| 摘要 |
PROBLEM TO BE SOLVED: To prevent the reflecting surface of a rotary polygon mirror from being contaminated with dust, etc., in the outside air. SOLUTION: The scanning light L1 of the rotary polygon mirror 3 passes through a spherical lens 4a and a toric lens 4b and is guided out of the window 8 of an optical box 7 toward a photoreceptor drum 5. The lower end of the spherical lens 4a is fixed to a pedestal 11a, a rib 12 which faces the flank of the spherical lens 4a is provided around the lens, and an air flow circulating on the bottom surface of the spherical lens 4a is cut off by labyrinth effect. A filler 13 of urethane foam, etc., is arranged between the top surface of the spherical lens 4a and the lid member to cut off an air flow circulating on the top surface of the spherical lens 4a. |
