Patent ID: 7355771

Claim:
An optical scanning apparatus, comprising: a light source generating a laser beam; a deflection device to deflect the laser beam generated from the light source; and a scanning lens through which the laser beam deflected by said deflection device passes, wherein after the laser beam passes through said scanning lens, the laser beam generated from said light source is deflected by said deflection device, again passes through said scanning lens, and emits to the surface to be scanned, a light shield plate to shield the reflected light reflected by said scanning lens and traveling to said surface to be scanned is provided at the opposite side to the side where said deflection device is arranged with said scanning lens, as a boundary, and wherein, in a case that a distance between said deflection device and said scanning lens is taken as L 1 (mm), the distance between said deflection device and said light shield plate is taken as L 2 (mm), a thickness of said scanning lens as T (mm), an incident angle in the sub scanning direction of said laser beam to said deflection device as Î±, and a convergent angle of said laser beam as 2Î¸, said light shield plate is arranged within the range of satisfying the following formula: 2 â¢ â¢ tan â¡ ( Î± + Î¸ ) â¢ ( L 1 + T ) + 0.5 â¢ mm tan â¡ ( Î± + Î¸ ) + tan â¡ ( Î± + Î¸ ) < L 2 < 2 â¢ â¢ tan â¡ ( Î± + Î¸ ) â¢ L 1 - 0.5 â¢ mm tan â¡ ( Î± + Î¸ ) - tan â¡ ( Î± - Î¸ ) .