Adaptive correction of retardations with immunity to alignment errors for a channeled spectropolarimeter.

Retardation errors of high-order retarders will decrease the accuracy of a channeled spectropolarimeter. Taniguchi et al. have proposed a self-calibration method to calibrate the retardations [Opt. Lett.31, 3279 (2006)OPLEDP0146-959210.1364/OL.31.003279]; however, they do not take into account the inevitable alignment errors of high-order retarders. In this paper, an adaptive correction method with immunity to alignment errors is proposed to reduce the effects of temperature variation on retardations. By separating and analyzing the amplitude terms and phase terms contained in the measurement data, the phase terms are utilized to correct the retardations, which makes the effectiveness of this adaptive correction method immune to the inevitable alignment errors of high-order retarders. The adaptive correction process can be accomplished in parallel to the measurement process without any auxiliary resources. The effectiveness and feasibility of this method is verified by simulations and experiments. The convenience and simplicity of the presented method make it extremely suitable for application on track.