| 摘要 |
PURPOSE: A scanner lens is provided to achieve an improve performance of lens and high resolution of approximately 600dpi, while reducing size of lens and manufacturing costs. CONSTITUTION: A scanner lens comprises a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a third lens group having a positive refractive power. The scanner lens satisfies the condition of 0.40<f1/f<0.79, -0.35<f2/f<-0.30, 0.7<f3/f4<1.20, -0.4<r6/f<-0.3, 1.15<a/b<1.50, 1.7<d4 + d6<2.2, 1.63<(n3+n4)/2<1.74, 0.83<(v1+v3+v4)/vt<0.85, wherein f is a focal distance of the entire lens group with respect to e-line, and f1,f2,f3,f4 are focal distances of e-line of the first, second, third and fourth lenses, r6 is a radius of curvature of a sixth plane, a is (d1+d2+d3)/f, b is (d4+d5+d6)/f, n3 is a refractive index of e-line of the third lens, n4 is a refractive index of e-line of the fourth lens, v1 is an Abbe number of d-line of the first lens, v3 is an Abbe number of d-line of the third lens, v4 is an Abbe number of d-line of the fourth lens, and vt is an Abbe number of d-line of the entire lens group.
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