Method and apparatus for detecting cosmetic defects in opthalmic lenses

Abstract

Method and apparatus for detecting and analyzing cosmetic defects on the surface of ophthalmic lenses. The apparatus according to one embodiment comprises means for scanning a narrow beam of light across the lens surface under inspection together with an array of photodetectors for detecting the manner in which the scanning beam is scattered or deflected as a result of striking a defect on or beneath the lens surface. More particularly, the photodetector array is mounted around the edge of the lens in a symmetrical pattern such that by properly monitoring the outputs of the detectors and by correlating these outputs with the position of the scanning beam, information regarding the position of the defect, the type of defect, and its severity can readily be ascertained in an automatic manner. By properly positioning the detector array around the edge of the lens, the system is able to automatically distinguish between cosmetic defects on the surface being examined and any defects which may be present on the opposite lens surface as well as between actual cosmetic defects and external surface debris such as dust or fingerprints. By an alternative embodiment, the array of photodetectors can be replaced with an array of light sources while the laser can be replaced with an appropriate detector. The system is particularly designed for inspecting the finished front surface of semifinished ophthalmic lenses although it has application in a variety of other fields.