Patent attributes
A defect inspection method for a transparent plate material for detecting a bubble, a scratch, a foreign matter, and another defect existing on or in the transparent plate material. The method includes capturing a first image of a main surface of the transparent plate material and capturing a second image of a rear surface of the transparent plate material. A defect candidate is searched for in each of the first and second images. Whether a real image or a virtual image was formed is determined, based on a contrast of an image of a defect candidate obtained by the search. Further, based on an appearance pattern of the real image or the virtual image, a determination is made as to whether the defect candidate is located on the main surface, inside, or on the rear surface of the transparent plate material.
