| 摘要 |
PROBLEM TO BE SOLVED: To correct the positional error of a spot by reading out error information on a reflection surface used to deflect a luminous flux from a memory based on an index signal and controlling the luminous flux so that the error may be corrected. SOLUTION: Since an influence by plane tilt and irregular rotation appears as the shift of respective spots on a photoreceptor drum in a subscanning direction, the angle of a dynamic prism is changed so that the influence may be corrected. The shift amount of the spot on the photoreceptor drum caused by the plane tilt of the respective surfaces of the polygon mirror is previously inputted in the memory 401 of a central control circuit 400. When the reflection surface used for next scanning is specified from output from a polygon sensor 374, the angle of the dynamic prism capable of cancelling the shift of the spot caused by the reflection surface is obtained, and a prism driving part 161 is controlled based on the obtained result so as to set the angle of the dynamic prism. |
