Optical scanning device and image forming apparatus

An image forming apparatus that forms an image by performing electrophotographic image forming process, the image forming apparatus comprising:

• an optical scanning device as a device that performs exposure process in the electrophotographic image forming process, and wherein the optical scanning device includes:
• 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,
• 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
• the distance between the deflection facet of the optical deflecting unit and the incident surface of the first scanning lens is longer than a distance between the incident surface of the first scanning lens and the exit surface of the second scanning lens, 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.