| 摘要 |
PURPOSE:To detect original size with high reliability only by providing one sensor for original size detection by allowing the photodetecting element of the sensor to photodetect reflected light from an original cover which is irradiated with light from a light emitting element from below and held closed while moving under an original platen, and detecting and deciding an output change due to the original. CONSTITUTION:Only light which is emitted by the light emitting element 5 of the sensor 7 provided under a transparent plate where the original is placed and transmitted through a transparent plate, reflected by the original cover 4 in a closed state, and not cut off by the original is incident on the photodetecting element 6. The output of the photodetecting element 6 of the sensor 7 which moves under the transparent plate in parallel to the original is sent to an AND gate 9 through an amplifier 8 and an inverter 9 and pulses from an oscillator 10 are inputted to a gate 11 and counted by a counter 12. Its signal is passed through a DA converter 13 and compared with reference voltages E1-E4 of comparators 14-17, whose outputs are passed through a decoder 18, so that signals corresponding to the original size are outputted from FFs 20.
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