Residual Compensation Method of Phase Carrier Laser Interferometer Closed-loop Demodulation Algorithm

Abstract

The invention provides a residual error compensation method of a phase carrier wave type laser interferometer closed-loop demodulation algorithm. A system residual error is obtained by multiplying interference optical signals with additional carrier wave signals and performing low-pass filtering, division and an arc tangent, weighted addition is performed on the system residual error and phase signals obtained through closed-loop demodulation, and thus a measurement result is corrected. In a phase carrier wave type laser interferometer closed-loop demodulation process, residual errors with different degrees exist in a system due to restrictions of disturbance factors or traceability. The method has the advantage of a phase modulation laser interference signal closed-loop demodulation method and also has higher demodulation precision at the same time.

Description

technical field [0001] The invention relates to an optical interferometry method, in particular to a method for residual error compensation of phase carrier laser interference signals. Background technique [0002] The phase demodulation algorithm widely used in optical interference sensors is the PGC algorithm. Its principle is to use the input signal and the local phase modulation wave to perform frequency difference processing to obtain the quadrature value of the two measured phases, and then use the quadrature value and the original The signal is multiplied by cross differential, and the measured phase value is obtained through trigonometric function relationship and integral processing. In the 1980s, when digital circuits were not very developed, the algorithm was proposed to solve the problem of engineering practice. However, there are several problems with this algorithm. First, the dynamic range of its work is greatly affected by the phase-modulated wave signal. In...

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Problems solved by technology

However, there are several problems with this algorithm. First, the dynamic range of its work is greatly affected by the phase-modulated wave signal. In addition, the system works in an open-loop state, and there is no feedback loop to ensure the long-term stability of the system.

Another serious problem in the PGC algorithm is that it is easily affected by the associated amplitude modulation. Since the PGC algorithm requires a phase-modulated wave signal to modulate the interferometer, it is easy to cause accompanying amplitude changes in the process of directly modulating the laser phase. Variations can produce large harmonic distortions in the final data result

On the other hand, the closed-loop demodulation algorithm for the phase carrier laser interference signal will also have different degrees of residual error due to disturbance factors or tracking capability limitations

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