| 摘要 |
PROBLEM TO BE SOLVED: To reduce sizes of an optical scanner, an exposure unit equipped with the optical scanner, and an image forming device by enhancing flexibility of shape and arrangement of the process unit, etc. SOLUTION: The optical scanner comprises a rotating polygon mirror for scanning a beam from a pre-deflection optical system in the main scanning direction, and two mirrors 23 and 25 for focusing the beam scanned by the rotating polygon mirror 5 on an image surface. The first mirror 23, on the rotating polygon mirror 5 side, has a negative power in the main scanning direction, and the second mirror 25 on the image surface side has a positive power in the main scanning direction. Consequently, the distance between the last imaging element and the image surface is secured, while an increase in the optical path length between the reflecting surface 5A of the rotating polygon mirror 5 and the image surface is restrained, thereby, flexibility of the shape and the arrangement of the process unit, etc. can be enhanced, and the sizes of the devices can be reduced. COPYRIGHT: (C)2007,JPO&INPIT |
