LCVR-based polarimetry: calibration issues

摘要

Changes in the structural organization of biological tissue can be indicative of disease. The ability to measure and associate changes in structural organization with disease-related cellular architecture has significant diagnostic value. Here we present a spectral imaging polarimeter to probe the local structural organization of tissue. The system is based on liquid crystal technology, and is comprised of two modules, a Stokes generator and a polarimeter. The Stokes generator uses a pair of Liquid Crystal Variable Retarders (LCVRs) to generate a set of Stokes vectors incident on a sample, while the polarimeter utilizes a separate pair of LCVRs to analyze the scattered Stokes vectors. Characterization of the system is in terms of a data reduction matrix that relates the polarimeter measurements to the incident Stokes vector. Calibration of the polarimeter (calculation of the elements of this data reduction matrix) is performed by presenting a series of known Stokes vectors to the device. The resulting over-determined system of equations is solved using the Singular Value Decomposition. We discuss the construction and calibration of the system.