High-accuracy measurement of the focal length and distortion of optical systems based on interferometry

A figure measuring interferometer (FMI) method is proposed for high-accuracy measurement of the focal length and distortion of optical systems simultaneously. FMI uses the Zernike coefficients of interference fringe to identify the image point position precisely, and then measures the distance between the image points under the different fields to determine the image height. The field of view can also be accurately obtained by a precise rotating platform. Linear fitting between the field of view and the image height is used to calculate the focal length and distortion. The experimental results indicate that FMI has a relative expanded standard uncertainty of less than 0.01% for focal length and 0.02% for distortion. In brief, the proposed method is feasible for measurement of the focal length and distortion with high accuracy, promising further industrial applications.