Optical properties of polymer-dispersed liquid crystal films as basic elements of imitation measures for calibration of photoplethysmographic devices
Denis G. Lapitan, Andrey P. Tarasov, Lev S. Kapustin, Dmitry A. Rogatkin;
Moscow Regional Research and Clinical Institute (“MONIKI”), Moscow, Russia
Abstract
The modern advancement of optical noninvasive diagnostic methods in medicine requires the development of working measures (phantoms) that mimic the properties of real biological tissues and reproduce units of measured quantities. We have recently developed a working measure that simulates pulsating blood flow in the skin for calibration of photoplethysmographic devices. The basis of the measure is a polymer-dispersed liquid crystal (PDLC) film, which acts as an electro-optical modulator. However, the optical properties of PDLC films depend on many factors (concentration of liquid crystals in the polymer matrix, presence of impurities in it, etc.) and, therefore, can vary from film to film. The aim of this work was to measure the optical properties of two samples of PDLC films to select the most suitable option for use in imitation measures. We assembled an experimental setup and carried out measurements in the transmission geometry. Lasers at wavelengths of 365 nm, 513 nm and 635 nm were used as light sources. Based on the measurements, the electro-optical curves (transmittance versus applied voltage) were calculated. Using the two-stream Kubelka–Munk model, the electro-optical curves were further converted into the scattering coefficient of the films. At a wavelength of 513 nm, the scattering coefficient of the first film varies in the range of 5...55 cm-1, and the scattering of the second film is in the range of 20...40 cm-1 when the applied voltage changes from 0 to 60 V. Thus, both films are suitable for use in the developed working imitation measures.
Speaker
Denis Lapitan
Moscow Regional Research and Clinical Institute (“MONIKI”)
Russia
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