| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an imaging optical system that is advantageous in sound isolation and dust prevention, can easily have a small size in a radial direction, and can easily secure optical performance, and provide an imaging apparatus using the imaging optical system. <P>SOLUTION: An imaging optical system includes, in order from an object side to an image plane side, a first lens group having a positive refractive power, a second lens group having a positive or negative refractive power, a third lens group having a positive refractive power, and an aperture stop disposed between an object side surface of the first lens group and an object side surface of the second lens group. The lens closest to the object side in the first lens group and the lens closest to the image side in the third lens group are constantly fixed. During focusing from a long distance to a short distance, only the second lens group moves along the optical axis. The third lens group includes a front sub lens group having a positive refractive power disposed on the object side and a rear sub lens group having a negative refractive power disposed on the image side, with the largest air interval on the optical axis in the third lens group between them. <P>COPYRIGHT: (C)2012,JPO&INPIT |
