基于飞秒激光光学频率梳的大尺寸绝对测距方法研究

发布时间：2018-05-29 12:35

  本文选题：飞秒光梳 + 多波长　； 参考：《国防科学技术大学》2015年博士论文

【摘要】：激光以其单色性和相干性好、方向性强等优点,被广泛用于精密工程与测量领域。激光测距技术是目前动态量程最大、精度最高的长度和距离测量手段,在工业生产、装备制造、国防科技和航空航天等领域发挥着至关重要的作用。随着现代工业对大尺寸精密测量和定位技术需求的不断提升,传统的激光非相干和相干测距方法已经难以满足大尺寸高精度距离测量的需求。飞秒激光光学频率梳作为本世纪初最伟大的物理学贡献之一,不仅实现了光学频率和微波频率的对接,而且带来了距离测量技术和长度计量实现手段的革新,其通过在传统激光脉冲测距中引入光学相干技术,将非相干和相干测量完美地融合在一起,创新性地解决了大距离和高精度的突出矛盾,为实现大尺寸高精度激光绝对测距提供了诸多新方法和新技术。论文以实现大尺寸高精度实时绝对距离测量为任务,开展利用飞秒光梳时频特性来实现绝对测距的理论和方法研究,特别是围绕基于飞秒光梳同步锁频的多波长干涉实时绝对测距方法进行了系统的深入研究。论文的主要工作总结如下:1、提出了一种双飞秒光梳多外差绝对测距方法。结合双光梳互相关多外差测量和梳间拍频测量,构建微波合成波长链,不需要扫描重复频率便可在km量程内实现理论精度为亚微米量级的绝对测距;建立了该方法的测距理论模型,并仿真验证了该方法用于开展大尺寸高精度绝对测距的可行性;利用飞秒脉冲的强度互相关特性建立了扫描重复频率的互相关空间绝对测距模型,对现有的光梳时域互相关测距方法进行了改进,并通过建模与仿真分析证明了其可行性。2、提出了基于飞秒光梳同步锁频的多波长干涉实时绝对测距方法。针对传统多波长干涉光源难以制备以及使用波长扫描干涉难以满足实时测量需求等大尺寸绝对测距问题,从飞秒光梳的精密频率尺特性出发,本文提出了基于飞秒光梳同步锁频的多波长干涉实时绝对测距方法。该方法以飞秒光梳作为激光频率参考源,利用光学锁相技术同时产生多路波长相异、频率稳定度高的单波长激光来进行干涉测量,并通过多波长干涉相位的同步探测和小数重合算法拓展实时测距的非模糊度量程,测量结果不仅能保留单波长激光干涉测量的分辨力和精度,而且可溯源至微波频率基准,对复现“米”的定义和长度计量具有重要意义。3、提出了二次等效合成波长拓展测距非模糊度的方法。针对多波长干涉中仅靠一次等效合成波长难以满足大尺寸绝对测距中波长解调的问题,本文提出了二次等效合成波长的方法,通过两个一次等效合成波长的再次合成克服了波长间隔的限制;在此基础上,还深入研究了多波长干涉测距解调算法、波长选择和非模糊度量程等问题,并仿真验证了基于飞秒光梳同步锁频的四波长干涉非模糊度量程一般能达到36 mm,五波长干涉能达到米量级。4、围绕产生高频率稳定度的多波长激光光源,在光纤飞秒脉冲激光光源基础上,利用光学倍频、f-2f自参考干涉和锁相技术实现了重复频率和载波包络频移的锁定,使用Allan方差表征的相对频率稳定度分别达到1.1×10-12和5.1×10-15,实现了飞秒光梳的制备;在所搭建的飞秒光梳频率参考源基础上,利用光学锁相技术将多个可调谐单波长激光同时锁频到不同的光梳梳模上,得到了相对锁频稳定度为1.9×10-15的连续波输出,实现了高频率稳定度的多波长光学频率发生器装置;针对所提多波长干涉法实现多路同步干涉测量的需求,研制了多波长外差干涉仪光路和多路同步相位解调模块,实现了多波长测距系统的无混叠干涉、波长解调和小数相位精度优于0.001(相对弧度制相位2π)的同步相位测量;研制了实时绝对测距算法及软件,提高了小数重合法计算整数相位的效率,实现了更新速率为10 ms的连续测量,较好地满足了实时绝对测距的需求。5、搭建了基于飞秒光梳同步锁频的多波长干涉绝对测距系统及其实验平台,并利用频率扫描法实现了mm精度的初始绝对距离值的粗测。在此基础上,进行了非模糊度量程验证实验和线性位移对比试验。通过与双频激光干涉仪测量结果对比,证明了四波长干涉非模糊度量程达到44.6 mm,且1m线性位移内测量残余误差的P.V值为61.9 nm,相对测距精度达到了10-8量级,证明了所搭建的多波长干涉绝对测距系统开展大尺寸纳米精度距离测量的可行性。6、提出了结合微波合成波长和多波长干涉进一步拓展非模糊度量程的方法。针对五波长干涉中使用二次等效合成波长拓展非模糊度量程的有限性,提出在四波长干涉基础上融合微波合成波长测距的思想,大大提高了合成波长链拓展测距量程的效率。在所提方法基础上,开展了3m大量程的线性位移对比测量实验,与参考位移值的拟合残差的P.V值为35.3 nm;同时,开展了抗光路中断实时绝对测距实验、短时测量性能对比试验和24h长时测距性能对比实验,从抗光路扰断、测量分辨力、短时精度、长时间稳定性和防死区光程误差等方面展现了多波长绝对测距系统的良好测量性能及其应用潜力;对多波长干涉绝对测距的测量不确定度进行了分析和总结,并围绕空气折射率变化对准确判断整数相位的影响及其与多波长干涉测距量程之间的关系进行了探讨。
[Abstract]:Laser is widely used in the field of precision engineering and measurement for its advantages of good monochromability, good coherence and strong direction. Laser ranging is the largest and most accurate measure of length and distance in the dynamic range. It plays a vital role in the fields of industrial production, equipment manufacturing, national defense science and technology and aerospace. The demand for large size precision measurement and positioning technology has been improved in industry. Traditional laser incoherent and coherent distance measurement methods have been difficult to meet the needs of large size and high-precision distance measurement. The femtosecond laser optical frequency comb is one of the greatest physical contributions in the beginning of this century, which not only realizes the pair of optical frequency and microwave frequency. In addition, it brings the innovation of distance measurement and length measurement. Through the introduction of optical coherence technology in the traditional laser pulse distance measurement, it combines the noncoherent and coherent measurement perfectly. It innovatively solves the prominent contradiction between the large distance and the high precision, and provides the large size and high precision laser absolute distance measurement. In order to realize the real time absolute distance measurement with large