The Experts below are selected from a list of 24312 Experts worldwide ranked by ideXlab platform
Russell A Chipman - One of the best experts on this subject based on the ideXlab platform.
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Advances in modeling polarimeter performance
Polarization Science and Remote Sensing VIII, 2017Co-Authors: Russell A ChipmanAbstract:Artifacts in Polarimeters are apparent polarization features which are not real but result from the systematic errors in the polarimeter. The polarization artifacts are different between division of focal plane, spectral, and time modulation Polarimeters. Artifacts result from many sources such as source properties, micropolarizer arrays, coatings issues, vibrations, and stress birefringence. A modeling examples of polarization artifacts due to a micro-polarizer array polarimeter is presented.
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spectral density response functions for modulated Polarimeters
Applied Optics, 2015Co-Authors: Charles F Lacasse, Oscar G Rodriguezherrera, Russell A ChipmanAbstract:Conventional imaging devices are often compared using their optical transfer functions (OTFs) in space and their impulse responses in time. Modulated Polarimeters cannot be directly compared this way, since they are frequency multiplexed. Here we define a spectral density response function that describes how the spectral density matrix of the Stokes parameters for an object transfers through a modulated polarimeter. This response function facilitates the objective comparison of Polarimeters in a way that is analogous to the OTF for conventional imaging systems. The spectral density response is used to calculate a Wiener filter for a rotating analyzer polarimeter as an example of filter optimization for modulated polarimetry.
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role of the null space of the drm in the performance of modulated Polarimeters
Optics Letters, 2012Co-Authors: Charles F Lacasse, Russell A ChipmanAbstract:Imaging Polarimeters infer the spatial distribution of the polarization state of the optical field as a function of time and/or wavelength. A polarimeter indirectly determines the polarization state by first modulating the intensity of the light field and then demodulating the measured data to infer the polarization parameters. This Letter considers passive Stokes parameter Polarimeters and their inversion methods. The most widely used method is the data reduction matrix (DRM), which builds up a matrix equation that can be inverted to find the polarization state from a set of intensity measurements. An alternate strategy uses linear system formulations that allow band limited reconstruction through a filtering perspective. Here we compare these two strategies for overdetermined Polarimeters and find that design of the null space of the inversion operator provides degrees of freedom to optimize the trade off between accuracy and signal-to-noise ratio. We further describe adaptive filtering techniques that could optimize the reconstruction for a particular experimental configuration. This Letter considers time-varying Stokes parameters, but the methods apply equally to Polarimeters that are modulated in space or in wavelength.
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band limited data reconstruction in modulated Polarimeters
Optics Express, 2011Co-Authors: Charles F Lacasse, Russell A ChipmanAbstract:Data processing for sequential in time Polarimeters based on the Data Reduction Matrix technique yield polarization artifacts in the presence of time varying signals. To overcome these artifacts, Polarimeters are designed to operate at higher and higher speeds. In this paper we describe a band limited reconstruction algorithm that allows the measurement and processing of temporally varying Stokes parameters without artifacts. An example polarimeter consisting of a rotating retarder and polarizer is considered, and conventional processing methods are compared to a band limited reconstruction algorithm for the example polarimeter. We demonstrate that a significant reduction in error is possible using these methods.
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optimization of mueller matrix Polarimeters in the presence of error sources
Optics Express, 2008Co-Authors: K Twietmeyer, Russell A ChipmanAbstract:Methods are presented for optimizing the design of Mueller matrix Polarimeters and and in particular selecting the retardances and orientation angles of polarization components to ensure accurate reconstruction of a sample’s Mueller matrix in the presence of error sources. Metrics related to the condition number and to the singular value decomposition are used to guide the design process for Mueller matrix Polarimeters with the goal of specifying polarization elements, comparing polarimeter configurations, estimating polarimeter errors, and compensating for known error sources. The use of these metrics is illustrated with analyses of two example Polarimeters: a dual rotating retarder polarimeter, and a dual variable retarder polarimeter.
Doron Goldberg - One of the best experts on this subject based on the ideXlab platform.
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Self-referenced, microdegree, optical rotation polarimeter — a detailed analysis
2016 Progress in Electromagnetic Research Symposium (PIERS), 2016Co-Authors: Zeev Weissman, Doron GoldbergAbstract:Summary form only given. Optical rotation (OR) polarimetry is one of the most suitable optical methods to track glucose concentration in vivo, as well as to track the concentration of chiral molecules in high pressure liquid chromatography (HPLC) systems, widely used for analytical chemistry, mainly in the pharmaceutical industry. We have been developing a novel OR polarimeter that has high sensitivity (in the microdegree range), and can be miniaturized (down to a size of a matchbox), and therefore is exceptionally suitable for these sensing applications. The purpose of this presentation is to provide a detailed analysis of the new polarimeter. Attention is given to the attainable resolution and the susceptibility to various noise mechanisms. One such mechanism is a phenomenon known as pseudo-rotation, typical to HPLC OR Polarimeters, which results in a large spurious rotation signal indistinguishable from true OR. The analysis is validated by respective experimental results. The potential for miniaturization of the polarimeter is also considered. This polarimeter has a relatively simple configuration (see Figure 1), that, as mentioned, facilitates miniaturization. It is based on two novel optical mechanisms, which ensure high sensitivity: the first provides a continuous optical reference, and the second provides an internal optical gain for the OR signal. The reference signal compensates for background noises, which in some cases can be more than an order of magnitude larger than the OR signal itself. The current experimental angular resolution is ~ 20 micro-degrees, and the analysis shows a potential for reduction by more than an order of magnitude.
