Wavelength, temperature, and voltage dependent calibration of a nematic liquid crystal multispectral polarization...

Rapid calibration of liquid crystal variable retarder (LCVR) devices is critical for successful clinical implementation of a LC-based Mueller matrix imaging system being developed for noninvasisve skin cancer detection. For multispectral implementation of such a system, the effect of wavelength (lambda), temperature (T), and voltage (V) on the retardance (delta) required to generate each desired polarization state needs to be clearly understood. Calibration involves quantifying this interdependence such that for a given set of system input variables (lambda,T), the appropriate voltage is applied across a LC cell to generate a particular retardance. This paper presents findings that elucidate the dependence of voltage, for a set retardance, on the aforementioned variables for a nematic LC cell: approximately 253 mV/100 nm lambda-dependence and approximately 10 mV/ degrees CT-dependence. Additionally, an empirically derived model is presented that enables initial voltage calibration of retardance for any desired input wavelength within the calibration range of 460-905 nm.