Imaging techniques through discrete scattering media by polarized pulse waves

摘要

Imaging through random media is an important problem with many applications including optical remote sensing and bio-optics. As the optical depth gets larger, the imaging resolution and contrast deteriorates because of the effect of scattering. In this paper, we present the solution to the vector radiative transfer equation (VRTE) and its application to the optical imaging problem. Since the incoherent component created by the scattering in random media is responsible for the deterioration of the quality of images, several techniques are proposed to improve the imaging by reducing the incoherent component. The Off-Axis Intensity Subtraction (OAIS) and Cross-Polarization Intensity Subtraction (CPIS) imaging techniques are based on the fact that off-axis and cross polarization contains most of the incoherent component. Photon Density Waves (PDW) is a frequency-domain method which exhibits less effect of multiple scattering from the random media. We investigate the techniques mentioned above using numerical solution of VRTE and show the effectiveness, the limitations and the conditions of these techniques. Because we consider the polarized pulse wave case, we also discuss the time-domain behavior and the application of time-gating to the imaging problem. The time-gating method is investigated in both position and duration. Since in practice an array of detectors are often used, we also include the effect of Field Of View of a detector (pixel FOV) in our calculations. We quantitatively measure the performance of imaging techniques by contrast. Also, we apply these techniques to numerical simulations of cross images and show the improvement of the quality of the images.