Patent ID: 6987594

Claim:
An optical scanning apparatus, comprising: light source means; an incident optical system for temporarily focusing a beam emitted from the light source means in a sub-scanning section to form a linear image on a deflection surface of a light deflector; and a scanning optical system for guiding the beam deflected by the light deflector onto a surface to be scanned, wherein the beam from the incident optical system is incident at an angle with a normal to the deflection surface in the sub-scanning section; wherein the imaging magnification in the sub-scanning section of the scanning optical system is 0.7-fold or higher magnification in the entire scanning region and the scanning optical system includes a first scanning optical element having a refractive power in a main-scanning section and a second scanning optical element having a refractive power in the sub-scanning section, which weakens from an on-axis position to an off-axis position; and wherein an optical axis of the scanning optical element is eccentric toward a deflection point side of the deflection surface with respect to a transmission position of a principal ray of the beam in a sub scanning direction to meet the following expression: (βmax−βmin)<P/ΔL where βmax represents a maximum value of an imaging magnification in the sub-scanning section of an entire scanning region of the scanning optical system and βmin represents a minimum value of the imaging magnification in the sub-scanning section of the entire scanning region of the scanning optical system; P represents a pixel size defined according to a resolution in the sub-scanning section; and ΔL represents a distance between the normal to the deflection surface at the deflection point and the optical axis of the scanning optical element in the sub scanning direction.