空间调制型全偏振成像系统的角度误差优化

Alignment error optimization of spatially modulated imaging polarimeter system

空间调制型全偏振成像系统利用Savart偏光镜能够将被探测目标的4个Stokes参数S0~S3调制在同一幅干涉图像中,从而通过单次采集便可获得完整的偏振信息。在该系统中,半波片和检偏器的角度误差对Stokes参数的测量精度有着不可忽略的影响。文中首先给出了包含上述两种角度误差的干涉强度调制方程,根据实际系统参数,在角度误差模型的基础上分析了当入射光为自然光、0°/90°线偏振光、45°/135°线偏振光和左/右旋圆偏振光时,角度误差对空间调制型全偏振成像系统的Stokes参数测量精度的影响。利用这四种基态偏振光的偏振测量误差,给出了任意偏振态和偏振度的入射光偏振测量误差的表征方法 ,最后,文中以系统测量矩阵条件数为优化目标函数,经仿真计算得出当Savart板厚度为23 mm时系统测量矩阵条件取得最小值为2.06,半波片和检偏器耦合角度误差对系统偏振测量精度的影响程度最小。

Spatially modulated imaging polarimeter（SMIP） system is able to modulate four Stokes parameters S0-S3 in a single interferogram by using Savart plate. Through sliding reconstruction method,the entire polarization information can be demodulated from the interference fringes. In this system, the alignment errors of the half wave plate（HWP） and the analyzer has a non-ignorable impact on the measurement accuracy of the Stokes parameters. A theoretical model including these two alignment errors were presented in this paper. Based on this model and parameters of the prototype SMIP, the Stokes parameters measurement accuracy of unpolarized light, 0° /90° linear polarized light, 45° /135° linear polarized light and left/right circularly polarized light was analyzed. According to these four basic polarized lights, a method for solving Stokes parameters measurement error of incident light with any state of polarization（SOP） and degree of polarization（DOP） was given. In order to alleviate the influence of HWP and analyzer alignment errors, an optimization using condition number of measurement matrix as an objective function was given. It is shown that when the thickness of Savart plate is 23 mm,which is corresponding to the minimum condition 2.06, measurement errors induced by HWP and analyzer alignment errors can be effectively diminished.