JP2010160333A - Zoom lens system, imaging apparatus, and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens system with high performance by having both of a wide field angle at an wide angle end and a high zooming ratio while being compact, and to provide an imaging apparatus and a camera. <P>SOLUTION: The zoom lens system includes a first positive power lens group, a second negative power lens group, a third positive power lens group, and a fourth positive power lens group in order from an object side to an image side. The first lens group and the second lens group include three lens elements respectively. In zooming from the wide angle end to a telescopic end, the first to the fourth lens groups are moved along an optical axis respectively to perform variable magnification so that an air space between respective lens groups is changed, and the zoom lens system, the imaging apparatus and the camera satisfy conditions: -3.12≤T<SB>G1</SB>/f<SB>W</SB>≤-2.36, 1.26≤T<SB>G2</SB>/f<SB>W</SB>≤1.78, ω<SB>W</SB>≥37 and f<SB>T</SB>/f<SB>W</SB>≥10. Herein, T<SB>G1</SB>, T<SB>G2</SB>: movement amount on optical axis of the first and second lens groups from object side to image side in zooming from wide angle end to telescopic end in imaging, ω<SB>W</SB>: half field angle at wide angle end, f<SB>T</SB>, f<SB>W</SB>: focal lengths of entire system at telescopic end and wide angle end, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a zoom lens system, an imaging apparatus, and a camera. In particular, the present invention is a compact high-performance zoom lens system having a wide angle of view at a wide-angle end and a high zooming ratio, an imaging device including the zoom lens system, and a thin type including the imaging device. It relates to a compact camera.

  There is an extremely strong demand for compactness and high performance of a camera having an image sensor that performs photoelectric conversion (hereinafter simply referred to as a digital camera) such as a digital still camera or a digital video camera. In particular, a camera equipped with a zoom lens system with a high zooming ratio that can cover a wide focal length range from a wide angle range to a high telephoto range with a single digital camera is strongly demanded for its convenience. . On the other hand, in recent years, a zoom lens system having a wide angle range with a wide photographing range is also demanded.

  As described above, as a zoom lens system having a high zooming ratio, conventionally, in order from the object side to the image side, a first lens group having a positive power, a second lens group having a negative power, and a positive power are provided. Various zoom lenses having a positive, negative and positive four-group configuration in which a third lens group having a positive power and a fourth lens group having a positive power are arranged have been proposed.

  Patent Document 1 has the above-described four-group configuration of positive, negative, positive and positive, and when zooming from the wide-angle end to the telephoto end, the first lens group and the third lens group are relatively at the telephoto end position rather than at the wide-angle end position. The second lens group is displaced more toward the image side than the wide-angle end position, and the fourth lens group moves along the optical axis. A zoom lens is disclosed in which the focal length ratio of one lens group and the imaging magnification of the second lens group are defined.

  Patent Document 2 has the above-described four-group configuration of positive, negative, positive and positive, and at the time of zooming from the wide-angle end to the telephoto end, the first lens group moves monotonously to the object side, and the second lens group monotonously moves to the image side. And the third lens unit moves so that the third lens unit is positioned closer to the object side at the wide-angle end than the telephoto end, and the fourth lens unit and the third lens unit at the telephoto end rather than the wide-angle end when focusing on an object point at infinity. Of the third and fourth lens groups, the air distance of the third and fourth lens groups, and the synthesis of the first to third lens groups. A zoom lens that defines a focal length is disclosed.

  Patent Document 3 has the above-described four-group configuration of positive, negative, positive and positive, changes the distance between each group upon zooming from the wide-angle end to the telephoto end, and the first lens group is at the telephoto end rather than the wide-angle end. The zoom lens is disclosed in which the focal length of the first lens group and the lateral magnification at the telephoto end and the wide-angle end of the second lens group are defined.

  Patent Document 4 has a positive, negative, positive, and positive four-group configuration, and at least the first and third lens groups move during zooming. A zoom lens is disclosed in which the relative movement amount of the second lens unit and the focal lengths of the first and third lens units in zooming from the wide-angle end to the telephoto end are defined.

  Patent Document 5 has a four-group configuration of positive, negative, positive and positive, and at least the first lens group moves during zooming from the wide-angle end to the telephoto end, the focal length of the first lens group, The zoom lens which prescribe | regulated the average refractive index with respect to d line of all the lenses of this is disclosed.

Patent Document 6 has a positive, negative, positive, and positive four-group configuration, and when zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases, and the second lens group and the second lens group A zoom lens is disclosed in which the distance from the three lens groups is reduced, and the refractive index, Abbe number, and anomalous dispersion are defined for at least one positive lens in the third lens group.
JP 07-005361 A JP-A-07-020281 JP 2006-133632 A JP 2007-003554 A JP 2007-010695 A JP 2008-026837 A

  However, each of the zoom lenses disclosed in Patent Documents 1 to 6 is downsized to such a degree that it can be applied to a thin and compact digital camera, and has a high zooming ratio of about 10 times or more. Since the angle of view at the edge is insufficient, recent demands cannot be satisfied.

  An object of the present invention is a high-performance zoom lens system that has a wide angle of view at a wide-angle end and a high zooming ratio while being small, an imaging device including the zoom lens system, and a thin type including the imaging device Is to provide a compact camera.

One of the above objects is achieved by the following zoom lens system. That is, the present invention
In order from the object side to the image side, a first lens group having a positive power, a second lens group having a negative power, a third lens group having a positive power, and a fourth lens having a positive power A group of
The first lens group is composed of three lens elements,
The second lens group is composed of three lens elements,
During zooming from the wide-angle end to the telephoto end during imaging, the first lens group, the second lens group, the third lens group, and the fourth lens group have an air space between each lens group and the lens group. Move each along the optical axis so that it changes,
The following conditions (7), (8), (a-2) and (b):
−3.12 ≦ T _G1 / f _W ≦ −2.36 (7)
1.26 ≦ T _G2 / f _W ≦ 1.78 (8)
ω _W ≧ 37 (a-2)
f _T / f _W ≧ 10 (b)
(here,
T _G1: moving amount of the optical axis from a wide-angle end at the time of imaging during zooming to the telephoto end, from the object side to the image side of the first lens group,
T _G2 : the amount of movement on the optical axis from the object side to the image side of the second lens group during zooming from the wide-angle end to the telephoto end during imaging,
ω _W : Half angle of view (°) at the wide-angle end,
f _T : focal length of the entire system at the telephoto end,
f _W is the focal length of the entire system at the wide-angle end)
The present invention relates to a zoom lens system that satisfies

One of the above objects is achieved by the following imaging device. That is, the present invention
An imaging apparatus capable of outputting an optical image of an object as an electrical image signal,
A zoom lens system that forms an optical image of the object;
An image sensor that converts an optical image formed by the zoom lens system into an electrical image signal;
The zoom lens system is
In order from the object side to the image side, a first lens group having a positive power, a second lens group having a negative power, a third lens group having a positive power, and a fourth lens having a positive power A group of
The first lens group is composed of three lens elements,
The second lens group is composed of three lens elements,
During zooming from the wide-angle end to the telephoto end during imaging, the first lens group, the second lens group, the third lens group, and the fourth lens group have an air space between each lens group and the lens group. Move each along the optical axis so that it changes,
The following conditions (7), (8), (a-2) and (b):
−3.12 ≦ T _G1 / f _W ≦ −2.36 (7)
1.26 ≦ T _G2 / f _W ≦ 1.78 (8)
ω _W ≧ 37 (a-2)
f _T / f _W ≧ 10 (b)
(here,
T _G1: moving amount of the optical axis from a wide-angle end at the time of imaging during zooming to the telephoto end, from the object side to the image side of the first lens group,
T _G2 : the amount of movement on the optical axis from the object side to the image side of the second lens group during zooming from the wide-angle end to the telephoto end during imaging,
ω _W : Half angle of view (°) at the wide-angle end,
f _T : focal length of the entire system at the telephoto end,
f _W is the focal length of the entire system at the wide-angle end)
The present invention relates to an imaging apparatus that is a zoom lens system that satisfies

