Analysis and swing control of optical path scanning model of double-moving mirror swing interferometer

Interferometer is the core component of the Fourier transform infrared spectrometer (FTIR). The scanning accuracy and stroke of the moving mirror directly affect the signal-to-noise ratio (SNR) and resolution of the instrument. In order to obtain high-quality spectra, a double-moving mirror swing interferometer with compact structure and small size was designed. Through modeling and analysis of the interferometer, the optical path difference (OPD) expression of this interferometer was obtained. The relationship between the optical path scanning speed and the swing speed of the swing arm was analyzed, and the impact of speed fluctuation on the SNR of the spectrum was pointed out. A nonlinear PI controller based on a disturbance observer was proposed to control the rotary voice coil motor (RVCM), and the controller was simulated and verified. The results prove that the speed stability of the optical path scanning system is higher than 99%, which effectively reduces the impact of external disturbances on the system.