A sine phase modulation laser interferometer and carrier generation and signal demodulation method

Abstract

The invention discloses a sine phase modulation laser interferometer and a carrier wave generation and signal demodulation method. The high-frequency acoustic waves are used to generate high-frequency liquid surface acoustic waves at the gas-liquid interface, and the reference light of the homodyne interferometer is incident on the gas-liquid interface. At the interface, the high-frequency liquid surface acoustic wave modulates the phase of the reference light to realize the generation of the phase carrier of the homodyne interference signal; it can solve the problem that the existing PGC demodulation method needs to realize the high-frequency sinusoidal phase modulation of the reference arm of the homodyne interferometer, and realize the High frequency sinusoidal phase modulation requires expensive components. The invention adopts Arctan demodulation algorithm based on real-time normalization to eliminate the influence of carrier phase delay caused by low-frequency capillary waves on liquid surface and carrier modulation depth variation caused by power fluctuation of electroacoustic transducer on demodulation results.

Description

technical field [0001] The invention relates to the technical field of laser interferometry, in particular to a sinusoidal phase modulation laser interferometer and a carrier wave generation and signal demodulation method. Background technique [0002] For the laser interferometry method, in order to achieve the resolution of the measured displacement nanometer, the phase demodulation of the interference signal must be realized. To demodulate the phase of the interference signal, the orthogonal interference signal pair must be obtained through the optical path or signal processing algorithm. At present, three methods are often used to obtain the orthogonal interference signal pair: using a heterodyne interferometer and a specific signal processing algorithm; using zero A differential interferometer combined with a polarizing beamsplitter and uses two photodetectors to obtain quadrature signals; a homodyne interferometer with sinusoidal phase modulation and specific signal pr...

AI Technical Summary

Problems solved by technology

However, it is very difficult to precisely adjust the modulation depth to 2.63rad, and it is not the best value in terms of demodulation error and signal-to-noise ratio

[0005] In addition, the PGC demodulation method needs to use devices such as electro-optic modulators or acousto-optic modulators to realize high-frequency sinusoidal phase modulation on the reference arm of the homodyne interferometer, so that the interference signal generates a phase carrier; however, these devices are expensive, and Its driving equipment also often costs a lot, which greatly increases the cost of the entire measurement system

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