Apparatus for automatic measurement and display of the refractive power of lenses, in particular, astigmatism lenses

摘要

An automatic digital indicating lens meter is provided with an optical system having a light beam source and a target which reciprocally moves within a certain range along the optical axis, the target having several circular luminous points. An image pickup system including a lens to be inspected, such as a mono-focal point spherical lens or a bi-focal non- spherical point lens, is fixed on the optical axis approximately mating with the luminous centers of a light beam source collimator and a light beam receiving collimator. A photo electric converter is located at the focal plane of the receiving collimator; on an extension of said optical axis. An electric circuit analyses by scanning lines, the images detected by said electric light converter as time series signals and counts the position when the time band width of the brightness signal becomes minimum in the course of movement of the target. A further electric circuit, including a pulse motor for reciprocally driving said target through a desired diopter plus and minus range, and a signal generator for driving said motor is provided, said circuit automatically controlling said reciprocal driving of the target by synchronizing with said first mentioned electric circuit. An indicating circuit is utilized for discriminating plus or minus diopter indicating signals converted from the position, or positions, where said target image becomes of minimum area and also for digitally indicating the diopters.