| 摘要 |
PURPOSE:To exactly detect an incident position of a specific light beam to a photodetecting panel, irrespective of an intensity variation of an ambient light beam, by constituting so that a mean value of photodetecting values obtained from plural photodetectors of the phosodetecting panel is derived, and it is compared with the photodetecting value. CONSTITUTION:Photodetecting signals A from a plurality of photodetectors 1 placed on a photodetecting panel are scanned and selected in order by a photodetecting signal selecting part 2, and are sent to a storage part 6 through an A/D converter 5. A stored photodetecting value E is read out and added by an operation control part 7, its sum total is divided by the total number of all the photodetectors, and a mean value of the photodetecting values is derived. This means value is used as a threshold level, this threshold level is compared with the photodetecting value of each photodetector 1 by the operation control part 7, and when a photodetecting value has exceeded the threshold level, a photodetector number is read out from the storage part 6 which has stored said photo detecting value, its photodetecting position is detected, and it is sent out as a photodetecting position signal D. Accordingly, a position of an incident light beam to the photodetecting panel is detected exactly without being influenced by an ambient light beam. |
