Method and system for phase measurement of the heterodyne interference system

Abstract

Laser interferometers and grating interferometers are typical optical measurement devices. The measurement resolution and range of the two devices are generally nanometers and meters, so they can meet the needs of high-resolution, largerange measurement. Whether it is a laser interferometer or a grating interferometer, it can be implemented based on a technical route based on the principle of homodyne interference or heterodyne interference. Heterodyne interference is not sensitive to changes in signal amplitude and DC offset, and can effectively avoid measurement errors. To design a highprecision displacement measuring device based on the principle of heterodyne interferometry, the key is whether it can accurately measure the phase change of the measured signal relative to the reference signal. The accuracy of the phase measurement determines the accuracy of the displacement measurement. Phase measurement methods can be divided into two categories: analog method and digital method. In this paper, a high-precision phase measurement system based on FPGA is designed based on the automatic digital phase detection method. The hardware part of the system includes FPGA, high-speed ADC module, signal conditioning circuit, the phase detection algorithm selects the automatic phase detection algorithm, and finally realizes the output display of the phase measurement results. The experimental results show that the deviation between the experimental data of all measurement points and the true value does not exceed 0.1°. Therefore, the accuracy of the phase measurement system designed in this paper is 0.2° and 0.018° resolution.