| 摘要 |
An optical scanner according to the present invention comprises a first imaging optical system consisting of a collimator lens (2) and a cylindrical lens (3), a light deflector (5) reflecting/deflecting a light beam for scanning; and a second imaging optical system consisting of an f-&thetas; lens (6) and an anamorphic lens (10). The f-&thetas; lens has three groups of lenses, i.e., a first lens (7) having negative refracting power, a second lens (8) having positive refracting power and a third lens (9) having positive refracting power. The f-&thetas; 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-&thetas; lens, f represents the focal distance of the f-&thetas; 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-&thetas; 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. <IMAGE> |
