Patent ID: 8000026

Claim:
An optical system, comprising: a front unit having positive refractive power; an aperture stop; and a rear unit having positive or negative refractive power, in order from an object side to an image side, wherein the front unit has a positive lens Gp 1 and the rear unit has a negative lens Gn 1 , and when an Abbe number of a material of the positive lens Gp 1 with respect to a d-line is defined as νdp 1 , a partial dispersion ratio of the material of the positive lens with respect to a g-line and an F-line is defined as θgFp 1 , a refractive index and an Abbe number of a material of the negative lens Gn 1 with respect to a d-line are defined as Ndn 1 and νdn 1 , respectively, and a partial dispersion ratio of the material of the negative lens with respect to the g-line and the F-line is defined as θgFn 1 , satisfying the following conditions: 75<νdp1<99, 0.020< θgFp 1−0.6438+0.001682 ×νdp 1<0.100, 1.75<Ndn1<2.10, and 0.020< θgFn 1−0.6438+0.001682 ×νdn 1<0.100.