针对光学薄膜厚度测量困难问题，提出了一种基于激光外差干涉术的薄膜厚度测量方法。采用经典迈克尔逊干涉光路，利用外差干涉原理将薄膜厚度差转换为光程差，以精密位移平台为扫描机构实现薄膜厚度的逐行扫描测量。测量系统在恒温实验条件下20 min内的漂移不超过8 nm，测量结果平均差小于1 nm，通过与椭圆偏振仪的测量结果比较，测量差值为12.97 nm，表明了该方法的可行性。

For the difficulty of measuring the thin film thickness, a method of thin film thickness measurement based on laser heterodyne interferometry was proposed. Using the classical Michelson interference optical path, the heterodyne interference principle was used to convert the film thickness difference into the optical path difference, and the precise displacement table was used as the scanning mechanism to realize the progressive scanning measurement of the film thickness. Results show that the shift of the measurement system within 20 min under constant temperature experimental conditions does not exceed 8 nm, and the average deviation of the measurement results is less than 1 nm. Comparing with the measurement results of the ellipsometer, the measurement difference is 12.97 nm, indicating the feasibility of the method.