related to phi(sub DP) divided by (1 - reversed R), where reversed R is the mass-weighted mean axis ratio of the raindrops. Unfortunately, such relations are not widely used in part because measurements of phi(sub DP) are scarce but also because one must determine reversed R. In this work it is shown that this parameter can be estimated using the differential reflectivity (Z(sub H)/Z(sub V) at 3 GHz. An alternative technique is suggested for higher frequencies when the differential reflectivity becomes degraded by attenuation. While theory indicates that it should be possible using phi(sub DP) to estimate W quite accurately, measurement errors increase the uncertainty to +/- 18%-35% depending on reversed R. While far from ideal, it appears that these estimates are likely to be considerably more accurate than those deduced using currently available methods.
Analysis of all-optical temporal integrator employing phased-shifted DFB-SOA.
Jia, Xin-Hong; Ji, Xiao-Ling; Xu, Cong; Wang, Zi-Nan; Zhang, Wei-Li
2014-11-17
All-optical temporal integrator using phase-shifted distributed-feedback semiconductor optical amplifier (DFB-SOA) is investigated. The influences of system parameters on its energy transmittance and integration error are explored in detail. The numerical analysis shows that, enhanced energy transmittance and integration time window can be simultaneously achieved by increased injected current in the vicinity of lasing threshold. We find that the range of input pulse-width with lower integration error is highly sensitive to the injected optical power, due to gain saturation and induced detuning deviation mechanism. The initial frequency detuning should also be carefully chosen to suppress the integration deviation with ideal waveform output. PMID:25402095
Three-frame generalized phase-shifting interferometry by a Euclidean matrix norm algorithm
NASA Astrophysics Data System (ADS)
Xu, Yuanyuan; Wang, Yawei; Ji, Ying; Han, Hao; Jin, Weifeng
2016-09-01
Generalized phase-shifting interferometry (GPSI) is one of the most effective techniques in imaging of a phase object, in which phase retrieval is an essential and important procedure. In this paper, a simple and rapid algorithm for retrieval of the unknown phase shifts in three-frame GPSI is proposed. Using this algorithm, the value of phase shift can be calculated by a determinate formula consisting of three different Euclidean matrix norms of the intensity difference between two phase shifted interferograms, and then the phase can be retrieved easily. The algorithm has the advantages of freeing from the background elimination and less computation, since it only needs three phase-shifted interferograms without no extra measurements, the iterative procedure or the integral transformation. The reliability and accuracy of this algorithm were demonstrated by simulation and experimental results.
Self-imaging phase mask used in digital holography with phase-shifting
NASA Astrophysics Data System (ADS)
Fajst, Agnieszka; Sypek, Maciej; Makowski, Michal; Suszek, Jaroslaw; Kolodziejczyk, Andrzej
2008-12-01
The digital reconstruction of an optically recorded hologram has become a fast developing method and has found a vast practical application in many branches of science and industry. An especially invented diffractive optical element with self imaging properties is placed in the reference beam. In the recording process this element forms its self-image in the hologram plane. Self-imaging properties of the diffractive optical element provide the possibility of recording a digital hologram by means of the phase-shifting without any additional imaging components. The innovation of the proposed method lies in using a self-imaging diffractive optical element which enables a significant simplification of a spatial phase shifting optical setup used to record the digital hologram with only a small decrease of the quality of the reconstructed image.
Atmospheric turbulence compensation with laser phase shifting interferometry
NASA Astrophysics Data System (ADS)
Rabien, S.; Eisenhauer, F.; Genzel, R.; Davies, R. I.; Ott, T.
2006-04-01
Laser guide stars with adaptive optics allow astronomical image correction in the absence of a natural guide star. Single guide star systems with a star created in the earth's sodium layer can be used to correct the wavefront in the near infrared spectral regime for 8-m class telescopes. For possible future telescopes of larger sizes, or for correction at shorter wavelengths, the use of a single guide star is ultimately limited by focal anisoplanatism that arises from the finite height of the guide star. To overcome this limitation we propose to overlap coherently pulsed laser beams that are expanded over the full aperture of the telescope, traveling upwards along the same path which light from the astronomical object travels downwards. Imaging the scattered light from the resultant interference pattern with a camera gated to a certain height above the telescope, and using phase shifting interferometry we have found a method to retrieve the local wavefront gradients. By sensing the backscattered light from two different heights, one can fully remove the cone effect, which can otherwise be a serious handicap to the use of laser guide stars at shorter wavelengths or on larger telescopes. Using two laser beams multiconjugate correction is possible, resulting in larger corrected fields. With a proper choice of laser, wavefront correction could be expanded to the visible regime and, due to the lack of a cone effect, the method is applicable to any size of telescope. Finally the position of the laser spot could be imaged from the side of the main telescope against a bright background star to retrieve tip-tilt information, which would greatly improve the sky coverage of the system.
Hybrid shearing and phase-shifting point diffraction interferometer
Goldberg, Kenneth Alan; Naulleau, Patrick P.
2003-06-03
A new interferometry configuration combines the strengths of two existing interferometry methods, improving the quality and extending the dynamic range of both. On the same patterned mask, placed near the image-plane of an optical system under test, patterns for phase-shifting point diffraction interferometry and lateral shearing interferometry coexist. The former giving verifiable high accuracy for the measurement of nearly diffraction-limited optical systems. The latter enabling the measurement of optical systems with more than one wave of aberration in the system wavefront. The interferometry configuration is a hybrid shearing and point diffraction interferometer system for testing an optical element that is positioned along an optical path including: a source of electromagnetic energy in the optical path; a first beam splitter that is secured to a device that includes means for maneuvering the first beam splitter in a first position wherein the first beam splitter is in the optical path dividing light from the source into a reference beam and a test beam and in a second position wherein the first beam splitter is outside the optical path: a hybrid mask which includes a first section that defines a test window and at least one reference pinhole and a second section that defines a second beam splitter wherein the hybrid mask is secured to a device that includes means for maneuvering either the first section or the second section into the optical path positioned in an image plane that is created by the optical element, with the proviso that the first section of the hybrid mask is positioned in the optical path when first beam splitter is positioned in the optical path; and a detector positioned after the hybrid mask along the optical path.
Black reefs: iron-induced phase shifts on coral reefs.
Kelly, Linda Wegley; Barott, Katie L; Dinsdale, Elizabeth; Friedlander, Alan M; Nosrat, Bahador; Obura, David; Sala, Enric; Sandin, Stuart A; Smith, Jennifer E; Vermeij, Mark J A; Williams, Gareth J; Willner, Dana; Rohwer, Forest
2012-03-01
The Line Islands are calcium carbonate coral reef platforms located in iron-poor regions of the central Pacific. Natural terrestrial run-off of iron is non-existent and aerial deposition is extremely low. However, a number of ship groundings have occurred on these atolls. The reefs surrounding the shipwreck debris are characterized by high benthic cover of turf algae, macroalgae, cyanobacterial mats and corallimorphs, as well as particulate-laden, cloudy water. These sites also have very low coral and crustose coralline algal cover and are call black reefs because of the dark-colored benthic community and reduced clarity of the overlying water column. Here we use a combination of benthic surveys, chemistry, metagenomics and microcosms to investigate if and how shipwrecks initiate and maintain black reefs. Comparative surveys show that the live coral cover was reduced from 40 to 60% to <10% on black reefs on Millennium, Tabuaeran and Kingman. These three sites are relatively large (>0.75 km(2)). The phase shift occurs rapidly; the Kingman black reef formed within 3 years of the ship grounding. Iron concentrations in algae tissue from the Millennium black reef site were six times higher than in algae collected from reference sites. Metagenomic sequencing of the Millennium Atoll black reef-associated microbial community was enriched in iron-associated virulence genes and known pathogens. Microcosm experiments showed that corals were killed by black reef rubble through microbial activity. Together these results demonstrate that shipwrecks and their associated iron pose significant threats to coral reefs in iron-limited regions. PMID:21881615
One-exposure phase-shifting digital holography based on the self-imaging effect
NASA Astrophysics Data System (ADS)
Siemion, Agnieszka; Sypek, Maciej; Makowski, Michał; Suszek, Jaroslaw; Siemion, Andrzej; Wojnowski, Dariusz; Kolodziejczyk, Andrzej
2010-05-01
A diffractive optical element with self-imaging capabilities is used to make a phase-shifting digital holography optical system simpler and cheaper. Sequential phase-shifting requires multiple exposures, and parallel phase-shifting demands a more complicated optical system. As opposed to typical phase-shifting methods, using the self-imaging diffractive optical element requires only one exposure on a low-cost CMOS matrix, and due to the small number of needed elements, the optical system is very compact. Instead of the approximation and interpolation methods, the properties of the self-imaging effect are utilized in the recording process and in the numerical reconstruction process.
Removal of complex-conjugate ambiguity in SDOCT by using phase shiftings
NASA Astrophysics Data System (ADS)
Cai, Wenyuan; Jiang, Zhuqing; Huang, Haochong
2012-12-01
The three-step or many steps phase shifting method is usually employed to resolve the complex-conjugate ambiguity in Spectral-domain optical coherence tomography (SD-OCT). However it reduces the image quality and also the imaging speed is slow. In this paper two steps phase-shifting is used in digital image processing to resolve the complex-conjugate ambiguity and improves the quality of reconstructed image in SD-OCT. In the two-step phase shifting method the phase shifting operation is used only once which simplified the experiment and also the effect of relative error in SD-OCT on image quality is eliminated.
Absolute Definition of Phase Shift in the Elastic Scattering of a Particle from Compound Systems
NASA Technical Reports Server (NTRS)
Temkin, A.
1961-01-01
The projection of the target wave function on the total wave function of a scattered particle interacting with the target system is used to define an absolute phase shift including any multiples of pi. With this definition of the absolute phase shift, one can prove rigorously in the limit of zero energy for s-wave electrons scattered from atomic hydrogen that the triplet phase shift must approach a nonzero multiple of pi. One can further show that at least one pi of this phase shift is not connected with the existence of a bound state of the H- ion.
Trujillo, Carlos; Doblas, Ana; Saavedra, Genaro; Martínez-Corral, Manuel; García-Sucerquia, Jorge
2016-04-01
The use of an electronically tunable lens (ETL) to produce controlled phase shifts in interferometric arrangements is shown. The performance of the ETL as a phase-shifting device is experimentally validated in phase-shifting digital holographic microscopy. Quantitative phase maps of a section of the thorax of a Drosophila melanogaster fly and of human red blood cells have been obtained using our proposal. The experimental results validate the possibility of using the ETL as a reliable phase-shifter device. PMID:27192250
Effect of Phase Shift from Corals to Zoantharia on Reef Fish Assemblages
Cruz, Igor C. S.; Loiola, Miguel; Albuquerque, Tiago; Reis, Rodrigo; de Anchieta C. C. Nunes, José; Reimer, James D.; Mizuyama, Masaru; Kikuchi, Ruy K. P.; Creed, Joel C.
