INSPECTION OF DEFECT OF TRANSPARENT OR SEMI-TRANSPARENT PLATE-SHAPED BODY

PURPOSE:To detect the defective part of a transparent or semi-transparent plate-shaped body to be inspected in the form of the disurbance of a line array disposed with plural lines at equal intervals at the spacing narrower than the size of the defective part to be inspected by observing the above-mentioned line array through the plate-shaped body. CONSTITUTION:The line array disposed with the lines at equal intervals at the spacing narrower than the size of the defective part to be detected in observed through the transparent or semi-transparent plate-shaped body 2 to be inspected. The refracting way of light at the defective part 2a which consists of the same material as the material of the non-defective part of the body 2 and is different in density therefrom or the defective part 2a where part of the surface builds up or dents is different from the refracting way of the light at the other part if such defective part exists and therefore the line array 1 is observed as the disturbed array or the array different in the spacing, line size and various densities from the non-defective part. The discrimination of the non-defective part and the defective part 2a and the detection of the defective part are thus made possible.