High-speed portable polarimeter using a ferroelectric liquid crystal modulator

The implementation of an imaging polarimeter able to capture dynamic scenes is presented. Our prototype is designed to work at visible wavelengths and to operate at high-speed, ie above 200 Hz, contrary to commercial or laboratory liquid crystal polarimeters previously reported in the literature. It has been used in the laboratory with controlled illumination conditions (wavelength, coherence or incoherence, incidence,...) as well as in a natural environment with sunlight or any lamp or light source. The device consists of commercial components whose cost is moderate. The polarizing element is based on a ferroelectric liquid crystal modulator which acts as a half-wave plate at its design wavelength. The device has been fully characterized and verified to work up to 1 kHz. It produces a 90 degrees polarization rotation. In this Orthogonal State Configuration Imagery (OSCI), images in degree of polarization (DOP) can be obtained with simple post-processing of two consecutive images. With a commercial CCD camera, operation up to 360 Hz is demonstrated, resulting in images whose quality is equivalent to that of classical low speed polarimeters.