Patent ID: 7245311

Claim:
An image forming apparatus, comprising: a photosensitive body; and an optical scanning device having a deflector deflecting a light flux emitted from a light source, and scanning a surface of said photosensitive body by the thus-deflected light flux formed as a beam spot in a main scan direction along main scan lines separated from one another in a sub-scan direction on said surface of said photosensitive body, wherein said image forming apparatus is configured such that new dots are formed centered between adjacent main scan lines in areas exposed to overlapping beam spot portions when an exposure intensity exceeds 50% of a maximum value there, wherein each beam spot has a first static beam-spot diameter Ws in said sub-scan direction on said surface of said photosensitive body and a second static beam-spot diameter Wm in said main scan direction on said surface of said photosensitive body, each static beam-spot diameter being defined by 1/e 2 of a maximum value in an exposure distribution of the associated beam spot, wherein a ratio of a first static beam-spot diameter Ws to an interval L between adjacent scan lines satisfies the following formula: 1.2 <Ws/L< 4.5, and wherein a ratio of said second static beam-spot diameter Wm to the first static beam-spot diameter Ws satisfies the following formula: Wm/Ws< 1.