ZOOM LENS SYSTEM, IMAGING APPARATUS AND METHOD FOR VARYING FOCAL LENGTH

Abstract

Providing a zoom lens system capable of obtaining higher optical performance, an imaging apparatus, and a method for varying a focal length of the zoom lens system. The system includes, in order from an object: a first lens group having negative refractive power; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power. Upon zooming from a wide-angle end state to a telephoto end state, each lens group moves along an optical axis such that a distance between the first and second lens groups decreases, a distance between the second and third lens groups increases, and the distance between the third and fourth lens groups decreases; and the first lens group includes a negative lens, at least one lens in the negative lens includes an aspherical surface, and the negative lens satisfies given conditionals.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a lens configuration of a zoom lens system according to Example 1 of a first embodiment together with a zooming trajectory of each lens group.

FIGS. 2A, 2B and 2C are graphs showing various aberrations of the zoom lens system according to Example 1 of the first embodiment in a wide-angle end state, in an intermediate focal length state, in a telephoto end state, respectively.

FIG. 3 is a diagram showing a lens configuration of a zoom lens system according to Example 2 of the first embodiment together with a zooming trajectory of each lens group.

FIGS. 4A, 4B and 4C are graphs showing various aberrations of the zoom lens system according to Example 2 of the first embodiment in a wide-angle end state, in an intermediate focal length state, in a telephoto end state, respectively.

FIG. 5 is a diagram showing a lens configuration of a zoom lens system according to Example 3 of the first embodiment together with a zooming trajectory of each lens group.

FIGS. 6A, 6B and 6C are graphs showing various aberrations of the zoom lens system according to Example 3 of the first embodiment in a wide-angle end state, in an intermediate focal length state, in a telephoto end state, respectively.

FIG. 7 is a diagram showing a lens configuration of a zoom lens system according to Example 4 of the first embodiment together with a zooming trajectory of each lens group.

FIGS. 8A, 8B and 8C are graphs showing various aberrations of the zoom lens system according to Example 4 of the first embodiment in a wide-angle end state, in an intermediate focal length state, in a telephoto end state, respectively.

FIG. 9 is a diagram showing a lens configuration of a zoom lens system according to Example 5 of a second embodiment together with a zooming trajectory of each lens group.

FIGS. 10A, 10B and 10C are graphs showing various aberrations of the zoom lens system according to Example 5 of the second embodiment in a wide-angle end state, in an intermediate focal length state, in a telephoto end state, respectively.

FIG. 11 is a diagram showing a lens configuration of a zoom lens system according to Example 6 of the second embodiment together with a zooming trajectory of each lens group.

FIGS. 12A, 12B and 12C are graphs showing various aberrations of the zoom lens system according to Example 6 of the second embodiment in a wide-angle end state, in an intermediate focal length state, in a telephoto end state, respectively.

FIG. 13 is a diagram showing a lens configuration of a zoom lens system according to Example 7 of the second embodiment together with a zooming trajectory of each lens group.

FIGS. 14A, 14B and 14C are graphs showing various aberrations of the zoom lens system according to Example 7 of the second embodiment in a wide-angle end state, in an intermediate focal length state, in a telephoto end state, respectively.

FIG. 15 is a diagram showing a lens configuration of a zoom lens system according to Example 8 of the second embodiment together with a zooming trajectory of each lens group.

FIGS. 16A, 16B and 16C are graphs showing various aberrations of the zoom lens system according to Example 8 of the second embodiment in a wide-angle end state, in an intermediate focal length state, in a telephoto end state, respectively.

FIG. 17 is a diagram showing a lens configuration of a zoom lens system according to Example 9 of the second embodiment together with a zooming trajectory of each lens group.

FIGS. 18A, 18B and 18C are graphs showing various aberrations of the zoom lens system according to Example 9 of the second embodiment in a wide-angle end state, in an intermediate focal length state, in a telephoto end state, respectively.

FIG. 19 is a schematic diagram showing an imaging apparatus using a zoom lens system according to Example 1.

Claims

1. A zoom lens system comprising, in order from an object: a first lens group having negative refractive power;a second lens group having positive refractive power;a third lens group having negative refractive power; anda fourth lens group having positive refractive power;wherein upon zooming from a wide-angle end state to a telephoto end state, each lens group moves along an optical axis such that a distance between the first lens group and the second lens group decreases, a distance between the second lens group and the third lens group increases, and the distance between the third lens group and the fourth lens group decreases; andthe first lens group includes a negative lens, at least one lens in the negative lens includes an aspherical surface, and the negative lens satisfies the following conditional expressions: 30≦νd1≦71when 30≦νd1≦36, −0.013×νd1+2.083≦nd1≦1.7,when 36≦νd1≦41, −0.013×νd1+2.083≦nd1≦−0.004×νd1+1.844,when 41≦νd1≦51, −0.004×νd1+1.714≦nd1≦−0.004×νd1+1.844,when 51≦νd1≦61, −0.0015×νd1+1.5865≦nd1≦−0.004×νd1+1.844,when 61≦νd1≦71, −0.0015×νd1+1.5865≦nd1≦0.009×νd1+2.149

