| 摘要 |
PROBLEM TO BE SOLVED: To perform optical scanning with a small baud by using a reduction optical element after separating a light beam and again image forming the light beam on a photosensitive body. SOLUTION: A magnification optical system 61 is constituted of cylindrical concave lens 61a and convex lens 61b, and an fθlens 50 is arranged between these tow groups of lenses. Then, four pieces o laser beams are made incident on a separation polygon mirror 42 in the state that an interval between respective laser beam each other is expounded by the optical system 61. At this time, the polygon mirror 52 is provided with reflection surfaces respectively reflecting four pieces of incident laser beams in the directions of corresponding final mirrors 53a-53d. Although the reflection angles of theses reflection surfaces are decided by the arranged positions of the mirrors 53a-53d, the arranged positions of these mirror 53a-53b are set so that respective optical path lengths from a semiconductor laser array 45 to a photosensitive drums 1a-1d become equal. Thus, bow-shaped adoration in a main scanning line is reduced. |
