| 摘要 |
PROBLEM TO BE SOLVED: To enable the inspection of whether foreign matter is present or absent at a heel part even with the presence of projections and recessions at the periphery by providing diffused beams to irradiate the heel part from diagonally underneath and a camera to photograph the heel part from an opposing direction diagonally above, and determining a part photographed darker than a background as foreign matter. SOLUTION: Light from a diffused light source 3 becomes incident on the projected and recessed part 2 of a heel part 1c in a rotating bottle 1. Light incident on the projected and recessed part 2 from multi-directions is transmitted through the heel part 1c on the side of the light source 3 and becomes incident on a body part 1a on the side of a camera 4. Here, as multi-directional light from the diffused light source 3 becomes directly incident on the projected and recessed part 2 of the heel part 1c, the projected and recessed part 2 is blurred. As light from the projected and recessed part 2 is transmitted through the heel part 1c on the light source side and the body part 1a on the camera side and becomes incident on the camera 4. the projected and recessed part 2 is further blurred. Therefore, the image of the projected and recessed part 2 of the heel part 1c has no difference in contrast as much as the other part of the heel part 1c, and only the image of foreign matter 9 present at the heel part 1c is dark. The angleθwhich the optical axis Lx of the camera 4 forms with a horizontal plane is 23-30 degrees.
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