| 摘要 |
PROBLEM TO BE SOLVED: To increase the F number of a 1st image formation optical system without increasing the size of the optical system or decreasing the diameter of the aperture, and obtain a desired spot diameter while suppressing light quantity loss small. SOLUTION: The parallel laser beam which is emitted by a semiconductor laser 10 and transmitted through a collimator lens 11 is passed through a cylindrical lens 12 as the 1st image formation optical system, and reflected and deflected by a polygon mirror 14 as a deflector to form a spot scanning a photoreceptor drum 18 in a horizontal scanning direction through a 2nd image formation optical system consisting of a curved surface mirror 15 and an anamorphic lens 16. The line image LI formed by the cylindrical lens 12 is positioned between the polygon mirror 14 and curved surface mirror 15. |
