Signal processing method for heterodyne interferometer

Abstract

The invention discloses a signal processing method for a heterodyne interferometer. The method comprises the following steps of: providing a Span3-series XC3S1500 chip for an FPGA (Field Programmable Gate Array), chopping a reference signal and a measurement signal through a high-frequency small-power Schottky diode respectively to obtain positive half period signals and connecting with a pin of the FPGA; countering two paths of signals respectively at the counting period of 100 mum s and latching every 100 mum s, wherein the phase difference of the entire period is N1-N2; setting a count value of an initial phase difference in a first sampling counting period as n1 and latching by taking a reference signal as a standard, setting a count value of a tail end phase difference as n2, and setting a count value of a non-period phase different as n2-n1; setting a count value of an ith non-period phase difference as ni+1-n1; performing pulse filling counting on one period of the reference signal to obtain a count value NTr of the reference signal in the entire period; setting the phase difference in the sampling period as (N1-N2)+(ni+1-n1) / NTr; and obtaining measured displacement: L=lambda / 2[(N1-N2)+(ni+1-n1) / NTr], wherein lambda is a laser wavelength, (i=1,2,---,n). According to the method, dynamic and real-time measurement of phases can be realized, a high resolution is achieved.

Description

technical field [0001] The invention belongs to the technical field of nanometer measurement, and in particular relates to a signal processing method of a heterodyne interferometer. Background technique [0002] In the field of precision measurement and ultra-precision measurement, laser interferometry is more widely used. In the development process of laser interferometry, the measurement accuracy has reached the micronano and nanometer level. The application of photoelectric conversion devices and electronic technology has changed the processing method of heterodyne signals. Technologies such as heterodyne, quasi-heterodyne, automatic recording, and electronic subdivision have greatly improved the processing accuracy and speed of interference signals. "AC" interference, that is, according to the idea of ​​moving the effective signal spectrum to the high frequency band, the signal-to-noise ratio of the interference signal is greatly improved. With the rapid development of...

AI Technical Summary

Problems solved by technology

However, the limitation of the phase measurement method is that it is suitable for static measurement, and the dynamic measurement is not perfect, that is, the measurement accuracy is not high enough, and the real-time performance is not good enough.

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