Enhancement of the point-spread function for imaging in scattering media by use of polarization-difference imaging

Abstract

Polarization-difference (PD) imaging techniques have been demonstrated to improve the detectability of target features that are embedded in scattering media. The improved detectability occurs for both passive imaging in moderately scattering media (Ͻ5 optical depths) and active imaging in more highly scattering media. These improvements are relative to what is possible with equivalent polarization-blind, polarization-sum (PS) imaging under the same conditions. In this investigation, the point-spread functions (PSF's) for passive PS and PD imaging in single-scattering media are studied analytically, and Monte Carlo simulations are used to study the PSF's in single-and moderately multiple-scattering media. The results indicate that the PD PSF can be significantly narrower than the corresponding PS PSF, implying that better images of target features with high-spatial-frequency information can be obtained by using differential polarimetry in scattering media. Although the analysis was performed for passive imaging at moderate optical depths, the results lend insight into experiments that have been performed in more highly scattering media with active imaging methods to help mitigate the effects of multiple scattering.

Transillumination of highly scattering media by polarized light

“…The quasi-straightforward propagating photons pass the shortest path and are the least depolarized. This feature underlies polarization-difference imaging of objects hidden inside turbid media (see, e.g., [13][14][15][16]19,[23][24][25]). In this technique the imagebearing component of light is extracted by subtracting the detected cross-polarized signal from the co-polarized one.…”

“…In many experiments, detection of the polarization difference is employed (see, e.g., [13][14][15][16]19,[21][22][23][24][25]). This method is based on subtracting of the intensity of the cross-polarized component from the intensity of radiation with the initial polarization.…”

“…In the polarization-difference techniques (see, e.g., [13][14][15][16]19,[23][24][25]) the 'imagebearing' component of light is extracted by subtracting the detected cross-polarized signal from the co-polarized one. As diffusive photons with completely randomized polarization make the same contribution to both polarized components of scattered radiation, subtraction of cross-polarized component from the co-polarized one filters out the diffusive photons from the ballistic and snake photons.…”

“…Previous theoretical works devoted to this problem dealt with numerical simulations (see, e.g., [16,[18][19][20][21]23]). Contrary to these works, we present a simple analytical theory that makes possible semi-quantitative describing the image characteristics and gives an insight into their dependence on optical parameters of the medium.…”

Resolution enhancement in active underwater polarization imaging with modulation transfer function analysis

“…Tyo simulated light transmitting procedures with single scatter theory and the Monte Carlo method [19]. The results showed that the point spread function (PSF) of the water was dependent on the polarization in the passive and active imaging, and the polarization-difference (PD) algorithm had a narrower PSF than polarization-sum (PS) algorithm.…”