Theoretical research of retarder phase deviation in channeled Mueller matrix spectropolarimeters

Channeled Mueller matrix spectropolarimeters (CMMSPs) have gained increasing popularity in recent years due to no moving parts. However, in order to obtain more accurate measurements, thorough studies on the influence and correction of their systematic errors are still needed. This paper presents a novel perspective for CMMSPs based on a signal processing technique, and propose a coherence demodulation method to extract channel signals in the modulated intensity. From theoretical analysis, the influence of phase deviation resulting from the imperfection of retarders is pinpointed. Meanwhile, the mechanism of phase deviation is described in theory and visually displayed by simulation. To mitigate the interference of retarder phase deviation, this work proposes a way for correction utilizing a vacuum and polarizer as determinant samples. Noticeably, the phase deviations are treated as a whole and represented by polynomials during correction. The reverse process of error mechanism is used to correct the influence. Finally, this means is proved by a series of simulation validations with a detector noise of 30 dB and retarder misalignment errors of 0.5°.