| 摘要 |
An optical scanner according to the present invention comprises a first imaging optical system consisting of a collimator lens and a cylindrical lens, a light deflector reflecting/deflecting a light beam for scanning, and a second imaging optical system consisting of an f-theta lens and an anamorphic lens. The f-theta lens has three groups of lenses, i.e., a first lens having negative refracting power, a second lens having positive refracting power and a third lens having positive refracting power. The f-theta lens is formed to satisfy relational expressions L/f<0.100 and 0.10<=r1/r3<=0.26, where L represents the total length of the f-theta lens, f represents the focal distance of the f-theta lens, r1 represents the radius of curvature of a light beam entrance-side refracting interface of the first lens and r3 represents the radius of curvature of a light beam entrance-side refracting interface of the second lens. Thus, a compact optical scanner comprising an f-theta lens having a small total length L and high optical performance is provided also when increasing a focal length f as well as a scanning line length W.
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