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Zero difference orthogonal laser interference signal generation method based on software phase shift

A technology of laser interference and signal generation, applied in the direction of using optical devices, measuring devices, instruments, etc., can solve the problems of high cost, inability to demodulate and process photoelectric signals correctly, deviation, etc., and achieve the effect of saving hardware costs and occupying space

Active Publication Date: 2017-12-01
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, since the above-mentioned laser interferometer needs two orthogonal photoelectric signal outputs, this requires the use of optical phase shifting components such as quarter-wave plates, but due to the quarter-wave plates, The influence of factors such as the installation and adjustment position of the polarization beam splitter may cause the phase difference of the two output orthogonal photoelectric signals to deviate from 90°. When the deviation from the nominal angle of 90° exceeds ±20°, the two orthogonal photoelectric signals The Lissajous figure composed of alternating photoelectric signals is an ellipse with a large eccentricity. Such two-way photoelectric signals cannot be correctly processed for subsequent demodulation.
Moreover, phase shifting is realized from the hardware, plus an additional set of photoelectric conversion equipment and high-speed data acquisition system, the cost is expensive

Method used

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  • Zero difference orthogonal laser interference signal generation method based on software phase shift
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  • Zero difference orthogonal laser interference signal generation method based on software phase shift

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Embodiment 1

[0026] Such as figure 1 , a homodyne orthogonal laser interference signal generation method based on software phase shifting, comprising the following steps:

[0027] Step 1: Obtain a single-channel signal: the single-channel photoelectric signal output from the Michelson laser interferometer is read by the data acquisition card, and the single-channel photoelectric signal is sampled according to the cycle of the measured vibration signal.

[0028] Step 2: Normalization processing: Due to the influence of photoelectric conversion and amplifier circuit gain and zero point drift, the output photoelectric signal may have a peak voltage of not 1 V or an average value of not 0. In order to facilitate the subsequent alternate phase shift algorithm processing The photoelectric signal needs to be normalized, that is, the amplitude of the photoelectric signal is scaled to a peak value of 1 V, and the DC amount is removed to obtain a signal with an average value of 0.

[0029] Step 3: ...

Embodiment 2

[0040] The difference between this embodiment and embodiment 1 is that the specific method for obtaining the correction signal in step 3 is different, except for the step of obtaining the correction signal, other steps are the same as in embodiment 1.

[0041] The acquisition of the correction signal in step 3 includes the following steps:

[0042] Step 3.1: Determine whether the initial value of the normalized signal is at the phase inversion point, if so, use the normalized signal as the correction signal; if not, go to step 3.2;

[0043]Step 3.2: Perform a differential operation on the normalized signal, and obtain the upper envelope curve of the signal after the differential operation; in order to reduce the influence of noise and obtain an accurate minimum point, perform appropriate low-pass filtering on the upper envelope curve , and then search for the minimum value. Low-pass filtering may not be used when the noise effect of the original signal is negligible.

[0044...

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Abstract

The invention discloses a zero difference orthogonal laser interference signal generation method based on software phase shift. The method includes the following steps: acquiring a signal path photoelectric signal from a laser interferometer according to integral sampling; proportionally scaling the photoelectric signal such that the peak value of the amplitude is 1V, and also eliminating a DC amount to obtain a normalized signal of which the average amplitude is zero; adaptively correcting the normalized signal to obtain a correction signal which has an initial value at a phase position inversion point and which meets the characteristics of integral sampling; alternatively conducting +90 DEG and -90 DEG phase shift on the correction signal in half cycle, obtaining a phase shift signal; and the phase shift signal and the signal path photoelectric signal from the laser interferometer forming two paths of orthogonal photoelectric signals. According to the invention, the method herein is advantaged by obviating the need for hardware in performing phase shift and the fact that the phase positions of the two paths of the orthogonal photoelectric signals have a phase difference of +90 DEG or -90 DEG.

Description

technical field [0001] The invention relates to a method for generating a homodyne orthogonal laser interference signal based on software phase shifting, which can realize the generation of two homodyne orthogonal laser interference signals by using a single laser interference signal, which is used for the amplitude-frequency characteristics and phase-frequency characteristics of vibration sensors Absolute measurement. technical background [0002] In the current national standard, the homodyne orthogonal laser interferometer is recommended for the absolute measurement of the amplitude-frequency characteristics and phase-frequency characteristics of vibration sensors, such as the homodyne laser interferometer based on the quadrature output of the National Institute of Metrology of China. However, since the above-mentioned laser interferometer requires two orthogonal photoelectric signal outputs, this requires the use of optical phase shifting components such as quarter-wave ...

Claims

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Application Information

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IPC IPC(8): G01B9/02
CPCG01B9/0201
Inventor 何闻谢智郎郝凌凌
Owner ZHEJIANG UNIV