| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming apparatus which performs rough positioning accurately prior to precise positioning in order to facilitate the precise positioning.SOLUTION: Individual patch patterns for constituting a registration patch for registration control are formed, using a laterally long tile pattern formed of 128 dots in an X-direction and 32 dots in a Y-direction as a minimum unit pattern, in a matrix of 32 dots in the Y-direction by 8 rows in a range of 320 dots in the X-direction. A patch pattern of a reference color K pattern 55 is shifted by 3 dots sequentially in a main scanning direction, to form 43 pattern-shifted patch patterns on a transfer belt. A concentration sensor 20 reads 15 spots in a concentration sensor reading area of each of the 43 patch patterns along with running of the transfer belt, to set a patch pattern presenting as a desired mode a mode obtained by 15 output values, as a reference patch pattern for quadruple patch pattern registration correction. |
