High speed optical inspection apparatus using gaussian distribution analysis and method therefore

Abstract

An optical inspection apparatus operates at high speed at very high resolution for detecting defects in flat, polished media in a production environment. The configuration of the first embodiment is used to inspect transparent disks such as those used as disk platters in hard disk drives. The configuration of the second embodiment is used to inspect reflective disks. The configuration of the third embodiment is used to inspect transparent flat panels such as those commonly used in Liquid Crystal Display (LCD) panels. All embodiments use a laser providing a light beam directed to a polygon scanner, which provides a linear scan of the beam. The unit to be inspected is moved such that its entire surface passes the scan path of the light beam. The light beam, after contacting the unit to be inspected, is directed to a parallel detector array, which detects changes in the nominal Gaussian distribution of the light beam that correspond to defects above a programmable threshold level. This parallel detection method allows the inspection apparatus to identify defects much smaller than the diffraction limits of the optics used, and will accurately identify changes in the light beam caused by defects in the media. An automatic media handler loads untested units into the apparatus and unloads and sorts tested units according to the results of the inspection.