Zoom lens system

Abstract

A zoom lens system which includes, in order from an object side, a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power, a space between the lens units is changed to perform magnification change; a lens of the second lens unit closest to an image side has a concave surface which faces the image side; a lens of the third lens unit closest to the object side is a negative lens whose concave surface faces the object side; and during the magnification change, the space between the second lens unit and the third lens unit is larger in a telephoto end than in a wide-angle end.

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 1C are sectional views of Example 1 of a zoom lens system according to the present invention when focused on an infinite object, FIG. 1A is a sectional view in a wide-angle end, FIG. 1B is a sectional view in an intermediate state, and FIG. 1C is a sectional view in a telephoto end;

FIGS. 2A to 2C are sectional views of Example 2 of a zoom lens system according to the present invention when focused on an infinite object, FIG. 2A is a sectional view in a wide-angle end, FIG. 2B is a sectional view in an intermediate state, and FIG. 2C is a sectional view in a telephoto end;

FIGS. 3A to 3C are sectional views of Example 3 of a zoom lens system according to the present invention when focused on an infinite object, FIG. 3A is a sectional view in a wide-angle end, FIG. 3B is a sectional view in an intermediate state, and FIG. 3C is a sectional view in a telephoto end;

FIGS. 4A to 4C are sectional views of Example 4 of a zoom lens system according to the present invention when focused on an infinite object, FIG. 4A is a sectional view in a wide-angle end, FIG. 4B is a sectional view in an intermediate state, and FIG. 4C is a sectional view in a telephoto end;

FIGS. 5A to 5C are sectional views of Example 5 of a zoom lens system according to the present invention when focused on an infinite object, FIG. 5A is a sectional view in a wide-angle end, FIG. 5B is a sectional view in an intermediate state, and FIG. 5C is a sectional view in a telephoto end;

FIGS. 6A to 6C are sectional views of Example 6 of a zoom lens system according to the present invention when focused on an infinite object, FIG. 6A is a sectional view in a wide-angle end, FIG. 6B is a sectional view in an intermediate state, and FIG. 6C is a sectional view in a telephoto end;

FIGS. 7A to 7C are sectional views of Example 7 of a zoom lens system according to the present invention when focused on an infinite object, FIG. 7A is a sectional view in a wide-angle end, FIG. 7B is a sectional view in an intermediate state, and FIG. 7C is a sectional view in a telephoto end;

FIGS. 8A to 8C are diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration of magnification (CC) of Example 1 when focused on the infinite object, FIG. 8A is an aberration diagram in the wide-angle end, FIG. 8B is an aberration diagram in the intermediate state, and FIG. 8C is an aberration diagram in the telephoto end;

FIGS. 9A to 9C are diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration of magnification (CC) of Example 2 when focused on the infinite object, FIG. 9A is an aberration diagram in the wide-angle end, FIG. 9B is an aberration diagram in the intermediate state, and FIG. 9C is an aberration diagram in the telephoto end;

FIGS. 10A to 10C are diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration of magnification (CC) of Example 3 when focused on the infinite object, FIG. 10A is an aberration diagram in the wide-angle end, FIG. 10B is an aberration diagram in the intermediate state, and FIG. 10C is an aberration diagram in the telephoto end;

FIGS. 11A to 11C are diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration of magnification (CC) of Example 4 when focused on the infinite object, FIG. 11A is an aberration diagram in the wide-angle end, FIG. 11B is an aberration diagram in the intermediate state, and FIG. 11C is an aberration diagram in the telephoto end;

FIGS. 12A to 12C are diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration of magnification (CC) of Example 5 when focused on the infinite object, FIG. 12A is an aberration diagram in the wide-angle end, FIG. 12B is an aberration diagram in the intermediate state, and FIG. 12C is an aberration diagram in the telephoto end;

FIGS. 13A to 13C are diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration of magnification (CC) of Example 6 when focused on the infinite object, FIG. 13A is an aberration diagram in the wide-angle end, FIG. 13B is an aberration diagram in the intermediate state, and FIG. 13C is an aberration diagram in the telephoto end;

FIGS. 14A to 14C are diagrams showing a spherical aberration (SA), an astigmatism (FC), a distortion (DT) and a chromatic aberration of magnification (CC) of Example 7 when focused on the infinite object, FIG. 14A is an aberration diagram in the wide-angle end, FIG. 14B is an aberration diagram in the intermediate state, and FIG. 14C is an aberration diagram in the telephoto end;

FIG. 15 is a front perspective view showing an appearance of a digital camera using the zoom lens system of the present invention;

FIG. 16 is a rear view of the digital camera of FIG. 15;

FIG. 17 is an explanatory view showing an inner constitution of the digital camera of FIG. 15;

FIG. 18 is a schematic block diagram showing a main part of a control system of the digital camera shown in FIG. 15;

FIG. 19 is a front view of a cellular phone;

FIG. 20 is a sectional view of a photographing optical system incorporated in the cellular phone;

FIG. 21 is a side view of the cellular phone; and

FIG. 22 is a schematic block diagram showing a main part of a control system related to photographing, image recording and image display of the cellular phone of FIG. 19.

