Liquid crystal-based spectral imaging goniometric polarimeter for sample characterization

Abstract

The ability to measure polarization effects is important in many biological and industrial applications. Additionally, measuring spectral and scatter effects can offer greater sensitivity for applications where characterization and differentiation are important. Here we present a liquid crystal-based spectral imaging goniometric polarimeter to probe these effects. The system consists of two modules, a Stokes generator and a polarimeter, each constructed from a pair of liquid crystal variable retarders (LCVR). LCVRs are computer-controlled birefringent devices that impart retardance effects with no mechanical movement. Additionally, the Stokes generator utilizes a computer-controlled liquid crystal tunable filter (LCTF) to transmit a specific wavelength bandwidth, also with no mechanical movement. The polarimeter, enclosed in a cage system, manually rotates around the sample plane to provide angular scatter measurements. A CCD camera images the sample and provides spatially resolved estimates of the complete Mueller matrix as a function of wavelength and scatter angle. Here we describe the system and its calibration, and show quantitative measurement results for a number of samples.