Spectral imaging polarimeter based on liquid crystal technology

Abstract

The ability to detect changes in the structural organization of tissue has significant diagnostic value. A polarimeter has the ability to detect these changes as it can probe the tissue sub-wavelength structural organization through polarization effects. Here we present a spectral imaging polarimeter that is based on liquid crystal technology. The system is comprised of two modules, a Stokes generator and a polarimeter. Each module employs a pair of Liquid Crystal Variable Retarders (LCVRs), which are computer-controlled birefringent devices. Additionally, the polarimeter utilizes a CCD camera to image the illuminated region, thus providing spatially resolved estimates of the complete Mueller matrix for the sample. Before the system can be employed, an overall system characterization involving all four LCVRs must be performed. This characterization defines a relationship between polarimeter measurements and the incident Stokes vectors. Here we briefly describe the calibration procedure and show example Mueller matrix images of biological tissue.