Patent ID: 6509966
Filing Date: 2003-01-21
Classification: G01N

Abstract:
A defect detection optical system for scanning a surface of a flat plate with light beam, receiving a reflection light reflected from the surface by a light receiver and generating a signal for detecting a defect by said light receiver, said defect detection optical system comprising:a light illuminating system for illuminating said light beam having a width in a direction perpendicular to a main scan direction and relatively scanning said flat plate; and a light receiving system including said light receiver composed of a plurality (n) of light receiving elements, where n is an integer larger than 1, arranged in the direction perpendicular to the main scan direction, for focusing an image of a scan position on said flat plate on said light receiving elements such that the image of the scan position on said flat plate, which is laid in the direction perpendicular to the main scan direction, becomes in the arranging direction of said light receiving elements, wherein, when a width of the image in the main scan direction is equal to or smaller than the width of said light receiving elements and a certain one of said light receiving elements receives a light reflected from a recessed defect or a protruded defect on said surface of said flat plate, the image of the scan position of said flat plate is moved in the width direction of said certain light receiving element, which is perpendicular to the arranging direction of said light receiving elements, and an amount of light received by said certain light receiving element is at least reduced.