激光扫频干涉绝对距离测量关键技术研究

发布时间：2018-01-12 05:30

本文关键词：激光扫频干涉绝对距离测量关键技术研究　出处：《哈尔滨工业大学》2017年博士论文　论文类型：学位论文

【摘要】：随着航空航天、船舶、精密加工制造等技术的快速发展,对激光测距技术的需求越来越多,激光扫频干涉绝对距离测量技术具有非接触测量、无测距盲区、无需合作目标等优点,成为该领域的研究热点。激光扫频干涉绝对距离测量系统的测距精度随着激光器扫频范围的增大而提高。目前常用的半导体激光器由于调谐范围较小,测量精度难以进一步提高。宽带外腔调频激光器的出现使激光扫频干涉测量精度大幅度提高成为可能。然而也带来了新的问题,如外腔调谐激光器的调频非线性形式为高次函数,调频非线性校正比较困难;宽带调频所带来的色散失配效应导致测距精度下降;大带宽调频形成的大数据量的快速处理问题。这些问题成为限制宽带激光扫频干涉测量的重要因素。针对以上关键问题,本文对基于频率采样法宽带激光扫频干涉绝对距离测量技术进行了研究,主要研究内容如下:构建了宽带外腔激光扫频干涉测距系统,通过分析外腔激光器调频非线性的特点,建立了基于频率采样法的拍频信号非线性校正模型,实现了高次调频非线性校正。由于受奈奎斯特采样定理限制,频率采样法测距量程不能超过辅助干涉仪光程的1/4。为扩展量程,提出了移相频率采样法,将测量信号依辅助干涉仪信号相位尺度进行移相,使移相后的信号满足奈奎斯特采样定理,提高了频率采样法的适用范围,实验验证了其可进行7倍的量程扩展。研究了光纤辅助干涉仪与测量干涉仪色散失配对测距精度的影响,发现随着调频带宽与被测距离增加,色散失配效应导致测量信号拍频产生线性变化,导致目标谱峰展宽,产生测量误差。建立了辅助干涉仪与测量干涉仪色散失配的理论模型,为补偿色散失配对测量产生的影响,提出了基于色散啁啾斜率标定的色散补偿方法,有效降低了目标谱峰展宽效应,使色散补偿后的目标峰值半高全宽(FWHM)基本达到接近理论值的水平。采用外腔调谐激光器单次测量产生的数据量将随扫频带宽增加而增大,导致现有拍频提取算法效率下降。研究了测量信号拍频提取算法的特点,提出的拍频提取算法通过对测量信号进行移频、降采样,实现了大数据量信号的快速拍频提取。该算法精度与基于复解析带通滤波器的复调制细化谱分析(ZFFT)算法相同,但运算时间为ZFFT算法的27.4%。其次,从相位角度研究了线性回归测频方法,通过仿真验证了该算法在较高信噪比下具有高精度测频能力。研究了温度对辅助干涉仪的影响模型,采用模型参数补偿及光程修正的方法,降低了温度对测量的影响。最后,通过实验验证了在12m范围内激光扫频干涉绝对距离测量的扩展不确定度小于U=(7.6×10-6+2.8×10-6Rm)m(k=2)。
[Abstract]:With the rapid development of aerospace, ship, precision manufacturing and other technologies, laser ranging technology needs more and more, laser scanning interference absolute distance measurement technology has a non-contact measurement, no ranging blind area. No need for cooperation goals and other advantages. The ranging accuracy of the absolute range measurement system increases with the increase of the frequency sweep range of the laser. Currently, the semiconductor laser is widely used because of its small tuning range. It is difficult to improve the measurement accuracy further. The appearance of broadband external cavity FM laser makes it possible to improve the measurement accuracy of laser frequency sweep interferometry. However, it also brings new problems. If the nonlinear form of frequency modulation of external cavity tunable laser is high order function, it is difficult to correct the nonlinear frequency modulation. The dispersion mismatch effect caused by broadband frequency modulation results in the decrease of ranging accuracy. Fast processing of large amount of data due to large bandwidth frequency modulation. These problems have become an important factor to limit the wideband laser scanning interferometry. In view of the above key problems. In this paper, the absolute range measurement technology of wideband laser scanning interference based on frequency sampling method is studied. The main research contents are as follows: a wideband external cavity laser frequency sweep interferometric ranging system is constructed. By analyzing the nonlinear characteristics of frequency modulation of external cavity laser, a nonlinear correction model of beat frequency signal based on frequency sampling method is established, and the nonlinear correction of high order frequency modulation is realized, because of the limitation of Nyquist sampling theorem. The ranging range of frequency sampling method can not exceed 1 / 4 of the optical path of the auxiliary interferometer. In order to extend the measuring range, a phase shift frequency sampling method is proposed, in which the measurement signal is phase-shifted according to the phase scale of the auxiliary interferometer signal. The phase-shifted signal meets the Nyquist sampling theorem and improves the application range of the frequency sampling method. Experimental results show that the range can be extended by 7 times. The influence of optical fiber assisted interferometer and measurement interferometer color dispersion on ranging accuracy is studied. It is found that the range is increased with the increase of FM bandwidth and measured range. The dispersion mismatch effect leads to the linear change of the beat frequency of the measurement signal, the broadening of the target spectrum peak and the measurement error. The theoretical model of the dispersion mismatch between the auxiliary interferometer and the measurement interferometer is established. In order to compensate the effect of color dispersion on measurement, a dispersion compensation method based on dispersion chirped slope calibration is proposed, which can effectively reduce the peak broadening effect of target spectrum. The FWHM of the target peak value after dispersion compensation reaches the level close to the theoretical value. The amount of data generated by the single measurement of the external cavity tunable laser will increase with the increase of the sweep bandwidth. As a result, the efficiency of the existing beat extraction algorithm is reduced. The characteristics of the measurement signal beat extraction algorithm are studied, and the beat frequency extraction algorithm is proposed to reduce the sampling by moving the frequency of the measurement signal. The algorithm has the same precision as the ZFFT-based complex modulation thinning spectrum analysis algorithm based on complex analytic bandpass filter. However, the computing time is 27.4 of the ZFFT algorithm. Secondly, the linear regression frequency measurement method is studied from the angle of phase. The simulation results show that the algorithm has high precision frequency measurement ability under higher SNR. The influence model of temperature on the auxiliary interferometer is studied, and the method of model parameter compensation and optical path correction is adopted. The influence of temperature on the measurement is reduced. Finally. The experimental results show that the spread uncertainty of absolute range measurement is less than 7.6 脳 10-62.8 脳 10-6Rmmmknmmknmkng in the range of 12m for absolute range measurement of laser sweep interference.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN249

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