| 摘要 |
A method and a device for discriminating an upper surface from a lower surface, particularly for detecting the directivity of an item having upper and lower surfaces which are hard to be discriminated merely with the naked eye in a member having an outer periphery formed in a vertically asymmetrical shape, for example, a disk- like, a cylindrical, or an annular member, more specifically, a piston ring with directivity which forms the component of an engine. The disk- like, cylindrical, or annular member having the outer periphery formed in the vertically asymmetrical shape is put on a reference plane having a reference block, the outer peripheral part of the member is brought into contact with the reference block on the reference plane, and the upper surface which is discriminated from the lower surface, inline, through a clearance formed between the outer peripheral part of the member and the reference block by using an illumination for light source and a camera for detection.
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