US Patent 7099002 Defect detector and method of detecting defect

A defect detector having: a first optical system including a first light source to irradiate a surface of a subject with coaxial incident-light while scanning, and a first imaging device to receive light regularly reflected from the subject and change the light to a first electrical signal to form a first electrical image; a second optical system including a second light source to irradiate the surface of the subject with inclined light while scanning, and a second imaging device to receive light scattered at the subject and change the light to a second electrical signal to form a second electrical image, in which the inclined light of the second light source does not meet the coaxial incident-light of the first light source; and a computer to compare the first electrical signal with a predetermined first threshold to detect a concavo-convex defect on the surface of the subject, and to compare the second electrical signal with a predetermined second threshold to detect a blocky color defect on the surface of the subject.