Active polarimetric and multispectral laboratory demonstrator: contrast enhancement for target detection

Abstract

A compact laboratory demonstrator providing both active polarimetric and multispectral images is designed. Its buildings blocks include, at emission part, a multi-wavelength optical parametric oscillator and, at the reception part, a polarimetric hyperspectral imager. Some of the results obtained with this system are illustrated and discussed. In particular, we show that a multispectral polarimetric image brings additional information on the scene, especially when interpreted in conjunction with its counterpart intensity image, since these two images are complementary in most cases. Moreover, although hyperspectral imaging might be mandatory for recognition of small targets, we evidence that the number of channels can be limited to a set of few wavelengths as far as target detection is considered.

Design and experimental validation of a snapshot polarization contrast imager

“…In order to increase the range of remote sensing systems, pulsed light sources are classically used [14,30]. However, such sources are often affected by pulse-topulse intensity fluctuations.…”

“…In this section we will show how this system enables a good OSC estimation in real conditions. In particular, we will carry out experiments in situations where systems based on sequential acquisition [3,14,27] show weakness and imprecision. The system designed in this paper can also be operated in a sequential acquisition mode to show the benefit of simultaneous acquisition: one just has to consider the parallel image X in an acquisition and the orthogonal image Y in the subsequent acquisition.…”

“…Analysis along two orthogonal states of polarization is often achieved by switching a polarization sensitive device such as a rotating linear polarizer [10], a liquid crystal-based polarization rotator [4], a variable retarder [11,12], or a ferroelectric modulator [13,14]. However, this type of approach has two drawbacks.…”

Degree of polarization estimation in the presence of nonuniform illumination and additive Gaussian noise

“…In this paper, we consider that illumination is weakly coherent, so the speckle noise is not dominant and may be neglected. This assumption has been verified for the wideband light sources we will use, but also with the highpower laser sources used in [10], which do not lead to speckled images. We thus focus on two important issues relative to the estimation of DOP when the intensity images used to form the DOP image are perturbed by detector noise, which can be modeled as additive and Gaussian [9].…”

Target detection in active polarization images perturbed with additive noise and illumination nonuniformity

“…Imaging systems that measure the degree of polarization (DOP) of light backscattered by a scene have aroused great interest in several domains such as machine vision [1], biomedical imaging [2,3], and remote sensing [4,5]. These systems can, for example, reveal contrasts between regions of a scene which have the same intensity reflectivity but different polarimetric properties [6].…”