Frequency-modulated continuous-wave laser interferometry displacement sensor based on centroid peak-finding

Zhang Dengpan; Yan Mengchao; Shi Ancun; Li Gaochao; Zhao Xian; Wang Yongjie; Li Fang

doi:10.12086/oee.2023.220315

Article navigation > Opto-Electronic Engineering > 2023 Vol. 50 > No. 6 > 220315

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Zhang D P, Yan M C, Shi A C, et al. Frequency-modulated continuous-wave laser interferometry displacement sensor based on centroid peak-finding[J]. Opto-Electron Eng, 2023, 50(6): 220315. doi: 10.12086/oee.2023.220315

Citation:

Zhang D P, Yan M C, Shi A C, et al. Frequency-modulated continuous-wave laser interferometry displacement sensor based on centroid peak-finding[J]. Opto-Electron Eng, 2023, 50(6): 220315. doi: 10.12086/oee.2023.220315

Frequency-modulated continuous-wave laser interferometry displacement sensor based on centroid peak-finding

1.
School of Mechanical & Power Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China
2.
Laboratory of Optoelectronic System, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China

Fund Project: National Natural Science Foundation of China (42276194)

More Information

^*Corresponding author: wyj@semi.ac.cn

Received Date 28 November 2022

Revised Date 03 February 2023

Accepted Date 08 February 2023

Published Date 25 June 2023

Abstract

Abstract

The frequency-modulated continuous wave laser interferometry is widely used in the field of precision measurement. Aiming at its high-precision displacement demodulation problem, this paper applies the centroid method to the demodulation of its beat signal, proposes a phase demodulation algorithm based on the centroid peak-seeking method, and carries out experiments and analysis. Based on the smooth filtering and peak clipping of the intercepted beat signal, the proposed algorithm obtains the centroid of the beat signal through the centroid coordinate formula. The abscissa of the centroid is the peak position. Finally, the phase discrimination algorithm demodulates the displacement. In the simulation, the SNR is set to 15 dB, the phase error of the algorithm is 0.016 rad, and the displacement error is 2.04 nm. A frequency-modulated continuous wave laser interference displacement measurement system was built for experimental verification. The experimental results show that when the fixed distance is 44 mm, the standard deviation of random displacement error is 2.18 nm. Compared with the conventional zero crossing detection method, the measurement error of the algorithm is reduced by 49%, the resolution is improved, and the algorithm has broad application prospects.
- interferometry /
- frequency-modulated continuous wave /
- phase demodulation /
- centroid peak searching /
- distributed feedback laser

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References

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Overview

Overview

Frequency-modulated continuous wave laser interferometry technology has broad application prospects in modern industrial production due to its advantages of large dynamic range, high precision, and high reliability. The frequency-modulated continuous wave laser is coupled with the Fabry-Perot interferometer in the optical field through optical fiber devices. The signal light and reference light of the interferometer propagate along the same optical fiber arm, which is extremely sensitive to displacement information. The measurement information can be obtained by demodulating the beat signal generated when the reference signal interferes with the measurement signal. In phase demodulation, the extreme point position of the beat frequency signal in one cycle is converted into a change in the initial phase to achieve displacement demodulation. But a beat frequency signal is a kind of sine signal with low signal noise, unequal amplitude, and frequency. It needs signal preprocessing to facilitate the subsequent extreme point location. Determining the precise position of the peak is the key problem in displacement demodulation.

Aiming at the demodulation problem of frequency modulation continuous wave interference beat frequency signal, this paper applies the centroid method to the field of the beat frequency signal demodulation and proposes a phase demodulation algorithm based on the centroid peak finding method. Compared with the existing phase demodulation algorithm, the algorithm does not need amplitude correction. After smooth filtering and minimum point positioning of the signal, the peak point position of the beat frequency signal can be accurately obtained by the centroid method, and the displacement amount can be obtained after phase demodulation according to this peak point position. A frequency-modulated continuous wave interferometric ranging system was constructed, and test experiments were carried out. The random error distribution of the displacement is verified when the length of the F-P cavity is fixed, and the standard deviation of the error is 2.18 nm. In order to compare the centroid peak-finding method proposed in this paper with the conventional zero-crossing detection method, the displacement random error of the two methods is obtained by using the built frequency modulated continuous wave ranging system with fixed different distances, and its standard deviation is calculated. Experimental results show that the measurement error of the method proposed in this paper is reduced by 49% compared to the traditional zero-crossing detection method. It has important research significance in the field of laser interferometry and has broad application prospects in the field of precision measurement.