调频连续波激光测距系统的振动补偿仿真研究
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摘要
在双光路调频连续波激光测距过程中,振动将光程差变化转为拍频信号不需要的相位调制,并在拍频信号中引入多普勒频移,导致拍频信号的频谱发生严重展宽和频移,无法根据拍频频率计算距离值。为解决该问题,提出一种基于四波混频效应的振动补偿方法,该方法利用四波混频技术产生与原频率扫描信号扫描方向相反的新频率扫描信号,通过两个频率扫描信号的测量拍频信号计算距离值。结果表明:当扫描带宽为10nm,待测距离为5m,待测目标以2Hz的频率进行行程为100μm的周期性位移时,基于四波混频效应的振动补偿方法能有效消除振动对测距的影响,测量标准差由补偿前的1.062mm减小为29μm;该方法无需测量振动位移便可直接获取消除振动影响的距离值,极大地简化了系统的硬件部分。
In the process of dual-path frequency-modulated continuous-wave laser ranging,the vibration converts the optical-path difference into an unnecessary phase modulation of a beat-frequency signal.In addition,the Doppler shift is introduced into this beat-frequency signal,which results in the serious broadening and frequency shift in the spectrum of beat-frequency signals.Thus the distance cannot be calculated according to the beat-frequency.To solve this problem,we propose a vibration compensation method based on the four-wave mixing effect,in which the fourwave mixing technology is utilized to generate a new frequency-sweeping signal opposite to the sweeping direction of the original frequency-sweeping signal,and the distance value can be calculated according to the measured beatfrequency signal of two frequency-sweeping signals.The results show that when the sweeping bandwidth is 10 nm,the measurement distance is 5 mand the target has a periodic displacement of 100μm at a frequency of 2 Hz,the influence of vibration on laser ranging can be effectively eliminated with the vibration-compensation method based on the four-wave mixing effect,and the measurement standard deviation is reduced from 1.062 mm before compensation to 29μm.In this method,the distance value after elimination of vibration influence can be directly obtained without the need of measuring vibration displacement,and the hardware part of the system is greatly simplified.
In the process of dual-path frequency-modulated continuous-wave laser ranging,the vibration converts the optical-path difference into an unnecessary phase modulation of a beat-frequency signal.In addition,the Doppler shift is introduced into this beat-frequency signal,which results in the serious broadening and frequency shift in the spectrum of beat-frequency signals.Thus the distance cannot be calculated according to the beat-frequency.To solve this problem,we propose a vibration compensation method based on the four-wave mixing effect,in which the fourwave mixing technology is utilized to generate a new frequency-sweeping signal opposite to the sweeping direction of the original frequency-sweeping signal,and the distance value can be calculated according to the measured beatfrequency signal of two frequency-sweeping signals.The results show that when the sweeping bandwidth is 10 nm,the measurement distance is 5 mand the target has a periodic displacement of 100μm at a frequency of 2 Hz,the influence of vibration on laser ranging can be effectively eliminated with the vibration-compensation method based on the four-wave mixing effect,and the measurement standard deviation is reduced from 1.062 mm before compensation to 29μm.In this method,the distance value after elimination of vibration influence can be directly obtained without the need of measuring vibration displacement,and the hardware part of the system is greatly simplified.
引文
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[2]Yao Y N,Zhang F M,Qu X H.Hardware-based equispaced-phase resampling nonlinearity correction algorithm and spectral analysis method[J].Acta Optica Sinica,2016,36(12):1212003.姚艳南,张福民,曲兴华.基于硬件的等光频间隔采样及频谱分析方法[J].光学学报,2016,36(12):1212003.
[3]Shi G,Zhang F M,Qu X H,et al.High-resolution frequency-modulated continuous-wave laser ranging for precision distance metrology applications[J].Optical Engineering,2014,53(12):112402.
