AUTOLENSMETER

An autolensmeter for inspecting refracting power of optical systems is herein disclosed, which comprises a collimater lens for projecting light from a light source onto an optical system to be examined as a parallel luminous flux, a mask means having a mask pattern for selectively transmitting the luminous flux from the optical system and a photodetecting means for receiving the luminous flux partially transmitted through the mask pattern, disposed at a non-image forming position of the optical system, characterized in that an optical element is arranged in close vicinity of the mask pattern so that the light source and the photodetecting means are in an optical conjugate relationship with each other. The automlensmeter masks it possible to enlarge the width of the effective luminous flux for measuring the refracting power of the optical system without reducing the sharpness of the pattern projected on the photodetecting means and thereby eliminating the requirements for the use of photodetecting means of a high sensitivity and light sources of a high luminance and the accuracy of measurement being not influenced by the presence of, for instance dusts and/or water drops on the optical system and/or the mask means.