Method and system thereof for signal demodulation of heterodyne laser

Abstract

The invention provides a method and a system thereof for signal demodulation of heterodyne laser. The method comprises the following steps of performing 90-degree phase shifting on a Doppler carrier signal outputted by a heterodyne laser interferometer to form two paths of orthogonal carrier signals; respectively performing frequency dropping processing on the two paths of orthogonal carrier signals to obtain two paths of low-frequency signals, wherein during frequency dropping processing, the two paths of orthogonal carrier signals are subject to frequency mixing by an external local oscillation signal; converting the two paths of low-frequency signals into two paths of discrete voltage signals by an analog to digital converter, calculating a phase modulation value sequence, and demodulating the acceleration amplitude and the initial phase angle of oscillation. The method has the advantages that the requirement of data collecting speed is greatly decreased, the problem of huge data and difficult solving in the data solving are reduced, the low-frequency vibration is measured by the heterodyne laser interferometer, the same-clock method is adopted in the zero frequency change process, the influence of interference on the measuring result by the outside environment is avoided, and the measuring stability and measuring accuracy are improved.

Description

technical field [0001] The invention relates to the field of mechanical vibration and shock measurement, in particular to a signal demodulation method and system of a heterodyne laser. Background technique [0002] With the advancement of science and the development of society, the requirements for mechanical vibration measurement are also increasing, mainly reflected in the absolute calibration requirements of vibration acceleration, velocity and displacement sensors and measuring instruments. Carrier technology converts the information of the measured physical quantity into a frequency-modulated or phase-modulated signal. Therefore, it has the characteristics of strong anti-interference ability, fast measurement speed, high signal-to-noise ratio, and easy to achieve high-resolution measurement. It has been greatly developed. It has unique advantages in the measurement of small vibrations. [0003] In heterodyne interferometry, a heterodyne laser interferometer shifts the ...

AI Technical Summary

Problems solved by technology

[0003] In heterodyne interferometry, a heterodyne laser interferometer shifts the frequency of light by means of an acousto-optic modulator f c (such as f c =40MHz), the Doppler frequency shift Δf generated by the vibration will carry the carrier to f c , the frequency of the electrical signal output by the photoelectric receiver is f c +Δf, due to the high carrier frequency, it is difficult to collect data and calculate a large amount of data after collection. Usually, this frequency needs to be down-converted to a lower carrier frequency modulation signal to reduce Data acquisition and data calculation are difficult, but for low-frequency vibration, the vibration period is long, and the acquisition of carrier signal still forms a huge amount of data, which increases the difficulty of calculation, low-frequency vibration cannot be measured, and the lower limit of demodulation vibration frequency is limited

Images