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All-phase FFT based distance measurement in laser self-mixing interferometry
Optics and Lasers in Engineering ( IF 4.6 ) Pub Date : 2021-03-19 , DOI: 10.1016/j.optlaseng.2021.106611
Ke Kou , Cuo Wang , Yun Liu

As is widely known in the field of laser self-mixing interferometry (SMI), a commercial laser diode (LD) under linear injection current modulation can serve as a low-cost laser rangefinder, whose self-mixed signal exhibits a beat frequency proportional to the distance to be measured. So exact frequency extraction becomes a significant issue in this measurement scheme. In order to obtain better frequency and then better distance estimation performance, a new frequency extraction technique based on all-phase FFT (apFFT) is proposed to deal with SMI signals to suppress the influence of spectrum leakage and signal noise. Related mathematical derivation shows the advantages of the apFFT, then the simulation analysis indicates that the relative frequency errors can be evaluated to be lower than 103 even under the signal-to-noise ratio (SNR) of 5 dB. While in the experiments, the corresponding distance resolution is about 30 µm in the range examined. Additionally, the discussions of several influencing factors are included. The method proposed is effective in detecting target distance and can provide an interesting and attractive technical route for SMI distance measurement.



中文翻译:

自混合干涉测量中基于全相位FFT的距离测量

如激光自混合干涉术(SMI)领域中众所周知的那样,线性注入电流调制下的商用激光二极管(LD)可以用作低成本的激光测距仪,其自混合信号的拍频与要测量的距离。因此,精确的频率提取成为该测量方案中的重要问题。为了获得更好的频率,进而获得更好的距离估计性能,提出了一种基于全相位FFT(apFFT)的频率提取新技术来处理SMI信号,以抑制频谱泄漏和信号噪声的影响。相关的数学推导显示了apFFT的优势,然后的仿真分析表明,相对频率误差可以评估为低于10-3即使在5 dB的信噪比(SNR)下也是如此。在实验中,相应的距离分辨率在所检查的范围内约为30 µm。此外,还包括对几个影响因素的讨论。所提出的方法可以有效地检测目标距离,并且可以为SMI距离测量提供有趣而诱人的技术路线。

更新日期:2021-03-21
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