| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical system having good optical performance over an entire screen by satisfactorily correcting a chromatic aberration such as a chromatic difference of magnification and axial chromatic aberration, which occur with a wider angle of view. <P>SOLUTION: The optical system includes, in order from an enlargement conjugate side to a reduction conjugate side via the largest air gap, a front group having negative refractive power and a rear group having positive refractive power. In the optical system, the followings are appropriately set: the focal length f<SB>n1</SB>of at least one negative lens out of negative lenses included in the front group; a refractive index, an Abbe number, and a partial dispersion ratio Nd<SB>n1</SB>, νd<SB>n1</SB>, and θgF<SB>n1</SB>of a material of at least the one negative lens, respectively; and a focal length F (focal length at a wide angle end when the optical system is a zoom lens) of the entire system. <P>COPYRIGHT: (C)2011,JPO&INPIT |
