半导体激光端点干涉测长法原理探讨

阐述利用半导体激光的频率变化和波长变化测量干涉仪光程差的基本原理，探讨一种在长度的两个端点干涉测量长度的新方法，即端点干涉测长法的原理，推导这种方法测量长度的公式，指出这种方法区别于其它干涉测长方法的独特优点，最后讨论测量中的注意事项以及需要深入研究的问题。     

半导体激光端点干涉长法原理探讨

阐述利用半导体激光的频率变化和波长变化测量干涉仪光程差的基本原理，探讨一种在长度的两个端点干涉测量长度的新方法，即端点干涉测长法的原理，推导这种方法测量长度的公式，指出这种方法区别二其它干涉测长方法的独特优点，最后讨论测量中的注意事项以及需要深入的研究的问题。     

双纵模He-Ne激光单模干涉在大尺寸测量中的研究

采用双纵模热稳频He-Ne激光作为光源,其拍波波长作为测量大尺寸的基准,可实现大尺寸零件的精密测量.在前期研究的基础上利用其两个单模干涉实现整数倍拍波波长被测长度的确定,解决了该段长度测量精度难题,并利用激光单模干涉实现不足一个拍波波长长度的测量.该方法可实现对大尺寸工件几何尺寸的现场测量,并具有较高的精度.     

光学倍乘干涉原理在大长度测量中的应用

用激光单频干涉条纹计数方法测量长度需要设置相应长度的导轨和具备适宜的测试环境。这里介绍的光学倍乘干涉原理是一种不需要长导轨的大长度测长技术。对测试环境要求不严,适宜在室外进行测量。这种方法可作为室外校验24m 因瓦(Invar)基线尺长光电测距仪,直接测试地壳微量变形及特种工程安装测试等的手段。     

浅谈激光计米器

一、激光计米器的原理 激光计米器用双光线的激光多普勒干涉测量技术,实现非接触式长度测量.激光源发射出的激光通过光束分离器产生两束光在被测物体表面产生明暗相间的干涉条纹,光检测器通过回收激光检测到干涉条纹的变化,输出相应的电信号.被测物体移动,光检测器获得信号,测出被测物体的速度,并精确计算出通过测量区域的该物体的长度.     

激光自混频干涉法测量表面粗糙度的理论分析

设计了一种半导体激光自混频干涉法测量表面粗糙度的实验，对半导体激光自混频干涉法测量表面粗糙度中的干涉效应进行了理论分析，推导了干涉信号与表面粗糙度的数学关系式，讨论了影响测量信号的因素。实验结果表明，随着加工表面粗糙度的降低，反射光的强度逐渐增加，被测物体表面的反射率越高，越有利于测量。     

外腔半导体激光器大长度绝对测量

在线性调频激光绝对测长技术中采用平面镜外腔半导体激光器，实现了在无导轨条件下的大长度绝对测量，测量范围达到１０米，测量不确定度为１０＾－４。     

调频激光干涉绝对距离测量技术及其信号处理

最最的绝对距离测量方法是非相干飞行时间测量法。随后，在小数重合法的基础上，产生了多波长干波绝对距离测量技术。随着半导体激光器的发展，８０年代又出现了调频干涉绝对距离测量方法，并很快成为一种新的测长技术。本文在综述绝对距离技术及方法的基础上，着重介绍了调频激光干涉绝对距离测量技术的一些新发展及其几种不同的信号处理。     

2 m激光干涉测长基准装置

阐述了2 m激光干涉测长基准装置工作原理及系统组成,以线间距测量功能为基础,研究了接触式和非接触式的几何测长对准方法,实现了其测长功能拓展应用。介绍了实现纳米精度测长的技术措施。对称布局的双光电显微镜同步扫描测量接长的方式实现2 m刻线间距测量,信号处理系统具有标准间距位置脉冲发生功能,可以实现位移传感器动态触发校准和其它应用。对于高质量的线纹尺,2 m激光干涉测长基准装置单次测量刻线间距的最佳瞄准精度优于10 nm(1σ),1 m测量范围内的线纹测量不确定度U=（20+40 L） nm （k=2）。     

