High-speed portable polarimeter using a ferroelectric liquid crystal modulator

Abstract

The implementation of an imaging polarimeter able to capture dynamicscenes is presented. Our prototype is designed to work at visiblewavelengths and to operate at high-speed, ie above 200 Hz, contraryto commercial or laboratory liquid crystal polarimeters previouslyreported in the literature. It has been used in the laboratory withcontrolled illumination conditions (wavelength, coherence or incoherence,incidence, ...) as well as in a natural environment with sunlightor any lamp or light source. The device consists of commercial componentswhose cost is moderate. The polarizing element is based on a ferroelectricliquid crystal modulator which acts as a half-wave plate at its designwavelength. The device has been fully characterized and verifiedto work up to 1 kHz. It produces a 90° polarization rotation. Inthis Orthogonal State Configuration Imagery (OSCI), images in degreeof polarization (DOP) can be obtained with simple post-processingof two consecutive images. With a commercial CCD camera, operationup to 360 Hz is demonstrated, resulting in images whose quality isequivalent to that of classical low speed polarimeters.