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Self-referenced, microdegree, optical rotation polarimeter for biomedical applications: an analysis
Journal of Biomedical Optics, 2015Co-Authors: Zeev Weissman, Doron GoldbergAbstract:We comprehensively analyze the performance of a type of optical rotation (OR) polarimeter, which has been designed from the outset to fit the special requirements of two major applications: general chiral detection during the separation of optical isomers by high-pressure liquid chromatography systems in the pharmaceutical industry, and monitoring of glucose in the interstitial fluid of diabetics by a fully implanted long-term optical sensor. Both very demanding applications call for an OR polarimeter that can be miniaturized while maintaining high resolution and accuracy in the microdegree range in the face of considerable noise from various sources. These two characteristics—miniature size and immunity to noise—set this polarimeter apart from the traditional OR Polarimeters currently in use, which are both bulky and very susceptible to noise. The following detailed analysis demonstrates the advantages of this polarimeter and its potential as an analytic and diagnostic tool.
Charles F Lacasse - One of the best experts on this subject based on the ideXlab platform.
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spectral density response functions for modulated Polarimeters
Applied Optics, 2015Co-Authors: Charles F Lacasse, Oscar G Rodriguezherrera, Russell A ChipmanAbstract:Conventional imaging devices are often compared using their optical transfer functions (OTFs) in space and their impulse responses in time. Modulated Polarimeters cannot be directly compared this way, since they are frequency multiplexed. Here we define a spectral density response function that describes how the spectral density matrix of the Stokes parameters for an object transfers through a modulated polarimeter. This response function facilitates the objective comparison of Polarimeters in a way that is analogous to the OTF for conventional imaging systems. The spectral density response is used to calculate a Wiener filter for a rotating analyzer polarimeter as an example of filter optimization for modulated polarimetry.
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role of the null space of the drm in the performance of modulated Polarimeters
Optics Letters, 2012Co-Authors: Charles F Lacasse, Russell A ChipmanAbstract:Imaging Polarimeters infer the spatial distribution of the polarization state of the optical field as a function of time and/or wavelength. A polarimeter indirectly determines the polarization state by first modulating the intensity of the light field and then demodulating the measured data to infer the polarization parameters. This Letter considers passive Stokes parameter Polarimeters and their inversion methods. The most widely used method is the data reduction matrix (DRM), which builds up a matrix equation that can be inverted to find the polarization state from a set of intensity measurements. An alternate strategy uses linear system formulations that allow band limited reconstruction through a filtering perspective. Here we compare these two strategies for overdetermined Polarimeters and find that design of the null space of the inversion operator provides degrees of freedom to optimize the trade off between accuracy and signal-to-noise ratio. We further describe adaptive filtering techniques that could optimize the reconstruction for a particular experimental configuration. This Letter considers time-varying Stokes parameters, but the methods apply equally to Polarimeters that are modulated in space or in wavelength.
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frequency domain scene based non uniformity correction and application to microgrid Polarimeters
Proceedings of SPIE, 2011Co-Authors: Wiley T Black, Charles F LacasseAbstract:ABSTRACT Non-uniformity noise is common in infrared imagers, and is usually corrected through calibration, often bymomentarily blocking the optical system with a relatively uniform temperature plate. The non-uniformitypatterns also tend to drift and require periodic recalibration, necessitating occasional loss of video from the imagerduring the recalibration process. Microgrid Polarimeters are especially sensitive to xed-pattern noise becausethe polarization signal is acquired by dierentiation of neighboring pixels. Scene-based algorithms attempt toalleviate the need for recalibration of the imager through image processing techniques. We introduce a newfrequency-domain scene-based non-uniformity estimation and correction technique, and apply the technique toinfrared and microgrid polarimeter imagery. The technique demonstrates promising results for shutter-assisted(recalibration) video, for microgrid polarization systems as well as most spatially modulated sensor systems.Keywords: Long-wave infrared, Polarimetry, Microgrid, Scene-BasedNon-Uniformity Correction, Fixed-PatternNoise
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band limited data reconstruction in modulated Polarimeters
Optics Express, 2011Co-Authors: Charles F Lacasse, Russell A ChipmanAbstract:Data processing for sequential in time Polarimeters based on the Data Reduction Matrix technique yield polarization artifacts in the presence of time varying signals. To overcome these artifacts, Polarimeters are designed to operate at higher and higher speeds. In this paper we describe a band limited reconstruction algorithm that allows the measurement and processing of temporally varying Stokes parameters without artifacts. An example polarimeter consisting of a rotating retarder and polarizer is considered, and conventional processing methods are compared to a band limited reconstruction algorithm for the example polarimeter. We demonstrate that a significant reduction in error is possible using these methods.
