光学在大型几何尺寸测量中的应用

介绍了几种光学原理在大型几何尺寸测量中的应用．讨论的内容包括：多波长、双波长合成波长绝对距离干涉测量；激光频率分裂干涉测量；线性调频绝对距离干涉测量；相位板激光准直；旋光激光准直；半导体激光动态定位等．文章介绍了测量系统的工作原理，并讨论了测量精度和应用前景     

光学频率梳基于光谱干涉实现绝对距离测量

详细分析了光学频率梳光谱干涉的原理, 建立了较全面的光谱干涉的数学模型, 为实现绝对距离测量提供理论分析基础. 基于光谱干涉, 指出通过光谱干涉条纹的振荡频率, 即一次傅里叶变换, 可以实现绝对距离测量, 数值模拟结果表明, 最大测量误差为1.5 nm; 提出了一种等效的多波长并行零差干涉的方法, 分析了多波长并行零差干涉法的测距原理. 数值模拟结果表明, 多波长并行零差干涉法的最大误差为8.7 nm; 通过脉冲啁啾实现绝对测距, 分析了基于脉冲啁啾实现绝对测距的原理, 数值模拟结果表明, 最大测距误差为5.3 nm.     

基于光纤三波长激光自混合干涉的绝对距离测量系统

研究了一种基于光纤三波长激光自混合干涉的绝对距离测量系统.系统中的光纤激光器包含三个独立的激光谐振腔,每个激光谐振腔都有作为增益介质的掺铒光纤,三个激光谐振腔利用光纤光栅作为反射镜及波长选择元件,光纤激光器能同时发出无模竞争的频率和功率都稳定的三波长激光.利用三波长激光的自混合干涉,以及干涉信号的相位小数重合方法,实现绝对距离测量.为实现绝对距离测量,三个波长中两相邻波长间距应为相等.实验中,两相邻波长间距约为10nm.系统对公称高度为11mm修正值不大于2.7μm的台阶高度进行测量,测量结果为11.000 059mm.对13.000 090mm绝对距离重复测量20次的标准差为4.4nm.     

用117μm合成波长实现绝对距离干涉测量

根据以前双纵模绝对距离测量中合成波长过大导致误差较大的缺点,设计了一种新型多波长绝对距离干涉测量系统。采用633 nm双纵模He-Ne激光器中的一个纵模和629 nm波长的He-Ne激光组成117μm合成波长,使用双外差干涉技术对距离改变进行精密测量。静态稳定度和动态测量实验表明,由于采用了较小的合成波长,系统的测量不确定度可以达到3.8×10-6L+57 nm,在500 mm的距离上不确定度小于2μm。最后从合成波长不确定性的角度,对干涉系统中的误差作了分析。该系统如能与双纵模拍波测量作衔接则可实现对被测距离由粗至精的测量。     

基于飞秒光梳多路同步锁相的多波长干涉实时绝对测距及其非模糊度量程分析

飞秒光梳被广泛用于时间频率技术和精密光谱测量,由其时频特性所衍生的绝对测距技术以可溯源、大尺寸、高精度等优点有望成为未来长度计量的最重要手段.本文提出了一种基于飞秒光梳多路同步锁相的多波长干涉实时绝对测距方法,使多个连续波激光器通过光学锁相环技术同步锁定到飞秒光梳梳模上,通过多路同步相位测量和小数重合算法最终实现绝对距离测量.所提测量方法不仅能保留传统激光干涉测距的高分辨力和精度,而且可溯源至时间频率基准,对高精度长度测量、尤其是对物理复现“米”的定义具有重要计量意义.测距实验证明,四波长干涉测距的非模糊度量程达到44.6 mm,折射率波动导致非模糊度量程变化为纳米量级;多波长干涉测距的非模糊度量程也受制于空气折射率的测量误差,多波长干涉绝对测距的非模糊度量程在实验室环境下可达数米、甚至几十米,并通过2米线性位移实验证明了多波长绝对测距的大量程和线性测量性能.     