2. The zoom lens system according to claim 1, wherein the second lens group includes a positive lens, and the positive lens in the second lens group satisfies the following conditional expressions: 30≦νd2≦71when 30≦νd2≦36, −0.013×νd2+2.083≦nd2≦1.7,when 36≦νd2≦41, −0.013×νd2+2.083≦nd2≦−0.004×νd2+1.844,when 41≦νd2≦51, −0.004×νd2+1.714≦nd2≦−0.004×νd2+1.844,when 51≦νd2≦61, −0.0015×νd2+1.5865≦nd2≦−0.004×νd2+1.844,when 61≦νd2≦71, −0.0015×νd2+1.5865≦nd2≦0.009×νd2+2.149

3. The zoom lens system according to claim 2, wherein the fourth lens group includes a positive lens, and the positive lens in the fourth lens group satisfies the following conditional expressions: 30≦νd4≦71when 30≦νd4≦36, −0.013×νd4+2.083≦nd4≦1.7,when 36≦νd4≦41, −0.013×νd4+2.083≦nd4≦−0.004×νd4+1.844,when 41≦νd4≦51, −0.004×νd4+1.714≦nd4≦−0.004×νd4+1.844,when 51≦νd4≦61, −0.0015×νd4+1.5865≦nd4≦−0.004×νd4+1.844,when 61≦νd4≦71, −0.0015×νd4+1.5865≦nd4≦0.009×νd4+2.149

4. The zoom lens system according to claim 1, wherein the fourth lens group includes a positive lens, and the positive lens in the fourth lens group satisfies the following conditional expressions: 30≦νd4≦71when 30≦νd4≦36, −0.013×νd4+2.083≦nd4≦1.7,when 36≦νd4≦41, −0.013×νd4+2.083≦nd4≦−0.004×νd4+1.844,when 41≦νd4≦51, −0.004×νd4+1.714≦nd4≦−0.004×νd4+1.844,when 51≦νd4≦61, −0.0015×νd4+1.5865≦nd4≦−0.004×νd4+1.844,when 61≦νd4≦71, −0.0015×νd4+1.5865≦nd4≦0.009×νd4+2.149

5. The zoom lens system according to claim 1, wherein the first lens group includes, in order from the object, a negative meniscus lens having convex surface facing the object, a negative lens having a concave surface facing an image, and a positive lens having a convex surface facing the object.

6. The zoom lens system according to claim 1, wherein the following conditional expression is satisfied: 0.7≦(−f1)/fw≦1.7

7. The zoom lens system according to claim 1, wherein at least one of an image side surface of the negative meniscus lens or the image side surface of the negative lens in the first lens group is an aspherical surface, and the following conditional expression is satisfied: 0.32≦Rasp/(−f1)≦1.0

8. The zoom lens system according to claim 1, wherein the second lens group consists of two positive lenses and a negative lens.

9. The zoom lens system according to claim 1, wherein the third lens group consists of a positive lens and a negative lens.

10. The zoom lens system according to claim 1, wherein an aperture stop is disposed in the vicinity of the third lens group, and moved together with the third lens group in a body.

11. The zoom lens system according to claim 1, wherein the fourth lens group consists of two positive lenses and a negative lens.

12. The zoom lens system according to claim 1, wherein the second lens group is moved together with the fourth lens group in a body upon zooming from the telephoto end state to the wide-angle end state.

13. The zoom lens system according to claim 1, wherein the following conditional expression is satisfied: 1.0≦f2/fw≦2.3

14. The zoom lens system according to claim 1, wherein the following conditional expression is satisfied: 0.8≦(−f3)/fw≦3.0

15. The zoom lens system according to claim 1, wherein the following conditional expression is satisfied: 0.8≦f4/fw≦2.0

16. The zoom lens system according to claim 1, wherein the fourth lens group includes a plastic aspherical lens.

17. The zoom lens system according to claim 16, wherein the following conditional expression is satisfied: 1.5≦f4/fw≦2.9

18. The zoom lens system according to claim 16, wherein the plastic aspherical lens in the fourth lens group satisfies the following conditional expression: |f4/fP|≦0.9

