TRANSPARENT SUBSTRATE INSPECTING DEVICE

摘要

PROBLEM TO BE SOLVED: To positively detect presence of a flaw even with orientation to an irradiating direction of an illumination beam such as a hairline flaw. SOLUTION: An illuminating means irradiates a light beam emitted from light sources 100 and 200 as an elongated elliptical illumination beam for flaw detection on a glass substrate 40 using a plurality of lens means 101-204 and 201-204. An image forming means focuses scattered light or reflected light of the illumination beam irradiated on the glass substrate 40 into an image by using a detection lens 10 and the image is detected by a photo-detector means 30. At this point, the illuminating means irradiates illumination beams from four directions so they respectively cross at different angles with a longitudinal direction of the illumination beam on the glass substrate 40. Since crossing angles of the illumination beams and a longitudinal direction of the hairline flaw can be provided at 45 deg. within±25 deg. by irradiating the illumination beams from the four directions, presence of a flaw even with orientation to an irradiating direction of an illumination beam such as the hairline flaw can be positively detected.