液晶光学相位阵列的电压-相位曲线标定方法

Algorithm of Voltage-Phase Shift Characteristic Calibration for Liquid Crystal Optical Phased Array

液晶光学相位阵列(Liquid Crystal Optical Phased Array,LCOPA)作为一类空间光调制器,正广泛应用于光学信息处理等领域。对加载在LCOPA单元上的控制电压与相位延迟关系的标定,是影响其工作性能的关键因素。提出了一种基于光强测量的标定方法。首先推导了出射光束相位分布和远场光强之间的关系。标定时,将相位控制图设计成国际象棋棋盘格的图样,在两区域施加不同的电压,记录出射光束在远场中心的强度。经过滤波和归一化处理,得到电压-光强曲线。提出了标定的测量方程和权值矩阵,然后利用加权的最小二乘方法对电压-相位关系进行标定。最后用该方法对BNS公司生产的一款LCOPA进行标定。

Liquid crystal optical phased array（ LCOPA）,as a kind of spatial light modulator（ SLM）,is now widely used in the field of optical information processing. The voltage- phase shift calibration of LCOPA in a phase shift unit is an important step which will seriously affect the performance of a LCOPA. A new calibration algorithm based on the measurement of light intensity is proposed in this paper. The relationship between the phase distribution of emerge light and light intensity in the far- field is derived. The checkerboard pattern is used in the calibration routine. The different control voltages are applied in two regions to measure the light intensity at the center of the far- field. The voltage- intensity curve is obtained by filtering the raw data and normalizing them. The measurement equation and the weight matrix are introduced and the weighted least square method is used to calibrate the phase- voltage characteristics. Finally,the calibrational results of a LCOPA from BNS are shown.