19. An imaging apparatus equipped with a zoom lens system, said zoom lens system comprising, in order from an object: a first lens group having negative refractive power;a second lens group having positive refractive power;a third lens group having negative refractive power; anda fourth lens group having positive refractive power;wherein upon zooming from a wide-angle end state to a telephoto end state, each lens group moves along an optical axis such that a distance between the first lens group and the second lens group decreases, a distance between the second lens group and the third lens group increases, and the distance between the third lens group and the fourth lens group decreases; andthe first lens group includes a negative lens, at least one lens in the negative lens includes an aspherical surface, and the negative lens satisfies the following conditional expressions: 30≦νd1≦71when 30≦νd1≦36, −0.013×νd1+2.083≦nd1≦1.7,when 36≦νd1≦41, −0.013×νd1+2.083≦nd1≦−0.004×νd1+1.844,when 41≦νd1≦51, −0.004×νd1+1.714≦nd1≦−0.004×νd1+1.844,when 51≦νd1≦61, −0.0015×νd1+1.5865≦nd1≦−0.004×νd1+1.844,when 61≦νd1≦71, −0.0015×νd1+1.5865≦nd1≦0.009×νd1+2.149

20. A zoom lens system comprising, in order from an object: a first lens group having negative refractive power;a second lens group having positive refractive power;a third lens group having negative refractive power; anda fourth lens group having positive refractive power;wherein upon zooming from a wide-angle end state to a telephoto end state, each lens group moves along an optical axis such that a distance between the first lens group and the second lens group decreases, a distance between the second lens group and the third lens group increases, and a distance between the third lens group and the fourth lens group decreases; andthe first lens group includes a negative lens, and the negative lens satisfies the following conditional expressions: 30≦νd1≦71when 30≦νd1≦36, −0.013×νd1+2.083≦nd1≦1.7,when 36≦νd1≦41, −0.013×νd1+2.083≦nd1≦−0.004×νd1+1.844,when 41≦νd1≦51, −0.004×νd1+1.714≦nd1≦−0.004×νd1+1.844,when 51≦νd1≦61, −0.0015×νd1+1.5865≦nd1≦−0.004×νd1+1.844,when 61≦νd1≦71, −0.0015×νd1+1.5865≦nd1≦0.009×νd1+2.149

21. The zoom lens system according to claim 20, wherein the fourth lens group includes a positive lens, and the positive lens in the fourth lens group satisfies the following conditional expressions: 30≦νd4≦71when 30≦νd4≦36, −0.013×νd4+2.083≦nd4≦1.7,when 36≦νd4≦41, −0.013×νd4+2.083≦nd4≦−0.004×νd4+1.844,when 41≦νd4≦51, −0.004×νd4+1.714≦nd4≦−0.004×νd4+1.844,when 51≦νd4≦61, −0.0015×νd4+1.5865≦nd4≦−0.004×νd4+1.844,when 61≦νd4≦71, −0.0015×νd4+1.5865≦nd4≦0.009×νd4+2.149

22. The zoom lens system according to claim 20, wherein the following conditional expression is satisfied: 0.7≦(−f1)/fw≦1.7

23. The zoom lens system according to claim 20, wherein the following conditional expression is satisfied: 1.0≦f2/fw≦2.3

24. The zoom lens system according to claim 20, wherein the following conditional expression is satisfied: 0.8≦f4/fw≦2.0

25. A zoom lens system comprising, in order from an object: a first lens group having negative refractive power;a second lens group having positive refractive power;a third lens group having negative refractive power; anda fourth lens group having positive refractive power;wherein upon zooming from a wide-angle end state to a telephoto end state, each lens group moves along an optical axis such that a distance between the first lens group and the second lens group decreases, a distance between the second lens group and the third lens group increases, and a distance between the third lens group and the fourth lens group decreases; andthe first lens group includes a negative lens, and the negative lens satisfies the following conditional expressions: 30≦νd1≦71when 30≦νd1≦36, −0.013×νd1+2.083≦nd1≦1.7,when 36≦νd1≦41, −0.013×νd1+2.083≦nd1≦−0.004×νd1+1.844,when 41≦νd1≦51, −0.004×νd1+1.714≦nd1≦−0.004×νd1+1.844,when 51≦νd1≦61, −0.0015×νd1+1.5865≦nd1≦−0.004×νd1+1.844,when 61≦νd1≦71, −0.0015×νd1+1.5865≦nd1≦0.009×νd1+2.149

26. The zoom lens system according to claim 25, wherein the following conditional expression is satisfied: 0.7≦(−f1)/fw≦1.7