[4]Kakuma S,Katase Y.Frequency scanning interferometry immune to length drift using apair of vertical-cavity surface-emitting laser diodes[J].Optical Review,2012,19(6):376-380.
[5]Tao L,Liu Z G,LüT,et al.Drift error compensation method of frequency sweeping interferometer by consecutive forward and reverse optical frequency scanning[J].Acta Optica Sinica,2014,34(2):0212002.陶龙,刘志刚,吕涛,等.频率扫描干涉仪漂移误差正反向扫描补偿法[J].光学学报,2014,34(2):0212002.
[6]Lu C,Liu G D,Liu B G,et al.Absolute distance measurement system with micron-grade measurement uncertainty and 24mrange using frequency scanning interferometry with compensation of environmental vibration[J].Optics Express,2016,24(26):30215-30224.
[7]Liu G D,Xu X K,Liu B G,et al.A method of suppressing vibration for high precision broadband laser frequency scanning interferometry[J].Acta Physica Sinica,2016,65(20):209501.刘国栋,许新科,刘炳国,等.基于振动抑制高精度宽带激光扫频干涉测量方法[J].物理学报,2016,65(20):209501.
[8]Meng X S,Zhang F M,Qu X H.High precision and fast method for absolute distance measurement based on resampling technique used in FM continuous wave laser ranging[J].Acta Physica Sinica,2015,64(23):230601.孟祥松,张福民,曲兴华.基于重采样技术的调频连续波激光绝对测距高精度及快速测量方法研究[J].物理学报,2015,64(23):230601.
[9]Shi G,Zhang F M,Qu X H,et al.Absolute distance measurement by high resolution frequency modulated continuous wave laser[J].Acta Physica Sinica,2014,63(18):184209.时光,张福民,曲兴华,等.高分辨率调频连续波激光绝对测距研究[J].物理学报,2014,63(18):184209.
[10]Meng X S,Zhang F M,Qu X H.Optimization of the signal processing in frequency modulated continuous wave laser ranging system[J].Proceedings of SPIE,2015,9446:94461Q.
[11]Schneider R,Thuermel P,Stockmann M.Distance measurement of moving objects by frequency modulated laser radar[J].Optical Engineering,2001,40(1):33-37.
[12]Ahn T J,Kim D Y.Analysis of nonlinear frequency sweep in high-speed tunable laser sources using a selfhomodyne measurement and Hilbert transformation[J].Applied Optics,2007,46(13):2394-2400.
[13]Deng Z W,Liu Z G,Li B,et al.Precision improvement in frequency-scanning interferometry based on suppressing nonlinear optical frequency sweeping[J].Optical Review,2015,22(5):724-730.
[14]Liu Z,Liu Z G,Deng Z W,et al.Suppression of nonlinear frequency sweep in frequency sweeping interferometer based on order tracking technique[J].Acta Optica Sinica,2016,36(1):0112003.刘哲,刘志刚,邓忠文,等.扫频干涉测距光频率非线性阶次跟踪抑制方法[J].光学学报,2016,36(1):0112003.
[15]Zheng J.Analysis of optical frequency-modulated continuous-wave interference[J].Applied Optics,2004,43(21):4189-4198.
[16]Zhang Q Y.Study on application of SOA-FWM effect in RoF system[D].Chengdu:University of Electronic Science and Technology of China,2014:3-5.张巧燕.SOA-FWM效应在RoF系统中的应用研究[D].成都:电子科技大学,2014:3-5.
[17]Zheng Z Z.Research on four-wave mixing wavelength conversion based on semiconductor optical amplifiers[D].Wuhan:Huazhong University of Science and Technology,2003:24-26.郑泽洲.基于半导体光放大器四波混频型波长转换的研究[D].武汉:华中科技大学,2003:24-26.
[18]Bava G P,Osella G,Debernardi P.Highly nondegenerate four-wave mixing in semiconductor laser oscillators[J].Optics Letters,1995,20(15):1643-1645.