| 摘要 |
This disclosure is concerned with the optical detection of pin holes or similar aberrations in sheet material, such as metal or metalized packaging materials that are to enclose and seal contents therewithin, with the aid of a reflective-wall cavity structure over which the sheet material is placed and light-sealed and the walls of which are shaped to enable external light leaking through the pin hole or the like to become multiply reflected from the cavity walls and the underside of the sheet to impinge upon photodetecting means at an appropriate portion of the walls, thus to enable detection of such leak, and, if desired, location of the pin hole or the like.
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