| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that stain and dust deposited on a surface of a transparent sheet-like member are required to be detected distinguishedly from a flaw, a forein matter and the like, because there are the stain and the dust deposited on a surface of the transparent sheet-like member in addition to the defect such as the flaw and the forein matter in the transparent sheet-like member, and because the stain and the dust deposited on the surface are able to be removed by washing. SOLUTION: This defect detector is provided with an illuminator for irradiating the transparent sheet-like member from an end face thereof with light to be transmitted through an inside the transparent sheet-like member, and illuminators for irradiating the transparent sheet-like member from both sides thereof. The stain and the dust deposited on the surface of the transparent sheet-like member are distinguished from the defect such as the flaw and the forein matter, and only the defect is detected, based on an image image-picked up by the respective illuminators of the detector.
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