共路外差干涉测量液晶空间光调制器相位特性

Measurement of the phase characteristics of liquid crystal spatial light modulator based on common-path heterodyne interferometry

为了对液晶空间光调制器进行高精度的校准,使其满足线性相位调制的应用需求,采用共路外差干涉法测量了液晶空间光调制器的相位调制特性,分析了实验系统的测量原理,取得了液晶空间光调制器相位调制量随输入灰度值变化的实验数据,并进行了线性校准。结果表明,实验中所用的液晶空间光调制器的最大相位调制量为2.55π,利用反插值法对20~240灰度范围内的相位调制曲线进行线性校正后的理论相位调制曲线非常接近理想线性曲线,相位调制曲线与理想线性调制曲线的相关系数可达0.9996;该测量方法可克服传统测量方法对图像处理的依赖性,具有较高的测量精度,相位调制量直接通过锁相放大器就可获得。该研究为基于液晶空间光调制器的高精度波前校正和精密测量提供了参考。

In order to calibrate the liquid crystal spatial light modulator(LCSLM)with high precision and meet the application requirements of linear phase modulation,a common-path heterodyne interferometer system was proposed to measure the phase modulation characteristics of LCSLM.The measurement principle was analyzed.Then the experimental data of the phase modulation varying with the input gray value of LCSLM was obtained and the linear calibration was carried out.The measurement results of the LCSLM show that the maximum phase modulation of the LCSLM used in the experiment is 2.55π.The phase modulation curve in the range of 20~240 is linearly corrected using the inverse interpolation method,and the corrected theoretical phase modulation curve is very close to the ideal linear curve.The correlation coefficient between the measured phase modulation curve and the ideal linear modulation curve can reach 0.9996.The proposed method can overcome the dependence of traditional measurement methods on image processing.The measurement precision of the proposed method is higher,and the phase modulation valves of LCSLM can be obtained directly through the lock-in amplifier.This research can provide a reference for high-precision wavefront correction and measurement based on LCSLM.