On the issue of achieving subpicometric resolution by acousto-optic two-channel laser displacement interferometer with two different frequency photodetectors

Abstract

The article discusses an acousto-optical (AO) heterodyne laser displacement interferometer (LDI) with two different-frequency photodetectors: highfrequency (HF) and low-frequency (LF) low-noise, working with «fast inaccurate» and «slow accurate» measuring channels, respectively. The mode of operation of AO LDI at start-stop cyclic motions of objects is described, which provides high resolution at the initial and final stages of motions with low speeds of motion. A metrological analysis of the «slow accurate» channel is carried out taking into account the noise frequency characteristics of photodetectors with the formation of its so-called «optimistic» and «pessimistic» variants. Based on the metrological analysis carried out, the frequency ranges of the signal are determined, which allow achieving the resolution of AO LDI subpicometric values at low speeds.

Keywords

• laser displacement interferometer
• phaselocked frequency system
• acousto-optic modulator
• photodetector noise
• signal jitter
• picometer
• smallrange phase meter