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This PDF file contains the front matter associated with SPIE
Proceedings Volume 7461, including the Title Page, Copyright
information, Table of Contents, Introduction (if any), and the
Conference Committee listing.
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A requirement for the Visible/Infrared Imager Radiometer Suite (VIIRS) is that its polarization sensitivity be 3% or less
for all VISNIR bands (412-865 nm). A test using a rotating polarizer sheet was performed on the sensor to validate this
requirement, and though the test results show that the requirement is met, they also show a large variation in this
polarization sensitivity (as much as 2%) across the field of view (FOV) in track. Though this result is unexpected, it may
be the result of natural variations in the diattenuation and retardance of the VIIRS optics as a function of field angle. To
test this theory, a raytracing model of the system was constructed using measured ellipsometric data from the VIIRS
optics, and the polarization sensitivity of the model was computed. Using the nominal ellipsometric data, good
correlation between the predicted and measured polarization sensitivity was not achieved. However, by applying small
variations to the ellipsometric data as a function of position on the optics, it was possible to achieve good correlation.
This paper gives the details of the sensor polarization sensitivity measurements, ellipsometric measurements, and
raytracing analysis.
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Marshall Space Flight Center's (MSFC) is developing a Vacuum Ultraviolet (VUV) Fabry-Pérot Interferometer that will be launched on a sounding rocket for high throughput, high-cadence, extended field of view CIV (155nm) measurements. These measurements will provide (i) Dopplergrams for studies of waves, oscillations, explosive events, and mass motions through the transition region, and, (ii), polarization measurements to study the magnetic field in the transition region. This paper will describe the scientific goals of the instrument, a brief description of the optics and the polarization characteristics of the VUV Fabry Pérot.
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Low polarization sensitivity is critical for a number of Earth science applications, including the measurement
of ocean color and ozone from satellite sensors. Polarization control places serious constraints on the optical
design of these sensors, particularly for the wide field of view imaging spectrometers contemplated for future
Decadal Survey applications. The PolZero Time Domain Polarization Scrambler (TDPS) is an optical
component that provides significant polarization sensitivity reduction for spectrometric instruments without
producing beam replication, image distortion or requiring a specialized optical path. The PolZero is
implemented using a pair of photo-elastic modulators to induce a particular high frequency polarization
structure onto the transmitted beam. Averaging this modulated beam over many temporal polarization cycles,
that is, over a few milliseconds, produces results approximating transmission through an ideal depolarizer.
Measurements have shown reduction in the transmitted degree of polarization by factors of over 30. Mueller
matrices of the TDPS, measured using a Mueller matrix imaging polarimeter, are presented as a function of
wavelength in the region 450-700 nm.
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The Ocean Radiometer for Carbon Assessment (ORCA) is a new design concept for the next generation ocean
biology and biogeochemistry satellite sensor. The wavelength range will be from the near UV, through the visible
and to the Short Wave infrared. The challenge in this design is to remove the polarization effects from the optical
performance of this hyper spectral observing instrument. In order to remove any polarization sensitivity during
observation, the design calls for a front-end depolarizer that consists of two wedged birefringent magnesium
fluoride crystals. Here we discuss the polarimetry measurements performed on this polarization scrambler, the
depolarizer design and compare these results with model calculations.
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A method for aerosol refractive index estimation with ground based polarization measurement data is proposed. The
proposed method uses a dependency of refractive index on p and s polarized down welling solar diffuse irradiance. It is
much easy to measure p and s polarized irradiance on the ground with a portable measuring instrument rather than solar
direct, diffuse and aureole measurements. Through theoretical and simulation studies, it is found that the proposed
method show a good estimation accuracy of refractive index using measured down welling p and s polarized irradiance
data with a measuring instrument pointing to the direction which is perpendicular to the sun in the principal plane. Field
experimental results also show a validity of the proposed method in comparison to the estimated results from the
conventional method with solar direct, diffuse and aureole measurement data.
