Defect inspection method and apparatus for transparent plate-like members

A defected inspection apparatus 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 apparatus comprising:

• a first reflective bright-field optical system disposed at a main surface side of the transparent plate material, for capturing an image (hereinafter called a first image) of a main surface of the transparent plate material, the first optical system comprising a linear light source and a camera;
• a second reflective bright-field optical system disposed at a rear surface side of the transparent plate material, for capturing an image (hereinafter called a second image) of a rear surface of the transparent plate material, the second optical system comprising a linear light source and a camera;
• and
• a computer for searching for a defect candidate in each of the first and second images;
• for determining, based on the contrast of an image of a defect candidate obtained by the search, whether a real image or a virtual image was formed;
• and for determining, based on an appearance pattern of the real image or the virtual image, whether the defect candidate is located on the main surface, inside, or on the rear surface of the transparent plate material.