| 摘要 |
In an optical lens system for use in combination with a bar code sensor, first and second meniscus lenses are arranged back to back along an optical axis on object and image sides, respectively, and are identical in configuration and optical charcteristics with each other. Each meniscus lens has effective aspherical surfaces defined by predetermined formulae. On the assumption that the first and the second meniscus lenses have the same refractive index, the optical lens system satisfies the following formulae: 0.25<(r1/r2)/(n/(n-1))<0.5. 1.2<f1/f<1.8, 0.3<D/f<0.6, and 1.0<K2, where r1 is representative of a radius of curvature measured at an apex of a first aspherical surface of each meniscus lens; r2, a radius of curvature measured at an apex of a second aspherical surface of each meniscus lens; n, the refractive index of the first meniscus lens; f, a combined focal length of a whole of the aspherical lens system, f1, a focal length of the first meniscus lens; D, a total length of the aspherical lens system; and K2, a coefficient of cone of the second aspherical surface.
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