Zooming optical system, optical apparatus and method for manufacturing zooming optical system
A compact zooming optical system having high zooming ratio and superb optical performance and a manufacturing method are provided. The zooming optical system includes, in order from an object along the optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having negative refractive power. Upon zooming from a wide angle end state to a telephoto end state, respective distances between the first lens group and the second lens group, between the second lens group and the third lens group, between the third lens group and the fourth lens group, and between the fourth lens group and the fifth lens group, are varied.
1. A zooming optical system comprising, in order from an object side along an optical axis:
a first lens group having positive refractive power,
a second lens group having negative refractive power,
a third lens group having positive refractive power, and
a fourth lens group having negative refractive power, and
a fifth lens group having negative refractive power, and
wherein upon zooming from a wide angle end state to a telephoto end state a distance between said first lens group and said second lens group, a distance between said second lens group and said third lens group, a distance between said third lens group and said fourth lens group, and a distance between said fourth lens group and said fifth lens group are respectively varied,
wherein the following conditional expression is satisfied:
3.532≦(− f 5)/ fw ≦7.479
where f5 denotes a focal length of the fifth lens group and fw denotes a focal length of the zooming optical system in the wide angle end state.
2. The zooming optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.40< f 5/ f 4<4.20
where f4 denotes a focal length of the fourth lens group.
3. The zooming optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.88<(− f 5)/ f 3<8.20
where f3 denotes a focal length of the third lens group.
4. The zooming optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.066< R 5/ f 5<0.600
where R5 denotes curvature radius of a lens surface in the fifth lens group which is concave facing the object side and whose curvature radius is smallest in absolute value.
5. The zooming optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.066< R 5/ f 5<0.600
where R5 denotes curvature radius of a lens surface in said fifth lens group which is concave facing the object side and whose curvature radius is smallest in absolute value; and
wherein said fifth lens group has a cemented lens, and said lens surface in said fifth lens group which is concave facing the object side and whose curvature radius is smallest in absolute value, is a cemented surface between two lens elements of the cemented lens.
6. The zooming optical system according to claim 1 , wherein, upon zooming from the wide angle end state to the telephoto end state, a distance between the third lens group and the fourth lens group increases from the wide angle end state to an intermediate focal length state and decreases from the intermediate focal length state to the telephoto end state.
7. The zooming optical system according to claim 1 , wherein, upon zooming from the wide angle end state to the telephoto end state, a distance between the fourth lens group and the fifth lens group decreases from the wide angle end state to an intermediate focal length state and increases from the intermediate focal length state to the telephoto end state.
8. The zooming optical system according to claim 1 , wherein, upon zooming from the wide angle end state to the telephoto end state, the third lens group and the fifth lens group are moved in a body.
9. The zooming optical system according to claim 1 , wherein, upon zooming from the wide angle end state to the telephoto end state, a distance between the first lens group and the second lens group increases and a distance between the second lens group and the third lens group decreases.
10. The zooming optical system according to claim 1 , wherein said fifth lens group has an aspherical surface.
11. The zooming optical system according to claim 1 , wherein said fifth lens group has an aspherical surface, and
said aspherical surface is the most object side surface in said fifth lens group.
12. The zooming optical system according to claim 1 , wherein an aperture stop is provided inside of or adjacent to said third lens group.
13. The zooming optical system according to claim 1 , wherein an aperture stop is provided inside of or adjacent to said third lens group, and
upon zooming from the wide angle end state to the telephoto end state said aperture stop is moved together with said third lens group in a body.
14. An optical apparatus equipped with the zooming optical system according to claim 1 .
15. A method for manufacturing a zooming optical system comprising steps of
disposing, in order from an object side along an optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having negative refractive power, such that, upon zooming from a wide angle end state to a telephoto end state, a distance between said first lens group and said second lens group, a distance between said second lens group and said third lens group, a distance between said third lens group and said fourth lens group and a distance between said fourth lens group and said fifth lens group are respectively varied; and
satisfying the following conditional expression:
3.532≦(− f 5)/ fw≦ 7.479
where f5 denotes a focal length of the fifth lens group and fw denotes a focal length of the zooming optical system in the wide angle end state.