Patent ID: 7486389

Claim:
A lens meter for measuring refractive power distribution in a wide range of a subject lens to be measured, the lens meter comprising: a measurement optical system including: a projection unit having a light source and a target plate, which projects a target pattern for refractive power distribution measurement. a projection lens, a diaphragm having an aperture disposed at a front focal point of the projection lens between the projection unit and the projection lens, wherein a diameter of the aperture is variable, a field lens disposed between the projection unit and the aperture, wherein the aperture is disposed at a back focal point of the field lens, and a two-dimensional photodetector which detects an image of the target, pattern passed through the subject lens, which is disposed so as to have a conjugate relation with the target plate with respect to the projection lens and the subject lens in a case where the subject lens with one of a specific diopter in the vicinity of 0D and a frequently-used specific diopter is placed in a measurement position; and a control device that changes a size of each measurement light bundle of the target pattern by changing the diameter of the aperture based on an output signal from the photodetector, and obtains the refractive power distribution.