| 摘要 |
An optical system includes, in order from an object side to an image side, a first lens unit of positive optical power, and a second lens unit of negative refractive power, wherein focusing from an infinitely distant object to a closest object is effected by moving the second lens unit toward the image side along an optical axis, and the second lens unit consists of one negative lens. Further, it is desirable that the following conditions are satisfied:where L1(lambd) is an aberration coefficient of longitudinal chromatic aberration of the first lens unit, T1(lambd) is an aberration coefficient of lateral chromatic aberration of the first lens unit, lambd is a wavelength of light, and &ngr;2 is an Abbe number of material of the negative lens of the second lens unit.
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