描述了利用低相干干涉技术实现光学镜面间距测量的方法。首先，采用微机电系统(MEMS)光开关多通道延迟结构实现测量范围的多倍增，然后通过共光路激光测距结构实现扫描反射镜的位移测量，再利用包络提取算法对低相干干涉信号的零光程差位置进行定位，最后实现镜面间距的高精度测量。实验测量系统为全光纤结构，利用该系统完成了对因瓦合金（Invar）标准块、大间距光学结构和光学镜组的镜面间距测量，在导轨扫描量程为300 mm的条件下，实现了在0.02~550 mm范围内的镜面间距测量，测量精度优于0.5 μm。该套系统可用于光刻机曝光系统、航测镜头、激光谐振腔等高性能精密光学系统的装调与检测。

The distance measurement of optical mirror surfaces based on low coherence interferometry is described. The system realizes lens surface distance measurement with high precision, by first using double micro-electromechanical systems (MEMS) switches to multiply enlarge the measuring range, secondly by using co-light-path laser ranging structure to realize the displacement measurement of the scanning mirror, and thirdly by using the envelope extraction algorithm to obtain the zero light path difference location of low coherence light interference signal. The whole measurement system has an all-fiber structure. Lens surface distances of Invar gauge, optical system with large air gap and optical lens group are measured with this system. Under the condition of the scanning range of 300 mm, distance measurement within the range of 0.02~550 mm by using MEMS switches is realized, and the experimental results indicate that the system possesses high measurement accuracy below 0.5 μm.Such a measurement system has important applications in optical testing and optical alignment of high precision optical systems, such as lithography exposure system, aerial camera, and laser resonator.