| 摘要 |
PROBLEM TO BE SOLVED: To prevent a rotary polygon mirror and a scanning lens from being contaminated owing to an entry of the outside air due to deficiency in the sealing between an optical box and a lid. SOLUTION: A motor 14 is provided with a projection part 14a, which engages a recessed part 11a of the optical box 11 to position the motor 14 in the optical box 11. When the optical box 11 is covered with the lid 15 formed of a metal material, an elastic body 16 is sandwiched between the top surface of an image forming lens 13 and the lid 15. At this time, not a through hole, but a recess is formed as the recessed part 11a of the optical box 11, further the elastic body 16 between the image forming lens 13 and lid 15 cut off the outside air entered through the engagement gap between the motor 14 and optical box 11, and the lid 15 is made of metal and then made less in initial curvature than a lid made of synthetic resin, thereby reducing variation due to environmental changes. |
