Patent ID: 7616300

Claim:
An edge flaw detection device comprising: an elliptical mirror having a mirror surface on an inside thereof; a light-emitting unit that radiates coherent light toward an edge of an object, the edge of the object being arranged in a vicinity of a first focal position of the elliptical mirror; a photo detector that is arranged in a second focal position of the elliptical mirror and is capable of detecting the diffracted light resulting when the radiated coherent light is reflected by the edge of the object and by the elliptical mirror so as to arrive at the second focal position; and a light-shielding member that shields low-order diffracted light which is regularly reflected among the diffracted light, a position of the light-emitting unit being freely set in a thickness direction of the object by a moving member so that the light-emitting unit can radiate the coherent light in a different radiation range in the thickness direction at the edge of the object.