Patent ID: 7355615

Claim:
An optical scanning apparatus for scanning a recording medium with laser light beam and exposing said recording medium to said laser light beam to record a latent image on said recording medium, comprising: a laser light source which generates said laser light beam; an optical modulator which is disposed on an optical path between said laser light source and said recording medium and is used to modulate said laser light beam; a reducing filter which has a light amount reducing function for reducing light amount of said laser light beam using absorption or reflection of said laser light beam and is disposed on said optical path of said laser light beam between said laser light source and said optical modulator; at least one reflection optical element disposed on said optical path of said laser light beam; and at least one transmission optical element disposed on the optical path of the laser light beam, wherein, when transmittance of said reducing filter is given by Î· nd , amount of light emitted from said laser light source is given by W 0 , amount of light required for recording on said recording medium is given by W 1 , diffraction efficiency in said optical modulator is given by Î· AOM , total reflectance of said at least one reflection optical element is given by Î· ref , and total transmittance of said at least one transmission optical element is given by Î· tra , the following expression (1) Î· nd =( W 1 /W 0 )/(Î· AOM Ã—Î· ref Ã—Î· tra )â€ƒâ€ƒ(1) is satisfied.