Zoom lens system and image pickup apparatus using the same

Abstract

A zoom lens system having, in order from an object side, a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; and a fourth lens unit having a positive refractive power, wherein during magnification change from a wide-angle end to a telephoto end, an interval between the first lens unit and the second lens unit, an interval between the second lens unit and the third lens unit and an interval between the third lens unit and the fourth lens unit change.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given below and the accompanying drawings, which are given by way of illustration only and thus are not limitative of the present invention, wherein:

FIGS. 1A to 1E are sectional views of Example 1 of the present invention along an optical axis, FIG. 1A shows an arrangement of lens units in a wide-angle end, FIGS. 1B, 1C and 1D show arrangements of the lens units in three states between the wide-angle end and a telephoto end, and FIG. 1E shows an arrangement of the lens units in the telephoto end, respectively;

FIGS. 2A to 2C are aberration diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration (CC) of magnification of Example 1 when focused on an infinite object, FIG. 2A shows aberrations in the wide-angle end, FIG. 2B shows aberrations in the state shown in FIG. 1C, and FIG. 2C shows aberrations in the telephoto end;

FIGS. 3A to 3E are sectional views of Example 2 of the present invention along an optical axis, FIG. 3A shows an arrangement of lens units' in a wide-angle end, FIGS. 3B, 3C and 3D show arrangements of the lens units in three states between the wide-angle end and a telephoto end, and FIG. 3E shows an arrangement of the lens units in the telephoto end, respectively;

FIGS. 4A to 4C are aberration diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration (CC) of magnification of Example 2 when focused on an infinite object, FIG. 4A shows aberrations in the wide-angle end, FIG. 4B shows aberrations in the state shown in FIG. 3C, and FIG. 4C shows aberrations in the telephoto end;

FIGS. 5A to 5E are sectional views of Example 3 of the present invention along an optical axis, FIG. 5A shows an arrangement of lens units in a wide-angle end, FIGS. 5B, 5C and 5D show arrangements of the lens units in three states between the wide-angle end and a telephoto end, and FIG. 5E shows an arrangement of the lens units in the telephoto end, respectively;

FIGS. 6A to 6C are aberration diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration (CC) of magnification of Example 3 when focused on an infinite object, FIG. 6A shows aberrations in the wide-angle end, FIG. 6B shows aberrations in the state shown in FIG. 5C, and FIG. 6C shows aberrations in the telephoto end;

FIGS. 7A to 7E are sectional views of Example 4 of the present invention along an optical axis, FIG. 7A shows an arrangement of lens units in a wide-angle end, FIGS. 7B, 7C and 7D show arrangements of the lens units in three states between the wide-angle end and a telephoto end, and FIG. 7E shows an arrangement of the lens units in the telephoto end, respectively;

FIGS. 8A to 8C are aberration diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration (CC) of magnification of Example 4 when focused on an infinite object, FIG. 8A shows aberrations in the wide-angle end, FIG. 8B shows aberrations in the state shown in FIG. 7C, and FIG. 8C shows aberrations in the telephoto end;

FIGS. 9A to 9E are sectional views of Example 5 of the present invention along an optical axis, FIG. 9A shows an arrangement of lens units in a wide-angle end, FIGS. 9B, 9C and 9D show arrangements of the lens units in three states between the wide-angle end and a telephoto end, and FIG. 9E shows an arrangement of the lens units in the telephoto end, respectively;

FIGS. 10A to 10C are aberration diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration (CC) of magnification of Example 5 when focused on an infinite object, FIG. 10A shows aberrations in the wide-angle end, FIG. 10B shows aberrations in the state shown in FIG. 9G, and FIG. 10C shows aberrations in the telephoto end;

FIGS. 11A to 11E are sectional views of Example 6 of the present invention along an optical axis, FIG. 11A shows an arrangement of lens units in a wide-angle end, FIGS. 11B, 11C and 11D show arrangements of the lens units in three states between the wide-angle end and a telephoto end, and FIG. 11E shows an arrangement of the lens units in the telephoto end, respectively;

FIGS. 12A to 12C are aberration diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration (CC) of magnification of Example 6 when focused on an infinite object, FIG. 12A shows aberrations in the wide-angle end, FIG. 12B shows aberrations in the state shown in FIG. 11C, and FIG. 12C shows aberrations in the telephoto end;

FIG. 13 is a front perspective view showing an appearance of an electronic camera to which a zoom lens system of the present invention is applied;

FIG. 14 is a rear view of the digital camera of FIG. 13; and

FIG. 15 is an explanatory view showing an arrangement of an optical system in the digital camera of FIG. 13.

Claims

1. A zoom lens system comprising, in order from an object side: a first lens unit having a positive refractive power;a second lens unit having a negative refractive power;a third lens unit having a positive refractive power; anda fourth lens unit having a positive refractive power,wherein the first lens unit comprises a negative lens element and a positive lens element in order from the object side;the second lens unit comprises a negative lens element and a positive lens element in order from the object side;the third lens unit comprises a positive lens element, a positive lens element and a negative lens element in order from the object side;the fourth lens unit comprises a positive lens element;the total number of the lens elements of the first to fourth lens units is eight; andduring magnification change from a wide-angle end to a telephoto end, an interval between the first lens unit and the second lens unit, an interval between the second lens unit and the third lens unit and an interval between the third lens unit and the fourth lens unit change, andthe first lens unit moves.