2015-01-01
Consequences of reef phase shifts on fish communities remain poorly understood. Studies on the causes, effects and consequences of phase shifts on reef fish communities have only been considered for coral-to-macroalgae shifts. Therefore, there is a large information gap regarding the consequences of novel phase shifts and how these kinds of phase shifts impact on fish assemblages. This study aimed to compare the fish assemblages on reefs under normal conditions (relatively high cover of corals) to those which have shifted to a dominance of the zoantharian Palythoa cf. variabilis on coral reefs in Todos os Santos Bay (TSB), Brazilian eastern coast. We examined eight reefs, where we estimated cover of corals and P. cf. variabilis and coral reef fish richness, abundance and body size. Fish richness differed significantly between normal reefs (48 species) and phase-shift reefs (38 species), a 20% reduction in species. However there was no difference in fish abundance between normal and phase shift reefs. One fish species, Chaetodon striatus, was significantly less abundant on normal reefs. The differences in fish assemblages between different reef phases was due to differences in trophic groups of fish; on normal reefs carnivorous fishes were more abundant, while on phase shift reefs mobile invertivores dominated. PMID:25629532
Single-shot dual-wavelength phase unwrapping in parallel phase-shifting digital holography.
Lee, Yonghee; Ito, Yasunori; Tahara, Tatsuki; Inoue, Junichi; Xia, Peng; Awatsuji, Yasuhiro; Nishio, Kenzo; Ura, Shogo; Matoba, Osamu
2014-04-15
We propose a single-shot phase-unwrapping method using two wavelengths in parallel phase-shifting digital holography (PPSDH). The proposed method enables one to solve the phase ambiguity problem in PPSDH. We conducted an experiment of the proposed method using two lasers whose wavelengths are 473 and 532 nm. An object having about 1.9 μm step, which is 7.1 times larger than the half wavelength of one of the lasers (266 nm), was fabricated by using vapor deposition of aluminum. Single-shot measurement of the height of the object was successfully demonstrated, and the validity of the proposed method was verified. PMID:24978996
Design of the phase-shifting algorithm for flatness measurement of a mask blank glass
NASA Astrophysics Data System (ADS)
Kim, Yangjin; Hibino, Kenichi; Sugita, Naohiko; Mitsuishi, Mamoru
2014-04-01
Nonlinearity and non-uniformity of phase-shifts significantly contribute to the error of the evaluated phase in phase-shifting interferometry. However, state of the art error-compensating algorithms can counteract the linear mis-calibration and first-order nonlinearity associated with the phase-shift. We describe an error expansion method that is utilized to construct a phase-shifting algorithm that can compensate the second-order nonlinearity and non-uniformity of phase-shifts. The conditions for eliminating the effect of second-order nonlinearity and non-uniformity of phase-shifts are given as a set of linear equations for the sampling amplitudes. We developed a novel 11-sample phase-shifting algorithm that can compensate for the second-order nonlinearity and non-uniformity of phase-shifts and is robust up to a 4th harmonic. Experimental results show that the surface shape of a transparent plate could be measured with a precision of 1 nm, over the 120-mm-diameter aperture.
Phase-shifter edge effects on attenuated phase-shifting mask image quality
NASA Astrophysics Data System (ADS)
Wong, Alfred K. K.; Ferguson, Richard A.; Neureuther, Andrew R.
1994-05-01
Edge effects of space, line, and linespace patterns in attenuated phase-shifting masks are studied using experimentally measured aerial images from the IBM AIMS tool, the scalar and thin mask approximations in SPLAT, and the rigorous electromagnetic simulator TEMPEST. The inadequacy of the thin mask approximation cannot be anticipated from comparisons of in- focus images of isolated line features as the experimentally measured image and the predictions from SPLAT and TEMPEST agree well. However, the scalar and thin mask approximations are not suitable for out of focus image prediction for all pattern types because the presence of the glass edges causes a focus shift of about 0.1 micrometers . Printing small isolated spaces and dense linespace patterns is more robust than isolated lines in the attenuated PSM technology.
An encryption scheme based on phase-shifting digital holography and amplitude-phase disturbance
NASA Astrophysics Data System (ADS)
Hua, Li-Li; Xu, Ning; Yang, Geng
2014-06-01
In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform. We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.
Stokesian peristaltic pumping in a three-dimensional tube with a phase-shifted asymmetry
NASA Astrophysics Data System (ADS)
Aranda, Vivian; Cortez, Ricardo; Fauci, Lisa
2011-08-01
Many physiological flows are driven by waves of muscular contractions passed along a tubular structure. This peristaltic pumping plays a role in ovum transport in the oviduct and in rapid sperm transport through the uterus. As such, flow due to peristalsis has been a central theme in classical biological fluid dynamics. Analytical approaches and numerical methods have been used to study flow in two-dimensional channels and three-dimensional tubes. In two dimensions, the effect of asymmetry due to a phase shift between the channel walls has been examined. However, in three dimensions, peristalsis in a non-axisymmetric tube has received little attention. Here, we present a computational model of peristaltic pumping of a viscous fluid in three dimensions based upon the method of regularized Stokeslets. In particular, we study the flow structure and mean flow in a three-dimensional tube whose asymmetry is governed by a single phase-shift parameter. We view this as a three-dimensional analog of the phase-shifted two-dimensional channel. We find that the maximum mean flow rate is achieved for the parameter that results in an axisymmetric tube. We also validate this approach by comparing our computational results with classical long-wavelength theory for the three-dimensional axisymmetric tube. This computational framework is easily implemented and may be adapted to more comprehensive physiological models where the kinematics of the tube walls are not specified a priori, but emerge due to the coupling of its passive elastic properties, force generating mechanisms, and the surrounding viscous fluid.
NASA Astrophysics Data System (ADS)
Yoshikawa, Nobukazu; Kajihara, Kazuki
2015-09-01
When phase-shifting digital holography with a continuous fringe-scanning scheme is implemented using a PC-based measurement system without any synchronous circuit, nonuniform phase-shifted interference fringes are captured because of the fluctuation in the image-capturing interval. To cope with the nonuniform phase shifts, a statistical generalized phase-shifting approach is employed. Because the algorithm is designed to use an arbitrary phase shift, the nonuniform phase shifts do not obstruct object-wave retrieval. Moreover, multiple interference fringes can be obtained in a short time owing to the continuous fringe-scanning scheme. However, the wavefront calculation method is not designed for sequentially recorded interference fringes. To use multiple interference fringes appropriately, we develop a least-squares wavefront calculation method combined with corrections for the initial phase and the direction of phase rotation. We verify the proposed method by numerical simulations and optical experiments. The results show that the object wave with the same initial phase can be correctly reconstructed by using both phase correction methods simultaneously.
NASA Astrophysics Data System (ADS)
Puthankovilakam, Krishnaparvathy; Scharf, Toralf; Herzig, Hans Peter; Weichelt, Tina; Zeitner, Uwe; Vogler, Uwe; Voelkel, Reinhard
2015-03-01
The proximity printing industry is in real need of high resolution results and it can be done using Phase Shift Mask (PSM) or by applying Optical Proximity Correction (OPC). In our research we are trying to find out details of how light fields behind the structures of photo masks develop in order to determine the best conditions and designs for proximity printing. We focus here on parameters that are used in real situation with gaps up to 50 μm and structure sizes down to 2 μm. The light field evolution behind the structures is studied and delivers insight in to precisions and tolerances that need to be respected. It is the first time that an experimental analysis of light propagation through mask is presented in detail, which includes information on intensity and phase. The instrument we use is known as High Resolution Interference Microscopy (HRIM). HRIM is a Mach-Zehnder interferometer which is capable of recording three dimensional distributions of intensity and phase with diffraction limited resolution. Our characterization technique allows plotting the evolution of the desired light field and therefore printable structure till the desired proximity gap. In this paper we discuss in detail the evolution of intensity and phase fields of elbow or corner structure at different position behind a phase mask and interpret the main parameters. Of particular interest are tolerances against proximity gap variation and the resolution in printed structures.
NASA Astrophysics Data System (ADS)
Griesinger, Uwe A.; Pforr, Rainer; Knobloch, Juergen; Friedrich, Christoph M.
1999-12-01
Dual trench alternating phase shifting masks with an optimized value of the so-called shallow trench depth represents an interesting approach to overcome aerial image imbalances. In order to get a better understanding of the possibilities and limits of this approach, especially for 5X reduction, theoretical and experimental investigations were accomplished. In this paper experimental data obtained from 5X dual trench type alternating PSMs, using DUV-lithography are introduced and compared with 3D-mask simulations. The masks were fabricated with different etch depths and contain parts of typical DRAM patterns. Besides the transmission balancing also the phase balancing has an important influence on the effective process window of an alternating PSM. The effective phase error can be measured with an AIMS-system (MSM100). The comparison with simulated data allows the determination of the phase error. In a second step the influence of different balancing methods on phase and transmission were investigated with the TEMPEST mask simulator for unpolarized light. The optimization of the balancing with respect to the CD-bias, undercut and etch depth will be shown and a first approach of a sensitivity analysis will be presented.
A phase-shifting in-line digital holography of pre-magnification on imaging research
NASA Astrophysics Data System (ADS)
Lin, Qiaowen; Wang, Dayong; Rong, Lu; Wang, Yunxin; Zhao, Jie; Panezai, Spozmai
2013-12-01
A phase shifting digital holography with pre-magnification is designed. In order to fully utilize the bandwidth of the camera, a four-step phase-shifting digital holography is adopted to retrieve the complex distribution of the object. To further enhance the resolution of the reconstructed image without phase aberration, two microscope objectives (MOs) are placed in front of the object and the reference mirror. The MO in the reference arm provides parallel beam at the PZT plane thus improve the precision of the phase shifting. A 1951 USAF negative resolution target is used as the sample. Experiment result demonstrates the feasibility of the proposed method.
Correction of Errors in Polarization Based Dynamic Phase Shifting Interferometers
NASA Astrophysics Data System (ADS)
Kimbrough, Brad
2014-10-01
Polarization based interferometers for single snap-shot measurements allow single frame, quantitative phase acquisition for vibration insensitive measurements of optical surfaces. Application of these polarization based phase sensors requires the test and reference beams of the interferometer to be orthogonally polarized. As with all polarization based interferometers, these systems can suffer from phase dependent errors resulting from systematic polarization aberrations. This type of measurement error presents a particular challenge because it varies in magnitude both spatially and temporally between each measurement. In this article, a general discussion of phase calculation error is presented. We then present an algorithm that is capable of mitigating phase-dependent measurement errors on-the-fly. The algorithm implementation is non-iterative providing sensor frame rate limited phase calculations. Finally, results are presented for both a high numerical aperture system, where the residual error is reduced to the shot noise limit, and a system with significant birefringence in the test arm.
Modulation measuring profilometry with auto-synchronous phase shifting and vertical scanning.
