| 摘要 |
PURPOSE:To compensate curvature of field and make an excellent optical scan with small variation in spot diameter possible by providing a barrel-shaped toroidal surface as a concave surface for field curvature compensation. CONSTITUTION:A lens for light scanning consists of plural lenses and a correction optical system is a long-sized toroidal lens 6A arranged between the lens for light scanning and an unscanned surface and includes the barrel-shaped toroidal surface, whose radius of curvature in a subscanning direction decreases with the distance of the optical axis in a main-scan corresponding direction, is contained as the concave lens surface. Consequently, the curvature of field in the subscanning direction can be compensated excellently and the optical scanning system which has good mass-productivity is obtained. Further, the constitution is simple, the cost is reducible, and an excellent optical scan can be made. |
