Improved PGC-Arctan demodulation scheme with immunity to carrier phase delay and modulation depth

As one of the most popular interferometric phase demodulation techniques, phase generated carrier (PGC) demodulation technique has been widely used in fields of high-precision measurement and sensing. Carrier phase delay (θ) and modulation depth (C) are two critical factors affecting the fidelity of the demodulation results. Inappropriate values of θ or C will lead to nonlinear distortions for the basic Arctan demodulation scheme or linear distortions for the differential-cross-multiplying (DCM) demodulation scheme in the demodulated results. To overcome these problems, an improved Arctan demodulation scheme with immunity to θ and C is proposed. As expected from theoretical analysis, simulation results have confirmed the insensitivity of the improved scheme to θ and C compared with the basic Arctan and DCM schemes. A sinusoidal phase modulation interferometer was constructed to further test the performance of the proposed scheme. Experimental results show that, with θ changes from 0° to 180° or C changes from 1.5 rad to 3.5 rad, the demodulated results of the improved Arctan scheme have a low THD less than 0.5 %, a high SINAD greater than 45 dB and stable amplitude with standard deviation of less than 0.01 rad, demonstrating the immunity of the proposed scheme to carrier phase delay and modulation depth.