| 摘要 |
PURPOSE: To correct plane tilt error on a deflector with a simple constitution without increasing the number of parts by specifying the radius of the curvature of a reflection optical device reflecting a laser beam from a laser light source in a direction different from an entering direction. CONSTITUTION: A laser beam is converged to a parallel light by light source unit 1 constituted of a laser diode and a collimator lens, is reflected by an extended cylindrical mirror 2, so that the shape of the beam is changed to be a nearly straight line state in which the longitudinal direction of the shape is in parallel with a main scanning direction, and a rotating polygon mirror 5 deflects the beam at a constant angular velocity in the main scanning direction. A toric lens 10 corrects the plane tilt error of each deflecting surface of the mirror 5 by combination with the mirror 2. The radius of the curvature of the mirror 2 is finite only in a sub-scanning direction, the radius of the curvature (focal distance) is changed, so that it is large on the laser beam entering side and it is small on an emitting side in terms of the main scanning direction, and a condensing surface is nearly in parallel with the deflecting surface of the mirror 5. |
