| 摘要 |
An object of this invention is to provide a lens array in which the amount of light reaching the image forming surface is large and the variation in the amount of light is small. In order to achieve this object, the lens array comprises cylindrical graded index lenses of radius r0 wherein the refractive index continuously decreases from the center of the lens toward the periphery, said cylindrical graded index lenses are arranged in one line or plural lines with array pitch 2R, if R is R>=r0>=0.8R and if the refractive index profile of each graded index lens is approximated by n(r)<2>=n0<2>{1-(g.r)<2>}, the overlapping degree m defined by m=X0/2R satisfies 1.05<=m<=1.2, wherein, said r is the distance from the optical axis, n(r) is refractive index at the distance r from the optical axis, n0 is the refractive index at the center, g is the refractive index profile constant, X0 is the radius of the field of view (X0=r1 cos(Z0pi/P), r1 is the effective radius of the graded index lens, Z0 is the length of the graded index lenses, and P is the period length of the graded index lenses namely P=2pi/g.
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