| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact and lightweight optical system for successfully correcting various aberrations such as chromatic aberrations, and also to provide an optical instrument having the optical system. SOLUTION: The optical system comprises, in order from an object side to an image side, a first lens group L1 having positive refractive power, a diaphragm SP, and a second lens group L2. The first lens group includes a first a lens group L1a having positive refractive power and a first b lens group L1b having negative refractive power, moving on an optical axis in focusing. The first b lens group has at least one negative lens and one positive lens 1bp. The optical system satisfies a condition of 0.020<θgF1-0.6438+0.001682×νd1<0.100, whereinθgF1 is the partial dispersion ratio of the material of the positive lens 1bp, andνd1 is the Abbe number of the material of the positive lens 1bp. COPYRIGHT: (C)2011,JPO&INPIT |
