Patent ID: 6078431
Filing Date: 2000-06-20
Classification: G02B

Abstract:
An object lens system comprising a lens made of a transparent medium with a refractive index distribution in a radial direction, whereina first surface of the lens is a convex spherical surface, and a second surface of the lens is a planar surface;the lens is arranged so that the convex spherical surface faces an object surface, and the planar surface faces an image surface;the equations1.0.ltoreq.R/r.sub.0 .ltoreq.1.6, andR/f.ltoreq.1.2are satisfied, wherein r.sub.0 is a radius of a portion of the lens that operates as a lens, measured from an optical axis of the lens, R is a curvature radius of the convex spherical surface, and f is a focal length of the lens;the lens is a rod lens, whose refractive index distribution is expressed byn(r).sup.2 =n.sub.0.sup.2 .multidot.{1-(g.multidot.r).sup.2 +h.sub.4 (g.multidot.r).sup.4 +h.sub.6 (g.multidot.r).sup.6 +h.sub.8 (g.multidot.r).sup.8 +. . . }wherein r is a distance in a radial direction from the optical axis of the rod lens, n.sub.0 is a refractive index on the optical axis of the rod lens, and g, h.sub.4, h.sub.6, h.sub.8, etc. are refractive index distribution coefficients; andL.sub.2 /r.sub.0 is in a range of L.sub.2 /r.sub.0 .ltoreq.0.37, wherein L.sub.2 is a distance between the planar surface of the lens and the image surface.