Polarization based optical sectioning of multilayer cell patterns

Abstract

In this paper we present a polarization based technique for optical sectioning and imaging of multi-layer cell patterns separated by a weakly diffused media. Multi-layer cell pattern is important to study because this type of structure is often used for heterogeneous three dimensional cell culture and bio-chips applications, where information at different depths would be crucial. Functioning of this type of bi-layer or multilayer cell patterns can easily be monitored using polarization based imaging techniques. For polarization based imaging, samples are excited by white light source with different set of band-pass filter and linear polarizer, and images are collected through corresponding long-pass filters and analyzer by CCD camera. Preliminary experiments are carried out using absorption inhomogeneity separated by a weakly diffused thin polymer layers. Polarized images at various angles are collected at a set of excitation wavelength. Such measurements can identify 3x3 sub-matrix elements out of the full 4x4 sixteen elements of Mueller matrix. In order to enhance the image contrast, the 3x3 Mueller components are further decomposed into diattenuation and depolarization power images. Superficial layer image information is found to be more prominent in the depolarization power images, and diattenuation images provide sub layer information. By comparing the decomposition images at various wavelengths, we can observe sub-layer structures at different depths.