| 摘要 |
PURPOSE:To obtain a good-quality image even when recording density is switched over a wide range in a scanning optical device. CONSTITUTION:A 1st image-formation optical system which makes a laser beam emitted from a semiconductor laser 1 being a divergent light beam from a light source nearly parallel rays of light is a variable focusing collimator lens 10 consisting of a diaphragm 11, a convex lens 12, and a concave lens 13. Then, the lens 10 is a variable focusing lens capable of varying a focal distance by changing a space between the convex lens 12 being a positive lens (lens having positive power) and concave lens 13 being a negative lens (lens having negative power), and the the diameter of the flux of emitted light is varied in accordance with the recording density on a photosensitive drum 7 being a medium to be scanned. |