Claims

1. A zoom lens system comprising, in order from an object side: a first lens unit having a negative refractive power;a second lens unit having a positive refractive power; anda third lens unit having a positive refractive power,wherein a space between the lens units is changed to perform magnification change;a lens of the second lens unit closest to an image side has a concave surface which faces the image side;a lens of the third lens unit closest to the object side is a negative lens whose concave surface faces the object side; andduring the magnification change, the space between the second lens unit and the third lens unit is larger in a telephoto end than in a wide-angle end.

2. The zoom lens system according to claim 1, wherein the third lens unit is moved to perform focusing on an object at a short distance.

3. The zoom lens system according to claim 1, wherein the third lens unit includes a negative lens and a positive lens in order from the object side.

4. The zoom lens system according to claim 3, wherein the negative lens and the positive lens of the third lens unit satisfy the following condition: −4.2<f3n/f3p<−1.1  (1),in which f3n is a focal length of the negative lens of the third lens unit, and f3p is a focal length of the positive lens of the third lens unit.

5. The zoom lens system according to claim 1, wherein the negative lens of the third lens unit closest to the object side satisfies the following condition: −7.90<SF3n<−1.20  (2),in which SF3n is defined by SF3n=(R31f+R31r)/(R31f−R31r) and in which R31f, R31r are paraxial radii of curvatures of an object-side surface and an image-side surface of the negative lens of the third lens unit, respectively.

6. The zoom lens system according to claim 1, wherein the negative lens of the third lens unit closest to the object side satisfies the following conditions: 1.75<nd3n<2.20  (3); and13.0<vd3n<33.0  (4),in which nd3n and vd3n are a refractive index and the Abbe number of the negative lens of the third lens unit closest to the object side for the d-line, respectively.

7. The zoom lens system according to claim 1, wherein the following condition is satisfied: 0.35<d23/fw<1.25  (5),in which d23 is an axial space between the second lens unit and the third lens unit in the wide-angle end, and fw is a focal length of the zoom lens system in the wide-angle end.

8. The zoom lens system according to claim 1, wherein the first lens unit includes two lenses or less.

9. The zoom lens system according to claim 8, wherein the first lens unit includes one negative lens.

10. The zoom lens system according to claim 9, wherein the negative lens of the first lens unit satisfies the following condition: 75.0<vd1n<105.0  (6),in which Vd1n, is the Abbe number of the negative lens of the first lens unit.

11. The zoom lens system according to claim 10, wherein the negative lens of the first lens unit satisfies the following condition: 0.01<SF1n<1.00  (7),in which SF1n is defined by SF1n=(R11f+R11r)/(R11f−R11r) and in which R11f, R11r are paraxial radii of curvatures of an object-side surface and an image-side surface of the negative lens of the first lens unit, respectively.

12. The zoom lens system according to claim 8, wherein the first lens unit includes a cemented lens of a negative lens and a positive lens.

13. The zoom lens system according to claim 1, wherein an aperture stop is disposed between the second lens unit and the third lens unit.

14. The zoom lens system according to claim 1, wherein the following condition is satisfied: 5.0<Fnow×Lw/fw<17.0  (16),in which Fnow is a full aperture F-value in the wide-angle end, Lw is the total length of the zoom lens system in the wide-angle end, and fw is a focal length of the zoom lens system in the wide-angle end.

15. An electronic image pickup unit comprising: the zoom lens system according to claim 1; andan image sensor disposed at a position where an object image formed by the zoom lens system is received.

16. An information processing device comprising: the zoom lens system according to claim 1;an image sensor disposed at a position where an object image formed by the zoom lens system is received;a CPU which processes an electric signal photoelectrically converted by the image sensor;an input section which inputs an information signal to be input into the CPU by an operator;display processing section for displaying an output from the CPU in a display unit; anda recording medium which records the output from the CPU,wherein the CPU is configured to perform control so as to display the object image received by the image sensor in the display unit.

17. The information processing device according to claim 16, which is a portable terminal device.

18. An electronic camera device comprising: the zoom lens system according to claim 1;an image sensor disposed at a position where an object image formed by the zoom lens system is received;a CPU which processes an electric signal photoelectrically converted by the image sensor;a display element which displays the object image received by the image sensor so as to observe the image; anda recording processing section which records the object image received by the image sensor in a recording medium; andthe recording medium incorporated in the electronic camera device and/or constituted so as to be detachably attached to the electronic camera device in order to record image information of the object image received by the image sensor,wherein the CPU is configured to perform control so as to display the object image received by the image sensor in the display element and to record the object image received by the image sensor in the recording medium.