Zhong, Min; Su, Xianyu; Chen, Wenjing; You, Zhisheng; Lu, Mingteng; Jing, Hailong
2014-12-29
To determine the shape of a complex object with vertical measurement mode and higher accuracy, a novel modulation measuring profilometry realizing auto-synchronous phase shifting and vertical scanning is proposed. Coaxial optical system for projection and observation instead of triangulation system is adopted to avoid shadow and occlusion. In the projecting system, sinusoidal grating is perpendicular to optical axis. For moving the grating along a direction at a certain angle to optical axis, 1D precision translation platform is applied to achieve purposes of both phase-shifting and vertical scanning. A series of fringe patterns with different modulation variations are captured by a CCD camera while scanning. The profile of the tested object can be reconstructed by the relationship between the height values and the modulation distributions. Unlike the previous method based on Fourier transform for 2D fringe pattern, the modulation maps are calculated from the intensity curve formed by the points with definite pixel coordinates in the captured fringe patterns. The paper gives the principle of the proposed method, the set-up of measurement system and the method for system calibration. Computer simulation and experiment results proved its feasibility. PMID:25607133
Phase-shift-controlled logic gates in Y-shaped nonlinearly coupled chains.
Assunção, T F; Nascimento, E M; Sombra, A S B; Lyra, M L
2016-02-01
We introduce a model system composed of two input discrete chains nonlinearly coupled to a single output chain which mimics the geometry of Y-shaped carbon nanotubes, photonic crystal wave guides, and DNA junctions. We explore the capability of the proposed system to perform logic gate operations based on the transmission of phase-shifted harmonic incoming waves. Within a tight-binding approach, we determine the exact transmission spectrum which exhibits a nonlinear induced bistability. Using a digitalization scheme of the output signal based on amplitude modulation, we show that AND, OR, and XOR logic operations can be achieved. Nonlinearity strongly favors the realization of logic operations in the regime of large wavelengths, while phase shifting is required for the OR logic gate to be realizable. A detailed analysis of the contrast ratio shows that optimal operation of the AND and OR logic gates takes place when the nonlinear response is the predominant physical property distinguishing the coupling and regular sites. These results point towards the possibility of Y-branched junctions to perform logic operations based on the transmission of traveling waves. PMID:26986342
Simultaneous phase-shifting interferometry: immune to azimuth error of fast-axes in retarder array.
Zheng, Donghui; Chen, Lei; Li, Jinpeng; Gu, Chenfeng; Zhu, Wenhua; Han, Zhigang
2015-11-20
Simultaneous phase-shifting interferometry based on a 2×2 retarder array with random fast-axes (RARF-SPSI) is proposed for real-time wavefront measurements. The retarder array is used as the phase-shift component, where the phase retardances are π/2, π, 3π/2, and 2π and the four fast-axes of the four retarders can be somewhat random. In this paper, the mathematical model of RARF-SPSI is built by using a Stokes vector and a Mueller matrix, the phase demodulation method through solving equations is derived, and the coefficient matrix of the equations that is associated with the azimuth of the fast-axes is calculated by Fourier analysis. Then the corresponding simulation analysis is executed. In the experiment, four simultaneous phase-shifting interferograms are captured and the phase distribution under test is demodulated through the proposed method. Compared with the four-bucket phase-shifting algorithm adopted in traditional simultaneous phase-shifting interferometry, the ripple error is suppressed well. The advantage of the proposed RARF-SPSI is that there is no need to calibrate the fast-axes of the phase-shift component before measuring; in other words, the phase demodulation error caused by the azimuth error of fast-axes is eliminated. PMID:26836541
Development of high-precision high-frequency phase-shifting circuit
NASA Astrophysics Data System (ADS)
Ye, Shuliang; Song, Jiaying; Zhang, Baowu; Qiu, Jian
2010-08-01
Phase-locked frequency multiplying technology is utilized to amplify 10MHz signal to 640MHz. Pulse inhibition method is then exploited to make high-frequency signal have a phase shift of 2π. 20MHz signal with 2π / 32 phase shift is output after 5 times flip frequency division. In order to optimize electromagnetic compatibility, signal integrity and power integrity of a high-speed circuit, system simulation is performed using HyperLynx, a specially EDA simulation software. A whole printed circuit board (PCB) was made under the guide of optimized simulation results. Phase-shift experiments show that the output of high-frequency phase-shifting circuit system is two-way signals with a frequency of 20.0001 MHz with 1.8ns time difference, i.e. two signals with 12.96°phase difference are obtained.
Phase sensitivity in deformed-state superposition considering nonlinear phase shifts
NASA Astrophysics Data System (ADS)
Berrada, K.
2016-07-01
We study the problem of the phase estimation for the deformation-state superposition (DSS) under perfect and lossy (due to a dissipative interaction of DSS with their environment) regimes. The study is also devoted to the phase enhancement of the quantum states resulting from a generalized non-linearity of the phase shifts, both without and with losses. We find that such a kind of superposition can give the smallest variance in the phase parameter in comparison with usual Schrödinger cat states in different order of non-linearity even if for a larger average number of photons. Due to the significance of how a system is quantum correlated with its environment in the construction of a scalable quantum computer, the entanglement between the DSS and its environment is investigated during the dissipation. We show that partial entanglement trapping occurs during the dynamics depending on the kind of deformation and mean photon number. These features make the DSS with a larger average number of photons a good candidate for implementation of schemes of quantum optics and information with high precision.
Arbel, Elad; Bilenca, Alberto
2015-01-01
Conventional low-magnification phase-contrast microscopy is an invaluable, yet a qualitative, imaging tool for the interrogation of transparent objects over a mesoscopic millimeter-scale field-of-view in physical and biological settings. Here, we demonstrate that introducing a compact, unbalanced phase-shifting Michelson interferometer into a standard reflected brightfield microscope equipped with low-power infinity-corrected objectives and white light illumination forms a phase mesoscope that retrieves remotely and quantitatively the reflection phase distribution of thin, transparent, and weakly scattering samples with high temporal (1.38 nm) and spatial (0.87 nm) axial-displacement sensitivity and micrometer lateral resolution (2.3 μm) across a mesoscopic field-of-view (2.25 × 1.19 mm2). Using the system, we evaluate the etch-depth uniformity of a large-area nanometer-thick glass grating and show quantitative mesoscopic maps of the optical thickness of human cancer cells without any area scanning. Furthermore, we provide proof-of-principle of the utility of the system for the quantitative monitoring of fluid dynamics within a wide region. PMID:26216719
NASA Astrophysics Data System (ADS)
Arbel, Elad; Bilenca, Alberto
2015-07-01
Conventional low-magnification phase-contrast microscopy is an invaluable, yet a qualitative, imaging tool for the interrogation of transparent objects over a mesoscopic millimeter-scale field-of-view in physical and biological settings. Here, we demonstrate that introducing a compact, unbalanced phase-shifting Michelson interferometer into a standard reflected brightfield microscope equipped with low-power infinity-corrected objectives and white light illumination forms a phase mesoscope that retrieves remotely and quantitatively the reflection phase distribution of thin, transparent, and weakly scattering samples with high temporal (1.38 nm) and spatial (0.87 nm) axial-displacement sensitivity and micrometer lateral resolution (2.3 μm) across a mesoscopic field-of-view (2.25 × 1.19 mm2). Using the system, we evaluate the etch-depth uniformity of a large-area nanometer-thick glass grating and show quantitative mesoscopic maps of the optical thickness of human cancer cells without any area scanning. Furthermore, we provide proof-of-principle of the utility of the system for the quantitative monitoring of fluid dynamics within a wide region.
A staggered differential phase-shift keying modulation format for 100Gbit/s applications.
Shao, Yufeng; Wen, Shuangchun; Chen, Lin; Li, Ying; Xu, Huiwen
2008-08-18
We propose and demonstrate by numerical simulation a new phase modulation format, the staggered differential phase-shift keying (SDPSK), for 100 Gbit/s applications. Non-return-to-zero (NRZ) SDPSK signals was generated by using two phase modulators, and return-to-zero (RZ) SDPSK signals with 50% duty cycle was generated by cascading a dual-arm Mach-Zehnder modulator. The demodulation of 2 bit/symbol can be simply achieved on 1 bit rate through only one Mach-Zehnder delay interferometer and a balanced receiver. By comparing the transmission characteristics of the two staggered phase modulation formats with those of NRZ-DPSK, RZ-DPSK, NRZ-DQPSK, and RZ-DQPSK, respectively, we show that, the SDPSK signal has similar chromatic dispersion and polarization-mode-dispersion tolerance to the DPSK signal with same NRZ or RZ shape, while the SDPSK signal has stronger nonlinear tolerance than the DPSK or DQPSK signal. In addition, the SDPSK signal has the best transmission performance when each signal was transmitted over 106km optical SMF+DCF, and then launched into a third-order Gaussian optical bandpass filter placed with beyond 125GHz bandwidth. PMID:18711532
NASA Astrophysics Data System (ADS)
Guo, Tong; Li, Feng; Chen, Jinping; Fu, Xing; Hu, Xiaotang
2016-07-01
Conventional multi-wavelength phase-shifting interferometry utilizes two or three monochromatic light sources, such as lasers, to realize the measurement of the surface topography with large discontinuity. In this paper, the white light source, with a single-chip CCD color camera, is used to accomplish multi-wavelength phase-shifting interferometry. In addition, we propose an algorithm which combines white light phase-shifting algorithm, equivalent wavelength method and fringe order method to achieve measuring and calibrating the micro-structures ranging from nanometer scale to micrometer scale. Finally, the proposed method is validated by a traceable step height standard.
NASA Astrophysics Data System (ADS)
Chen, Yi-Hung; Lee, Shu-Sheng; Hsu, I.-Hung; Tseng, Eddie; Lee, Chih-Kung
2007-12-01
Surface plasmon resonance (SPR) is a very important metrology in biology detection. Phase modulation is one of the SPR detection technologies and the sample changes can be recognized from the phase variation. It is able to detect very tiny bio sample variation due to its high sensitivity. In this study, the optical system design based on a paraboloidal lens-based surface plasmon resonance instrument will be used to control the SPR critical angle. The charge coupled device camera (CCD camera) will be used to record the images of the bio-reaction and (5,1) phase-shifting algorithm will be adopted to retrieve the phase fringes of the whole spot from the intensity maps. The combination of the angle control SPR system and the (5,1) phase-shifting algorithm will expand the whole spot detection ability from the intensity to phase modulation because the intensity maps are going to be recorded for the (5,1) phase-shifting algorithm calculation. The difference between (5,1) phase-shifting algorithm and Five-Step Algorithm1 is that (5,1) phase-shifting algorithm only needs one image map at one time during the bio reaction and Five-Step Algorithm requires five image maps. Therefore, (5,1) phase-shifting algorithm will reduce the process of experiment and the requirement of the memory. The different concentration alcohols were measured by the optical system to verify the (5,1) phase-shifting algorithm applied in SPR phase modulation measurement and to prove the idea is workable and successful.
Dong, Po; Gui, Chengcheng
2016-06-15
In coherent optical transmission, traveling-wave Mach-Zehnder modulators are commonly used to generate various advanced formats where the modulators are biased at the minimum transmission point. Here, we report that an optical isolation effect with lower backward transmission occurs under this condition. This concept is successfully demonstrated to achieve ∼7 dB isolation over a 90-nm wavelength span under binary phase-shift keying modulation using a commercial lithium niobate modulator. PMID:27304273
Accurate calculation of phase shifts for electron collisions with positive ions
NASA Astrophysics Data System (ADS)
Gien, T. T.
