Phase modulation depth extraction and correction and nonlinear influence factor elimination method and system in PGC-Atan demodulation method

The invention relates to a phase modulation depth extraction and correction and nonlinear influence factor elimination method and system in a PGC-Atan demodulation method. The light source modulation module generates a high-frequency carrier, an interference signal modulated by the high-frequency carrier and a signal to be measured is processed into an electric signal, and the electric signal is mixed with a carrier frequency-doubled sinusoidal signal, a carrier frequency-doubled cosine signal and a carrier frequency-doubled cosine signal. Carrying out arc tangent operation on a pair of signals mixed and multiplied with the carrier-frequency-doubled signal to extract carrier phase delay; and ellipse fitting is carried out on a pair of signals mixed and multiplied with the carrier cosine signal. And the phase modulation depth is extracted by combining carrier phase delay and ellipse fitting parameters and is fed back to the light source modulation module for closed-loop control. A pair of strictly orthogonal s