Measurement of lens focal length with Hartmann–Shack wavefront sensor based on 4F system

Knowledge of the focal length of a lens is vital in the construction of all optical instruments, from spectacles to large astronomical telescopes. In this paper, we described a method using Hartmann–Shack sensor to measure the focal lengths of lenses based on the 4F system. The experimental system that we have set up and the experiments which have been done are described, and also the formulas used to calculate the focal lengths of lenses are being given. A clue to improve the measurement accuracy is given. Compared to other methods, it is easy to get a precision value of the focal length using our method, and the relative error will be less than 0.1%; meanwhile, it shows the distribution of wavefront aberrations of imaging information of the detection-area of the lens.