2003-06-01
The Harris-Nesbet variational method was considered for the calculation of phase shifts of electron collisions with hydrogen-like ions (Li2+, Be3+, and B4+). Calculations were carried out for both singlet and triplet scattering. Very accurate results of phase shift of electron collisions with these ionic targets were obtained for the first time for partial waves of L up to six. The phase shifts that we obtained for low partial wave (S, P, and D) scattering were compared with those available in the literature by a few other research groups employing different numerical methods.
Femtosecond inscription of phase-shifted gratings by overlaid fiber Bragg gratings.
Shamir, Avishay; Ishaaya, Amiel A
2016-05-01
Two slightly shifted gratings are inscribed, one over the other, in an SMF fiber with a femtosecond laser and a phase mask. The transmission spectrum of the complex structure is similar to that of a phase-shifted grating; yet, the fabrication process is fast and simple compared to standard methods. High-quality semi-phase-shifted gratings with -24 dB transmission loss and <100 pm transmission bandwidth are presented. Their application as highly narrow micro-resonators and notch filters seems feasible. PMID:27128063
Acoustic radiation force expressed using complex phase shifts and momentum-transfer cross sections.
Zhang, Likun; Marston, Philip L
2016-08-01
Acoustic radiation force is expressed using complex phase shifts of partial wave scattering functions and the momentum-transfer cross section, herein incorporated into acoustics from quantum mechanisms. Imaginary parts of the phase shifts represent dissipation in the object and/or in the boundary layer adjacent to the object. The formula simplifies the force as summation of functions of complex phase shifts of adjacent partial waves involving differences of real parts and sums of imaginary parts, providing an efficient way of exploring the force parameter-space. The formula for the force is proportional to a generalized momentum-transfer cross section for plane waves and no dissipation. PMID:27586777
Phase shifts to light are altered by antagonists to neuropeptide receptors.
Chan, Ryan K; Sterniczuk, Roxanne; Enkhbold, Yaruuna; Jeffers, Ryan T; Basu, Priyoneel; Duong, Bryan; Chow, Sue-Len; Smith, Victoria M; Antle, Michael C
2016-07-01
The mammalian circadian clock in the suprachiasmatic nucleus (SCN) is a heterogeneous structure. Two key populations of cells that receive retinal input and are believed to participate in circadian responses to light are cells that contain vasoactive intestinal polypeptide (VIP) and gastrin-releasing peptide (GRP). VIP acts primarily through the VPAC2 receptor, while GRP works primarily through the BB2 receptor. Both VIP and GRP phase shift the circadian clock in a manner similar to light when applied to the SCN, both in vivo and in vitro, indicating that they are sufficient to elicit photic-like phase shifts. However, it is not known if they are necessary signals for light to elicit phase shifts. Here we test the hypothesis that GRP and VIP are necessary signaling components for the photic phase shifting of the hamster circadian clock by examining two antagonists for each of these neuropeptides. The BB2 antagonist PD176252 had no effect on light-induced delays on its own, while the BB2 antagonist RC-3095 had the unexpected effect of significantly potentiating both phase delays and advances. Neither of the VIP antagonists ([d-p-Cl-Phe6, Leu17]-VIP, or PG99-465) altered phase shifting responses to light on their own. When the BB2 antagonist PD176252 and the VPAC2 antagonist PG99-465 were delivered together to the SCN, phase delays were significantly attenuated. These results indicate that photic phase shifting requires participation of either VIP or GRP; phase shifts to light are only impaired when signalling in both pathways are inhibited. Additionally, the unexpected potentiation of light-induced phase shifts by RC-3095 should be investigated further for potential chronobiotic applications. PMID:27090819
Diffractive phase-shift lithography photomask operating in proximity printing mode.
Cirino, Giuseppe A; Mansano, Ronaldo D; Verdonck, Patrick; Cescato, Lucila; Neto, Luiz G
2010-08-01
A phase shift proximity printing lithographic mask is designed, manufactured and tested. Its design is based on a Fresnel computer-generated hologram, employing the scalar diffraction theory. The obtained amplitude and phase distributions were mapped into discrete levels. In addition, a coding scheme using sub-cells structure was employed in order to increase the number of discrete levels, thus increasing the degree of freedom in the resulting mask. The mask is fabricated on a fused silica substrate and an amorphous hydrogenated carbon (a:C-H) thin film which act as amplitude modulation agent. The lithographic image is projected onto a resist coated silicon wafer, placed at a distance of 50 microm behind the mask. The results show a improvement of the achieved resolution--linewidth as good as 1.5 microm--what is impossible to obtain with traditional binary masks in proximity printing mode. Such achieved dimensions can be used in the fabrication of MEMS and MOEMS devices. These results are obtained with a UV laser but also with a small arc lamp light source exploring the partial coherence of this source. PMID:20721026
Pattern-dependent correction of mask topography effects for alternating phase-shifting masks
NASA Astrophysics Data System (ADS)
Ferguson, Richard A.; Wong, Alfred K. K.; Brunner, Timothy A.; Liebmann, Lars W.
1995-05-01
Strategies for modifying both mask fabrication processes and design data for alternating phase-shifting masks to account for mask scattering phenomena are explored. Results were derived from the rigorous solution of Maxwell's equations using the EMFlex and TEMPEST programs for an etched-quartz fabrications process. By importing the resulting diffracted orders into VCIMAGE, full vector calculation of the aerial image from mask to wafer was obtained. From the rigorous mask simulations, the 0th and 1st diffracted orders were translated into an effective transmission and phase based on a thin-mask approximation. With this analysis technique, a 0.25 micrometers line-space grating for the baseline etched-quartz process (4X magnification) showed a transmission error of 7.2% and a phase error of 1.6 degree(s). In order to compensate for these errors, etch-back fabrication techniques, in which the quartz was recessed beneath the chrome, were evaluated to determine the extent to which the transmission and phase errors could be reduced. For the dual etch-back process typically in use today, a residual transmission error of approximately 0.5% could not be completely removed, even for etch-back depths greater than 200 nm. Correction of the phase errors was achieved by reducing the reactive-ion etch depth by 2-3 nm. Design manipulation, in which the 180 degree(s) opening was increased in size, required feature-dependent phase errors as large as 1 degree(s) were present.
EMP-002a Phase Shift through the Ionosphere
Soltz, R.; Simons, D.; Fenimore, E.; Wilks, S.; Carey, T.
2015-10-20
In this note we review the derivation and use of the Ionospheric Transfer Function (ITF) in the DIO- RAMA model to calculate the propagation of a broad band ElectroMagnetic Pulse (EMP) through the Ionosphere in the limit of geometric optics. This note is intended to resolve a misunderstanding between the NDS VVA and EMP modeling teams regarding the appropriate use of the phase and group velocities in DIORAMA. The di erent approaches are documented in EMP-002 note, \\Phase vs. Group" [1], generated by the LLNL DIORAMA VVA team, and the subsequent response from the DIORAMA EMP modeling team' [2].
Surface characterization based on optical phase shifting interferometry
Mello, Michael , Rosakis; Ares J.
2011-08-02
Apparatus, techniques and systems for implementing an optical interferometer to measure surfaces, including mapping of instantaneous curvature or in-plane and out-of-plane displacement field gradients of a sample surface based on obtaining and processing four optical interferograms from a common optical reflected beam from the sample surface that are relatively separated in phase by .pi./2.
Kuo, Wen-Kai; Syu, Siang-He; Lin, Peng-Zhi; Yu, Hsin Her
2016-02-01
This paper reports on a transmitted-type dual-channel guided-mode resonance (GMR) sensor system that uses phase-shifting interferometry (PSI) to achieve tunable phase detection sensitivity. Five interference images are captured for the PSI phase calculation within ∼15 s by using a liquid crystal retarder and a USB web camera. The GMR sensor structure is formed by a nanoimprinting process, and the dual-channel sensor device structure for molding is fabricated using a 3D printer. By changing the rotation angle of the analyzer in front of the camera in the PSI system, the sensor detection sensitivity can be tuned. The proposed system may achieve high throughput as well as high sensitivity. The experimental results show that an optimal detection sensitivity of 6.82×10(-4) RIU can be achieved. PMID:26836099
Chronic ethanol intake alters circadian phase shifting and free-running period in mice.
Seggio, Joseph A; Fixaris, Michael C; Reed, Jeffrey D; Logan, Ryan W; Rosenwasser, Alan M
2009-08-01
Chronic alcohol intake is associated with widespread disruptions in sleep and circadian rhythms in both human alcoholics and in experimental animals. Recent studies have demonstrated that chronic and acute ethanol treatments alter fundamental properties of the circadian pacemaker--including free-running period and responsiveness to photic and nonphotic phase-shifting stimuli--in rats and hamsters. In the present work, the authors extend these observations to the C57BL/6J mouse, an inbred strain characterized by very high levels of voluntary ethanol intake and by reliable and stable free-running circadian activity rhythms. Mice were housed individually in running-wheel cages under conditions of either voluntary or forced ethanol intake, whereas controls were maintained on plain water. Forced ethanol intake significantly attenuated photic phase delays (but not phase advances) and shortened free-running period in constant darkness, but voluntary ethanol intake failed to affect either of these parameters. Thus, high levels of chronic ethanol intake, beyond those normally achieved under voluntary drinking conditions, are required to alter fundamental circadian pacemaker properties in C57BL/6J mice. These observations may be related to the relative ethanol insensitivity displayed by this strain in several other phenotypic domains, including ethanol-induced sedation, ataxia, and withdrawal. Additional experiments will investigate chronobiological sensitivity to ethanol in a range of inbred strains showing diverse ethanol-related phenotypes. PMID:19625732
Chronic Ethanol Intake Alters Circadian Phase Shifting and Free-Running Period in Mice
Seggio, Joseph A.; Fixaris, Michael C.; Reed, Jeffrey D.; Logan, Ryan W.; Rosenwasser, Alan M.
