| 摘要 |
PURPOSE:To detect the size of an original securely with high precision by irradiating the original slantingly from below and detecting a shadow formed on the reverse surface of an original pressure plate. CONSTITUTION:The original is placed on contact glass 1 at a reference position and the original pressure plate 10 is rotated downward to turn on a limit right before the pressure plate 10 contacts the glass 1. Detection signals of respective photodetection parts 53 are read in a detection part 54 at said timing to decide which photodetection part generates a photodetection signal and which photodetection part 53 outputs a non-photodetection signal, thereby detecting the original size on the basis of the decision results. In this case, a photodetection part 53 right below an original presence part outputs the photo detection signal, a photodetection part 53 right below the shadow 55 outputs the non-photodetection signal, and a photodetection part 53 right under a part a little to an exposure end side from the shadow 55 outputs the photodetection output signal.
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