| 摘要 |
PROBLEM TO BE SOLVED: To more quickly acquire the rotational phase of each of photoreceptor drums.SOLUTION: Bodies to be detected 14 are formed as a plurality of protrusion members 14A to 14D arranged, respectively, along the same circular arc at intervals in a circumferential direction, at a black photoreceptor drum 7 and a non-black photoreceptor drum 6, and the plurality of protrusion members 14A to 14D are different in circular arc length, respectively. By such an arrangement, the rotational phase of the black photoreceptor drum 7 and the non-black photoreceptor drum 6 can be acquired in accordance with the time interval between the plurality of protrusion members 14A to 14D or the detection time length of the plurality of protrusion members 14A to 14D, accordingly, the rotational phase can be more quickly acquired. |
