A comparison of the point spread functions for polarization-difference and intensity-only imaging in scattering media

A possible reason for the observed improvement in the detectability of polarizing targets in polarization-difference (PD) images obtained in scattering media is examined. The point spread function (PSF) of an imaging system indicates how a particular system degrades the image of a point source. Through a convolution with a particular intensity distribution, the effects of scatterers on the image as a whole can also be determined. When imaging in a dense scattering medium, multiple scattering effects causes a widening of the PSF beyond that of the optical imaging system alone (without scatterers). Since multiple scattering also tends to depolarize radiation, it has been hypothesized that polarization-difference imaging (PDI) has a narrower PSF than polarization-sum (PS) imaging because PDI is insensitive to unpolarized radiation. A narrower PSF would allow for less blurring in images and, therefore, better resolution of targets in a scattering medium. Through the use of a Monte-Carlo simulation, the PSFs for an elemental electric dipole source imaged by PS and PD imaging through a slab of scattering medium are explored.