| 摘要 |
A gradient index lens includes a first surface comprising a convex surface, a second surface comprising a convex surface, the convex surface of the second surface sharing the center of curvature with the convex surface of the first surface, and an index gradient N( rho ) formed in the medium of the lens. The index gradient N( rho ) is expressed as N( rho )=N0+N2 rho 2+N3 rho 3N4 rho 4+N5 rho 5+ . . . where N0 is the refractive index at the center of curvature, Nk (k=2, 3, 4, . . . ) are the index gradient coefficients, and rho is the distance from the center of curvature, and at least one of the index gradient coefficients Nk in which k>/=3 is greater than 0. The lens satisfies the following conditions: 1.45<N0<1.9 -0.4<N2f2<-0.2 where f is the focal length of the lens.
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