size and high precision as the task, the theory and method of the absolute distance measurement using the time frequency characteristics of the femtosecond comb are carried out, especially the system of the multi wavelength interference real-time absolute distance measurement based on the femtosecond comb synchronous locking. The main work of this paper is summarized as follows: 1, a method of multi heterodyne absolute distance measurement for two femtosecond combs is proposed. Combining the cross correlation multi heterodyne measurement and beat frequency measurement, the microwave synthesis wavelength chain is constructed, and the absolute distance of the theoretical degree of sub micron can be realized within the km range without the need of scanning repetition frequency. The distance measurement model of the method is used to verify the feasibility of the method for large size and high precision absolute distance measurement. Using the intensity cross correlation characteristic of the femtosecond pulse, the absolute distance measurement model of the cross correlation space of the scanning repetition frequency is established, and the existing method of the cross correlation distance measurement of the current comb is improved and the modeling and simulation are made. The analysis proves its feasibility.2, and proposes a multi wavelength interferometric real-time absolute distance measurement method based on the femtosecond comb synchronous locking frequency. It is difficult to prepare the traditional multi wavelength interference light source and use the wavelength scanning interference to meet the real time measurement requirement. In this paper, a multi wavelength interferometric real-time absolute distance measurement method based on femtosecond comb synchronous locking is proposed. This method uses femtosecond comb as the reference source of the laser frequency, and produces a single wavelength laser with multi wavelength different wavelengths and high frequency stability by using optical phase locking technique. The small number coincidence algorithm extends the non fuzzy range of real-time distance measurement. The measurement results not only retain the resolution and accuracy of the single wavelength laser interferometry, but also be traced to the microwave frequency reference. It is of great significance to the definition and length measurement of the reiterative "rice".3. The two times of the equivalent synthetic wavelengths to extend the non ambiguity of distance measurement are proposed. Method. Aiming at the problem that only one equivalent synthetic wavelength in multi wavelength interference is difficult to satisfy the problem of wavelength demodulation in large size absolute distance measurement, this paper proposes a method of two equivalent synthetic wavelengths, which overcomes the limitation of wavelength interval through the resynthesis of two first equivalent synthetic wavelengths, and on this basis, the multi wavelength interferometry is also studied. From the demodulation algorithm, the wavelength selection and the non ambiguity range, the simulation shows that the four wavelength interference non ambiguity range based on the femtosecond comb synchronous locking frequency can reach 36 mm, the five wavelength interference can reach the meter.4, and the multi wavelength light source with high frequency stability is based on the fiber femtosecond laser light source. By using optical frequency doubling, f-2f self reference interference and phase locked technique have realized