One of the above objects is achieved by the following camera. That is, the present invention
A camera that converts an optical image of an object into an electrical image signal, and displays and stores the converted image signal;
An image pickup apparatus including a zoom lens system that forms an optical image of an object, and an image sensor that converts an optical image formed by the zoom lens system into an electrical image signal;
The zoom lens system is
In order from the object side to the image side, a first lens group having a positive power, a second lens group having a negative power, a third lens group having a positive power, and a fourth lens having a positive power A group of
The first lens group is composed of three lens elements,
The second lens group is composed of three lens elements,
During zooming from the wide-angle end to the telephoto end during imaging, the first lens group, the second lens group, the third lens group, and the fourth lens group have an air space between each lens group and the lens group. Move each along the optical axis so that it changes,
The following conditions (7), (8), (a-2) and (b):
−3.12 ≦ T _G1 / f _W ≦ −2.36 (7)
1.26 ≦ T _G2 / f _W ≦ 1.78 (8)
ω _W ≧ 37 (a-2)
f _T / f _W ≧ 10 (b)
(here,
T _G1 : the amount of movement on the optical axis from the object side to the image side of the first lens group during zooming from the wide-angle end to the telephoto end during imaging,
T _G2 : the amount of movement on the optical axis from the object side to the image side of the second lens group during zooming from the wide-angle end to the telephoto end during imaging,
ω _W : Half angle of view (°) at the wide-angle end,
f _T : focal length of the entire system at the telephoto end,
f _W is the focal length of the entire system at the wide-angle end)
The present invention relates to a camera that is a zoom lens system satisfying the above.

  According to the present invention, a high-performance zoom lens system having a wide angle of view at a wide-angle end and a high zooming ratio, an image pickup apparatus including the zoom lens system, and a thin type including the image pickup apparatus are small in size. A compact camera can be provided.

(Embodiments 1 to 6)
1, 4, 7, 9, 11 and 14 are lens arrangement diagrams of the zoom lens systems according to Embodiments 1 to 6, respectively.

1, 4, 7, 9, 11, and 14 represent the zoom lens system in an infinitely focused state. In each figure, (a) shows the lens configuration at the wide angle end (shortest focal length state: focal length f _W ), and (b) shows the intermediate position (intermediate focal length state: focal length f _M = √ (f _W * f). _T )) shows a lens configuration, and FIG. 8C shows a lens configuration at the telephoto end (longest focal length state: focal length f _T ). In each figure, straight or curved arrows provided between FIGS. (A) and (b) indicate the movement of each lens group from the wide-angle end to the telephoto end via the intermediate position. Furthermore, in each figure, the arrow attached to the lens group represents the focusing from the infinite focus state to the close object focus state. That is, the moving direction during focusing from the infinitely focused state to the close object focused state is shown.

  The zoom lens system according to each embodiment includes, in order from the object side to the image side, a first lens group G1 having a positive power, a second lens group G2 having a negative power, and a first lens group having a positive power. A third lens group G3 and a fourth lens group G4 having a positive power. During zooming, the distance between the lens groups, that is, the distance between the first lens group G1 and the second lens group G2, the second lens Each lens group moves in a direction along the optical axis so that the distance between the group G2 and the third lens group G3 and the distance between the third lens group G3 and the fourth lens group G4 change. The zoom lens system according to each embodiment can reduce the size of the entire lens system while maintaining high optical performance by arranging these lens groups in a desired power arrangement.

  In FIGS. 1, 4, 7, 9, 11, and 14, an asterisk * attached to a specific surface indicates that the surface is aspherical. In each figure, a symbol (+) and a symbol (−) attached to a symbol of each lens group correspond to a power symbol of each lens group. In each figure, the straight line described on the rightmost side represents the position of the image plane S, and is located on the object side of the image plane S (between the image plane S and the most image side lens surface of the fourth lens group G4). Is provided with a parallel plate P equivalent to an optical low-pass filter, a face plate of an image sensor, or the like.

  Further, in FIGS. 1, 4, 7, 9, 11 and 14, an aperture stop A is provided on the most object side of the third lens group G3, and the aperture stop A extends from the wide-angle end to the telephoto end during imaging. During zooming, it moves on the optical axis integrally with the third lens group G3.

  As shown in FIG. 1, in the zoom lens system according to Embodiment 1, the first lens group G1 is a negative meniscus first lens element L1 having a convex surface directed toward the object side in order from the object side to the image side. And a positive meniscus second lens element L2 having a convex surface facing the object side, and a positive meniscus third lens element L3 having a convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented, and in the surface data in the corresponding numerical example described later, the adhesion between the first lens element L1 and the second lens element L2 Surface number 2 is given to the agent layer.

  In the zoom lens system according to Embodiment 1, the second lens group G2 includes, in order from the object side to the image side, a negative meniscus fourth lens element L4 having a convex surface directed toward the object side, and a biconcave second lens element L4. 5 lens elements L5 and a positive meniscus sixth lens element L6 having a convex surface facing the object side.

  In the zoom lens system according to Embodiment 1, the third lens unit G3 includes, in order from the object side to the image side, a positive meniscus seventh lens element L7 with a convex surface facing the object side, and a convex surface facing the object side And a negative meniscus ninth lens element L9 having a convex surface facing the object side. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented, and in the surface data in the corresponding numerical value example described later, the adhesion between the eighth lens element L8 and the ninth lens element L9. Surface number 17 is given to the agent layer. The eighth lens element L8 has an aspheric object side surface.

  In the zoom lens system according to Embodiment 1, the fourth lens unit G4 comprises solely a bi-convex tenth lens element L10. The tenth lens element L10 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 1, a parallel plate P is provided on the object side of the image plane S (between the image plane S and the tenth lens element L10).

  In the zoom lens system according to Embodiment 1, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 and the third lens group G3 move to the object side, and the second lens group G2 Moves toward the image side, and the fourth lens group G4 moves toward the image side along a locus convex toward the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens group G3 and the fourth lens. Each lens group moves along the optical axis so that the distance from the group G4 increases.

  As shown in FIG. 4, in the zoom lens system according to Embodiment 2, the first lens unit G1 includes a negative meniscus first lens element L1 having a convex surface directed toward the object side in order from the object side to the image side. And a positive meniscus second lens element L2 having a convex surface facing the object side, and a positive meniscus third lens element L3 having a convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented, and in the surface data in the corresponding numerical example described later, the adhesion between the first lens element L1 and the second lens element L2 Surface number 2 is given to the agent layer.

  In the zoom lens system according to Embodiment 2, the second lens group G2 includes, in order from the object side to the image side, a negative meniscus fourth lens element L4 having a convex surface directed toward the object side, and a biconcave second lens element L4. 5 lens elements L5 and a positive meniscus sixth lens element L6 having a convex surface facing the object side.

  In the zoom lens system according to Embodiment 2, the third lens unit G3 includes, in order from the object side to the image side, a positive meniscus seventh lens element L7 with a convex surface facing the object side, and a convex surface facing the object side And a negative meniscus ninth lens element L9 having a convex surface facing the object side. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented, and in the surface data in the corresponding numerical value example described later, the adhesion between the eighth lens element L8 and the ninth lens element L9. Surface number 17 is given to the agent layer. The eighth lens element L8 has an aspheric object side surface.

  In the zoom lens system according to Embodiment 2, the fourth lens unit G4 comprises solely a bi-convex tenth lens element L10. The tenth lens element L10 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 2, a parallel plate P is provided on the object side of the image plane S (between the image plane S and the tenth lens element L10).

  In the zoom lens system according to Embodiment 2, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 and the third lens group G3 move to the object side, and the second lens group G2 Moves toward the image side, and the fourth lens group G4 moves toward the image side along a locus convex toward the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens group G3 and the fourth lens. Each lens group moves along the optical axis so that the distance from the group G4 increases.

