| 摘要 |
PROBLEM TO BE SOLVED: To detect the dislocations in the main and subordinate directions of toner images which constitute a recording image. SOLUTION: The first class patterns PT1 BK1, etc., which are slender in the main scanning direction are obtained in each optical writing device as an unfixed toner image on the surface of a transparent common transfer belt 10 rotating at a constant speed and irradiated at a fixed position by the first light source 121 for detecting subordinate scanning dislocation from the front side of the transfer belt, the light is received by the first light receiving element 125 through the first slit SL11 for detecting subordinate scanning dislocation which is arranged to contact or close to the back side of the transfer belt and slender in the main scanning direction and has a width nearly equal to the width of the first class pattern, on the basis of the detection signal of the first class pattern of each optical writing device from the first light receiving element 125, the dislocation in the subordinate scanning direction of each optical scanning device is detected, and the dislocation in the main scanning direction is detected similarly. |
