The film thickness is an important technical indicator of film devices, and its accuracy directly affects various performances of optical components. In fabrication process of film device, fast and accurate measurement of film thickness has positive significance on product quality control. In this paper, measure film thickness with lateral shearing interferometry. Collect interferograms through structured lateral shearing interference platform, process interferogram with Fast Fourier Transform method to extract phase, unwrap the wrapped phase to achieve phase value. Finally, calculate film thickness based on lateral shearing interference principle. The thickness of sample is 119.6800nm measured by this method, basically the same with the result 120.6036nm that measured by ZYGO interferometer. This experiment shows that lateral shearing interferometry not only suit to measurement of film thickness, but also abundant high-precision method of measuring film thickness, and has high practical value.