频率扫描干涉法绝对测距中运动误差的补偿研究

在频率扫描干涉法绝对距离测量过程中,目标的运动会对测量结果引入误差,经推导发现运动误差与激光扫频终点频率以及扪频过程中的光程差位移量有关.前者可直接通过高精度波长计测量,对于后者,提出了外差干涉频分复用技术,设计了一种新的频率扫描距离测量干涉仪,可同时实现目标绝对距离和光程差位移量的测量,通过剔除与扫频终点频率和光程差...     

一种新型多波长绝对距离干涉测量系统的研究

介绍了一种新型多波长绝对距离干涉测量系统。系统采用633nm的双纵模He-Ne激光器和629nm的He-Ne激光器,组成三级合成波长链对较大距离进行精密测量,并作了误差分析。系统采用高稳定度的声光晶体对各波长分别进行偏频,再用外差探测法测量出光束通过参考光路和测量光路后的位相差。简要介绍了629nm的He-Ne激光器的设计方案。     

具有位移和绝对距离测量能力的回馈干涉系统

提出一种基于半导体激光器泵浦Nd∶YAG微片激光器的回馈干涉系统，适合于非配合目标的位移和绝对距离测量。该测量系统包括移频回馈干涉光学系统，基于泵浦调制的微片激光器调频系统和相敏检波信号处理系统3部分。介绍了移频回馈干涉的原理，给出了位移测量和绝对距离测量应用的原理和测量方法，分析了测量的分辨率。实际测量了发黑工件表面的位移和绝对距离。实验结果表明，该回馈干涉系统灵敏度高，对被测表面反射率的要求很低，兼有对非配合目标的高分辨率位移测量和绝对距离测量的能力。     

用于绝对距离测量的波长扫描干涉仪信号分析

提出了一种可用于绝对距离测量的波长扫描光纤干涉仪。在时域和频域上，对其输出信号进行了研究。理论分析了法布里－珀罗腔多光束干涉所产生的干扰以及扫描过程中波长的随机漂移对输出信噪比的影响。由此提出了外腔光源结构和加工精度的要求，并设计了相应的信号处理算法，达到了距离测量所要求的０．０５μｍ的精度和０．０１μｍ的分辨率     

光梳多波长绝对测距的波长选择及非模糊度量程分析

飞秒光学频率梳作为精密光学频率标尺,可以用来产生频率稳定度极高的单波长连续激光,利用其多个梳模制备理想的多波长光源用于绝对距离测量具有测量速度快、实时性强、非模糊度量程大、精度高等优点。以多波长测距的基本理论和光梳高频率稳定度为基础,提出了二次合成波长的方法,不仅扩展了非模糊度量程,同时为干涉信号的多波长解调创造了足够的波长间隔条件。结合光梳的波长特点,分析了基于光梳的多波长选择与非模糊度量程的关系,并阐述了具体的选择步骤及波长组合结构。利用小数重合解调算法,在0.01的小数相位测量精度条件下,仿真验证了四波长干涉测距的非模糊度量程为35.636mm,五波长干涉系统可以达到几百毫米的非模糊度量程,后者相对分辨力的动态量程达到109量级。     

光纤超外差干涉测量系统的研究

提出了一种用于绝对距离测量的光纤超外差干涉系统,简述了该方案的原理,给出了信号处理的框图,并进行了初步实验。对系统的误差分析表明,在光强较弱、信噪比差的情况下,光学元件的非理想特性以及测量信号与参考信号之间的耦合是引起测量误差的主要原因。     

Frequency-comb-referenced two-wavelength source for absolute distance measurement

We propose a new tunable laser source concept for multiple-wavelength interferometry, offering an unprecedented large choice of synthetic wavelengths with a relative uncertainty better than 10(-11) in vacuum. Two lasers are frequency stabilized over a wide range of frequency intervals defined by the frequency comb generated by a mode-locked fiber laser. In addition, we present experimental results demonstrating the generation of a 90 mum synthetic wavelength calibrated with an accuracy better than 0.2 parts in 10(6). With this synthetic wavelength we can resolve one optical wavelength, which opens the way to absolute distance measurement with nanometer accuracy.     

