Calibration of geometric distortion based on a reference sheet in oblique laser interferometry

Abstract When the form deviation of curved surface is measured with oblique laser interferometry, the collected interferogram is badly distorted, and cannot be positioned on the measured surface directly. The simulated object image is employed as a bridge to solve the problem. However, the geometric distortion is ignored in the current measurement, and prevents a high accuracy of the registration result between measured surface and interferogram. This paper focuses on calibrating the geometric distortion to improve the registration accuracy. Firstly, the object image of a reference sheet is captured in the same position and measurement system with measured curved surface. Then, the object image is compared with its simulated object image to establish the geometric distortion model. Next, the geometric distortion is integrated with image foreshortening and anamorphic distortion to simulate a better object image. Finally, the experimental results are given to show the more accurate registration result, and verify the feasibility and effectiveness of the proposed method.