  As shown in FIG. 7, in the zoom lens system according to Embodiment 3, the first lens group G1 is a negative meniscus first lens element L1 having a convex surface directed toward the object side in order from the object side to the image side. And a positive meniscus second lens element L2 having a convex surface facing the object side, and a positive meniscus third lens element L3 having a convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented, and in the surface data in the corresponding numerical example described later, the adhesion between the first lens element L1 and the second lens element L2 Surface number 2 is given to the agent layer.

  In the zoom lens system according to Embodiment 3, the second lens unit G2 includes, in order from the object side to the image side, a negative meniscus fourth lens element L4 having a convex surface directed toward the object side, and a biconcave second lens element L4. 5 lens elements L5 and a positive meniscus sixth lens element L6 having a convex surface facing the object side.

  In the zoom lens system according to Embodiment 3, the third lens unit G3 includes, in order from the object side to the image side, a biconvex seventh lens element L7 and a negative meniscus shape having a convex surface directed toward the object side. It comprises an eighth lens element L8 and a positive meniscus ninth lens element L9 with the convex surface facing the object side. Among these, the seventh lens element L7 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 3, the fourth lens unit G4 comprises solely a bi-convex tenth lens element L10. The tenth lens element L10 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 3, a parallel plate P is provided on the object side of the image plane S (between the image plane S and the tenth lens element L10).

  In the zoom lens system according to Embodiment 3, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 and the third lens group G3 move to the object side, and the second lens group G2 Moves toward the image side, and the fourth lens group G4 moves toward the image side along a locus convex toward the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens group G3 and the fourth lens. Each lens group moves along the optical axis so that the distance from the group G4 increases.

  As shown in FIG. 9, in the zoom lens system according to Embodiment 4, the first lens unit G1 includes, in order from the object side to the image side, a negative meniscus first lens element L1 having a convex surface directed toward the object side. And a positive meniscus second lens element L2 having a convex surface facing the object side, and a positive meniscus third lens element L3 having a convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented, and in the surface data in the corresponding numerical example described later, the adhesion between the first lens element L1 and the second lens element L2 Surface number 2 is given to the agent layer.

  In the zoom lens system according to Embodiment 4, the second lens group G2 includes, in order from the object side to the image side, a negative meniscus fourth lens element L4 with a convex surface directed toward the object side, and a biconcave second lens element L4. 5 lens elements L5 and a positive meniscus sixth lens element L6 having a convex surface facing the object side.

  In the zoom lens system according to Embodiment 4, the third lens unit G3 includes, in order from the object side to the image side, a biconvex seventh lens element L7 and a negative meniscus shape having a convex surface directed toward the object side. And an eighth lens element L8. Among these, the seventh lens element L7 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 4, the fourth lens unit G4 comprises solely a bi-convex ninth lens element L9. The ninth lens element L9 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 4, a parallel plate P is provided on the object side of the image plane S (between the image plane S and the ninth lens element L9).

  In the zoom lens system according to Embodiment 4, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 and the third lens group G3 move to the object side, and the second lens group G2 Moves toward the image side, and the fourth lens group G4 moves toward the image side along a locus convex toward the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens group G3 and the fourth lens. Each lens group moves along the optical axis so that the distance from the group G4 increases.

  As shown in FIG. 11, in the zoom lens system according to Embodiment 5, the first lens unit G1 includes, in order from the object side to the image side, a negative meniscus first lens element L1 having a convex surface directed toward the object side. And a positive meniscus second lens element L2 having a convex surface facing the object side, and a positive meniscus third lens element L3 having a convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented, and in the surface data in the corresponding numerical example described later, the adhesion between the first lens element L1 and the second lens element L2 Surface number 2 is given to the agent layer.

  In the zoom lens system according to Embodiment 5, the second lens unit G2 includes, in order from the object side to the image side, a negative meniscus fourth lens element L4 with a convex surface directed toward the object side, and a biconcave second lens element L4. 5 lens elements L5 and a positive meniscus sixth lens element L6 having a convex surface facing the object side.

  In the zoom lens system according to Embodiment 5, the third lens unit G3 includes, in order from the object side to the image side, a biconvex seventh lens element L7 and a negative meniscus shape having a convex surface directed toward the image side. An eighth lens element L8 and a negative meniscus ninth lens element L9 having a convex surface facing the object side. Among these, the seventh lens element L7 and the eighth lens element L8 are cemented, and in the surface data in the corresponding numerical example described later, the adhesion between the seventh lens element L7 and the eighth lens element L8. Surface number 15 is given to the agent layer. Further, both the seventh lens element L7 and the ninth lens element L9 have an aspheric object side surface.

  In the zoom lens system according to Embodiment 5, the fourth lens unit G4 comprises solely a bi-convex tenth lens element L10. The tenth lens element L10 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 5, a parallel plate P is provided on the object side of the image plane S (between the image plane S and the tenth lens element L10).

  In the zoom lens system according to Embodiment 5, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 and the third lens group G3 move to the object side, and the second lens group G2 Moves toward the image side, and the fourth lens group G4 moves toward the image side along a locus convex toward the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens group G3 and the fourth lens. Each lens group moves along the optical axis so that the distance from the group G4 increases.

  As shown in FIG. 14, in the zoom lens system according to Embodiment 6, the first lens unit G1 includes a negative meniscus first lens element L1 having a convex surface directed toward the object side in order from the object side to the image side. And a positive meniscus second lens element L2 having a convex surface facing the object side, and a positive meniscus third lens element L3 having a convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented, and in the surface data in the corresponding numerical example described later, the adhesion between the first lens element L1 and the second lens element L2 Surface number 2 is given to the agent layer.

  In the zoom lens system according to Embodiment 6, the second lens group G2 includes, in order from the object side to the image side, a negative meniscus fourth lens element L4 with a convex surface directed toward the object side, and a biconcave second lens element L4. It comprises a five-lens element L5 and a positive meniscus sixth lens element L6 with a convex surface facing the object side.

  In the zoom lens system according to Embodiment 6, the third lens unit G3 includes, in order from the object side to the image side, a positive meniscus seventh lens element L7 with a convex surface facing the object side, and a convex surface facing the object side And a negative meniscus ninth lens element L9 having a convex surface facing the object side. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented, and in the surface data in the corresponding numerical value example described later, the adhesion between the eighth lens element L8 and the ninth lens element L9. Surface number 17 is given to the agent layer. The eighth lens element L8 has an aspheric object side surface.

  In the zoom lens system according to Embodiment 6, the fourth lens unit G4 comprises solely a bi-convex tenth lens element L10. The tenth lens element L10 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 6, a parallel plate P is provided on the object side of the image plane S (between the image plane S and the tenth lens element L10).

  In the zoom lens system according to Embodiment 6, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 and the third lens group G3 move to the object side, and the second lens group G2 Moves toward the image side, and the fourth lens group G4 moves toward the image side along a locus convex toward the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens group G3 and the fourth lens. Each lens group moves along the optical axis so that the distance from the group G4 increases.

  In the zoom lens systems according to Embodiments 1 to 6, since the first lens group G1 includes three lens elements and the second lens group G2 includes three lens elements, the lens system has a short lens overall length. .

  In the zoom lens systems according to Embodiments 1 to 6, the first lens group G1 has the negative meniscus lens element L1 having a convex surface directed toward the object side and the convex surface directed toward the object side in order from the object side to the image side. A positive meniscus lens element L2 and a positive meniscus lens element L3 having a convex surface facing the object side, and of these, the negative meniscus lens element L1 and the positive meniscus lens element L2 are joined to form a cemented lens element. Therefore, it is a compact lens system. In addition, with such a configuration, chromatic aberration can be favorably corrected.

  In the zoom lens systems according to Embodiments 1 to 6, the three lens elements constituting the first lens group G1 and the three lens elements constituting the second lens group G2 are located at the center of the second lens group G2. Since it has a positive radius of curvature except for the object side surface of the arranged fifth lens element L5, it is possible to correct field curvature while maintaining a compact lens system.

  In the zoom lens systems according to Embodiments 1 to 6, since the third lens group G3 includes at least one lens element having a negative surface on the image side and having negative power, the spherical aberration, coma aberration, and chromatic aberration are corrected favorably. be able to.

