基于FFT的薄膜厚度干涉测量新方法

在研究二维FFT法进行干涉测试基本原理的基础上，提出一种基于二维FFT的薄膜厚度测量新方法。利用搭建的泰曼-格林型干涉系统，用CCD接收、采集卡采集，可获得被测膜层的干涉条纹图像。编制算法处理软件，可实现对干涉条纹图中薄膜边缘识别、区域延拓、滤波、波面统一等的处理，从而获得带有薄膜信息的面形分布，实现对薄膜样片厚度的自动化测量。研究结果表明：所测薄膜厚度的峰谷值为0．2562，均方根值为0．068λ，说明采用基于FFT的薄膜厚度干涉测量新方法测量薄膜厚度具有较高的精度。

Interferometric Measurement Method of Thin Film Thickness Based on FFT

The kernel of modern interferometry is to obtain necessary surface shape and parameter by processing interferogram with reasonable algorithm. Studying the basic principle of interferometry by using 2-D FFT arithmetic, a new method to measure the thin film thickness is proposed based on the FFT algorithm. Taking advantage of Twyman-Green interferometer, a fringe interferogram measuring the thin film can be obtained by CCD receiving and acquired card collection. According to the knowledge of interferogram processing, the algorithm processing software is prepared to realize identification of the edge films, regional extension, filtering, unwrapping the wrapped phase, etc. Surface distribution with the film information can be obtained, and the thickness of thin film samples is measured automatically. The pv and rms values of the measured film sample are 0. 256λ, and 0. 068λ, respectively. The results indicate that the new method has high precision.