基于合成波长法的飞秒激光外差干涉测距方法

本文提出了一种基于合成波长法的飞秒激光外差干涉测距方法.系统采用两个带通滤波器产生两个具有一定波长差的单波长,用于产生合成波长.本方法结构简单,能量利用率高.与双频激光干涉仪在40 mm范围内的比对结果表明,该方法比对残差的标准差为91 nm.     

Alternative method of wavelength drift free dual-wavelength heterodyne interferometry for the absolute distance measurement

Based on the technique of dual-wavelength and principle of heterodyne interferometry, a modified method for measuring the absolute distance is proposed. Because two test lights suffer from the same influence of wavelength drift in the measurement setup, the minus effect coming from the wavelength drift can be offset. Therefore, the measurement accuracy can be significantly increased. The feasibility of this method was demonstrated with a measurement resolution of about 1.50 μm. This method provides the advantages of a simple optical setup, easy operation and rapid measurement.     

U-shaped optical fiber sensor based on multiple total internal reflections in heterodyne interferometry

In this paper, an optical fiber sensor based on multiple total internal reflections (MTIRs) in heterodyne interferometry is proposed. With the optical fiber sensor the phase shift difference due to the multiple total internal reflections effect between the p- and s-polarizations is measured by using heterodyne interferometry. Substituting the phase shift difference into Fresnel's equations, the refractive index for the tested medium can be calculated. The resolution of the sensor can reach 1.6×10^?6 refractive index unit (RIU). The optical fiber sensor could be valuable for chemical, biological and biochemical sensing. It has some merits, such as, high resolution and stability, high sensitivity, high resolution and real-time measurement.     

Method of making mosaic gratings by using a two-color heterodyne interferometer containing a reference grating

We propose and demonstrate a two-color heterodyne interferometric method for making a perfect mosaic of two planar gratings that can substitute for a single and larger grating without introducing wavefront aberration at any wavelength. The lateral and longitudinal phase errors are separated and eliminated by use of two wavelengths in the interferometry. The accuracy of the phase difference measurement is improved by this heterodyne scheme. The method ensures that the lateral gap between the two subaperture gratings is an integer multiple of the grating period. For a pair of 0.72 microm period gratings we experimentally achieved a lateral alignment error of less than 1% of the grating period.     

High contrast linking six lasers to a 1 GHz Yb:fiber laser frequency comb

We demonstrate a 0.95 GHz repetition rate fully stabilized Yb:fiber frequency comb without optical amplification. Benefitting from the high mode power and high coherence, this comb achieved 35 to 42 dB signal to noise ratio on the direct heterodyne beat signals with at least six continuous wave lasers(at 580, 679, 698, 707, 813, and922 nm) while keeping 40 dB carrier envelope frequency signal. It can be used for the direct measurement of optical frequencies at visible and near-infrared wavelengths and has great potential on simultaneous comparison of multiple optical frequencies.     

台阶高度测量方法研究现状及进展

台阶高度测量是目前新提出的国际计量比对项目之一,当前的趋势是向纳米量级精度发展并尽量扩大测量范围。在分析现状和背景的基础上,大致归类了测量台阶高度的几种光学方法,着重介绍了其中绝对干涉方案的最新进展,从测量原理、测量精度以及量程等几方面比较了它们的优缺点。在此基础上提出以可调谐半导体激光器作为光源,采用可调合成波长链法实现纳米级精度毫米级量程的台阶高度测量,详细分析了方案的原理误差,得到最后的结论。     

Detection Schemes for Optical-Coherence-Domain Imaging of Biological Tissues

Optical coherence tomography (OCT) is a novel imaging modality based on low-coherence interferometry. This paper summarizes some of our latest work on the development of OCT where we have taken two approaches. In the first approach we have developed a phase-drift-suppression method for stable heterodyne detection in the presence of phase fluctuations. In the second approach we have concentrated on the development of two-dimensional heterodyne detection techniques for real-time imaging. A novel detection scheme has been proposed, which enables parallel heterodyne detection with a commercially available imager such as a charge-coupled-device camera. Meanwhile, a non-scanning OCT system configuration based on off-axis interferometry is being studied. Using a newly developed angular-dispersion imaging scheme, we show that the axial reflectance profile in OCT measurement can be detected instantaneously with a sensor array.