  In the zoom lens systems according to Embodiments 1, 2, and 6, the third lens group G3 includes, in order from the object side to the image side, the seventh lens element L7 having positive power, and the object side surface is aspheric and positive. The eighth lens element L8 having a negative power and the ninth lens element L9 having a negative power, and the eighth lens element L8 and the ninth lens element L9, which are positive lens elements on the image side, are joined. Since the cemented lens element is formed, spherical aberration, coma aberration, and chromatic aberration can be corrected particularly well.

  In the zoom lens systems according to Embodiments 1 to 6, the fourth lens group G4 further includes one lens element, and the lens element has a positive power. In addition, when focusing from an object at infinity to an object at a short distance, rapid focusing is facilitated by extending the fourth lens group G4 to the object side as shown in each drawing. In addition, since one lens element constituting the fourth lens group G4 has two aspheric surfaces, off-axis field curvature from the wide-angle end to the telephoto end can be corrected well.

  In the zoom lens systems according to Embodiments 1 to 6, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens are used for zooming from the wide-angle end to the telephoto end during imaging. The group G4 is moved along the optical axis to perform zooming, and any one of the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4, Alternatively, by moving some sub-lens groups of each lens group in a direction perpendicular to the optical axis, image point movement due to vibration of the entire system is corrected, that is, image blur due to camera shake, vibration, etc. is optically corrected. Can be corrected.

  When correcting the image point movement due to the vibration of the entire system, for example, the third lens group G3 moves in a direction orthogonal to the optical axis, thereby suppressing the increase in size of the entire zoom lens system, Image blur can be corrected while maintaining excellent imaging characteristics with small decentration coma and decentering astigmatism.

  In addition, when one lens group is composed of a plurality of lens elements, a part of the sub-lens groups of each lens group is any one of the plurality of lens elements or adjacent to each other. A plurality of lens elements.

  The following description is given for conditions preferred to be satisfied by a zoom lens system like the zoom lens systems according to Embodiments 1 to 6. A plurality of preferable conditions are defined for the zoom lens system according to each embodiment, but a zoom lens system configuration that satisfies all of the plurality of conditions is most desirable. However, by satisfying individual conditions, it is possible to obtain a zoom lens system that exhibits the corresponding effects.

For example, like the zoom lens systems according to Embodiments 1 to 6, in order from the object side to the image side, a first lens group having a positive power, a second lens group having a negative power, and a positive power And a fourth lens group having positive power, the first lens group is composed of three lens elements, and the second lens group is composed of three lens elements. The zoom lens system (hereinafter, this lens configuration is referred to as a basic configuration of the embodiment) satisfies the following conditions (7), (8), (a-2), and (b).
−3.12 ≦ T _G1 / f _W ≦ −2.36 (7)
1.26 ≦ T _G2 / f _W ≦ 1.78 (8)
ω _W ≧ 37 (a-2)
f _T / f _W ≧ 10 (b)
here,
T _G1 : the amount of movement on the optical axis from the object side to the image side of the first lens group during zooming from the wide-angle end to the telephoto end during imaging,
T _G2 : the amount of movement on the optical axis from the object side to the image side of the second lens group during zooming from the wide-angle end to the telephoto end during imaging,
ω _W : Half angle of view (°) at the wide-angle end,
f _T : focal length of the entire system at the telephoto end,
f _W : the focal length of the entire system at the wide angle end.

  The condition (7) defines the ratio between the amount of movement of the first lens unit on the optical axis and the focal length of the entire system at the wide angle end. If the lower limit of condition (7) is not reached, the focal length of the first lens group becomes short, and it becomes difficult to correct spherical aberration and field curvature. On the other hand, if the upper limit of condition (7) is exceeded, the amount of movement of the first lens group becomes too large, and it becomes difficult to ensure compactness.

In addition, the above effect can be further achieved by satisfying at least one of the following conditions (7) ′ and (7) ″.
-2.94 ≦ T _G1 / f _W (7) ′
T _G1 / f _W ≦ −2.46 (7) ″

  The condition (8) defines the ratio between the amount of movement of the second lens group on the optical axis and the focal length of the entire system at the wide angle end. If the lower limit of condition (8) is not reached, the focal length of the second lens group becomes short, and it becomes difficult to correct field curvature. On the other hand, if the upper limit of condition (8) is exceeded, the amount of movement of the second lens group becomes too large, and it becomes difficult to ensure compactness.

In addition, the above effect can be further achieved by satisfying at least one of the following conditions (8) ′ and (8) ″.
1.32 ≦ T _G2 / f _W (8) ′
T _G2 / f _W ≦ 1.74 (8) ″

For example, the zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 6 preferably satisfies the following condition (10).
4.00 ≦ m _2T / m _2W ≦ 8.00 (10)
here,
m _2T : lateral magnification of the second lens unit at the telephoto end and infinite focus state,
m _2W : The lateral magnification of the second lens group at the wide-angle end and at infinity in-focus state.

  The condition (10) is a condition that regulates the magnification change of the second lens group and substantially optimizes the zooming burden during zooming of the second lens group. If the range of the condition (10) is not satisfied, the zooming load of the second lens group is not appropriate, and it may be difficult to make the zoom lens system compact while maintaining the optical performance.

Furthermore, the above effect can be further achieved by further satisfying at least one of the following conditions (10) ′ and (10) ″.
4.50 ≦ m _2T / m _2W (10) ′
m _2T / m _2W ≦ 6.00 (10) ''

For example, the zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 6 preferably satisfies the following condition (11).
1.00 ≦ L _T / f _T ≦ 2.00 (11)
here,
L _T : Total lens length at the telephoto end (distance from the most object side surface of the first lens group to the image plane),
f _T is the focal length of the entire system at the telephoto end.

  The condition (11) defines the total lens length of the zoom lens system at the telephoto end. If the lower limit of the condition (11) is not reached, the refractive power of each lens group becomes strong, so that various aberrations of each lens group increase and aberration correction may be difficult. On the other hand, if the upper limit of the condition (11) is exceeded, the refractive power of each lens group becomes weak. Therefore, in order to maintain a high zoom ratio, the amount of movement of each lens group becomes large and it is difficult to ensure compactness. There is a risk of becoming.

In addition, the above effect can be further achieved by satisfying at least one of the following conditions (11) ′ and (11) ″.
1.10 ≦ L _T / f _T (11) ′
L _T / f _T ≦ 1.37 (11) ″

For example, a zoom lens system having a basic configuration like the zoom lens systems according to Embodiments 1 to 6 preferably satisfies the following condition (12).
1.00 ≦ f _T / f _G1 ≦ 2.00 (12)
here,
f _G1 : composite focal length of the first lens group,
f _T is the focal length of the entire system at the telephoto end.

  The condition (12) defines an appropriate focal length of the first lens group. If the lower limit of condition (12) is not reached, the refractive power of the first lens group becomes weak. Therefore, in order to maintain a high zoom ratio, the amount of movement of the second lens group becomes large and it is difficult to ensure compactness. There is a risk of becoming. On the contrary, if the upper limit of the condition (12) is exceeded, the refractive index of the first lens group becomes strong, so the amount of various aberrations increases, and it may be difficult to correct axial chromatic aberration, especially at the telephoto end.

In addition, the above effect can be further achieved by satisfying at least one of the following conditions (12) ′ and (12) ″.
1.40 ≦ f _T / f _G1 (12) ′
f _T / f _G1 ≦ 1.70 (12) ″

For example, the zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 6 preferably satisfies the following condition (13).
1.00 ≦ L _W / f _G1 ≦ 2.00 (13)
here,
L _W : total lens length at the wide-angle end (distance from the most object side surface of the first lens group to the image plane),
f _G1 is the combined focal length of the first lens group.

