An Automatic Control System for Measuring Stokes Polarization and Utilizing UV Light Source

Polarization is an elementary property of light waves and has many applications in medicine and health sciences. In this research, an automatic control UV light source Stokes polarimeter system is built using simple and inexpensive optical devices. The optical system includes one UV laser source, three polarizers, two quarter-waveplate, and one optical sensor applying the Mueller-Stokes decomposition for extracting linear birefringence (LB), linear dichroism (LD), circular birefringence (CB), circular dichroism (CD), linear depolarization (L-Dep), and circular depolarization (C-Dep) of a biological sample. The system can measure the intensity of 180 data points then calculate the output Stokes vector of measured samples from 4 inputs polarized lights (i.e., 0°, 45°, 90° of linear polarized lights and right-hand circular). The experimental results showed that the system could automatically measure Stokes parameters of a biological sample with the accuracy at ±5% to compare with the commercial device, Stokes polarimeter. Therefore, the designed system has the benefits not only of extracting the optical parameters of the biological samples but also of improving the accuracy of results by reducing the error effect on the measurement.