Development Of A Stokes Polarimeter Based On Liquid Crystal Variable Retarder

There are many methods for polarization measurement,such as mechanical modulation,wavefront segmentation.However,we cannot use these methods on high-precision systems or some instruments with special requirements for incident light intensity.In order to solve the problems above,we developed a Stokes polarimeter based on liquid crystal variable retarder,which has the characteristics of no mechanical rotation,fast response and simple calibration.This thesis first elaborates the current research status of Stokes polarimeter and its advantages,as well as disadvantages.We further proposed the necessity of constructing a Stokes polarimeter based on liquid crystal variable retarder,and finally completed the development and testing of this polarimeter.The main research contents and innovations of this thesis are as follows:(1)We constructed a theoretical model of a liquid crystal variable retarder.Through the theoretical derivation,we obtained the theoretical formulas of the retardance and the fast axis azimuth of a liquid crystal variable retarder,which are related to the driving voltage,the wavelength,the incident angle and the azimuth angle.Through performance characterization,we have compared the experimental results with the simulation results.The consistency of the two results illustrated the correctness and rationality of the theoretical derivation.(2)We have developed a Stokes polarimeter based on a liquid crystal variable retarder.The development process includes the working principle of the polarimeter,components selection as well as the development of the control system.At the same time,in order to reduce the condition number and improve the stability of the system,we have also systematically modeled and optimized the polarization system.According to the optimization results,we completed the construction and calibration of the polarimeter.(3)We evaluated the measurement error of this Stokes polarimeter by testing the air,a waveplate and a polarizer respectively.Furthermore,we evaluated the repeatability of this polarization measurement system by repeating the measurement of the same waveplate.The final standard deviation is less than 0.2%,indicating that the system repeatability is acceptable.We have completed the property research of a liquid crystal variable retarder by theoretical modeling and experimental verification.On this basis,we developed a Stokes polarimeter based on liquid crystal variable retarders.The polarimeter utilizes liquid crystal modulation to perform polarization measurements,which helps to increase the speed and accuracy of polarization measurements.