  The condition (13) defines the ratio between the total lens length of the zoom lens system at the wide angle end and the focal length of the first lens group. If the lower limit of condition (13) is not reached, the refractive power of the first lens group becomes weak, so the refractive power of the second lens group becomes weak and the movement amount of the second lens group becomes large. As a result, the position of the first lens unit at the relatively wide-angle end is disposed on the object side, and in order to maintain a wide angle, the outer diameter of the first lens unit is increased and compactness is ensured. May be difficult. On the contrary, if the upper limit of the condition (13) is exceeded, the refractive index of the first lens group becomes strong, so that it is difficult to correct curvature of field particularly at the wide angle end.

Furthermore, the above effect can be further achieved by further satisfying at least one of the following conditions (13) ′ and (13) ″.
1.30 ≦ L _W / f _G1 (13) ′
L _W / f _G1 ≦ 1.50 (13) ″

For example, the zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 6 preferably satisfies the following condition (14).
1.50 ≦ L _T / f _G1 ≦ 2.00 (14)
here,
L _T : Total lens length at the telephoto end (distance from the most object side surface of the first lens group to the image plane),
f _G1 is the combined focal length of the first lens group.

  The condition (14) defines the ratio between the total lens length of the zoom lens system at the telephoto end and the focal length of the first lens group. If the lower limit of condition (14) is not reached, the refractive power of the first lens group becomes weak. Therefore, in order to maintain a high zoom ratio, the amount of movement of the second lens group becomes large and it is difficult to ensure compactness. There is a risk of becoming. On the contrary, if the upper limit of the condition (14) is exceeded, the refractive index of the first lens group becomes strong, so the amount of various aberrations increases, and it may be difficult to correct axial chromatic aberration, especially at the telephoto end.

In addition, the above effect can be further achieved by satisfying at least one of the following conditions (14) ′ and (14) ″.
1.60 ≦ L _T / f _G1 (14) ′
L _T / f _G1 ≦ 1.80 (14) ''

For example, the zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 6 preferably satisfies the following condition (15).
4.50 ≦ f _G1 / | f _G2 | ≦ 7.00 (15)
here,
f _G1 : composite focal length of the first lens group,
f _G2 is the combined focal length of the second lens group.

  The condition (15) defines the ratio of the focal lengths of the first lens group and the second lens group. If the lower limit of the condition (15) is not reached, the focal length of the first lens group becomes relatively small, and it becomes difficult to maintain the zooming action of the second lens group, and the optical performance is maintained while maintaining 10. There is a risk that it may be difficult to construct a zoom lens system having a zoom ratio of double or more. On the contrary, when the upper limit of the condition (15) is exceeded, the focal length of the second lens group becomes relatively small, and it may be difficult to correct the aberration generated in the second lens group.

The above effect can be further achieved by further satisfying at least one of the following conditions (15) ′ and (15) ″.
5.00 ≦ f _G1 / | f _G2 | (15) ′
f _G1 / | f _G2 | ≦ 6.00 (15) ″

  Each lens group constituting the zoom lens system according to Embodiments 1 to 6 includes a refractive lens element that deflects incident light by refraction (that is, a type in which deflection is performed at an interface between media having different refractive indexes). However, the present invention is not limited to this. For example, a diffractive lens element that deflects incident light by diffraction, a refractive / diffractive hybrid lens element that deflects incident light by a combination of diffractive action and refractive action, and a refractive index that deflects incident light according to the refractive index distribution in the medium Each lens group may be composed of a distributed lens element or the like. In particular, in a refractive / diffractive hybrid lens element, it is preferable to form a diffractive structure at the interface of media having different refractive indexes, since the wavelength dependency of diffraction efficiency is improved.

  Furthermore, in each embodiment, an optical low-pass filter, a face plate of an image sensor, or the like is equivalent to the object side of the image plane S (between the image plane S and the most image side lens surface of the fourth lens group G4). Although the configuration in which the parallel plate P is arranged is shown, as this low-pass filter, a birefringent low-pass filter made of quartz or the like whose predetermined crystal axis direction is adjusted, or a required optical cutoff frequency. A phase type low-pass filter or the like that achieves the characteristics by the diffraction effect can be applied.

(Embodiment 7)
FIG. 17 is a schematic configuration diagram of a digital still camera according to the seventh embodiment. In FIG. 17, the digital still camera includes an image pickup apparatus including a zoom lens system 1 and an image pickup device 2 that is a CCD, a liquid crystal monitor 3, and a housing 4. As the zoom lens system 1, the zoom lens system according to Embodiment 6 is used. In FIG. 17, the zoom lens system 1 is composed of a first lens group G1, a second lens group G2, an aperture stop A, a third lens group G3, and a fourth lens group G4. In the housing 4, the zoom lens system 1 is disposed on the front side, and the imaging element 2 is disposed on the rear side of the zoom lens system 1. A liquid crystal monitor 3 is disposed on the rear side of the housing 4, and an optical image of the subject by the zoom lens system 1 is formed on the image plane S.

  The lens barrel includes a main lens barrel 5, a movable lens barrel 6, and a cylindrical cam 7. When the cylindrical cam 7 is rotated, the first lens group G1, the second lens group G2, the aperture stop A, the third lens group G3, and the fourth lens group G4 move to predetermined positions on the basis of the image sensor 2, Zooming from the wide-angle end to the telephoto end can be performed. The fourth lens group G4 is movable in the optical axis direction by a focus adjustment motor.

  Thus, by using the zoom lens system according to Embodiment 6 for a digital still camera, it is possible to provide a small digital still camera that has a high ability to correct resolution and curvature of field and has a short overall lens length when not in use. it can. In the digital still camera shown in FIG. 17, any of the zoom lens systems according to Embodiments 1 to 5 may be used instead of the zoom lens system according to Embodiment 6. Further, the optical system of the digital still camera shown in FIG. 17 can be used for a digital video camera for moving images. In this case, not only a still image but also a moving image with high resolution can be taken.

  In the digital still camera according to the seventh embodiment, the zoom lens system according to the first to sixth embodiments is shown as the zoom lens system 1. However, these zoom lens systems need to use all zooming areas. There is no. That is, a range in which the optical performance is ensured according to a desired zooming area may be cut out and used as a zoom lens system having a lower magnification than the zoom lens system described in the first to sixth embodiments.

  Furthermore, in the seventh embodiment, an example in which the zoom lens system is applied to a so-called collapsible lens barrel is shown, but the present invention is not limited thereto. For example, a prism having an internal reflection surface or a surface reflection mirror may be disposed at an arbitrary position such as in the first lens group G1, and the zoom lens system may be applied to a so-called bent lens barrel. Furthermore, in Embodiment 7, some lenses constituting the zoom lens system such as the entire second lens group G2, the entire third lens group G3, the second lens group G2, or a part of the third lens group G3. The zoom lens system may be applied to a so-called sliding lens barrel in which the group is retracted from the optical axis when retracted.

  In addition, an imaging apparatus including the zoom lens system according to Embodiments 1 to 6 described above and an imaging element such as a CCD or CMOS is used as a monitoring camera in a mobile phone device, a PDA (Personal Digital Assistance), or a monitoring system. It can also be applied to Web cameras, in-vehicle cameras, and the like.

ここで、κは円錐定数、Ａ４、Ａ６、Ａ８、Ａ１０、Ａ１２、Ａ１４及びＡ１６は、それぞれ４次、６次、８次、１０次、１２次、１４次及び１６次の非球面係数である。 Hereinafter, numerical examples in which the zoom lens systems according to Embodiments 1 to 6 are specifically implemented will be described. In each numerical example, the unit of length in the table is “mm”, and the unit of angle of view is “°”. In each numerical example, r is a radius of curvature, d is a surface interval, nd is a refractive index with respect to the d line, and vd is an Abbe number with respect to the d line. In each numerical example, the surface marked with * is an aspherical surface, and the aspherical shape is defined by the following equation.

Here, κ is a conic constant, and A4, A6, A8, A10, A12, A14, and A16 are fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, and sixteenth-order aspheric coefficients, respectively. .

  2, 5, 8, 10, 12, and 15 are longitudinal aberration diagrams of the zoom lens systems according to Embodiments 1 to 6, respectively.

