| 摘要 |
PURPOSE:To simplify an optical system, and to make its cost low by forming the surface, opposed to a deflector of a surface inclination correcting cylindrical lens of a rotary polygon mirror, into a plane, and using a plano-convex cylindrical lens. CONSTITUTION:A laser beam emitted from a semiconductor laser 1 is converted to parallel rays by a collimator lens 2, condensed by an image forming lens 3, and brought to a linear image formation onto a deflecting surface of a rotary polygon mirror 5 by a one-direction condensing lens having an image forming capacity in only the direction vertical to the deflecting surface of the rotary polygon mirror 5. The laser beam is reflected and deflected by the deflecting surface of the rotary polygon mirror for rotating at a uniform speed in the direction as indicated with an arrow, made incident on a plano-convex cylindrical lens 6 and reaches on a recording body 7. By the plano-convex cylindrical lens 6, the deflecting surface of the rotary polygon mirror 5 and the recording body 7 being the surface to be scanned are in a conjugate relation, therefore, even if the deflecting surface of the rotary polygon mirror 5 is inclined from 5a to 5b, the laser beam follows an optical path of a broken line and always forms an image at a point (c) on the recording body 7, and a surface inclination of the deflecting surface of the rotary polygon mirror 5 is corrected. In this way, an optical system having a good aberration correcting effect can be simplified. |
