| 摘要 |
PROBLEM TO BE SOLVED: To provide an inner focus type imaging optical system which is excellent in performance, has a wide angle of view and a large diameter, and is compact and light weight.SOLUTION: The imaging optical system comprises an aperture stop S, a first lens group 1G arranged on the object side of the aperture stop S, and a positive second lens group 2G arranged on the image side of the aperture stop S. The first lens group has a negative lens in the position closest to the object side, and the second lens group comprises, in order from the object side, a positive second-F lens group 2FG and a negative second-R lens group 2RG. The first lens group, the aperture stop, and the second-F lens group are fixed, and only the second-R lens group is displaced in the optical axis direction to perform focusing. The magnification M2R of the second-R lens group when focusing at infinity satisfies the following conditional expression: (1) 0.50<|1-M2R|<3.00. |
