| Optical precision displacement measurement can be realized as a typical method of large range and high precision displacement measurement,and it is widely used in traditional manufacturing industry and information industry.By changing the measured displacement into the phase of the modulated signal,with the characteristics of high precision and high stability,the heterodyne interferometer become the main technical means of optical measurement.The performance of the heterodyne interferometer displacement measurement system depends on the measurement principle and the optical path structure.On the other hand,it mainly depends on the phase measurement accuracy of the interference signal.In this paper,based on the heterodyne interferometer plane displacement measurement system with the physical grating as the measuring datum,in order to realize the high precision phase measurement,it has carried out a comprehensive and in-depth study on the whole electronic system including analog circuit,digital circuit and communication software.The specific work and the main innovation points of this paper are as follows:1 The working principle of the heterodyne interferometer plane displacement measurement system is analyzed.The function relationship between two dimensional displacement and signal phase is established.Based on the characteristics of the reference signal and the measurement signal,the overall design scheme of the electronic system of displacement measurement is proposed to realize high precision multi-channel synchronous phase measurement.By coordinating the signal processing and communication between analog circuit,digital circuit and communication software,the accurate detection and real-time display of the phase information of the interference signal is ensured.2 Designed and manufactured the analog circuit of heterodyne interferometer grating displacement measuring system.A high power low noise bipolar current source module,a high sensitivity amplification circuit,a frequency mixing filter and a hysteresis comparison square wave conversion circuit are developed for the low intensity of the heterodyne interferometer signal.Realized the detection of 2.7 MHz interference signal,the SNR is 60 d B,and the low frequency square wave signal with complete phase information is obtained.3 Designed and manufactured the digital circuit of the heterodyne interferometric grating displacement measuring system.In view of the low frequency square wave signal obtained by the analog circuit output,a method of combined integer and fractional phase measurement based on pulse filling method is proposed.The hardware circuit of multi-channel signal phase measurement based on FPGA is developed.Use the same clock benchmark to synchronously detect the signal and parallel processing,to ensure the real-time detection of multi-channel signal phase.The communication software of the grating displacement measuring system is made by using the virtual instrument,to realize the fast communication and real-time display of the measurement.4 The experimental results verify the performance of analog circuit and digital circuit of the high precision multi-channel phase measurement,The performance of analog circuit and digital circuit is tested by using signal generator to simulate various kinds of interference signals,In the end,the design of the phase measurement system and the optical system is combined to test the plane displacement provided by the na no positioning table.The test results show that the phase measurement system can achieve 0.18 degree phase resolution,and the corresponding displacement resolution is 0.25 nm,which satisfies the requirements of high precision multi-channel phase synchronous phase measurement. |
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