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An all-sky imaging polarimeter was deployed in summer 2008 to the Mauna Loa Observatory in Hawaii to study
atmospheric skylight polarization. This paper describes the Mauna Loa deployment and presents an initial comparison of
our data to those observed by Coulson with a zenith-slice polarimeter in the late 1970s and early 1980s. We show how
the all-sky imaging technique yields additional insight to the nature of skylight polarization beyond what is observed in a
single zenith scan.
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A method for reflectance based vicarious calibration with aerosol refractive index and size distribution estimation using
atmospheric polarization irradiance data is proposed. It is possible to estimate aerosol refractive index and size
distribution with atmospheric polarization irradiance measured with the different observation angles (scattering angles).
The Top of the Atmosphere (TOA) or at-sensor radiance is estimated based on atmospheric codes with estimated
refractive index and size distribution then vicarious calibration coefficient can be calculated by comparing to the
acquired visible to near infrared instrument data onboard satellites. The estimated TOA radiance based on the proposed
method is compared to that with aureole-meter based approach which is based on refractive index and size distribution
estimated with solar direct, diffuse and aureole (Conventional AERONET approach). It is obvious that aureole-meter is
not portable, heavy and large while polarization irradiance measurement instruments are light and small (portable size
and weight).
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It is shown that once the diffusely scattered polarization properties are calibrated, the texture orientation can
be calculated directly from diattenuation and retardance. Polarization scattering properties are studied for a
rough aluminum surface with one-dimensional rough texture and well-defined orientation. Functions of Mueller
matrix elements related to sample orientation about the normal via the arctangent function are investigated.
The Mueller matrix bidirectional reflectance distribution function is measured for a linearly sanded aluminum
sample. Sinusoidal fits to the Mueller matrix show that the angular orientation of the data can be recovered
explicitly from its properties.
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We report the results of a multi-day diurnal study in which radiometrically calibrated polarimetric and conventional
thermal imagery is recorded in the LWIR to identify/compare the respective time periods in which minimum target
contrast is achieved, e.g., thermal inversion periods are typically experienced during dusk and dawn. Imagery is recorded
with a polarimetric IR sensor employing a 324x256 microbolometer array using a spinning achromatic retarder to
perform the polarimetric filtering. The images used in this study include the S0, normalized S1, and normalized S2 Stokes
images and the degree of linear polarization (DOLP) images of a scene containing military vehicles and the natural
background. In addition, relevant meteorological parameters measured during the test period include air temperature,
ambient loading in the LWIR, relative humidity, and cloud cover, height and density. The data shows that the chief
factors affecting polarimetric contrast are the amount of thermal emission from the objects in the scene and the
abundance of LWIR sources in the optical background. In addition, we found that contrast between targets and
background within polarimetric images often remains relatively high during periods of low thermal contrast.
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Measurements of visible-NIR skylight polarization are compared with radiative transfer calculations from a model that
employs polarized single scattering. The measurements are from a full-sky imaging polarimeter under conditions ranging
from very low aerosol content to thick forest fire smoke. Generally, the lack of multiple scattering in the model leads to
overestimated degree of polarization in all but very clear conditions at the longest wavelengths (> 600 nm).
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While color signals are well known as a form of animal communication, a number of animals communicate using
signals based on patterns of polarized light reflected from specialized body parts or structures. Mantis shrimps, a group
of marine crustaceans, have evolved a great diversity of such signals, several of which are based on photonic structures.
These include resonant scattering devices, structures based on layered dichroic molecules, and structures that use
birefringent layers to produce circular polarization. Such biological polarizers operate in different spectral regions
ranging from the near-UV to medium wavelengths of visible light. In addition to the structures that are specialized for
signal production, the eyes of many species of mantis shrimp are adapted to detect linearly polarized light in the
ultraviolet and in the green, using specialized sets of photoreceptors with oriented, dichroic visual pigments. Finally, a
few mantis shrimp species produce biophotonic retarders within their photoreceptors that permit the detection of
circularly polarized light and are thus the only animals known to sense this form of polarization. Mantis shrimps use
polarized light in species-specific signals related to mating and territorial defense, and their means of manipulating
light's polarization can inspire designs for artificial polarizers and achromatic retarders.
