High-precision phase-shift method for heavy-load reference mirror based on capacitance sensor monitoring

To address the problems associated with the high-precision phase shift of heavily loaded reference mirrors in large-aperture interferometry, this study proposes a high-precision phase-shifting method based on capacitance sensor monitoring. This method achieves spatial nanoscale phase shifting for a heavy-load reference mirror via spatial three-point synchronous driving of piezoelectric ceramics combined with flexible hinges. The highly sensitive spatial translation of a heavy-load reference mirror is achieved through the gravitational loading of air-floating support and the spatial translation motion modeling of the reference mirror. Nano precision phase-shifting feeds are achieved through spatial in-situ monitoring by combining capacitive sensors and piezoelectric ceramics with a proportion integration differentiation closed-loop drive. Finally, high-precision and high-stability mechanical phase shifting in large-aperture interferometry circumvent the principal shortcomings of existing large-aperture wavelength-tuned phase shifting. The experimental results reveal that the established heavy-load reference mirror mechanical phase shift system has a resolving power of 1.1 nm, frequency response of 120 Hz, and synchronization accuracy of 2° for three-phase shift quantities. This method provides a novel phase-shifting technique for constructing large-aperture phase-shifting interferometers.