| 摘要 |
<p>PURPOSE:To enable a detected object to be detected more accurately than usual despite the dispersion in the transmittivity and the reflecting power of the detected item by a method wherein a processing circuit to judge the existance of detected object is provided to process output signals from the first and the second photodetectors as input. CONSTITUTION:The light Ph1 from the first light emitting element 6 is reflected on a detected object 9 to be inputted in a photodetector 8 forming the first reflecting type light coupling channel while the light Ph2 from the second light emitting element 7 is reflected on the detected object 9 to be inputted in the photodetector 8 forming the second light coupling channel. The first and the second light emitting elements 6, 7 are time differentially driven not to be lighted simultaneously so that the output signal level Vs of photodetector 8 may be compared with the first reference level Vr1 in case the first light emitting element 6 is lighted in the processing circuit 10 while to be compared with the second reference level Vr2 in case the second light electrode 7 is lighted (provided Vr2<Vr1) with the processing circuit 10 assuming the logic sum of Vs>=Vr1, Vs>=Vr2 to be the existance judgement results a of the detected object 9.</p> |