2011-01-01
Chronic alcohol intake is associated with widespread disruptions in sleep and circadian rhythms in both human alcoholics and in experimental animals. Recent studies have demonstrated that chronic and acute ethanol treatments alter fundamental properties of the circadian pacemaker—including free-running period and responsiveness to photic and nonphotic phase-shifting stimuli—in rats and hamsters. In the present work, the authors extend these observations to the C57BL/6J mouse, an inbred strain characterized by very high levels of voluntary ethanol intake and by reliable and stable free-running circadian activity rhythms. Mice were housed individually in running-wheel cages under conditions of either voluntary or forced ethanol intake, whereas controls were maintained on plain water. Forced ethanol intake significantly attenuated photic phase delays (but not phase advances) and shortened free-running period in constant darkness, but voluntary ethanol intake failed to affect either of these parameters. Thus, high levels of chronic ethanol intake, beyond those normally achieved under voluntary drinking conditions, are required to alter fundamental circadian pacemaker properties in C57BL/6J mice. These observations may be related to the relative ethanol insensitivity displayed by this strain in several other phenotypic domains, including ethanol-induced sedation, ataxia, and withdrawal. Additional experiments will investigate chronobiological sensitivity to ethanol in a range of inbred strains showing diverse ethanol-related phenotypes. PMID:19625732
Humphrey, E; Phatak, C; Petford-Long, A K; De Graef, M
2014-04-01
We introduce a new approach for the separation of the electrostatic and magnetic components of the electron wave phase shift, based on the transport-of-intensity equation (TIE) formalism. We derive two separate TIE-like equations, one for each of the phase shift components. We use experimental results on FeCoB and Permalloy patterned islands to illustrate how the magnetic and electrostatic longitudinal derivatives can be computed. The main advantage of this new approach is the fact that the differences in the power spectra of the two phase components (electrostatic phase shifts often have significant power in the higher frequencies) can be accommodated by the selection of two different Tikhonov regularization parameters for the two phase reconstructions. The extra computational demands of the method are more than compensated by the improved phase reconstruction results. PMID:24513573
Transverse spatial phase-shifting method used in vibration-compensated interferometer
NASA Astrophysics Data System (ADS)
Wu, Dong; Zhu, Ri-Hong; Chen, Lei; Li, Jin-Yun
Based on the conception of temporal phase-shifting interferometry, we have developed a novel technique named transverse spatial phase-shifting method. Only using four photoelectric detectors with a certain spatial array, the method can directly detect wavefront phase variation due to external vibrations. As soon as wavefront variation was determined, some feedback control could be put on interferometer to compensate the vibrations. This method was applied to a Twyman-Green phase-shifting interferometer in which an adaptive vibration-compensated system has been built, it calibrated wavefront phase in real time by a piezoelectric transducer used as both wavefront phase shifter and vibration feedback device, thus fringe pattern could be stabilized and the optical testing would be carried out. Some experimental results were presented.
Optical π phase shift created with a single-photon pulse
Tiarks, Daniel; Schmidt, Steffen; Rempe, Gerhard; Dürr, Stephan
2016-01-01
A deterministic photon-photon quantum logic gate is a long-standing goal. Building such a gate becomes possible if a light pulse containing only one photon imprints a phase shift of π onto another light field. We experimentally demonstrate the generation of such a π phase shift with a single-photon pulse. A first light pulse containing less than one photon on average is stored in an atomic gas. Rydberg blockade combined with electromagnetically induced transparency creates a phase shift for a second light pulse, which propagates through the medium. We measure the π phase shift of the second pulse when we postselect the data upon the detection of a retrieved photon from the first pulse. This demonstrates a crucial step toward a photon-photon gate and offers a variety of applications in the field of quantum information processing. PMID:27386511
Vehicular motion in 2D city traffic network with signals controlled by phase shift
NASA Astrophysics Data System (ADS)
Komada, Kazuhito; Kojima, Kengo; Nagatani, Takashi
2011-03-01
We study the dynamic behavior of vehicular traffic through the series of traffic lights controlled by phase shift in two-dimensional (2D) city traffic network. The nonlinear-map model is presented for the vehicular traffic. The city traffic network is made of one-way perpendicular streets arranged in a square lattice with traffic signals where vertical streets are oriented upwards and horizontal streets are oriented rightwards. There are two traffic lights for the movement to north or that to east at each crossing. The traffic lights are controlled by the cycle time, split, and phase shift. The vehicle moves through the series of signals on a path selected by the driver. The city traffic with a heterogeneous density distribution is also studied. The dependence of the arrival time on cycle time, split, phase shift, selected path, and density is clarified for 2D city traffic. It is shown that the vehicular traffic is efficiently controlled by the phase shift.
The phase-shift of isospin-2 pi-pi scattering from lattice QCD
Jozef J. Dudek, Robert G. Edwards, Michael J. Peardon, David G. Richards, Christopher E. Thomas
2011-04-01
Finite-volume lattice QCD calculations offer the possibility of extracting resonance parameters from the energy-dependent elastic phase-shift computed using the L\\"uscher technique. In this letter, as a trial of the method, we report on the extraction of the non-resonant phase-shift for $S$ and $D$-wave $\\pi\\pi$ isospin-2 scattering from dynamical lattice QCD computations. We define a variational basis of operators resembling pairs of pions of definite relative momentum and extract a spectrum of excited states that maps to phase-shifts at a set of discrete scattering momenta. Computations are performed with pion masses between $400$ and $520$ MeV on multiple spatial volumes. We observe no significant quark mass dependence in the phase-shifts extracted which are in reasonable agreement with the available experimental data at low momentum.
Optical π phase shift created with a single-photon pulse.
Tiarks, Daniel; Schmidt, Steffen; Rempe, Gerhard; Dürr, Stephan
2016-04-01
A deterministic photon-photon quantum logic gate is a long-standing goal. Building such a gate becomes possible if a light pulse containing only one photon imprints a phase shift of π onto another light field. We experimentally demonstrate the generation of such a π phase shift with a single-photon pulse. A first light pulse containing less than one photon on average is stored in an atomic gas. Rydberg blockade combined with electromagnetically induced transparency creates a phase shift for a second light pulse, which propagates through the medium. We measure the π phase shift of the second pulse when we postselect the data upon the detection of a retrieved photon from the first pulse. This demonstrates a crucial step toward a photon-photon gate and offers a variety of applications in the field of quantum information processing. PMID:27386511
Phase shift of isospin-2 {pi}{pi} scattering from lattice QCD
Dudek, Jozef J.; Edwards, Robert G.; Richards, David G.; Thomas, Christopher E.; Peardon, Michael J.
2011-04-01
Finite-volume lattice QCD calculations offer the possibility of extracting resonance parameters from the energy-dependent elastic phase-shift computed using the Luescher technique. In this letter, as a trial of the method, we report on the extraction of the nonresonant phase-shift for S and D-wave {pi}{pi} isospin-2 scattering from dynamical lattice QCD computations. We define a variational basis of operators resembling pairs of pions of definite relative momentum and extract a spectrum of excited states that maps to phase-shifts at a set of discrete scattering momenta. Computations are performed with pion masses between 400 and 520 MeV on multiple spatial volumes. We observe no significant quark mass dependence in the phase-shifts extracted which are in reasonable agreement with the available experimental data at low momentum.
Phase-shift, stimuli-responsive drug carriers for targeted delivery
O’Neill, Brian E; Rapoport, Natalya
2011-01-01
The intersection of particles and directed energy is a rich source of novel and useful technology that is only recently being realized for medicine. One of the most promising applications is directed drug delivery. This review focuses on phase-shift nanoparticles (that is, particles of submicron size) as well as micron-scale particles whose action depends on an external-energy triggered, first-order phase shift from a liquid to gas state of either the particle itself or of the surrounding medium. These particles have tremendous potential for actively disrupting their environment for altering transport properties and unloading drugs. This review covers in detail ultrasound and laser-activated phase-shift nano- and micro-particles and their use in drug delivery. Phase-shift based drug-delivery mechanisms and competing technologies are discussed. PMID:22059114
Double input capacitively coupled contactless conductivity detector with phase shift.
Zheng, Hao; Li, Meng; Dai, Jianyuan; Wang, Zhen; Li, Xiuting; Yuan, Hongyan; Xiao, Dan
2014-10-21
A double input capacitively coupled contactless conductivity detector (DIC(4)D) device which gets higher sensitivity has been described in this paper. The detector consists of two input electrodes and one output electrode. When two alternating current (AC) voltages with the same amplitude and different phases are imposed on each input electrode, the equivalent resistance of the output electrode is reduced because of the interference of the two signals with different phase angles. For a capacitively coupled contactless conductivity detector (C(4)D), the ratio of the response of KCl solution to that of distilled water is 1.6. However, for DIC(4)D, the ratio is 1.55 at a phase difference of 0° and increases to 1.8 at the phase difference of 170°, respectively. For C(4)D, the response of KCl solution is a linear function of the logarithm of concentrations from 10(-5) M to 10(-2) M, and the slope is 5.58. However, the slope of the response increases to 7.13 in DIC(4)D, and the limit of detection (LOD) of DIC(4)D is estimated to be 5 × 10(-8) M. The slope of the three-way DIC(4)D is increased to 69.78. A flow injection device is employed for the evaluation of the applicability of DIC(4)D with the same range, and good reproducibility is confirmed through flow injection of the same solution 10 times. The relative standard deviation (RSD) is 0.7%, which demonstrates a promising application to capillary electrophoresis (CE). PMID:25250534
NASA Astrophysics Data System (ADS)
Okayama, Hideaki; Onawa, Yosuke; Shimura, Daisuke; Yaegashi, Hiroki; Sasaki, Hironori
2016-08-01
We describe a Bragg grating with a phase shift section and a sampled grating scheme that converts input polarization to orthogonal polarization. A very narrow polarization-independent wavelength peak can be generated by phase shift structures and polarization-independent multiple diffraction peaks by sampled gratings. The characteristics of the device were examined by transfer matrix and finite-difference time-domain methods.
Phase-shift measurments for second-harmonic generation in glass
NASA Astrophysics Data System (ADS)
Dominic, Vincent G.; Feinberg, Jack
1993-12-01
Focusing intense laser light along with some of its second harmonic into a glass sample transforms the glass into a frequency doubler. We present a new method to measure the optical phase shift between the second-harmonic beam used to seed the glass and the second- harmonic beam subsequently produced by the glass sample. Determination of this phase shift is essential for understanding the growth dynamics of the effect, and its value can discriminate between proposed theoretical models.
Error analysis of the phase-shifting technique when applied to shadow moire
Han, Changwoon; Han Bongtae
2006-02-20
An exact solution for the intensity distribution of shadow moire fringes produced by a broad spectrum light is presented. A mathematical study quantifies errors in fractional fringe orders determined by the phase-shifting technique, and its validity is corroborated experimentally. The errors vary cyclically as the distance between the reference grating and the specimen increases. The amplitude of the maximum error is approximately 0.017 fringe, which defines the theoretical limit of resolution enhancement offered by the phase-shifting technique.
Method for the manufacture of phase shifting masks for EUV lithography
Stearns, Daniel G.; Sweeney, Donald W.; Mirkarimi, Paul B.; Barty, Anton
2006-04-04
A method for fabricating an EUV phase shift mask is provided that includes a substrate upon which is deposited a thin film multilayer coating that has a complex-valued reflectance. An absorber layer or a buffer layer is attached onto the thin film multilayer, and the thickness of the thin film multilayer coating is altered to introduce a direct modulation in the complex-valued reflectance to produce phase shifting features.
Phase-Dependent Shifting of the Adrenal Clock by Acute Stress-Induced ACTH.
