DISTRIBUTED REFRACTIVE INDEX TYPE LENS

PURPOSE:To obtain the distributed refractive index type lens which has sufficiently small spherical and coma aberrations and is easily polished and assembled by allowing the lens to meet specific requirements. CONSTITUTION:The lens 1 is made of a transparent medium, such as glass and synthetic resin, having a refractive index N(Z) at distance Z from and end surface along an optical axis; one end surface 2 which is comprised of transparent medium expressed by the equation: N(Z)=Noo+No1Z is plane and the other end surface is an axially symmetrical surface with a radius 1/C1 of curvature. This lens has a refractive index distribution wherein the refractive index varies from the center 4 of the spherical end surface 3 to the optical axis 5 continuously according to expressions (1)-(3) and is constant in the surface perpendicular to an optical axis. When parallel luminous flux 6 is made incident from the side of the spherical end surface 3 of the lens 1 the flux is converted on a point 7 with small aberrations and a light source such as a semiconductor laser is arranged at the point 7 to obtain high-precision parallel projection luminous flux. In the expression, Noo and No1 are distribution constants, and C1 and C2 are curvature values of both lens surfaces; the surface is convex when C1>0 or concave when C1