| 摘要 |
PROBLEM TO BE SOLVED: To prevent dust from infiltrating into the inner part of a casing by forming the flow of air crossing scanning light in the vicinity of the outside of an aperture. SOLUTION: A rotary polygon mirror deflecting a laser scanning light beam 2a oscillated from a laser light source is housed in the casing 8 having an emitting aperture 6 through which the laser scanning light beam is emitted. It is conceivable to set the laser light source in the casing 8. In such a case, a cover glass is not set at the emitting aperture 6 for the scanning light beam 2a of the casing 8, but a wide nozzle 10 blows off the air downward from the upper side just before the aperture 6 to cross the scanning light beam, 2a passing the aperture 6 is arranged on the outside of the aperture 6. Thus, the flow 12 of the air in an air-curtain state crossing the scanning light beam emitted from the inside of the casing 8 is formed in the vicinity of the outside of the aperture 6, so that the dust is prevented from infiltrating into the easing 8. |
