Collimator lens

摘要

A collimator lens meets conditions that: (i) at least the outgoing surface is spherical; (ii) the lens comprises at least an index-varying region in which the refractive index varies in the axial direction but does not vary in the direction perpendicular to the axial direction, and a constant index region all over which the refractive index is fixed; (iii) the point having the maximum refractive index noo in the index-varying region is located at an apex of the profile of the lens; (iv) when the refractive index n(Z) on the optical axis at a distance Z from the apex is represent by n(Z)=noo+n1Z+n2Z2, noo is within the range of 1.50 to 1.77, n1 within the range of -0.14 to -0.02 mm-1 and n2 within the range of -0.03 to +0.03 mm-2; and (v) the inded-varying region is formed in the range of Z=0 to at least a depth d represented by an equation d=D2/{4R(1+ 2ROOT 1-(D/2R)2)} where D is the aperture of the lens and R is the radius of curvature of the lens surface which includes the point having the maximum refractive index noo.