Zeev Weissman - One of the best experts on this subject based on the ideXlab platform.
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Self-referenced, microdegree, optical rotation polarimeter — a detailed analysis
2016 Progress in Electromagnetic Research Symposium (PIERS), 2016Co-Authors: Zeev Weissman, Doron GoldbergAbstract:Summary form only given. Optical rotation (OR) polarimetry is one of the most suitable optical methods to track glucose concentration in vivo, as well as to track the concentration of chiral molecules in high pressure liquid chromatography (HPLC) systems, widely used for analytical chemistry, mainly in the pharmaceutical industry. We have been developing a novel OR polarimeter that has high sensitivity (in the microdegree range), and can be miniaturized (down to a size of a matchbox), and therefore is exceptionally suitable for these sensing applications. The purpose of this presentation is to provide a detailed analysis of the new polarimeter. Attention is given to the attainable resolution and the susceptibility to various noise mechanisms. One such mechanism is a phenomenon known as pseudo-rotation, typical to HPLC OR Polarimeters, which results in a large spurious rotation signal indistinguishable from true OR. The analysis is validated by respective experimental results. The potential for miniaturization of the polarimeter is also considered. This polarimeter has a relatively simple configuration (see Figure 1), that, as mentioned, facilitates miniaturization. It is based on two novel optical mechanisms, which ensure high sensitivity: the first provides a continuous optical reference, and the second provides an internal optical gain for the OR signal. The reference signal compensates for background noises, which in some cases can be more than an order of magnitude larger than the OR signal itself. The current experimental angular resolution is ~ 20 micro-degrees, and the analysis shows a potential for reduction by more than an order of magnitude.
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Self-referenced, microdegree, optical rotation polarimeter for biomedical applications: an analysis
Journal of Biomedical Optics, 2015Co-Authors: Zeev Weissman, Doron GoldbergAbstract:We comprehensively analyze the performance of a type of optical rotation (OR) polarimeter, which has been designed from the outset to fit the special requirements of two major applications: general chiral detection during the separation of optical isomers by high-pressure liquid chromatography systems in the pharmaceutical industry, and monitoring of glucose in the interstitial fluid of diabetics by a fully implanted long-term optical sensor. Both very demanding applications call for an OR polarimeter that can be miniaturized while maintaining high resolution and accuracy in the microdegree range in the face of considerable noise from various sources. These two characteristics—miniature size and immunity to noise—set this polarimeter apart from the traditional OR Polarimeters currently in use, which are both bulky and very susceptible to noise. The following detailed analysis demonstrates the advantages of this polarimeter and its potential as an analytic and diagnostic tool.
J. Pendharkar - One of the best experts on this subject based on the ideXlab platform.
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Compton polarimeter as a focal plane detector for hard X-ray telescope: sensitivity estimation with Geant4 simulations
Experimental Astronomy, 2013Co-Authors: T. Chattopadhyay, S. V. Vadawale, J. PendharkarAbstract:X-ray polarimetry can be an important tool for investigating various physical processes as well as their geometries at the celestial X-ray sources. However, X-ray polarimetry has not progressed much compared to the spectroscopy, timing and imaging mainly due to the extremely photon-hungry nature of X-ray polarimetry leading to severely limited sensitivity of X-ray Polarimeters. The great improvement in sensitivity in spectroscopy and imaging was possible due to focusing X-ray optics which is effective only at the soft X-ray energy range. Similar improvement in sensitivity of polarisation measurement at soft X-ray range is expected in near future with the advent of GEM based photoelectric Polarimeters. However, at energies >10 keV, even spectroscopic and imaging sensitivities of X-ray detector are limited due to lack of focusing optics. Thus hard X-ray polarimetry so far has been largely unexplored area. On the other hand, typically the polarisation degree is expected to increase at higher energies as the radiation from non-thermal processes is dominant fraction. So polarisation measurement in hard X-ray can yield significant insights into such processes. With the recent availability of hard X-ray optics (e.g. with upcoming NuSTAR, Astro-H missions) which can focus X-rays from 5 KeV to 80 KeV, sensitivity of X-ray detectors in hard X-ray range is expected to improve significantly. In this context we explore feasibility of a focal plane hard X-ray polarimeter based on Compton scattering having a thin plastic scatterer surrounded by cylindrical array scintillator detectors. We have carried out detailed Geant4 simulation to estimate the modulation factor for 100 % polarized beam as well as polarimetric efficiency of this configuration. We have also validated these results with a semi-analytical approach. Here we present the initial results of polarisation sensitivities of such focal plane Compton polarimeter coupled with the reflection efficiency of present era hard X-ray optics.
