Phase demodulating method based on heterodyning interference signal

Abstract

The invention relates to a phase demodulating method based on a heterodyning interference signal, which comprises the following steps: 1, enabling an exchanging reference signal Sr and a measurement signal Sm to pass through a two-way zero crossing comparison circuit, then reshaping the exchanging reference signal Sr and the measurement signal Sm to be intermediate frequency square signals so as to obtain an intermediate frequency square reference signal Qr and an intermediate frequency square measurement signal Qm; 2, enabling the intermediate frequency square reference signal Qr and the intermediate frequency square measurement signal Qm to pass through a self-reference phaselocked loop trend tracking frequency reducing module, then converting the intermediate frequency square reference signal Qr and the intermediate frequency square measurement signal Qm to low frequency square signals so as to obtain a low frequency square reference signal Wr and a low frequency square measurement signal Wm; 3, inputting the intermediate frequency square reference signal Qr, the intermediate square measurement signal Qm, the low frequency square reference signal Wr and the low frequency square measurement signal Wm to a digital phase measurement module based on FPGA (field programmable gate array) and taking phase measurement and integration on integral decimals; and 4, outputting results. According to the invention, the self-reference phaselocked loop trend tracking frequency reduction and the digital phase measurement technology based on the FPGA are adopted, phase demodulating for laser heterodyning interference signals can be achieved in a large scope and with high precision, and the test performance of a system can be guaranteed.

Description

technical field [0001] The invention mainly relates to the technical field of optical precision measurement, in particular to a phase demodulation method based on heterodyne interference signals. Background technique [0002] "Laser heterodyne interferometry" is to introduce a carrier wave to the change of interference fringes, so that the DC signal system of ordinary interferometry is transformed into the AC signal system of heterodyne interferometry, thereby greatly enhancing the anti-interference ability and stability of the system. It has With the advantages of high measurement accuracy, fast response speed, large measurement range, high signal-to-noise ratio, ability to overcome direction ambiguity and not be affected by light intensity changes, it has been widely used in the field of optical precision measurement and nanotechnology measurement. However, the conventional ordinary heterodyne interferometry system also has the problem of unstable and large fluctuations in...

AI Technical Summary

Problems solved by technology

The advantage of the frequency demodulation method is that it has a large measurement range, has the ability of integer counting, can perform dynamic measurement, and can measure the phase zero point. Its disadvantage is that the circuit is very complicated. Although it has a certain level of subdivision ability, it is difficult to achieve high precision.

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