Patent ID: 7027236

Claim:
An original reading lens comprising: a four-group, five-element lens configuration including three positive lenses and two negative lenses; the four-group, five-element lens configuration including, in order from an object side, a first group having a positive first lens, a second group having negative refractive power in which a positive second lens and a negative third lens are cemented, a third group having a negative fourth lens, and a fourth group having a positive fifth lens, and an aperture stop disposed between the second group and the third group, wherein the positive lens is constructed by a glass material of low dispersion, and the negative lens is constructed by a glass material of high dispersion, a partial dispersion θgd is defined by θgd=(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 (θgd, υd) and a coordinate point of a reference glass material F 2 , F 2 (θgd, υd) on a plane with a coordinate system including the partial dispersion θgd and an Abbe number υd as orthogonal two axes is adopted as a reference line, and a partial dispersion deviation δθgd which is the deviation from the reference line of the partial dispersion θgd of the material is positive in one or more positive lens.