Optical Heterodyne Interferometry Based on Two-stage or Multi-stage Resonant Filtering to Eliminate Nonlinear Errors

Abstract

The invention discloses an optical heterodyne interference method for eliminating non-linear errors based on two-stage or multi-stage resonant filters, and belongs to the field of optical heterodyne interference. The method comprises the steps of trying to obtain at least three paths of signals in a light path with non-linear error interference components, enabling respective periodical non-linear error interference components of the at least three paths of signals to be different from one another in phase angles of signal frequency components to be eliminated within the corresponding circumferential angle range or within the corresponding circumferential angle range excluding integral multiples of circumferential angles, and adopting the filters composed of two-stage or more-stage parallel-connection or series-connection inductance capacitance resonant loops to filter the signals in an analog electric signal channel so as to conduct follow-up electronics processing to eliminate or restrain the interference components after analog-digital conversion. According to the optical heterodyne interference method, the non-linear errors or interferential specific harmonic components can be eliminated, the adjustment process is quite easy, the system performance is improved, and cost is reduced.

Description

technical field [0001] The invention belongs to the field of optical heterodyne interferometry (Heterodyne Interferometry) measurement, and specifically relates to an optical heterodyne interferometry method based on a two-stage or more than two-stage resonance filter method to eliminate nonlinear error fundamental frequency without fine adjustment. Background technique [0002] The laser heterodyne interferometry system can be used to measure physical quantities such as displacement and length, and is one of the best nanometer measurement methods. The system converts the measured displacement into the frequency or phase change of the heterodyne signal, and then measures this change. Since the frequency of the heterodyne signal is much lower than the optical frequency, the photoelectric signal is easy to process and can be electronically fine-tuned. Points to achieve higher measurement resolution, the resolution can reach picometer (pm) or better. [0003] However, nonlinea...

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Problems solved by technology

[0005] In order to solve the technical problems existing in the existing laser heterodyne interferometry system, such as complex system, large amount of computation, poor real-time performance, and inaccurate results, the present invention provides a Level and above) resonant filtering and FFT (fast Fourier transform) algorithm to eliminate nonlinear error optical heterodyne interferometry, can eliminate nonlinear error or specific harmonic components of interference, and eliminate the precision required to eliminate nonlinear error Optical adjustments and precision adjustment process make this adjustment very easy, while greatly improving system performance and reducing cost

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