  In each longitudinal aberration diagram, (a) shows the aberration at the wide angle end, (b) shows the intermediate position, and (c) shows the aberration at the telephoto end. Each longitudinal aberration diagram shows spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)) in order from the left side. In the spherical aberration diagram, the vertical axis represents the F number (indicated by F in the figure), the solid line is the d line (d-line), the short broken line is the F line (F-line), and the long broken line is the C line (C- line). In the astigmatism diagram, the vertical axis represents the image height (indicated by H in the figure), the solid line represents the sagittal plane (indicated by s), and the broken line represents the meridional plane (indicated by m in the figure). is there. In the distortion diagram, the vertical axis represents the image height (indicated by H in the figure).

  3, 6, 13, and 16 are lateral aberration diagrams at the telephoto end of the zoom lens systems according to Embodiments 1, 2, 5, and 6, respectively.

  In each lateral aberration diagram, the upper three aberration diagrams show a basic state in which no image blur correction is performed at the telephoto end, and the lower three aberration diagrams move the entire third lens group G3 by a predetermined amount in a direction perpendicular to the optical axis. This corresponds to the image blur correction state at the telephoto end. Of the lateral aberration diagrams in the basic state, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows the lateral aberration at the image point of -70% of the maximum image height. Respectively. In each lateral aberration diagram in the image blur correction state, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows the image point at −70% of the maximum image height. Each corresponds to lateral aberration. In each lateral aberration diagram, the horizontal axis represents the distance from the principal ray on the pupil plane, the solid line is the d line (d-line), the short broken line is the F line (F-line), and the long broken line is the C line ( C-line) characteristics. In each lateral aberration diagram, the meridional plane is a plane including the optical axis of the first lens group G1 and the optical axis of the third lens group G3.

In the zoom lens system of each example, the movement amount in the direction perpendicular to the optical axis of the third lens group G3 in the image blur correction state at the telephoto end is as follows.
Example 1 0.135 mm
Example 2 0.142 mm
Example 5 0.135 mm
Example 6 0.135 mm

  When the shooting distance is ∞ and the zoom lens system is tilted by 0.3 ° at the telephoto end, the image decentering amount is when the entire third lens group G3 is translated by the above values in the direction perpendicular to the optical axis. Is equal to the amount of image eccentricity.

  As can be seen from the respective lateral aberration diagrams, the symmetry of the lateral aberration at the axial image point is good. Further, when the lateral aberration at the + 70% image point and the lateral aberration at the -70% image point are compared in the basic state, the curvature is small and the inclinations of the aberration curves are almost equal. It can be seen that the aberration is small. This means that sufficient imaging performance is obtained even in the image blur correction state. When the image blur correction angle of the zoom lens system is the same, the amount of parallel movement required for image blur correction decreases as the focal length of the entire zoom lens system decreases. Therefore, at any zoom position, it is possible to perform sufficient image blur correction without deteriorating the imaging characteristics for an image blur correction angle up to 0.3 °.

(Numerical example 1)
The zoom lens system of Numerical Example 1 corresponds to Embodiment 1 shown in FIG. Table 1 shows surface data of the zoom lens system of Numerical Example 1, Table 2 shows aspheric data, and Table 3 shows various data.

Table 1 (surface data)

Surface number rd nd vd
Object ∞
1 28.99500 0.75000 1.84666 23.8
2 19.08700 0.01000 1.56732 42.8
3 19.08700 2.84700 1.49700 81.6
4 103.92400 0.15000
5 19.82600 2.17900 1.72916 54.7
6 64.93200 Variable
7 44.87700 0.40000 1.88300 40.8
8 5.18600 2.92000
9 -29.16200 0.40000 1.78590 43.9
10 12.33600 0.47500
11 10.21400 1.34100 1.94595 18.0
12 47.83400 Variable
13 (Aperture) ∞ 0.30000
14 4.30100 1.76700 1.49700 81.6
15 8241.75900 1.15600
16 * 8.43400 1.39900 1.80359 40.8
17 47.78600 0.01000 1.56732 42.8
18 47.78600 0.40000 1.84666 23.8
19 5.30000 Variable
20 * 11.73300 1.57800 1.51788 70.1
21 * -1903.05100 variable
22 ∞ 0.78000 1.51680 64.2
23 ∞ (BF)
Image plane ∞

Table 2 (Aspheric data)

16th page
K = -1.08120E-01, A4 = -1.77815E-03, A6 = -2.10683E-04, A8 = 6.70181E-05
A10 = -2.73725E-05, A12 = 5.38765E-06, A14 = -5.55279E-07, A16 = 2.30717E-08
20th page
K = 0.00000E + 00, A4 = -7.73195E-04, A6 = 6.10146E-05, A8 = -8.73485E-06
A10 = 2.05233E-07, A12 = 1.29977E-08, A14 = -4.93132E-10, A16 = 4.24886E-13
21st page
K = 0.00000E + 00, A4 = -9.05532E-04, A6 = 7.99808E-05, A8 = -1.34302E-05
A10 = 7.25546E-07, A12 = -1.80811E-08, A14 = 3.94130E-10, A16 = -6.65586E-12

Table 3 (various data)

Zoom ratio 11.02510
Wide angle Medium telephoto Focal length 4.3006 13.7819 47.4146
F number 3.26027 4.27212 5.07918
Angle of View 42.8331 14.6873 4.2674
Image height 3.5000 3.6000 3.6000
Total lens length 43.0332 45.9184 54.8755
BF 0.88682 0.88842 0.88365
d6 0.3050 8.7502 18.1561
d12 15.2479 4.9989 1.2400
d19 3.8073 3.8429 12.7973
d21 3.9242 8.5760 2.9364
Entrance pupil position 11.6651 31.3726 103.4747
Exit pupil position -14.5110 -19.2329 -53.5837
Front principal point position 14.7645 35.7147 109.6143
Rear principal point position 38.7326 32.1365 7.4609

Single lens data Lens Start surface Focal length
1 1 -68.3446
2 3 46.5267
3 5 38.3600
4 7 -6.6721
5 9 -10.9840
6 11 13.4954
7 14 8.6579
8 16 12.5461
9 18 -7.0713
10 20 22.5233

Zoom lens group data Group Start surface Focal length Lens composition length Front principal point position Rear principal point position
1 1 31.49864 5.93600 0.99762 3.19693
2 7 -5.98512 5.53600 0.34799 1.33545
3 13 10.15272 5.03200 -2.46124 0.41427
4 20 22.52334 1.57800 0.00637 0.54447
Zoom lens group magnification Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 7 -0.27056 -0.43763 -1.40155
3 13 -0.70315 -1.95626 -1.41007
4 20 0.71768 0.51108 0.76168

(Numerical example 2)
The zoom lens system of Numerical Example 2 corresponds to Embodiment 2 shown in FIG. Table 4 shows surface data of the zoom lens system of Numerical Example 2, Table 5 shows aspheric data, and Table 6 shows various data.

