液晶可变相位延迟器相位延迟的精确定标

Accurate calibration of phase retardation based on the liquid crystal variable retarder

为了能够利用液晶可变相位延迟器(LCVR,liquid crystal variable retarder)对光波的相位延迟进行准确测量,提出一种基于Stokes参量测量光强法和最小二乘法的LCVR对光波相位延迟的精确定标方法。从理论分析光波经LCVR后影响相位延迟变化的因素,采用基于Stokes参量测量的光强法分别对波长为405、532、632和641nm入射光相位延迟随电压的变化进行测量,并实验验证归一化后的相位延迟变化只与驱动电压有关;基于最小二乘法对不同波长的初始相位延迟量进行定标研究,导出不同波长入射光经LCVR后初始相位延迟量定标方程,用671nm波长的激光对定标方程进行了验证,经定标方程求解的671nm波长的初始相位延迟量与实际值偏差为1.4nm,且任一驱动电压下,相位延迟量的实际测量值与公式定标计算值最大相对误差为0.18%。最后,通过与其他定标方法的比较,进一步说明采用本文方法定标的精确性和可靠性。

In order to use liquid crystal variable retarder （LCVR） to measure the phase retardation of light, the calibration method of phase retardation is studied. First, the factors that result in the change of phase retardation are analyzed in theory. Then,the retardance for 405 nm,532 nm,632 nm and 641 nm laser is measured by the light intensity method based on the Stokes parameters which changes with the driving voltage. Besides, the change of normalized phase retardation is only related to the driving voltage is verified by experiment. Next, the least square method is presented to measure the initial phase retarda- tion for different wavelengths,and the calibration equation of initial phase retardation is caleulated when different wavelengths of light incident to the LCVR. A 671 nm laser is used to demonstrate the equation and the results show that the stardard deviation is 1.4 nm between the initial phase retardation calculat- ed by the calibration equation and the real value,and the maximal relative error between them is 0.18% under any driving voltage. Finally, compared with other methods of calibrating initial phase retardation, the least square method is accurate and reliable.