含数字微镜器件的离轴光学系统偏振像差分析及补偿

Polarization Aberration Analysis and Compensation of Off-Axis Optical System with Digital Micro-Mirror Device

偏振像差会影响离轴光学成像系统的偏振测量精度和偏振成像效果,有必要对其进行标定和补偿。基于三维偏振光线追迹,分析了含有数字微镜器件(DMD)的编码超分辨离轴光学成像系统在不同视场下的偏振像差,并提出一种在光路中接近DMD位置加入线性衰减器(LD)和相位延迟器(LR)进行偏振补偿的方法。经计算发现,DMD表面引入的最大二向衰减为1.43×10^(-3),最大相位延迟为9.52×10^(-3)rad,整体光学系统引入的最大二向衰减为2.32×10^(-3),最大相位延迟为1.55×10^(-2)rad,DMD引入的偏振像差占全系统的60%以上。对比了偏振补偿前后整体光学系统的偏振像差分布、琼斯瞳和偏振成像仿真效果,结果表明:布置合适的弱偏振器件进行补偿后,二向衰减和相位延迟均减小为补偿前的一半左右,琼斯矩阵接近单位阵,偏振成像中的串扰现象也明显减少。可见,DMD会引入较大的偏振像差,而在DMD附近的光路中使用LD和LR能够简单有效地进行偏振补偿。

Polarization aberration will affect the accuracy of polarization measurement and the polarization imaging effect of an off-axis optical imaging system,and thus it is necessary to calibrate and compensate for it.On the basis of threedimensional polarization ray tracing,this study analyzes the polarization aberration of the coded super-resolution off-axis optical imaging system with a digital micro-mirror device(DMD)in different fields of view and proposes a method of polarization compensation by adding a linear attenuator(LD)and a linear retarder(LR)in the optical path near DMD.The calculations indicate that the maximum diattenuation and the maximum phase retardance introduced by the DMD surface are 1.43×10^(−3) and 9.52×10^(−3) rad,respectively,while the maximum diattenuation and the maximum phase retardance introduced by the overall optical system are 2.32×10^(−3) and 1.55×10^(−2) rad,respectively.Hence,the polarization aberration introduced by DMD accounts for more than 60%of that introduced by the whole system.Then,this paper compares the polarization aberration distributions,Jones pupils,and polarization imaging simulations of the overall optical system before and after polarization compensation.The results reveal that after an appropriate weak polarizer is used for compensation,the diattenuation and phase retardance are reduced by about a half,with the Jones matrix close to the unit matrix and the crosstalk phenomenon in polarization imaging alleviated significantly.It can be concluded that DMD introduces severe polarization aberration,but the utilization of the LD and LR in the optical path near DMD can simply and effectively compensate for the polarization.