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A custom imaging Mueller matrix retinal polarimeter (the GDx-MM) is built. Mueller matrix images of normal human
fovea were acquired with the GDx-MM over a 9° field at 780nm and have been analyzed for depolarization index and
the variation of degree of polarization with incident polarization state. The degree of polarization (DoP) was often above
50% and varied in complex ways as a function of the incident polarization states. The depolarization properties around
the macula loosely correlated with the retardance image. High spatial frequency depolarizing structures were evident
throughout the fovea.
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The SALSA linear Stokes polarization camera from Bossa Nova Technologies (520-550 nm) uses an electronically
rotated polarization filter to measure four states of polarization nearly simultaneously. Some initial imagery results are
presented. Preliminary analysis results indicate that the intensity and degree of linear polarization (DOLP) information
can be used for image classification purposes. The DOLP images also show that the camera has a good ability to
distinguish asphalt patches of different ages. These positive results and the relative simplicity of the camera system
show the camera's potential for field applications.
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We present a high-speed ferroelectric liquid crystal based imaging polarimeter. It can evaluate the first three
Stokes parameters. Contrary to previous high-speed systems, it only uses a single liquid crystal cell, driven in
an optimized way in order to produce a tunable rotation of polarization. Its characterization is presented, as
well as its integration in a portable implementation working at 633 nm. Preliminary results are provided.
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For the past several years we have been working on strategies to mitigate the effects of IFOV errors on
LWIR microgrid polarimeters. In this paper we present a detailed, theoretical analysis of the source of
IFOV error in the frequency domain, and show a frequency domain strategy to mitigate those effects.
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We present the first high spatial resolution, passively-illuminated polarimetric images of boosting rocket exhaust
plumes. The images shown here show significant linear and circular polarization, and the ability to resolve
the polarization signals into images allows us to make some preliminary arguments as to their origins. Our
observations are consistent with polarization caused by Rayleigh and Mie scattering (linear) and interaction
with plume plasma-generated magnetic fields (circular). We also present nearly simultaneous, two-color, narrowband
(633 ± 5 and 750 ± 5 nm) exhaust plume images, where significant structural differences are observed in
the plumes despite a relative small difference in the two wavelengths.
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Microgrid polarimeters are a type of division of focal plane (DoFP) imaging polarimeter that contains a mosaic
of pixel-wise micropolarizing elements superimposed upon an FPA sensor. Such a device measures a slightly
different polarized state at each pixel. These measurements are combined to estimate the Stokes vector at each
pixel in the image. DoFP devices have the advantage that they can obtain Stokes vector image estimates for
an entire scene from a single frame capture. However, they suffer from the disadvantage that the neighboring
measurements that are used to estimate the Stokes vector images are acquired at differing instantaneous fields of
view (IFOV). This IFOV issue leads to false polarization signatures that significantly degrade the Stokes vector
images. Interpolation and other image processing strategies can be employed to reduce IFOV artifacts; however
these techniques have a limit to the amount of enhancement they can provide on a single microgrid image.
Here we investigate algorithms that use multiple microgrid images that contain frame-to-frame global motion
to further enhance the Stokes vector image estimates. Motion-based imagery provides additional redundancy
that can be exploited to recover information that is "missing" from a single microgrid frame capture. We have
found that IFOV and aliasing artifacts can be defeated entirely when these types of algorithms are applied to the
data prior to Stokes vector estimation. We demonstrate results on real LWIR microgrid data using a particular
resolution enhancement technique from the literature.
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We have designed a new near-IR imaging polarimeter which generates the complete Stokes' vector estimation
simultaneously. The design is based on our first generation division of amplitude polarimeter where four images are
folded on to a single focal plane detector. This gives rise to a small compact rigid instrument. The design operation
wavelength is 632.8 nanometers. The new second generation design operates at a wavelength of 1550 nanometers and
has three improvements over the first generation: 1) the design of the Beam-Splitter Assembly (BSA) is based on an
optimization scheme where the Measurement (instrument) matrix is optimized for Stokes' vector estimation with noisy
data, 2) the four individual focusing lenses positioned after the BSA have been replaced by a single lens in front of the
BSA reducing differential image distortion, and 3) a reticle is placed at an intermediate image plane, providing a fiducial
mark in each of the images for precise registration.
