| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging optical system that restricts a light beam exit angle while realizing a field angle of 65 degrees or more, and has a small size and satisfactory optical performance.SOLUTION: The imaging optical system comprises, in order from an object side to an image side, a first lens group L1 of positive refractive power and a second lens group L2 of negative refractive power. When focusing takes place from infinity to proximity, the first lens group L1 moves from the image side to the object side along an optical axis. The first lens group L1 comprises, in order from the object side to the image side: a first lens group front group L1F of negative refractive power, an aperture diaphragm S, and a first lens group rear group L1R of positive refractive power. The first lens group front group L1F has at least one positive lens and one negative lens. The second lens group L2 comprises, in order from the object side to the image side, a negative lens having the strong concave face oriented toward the image side, a negative meniscus lens having the convex face orientated toward the image side, and a positive lens. |
