Patent ID: 7012721

Claim:
An optical imaging system comprising: a rod lens array comprising a plurality of rod lenses having a refractive index distribution in a radial direction that are arranged in two rows with their optical axes in parallel, and a manuscript plane and an image plane that are located on opposite sides of the rod lens array, wherein the refractive index distribution of the rod lenses is expressed by n ( r ) 2 =n 0 2 ·{1−( g·r ) 2 +h 4 ·( g·r ) 4 +h 6 ·( g·r ) 6 +h 8 ·( g·r ) 8 } Eq. 1 where r is a radial distance from an optical axis of the rod lenses, n 0 is a refractive index on the optical axis of the rod lenses, and g, h 4 , h 6 and h 8 are refractive index distribution coefficients, when h 4 is an x coordinate, h 6 is a y coordinate, and h 8 is a z coordinate in a three-dimensional Cartesian coordinate system, a locus of the refractive index distribution coefficients h 4 , h 6 and h 8 is a spheroid, and the spheroid is defined by a vector X* that is expressed by X * =( x, y, z )= O*+k A A*+k B B*+k C C* Eq. 2 where O* is a vector from an origin of the Cartesian coordinate system to a center of the spheroid, A*, B* and C* are vectors in the directions of a major axis, a mean axis and a minor axis of the spheroid, respectively, and k A , k B and k C satisfy k A 2 +k B 2 +k C 2 ≦1.