Engeland, William C; Yoder, J Marina; Karsten, Carley A; Kofuji, Paulo
2016-01-01
The adrenal cortex has a molecular clock that generates circadian rhythms in glucocorticoid production, yet it is unclear how the clock responds to acute stress. We hypothesized that stress-induced ACTH provides a signal that phase shifts the adrenal clock. To assess whether acute stress phase shifts the adrenal clock in vivo in a phase-dependent manner, mPER2:LUC mice on a 12:12-h light:dark cycle underwent restraint stress for 15 min or no stress at zeitgeber time (ZT) 2 (early subjective day) or at ZT16 (early subjective night). Adrenal explants from mice stressed at ZT2 showed mPER2:LUC rhythms that were phase-advanced by ~2 h, whereas adrenals from mice stressed at ZT16 showed rhythms that were phase-delayed by ~2 h. The biphasic response was also observed in mice injected subcutaneously either with saline or with ACTH at ZT2 or ZT16. Blockade of the ACTH response with the glucocorticoid, dexamethasone, prevented restraint stress-induced phase shifts in the mPER2:LUC rhythm both at ZT2 and at ZT16. The finding that acute stress results in a phase-dependent shift in the adrenal mPER2:LUC rhythm that can be blocked by dexamethasone indicates that stress-induced effectors, including ACTH, act to phase shift the adrenal clock rhythm. PMID:27445984
Phase-Dependent Shifting of the Adrenal Clock by Acute Stress-Induced ACTH
Engeland, William C.; Yoder, J. Marina; Karsten, Carley A.; Kofuji, Paulo
2016-01-01
The adrenal cortex has a molecular clock that generates circadian rhythms in glucocorticoid production, yet it is unclear how the clock responds to acute stress. We hypothesized that stress-induced ACTH provides a signal that phase shifts the adrenal clock. To assess whether acute stress phase shifts the adrenal clock in vivo in a phase-dependent manner, mPER2:LUC mice on a 12:12-h light:dark cycle underwent restraint stress for 15 min or no stress at zeitgeber time (ZT) 2 (early subjective day) or at ZT16 (early subjective night). Adrenal explants from mice stressed at ZT2 showed mPER2:LUC rhythms that were phase-advanced by ~2 h, whereas adrenals from mice stressed at ZT16 showed rhythms that were phase-delayed by ~2 h. The biphasic response was also observed in mice injected subcutaneously either with saline or with ACTH at ZT2 or ZT16. Blockade of the ACTH response with the glucocorticoid, dexamethasone, prevented restraint stress-induced phase shifts in the mPER2:LUC rhythm both at ZT2 and at ZT16. The finding that acute stress results in a phase-dependent shift in the adrenal mPER2:LUC rhythm that can be blocked by dexamethasone indicates that stress-induced effectors, including ACTH, act to phase shift the adrenal clock rhythm. PMID:27445984
Canceling the momentum in a phase-shifting algorithm to eliminate spatially uniform errors.
Hibino, Kenichi; Kim, Yangjin
2016-08-10
In phase-shifting interferometry, phase modulation nonlinearity causes both spatially uniform and nonuniform errors in the measured phase. Conventional linear-detuning error-compensating algorithms only eliminate the spatially variable error component. The uniform error is proportional to the inertial momentum of the data-sampling weight of a phase-shifting algorithm. This paper proposes a design approach to cancel the momentum by using characteristic polynomials in the Z-transform space and shows that an arbitrary M-frame algorithm can be modified to a new (M+2)-frame algorithm that acquires new symmetry to eliminate the uniform error. PMID:27534475
NASA Astrophysics Data System (ADS)
Liu, Shifeng; Zhu, Dan; Pan, Shilong
2014-03-01
A wideband signal upconversion and phase shifting scheme based on a frequency tunable optoelectronic oscillator (OEO) are proposed and demonstrated. The OEO performs simultaneously tunable high-quality local oscillator (LO) signal generation, wideband frequency upconversion, and phase shifting within the whole 2π range. With the generated LO tuning from 9.549 to 11.655 GHz, wideband square signals are successfully upconverted to the X band. The phase of the upconverted signal is tuned from 0 to 360 deg. The phase noise of the oscillation signal is about -104 dBc/Hz at 10 kHz offset with or without the injected baseband signal.
Bowman, Michael K.; Maryasov, Alexander G.
2007-04-01
The off-resonant pump pulse used in double electron electron resonance (DEER) measurements produces dynamic phase shifts that are explained here by simple analytic and vector descriptions of the full range of signal behaviors observed during DEER measurements, including: large phase shifts in the signal; changes in the position and shape of the detected echo; and changes in the signal intensity. The dynamic phase shifts depend on the width, amplitude and offset frequency of the pump pulse. Isolated radicals as well as pairs or clusters of dipolar-coupled radicals have the same dynamic phase shift that is independent of pump pulse delay in a typical measurement. A method of calibrating both the pump pulse offset frequency and the pump pulse field strength is outlined. A vector model is presented that explains the dynamic phase shifts in terms of precessing magnetization that is either spin locked or precessing about the effective pump field during the pump pulse. Implications of the dynamic phase shifts are discussed as they relate to setting up, calibrating and interpreting the results of DEER measurements.
vanderLeest, Henk Tjebbe; Rohling, Jos H. T.; Michel, Stephan; Meijer, Johanna H.
2009-01-01
Background In mammals, a major circadian pacemaker that drives daily rhythms is located in the suprachiasmatic nuclei (SCN), at the base of the hypothalamus. The SCN receive direct light input via the retino-hypothalamic tract. Light during the early night induces phase delays of circadian rhythms while during the late night it leads to phase advances. The effects of light on the circadian system are strongly dependent on the photoperiod to which animals are exposed. An explanation for this phenomenon is currently lacking. Methodology and Principal Findings We recorded running wheel activity in C57 mice and observed large amplitude phase shifts in short photoperiods and small shifts in long photoperiods. We investigated whether these different light responses under short and long days are expressed within the SCN by electrophysiological recordings of electrical impulse frequency in SCN slices. Application of N-methyl-D-aspartate (NMDA) induced sustained increments in electrical activity that were not significantly different in the slices from long and short photoperiods. These responses led to large phase shifts in slices from short days and small phase shifts in slices from long days. An analysis of neuronal subpopulation activity revealed that in short days the amplitude of the rhythm was larger than in long days. Conclusions The data indicate that the photoperiodic dependent phase responses are intrinsic to the SCN. In contrast to earlier predictions from limit cycle theory, we observed large phase shifting responses in high amplitude rhythms in slices from short days, and small shifts in low amplitude rhythms in slices from long days. We conclude that the photoperiodic dependent phase responses are determined by the SCN and propose that synchronization among SCN neurons enhances the phase shifting capacity of the circadian system. PMID:19305510
NASA Astrophysics Data System (ADS)
Curty, Marcos; Tamaki, Kiyoshi; Moroder, Tobias; Gómez-Sousa, Hipólito
2009-04-01
In this paper we present limitations imposed by sequential attacks on the maximal distance achievable by a differential-phase-shift (DPS) quantum key distribution (QKD) protocol with weak coherent pulses. Specifically, we compare the performance of two possible sequential attacks against DPS QKD where Eve realizes, respectively, optimal unambiguous state discrimination of Alice's signal states, and optimal unambiguous discrimination of the relative phases between consecutive signal states. We show that the second eavesdropping strategy provides tighter upper bounds for the security of a DPS QKD scheme than the former one.
Redshift controversy in atom interferometry: representation dependence of the origin of phase shift.
Schleich, Wolfgang P; Greenberger, Daniel M; Rasel, Ernst M
2013-01-01
Motivated by the recent debate on whether the Kasevich-Chu atom interferometer can measure the gravitational redshift, we show that in different representations of quantum mechanics chosen for the calculation, the observed phase shift appears as though it originates from different physical phenomena. In particular, we demonstrate that the decomposition of the total phase shift into three dynamical phases, which emerges in a semiclassical approach and is at the very heart of the redshift controversy, does not appear in an exact treatment based on a representation-free analysis. Here only two phenomena determine the phase shift: the difference of the laser phases and the acceleration of the atom. Hence, the Kasevich-Chu interferometer is an accelerometer or gravimeter. PMID:23383761
Du, Hubing; Gao, Honghong
2016-08-20
Affected by the height dependent effects, the phase-shifting shadow moiré can only be implemented in an approximate way. In the technique, a fixed phase step around π/2 rad between two adjacent frames is usually introduced by a grating translation in its own plane. So the method is not flexible in some situations. Additionally, because the shadow moiré fringes have a complex intensity distribution, computing the introduced phase shift from the existing arccosine function or arcsine function-based phase shift extraction algorithm always exhibits instability. To solve it, we developed a Gram-Schmidt orthonormalization approach based on a three-frame self-calibration phase-shifting algorithm with equal but unknown phase steps. The proposed method using the arctangent function is fast and can be implemented robustly in many applications. We also do optical experiments to demonstrate the correction of the proposed method by referring to the result of the conventional five-step phase-shifting shadow moiré. The results show the correctness of the proposed method. PMID:27556993
Phase shifting and the beating of complex waves
NASA Astrophysics Data System (ADS)
Keeports, David
2011-03-01
At the introductory level, the demonstration and analysis of sound beating is usually limited to the superposition of two purely sinusoidal waves with equal amplitudes and very similar frequencies. Under such conditions, an observer hears the periodic variation of the loudness of a sound with an unchanging timbre. On the other hand, when complex waves with very similar frequencies are superimposed, each harmonic beats with a frequency proportional to the frequency of the harmonic. Consequently, the resulting sound exhibits a subtle variation of timbre with time. This article extends the normal introductory discussion of beating and explains why electronic phase shifters, devices familiar to many musicians, can produce the sound of beating complex waves.
Tunable graphene metasurfaces by discontinuous Pancharatnam-Berry phase shift
NASA Astrophysics Data System (ADS)
Hu, Xin; Wen, Long; Song, Shichao; Chen, Qin
2015-12-01
Metal-dielectric-graphene three-layer structures are proposed to improve the interaction of graphene micro- and nanostructures with incident waves, as the upper graphene cut-wire layer introduces a discontinuous Pancharatnam-Berry phase profile. A semi-analytical method based on the Jones calculus is conducted to investigate the conversion efficiency of cross-polarized light on this graphene metasurface for circularly polarized wave incidence, which predicts that the physical constraint (25%) of cross-coupling conversion efficiency for individual graphene layers can be overcome. Numerical simulations confirm the conclusion and demonstrate an efficiency as high as 60%. Based on this mechanism, high-efficiency anomalous reflection surfaces and flat focal mirrors are designed with the tunability of reflection angles and one order of magnitude improved focusing intensity. This method paves the way to engineering high-efficiency graphene metasurfaces for tunable electromagnetic wave manipulation.
Tunable graphene metasurfaces by discontinuous Pancharatnam-Berry phase shift.
