| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical system that has satisfactorily corrected aberration while reducing weight and that is less affected by manufacturing error of an aspheric face. <P>SOLUTION: The optical system comprises, in order from an object side to an image side, a first lens group of positive refractive power, a second group of negative refractive power, and a third lens group of positive or negative refractive power. The first lens group comprises first and second partial lenses of positive refractive power. The first partial lens group includes a positive single lens, and at least its one face is aspheric. The second partial lens group includes a positive single lens and a negative single lens, and has a diffracting optical face including a diffracting optical element rotation-symmetrical with respect to the direction of an optical axis. The second lens group is a focus lens group movable in the direction of the optical axis. When the optical system focuses on infinite distance, paraxial lateral magnification βasph of a face closer to the image than a face arranged closest to the object in the aspheric face satisfies a predetermined condition. <P>COPYRIGHT: (C)2012,JPO&INPIT |
