Surface inspection apparatus using a mask system to monitor uneven surfaces

Claim 1

A surface inspection apparatus comprising: (a) a light source for irradiating an uneven surface of an object to be inspected; (b) a photoelectric conversion sensor for picking up the uneven surface of the object and generating a video signal thereof; (c) an electronic processor for processing the video signal to inspect the surface of the object; (d) an optical mask formed of two opaque portions and two transparent portions which are arranged alternately around the center of the optical mask, the two opaque portions being symmetrical to each other with respect to the center of the optical mask, the two transparent portions being also symmetrical to each other with respect to the center of the optical mask, said optical mask being located in front of the light source with the center of the former being coincident with the optical axis of the light source; (e) light splitting means for dividing the light passed through the optical mask into two directions intersecting at substantially 90 degrees; and (f) two light reflecting means for respectively reflecting thereon the lights from the light splitting means in such a manner that reflected lights intersect each other at substantially 90 degrees at the center of the surface of the object so that irregular light reflection on the uneven surface becomes substantially uneven.