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Mueller matrix polarimeter using the axisymmetrical polarized and analyzed optics is proposed. The axisymmetrical
optics has a potential to bring out the polarization properties of a sample which kept in beam spot. A key device of this
method is a detector named "a ring beam detector". The concept of the detector is a topology and/or a projective
transformation and the optical configuration of the detector consists of a conical mirror and/or a conical lens, a
cylindrical screen and a CCD camera. To use a Fourier transform method, we can get Mueller matrix properties from the
intensity distribution of the ring beam captured by the camera without a mechnically and electrically polarization
modulation. In this paper, principles of axisymmetrical Mueller matrix polarimeter, the ring beam detector and basically
experimental results are shown.
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The polarization behavior of the Leica Geosystems absolute distance meter is investigated in order to understand
measurement noise and dropouts sometimes observed when the instrument is used with fold mirrors. A Stokes-
Mueller calculus analysis suggests retardance in the fold elements is a likely culprit. We establish the heuristic
that for folds in a single plane, successful operation is obtained when the sum of the ellipsometric angle ▵ for
each element in single pass is an integer multiple of 180°. The heuristic is validated experimentally, and found
to have a tolerance in the range of ±12° to hold distance standard deviations to 10μm. Strategies to achieve this
condition include keeping angles of incidence near 90°, tuning with angle of incidence, and judicious selection of
mirror coatings.
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This report proposes an optical rotation measurement using Stokes parameters with a dual rotating retarder and analyzer.
The intensity captured by a spectrometer is modulated by a retarder and an analyzer in a rotating ratio of one to three.
The Stokes parameters and retardance along the wavelength of the retarder are simultaneously analyzed by Fourier
transform. Two standard quartz plates of 0.8 mm and 1.6 mm thickness are measured for a sample. The characteristics of
optical rotation dispersion of the two standard quartz plates correspond with theoretical values at wavelengths from 550
nm to 900 nm. We succeeded to separate the optical rotation from the birefringence.
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We describe the design, construction, calibration and testing of a confocal scanning Mueller polarimeter. A polarization
state generator and polarization state analyzer have been inserted into the optical path of a conventional confocal
scanning imager to collect the reflectance Muller matrix of samples measuring up to 6.26 mm on a side. Four sources
are available for sample interrogation using diode lasers centered at 532 nm, 635 nm, 670 nm, and 785 nm. The device
captures all required imagery to calculate the Mueller matrix of each image pixel in approximately 90 s. These matrices
are then reduced into polarization imagery such as the diattenuation, retardance and depolarization index. Oftentimes
this polarization imagery is quite different and potentially more informative than a conventional intensity image. There
are a number of fields that can benefit from alternative/enhanced imagery, most notably in the biomedical,
discrimination, and target recognition communities. The sensor has been designed for biomedical applications aimed at
improving the technique of noninvasive detection of melanoma lesions.
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All polarization characteristics can be described by Mueller matrix. These polarized parameters are captured by changing
the states of polarization given by combination of polarization generator and polarization analyzer. We employ double
liquid crystal phase modulators whose orientation is set 45 degrees by changing the rubbing direction of orientation film.
A unit of LC phase modulators is set in temperature-controlled environment and calibrated spectroscopic Stokes
polarimeter. A measurement method for obtaining Mueller matrix is to applied that the phase of LC phase modulators
are changed with the phase modulation in the proportion of one part to five. We succeed to measure spectroscopic
Mueller matrix without any mechanical movement with high accuracy.
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PEPPER is a high-speed differential Polarization-Encoded Photometer and Polarimeter developed in the Center
for Astronomical Adaptive Optics at the University of Arizona, Tucson, by Dr. Dan Potter and Matthew Graham.
PEPPER is capable of acting as a high-speed polarimeter by using electro-optical switching to chop between
standard star and target star, and between in and out-feature bandpass filter at frequencies fast enough to
suppress atmospheric variations. PEPPER is capable of either high-speed polarimetry or differential photometry
using a combination of simultaneous imaging and electro-optical switching. In the differential photometry mode,
PEPPER utilizes the electro-optical switching to calibrate instrumental and atmospheric photometric variation.
