Patent ID: 8264515
Filing Date: 2012-09-11
Classification: B41J,G02B

Abstract:
1. An optical scanning device comprising: a light source; an optical deflecting unit that deflects a light beam emitted from the light source to scan on a scanning surface in main-scanning direction; and a scanning optical system that includes a first scanning lens and a second scanning lens that converge the light beam deflected by the optical deflecting unit onto the scanning surface; wherein distance between an exit surface of the first scanning lens and an incident surface of the second scanning lens is shorter than distance between a deflection facet of the optical deflecting unit and an incident surface of the first scanning lens; an exit surface of the second scanning lens is nearer to the deflection facet than a midpoint between the deflection facet and the scanning surface; and an image-surface-side principal point of the scanning optical system in sub-scanning direction is nearer to the scanning surface than the midpoint between the deflection facet and the scanning surface; and wherein sub-scanning-cross-sectional profile of the first scanning lens is double-concave at every image height, and sub-scanning-cross-sectional profile of the second scanning lens is meniscal at every image height, with concave surface of the second scanning lens being opposed to the deflector; and wherein following relation is satisfied: |φ3|≦|φ2|≦|φ1|, where φ1 is power in the sub-scanning direction of the incident surface of the first scanning lens, φ2 is power in the sub-scanning direction of the exit surface of the first scanning lens, and φ3 is power in the sub-scanning direction of the incident surface of the second scanning lens, each of φ1, φ2, and φ3 being negative power.