| 摘要 |
PROBLEM TO BE SOLVED: To narrow down the variation range of the quantity of light on a photosensitive body. SOLUTION: Laser luminous flux emitted by a laser diode 16 is made by a collimator lens 18 and an expanding lens 20 into laser luminous flux having a nearly Gaussian profile which has horizontal-scanning directional beam width larger than the width of a reflecting surface 12A of a rotary polygon mirror 12 and also has its length in the horizontal scanning direction, and the luminous flux is made incident on the rotary polygon mirror 12. Laser luminous flux which is made incident on the rotary polygon mirror 12 from the side of the laser diode 16 is reflected and scanned by the reflecting surface 12A as the rotary polygon mirror 12 rotates. At this time, the optical axis of incidence of the laser luminous flux is moved by a movement quantity M from a reference position P as the center point of the reflecting surface 12A to the side opposite from the incidence in the horizontal scanning direction. |
