| 摘要 |
PROBLEM TO BE SOLVED: To perform accurate positional deviation correction, by excluding detection errors of a positional deviation amount for accurate positional deviation correction and stably detecting a color pattern by even a low-cost optical detection means, in a color image forming apparatus of such a type that a black BK image forming means is located in the most-upstream position in the rotation direction of a conveyance belt or an intermediate transfer belt. SOLUTION: A positional deviation correction pattern 26 has two edges forming a tilt angleθ, with respect to a subscanning direction and includes patterns of black BK and cyan C on the most upstream side which are formed apart from each other in the subscanning direction, and patterns of yellow Y and magenta M, having a narrow width, which are formed over patterns of black BK and cyan C, respectively. A light beam is emitted from a red LED, having a peak in spectral sensitivity characteristics of the reflected light of cyan C, and a CPU detects the edges of yellow Y and magenta M on black BK and cyan C and performs positional deviation correction. COPYRIGHT: (C)2010,JPO&INPIT
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