Determination of long focal length of lenses with Talbot interferometer

In this paper, a method for high-accuracy determination of long focal length based on Talbot interferometer is presented. Through changing the angle between two gratings, systematic errors are reduced effectively by calibration. The collimation of the light is determined by a standard concave mirror. The experimental results reveal that the relative error is 0.1%, and the repeatability is better than 0.1%. As the method is simple and somewhat insensitive to environmental effects, it is especially useful for measuring long focal-length lenses.