This technique coupled with a zero-read noise photon counting detector achieves photon noise limited results
demonstrated to an accuracy of less than 1 part in 105. Herein we present the design concept behind the
photometer and the polarimeter mode of PEPPER, as well as, results from observations in the differential
photometer mode at the Steward 90 inch telescope, at the Kitt Peak National Observatory, Tucson, Arizona.
Results from the analysis of near IR polarimetry observations of young stars with circumstellar disks taken at
the Gemini North Telescope with the Hokupa'a adaptive optics system are also presented.
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A three-by-three polarization ray tracing matrix P which is defined in global coordinates characterizes the
polarization transformations associated with single ray through optical system. The P matrix contains both a
geometrical transformation effect and the polarization characteristics of diattenuation and retardance from the
optical and polarization elements. In order to separate the geometrical transformation and calculate the "physical"
retardance, a non-polarizing ray tracing matrix Q is used. The diattenuation and the retardance of a dove prism are
analyzed as an example.
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For sensing systems that characterize the spectro-polarimetric radiance reaching the camera, the origin of the
sensed phenomenology is a complex mixture of sources. While some of these sources do not contribute to
the polarimetric signature, many do such as the downwelled sky polarization, the target and background p-
BRDF(polarimetric bi-directional reflectance distribution function), the upwelled sky polarization, and the camera
Mueller matrix transfer function. In this paper we investigate candidate in-scene calibration materials
potentially allowing for portions of the p-BRDF to be derived for material surfaces throughout the scene. Extraction
of target p-BRDF from the sensed spectro-polarimetric energy may result in improved target detection
performance in the future. Results using both synthetic and real data are presented.
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When using a MMP for a detection or identification task, a user considers certain elements of
the Mueller matrix. The usual way of performing this task is to measure the full Mueller matrix
and discard the unused elements. For polarimeter designs with speed, miniaturization, or other
constraints it may be desirable to have a system with reduced dimensionality that measures
only the important elements of the Mueller matrix as efficiently as possible. In this paper,
we develop a framework that allows partial MMPs to be analyzed. Quantitative metrics are
developed by considering geometrical relationships between the space spanned by a particular
MMP and the space occupied by the scene components. The method is generalized to allow
the effects of noise to come into the equation when noise performance is important as well.
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Quantifying aerosols on a global scale is extremely important due to their strong but anomalous impact on the global
climate. Traditionally, the aerosols retrievals use only the intensity measurements of the scattered light. However, these
measurements are less sensitive to aerosol type and also suffer contamination from ground surfaces. It is with these
limitations in mind that we plan to improve the quality and scope of aerosol retrieval by making use of soon to be
available polarimetric sensors such as the Aerosol Polarimetry Sensor (APS) on the GLORY satellite and combine them
with other available datasets such as lidar data from the CALIPSO satellite for vertical profiling, and high-spatialcoverage
intensity measurements from MODIS. To handle these extremely large sensor data sets, we will explore the
capabilities of various statistical methods and even combine them to create inversion algorithms that will work best. Up
to now, we worked with the simplest case, the single-scattering approximation and built a retrieval algorithm using
multi-angular, multi-wavelength simulated measurements of intensity and polarization. The inversion techniques we
used are the optimal estimator and the neural networks.
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Previous visible-band laboratory measurements have shown that polarization data can be used to determine optical
properties of materials such as the index of refraction with controlled illumination sources. For outdoor measurements,
the complex illumination formed by the polarized sky for visible wavelengths makes this process considerably more
difficult. This paper reports polarization measurements for horizontal painted-metal and PVC plates and the background
atmosphere from a quickly changeable dual-field imaging polarimeter which provides polarization of ground-based
objects nearly concurrently with full-sky polarization. A microfacet model has been developed which accounts for the
polarized sky illumination and solar-reflecting and flat-reflecting microfacets. Data from this model have been used to
explain the primary features of the polarization observed when viewing painted metal and PVC plates outdoors with
clear skies. Future work will attempt to use this model with polarimeter data to retrieve the index of refraction of the
observed plates.
