| 摘要 |
PURPOSE:To make correction of the scan speed difference (distort abberation) involved with a conventional ftheta lens and a correction of the image surface curvature in aux. scanning direction using a simple optical configuration without provision of ftheta lens. CONSTITUTION:An optical system is composed of a semiconductor laser 1, a collimator lens 6, a polygonal mirror 10 whose reflex surface 10a assumes a convex spherical surface, and a spherical surface mirror 20. A light flux emitted from the semiconductor laser 1 is scanned over the reflex surface 10a of the polygonal mirror 10 rotating in the direction of arrow (a), reflected by the concave surface of the spherical surface mirror 20, and condensed on a photo-sensitive element 30. Because of sphericalness of the reflex surface of polygonal mirror 10 and the reflex surface of the spherical surface mirror 20, the image surface curvatures in the main scanning direction and aux. scanning direction and canceled, and the scan speed difference (distort abberation) is also corrected. |
