| 摘要 |
PROBLEM TO BE SOLVED: To reduce a shift in image formation position with simple constitution and to adjust print width by providing a means which moves only a 1st lens along its optical axis. SOLUTION: Light is emitted by a light source 1 and collimated by a collimator lens 2 into parallel light. Then the light passes through a cylinder lens 3 interposed for surface tilt correction and is deflected by a rotary polygon mirror 4. The light is narrowed down on a photosensitive body 8 through an Fθlens consisting of a 1st lens 5 and a 2nd lens 6. In this case, the 1st lens 5 can be moved along the optical axis as shown by an arrow 10. Here, this 1st lens 5 is a spherical lens with negative power, the 2nd lens 6 is a positive lens which is different in radius of curvature between a horizontal scanning direction and a vertical scanning direction, and the lens 11 is a cylindrical lens which is long in the scanning direction. The lens 11 has refracting power only in the vertical scanning direction, so there is no need to consider Fθproperty and curvature of field in the scanning direction.
|
