Variable magnification optical system, optical device, and production method for variable magnification optical system

1. A variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power; a second lens group having negative refractive power; an aperture stop; a third lens group having positive refractive power; a fourth lens group having positive refractive power; and a fifth lens group;

upon zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group, a distance between the second lens group and the third lens group, a distance between the third lens group and the fourth lens group and a distance between the fourth lens group and the fifth lens group being varied and a distance between the aperture stop and the fourth lens group being fixed;

the following conditional expressions being satisfied:

0.650<(− f 2)/ fw< 1.240

0.410< f 3/ f 4<1.000

where fw denotes a focal length of the variable magnification optical system in the wide-angle end state, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group.

2. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:

−0.050<( d 3 t−d 3 w )/ fw< 0.750

where fw denotes the focal length of the variable magnification optical system in the wide-angle end state, d3w denotes a distance from a lens surface on a most image side of the third lens group to a lens surface on a most object side of the fourth lens group in the wide-angle end state, and d3t denotes a distance from the lens surface on the most image side of the third lens group to the lens surface on the most object side of the fourth lens group in the telephoto end state.

3. A variable magnification optical system according to claim 1 , wherein the first lens group is moved toward the object side upon zooming from the wide-angle end state to the telephoto end state.

4. A variable magnification optical system according to claim 1 , wherein the fifth lens group has positive refractive power.

5. A variable magnification optical system according to claim 1 , wherein a distance between the first lens group and the second lens group is increased upon zooming from the wide-angle end state to the telephoto end state.

6. A variable magnification optical system according to claim 1 , wherein a distance between the second lens group and the third lens group is decreased upon zooming from the wide-angle end state to the telephoto end state.

7. A variable magnification optical system according to claim 1 , wherein a distance between the fourth lens group and the fifth lens group is increased upon zooming from the wide-angle end state to the telephoto end state.

8. A variable magnification optical system according to claim 1 , wherein the fifth lens group is fixed in a position upon zooming from the wide-angle end state to the telephoto end state.

9. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:

4.000<( TLt−TLw )/ fw< 7.000

where fw denotes the focal length of the variable magnification optical system in the wide-angle end state, TLw denotes a distance from a lens surface on a most object side of the first lens group to an image plane in the wide-angle end state, and TLt denotes a distance from the lens surface on the most object side of the first lens group to the image plane in the telephoto end state.

10. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:

−0.010<( d 3 t−d 3 w )/ ft< 0.130

where ft denotes a focal length of the variable magnification optical system in the telephoto end state, d3w denotes a distance from a lens surface on a most image side of the third lens group to a lens surface on a most object side of the fourth lens group in the wide-angle end state, and d3t denotes a distance from the lens surface on the most image side of the third lens group to the lens surface on the most object side of the fourth lens group in the telephoto end state.

11. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:

0.300< f 1/ ft< 0.555

where ft denotes a focal length of the variable magnification optical system in the telephoto end state and f1 denotes a focal length of the first lens group.

12. An optical apparatus comprising a variable magnification optical system according to claim 1 .

13. A method for manufacturing a variable magnification optical system, comprising:

arranging, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an aperture stop, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group;

the arranging being such that, upon zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group, a distance between the second lens group and the third lens group, a distance between the third lens group and the fourth lens group and a distance between the fourth lens group and the fifth lens group are varied and a distance between the aperture stop and the fourth lens group is fixed; and

satisfying the following conditional expressions:

0.650<(− f 2)/ fw< 1.240

0.410< f 3/ f 4<1.000

where fw denotes a focal length of the variable magnification optical system in the wide-angle end state, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group.