Focal length measurement based on the correlation coefficient matching strategy

This paper proposes a new method to measure the focal lengths of both convex and concave lenses based on the correlation coefficient matching strategy. An interference model related to the real interferogram is built in advance to calculate the correlation coefficients between the simulated interferogram and the real interferogram by traversing parameters method. The parameters related to the maximum correlation coefficients can be used to confirm the focal length. For a biconvex lens with a focal length of 175.578 mm and a biconcave lens with a focal length of -100.001 mm, the relative measurement errors are 0.126% and 0.202%, respectively. Our measurement method is easy and efficient, and the measurement system is compact, easy to set up and low cost, which does not require the expensive precision displacement equipment, the distance measurement systems and the optical components.