Research On Signal Processing Method Of Single Frequency Laser Interferometer Based On FPGA

The laser interferometry technology is widely applied in the field of precision measurement,for it has the advantages of large range(meter-level),nano-scale resolution and wavelength-based reference traceability.With the higher requirements of precision measurement,the properties of precision,resolution and measurement speed have been improved for laser interferometric measurement technologies.Single-frequency laser interferometers are the significant methods for the interferometric displacement precision measurement.However,the single-frequency laser interferometer is a direct current measurement system,and is affected by the environment with large zero drift.It is of great significance to enhance the anti-interference ability of the single-frequency laser interferometer and improve its signal processing method.This dissertation mainly analyzes the error source of single-frequency laser interferometer and studies the error correction method.The CORDIC algorithm is used for phase subdivision,which effectively overcomes the shortcomings of traditional single-frequency laser interferometer error correction method.A signal processing system based on FPGA is designed to improve the disadvantages of low real time and low speed in signal processing of single frequency laser interferometer.The main research work of this dissertation is as follows:1.Analyze the error sources of single-frequency laser interferometers and design effective error correction methods and a phase subdivision method based on CORDIC algorithm.This method can realize high-speed signal phase subdivision.2.For the optical structure of a single-frequency laser interferometer,design the pre-stage circuit that matches the interference optical path structure,including the design of the photoelectric conversion circuit and the pre-amplification circuit.Using FPGA high-speed signal processing platform,design the AD converter circuit and FPGA interference signal processing system,and realize the hardware platform of signal processing.3?Set up the single-frequency laser interferometer measurement system and compare the measurement results with that of Renishaw XL-80 laser interferometer,which calibrates the effectiveness of the measurement system.The experimental results show that the single-frequency laser interferometer measurement system designed in this dissertation can achieve nano-resolution,whose stability is less than 100 nm.