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The photoelastic modulator (PEM) is a polarization modulator that operates at the resonant frequency of its optical
element. The PEM is made of isotropic optical materials, in contrast to birefringent materials used in electro-optic
modulators. These two characteristics, operation at resonance and the use of isotropic optical materials, give the PEM
unique optical features, such as high modulation purity and efficiency, broad spectral range, high power handling
capability, large acceptance angle, large useful aperture and high retardation stability. These features make the PEM an
effective polarization modulator in a variety of applications. Sometimes it is the only choice for high sensitivity
applications. In an effort to characterize the PEMs more thoroughly, we are carrying out a series of tests on the basic
properties of the PEM. Residual birefringence is an important property that affects the quality of a PEM. In the second
paper in a series, we focus on the measurement of residual birefringence in the optical element of a PEM and
maintaining the residual birefringence at a low level in the final PEM product.
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Changes in the state of polarization of a beam of radiation occurring without depolarization can be described by means
of a pure Mueller matrix. Pure Mueller matrix can be expressed in terms of the elements of a 2x2 Jones matrix. This
results in that the pure Mueller matrix has a simple and elegant structure, which is embodied by interrelations between
matrix elements. All possible interrelations for the elements of a general pure Mueller matrix are derived by Hovenier
(Appl. Opt., Vol.33, No.36, pp. 8318-8324, 1994). The structure of the pure Mueller matrix enables to solve the inverse
problem basing not on all sixteen matrix elements but only on certain part of them. We show that four elements which
are formed each of columns and rows of the pure Mueller matrix considering them individually are dependent and the
inverse problem can be solved in general case basing only on the rest of twelve matrix elements.
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The design and construction of wide FOV imaging polarimeters for use
in atmospheric remote sensing requires significant attention to the
prevention of artificial polarization induced by the optical elements.
Surface, coatings, and angles of incidence throughout the system must
be carefully designed in order to minimize these artifacts because the
remaining instrumental bias polarization is the main factor which
drives the final polarimetric accuracy of the system. In this work, we
present a detailed evaluation and analysis to explore the possibility
of retrieving the initial polarization state of the light traveling
through a generic system that has inherent instrumental polarization.
Our case is a wide FOV lens and a splitter device. In particular, we
chose as splitter device a Philips-type prism, because it is able to
divide the signal in 3 independent channels that could be
simultaneously analyze to retrieve the three first elements of the
Stoke vector (in atmospheric applications the elliptical polarization
can be neglected [1]). The Philips-type configuration is a versatile,
compact and robust prism device that is typically used in three color
camera systems. It has been used in some commercial polarimetric
cameras which do not claim high accuracy polarization measurements
[2]. With this work, we address the accuracy of our polarization
inversion and measurements made with the Philips-type beam divider.
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We report test results of a study to assess the applicability for using passive polarimetric imaging in the
long-wave infrared (LWIR) to detect regions of recently altered road-type surfaces, e.g., soil, gravel,
asphalt, etc. The field test was conducted at the U.S. Army Research Laboratory, Adelphi, MD, on a test
surface best described as a well traveled dirt road consisting of a gravel clay-soil mixture that was well
compacted. During this initial proof-of-concept test, a LWIR polarimetric camera system was positioned
at a slant-path of 10 degrees with respect to the line-of-site (LOS) and the natural lay of the surface,
approximately 15 meters from the target test-bed. Stokes images, S0, S1, and S2, were recorded using the
LWIR polarimeter that utilizes a spinning achromatic retarder design mated to Mercury Cadmium
Telluride (MCT) focal plane array (FPA). Various surrogate targets were buried near the surface and great
care was taken to camouflage the area to eliminate any "visible" signs of disturbance. Thermal gradients
resulting from the unearthing of cool soil were allowed to dissipate. Two metrics were used to evaluate
performance, i.e., conventional receiver operating characteristic (ROC) curve analysis and an effective
contrast ratio between the target and background. Results showed particularly good detectability in the S2
imagery, with less in S1, and no detectability in S0, i.e., the conventional LWIR thermal image.
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