| 摘要 |
<p>PROBLEM TO BE SOLVED: To certainly detect the existence of an object having narrower width such as carrier arm, using sets of transmission sensors. SOLUTION: Sets of transmission sensors S having light emitters and photo- detectors are disposed with specified spacings at an opening 4h for entering and ejecting an object such as carrier arm 10 and separately operated to detect the location of the object. The operation order of the sensors S is as follows. One sensor is operated. After its operation ends, a waiting time is taken, until the light from this sensor's emitter has no effect on the output of the photodetector of the adjacent sensor. Then the adjacent sensor is operated. Or, one sensor S is operated. After this operation ends, other sensor is operated which has a photodetector at a point where the quantity of the detected light from the emitter of that adjacent sensor is below a specified value.</p> |
