Ju Xueping, Yang Bin, Yan Changxiang, Zhang Junqiang, Xing Wenhe
Appl Opt. 2018 Oct 10;57(29):8600-8613. doi: 10.1364/AO.57.008600.
Calibration of the channeled spectropolarimeter is significant for the quantitative application of this instrument. In current calibration methods for a channeled spectropolarimeter, an absolute angle between the coordinate system of an auxiliary polarizer and the global coordinate system of the instrument is usually indispensable. The effectiveness of calibration depends on the precision of the absolute angle, while it is usually difficult to achieve in a practical calibration process. This paper presents an easily implemented method to simultaneously calibrate the alignment and retardation errors of high-order retarders for a channeled spectropolarimeter. In the presented method, the requirement of an absolute angle between the coordinate system of an auxiliary polarizer and the global coordinate system of the instrument is replaced by only rotating a relative angle in the coordinate system of the auxiliary polarizer itself. First, we theoretically derive the modified reconstruction model considering the alignment errors of high-order retarders. By analyzing and summarizing the modified reconstruction model, the calibration and compensation models of the alignment and retardation errors are further proposed. Then, two linearly polarized beams with a relative angle of 45° between them are utilized to determine the alignment and retardation errors. Based on these results, the alignment and retardation errors can be compensated by a software correction algorithm without any precise mechanical adjustments. The effectiveness and feasibility of the presented method are verified by numerical simulations and experiments. The advantage of easy implementation makes this calibration method more suitable to apply in the laboratory and to be on track for correcting the channeled spectropolarimeter.
通道式光谱偏振仪的校准对于该仪器的定量应用具有重要意义。在当前通道式光谱偏振仪的校准方法中，辅助偏振器的坐标系与仪器全局坐标系之间的绝对角度通常是不可或缺的。校准的有效性取决于绝对角度的精度，而在实际校准过程中通常难以实现。本文提出了一种易于实现的方法，用于同时校准通道式光谱偏振仪高阶延迟器的对准误差和延迟误差。在所提出的方法中，辅助偏振器坐标系与仪器全局坐标系之间的绝对角度要求被仅在辅助偏振器自身坐标系中旋转相对角度所取代。首先，我们从理论上推导了考虑高阶延迟器对准误差的修正重建模型。通过对修正重建模型的分析和总结，进一步提出了对准误差和延迟误差的校准与补偿模型。然后，利用两束相互之间相对角度为45°的线偏振光来确定对准误差和延迟误差。基于这些结果，可以通过软件校正算法对对准误差和延迟误差进行补偿，而无需任何精确的机械调整。通过数值模拟和实验验证了所提出方法的有效性和可行性。易于实现的优点使得这种校准方法更适合在实验室中应用，并有望用于通道式光谱偏振仪的校正。
