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1、6.1 6.1 激光激光激光激光(jgung)(jgung)干涉测长干涉测长干涉测长干涉测长第一页，共四十三页。激光激光(jgung)(jgung)干涉测长干涉测长n n干涉测量技术干涉测量技术(jsh)(jsh)是以光的干涉现象为基础进行测量的一门技术是以光的干涉现象为基础进行测量的一门技术(jsh)(jsh)6.1.1 干涉(gnsh)测长的基本原理u1.激光干涉测长的基本光路是一个迈克尔逊干涉仪,如图6-1示,用干涉条纹来反映被测量的信息。两束光的光程差可以表示为u2.被测长度与干涉条纹变化的次数和干涉仪所用光源波长之间的关系是u3.从测量方程出发可以对激光干涉测长系统进行基本误差分析图
2、6-1激光干涉测长仪的原理图第二页，共四十三页。6.1.2 6.1.2 激光干涉测长系统激光干涉测长系统(xt(xt ng)ng)的组成的组成1. 1. 除了迈克尔逊干涉仪以外，激光干涉测长系统还包括激光光源除了迈克尔逊干涉仪以外，激光干涉测长系统还包括激光光源(gungyun)(gungyun)，可移动平台，光电显微镜，光电计数，可移动平台，光电显微镜，光电计数器和显示记录装置。器和显示记录装置。 2.迈克尔逊干涉仪是激光干涉测长系统的核心部分，其分光器件、反射(fnsh)器件和总体布局有若干可能的选择3.干涉仪的分光器件原理可以分为分波阵面法、分振幅法和分偏振法。 偏振分光器(参见图6-6
3、中的B2)以及由晶轴正交的偏光棱镜组成如沃拉斯顿棱镜。 分振幅平行平板分光器和立方棱镜分光器4.干涉仪中常用的反射器件:平面反射器、角锥棱镜反射器（图6-2a）、直角棱镜反射器（图6-2b）、猫眼反射器（图6-2c）图6-2反射器第三页，共四十三页。6.1.2 6.1.2 激光干涉测长系统激光干涉测长系统(xt(xt ng)ng)的组成的组成n5.激光干涉仪的典型光路布局(bj)有使用角锥棱镜反射器的光路布局(bj)，如图6-3示。图6-3典型光路布局6.移相器也是干涉仪测量系统的重要(zhngyo)组成部分。常用的移相方法有机械移相（图6-4），翼形板移相，金属膜移相和偏振法移相。图6-4机
4、械法移相原理图第四页，共四十三页。6.1.2 激光干涉测长系统(xtng)的组成n n除了迈克尔孙干涉仪以外，激光干涉测长系统还包括除了迈克尔孙干涉仪以外，激光干涉测长系统还包括(boku)(boku)激光光源、可移激光光源、可移动平台、光电显微镜、光电计数器、显示记录装置动平台、光电显微镜、光电计数器、显示记录装置7.干涉条纹(tiown)计数时，通过移相获得两路相差/2的干涉条纹的光强信号，该信号经放大，整形，倒向及微分等处理,可以获得四个相位依次相差/2的脉冲信号（图6-5）。图6-5判向计数原理框图第五页，共四十三页。 激光干涉激光干涉(gnsh)(gnsh)测长仪的构成测长仪的构成n
5、 nAn accurate Michelson interferometer( the core part)An accurate Michelson interferometer( the core part)n nLaser source( Single-mode helium neon gas laser;Output Laser source( Single-mode helium neon gas laser;Output for 632.8 nm red wavelengths)for 632.8 nm red wavelengths)n nMobile platform( Alo
6、ng the direction of incident light Mobile platform( Along the direction of incident light translation)translation)n nPhotoelectric microscopePhotoelectric microscopen nPhotoelectric counterPhotoelectric countern nDisplay record device( Output measurement results, Display record device( Output measur
7、ement results, can be replaced by special computer or PC)can be replaced by special computer or PC)第六页，共四十三页。第七页，共四十三页。computerDetectormoduleHe-Ne Laser第八页，共四十三页。第九页，共四十三页。 第十页，共四十三页。第十一页，共四十三页。 A brief introduction about MichelsonA brief introduction about Michelson第十二页，共四十三页。Albert Abraham Michels
8、on(18521931) was born in what Albert Abraham Michelson(18521931) was born in what was then Germany (now Poland) and emigrated with his was then Germany (now Poland) and emigrated with his family to the United States in 1855.He became a family to the United States in 1855.He became a professor of phy
9、sics at the Case School of Applied professor of physics at the Case School of Applied Science (Cleveland, Ohio), then at Clark University( Science (Cleveland, Ohio), then at Clark University( Worcester, Massachusetts), and then at the University Worcester, Massachusetts), and then at the University
10、of Chicago. In 1907 he became the first American to of Chicago. In 1907 he became the first American to receive a Nober prize; the prize citation reads: receive a Nober prize; the prize citation reads: “ “For his For his optical precision instruments and the spectroscopic and optical precision instr
11、uments and the spectroscopic and meteorological investigations carried out with their aid.meteorological investigations carried out with their aid.” ”第十三页，共四十三页。 The Michelson interferometer is shown in Figure 1. The Michelson interferometer is shown in Figure 1. The basic optical path of laser inte
12、rferometer length measurement is a Michelson interferometer, and this The basic optical path of laser interferometer length measurement is a Michelson interferometer, and this makes use of interference fringes ,which are the traces of points owing the same path difference, to makes use of interferen
13、ce fringes ,which are the traces of points owing the same path difference, to reflect the information of measured object. It uses the partially reflecting element P to divide the light reflect the information of measured object. It uses the partially reflecting element P to divide the light from las
14、er source into two mutually coherent beams which are reflected by M1 and M2 .The output from laser source into two mutually coherent beams which are reflected by M1 and M2 .The output intensity of an interferometer is a periodic function of the length difference between the measuring path intensity
15、of an interferometer is a periodic function of the length difference between the measuring path and the reference path of the interferometer. Typical length measurements with a laser interferometer and the reference path of the interferometer. Typical length measurements with a laser interferometer
16、are performed by moving one reflector of the interferometer along a guideway and counting the are performed by moving one reflector of the interferometer along a guideway and counting the periodic interferometer signal, e.g. the interference fringes. These results are unambiguous as long as periodic interferometer signal, e.g. the interference fringes. These results are unambiguous as long as the length difference between two consecutive measurements is within the length difference between two c
