We present a Stokes polarization camera prototype based on an electro-optic ceramic (PLZT) as the key
polarization component. Two pairs of electrodes are used to control the applied electric field and so the retardance and
orientation of the induced waveplate. The active area of the PLZT element is 120x120µm. To increase the effective
active area, a 2D array PLZT is used. Imaging through this 2D array with reduced fill factor is achieved by splitting the
focal plane. The focal plane is split by a microlenses array and interacts with each element of the ceramic array. A
modified focal plane is reconstructed by another microlenses array. Digital image processing is used to recover the prime
focal plane information. The technology used in this device (ceramic element, 2D array, imaging with split focal plane)
as well as characterization of the ceramic element and preliminary results will be presented.
We present a linear Stokes polarization camera working at visible wavelength. The camera is both compact and
robust for use in field experiments and outdoor conditions. It is based on fast polarization modulator. Four polarization
states images are acquired successively. Processing software allows live calculation, visualization and measurement of
polarization images deduced from the acquired images. The architecture of the hardware, calibration results and
sensitivity measurements is presented. Polarization image processing including polarization parameters computed are
proposed. These parameters include linear Stokes parameters (S0, S1 and S2), usual polarization parameters (intensity,
degree of linear polarization, and angle of polarization) and other polarization based parameters (polarized image,
depolarized image, virtual polarizer, polarization difference). Color data fusion and vector overlay algorithms are
presented. Finally experimental results and observations as well as possible applications are discussed.
Along with intensity and spectrum, the polarization of light carries abundant information. Polarization imaging has established strong interest for visual appearance measurement, based on its ability to analyze scattered light and for defense applications, thanks to its performances in term of object detection/identification. Image contrast enhancement and information on the objects (natural, man-made, detection of water bodies, 3D shape...) composing the scene can also be derived from the polarization analysis. In this paper, we will present an innovative polarization component based on ceramic PLZT and its integration in an imaging system. It will lead to a passive polarization camera that will measure the 4 Stokes parameters for each pixel of the image, in real-time, without any mechanical rotation and at high frame per second. Based on PLZT ceramic, we will present the design and the manufacturing of a rotatable and programmable waveplate. It will be the key component of a passive polarization imaging system. The component will be optimized, fabricated and integrated into a passive polarization camera. The performances of the polarization camera will be demonstrated in the laboratory. Measurement of Stokes vector for each pixel of the image will allow precise polarization measurement, leading to accurate analysis of the scattered light. Various parameters (gloss, color...) and images (polarization degree, surface scattering, volume scattering...) will be calculated from the Stokes parameters.
We present the modeling and the performance of a polarization
active imager at l5806 nm. The device operates in a monostatic
configuration, using a semiconductor laser to illuminate the target and a
telescope to create the image on a CCD matrix. Dual images (intensity
and polarization degree) of different scenes are obtained by a new
method (only two images acquired) and analyzed, showing the experimental
validation of this concept. An application of this active imager to
the detection of a target buried in the background (same reflectivity but
different polarization degree) is proposed. Field experiment results are
The purpose of active imaging system is to provide discrimination at long ranges independently from the surrounding illumination by using and controlling its own light source. Parameters such as the Doppler shift for coherent devices, the range, or the intensity of the light back scattered by objects have already been used to encode images. However, another parameter characterizing the electromagnetic field can help to discriminate the target: its polarization. In this paper we demonstrate that images resulting from the analysis of the polarization of light can offer better contrasts than classical images encoded by the intensity of light back-scattered. The emitting part of the imaging polarimeter built at CREOL (Polarization State Generator) is a doubled YAG pulsed laser with external polarization controllers. At the receiving part, the Polarization State Analyzer separates the incoming light so as to provide two crossed polarized images of the target.These images are acquired simultaneously by two high-resolution progressive scan digital cameras controlled by a computer. Afterwards, the computer processes the acquired data and displays two new images encoded by polarization parameters (depolarization ratio for example). In several examples and experiments, the influence of the geometry of the target (roughness, shape) on the incident state of polarization will be discussed.
We present the modeling and the performances of a Polarization Active Imager at (lambda) equals 806 nm. The device is operating in a monostatic configuration, using a semiconductor laser to illuminate the target and a telescope to create the image on a CCD matrix. Dual images (intensity and polarization degree) of different scenes are obtained by a new method (only 2 images acquisition) and analyzed, showing the experimental validation of this concept. The application of this active imager to the detection of target buried in the background (same reflectivity but different polarization degree) is proposed.
We present the concept of a Polarization Diversity Active Imager operating at (lambda) equals 810 nm. Each pixel of the image is encoded by the polarization degree Pd (0% < Pd < 100%) given by its Mueller Matrix. The measurement of the Mueller matrices is obtained using the Dual Rotation Retarder Technique. A theoretical analysis and an experimental validation of this technique are presented. The device is operating in a monostatic configuration, using a semiconductor laser ((lambda) equals 810 nm) to illuminate the target and a telescope to create the image on a CCD matrix. The experiment is controlled by a computer that drives the rotation of the retarders, the digitalization and the encoding of the image. The measured intensity and polarization images are compared and the information contained in the polarization degree are analyzed. Dual images (intensity-polarization) of different targets are presented, showing the experimental validation of the technique. The application of this active imager to the detection and the decamouflage of target buried in the background (same albedo but different polarization degree) is proposed.