| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that toner dropping from an intermediate transfer belt falls and lies on an optical sensor to cause the faulty detection of a registration mark, consequently, color shift is not satisfactorily corrected in an image forming apparatus where the optical sensor is disposed vertically below the horizontal conveying part of a transfer belt. SOLUTION: A pinhole for projecting light 182 and a pinhole for receiving light 183 are provided on the opposed surface 181 of the optical sensor 18. When detecting the registration mark, light is projected through the pinhole for projecting light 182 and is also received through the pinhole for receiving light 183. Since the pinholes 182 and 183 are formed as physical holes, the toner is prevented from falling and lying. COPYRIGHT: (C)2007,JPO&INPIT
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