2. The zoom lens system according to claim 1, further comprising: an aperture stop which is disposed between the second lens unit and the third lens unit and which moves in an optical axis direction during the magnification change,wherein during the magnification change from the wide-angle end to the telephoto end, the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move in the optical axis direction; andin the telephoto end than in the wide-angle end, the interval between the first lens unit and the second lens unit increases,the interval between the second lens unit and the third lens unit decreases,the third lens unit is positioned closer to the object side, andthe aperture stop is positioned closer to the object side.

3. A zoom lens system comprising, in order from an object side: a first lens unit having a positive refractive power;a second lens unit having a negative refractive power;a third lens unit having a positive refractive power; anda fourth lens unit having a positive refractive power,wherein the first lens unit comprises a negative lens element and a positive lens element in order from the object side;the second lens unit comprises a negative lens element and a positive lens element in order from the object side;the third lens unit comprises a positive lens element and a negative lens element in order from the object side;the fourth lens unit comprises a positive lens element;the total number of the lens elements of the first to fourth lens units is seven;during magnification change from a wide-angle end to a telephoto end, an interval between the first lens unit and the second lens unit, an interval between the second lens unit and the third lens unit and an interval between the third lens unit and the fourth lens unit change;an aperture stop which moves in an optical axis direction during the magnification change is disposed between the second lens unit and the third lens unit; andin the telephoto end than in the wide-angle end, the interval between the first lens unit and the second lens unit increases,the interval between the second lens unit and the third lens unit decreases,the third lens unit is positioned closer to the object side, andthe aperture stop is positioned closer to the object side.

4. The zoom lens system according to claim 1, wherein the first lens unit is positioned closer to the object side in the telephoto end than in the wide-angle end.

5. An image pickup apparatus comprising: the zoom lens system according to claim 1; andan image pickup element which is disposed on an image side of the zoom lens system and which converts an optical image formed by the zoom lens system into an electric signal.

6. The zoom lens system according to claim 1, wherein the following condition (1) is satisfied: 0.6<fT/fg1<2.5  (1),

7. The zoom lens system according to claim 1, wherein the following condition (2) is satisfied: −10<fT/fg2<−2.5  (2),

8. The zoom lens system according to claim 1, wherein the following condition (3) is satisfied: 2<fT/fg3<7  (3),

9. The zoom lens system according to claim 1, wherein the following condition (4) is satisfied: 1.35<fT/fg4<5  (4),

10. The zoom lens system according to claim 1, wherein the following condition (5) is satisfied: 0.3<fg1/fTg234<2.5  (5),

11. The zoom lens system according to claim 1, wherein the following condition (6) is satisfied: −0.7<fg2/fTg34<−0.2  (6),

12. The zoom lens system according to claim 1, wherein the following condition (7) is satisfied: −0.45<fg3/fTg12<−0.1  (7),

13. The zoom lens system according to claim 3, wherein the following condition (8) is satisfied: −0.55<fg3/fTg12<−0.15  (8),

14. The zoom lens system according to claim 4, wherein the following condition (9) is satisfied: 0.2<|Dg1/D|<1.5  (9),

15. The zoom lens system according to claim 1, wherein the following condition (10) is satisfied: −0.4<Dg2/D<0.4  (10),

16. The zoom lens system according to claim 15, wherein the following condition (11) is satisfied: 0.01<|Dg2|/D  (11).

17. The zoom lens system according to claim 1, wherein during the magnification change from the wide-angle end to the telephoto end, the second lens unit moves toward the object side, then a movement direction reverses, and the unit moves toward an image side and is positioned closer to the image side in the telephoto end than in the wide-angle end; and the following condition is satisfied: 0.01<Dg2/D<0.25  (12),

18. The zoom lens system according to claim 1, wherein the following condition (13) is satisfied: 0.4<|Dg3/D|<1.0  (13),

19. The zoom lens system according to claim 1, wherein the following condition (14) is satisfied: −0.8<(rL2f+rL2r)/(rL2f−rL2r)<0.0  (14),

20. The zoom lens system according to claim 1, wherein the following condition (15) is satisfied: 0.1<(rL3f+rL3r)/(rL3f−rL3r)<0.75  (15),

21. The zoom lens system according to claim 1, wherein the positive lens element of the second lens unit is a positive meniscus lens whose convex surface faces the object side.

22. The zoom lens system according to claim 1, wherein the following condition (16) is satisfied: −10<(rL4f+rL4r)/(rL4f−rL4r)<−2  (16),

23. The zoom lens system according to claim 1, wherein the negative lens element of the third lens unit is a double concave lens.

