| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical system with a large aperture ratio, which is well corrected for aberrations including chromatic aberration, spherical aberration, and field curvature.SOLUTION: An optical system includes, in order from the object side to the image side, a first lens group L1 having positive refractive power, an aperture stop SP, and a second lens group L2, where the first lens group includes two or more positive lenses and one or more negative lenses. A refractive index and an Abbe number Ndi, &ngr;di of a material of one of the positive lenses of the first lens group and maximum and minimum Abbe numbers max(&ngr;di), min(&ngr;di) of materials of positive lenses of the first lens group are each set appropriately. |