Hu, Xin; Wen, Long; Song, Shichao; Chen, Qin
2015-12-18
Metal-dielectric-graphene three-layer structures are proposed to improve the interaction of graphene micro- and nanostructures with incident waves, as the upper graphene cut-wire layer introduces a discontinuous Pancharatnam-Berry phase profile. A semi-analytical method based on the Jones calculus is conducted to investigate the conversion efficiency of cross-polarized light on this graphene metasurface for circularly polarized wave incidence, which predicts that the physical constraint (25%) of cross-coupling conversion efficiency for individual graphene layers can be overcome. Numerical simulations confirm the conclusion and demonstrate an efficiency as high as 60%. Based on this mechanism, high-efficiency anomalous reflection surfaces and flat focal mirrors are designed with the tunability of reflection angles and one order of magnitude improved focusing intensity. This method paves the way to engineering high-efficiency graphene metasurfaces for tunable electromagnetic wave manipulation. PMID:26585113
Core stress distribution of phase shifting multimode polymer optical fiber
Furukawa, Rei Matsuura, Motoharu; Nagata, Morio; Mishima, Kenji; Inoue, Azusa; Tagaya, Akihiro; Koike, Yasuhiro
2013-11-18
Poly-(methyl methacrylate-co-benzyl methacrylate) polarization-maintaining optical fibers are known for their high response to normal stress. In this report, responses to higher stress levels up to 0.45 MPa were investigated. The stress amplitude and direction in the fiber cross section were calculated and analyzed with a coincident mode-field obtained from the near-field pattern. The stress amplitude varies significantly in the horizontal direction and is considered to create multiple phases, explaining the measurement results. To investigate possible permanent deformation, the core yield point profile was analyzed. Although it largely exceeds the average applied stress, the calculated stress distribution indicates that the core could partially experience stress that exceeds the yield point.
Tunable phase-shifted fiber Bragg grating based on femtosecond laser fabricated in-grating bubble.
Liao, Changrui; Xu, Lei; Wang, Chao; Wang, D N; Wang, Yiping; Wang, Qiao; Yang, Kaiming; Li, Zhengyong; Zhong, Xiaoyong; Zhou, Jiangtao; Liu, Yingjie
2013-11-01
We present a type of phase-shifted fiber Bragg gratings based on an in-grating bubble fabricated by femtosecond (fs) laser ablation together with a fusion-splicing technique. A microchannel vertically crossing the bubble is drilled by fs laser to allow liquid to flow in or out. By filling different refractive index (RI) liquid into the bubble, the phase-shift peak is found to experience a linear red shift with the increase of RI, while little contribution to the change of phase shift comes from the temperature and axial strain. Therefore, such a PS-FBG could be used to develop a promising tunable optical filter and sensor. PMID:24177122
Liu, Fengwei; Wu, Yongqian; Wu, Fan
2015-04-20
The accuracy of phase-shifting interferometers (PSI) is crippled by nonlinearity of the phase shifter and instability of the environment such as vibration and air turbulence. A general algorithm, utilizing Lissajous figures and ellipse fitting, of correcting the phase extraction error in the phase shifting interferometry is described in this paper. By plotting N against D, where N and D represent the numerator and denominator terms of the phase extraction function (i.e. an arctangent function) respectively, a Lissajous ellipse is created. Once the parameters of the ellipse are determined by ellipse fitting, one can transform the ellipse to a unit circle (ETC). Through this process the phase extraction error caused by random phase shift errors can be corrected successfully. Proposed method is non-iterated, adapts to all phase shifting algorithms (PSAs), and has high accuracy. Some factors that may affect the performance of proposed method are discussed in numerical simulations. Optical experiments are implemented to validate the effectiveness of proposed algorithm. PMID:25969117
A binary phase-shift keying receiver for the detection of attention to human speech.
Lopez-Gordo, M A; Pelayo, F
2013-08-01
Synthetic sounds, tone-beeps, vowels or syllables are typically used in the assessment of attention to auditory stimuli because they evoke a set of well-known event-related potentials, whose characteristics can be statistically contrasted. Such approach rules out the use of stimuli with non-predictable response, such as human speech. In this study we present a procedure based on the robust binary phase-shift keying (BPSK) receiver that permits the real-time detection of selective attention to human speeches in dichotic listening tasks. The goal was achieved by tagging the speeches with two barely-audible tags whose joined EEG response constitutes a reliable BPSK constellation, which can be detected by means of a BPSK receiver. The results confirmed the expected generation of the BPSK constellation by the human auditory system. Also, the bit-error rate and the information transmission rate achieved in the detection of attention fairly followed the expected curves and equations of the standard BPSK receiver. Actually, it was possible to detect attention as well as the estimation a priori of its accuracy based on the signal-to-noise ratio of the BPSK signals. This procedure, which permits the detection of the attention to human speeches, can be of interest for new potential applications, such as brain-computer interfaces, clinical assessment of the attention in real time or for entertainment. PMID:23746289
Target tracking using log-polar transform-based shifted phase-encoded joint transform correlation
NASA Astrophysics Data System (ADS)
Islam, Mohammed Nazrul; Bitew, Worku T.
2014-04-01
Automatic target detection and tracking requires efficient recognition of the target pattern in variable environmental conditions. Optical joint transform correlation (JTC) method has been proven to be efficient in recognizing a target without requiring complex optical set up. However, the classical JTC suffers from poor correlation performance, which can be improved through the use of different and modified designs. A very successful scheme is developed by employing phase-shifted and phase-encoded fringe-adjusted JTC (SPFJTC), which provides with a high discrimination between a target and non-target objects in a given scene and better utilization of the space-bandwidth resource. Further enhancement of the target detection performance can be achieved by incorporating log-polar transform in the SPFJTC technique. We applied the SPFJTC technique to the log-polar transformation of both the reference image and the input scene that makes the pattern recognition invariant to rotation and scale variations. Peak-to-side lobe ratio is measured and a threshold operation is employed to detect and track a target in an unknown input scene.
NASA Astrophysics Data System (ADS)
Zheng, Shijie; Zhu, Yinian
2015-11-01
In order to solve for the mode intensity distributions in a photonic crystal fiber (PCF) cross section and the propagation constant for the design of fiber bandpass filters, we numerically analyze the modal distributions of the fundamental core mode and different cladding modes. Based on the simulation results, we also experimentally demonstrate a simple fabrication of bandpass filters inscribed on the PCF by inserting a π-phase shift in a 12-period long-period grating (LPG). Two rejection bands with greater than 18 dB isolation and an ultra-wide band of 85.3 nm are achieved. The phase-shifted PCF-LPGs are fabricated using a CO2 laser with point-by-point focused pulses. The proposed fiber bandpass filter is compact and is not influenced by temperature effects.
NASA Astrophysics Data System (ADS)
Zeng, Zhuohuan; Fu, Yanjun; Li, Biao; Chai, Minggang
2016-08-01
Binary pattern defocused projection method can overcome the nonlinear gamma of the projector, as well as filter high harmonics and high-frequency noise. However, high-accuracy three-dimensional (3-D) shape measurement of complex surface using it still remains a challenge. Therefore, a novel Gray code plus phase-shifting method based on defocusing is proposed to solve the problem. The edges of Gray code patterns become blurred owing to defocus, which makes the recovery of accurate Gray code patterns difficult. To solve this problem, the positive and inverse Gray code patterns are projected to obtain threshold values, which are used to achieve the binarization of Gray code patterns. This method is robust and suitable for different defocus levels. Compared with the traditional Gray code plus phase-shifting method, the experimental results prove the effectiveness and feasibility of the proposed method.
Quantum Process Tomography of a Room Temperature Optically-Controlled Phase Shift
NASA Astrophysics Data System (ADS)
Kupchak, Connor; Rind, Samuel; Figueroa, Eden; Stony Brook University Team
2015-05-01
We have developed a room temperature setup capable of optically controlled phase shifts on a weak probe field. Our system is realized in a vapor of 87Rb atoms under the conditions of electromagnetically induced transparency utilizing a N-type energy level scheme coupled by three optical fields. By varying the power of the signal field, we can control the size of an optical phase shift experienced by weak coherent state pulses of < n > ~ 1 , propagating through the vapor. We quantify the optical phase shift by measuring the process output via balanced homodyne tomography which provides us with the complete quadrature and phase information of the output states. Furthermore, we measure the output for a set of states over a subspace of the coherent state basis and gain the information to completely reconstruct our phase shift procedure by coherent state quantum process tomography. The reconstruction yields a rank-4 process superoperator which grants the ability to predict how our phase shift process will behave on an arbitrary quantum optical state in the mode of the reconstruction. Our results demonstrate progress towards room temperature systems for possible quantum gates; a key component of a future quantum processor designed to operate at room temperature. US-Navy Office of Naval Research N00141410801, National Science Foundation PHY-1404398, Natural Sciences and Engineering Research Council of Canada.
Single-shot and phase-shifting digital holographic microscopy using a 2-D grating.
Yang, Taeseok Daniel; Kim, Hyung-Jin; Lee, Kyoung J; Kim, Beop-Min; Choi, Youngwoon
2016-05-01
We demonstrate digital holographic microscopy that, while being based on phase-shifting interferometry, is capable of single-shot measurements. A two-dimensional (2-D) diffraction grating placed in a Fourier plane of a standard in-line holographic phase microscope generates multiple copies of a sample image on a camera sensor. The identical image copies are spatially separated with different overall phase shifts according to the diffraction orders. The overall phase shifts are adjusted by controlling the lateral position of the grating. These phase shifts are then set to be multiples of π/2. Interferograms composed of four image copies combined with a parallel reference beam are acquired in a single shot. The interferograms are processed through a phase-shifting algorithm to produce a single complex image. By taking advantage of the higher sampling capacity of the in-line holography, we can increase the imaging information density by a factor of 3 without compromising the imaging acquisition speed. PMID:27137562
Gao, Fei; Zhang, Yu-Ru; Zhao, Shu-Xia; Wang, You-Nian
2014-08-15
The phase-shift effect has been investigated by a Langmuir probe and a fluid model in Ar capacitively coupled plasmas at 50 mTorr. In the discharge, two sources with the same frequency, i.e., 27.12 MHz, are applied on the top and bottom electrodes simultaneously, and the phase shift between them varies from 0 to π. It is found that the electron density has an off-axis peak near the radial edge when the phase difference is equal to 0 due to the electrostatic edge effect, and the best radial uniformity is observed at a phase difference equal to π. Furthermore, when the voltage increases, the best radial uniformity is obtained at lower phase shift values. Moreover, the electron energy probability function has a bi-temperature structure at all the selected phase differences at r = 1–15 cm. The evolution of the plasma characteristics with the phase difference implies that the best radial uniformity can be obtained, by balancing the electrostatic edge effect and the phase shift effect.