24. The zoom lens system according to claim 23, wherein the following condition (17) is satisfied: −0.8<(rL7f+rL7r)/(rL7f−rL7r)<0.8.  (17),

25. The zoom lens system according to claim 2, wherein the aperture stop moves integrally with the third lens unit.

26. The zoom lens system according to claim 1, wherein an object-side surface and an image-side surface of the negative lens element of the second lens unit are concave surfaces, and aspherical surfaces which have a negative power and the refractive power of portions on the surfaces weaken with distance from an optical axis.

27. The zoom lens system according to claim 1, wherein the positive lens element of the first lens unit is a double convex lens; the negative lens element of the second lens unit is a double concave lens; andan image-side surface of the positive lens element of the first lens unit satisfies the following condition (18): 0.15<|rL2r/fg1|<2.00  (18),

28. The zoom lens system according to claim 27, wherein the image-side surface of the positive lens element of the first lens unit is an aspherical surface which has a positive power and the refractive power of a portion on the surface weakens with distance from an optical axis.

29. The zoom lens system according to claim 1, wherein the following condition (19) is satisfied: 3.0<fT/fW  (19),

30. A zoom lens system comprising, in order from an object side: a first lens unit having a positive refractive power;a second lens unit having a negative refractive power;a third lens unit having a positive refractive power; anda fourth lens unit having a positive refractive power,wherein during magnification change from a wide-angle end to a telephoto end, an interval between the first lens unit and the second lens unit, an interval between the second lens unit and the third lens unit and an interval between the third lens unit and the fourth lens unit change;the second lens unit moves; and a movement direction reverses from a moving state toward the object side to a moving state toward an image side between the wide-angle end and an intermediate focal length state with the proviso that the intermediate focal length state is a state in which a focal length of the zoom lens system is a geometrical average value of the focal lengths in the wide-angle end and the telephoto end.

31. The zoom lens system according to claim 30, wherein during the magnification change from the wide-angle end to the telephoto end, the interval between the first lens unit and the second lens unit increases, andthe interval between the second lens unit and the third lens unit decreases; andthe first lens unit, the second lens unit and the third lens unit are all positioned closer to the object side in the telephoto end than in the wide-angle end.

32. The zoom lens system according to claim 31, wherein during the magnification change from the wide-angle end to the telephoto end, a movement direction of the fourth lens unit reverses from the moving state toward the image side to the moving state toward the object side, and then the movement direction further reverses from the moving state toward the object side to the moving state toward the image side.

33. The zoom lens system according to claim 32, wherein the first lens unit comprises a negative lens element and a positive lens element in order from the object side; the second lens unit comprises a negative lens element and a positive lens element in order from the object side;the third lens unit comprises a positive lens element, a positive lens element and a negative lens element in order from the object side;the fourth lens unit comprises a positive lens element; andthe total number of the lens elements of the first to fourth lens units is eight.

34. A zoom lens system comprising, in order from an object side: a first lens unit having a positive refractive power;a second lens unit having a negative refractive power;a third lens unit having a positive refractive power; anda fourth lens unit having a positive refractive power,wherein during magnification change from a wide-angle end to a telephoto end, an interval between the first lens unit and the second lens unit, an interval between the second lens unit and the third lens unit and an interval between the third lens unit and the fourth lens unit change,the fourth lens unit moves, a movement direction reverses from a moving state toward an image side to a moving state toward the object side, and then the movement direction further reverses from the moving state toward the object side to the moving state toward the image side.

35. The zoom lens system according to claim 34, wherein the movement direction of the fourth lens unit reverses from the moving state toward the image side to the moving state toward the object side between the wide-angle end and an intermediate focal length state; and the movement direction reverses from the moving state toward the object side to the moving state toward the image side between the intermediate focal length state and the telephoto end with the proviso that the intermediate focal length state is a state in which a focal length of the zoom lens system is a geometrical average value of the focal lengths in the wide-angle end and the telephoto end.

36. A zoom lens system comprising, in order from an object side: a first lens unit having a positive refractive power;a second lens unit having a negative refractive power;a third lens unit having appositive refractive power; anda fourth lens unit having a positive refractive power,wherein the first lens unit comprises at most two lens elements;the second lens unit comprises a negative lens element and a positive lens element in order from the object side, the total number of the lens elements of the second lens unit is two;the third lens unit comprises at most three lens elements;the fourth lens unit comprises one lens element, the total number of the lens elements of the fourth lens unit is one;during magnification change from a wide-angle end to a telephoto end, an interval between the first lens unit and the second lens unit, an interval between the second lens unit and the third lens unit and an interval between the third lens unit and the fourth lens unit change,the first lens unit moves,the interval between the first lens unit and the second lens unit increases, andthe interval between the second lens unit and the third lens unit decreases; andthe following condition (19) is satisfied: 3.0<fT/fW  (19),

37. The zoom lens system according to claim 34, wherein the following condition (19-1) is satisfied, 4.0<fT/fW  (19-1),

38. The zoom lens system according to claim 34, wherein the following condition (19-2) is satisfied, 4.5<fT/fW  (19-2),

39. The zoom lens system according to claim 34, wherein the total number of the lens elements of the first lens unit is two; and the third lens unit comprises a positive lens element and a negative lens element.