一、前言自一九六○年气体激光出现以来,激光技术得到不断发展,激光波长已作为长度计量的标准。单频和双频激光干涉仪相继问世。双频激光干涉仪由于克服了单频激光干涉仪的某些不足,具有可测距离大,测量速度高,抗干扰能力强等优点,特别适合在生产现场广泛使用。对大型机床、精密机械、船舶和飞机制造以及大地测量、地震预报等发展都有一定的促进作用。目前,双频激光干涉仪这一产品,在国际上只有美国、日本和法国等少数国家生产。七十年代以来,我国的一些单位也进行过研制,但都没有正式 I. Introduction Since the emergence of gas lasers in 1960, laser technology has been continuously developed. The laser wavelength has been used as a measure of length. Single-frequency and dual-frequency laser interferometers have come out. Dual-frequency laser interferometer due to overcome the single-frequency laser interferometer of some deficiencies, with measurable distance, high measurement speed, anti-interference ability and other advantages, especially suitable for use in the production site. For large machine tools, precision machinery, ship and aircraft manufacturing and geodesy, earthquake prediction and other development have a certain role in promoting. At present, dual-frequency laser interferometer this product, only the United States, Japan and France and a few countries in the world. Since the 1970s, some units in our country have also been developed, but none have been formalized