Table 4 (surface data)

Surface number rd nd vd
Object ∞
1 30.54400 0.75000 1.84666 23.8
2 19.97400 0.01000 1.56732 42.8
3 19.97400 2.87000 1.49700 81.6
4 119.41300 0.15000
5 20.78100 2.17200 1.72916 54.7
6 68.25600 Variable
7 41.23000 0.40000 1.88300 40.8
8 5.16000 2.91700
9 -28.35400 0.40000 1.77250 49.6
10 11.39200 0.28600
11 9.45200 1.61100 1.92286 20.9
12 65.98200 Variable
13 (Aperture) ∞ 0.30000
14 4.35700 1.71500 1.49700 81.6
15 8241.75900 1.15600
16 * 7.96500 1.39900 1.80359 40.8
17 29.72600 0.01000 1.56732 42.8
18 29.72600 0.40000 1.84666 23.8
19 5.06400 Variable
20 * 11.62400 1.57800 1.51835 70.3
21 * -1903.05100 variable
22 ∞ 0.78000 1.51680 64.2
23 ∞ (BF)
Image plane ∞

Table 5 (Aspheric data)

16th page
K = 1.39341E-02, A4 = -1.64227E-03, A6 = -2.91556E-04, A8 = 1.15858E-04
A10 = -3.67861E-05, A12 = 5.42493E-06, A14 = -3.77635E-07, A16 = 9.18775E-09
20th page
K = 0.00000E + 00, A4 = -8.69167E-04, A6 = 8.47786E-05, A8 = -9.59803E-06
A10 = 1.40175E-07, A12 = 1.12463E-08, A14 = -2.70390E-10, A16 = 0.00000E + 00
21st page
K = 0.00000E + 00, A4 = -9.30204E-04, A6 = 9.56087E-05, A8 = -1.40798E-05
A10 = 6.99942E-07, A12 = -2.23827E-08, A14 = 5.20712E-10, A16 = 0.00000E + 00

Table 6 (various data)

Zoom ratio 11.22248
Wide angle Medium telephoto Focal length 4.3010 13.8474 48.2674
F number 3.29469 4.30198 5.08146
Angle of view 42.3477 14.5267 4.1832
Image height 3.5000 3.6000 3.6000
Total lens length 43.5388 46.0391 55.0983
BF 0.88401 0.87645 0.87539
d6 0.3248 9.1089 19.1293
d12 15.8067 4.9971 1.0000
d19 3.7184 3.6596 12.5064
d21 3.9009 8.4930 2.6832
Entrance pupil position 11.8334 31.7811 106.5538
Exit pupil position -14.2616 -18.7397 -51.0622
Front principal point position 14.9130 35.8533 109.9646
Rear principal point position 39.2379 32.1916 6.8309

Single lens data Lens Start surface Focal length
1 1 -70.4642
2 3 47.8040
3 5 40.1995
4 7 -6.7146
5 9 -10.4742
6 11 11.7933
7 14 8.7707
8 16 13.1627
9 18 -7.2633
10 20 22.2951

Zoom lens group data Group Start surface Focal length Lens composition length Front principal point position Rear principal point position
1 1 32.74603 5.95200 1.03339 3.23646
2 7 -6.27842 5.61400 0.30252 1.41714
3 13 10.26172 4.98000 -2.53747 0.35393
4 20 22.29513 1.57800 0.00631 0.54473
Zoom lens group magnification Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 7 -0.27150 -0.43781 -1.45325
3 13 -0.67567 -1.89263 -1.31556
4 20 0.71597 0.51034 0.77098

(Numerical Example 3)
The zoom lens system of Numerical Example 3 corresponds to Embodiment 3 shown in FIG. Table 7 shows surface data of the zoom lens system of Numerical Example 3, Table 8 shows aspheric data, and Table 9 shows various data.

Table 7 (surface data)

Surface number rd nd vd
Object ∞
1 28.83400 0.75000 1.84666 23.8
2 19.10600 0.01000 1.56732 42.8
3 19.10600 2.85000 1.49700 81.6
4 101.86400 0.15000
5 20.12000 2.17900 1.72916 54.7
6 67.88000 Variable
7 48.57300 0.40000 1.88300 40.8
8 5.25800 2.88300
9 -30.09700 0.40000 1.78590 43.9
10 11.97200 0.46400
11 10.02000 1.38900 1.94595 18.0
12 45.19300 Variable
13 (Aperture) ∞ 0.30000
14 * 4.07200 1.85400 1.51835 70.3
15 * -14.78000 1.10600
16 10.46100 0.40000 1.80518 25.5
17 3.45300 0.45000
18 4.62900 1.00100 1.60342 38.0
19 7.26800 Variable
20 * 12.44300 1.57700 1.51835 70.3
21 * -178.17400 Variable
22 ∞ 0.78000 1.51680 64.2
23 ∞ (BF)
Image plane ∞

Table 8 (Aspherical data)

14th page
K = 0.00000E + 00, A4 = -8.24968E-04, A6 = -1.09073E-06, A8 = 2.17711E-05
A10 = -5.02279E-06, A12 = 2.35314E-07, A14 = 1.63202E-07, A16 = -1.54658E-08
15th page
K = 0.00000E + 00, A4 = 1.49679E-03, A6 = 1.31240E-04, A8 = 1.46070E-06
A10 = -1.18079E-06, A12 = -9.13721E-08, A14 = 2.62896E-07, A16 = -2.45633E-08
20th page
K = 0.00000E + 00, A4 = -7.69541E-04, A6 = 7.69065E-05, A8 = -1.40933E-05
A10 = 9.19495E-07, A12 = -1.81967E-08, A14 = -1.78801E-09, A16 = 7.53515E-11
21st page
K = 0.00000E + 00, A4 = -7.47072E-04, A6 = 4.18687E-05, A8 = -9.53545E-06
A10 = 6.77844E-07, A12 = -2.96255E-08, A14 = 8.03400E-11, A16 = 2.04568E-11

Table 9 (various data)

Zoom ratio 11.02588
Wide angle Medium telephoto Focal length 4.2986 13.8551 47.3961
F number 3.28208 4.24530 5.13352
Angle of View 42.0251 14.6001 4.2709
Image height 3.4000 3.6000 3.6000
Total lens length 43.1677 45.8742 54.8407
BF 0.87410 0.86181 0.87475
d6 0.3050 8.8771 18.0441
d12 15.5017 5.0021 1.2400
d19 3.8901 3.6860 12.7948
d21 3.6538 8.5042 2.9441
Entrance pupil position 11.7092 31.8814 101.3999
Exit pupil position -15.4282 -19.8509 -59.3792
Front principal point position 14.8744 36.4685 111.5140
Rear principal point position 38.8691 32.0191 7.4446

Single lens data Lens Start surface Focal length
1 1 -69.3377
2 3 46.7831
3 5 38.4775
4 7 -6.7066
5 9 -10.8530
6 11 13.3538
7 14 6.3728
8 16 -6.5687
9 18 18.4881
10 20 22.5016

Zoom lens group data Group Start surface Focal length Lens composition length Front principal point position Rear principal point position
1 1 31.49909 5.93900 1.00554 3.20336
2 7 -5.98151 5.53600 0.36288 1.39105
3 13 10.16322 5.11100 -2.32440 0.11796
4 20 22.50158 1.57700 0.06799 0.60342
Zoom lens group magnification Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 7 -0.27048 -0.44170 -1.36721
3 13 -0.68864 -1.92377 -1.44020
4 20 0.73265 0.51764 0.76416

(Numerical example 4)
The zoom lens system of Numerical Example 4 corresponds to Embodiment 4 shown in FIG. Table 10 shows surface data of the zoom lens system of Numerical Example 4, Table 11 shows aspheric data, and Table 12 shows various data.

Table 10 (surface data)

Surface number rd nd vd
Object ∞
1 30.82100 0.75000 1.84666 23.8
2 19.80 200 0.01000 1.56732 42.8
3 19.80200 2.84100 1.49700 81.6
4 132.37900 0.15000
5 19.70800 2.19000 1.72916 54.7
6 63.77100 Variable
7 46.49600 0.40000 1.88300 40.8
8 5.15900 2.99000
9 -26.75700 0.40000 1.78590 43.9
10 13.20600 0.40800
11 10.12700 1.34000 1.94595 18.0
12 46.54600 Variable
13 (Aperture) ∞ 0.30000
14 * 4.69000 2.11400 1.51835 70.3
15 * -14.23800 1.13000
16 6.94600 0.91900 1.94595 18.0
17 3.99000 Variable
18 * 11.88000 1.57700 1.51835 70.3
19 * -613.12200 Variable
20 ∞ 0.78000 1.51680 64.2
21 ∞ (BF)
Image plane ∞

Table 11 (Aspheric data)

