Patent ID: 7184222

Claim:
An original reading lens, comprising: a four-group, five-element lens configuration including three positive lenses and two negative lenses, wherein the positive lenses comprise a glass material of low dispersion, and the negative lenses comprise a glass material of high dispersion, a partial dispersion qgd is defined by the equation qgd=(ng−nd)/(nF−nc) by a refractive index of d line (587.56 nm) nd, a refractive index of c line (656.27 nm) nc, a refractive index of F line (486.13 nm) nF, and a refractive index of g line (435.83 nm) ng, a straight line connecting a coordinate point of a reference glass material K 7 , K 7 (qgd, vd) and a coordinate point of a reference glass material F 2 , F 2 (qgd, vd) on a plane with a coordinate system including the partial dispersion qgd and an Abbe number vd as two orthogonal axes is adopted as a reference line, and a partial dispersion deviation, δqgd which is the deviation from the reference line of the partial dispersion qgd of the material, is positive in one or more positive lens.