2m比长仪纳米级精度线间距测量系统的研究

介绍了2 m比长仪系统的组成,对其采用光电显微镜动态瞄准刻线和激光干涉测长原理进行了分析,研究了提高刻线瞄准精度和激光干涉测长精度的方法及利用现代电子技术实现刻线信号和干涉信号自动同步快速处理方法。自动信号处理系统基于FPGA现场可编程电路技术和计算机技术。通过对金属线纹尺测量的实验表明,依据JJG 331—1994激光干涉比长仪检定规程进行实验,2 m比长仪单次最佳刻线瞄准精度优于10 nm(1σ),对其测量的不确定度分析表明,对于测量高质量的高等别线纹尺,其测量不确定度U=（20+40 L）nm（k=2）。     

Fringe pattern analysis with a parametric method for measurement of absolute distance by a frequency-modulated continuous optical wave technique

Interferometry associated with an external cavity laser of long coherence length and broad wavelength tuning range shows promising features for use in measurement of absolute distance. As far as we know, the processing of the interferometric signals has until now been performed by Fourier analysis or fringe counting. Here we report on the use of an autoregressive model to determine fringe pattern frequencies. This concept was applied to an interferometric device fed by a continuously tunable external-cavity laser diode operating at a central wavelength near 1.5 microm. A standard uncertainty of 4 x 10(-5) without averaging at a distance of 4.7 m was obtained.     

Distance and velocity measurements by the use of an orthogonal Michelson interferometer

A novel signal processing scheme for detecting distance and velocity signals simultaneously is demonstrated. In this method, a frequency-modulated diode laser is used to illuminate a dual-channel Michelson interferometer with two orthogonal output signals. The distance and the velocity signals then exist on the beat frequencies of the output interferometric signal. Two interferometric output signals with a quadrature phase shift are used to adjust the gating time period of frequency counters for beat-frequency measurement. The distance and velocity signals can thus be obtained from the counting number within the gated-in time period.     

Measurement of absolute distance employing a tunable CW dye laser

With a tunable CW dye laser oscillating in a single longitudinal mode, measurement of an absolute distance is demonstrated with the method of excess fractions. Five beams which have different wavelengths are emitted sequentially from the dye laser, and the interferometric phase is measured for each wavelength. An interferometric order number for a wavelength can be calculated from values of wavelengths and phases. Then a precise value of length is obtained. This method is similar to measuring distances by using group delay as used in VLBI and microwave ranging. The measured accuracy was within ±8.8 nm between 0 and 10 mm (at an absolute distance of 0.1-10.1 mm)     

Interferometric ellipsometer with wavelength-modulated laser diode source

An interferometric ellipsometer, with no moving parts and an inexpensive laser diode source, is demonstrated. Temporal fringes are produced by a small modulation of the laser diode bias current and unbalanced arms in the interferometer. Fringe analysis algorithms are developed, and accurate measurements of the optical properties of a number of samples are made. Temperature tuning the laser diode center wavelength allows the frequency dependence of the optical properties to be determined over a wavelength range of approximately 1 nm.     

Intracavity iodine cell spectroscopy with an extended-cavity laserdiode around 633 nm

The purpose of the work described was to develop a tunable laser diode which is as easy to use as a He-Ne laser stabilized on iodine. The particularity of this experiment is the use of I₂ cell placed inside the extended cavity laser (ECL). The experimental set-up mounted takes the form of a lambdameter which gives the wavelength to one part in 10⁶, a Fabry-Perot (FP) interferometer for mode analysis and a beat-frequency measurement system. The FP interferometer has the particular feature of a second I₂ cell which makes it possible to detect the iodine transitions by simple visual inspection of an oscilloscope. Many transitions, some much more intense than the usual R(127)11-5 transition, are under study. We worked mainly on P(33) 6-3 since this is inside the range of our beat-frequency system. Results are promising: the free running relative frequency stability is about three parts in 10¹⁰ and the locked-laser relative frequency stability about three parts in 10¹¹ after 80 s. This is already good enough for use as a wavelength standard for length and for interferometric measurement     

