Polarized Remote Sensing: A Note on the Stokes Parameters Measurements From Natural and Man-Made Targets Using a Spectrometer

Abstract

Polarized light has been studied over the past four decades as a useful signal to enhance the information from a variety of remote sensing applications. In the measurement process, the Stokes parameters are usually used to describe the state of polarization of light reflected from target surfaces. However, there is no research concerning the influence of extinction of the polarizer on the polarization properties derived from the Stokes parameters when we perform the polarimetric measurements of target surfaces using a spectrometer. In this paper, we measured the Stokes parameters of six natural surfaces (two soil samples, three vegetation covers, and a single leaf) and two man-made targets over a wide range of viewing directions at different incident zenith angles in the laboratory under two measurement conditions: considering and without considering the extinction of the polarizer. The comparison of these measured results indicated that the extinction of the polarizer, which was taken from the Spectralon panel, decreased the $I$ parameter and the bidirectional polarized reflectance factor of all the samples. Moreover, it is safe to use the $I$ parameter to represent the total reflected intensity of all our samples when we considered the extinction of the polarizer. Thus, the polarimetric measurements of target surfaces can not only give us the polarization information but also provide a reliable intensity signal.