NASA Astrophysics Data System (ADS)
Wang, Zhigang; Fu, Yanjun; Yang, Jie; Xia, Guisuo; Wang, Jiasheng
2013-10-01
Blade is the key component of the aero-engine. In generally, it requires precise size and accurate shape, so the three-dimensional shape measurement of the blade is very important. Fringe projection profilometry is generally used to measure the 3D shape of an object, because of the advantages of non-contact operation, full-field acquisition, high resolution, and fast data processing. In this paper, 3D shape measurement method based on surface structured light that combination of gray-code and phase-shift projection is proposed. The wrapped phase of the blade is got by the four-step phase-shift method. In the projection process of the gray-code, due to the ambient light, different surface reflectance and surface physical discontinuous, the edge of gray-code becomes smooth, leading to decode error, so that the gray-code pattern must be binaried before decode. Through the accurate binarization of the blade gray-code pattern, the decoding cycle of the blade is achieved, and the unwrapped phase is achieved by phase unwrapping. Then the unwrapped phase difference between the blade and reference plane is got, the height of the blade can be obtained by the relationship between the phase difference and the height. The experimental and simulation results show that the proposed method can achieve a high precision, high speed and low cost 3D shape measurement of the blade. The measurement accuracy reaches 0.03 mm. The proposed method extends the reliability and practicality of the fringe projection profilometry.
Temperature effects in the modal phase shift of a weakly guiding fiber
NASA Technical Reports Server (NTRS)
Egalon, Claudio O.; Rogowski, Robert S.
1993-01-01
Temperature may be determined by monitoring the modal phase shift of an optical fiber. We present the results of a numerical model that has been developed to calculate the phase shift of a weakly guiding optical fiber due to thermal strain. Whenever an optical fiber is subjected to temperature changes, the optical path length, the index of refraction and the propagation constants of each fiber mode change. In consequence, the modal phase term, beta(ln)L, of the fields is also modified. A relationship for the modal phase shift is presented. This relation is applied to both single mode and two-mode fibers in order to determine the sensitivity characteristics of fibers that are subjected to temperature changes.
Observation of Atom Wave Phase Shifts Induced by Van Der Waals Atom-Surface Interactions
Perreault, John D.; Cronin, Alexander D.
2005-09-23
The development of nanotechnology and atom optics relies on understanding how atoms behave and interact with their environment. Isolated atoms can exhibit wavelike (coherent) behavior with a corresponding de Broglie wavelength and phase which can be affected by nearby surfaces. Here an atom interferometer is used to measure the phase shift of Na atom waves induced by the walls of a 50 nm wide cavity. To our knowledge this is the first direct measurement of the de Broglie wave phase shift caused by atom-surface interactions. The magnitude of the phase shift is in agreement with that predicted by Lifshitz theory for a nonretarded van der Waals interaction. This experiment also demonstrates that atom waves can retain their coherence even when atom-surface distances are as small as 10 nm.
Phase Shift of Polarized Light after Transmission through a Biaxial Anisotropic Thin Film
NASA Astrophysics Data System (ADS)
Hou, Yong-Qiang; Li, Xu; He, Kai; Qi, Hong-Ji; Yi, Kui; Shao, Jian-Da
2013-01-01
Based on the theoretical analysis of biaxial birefringent thin films with characteristic matrix method, we investigate the phase shift on transmission of a tilted columnar biaxial film at normal and oblique incidence over 300-1200 nm for s- and p-polarized waves. Compared with the simplified calculation method, the interference effects of the birefringent thin film are considered to yield more accurate results. The quarter wavelength phase shift calculated with the characteristic matrix method is consistent with that monitored with in situ measurement by two-angle ellipsometry, which validates our complied program for the calculation of the phase shift of the biaxial anisotropic thin film. Furthermore, the characteristic matrix method can be easily used to obtain continuous adjustable phase retardation at oblique incidence, whereas the simplified calculation method is valid for the case of normal incidence. A greater generality and superiority of the characteristic matrix method is presented.
Non-Relativistic Phase Shifts for Scattering on Generalized Radial Yukawa Potentials
NASA Astrophysics Data System (ADS)
O. J., Oluwadare; K. E., Thylwe; K. J., Oyewumi
2016-04-01
Non-relativistic phase shifts for a generalized Yukawa potential V(r) = ‑ V0(e‑αr/r) ‑ V1(e‑2αr/r2) are studied by the amplitude-phase method and by a frequently used analytic method based on a Pekeris-type approximation of power-law potential terms. Small variations of V1 seem to have marginal effects on the effective potential and on exact phase shifts. However, as pointed out in this study, a Pekeris-type approximation in scattering applications often implies serious distortions of both effective potentials and phase shifts. The Pekeris-type based analytic approximation in this study seems to give low-quality scattering results for this model potential at low energies.
Nakayama, Shinsuke; Shimono, Ken; Liu, Hong-Nian; Jiko, Hideyasu; Katayama, Noburu; Tomita, Tadao; Goto, Kazunori
2006-01-01
Gastrointestinal (GI) motility is well organized. GI muscles act as a functional syncytium to achieve physiological functions under the control of neurones and pacemaker cells, which generate basal spontaneous pacemaker electrical activity. To date, it is unclear how spontaneous electrical activities are coupled, especially within a micrometre range. Here, using a microelectrode array, we show a spatio-temporal analysis of GI spontaneous electrical activity. The muscle preparations were isolated from guinea-pig stomach, and fixed in a chamber with an array of 8 × 8 planar multielectrodes (with 300 μm in interpolar distance). The electrical activities (field potentials) were simultaneously recorded through a multichannel amplifier system after high-pass filtering at 0.1 Hz. Dihydropyridine Ca2+ channel antagonists are known to differentiate the electrical pacemaker activity of interstitial cells of Cajal (ICCs) by suppressing smooth muscle activity. In the presence of nifedipine, we observed spontaneous electrical activities that were well synchronized over the array area, but had a clear phase shift depending on the distance. The additional application of tetrodotoxin (TTX) had little effect on the properties of the electrical activity. Furthermore, by constructing field potential images, we visualized the synchronization of pacemaker electrical activities resolving phase shifts that were measurable over several hundred micrometres. The results imply a phase modulation mechanism other than neural activity, and we postulate that this mechanism enables smooth GI motility. In addition, some preparations clearly showed plasticity of the pacemaker phase shift. PMID:16990400
NASA Astrophysics Data System (ADS)
Bunsen, Masatoshi; Umetsu, Shuhei; Takabayashi, Masanori; Okamoto, Atsushi
2013-09-01
A technique for the phase and amplitude detection of object beams with multivalued phase and amplitude modulation is proposed for holographic storage systems. Generally, the spatial distribution of the complex amplitude of the object beam can be precisely detected by phase-shifting interferometric measurements in which the phase of the reference wave for interferometry is temporally or spatially changed in the datapage retrieval process. On the other hand, our technique allows fast, accurate, and feasible phase and amplitude demodulations by preliminary embedding phase shift into the phase signal of the datapage during recording. This technique will significantly improve the data transfer rate and vibration tolerance of the holographic storage system because the complex amplitudes of the object beam carrying datapages can be detected by single-shot image capturing. The optical system for datapage replay will also be simplified because there is no need to use any phase-shifting device during data retrieval. The single-shot detection of the phase-modulated datapage is experimentally demonstrated.
NASA Astrophysics Data System (ADS)
Zhang, Xuanni; Zhang, Hui; Wang, Yijun
2016-02-01
The optical Doppler Michelson imaging interferometer is widely used for wind measurements. Four interferograms obtained simultaneously are needed to immune to environmental disturbances. Thus, a static and divided mirror Michelson interferometer is proposed. Its highlight is the phase-shifting reflector array, which divides one mirror into four quadrants coated by different multilayer films with high reflectance, specified phase steps π/2 and little polarization effects. By combining analytical and empirical method, four coatings are designed with software TFCalc. The simulated results showed good agreement with the desired optical properties. Due to the limitation of the optical material and function of the software TFCalc, there are some design errors within tolerance.
NASA Astrophysics Data System (ADS)
Anchal, Abhishek; K, Pradeep Kumar; Landais, Pascal
2016-03-01
We propose and numerically verify a novel scheme of frequency-shift free optical phase conjugation by counter-propagating dual pump four-wave mixing in nonlinear fiber. The two counter-propagating pumps create a Bragg grating inside the fiber, which diffracts the forward propagating signal and generates a backward propagating idler wave whose phase is conjugate of signal phase. The two pump frequencies are placed symmetrically about signal frequency to ensure that idler wave will have same frequency as that of signal wave. Since the signal and idler waves appear at opposite ends, the idler is easily filtered out from the rest of the spectrum. Using nonlinear Schrödinger equation, we derive equations of signal and idler evolution. We obtain expressions for idler phase and show that perfect phase conjugation is achieved at an optimum length of fiber for a given pump power. We study the effect of fiber length and pump power on phase conjugation. Simulation results show the perfect phase conjugation at optimum fiber length under lossless conditions and small phase-offset when fiber loss and self and cross phase modulations are included. The small phase-offset is avoided by choosing fiber length smaller than optimum fiber length. Simulation results exhibit close agreement to theoretical values, which validates our simulations.
NASA Astrophysics Data System (ADS)
Dubey, Vishesh; Singh, Veena; Ahmad, Azeem; Singh, Gyanendra; Mehta, Dalip Singh
2016-03-01
We report white light phase shifting interferometry in conjunction with color fringe analysis for the detection of contaminants in water such as Escherichia coli (E.coli), Campylobacter coli and Bacillus cereus. The experimental setup is based on a common path interferometer using Mirau interferometric objective lens. White light interferograms are recorded using a 3-chip color CCD camera based on prism technology. The 3-chip color camera have lesser color cross talk and better spatial resolution in comparison to single chip CCD camera. A piezo-electric transducer (PZT) phase shifter is fixed with the Mirau objective and they are attached with a conventional microscope. Five phase shifted white light interferograms are recorded by the 3-chip color CCD camera and each phase shifted interferogram is decomposed into the red, green and blue constituent colors, thus making three sets of five phase shifted intererograms for three different colors from a single set of white light interferogram. This makes the system less time consuming and have lesser effect due to surrounding environment. Initially 3D phase maps of the bacteria are reconstructed for red, green and blue wavelengths from these interferograms using MATLAB, from these phase maps we determines the refractive index (RI) of the bacteria. Experimental results of 3D shape measurement and RI at multiple wavelengths will be presented. These results might find applications for detection of contaminants in water without using any chemical processing and fluorescent dyes.
Shifting the Bell Curve: The Benefits and Costs of Raising Student Achievement
ERIC Educational Resources Information Center
Yeh, Stuart S.
2009-01-01
Benefit-cost analysis was conducted to estimate the increase in earnings, increased tax revenues, value of less crime, and reductions in welfare costs attributable to nationwide implementation of rapid assessment, a promising intervention for raising student achievement in math and reading. Results suggest that social benefits would exceed total…
Achieving Gender Equity in Science Class: Shift from Competition to Cooperative Learning
ERIC Educational Resources Information Center
Esiobu, G. O.
2011-01-01
Purpose: This study aims to verify the impact of cooperative learning as an intervention strategy towards the achievement of peace, equality and equity in the science classroom as part of the democratic process necessary for sustainable development. Design/methodology/approach: The study sample comprised 56 SSS 2 students in one public…
ERIC Educational Resources Information Center
Tyler, Kathleen P.
2012-01-01
Interest in child development as a knowledge base for early childhood education programs flourished in the 1970s as a result of the theories and philosophies of Jean Piaget and other cognitive developmentalists. During subsequent decades in America, reform movements emphasizing accountability and achievement became a political and social…