Phase-stepped gauge block interferometry using a frequency-tunable visible laser diode

Frequency changes induced by bias or temperature modulation of injection diode lasers can provide an economical and effective method of applying phase-stepping interferometry to optical metrology. However, the intrinsic frequency instability of these devices limits their use in gauge block interferometry where precise and repeatable phase steps must be maintained simultaneously on two discontinuous surfaces and over relatively long path lengths. We demonstrate a method using a visible injection diode laser, the frequency of which is locked by using a Fabry-Perot interferometer. Small changes to the length of the Fabry-Perot interferometer shift the frequency of the laser producing proportional and repeatable phase steps to the gauge block interferogram. This method has been successfully implemented with a Fizeau-type gauge block interferometer with a phase measurement resolution of 0.005 lambda. The phase data are then processed to map the surface form of gauge blocks up to 100 mm in length and to objectively assess surface shape parameters.     

Measuring optical fiber length by use of a short-pulse optical fiber ring laser in a self-injection seeding scheme

A method for measuring the length of an optical fiber by use of an optical fiber ring laser pulse source is proposed and demonstrated. The key element of the optical fiber ring laser is a gain-switched Fabry-Perot laser diode operated in a self-injection seeding scheme. This method is especially suitable for measuring a medium or long fiber, and a resolution of 0.1 m is experimentally achieved. The measurement is implemented by accurately determining the pulse frequency that can maximize the output power of the fiber ring laser. The measurement results depend only on the refractive index of the fiber corresponding to this single wavelength, instead of the group index of the fiber, which represents a great advantage over both optical time-domain reflectometry and optical low-coherence reflectometry methods.     

Quantitative Analysis of Trace Moisture in N(2) and NH(3) Gases with Dual-Cell Near-Infrared Diode Laser Absorption Spectroscopy

This paper demonstrates our optical measurement system based on near-infrared tunable diode laser absorption spectrometry and reports the results of trace moisture determination in nitrogen and ammonia gases. A near-infrared InGaAsP distributed feedback diode laser operating at room temperature was employed as the optical source. We used a dual-cell detection strategy to cancel common mode noise from the diode laser and remove the effect of the residual moisture absorption in the beam path outside the sample cell. We also used this method to successfully eliminate the interfering absorption of matrix gas molecules such as NH(3). The detection limit of H(2)O absorption of 4 ppb in nitrogen and 12 ppb in ammonia was obtained using a single-pass absorption cell of only 92 cm in length and the average results of 10 scan measurements. This system has characteristics of both the high sensitivity and capability of in situ and real-time measurement.     

Measurement of absolute displacement by a double-modulation technique based on a Michelson interferometer

A novel method is presented for of measuring absolute displacement with a synthesized wavelength interferometer. The optical phase of the interferometer is simultaneously modulated with a frequency-modulated laser diode and optical path-length difference. The error signal originating from the intensity modulation of the source is eliminated by a signal processing circuit. In addition, a lock-in technique is used to demodulate the envelope of the interferometric signal. The displacement signal is derived by the self-mixing technique.     

频闪干涉仪在微机电系统动态表征中的应用

微机电系统(MEMS)测试的主要目的是为工程开发中的设计和模拟过程提供数据反馈，其中一个重要方面就是MEMS器件动态特性的高速可视化．介绍了一种基于计算机控制的频闪干涉测试系统，用来测量可动MEMS器件的离面运动，实现了纳米级分辨力，该系统采用改进的相移干涉算法，使用一个大功率激光二极管(LD)作为频闪照明的光源，可以实现1MHz范围内大幅值(十几微米)的微运动测量，这种高离面灵敏度的测量方法特别适合进行微机械(光学)元件的动态特性测量．通过研究一个多晶硅微谐振器的动态特性说明了系统的强大功能。