| 摘要 |
PURPOSE: To prevent a rotary polygon mirror from being contaminated by air flowing in an optical box. CONSTITUTION: A laser beam L1 generated from a light source unit 11 is deflected by the rotary polygon mirror 12 to perform scanning, and fetched from the window 22 of the optical box 20 through an image-formation lens 13. The cover, which is not shown in figure, of the optical box 20 is provided with an air flow guide plate 33 so as to introduce the air flowing in the optical box from the window 22 toward an electrostatic attractive filter 24, whereby the air cleaned by the filter 24 flows around the polygon mirror 12 as shown by arrows W1 to W5 and is returned to the window 22. |
