| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of inexpensively and accurately detecting the size of a document without using an expensive photosensor. SOLUTION: Black tapes having optical reflectances different from that of the texture of a document set on a document table 2 are stuck to the lower side of a platen cover 3. By turning on an exposure lamp 5 provided on a carriage 4, the document is exposed. Thus, a reflected light image of the document is obtained and it is projected to an image signal output means by reflection mirrors 6, 7, 8 and a lens block 9 for magnification. A detection unit detects at least one edge of the document and the length of the edge according to the amount of reflected light from the document and that from the black tapes during the exposure. A judgement unit judges the size of the document set on the document table 2 according to the detection result of the detection unit. COPYRIGHT: (C)2008,JPO&INPIT
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