| 摘要 |
PROBLEM TO BE SOLVED: To provide a mark detector which can improve the tolerance of discrimination when a mark put on a transparent body is detected by a beam sensor and also can stably discriminate plural marks to be detected at a time with no mutual interference (crosstalk). SOLUTION: A mark detector detects plural marks 9a, 9b... put on a transparent sheet substrate 9 and is provided with a light projection part 10 consisting of plural light projection fibers 10a, 10b... of a transmissive photoelectric sensor, a light receiving part 20 consisting of the light receiving fibers 20a, 20b... corresponding to the fibers 10a, 10b... respectively and a shielding plate 3 where the parts 10 and 20 are placed opposite to each other with a prescribed space secured between them and which has the openings 3a, 3b... formed on each optical path connecting together both parts 10 and 20. As wraparound quantity of light can be decreased around the marks by the plate 3, the difference of quantity of light can be increased between the 'mark' and 'non-mark' modes. |
