| 摘要 |
PROBLEM TO BE SOLVED: To surely detect a black defect included in transparent granular objects to be tested. SOLUTION: In an inspection unit 2, a lower illuminating apparatus 4 is arranged below a transparent conveyor belt 3, while an ultraviolet emitter 5 is arranged above the conveyor belt 3. The image of a tested object S is photographed by means of an imaging device 6 in the inspection unit 2 so as to be processed by means of an image processor 7, and if a colored part is detected in the tested object S, it is determined as being a defective. When the tested object S is irradiated with ultraviolet rays from the ultraviolet emitter 5, fluorescence which is a visible light is produced, and the tested object is illuminated from the inside, so that the whole of the tested object is brightened without shadows even in its end part. Therefore, the image taken by the imaging device includes no shadow, and wrong determination of a defective part can be prevented.
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