| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of executing correction by a method wherein a position shift among each of color images is detected accurately more than heretofore. SOLUTION: In a belt ground section before a mark for detection position shift, an average of K points is calculated, a level Vs of the belt ground section is calculated (S1) and the data is sequentially compared with each other, then a peak point P and the level Vp are obtained (S2). By taking a level '(Vp-(Vs+α))×β' which is a level between a voltage value 'Vs+β' greater than Vs by a predetermined level α and Vp and is obtained by using a predetermined ratio β as a threshold level, a point that the detection signal becomes '(Vp-(Vs+α))×β' and measured points PL', PR' in the vicinity thereof are obtained (S3). A smoothing operation is applied to points which become predetermined values of ±a of front and rear data of these points (S4). The point becoming the level '(Vp--(Vs+α))×β' and two points PL, PR in the vicinity thereof are obtained (S5), then the intermediate point Pc is made to be a mark center (S6). |
