| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical system which can excellently correct secondary spectrum of axial chromatic aberration and reduce generation of color flare, and by which a high optical performance can be obtained from an on-axis up to a periphery of an image plane. <P>SOLUTION: An optical system has a negative lens group consisting of one or more negative lenses disposed closest to an object and a positive lens group of positive refractive power consisting of a plurality of lenses disposed on an image side of the negative lens group. Assuming that some of the plurality of lenses constituting the positive lens group are LAj(j=1, 2...) in order from an object side and an abnormal partial dispersion ratio of material of the lenses LAj is ΔθgFAj, a conditional expression ΔθgFAj>0.0025 is satisfied. Assuming that one or more negative lenses are LNi(i=1, 2...) in order from an object side, a focal distance fni of the negative lens LNi, a refraction index Nni of the material, a focal distance fAj of the lens LAj, a refraction index of the material of the lens LAj, an Abbe number, partial dispersion ratios NAj, νdAj, θgFAj, and a focal distance f of the entire system are properly set, respectively. <P>COPYRIGHT: (C)2013,JPO&INPIT |
