| 摘要 |
PROBLEM TO BE SOLVED: To provide a sheet size measuring device capable of measuring sheet size with high precision in a short time and using the device as a compact sheet size sensor at low cost to reduce the number of used sensors. SOLUTION: This sheet size measuring device and this image formation device have a sheet size detection passage SHa set on the halfway of a sheet conveyance passage conveying sheet, a fixed sensor SL1 detecting a position of one end part in the direction of sheet conveyance, moving sensors SL2, SN in the longitudinal direction having a light receiving element detecting a position of the other end part in the direction of sheet conveyance by receiving light projected on the sheet held into a plane shape from light sources SL2a, SL2a' and a light receiving element arranged in such a way that incident light quantity differs depending on a case where the light receiving element opposes to sheet and a case where the light receiving element does not oppose to sheet, and a position detection plate PL which is fixed and arranged in a travel scope of the moving sensors SL2, SN in the longitudinal direction and in which reference patterns PLb, PLb' for letting light capable of detecting distance of the moving sensors SL2, SN in the longitudinal direction from the fixed sensor SL1 come into the moving sensors SL2, SN in the longitudinal direction are formed. COPYRIGHT: (C)2005,JPO&NCIPI
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