| 摘要 |
PURPOSE:To satisfactorily correct curvature of field so that good optical scanning is enabled by using a single lens which is well corrected in ftheta characteristic as an ftheta lens and subjecting either of a collimating lens or laser light source whichever is movable to simple oscillation in an optical axis direction in synchronization with the optical scanning. CONSTITUTION:The ftheta lens which is well corrected in the ftheta characteristic and curvature of field tends to have intricate lens constitution but the ftheta lens is easily realized even with a single lens if the correction of only the ftheta characteristic is involved. The single lens which is well corrected in the ftheta characteristic is, thereupon, used as the ftheta lens 4 and the curvature of field is corrected by the simple oscillation of the collimating lens 2 or the laser light source 1. The curvature of field is thereby satisfactorily corrected and the good optical scanning is enabled. |
