基于旋转波片的斯托克斯参量检测与精度分析

Stokes Parameter Detection and Precision Analysis Based on Rotating Quarter-Wave Plate

用于偏振光学遥感器定标的参考光源,其偏振态的检测精度会直接影响偏振光学遥感器的定标精度,进而影响目标特性的反演水平。选用870 nm波段的水平线偏振光作为被测试的定标参考光源,通过旋转1/4波片(quarter-wave plate,QWP)对其光强进行调制。调制光强可表达为波片快轴旋转角度的傅里叶级数,采用傅里叶变换法反演出级数的系数,根据该系数即可计算出被测试光源的Stokes参量。给出10次测量各参量及偏振度的平均值、标准偏差、合成不确定度以及测量平均值与理论值的相对偏差。为提高测试精度,通过对波片快轴初始定位角度偏差Δα、延迟量偏差Δδ与检偏器透光轴角度偏差Δβ进行分析,提出了偏差修正模型。该模型通过Stokes参量检测偏差随Δδ和Δβ的变化趋势及实际偏差值,确定Δδ和Δβ的大小。结合模拟出的波片快轴初始定位角度偏差Δα,对实验装置加以调整,再次对光源的偏振态进行检测。结果表明,基于该修正模型测得光源的各Stokes参量与理论值最大偏差从未经修正的3.77%降低至1.41%。证实了基于本实验的原理、装置、测量方法及所提出的偏差修正模型可有效提高定标参考光源偏振态检测的精度。

The accuracy of the calibration reference source polarization states directly influences the precision of the polarized optical remote sensor calibration,and thus affects the inversion accuracy of the characteristics of targets.In this paper,870 nm horizontal linear polarized light has been chosen as the tested calibration reference light,modulated by rotating quarter-wave plate（QWP）.The intensity as a Fourier series of the rotation angle of the plate and its coefficients were demodulated with the Fourier transform method,Stokes parameters can be calculated with these coefficients.The mean,standard deviation,composite uncertainty and relative deviation of measured data compared with the theoretical value of the ten measurement results were presented.In order to improve the accuracy of the measurement,the correction model for the quarter-wave plate retardance deviationΔδ fast axis angle deviation Δα and the transmission axis alignment deviation Δβ of analyzing polarizer has been constructed.In this model,detection deviation of Stokes parameters is described as a function of Δδ and Δβ,Δδ and Δβ were determined by the function and magnitude of the deviation.Combined with quarter-wave plate fast axis angle deviation which was the result of simulation to adjust the experiment device,and then detecting the calibration reference source polarization states again.The experimental results show that,the difference between measured value and theoretical value of Stokes parameters reduced to less than1.41%from 3.77%relative to without correction.The experiment principle,device and deviation correction model of this research can significantly improve the accuracy of detecting the polarization state of the calibration reference light source.