| 摘要 |
PURPOSE:To enable respective laser beams to make incident on a deflecting surface as linear images by providing an optical system for incidence which has a cylindrical lens between each semiconductor laser and the polarizing surface, and making the direction of refraction by the cylindrical lens coincident with one of two directions where astigmatic difference is caused. CONSTITUTION:A laser beam 2 which is reflected by the deflecting surface 6a is entered in and converged by the cylindrical lens 8 which has focal length suitable to convergence on a convergence position P on a surface to be scanned. At this time, the laser beam travels through an optical path shown by a solid line in a figure unless a rotary polygon mirror slants, but the optical path moves to a position shown by a broken line if the deflecting surface 6a shifts in position to 6a' owing to surface inclination. Further, a laser beam in the optical path shown by the solid line is also emitted from the same point on the deflecting surface 6a, so a scanning lens 5 and the cylindrical converge both the solid-line laser beam and broken-line laser beam on the position P. |