27. The zoom lens system according to claim 25, wherein the following conditional expression is satisfied: 1.0≦f2/fw≦2.3

28. The zoom lens system according to claim 25, wherein the following conditional expression is satisfied: 0.8≦f4/fw≦2.0

29. A method for forming an image of an object and varying a focal length of a zoom lens system that comprises, in order from the object, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, the method comprising steps of: moving each lens group along an optical axis such that a distance between the first lens group and the second lens group decreases, a distance between the second lens group and the third lens group increases, and a distance between the third lens group and the fourth lens group decreases upon zooming from a wide-angle end state to a telephoto end state;providing the first lens group including a negative lens;providing an aspherical surface on at least one lens in the negative lens in the first lens group; andsatisfying the following conditional expressions: 30≦νd1≦71when 30≦νd1≦36, −0.013×νd1+2.083≦nd1≦1.7,when 36≦νd1≦41, −0.013×νd1+2.083≦nd1≦−0.004×νd1+1.844,when 41≦νd1≦51, −0.004×νd1+1.714≦nd1≦−0.004×νd1+1.844,when 51≦νd1≦61, −0.0015×νd1+1.5865≦nd1≦−0.004×νd1+1.844,when 61≦νd1≦71, −0.0015×νd1+1.5865≦nd1≦0.009×νd1+2.149

30. The method according to claim 29, further comprising steps of: providing the second lens group including a positive lens, andsatisfying the following conditional expressions: 30≦νd2≦71when 30≦νd2≦36, −0.013×νd2+2.083≦nd2≦1.7,when 36≦νd2≦41, −0.013×νd2+2.083≦nd2≦−0.004×νd2+1.844,when 41≦νd2≦51, −0.004×νd2+1.714≦nd2≦−0.004×νd2+1.844,when 51≦νd2≦61, −0.0015×νd2+1.5865≦nd2≦−0.004×νd2+1.844,when 61≦νd2≦71, −0.0015×νd2+1.5865≦nd2≦0.009×νd2+2.149

31. The method according to claim 29, further comprising steps of: providing the fourth lens group including a positive lens; andsatisfying the following conditional expressions: 30≦νd4≦71when 30≦νd4≦36, −0.013×νd4+2.083≦nd4≦1.7,when 36≦νd4≦41, −0.013×νd4+2.083≦nd4≦−0.004×νd4+1.844,when 41≦νd4≦51, −0.004×νd4+1.714≦nd4≦−0.004×νd4+1.844,when 51≦νd4≦61, −0.0015×νd4+1.5865≦nd4≦−0.004×νd4+1.844,when 61≦νd4≦71, −0.0015×νd4+1.5865≦nd4≦0.009×νd4+2.149

32. A method for forming an image of an object and varying a focal length of a zoom lens system that comprises, in order from the object, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, the method comprising steps of: moving each lens group along an optical axis such that a distance between the first lens group and the second lens group decreases, a distance between the second lens group and the third lens group increases, and a distance between the third lens group and the fourth lens group decreases upon zooming from a wide-angle end state to a telephoto end state;providing the first lens group including a negative lens;satisfying the following conditional expressions: 30≦νd1≦71when 30≦νd1≦36, −0.013×νd1+2.083≦nd1≦1.7,when 36≦νd1≦41, −0.013×νd1+2.083≦nd1≦−0.004×νd1+1.844,when 41≦νd1≦51, −0.004×νd1+1.714≦nd1≦−0.004×νd1+1.844,when 51≦νd1≦61, −0.0015×νd1+1.5865≦nd1≦−0.004×νd1+1.844,when 61≦νd1≦71, −0.0015×νd1+1.5865≦nd1≦0.009×νd1+2.149

33. The method according to claim 32, further comprising steps of: providing the fourth lens group including a positive lens; andsatisfying the following conditional expressions: 30≦νd4≦71when 30≦νd4≦36, −0.013×νd4+2.083≦nd4≦1.7,when 36≦νd4≦41, −0.013×νd4+2.083≦nd4≦−0.004×νd4+1.844,when 41≦νd4≦51, −0.004×νd4+1.714≦nd4≦−0.004×νd4+1.844,when 51≦νd4≦61, −0.0015×νd4+1.5865≦nd4≦−0.004×νd4+1.844,when 61≦νd4≦71, −0.0015×νd4+1.5865≦nd4≦0.009×νd4+2.149

34. A method for forming an image of an object and varying a focal length of a zoom lens system that comprises, in order from the object, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, the method comprising steps of: moving each lens group along an optical axis such that a distance between the first lens group and the second lens group decreases, a distance between the second lens group and the third lens group increases, and a distance between the third lens group and the fourth lens group decreases upon zooming from a wide-angle end state to a telephoto end state;providing the first lens group including a negative lens;satisfying the following conditional expressions: 30≦νd1≦71when 30≦νd1≦36, −0.013×νd1+2.083≦nd1≦1.7,when 36≦νd1≦41, −0.013×νd1+2.083≦nd1≦−0.004×νd1+1.844,when 41≦νd1≦51, −0.004×νd1+1.714≦nd1≦−0.004×νd1+1.844,when 51≦νd1≦61, −0.0015×νd1+1.5865≦nd1≦−0.004×νd1+1.844,when 61≦νd1≦71, −0.0015×νd1+1.5865≦nd1≦0.009×νd1+2.149