| 摘要 |
PURPOSE:To not only attain the dazzle preventing effect but to detect an original in size including a special size by providing a minimum required number of optical sensors in the front end part of a light shielding film used in a conventional device. CONSTITUTION:An original 14 has one corner matched to the left lower corner on a platen glass 2 and is placed in the position indicated by broken lines, and a light shielding film 4 is moved in the direction of an arrow, and reflective optical sensors 30 and 31 are arranged in such positions that end parts of originals of B4 size (longitudinally placing) and A3 size (transversely placing). The original size is discriminated as B4 when the reflective optical sensor 30 detects the original in the position 364mm distant from the positioning corner of the platen glass according as the light shielding film 4 is moved in the direction of the arrow, and the original size is discriminated as A4 when only the reflective optical sensor 30 detects the original in the position 297mm distant from the positioning corner. The original size is discriminated as A3 when reflective optical sensors 30 and 31 detect the original approximately simultaneously in the position 297mm distant form the positioning corner, and the original size is discriminated as B5 when the reflective optical sensor 30 detects the original in the position 257mm distant from the positioning corner. The light shielding film 4 is stopped at the original detection time to full film the light shielding and dazzle preventing effect.
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