在干涉仪中由于用了相干性良好的氦氖激光光源,使参考光路与测试光路间的干涉程差允许大大增加,有的可达几十米。这种参考光路与测试光路间光程差很大的干涉仪通常称为不等臂干涉仪或不等程干涉仪。在以往的迈克尔逊型干涉仪中,使用普通光谱灯作光源。由于光源的干涉程长较短,一般为几十毫米,所以仪器实际工作时的参考光路与测试光路处于接近等光程的状态,这时准直系统即使由于视差、象差或其它原因而使出 In the interferometer due to the use of a good coherence HeNe laser light source, the reference optical path and the test optical path between the allowable difference greatly increased, and some up to tens of meters. This reference optical path and test optical path between the optical path difference is very large interferometer is often called unequal-arm interferometer or unequal-range interferometer. In the past Michelson interferometer, the use of ordinary light as a light source. Since the interference length of the light source is short and generally several tens of millimeters, the reference light path and the test light path in the actual working of the instrument are in a state close to the optical path. In this case, even if the collimation system is caused by parallax, aberration or other reasons Out