| 摘要 |
PURPOSE:To expand the degree of freedom of a design and to simultaneously correct the curvature of image surface and the scan non-linearity by forming the reflecting surface of a polygon optical deflector by a specific parabolic surface or parabolic cylindrical surface. CONSTITUTION:A polygon optical deflector 1 is provided with a reflecting surface 2 consisting of a parabolic surface or a parabolic cylindrical surface having the apex, and provided so that this reflecting surface 2 rotates centering around O. When a secondary coefficient of the reflecting surface which becomes a parabola in a rotary plane of the polygon optical deflector which has used an origin as the rotation center, and a distance extending from the rotation center O of the parabola to a position where an incident light beam is reflected by the reflecting surface are denoted as (a) and Rm, respectively, an equation of the parabolic cylinder is shown by X+ay<2>-Rm=0. In this regard, a relational expression for calculating a condition that a scan linearity error and a curvature of image surface become within + or -2% and within + or -0.05R, respectively is given. In such a way, the degree of freedom of a design is expanded, and the curvature of image and the scan non-linearity can be corrected. |
