| 摘要 |
<p>An optical scanner according to the present invention comprises a collimator lens, a cylindrical lens, a light deflector, an f-&thetas; lens and an anamorphic lens. The f-&thetas; lens is constituted by three groups of five lenses, i.e., a first cemented lens formed by bonding a first lens and a second lens to each other, a second cemented lens formed by boding a third lens and a fourth lens to each other and a fifth lens having positive refracting power. The f-&thetas; lens is formed to satisfy relational expressions L/f < 0.100 and 0.04 </= r1/r4 </= 0.31, 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 an entrance-side refracting interface of the first lens and r4 represents the radius of curvature of an entrance-side refracting interface of the third 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></p> |
