| 摘要 |
<p>PROBLEM TO BE SOLVED: To retain a best focus position with respect to an image pickup element position when performing a soft focus in a zoom lens having a soft focus function.SOLUTION: A spherical aberration adjustment device is composed of, in order from an object side: a first group that is stationary during varying a magnification, and has a positive refractive index; a second group that moves for varying the magnification, and has a negative refractive power; a third group that moves for correcting a change in an image plane accompanied by the varying magnification, and has the negative refractive power; and a fourth group that is stationary during varying the magnification, and has the positive refractive power. In the fourth group, the spherical aberration adjustment device has a spherical aberration adjustment group movable when adjusting a spherical aberration, and satisfies the following expression. 0.7<|βmv.βim|<10<fmv/fr<4, whereβmv indicates a lateral magnification of the spherical aberration adjustment group,βim indicates a lateral magnification of a group on an image side further than the spherical aberration adjustment group, fr indicates a focal length of the fourth group, and fmv indicates a focal length of the spherical aberration adjustment group.</p> |
