Zoom lens, optical apparatus equipped therewith and method for manufacturing the zoom lens
A zoom lens ZL installed in a single-lens reflex digital camera 1 and the like includes, in order from an object side, a first lens group G 1 having positive refractive power, a second lens group G 2 having negative refractive power, and a rear lens group GR having positive refractive power. The second lens group G 2 includes at least one positive lens and a negative lens disposed adjacent to the object side of the positive lens having largest refractive power among the positive lenses. Each distance between lens groups varies upon zooming from a wide-angle end state and a telephoto end state. Thereby providing a zoom lens having excellent optical performance, an optical apparatus equipped the zoom lens, and a method for manufacturing the zoom lens.
1. A zoom lens comprising, in order from an object side:
a first lens group having positive refractive power;
a second lens group having negative refractive power; and
a rear lens group having positive refractive power;
the second lens group including at least one positive lens and a negative lens disposed adjacent to the object side of the positive lens having largest refractive power among the positive lenses,
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 varying, and a distance between the second lens group and the rear lens group varying, and
the following conditional expressions being satisfied:
0.80<( r 2+ r 1)/( r 2− r 1)<3.50
0.50<(− f 2)/ fw< 0.90
where r 1 denotes a radius of curvature of the object side lens surface of the negative lens in the second lens group, r 2 denotes a radius of curvature of the image side lens surface of the negative lens in the second lens group, fw denotes a focal length of the zoom lens in the wide-angle end state, and f 2 denotes a focal length of the second lens group.
2. The zoom lens according to claim 1 , wherein at least one portion of the second lens group moves along an optical axis upon focusing from infinity to a close object.
3. The zoom lens according to claim 1 , wherein the rear lens group includes, in order from the object side, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power.
4. The zoom lens according to claim 1 , wherein the rear lens group includes, in order from the object side, a third lens group having positive refractive power, and a fourth lens group having positive refractive power.
5. The zoom lens according to claim 1 , wherein the most image side lens surface of the second lens group is an aspherical surface.
6. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
2.00 <f 1/| f 4|<6.00
where f 1 denotes a focal length of the first lens group and f 4 denotes a focal length of the fourth lens group.
7. The zoom lens according to claim 1 , wherein a portion of the rear lens group moves in a direction including a component substantially perpendicular to the optical axis.
8. The zoom lens according to claim 1 , wherein at least a portion of the fourth lens group moves in a direction including a component substantially perpendicular to the optical axis.
9. The zoom lens according to claim 1 , wherein the most object side lens surface of the second lens group is an aspherical surface.
10. The zoom lens 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 rear lens group decreases.
11. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.30<(− f 2)/ BFw< 0.60
where f 2 denotes a focal length of the second lens group, and BFw denotes a back focal length in the wide-angle end state.
12. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.45 <fw/BFw< 0.80
where fw denotes a focal length of the zoom lens in the wide-angle end state, and BFw denotes a back focal length in the wide-angle end state.
13. An optical apparatus equipped with the zoom lens according to claim 1 .
14. A zoom lens comprising, in order from an object:
a first lens group having positive refractive power;
a second lens group having negative refractive power; and
a rear lens group having positive refractive power;
the second lens group including at least one positive lens and a negative lens disposed adjacent to the object side of the positive lens having largest refractive power among the positive lenses,
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 varying, and a distance between the second lens group and the rear lens group varying, and
the following conditional expressions being satisfied:
0.80<( r 2+ r 1)/( r 2− r 1)<3.50
0.30<(− f 2)/ BFw< 0.60
0.45 <fw/BFw< 0.80
where r 1 denotes a radius of curvature of the object side surface of the negative lens in the second lens group, r 2 denotes a radius of curvature of the image side surface of the negative lens in the second lens group, fw denotes a focal length of the zoom lens in the wide-angle end state, f 2 denotes a focal length of the second lens group, and BFw denotes a back focal length in the wide-angle end state.
15. The zoom lens according to claim 14 , wherein the following conditional expression is satisfied:
0.50<(− f 2)/ fw< 0.90
where fw denotes a focal length of the zoom lens in the wide-angle end state, and f 2 denotes a focal length of the second lens group.
16. The zoom lens according to claim 14 , wherein the rear lens group includes, in order from the object side, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power.
17. The zoom lens according to claim 14 , wherein the rear lens group includes, in order from the object side, a third lens group having positive refractive power, and a fourth lens group having positive refractive power.
18. The zoom lens according to claim 14 , wherein the following conditional expression is satisfied:
2.00 <f 1/| f 4|<6.00
where f 1 denotes a focal length of the first lens group and f 4 denotes a focal length of the fourth lens group.
19. An optical apparatus equipped with the zoom lens according to claim 14 .
20. A method for manufacturing a zoom lens that includes, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear lens group having positive refractive power, the method comprising steps of:
providing in the second lens group at least one positive lens and a negative lens disposed adjacent to the object side of the positive lens having largest refractive power among the positive lenses;
providing the first lens group, the second lens group and the rear lens group such that a distance between the first lens group and the second lens group varies, and a distance between the second lens group and the rear lens group varies upon zooming from a wide-angle end state to a telephoto end state;
providing the second lens group with satisfying the following conditional expressions:
0.80<( r 2+ r 1)/( r 2− r 1)<3.50
0.50<(− f 2)/ fw< 0.90
where r 1 denotes a radius of curvature of the object side lens surface of the negative lens in the second lens group, r 2 denotes a radius of curvature of the image side lens surface of the negative lens in the second lens group, fw denotes a focal length of the zoom lens in the wide-angle end state, and f 2 denotes a focal length of the second lens group.
21. The method according to claim 20 : further comprising a step of:
providing, in order from the object side, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power into the rear lens group.
22. The method according to claim 20 : further comprising a step of:
providing, in order from the object side, a third lens group having positive refractive power, and a fourth lens group having positive refractive power into the rear lens group.
23. The method according to claim 20 : further comprising a step of:
providing the fourth lens group with satisfying the following conditional expression:
2.00 <f 1/| f 4|<6.00
where f 1 denotes a focal length of the first lens group and f 4 denotes a focal length of the fourth lens group.
24. A method for manufacturing a zoom lens that includes, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear lens group having positive refractive power, the method comprising steps of:
providing in the second lens group at least one positive lens and a negative lens disposed adjacent to the object side of the positive lens having largest refractive power among the positive lenses;
providing the first lens group, the second lens group and the rear lens group such that a distance between the first lens group and the second lens group varies and a distance between the second lens group and the rear lens group varies, upon zooming from a wide-angle end state to a telephoto end state;
providing the second lens group with satisfying the following conditional expressions:
0.80<( r 2+ r 1)/( r 2− r 1)<3.50
0.30<(− f 2)/ BFw < 0.60
0.45 <fw/BFw < 0.80
where r 1 denotes a radius of curvature of the object side surface of the negative lens in the second lens group, r 2 denotes a radius of curvature of the image side surface of the negative lens in the second lens group, fw denotes a focal length of the zoom lens in the wide-angle end state, f 2 denotes a focal length of the second lens group, and BFw denotes a back focal length in the wide-angle end state.