| 摘要 |
PURPOSE:To mechanically and well correct the curvature of field of the entire part of an optical system by oscillating a linear imaging lens in synchronization with the period of optical scanning so as to negate the curvature of field. CONSTITUTION:At least the linear imaging lens 14 of the 1st imaging optical system which forms image like a main scanning line is moved to negate the direction of negating the curvature of field in synchronization with the luminous flux scanning by a rotary polyhedral mirror 18. Namely, this optical scanner is so constituted that a cylindrical lens 14 is moved in an optical axis direction via a mounting member 15 in accordance with the synchronization signal obtd. with a photodetector 22b to negate the curvature of field of the optical system. The curvature of field over the entire part of the optical system is mechanically and well corrected in this way. |
