TRANSPARENT BODY INSPECTION METHOD AND TRANSPARENT BODY INSPECTION DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a transparent body inspection method and a transparent body inspection device which prevent defects from being erroneously detected due to thermal fluctuation defects, from a photographed image obtained under a high-temperature environment by the Schlieren method and, in the case that a surface of a transparent body like a plate or a thin film is distorted because of the existence of bubbles or foreign matters in the transparent body, are capable of detecting both bright areas and dark areas around areas corresponding to the bubbles or foreign matters, from the photographed image.SOLUTION: A line selection unit 11 successively selects lines from a photographed image of a transparent body like a plate or a thin film photographed by the Schlieren method. A differential processing unit 12 successively calculates differential values of gradation values of pixels in one line. When detecting a pixel of which the differential value is larger than a first differential threshold or is smaller than a second differential threshold, a labeling unit 13 compares gradation values of pixels following this pixel with a first gradation value threshold and a second gradation value threshold.