High reliability sinusoidal phase modulating interferometer combined reference signal and PGC-EFA-Arctan algorithm

Abstract

The ellipse fitting algorithm (EFA) is commonly used in correction of the orthogonal interference signal pair for phase generated carrier (PGC) demodulation schemes to eliminate nonlinear errors. However, it often happens that the interference signal cannot form an effective Lissajous ellipse in some applications. In this paper, a highly reliable sinusoidal phase modulating interferometer (SPMI) combined a reference signal and PGC-EFA-Arctan (arctangent) algorithm is proposed. In this interferometer system, the reference signal is provided by a reference interferometer that shares the same modulation optical path with the measurement interferometer. The target detected by the reference interferometer is maintained at a vibration with appropriate amplitude and frequency, thereby ensuring a stable and accurate ellipse fitting result for the orthogonal signal pair correction of the measurement interferometer. The numerical simulation results have illustrated the theoretical effectiveness of the proposed SPMI in scenarios where the interference signal of the measurement interferometer is affected by significant light intensity disturbances (LID). The comparative experiments conducted on ellipse fitting results between the two interferometers have confirmed the feasibility of the proposed SPMI. Experiments under various conditions have validated the effectiveness of the proposed SPMI in enhancing the demodulation reliability, particularly with significant LID. Nano displacement measurement experiments indicate that the proposed SPMI offers better demodulation stability and accuracy with a deviation of less than 2 nm when Lissajous ellipse arc length of measurement signal is extremely short. The linearity of the proposed SPMI exceeds 99.99%, and the dynamic range reaches 95.69 dB @ 55 Hz, surpassing the 90.29 dB @ 55 Hz achieved by the typical SPMI that uses conventional PGC-EFA-Arctan demodulation scheme.