the locking of repetition frequency and carrier envelope frequency shift. The relative frequency stability characterized by Allan variance is 1.1 * 10-12 and 5.1 * 10-15 respectively. The preparation of femtosecond combs is realized. Multiple tunable single wavelength lasers are locked to different comb modes at the same time, and the frequency lock stability is 1.9 * 10-15 continuous wave output, and a multi wavelength optical frequency generator with high frequency stability is realized. The multi wavelength heterodyne interferometry is developed for the multi wavelength interference measurement for the multi wavelength interference method. The optical path and the multi-channel synchronous phase demodulation module have realized the non aliasing interference of the multi wavelength range finding system. The wavelength demodulation and the fractional phase precision are better than 0.001 (relative radian phase 2 pi). The real-time absolute distance measurement algorithm and software are developed, which improves the efficiency of the integer phase and realizes the update speed. The continuous measurement of 10 ms has satisfactorily satisfied the requirement of real time absolute distance measurement, and set up a multi wavelength interferometric absolute distance measuring system based on femtosecond comb synchronous locking and its experimental platform. The initial absolute distance of MM precision is measured by frequency scanning. On this basis, a non fuzzy range verification experiment is carried out. Compared with the linear displacement contrast test, by comparison with the measurement results of double frequency laser interferometer, it is proved that the four wavelength interference non ambiguity range reaches 44.6 mm, and the P.V value of the residual error in the 1m linear displacement measurement is 61.9 nm, and the relative distance precision reaches 10-8 order of magnitude. The feasibility of nanometer precision distance measurement.6 is proposed. A method is proposed to further expand the non fuzzy range with microwave synthetic wavelength and multi wavelength interference. Aiming at the limitation of using two equivalent synthetic wavelengths to extend the non fuzzy range in the five wavelength interference, the idea of combining microwave synthesis wavelength ranging on the basis of four wavelength interferometry is proposed. On the basis of the proposed method, the linear displacement contrast measurement experiment of 3M is carried out on the basis of the proposed method. The P.V value of the fitting residual of the reference displacement value is 35.3 nm. At the same time, the real time absolute distance measurement experiment, the short time measurement performance comparison test and the long time range finder of the 24h are carried out. The comparison experiment shows the good measurement performance and the application potential of the multi wavelength absolute distance measuring system from the anti optical path disturbance, the measurement resolution, the short-time precision, the long time stability and the light path error of the dead zone. The measurement uncertainty of the multi wavelength interferometric absolute distance measurement is analyzed and summarized, and the change of the refractive index of the air is around. The relationship between the integer phase and the range of multi wavelength interferometry is discussed.
【学位授予单位】：国防科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN24
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本文编号：1950896