| 摘要 |
PURPOSE:To correct face inclination without using a long cylindrical lens by providing the 2nd image formation optical system arranged between a deflector and a medium to be scanned with one toric face, two cylinder faces and three spherical faces. CONSTITUTION:Parallel light beams from a light source part 1 are made incident upon the polarizing reflection surface 4 of a rotary polygon mirror 3 through a cylindrical lens 2 and the reflected light beams from the reflection surface 4 from a spot on the medium 8 to be scanned. Three lenses arranged between the polygon mirror 3 and the medium 8 consist of an anamorphic single lens 5, a single spherical lens 5 having a positive refractive power and a single lens 7 having a toric surface arranged successively from the side of the polygon mirror 3 to constitute the 2nd image formation optical system. The image of the deflected light beams is formed like a spot on the medium 8 by the three single lenses 5-7 and the formed spot scans the surface of the medium 8 by rotating the polygon mirror 3. Consequently, the curve of the image surface can be efficiently corrected. |
