Patent ID: 7428088
Filing Date: 2008-09-23
Classification: G02B,H04N,Y10S

Abstract:
1. An optical scanning apparatus, comprising: a light source means; an incident optical system for guiding a light beam emitted from the light source means to a deflecting means; and an imaging optical system for guiding the light beam reflected by the deflecting means onto a surface to be scanned, in which a deflecting surface of the deflecting means and the surface to be scanned satisfies a conjugate relation in a sub-scanning cross section, wherein the incident optical system comprises an anamorphic condenser lens having an optical power in a main scanning direction and an optical power in a sub-scanning direction, the optical power in the main direction and the optical power in the sub-scanning direction being different from each other; wherein a material of the anamorphic condenser lens is a plastic material, and wherein the anamorphic condenser lens comprises a diffractive portion having an optical power on at least one surface, wherein both the optical power in the main scanning direction of a refractive portion of the anamorphic condenser lens and the optical power in the sub-scanning direction of the refractive portion of the anamorphic condenser lens have a positive optical power; wherein both the optical power in the main scanning direction of a diffractive portion of the anamorphic condenser lens and the optical power in the sub-scanning direction of the diffractive portion of the anamorphic condenser lens have a positive optical power; and wherein the following conditions are satisfied: where Φ refr M represents the optical power in the main scanning cross section of the refractive portion, Φ diff M represents the optical power in the main scanning cross section of the diffractive portion, Φ refr S represents the optical power of the refractive portion in the sub-scanning cross section, and Φ diff S represents the optical power in the sub-scanning cross section of the diffractive portion, and wherein the imaging optical system satisfies the following conditions: where β represents a lateral magnification in the sub-scanning direction of the imaging optical system, w 0 represents a beam radius in the sub-scanning direction in a beam waist position of an imaging spot condensed by the imaging optical system, and λ 0 (mm) represents a wavelength of the light beam emitted from the light source means, and δ X (mm) represents an error of a position of an optical axis direction of emission of light point of light source means.