Highly accurate phase demodulation algorithm for white light interference

Abstract

In traditional white light interference phase demodulation technology (T-WLPDT), the accuracy issue caused by delay time has always existed. To control the distortion degree within a certain range, it is inevitable that operating bandwidth is necessary to be sacrificed. In this paper, the ratio between demodulation signal output by T-WLPDT and true signal is derived and formulated as compensation factor (CF). CF is then applied to compensate for the spectral signal output by T-WLPDT, thereby achieving high-accuracy demodulation and expansion of operating bandwidth. The experiment result shows that compared to T-WLPDT, the bandwidth of compensated white light interference phase demodulation technology (C-WLPDT) has extended 16 dB (6.28 times), with the distortion limited to 1.69 %. Besides, the study analyzed the advantages of phase compression of white light interference in demodulating low-frequency large phase-amplitude signals. When demodulating signals of 100 Hz, C-WLPDT presents 41 dB (108.1 times) phase compression, enabling measurement of signals with larger phase-amplitude than narrow linewidth laser phase demodulation technology (NLPDT). The work is of great significance to improve measurement accuracy of white light interference, and promotes it more applicable to the sensing field. Meanwhile, the phase compression performance of C-WLPDT provides an idea to detect low-frequency large phase-amplitude signals.