14th page
K = 0.00000E + 00, A4 = -6.98798E-04, A6 = -3.07231E-05, A8 = 4.14892E-05
A10 = -7.19360E-06, A12 = 8.33698E-08, A14 = 1.67474E-07, A16 = -1.49651E-08
15th page
K = 0.00000E + 00, A4 = 1.02954E-03, A6 = 2.16803E-04, A8 = -3.21361E-05
A10 = 3.94649E-06, A12 = 2.58926E-07, A14 = -6.31197E-09, A16 = -3.45461E-09
18th page
K = 0.00000E + 00, A4 = -2.31301E-04, A6 = -3.30169E-05, A8 = -5.02139E-06
A10 = 7.52561E-07, A12 = -5.25403E-08, A14 = 2.01872E-09, A16 = -4.40237E-11
19th page
K = 0.00000E + 00, A4 = -5.07083E-04, A6 = 2.66686E-05, A8 = -1.42819E-05
A10 = 1.13449E-06, A12 = -2.14192E-08, A14 = -1.36032E-09, A16 = 4.60748E-11

Table 12 (various data)

Zoom ratio 11.02420
Wide angle Medium telephoto Focal length 4.2999 13.8718 47.4034
F number 3.31040 4.20958 4.99163
Angle of View 41.5250 14.5528 4.2738
Image height 3.3500 3.6000 3.6000
Total lens length 43.3831 45.7414 54.4466
BF 0.87136 0.88634 0.87037
d6 0.3050 9.1454 18.3495
d12 15.6017 5.0041 1.2400
d17 4.8012 3.7877 12.7923
d19 3.5048 8.6189 2.8954
Entrance pupil position 11.6412 32.7101 105.6893
Exit pupil position -15.5987 -18.6607 -51.0614
Front principal point position 14.8185 36.7376 109.8228
Rear principal point position 39.0831 31.8696 7.0432

Single lens data Lens Start surface Focal length
1 1 -67.5261
2 3 46.4623
3 5 38.3143
4 7 -6.6017
5 9 -11.2015
6 11 13.4422
7 14 7.0758
8 16 -11.6760
9 18 22.5026

Zoom lens group data Group Start surface Focal length Lens composition length Front principal point position Rear principal point position
1 1 31.49935 5.94100 1.07105 3.27435
2 7 -5.98100 5.53800 0.35015 1.35673
3 13 10.16664 4.46300 -2.41163 0.14756
4 18 22.50262 1.57700 0.01976 0.55724
Zoom lens group magnification Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 7 -0.26946 -0.44781 -1.44049
3 13 -0.68706 -1.93046 -1.36656
4 18 0.73736 0.50942 0.76448

(Numerical example 5)
The zoom lens system of Numerical Example 5 corresponds to Embodiment 5 shown in FIG. Table 13 shows surface data of the zoom lens system of Numerical Example 5, Table 14 shows aspheric data, and Table 15 shows various data.

Table 13 (surface data)

Surface number rd nd vd
Object ∞
1 29.29600 0.75000 1.84666 23.8
2 19.18900 0.01000 1.56732 42.8
3 19.18900 2.85700 1.49700 81.6
4 108.03300 0.15000
5 20.45300 2.17600 1.72916 54.7
6 72.91900 Variable
7 51.45000 0.40000 1.88300 40.8
8 5.22500 2.88000
9 -33.13900 0.40000 1.78590 43.9
10 11.81100 0.46700
11 9.75900 1.38900 1.94595 18.0
12 40.80000 Variable
13 (Aperture) ∞ 0.30000
14 * 4.91700 1.83400 1.60602 57.4
15 -12.30000 0.01000 1.56732 42.8
16 -12.30000 0.74400 1.84666 23.8
17 -20.45800 1.34000
18 * 10.29900 0.80300 1.99540 20.7
19 5.31600 Variable
20 * 11.88800 1.57700 1.51835 70.3
21 * -586.41400 Variable
22 ∞ 0.78000 1.51680 64.2
23 ∞ (BF)
Image plane ∞

Table 14 (Aspherical data)

14th page
K = 0.00000E + 00, A4 = -4.87214E-04, A6 = -3.67232E-05, A8 = 1.22587E-05
A10 = -2.94245E-06, A12 = 3.29255E-07, A14 = -9.71641E-09, A16 = -7.68082E-10
18th page
K = 0.00000E + 00, A4 = -1.16235E-03, A6 = -7.02341E-05, A8 = 8.26548E-07
A10 = -1.03094E-06, A12 = 2.73287E-07, A14 = -5.65024E-08, A16 = 5.26646E-09
20th page
K = 0.00000E + 00, A4 = -5.35774E-04, A6 = 3.02823E-05, A8 = -9.38385E-06
A10 = 5.44017E-07, A12 = 4.39358E-09, A14 = -1.41360E-09, A16 = 2.98041E-11
21st page
K = 0.00000E + 00, A4 = -6.64748E-04, A6 = 3.66417E-05, A8 = -1.31889E-05
A10 = 1.02733E-06, A12 = -2.21503E-08, A14 = -8.57851E-10, A16 = 3.13948E-11

Table 15 (various data)

Zoom ratio 11.03744
Wide angle Medium telephoto Focal length 4.2998 13.8577 47.4583
F number 3.26307 4.22605 5.06442
Angle of View 42.8635 14.5180 4.2583
Image height 3.5000 3.6000 3.6000
Total lens length 43.1100 46.0464 54.9041
BF 0.87367 0.86814 0.86731
d6 0.3050 9.0407 18.2431
d12 15.2547 5.0015 1.2400
d19 3.9267 3.7030 12.8393
d21 3.8829 8.5661 2.8474
Entrance pupil position 11.6152 32.2976 103.7219
Exit pupil position -14.7562 -18.9976 -54.3396
Front principal point position 14.7321 36.4886 110.3829
Rear principal point position 38.8102 32.1888 7.4458

Single lens data Lens Start surface Focal length
1 1 -68.0081
2 3 46.4531
3 5 38.3148
4 7 -6.6130
5 9 -11.0366
6 11 13.2714
7 14 6.0392
8 16 -38.0210
9 18 -12.0029
10 20 22.4989

Zoom lens group data Group Start surface Focal length Lens composition length Front principal point position Rear principal point position
1 1 31.50001 5.94300 1.06957 3.26401
2 7 -5.99110 5.53600 0.33757 1.36227
3 13 10.15425 5.03100 -2.41145 0.42952
4 20 22.49886 1.57700 0.02066 0.55809
Zoom lens group magnification Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 7 -0.27002 -0.44538 -1.40992
3 13 -0.70167 -1.92719 -1.39365
4 20 0.72044 0.51254 0.76675

(Numerical example 6)
The zoom lens system of Numerical Example 6 corresponds to Embodiment 6 shown in FIG. Table 16 shows surface data of the zoom lens system of Numerical Example 6, Table 17 shows aspherical data, and Table 18 shows various data.

Table 16 (surface data)

Surface number rd nd vd
Object ∞
1 31.60900 0.75700 1.92286 20.9
2 22.12900 0.01000 1.56732 42.8
3 22.12900 2.85800 1.49700 81.6
4 221.46700 0.14400
5 19.82900 2.17900 1.72916 54.7
6 56.23800 Variable
7 44.93500 0.40100 1.88300 40.8
8 5.19000 2.94100
9 -28.98600 0.39900 1.78590 43.9
10 12.33500 0.47500
11 10.20700 1.34300 1.94595 18.0
12 47.99500 Variable
13 (Aperture) ∞ 0.30000
14 4.30200 1.77300 1.49700 81.6
15 6803.89600 1.15900
16 * 8.43500 1.39700 1.80359 40.8
17 49.88900 0.01000 1.56732 42.8
18 49.88900 0.39800 1.84666 23.8
19 5.29900 Variable
20 * 11.72100 1.58000 1.51835 70.3
21 * -1629.06500 Variable
22 ∞ 0.78000 1.51680 64.2
23 ∞ (BF)
Image plane ∞

Table 17 (Aspherical data)

16th page
K = -1.26014E-01, A4 = -1.78233E-03, A6 = -2.10674E-04, A8 = 6.69814E-05
A10 = -2.74048E-05, A12 = 5.39168E-06, A14 = -5.55222E-07, A16 = 2.30211E-08
20th page
K = 0.00000E + 00, A4 = -7.75064E-04, A6 = 6.14125E-05, A8 = -8.73167E-06
A10 = 2.05005E-07, A12 = 1.29818E-08, A14 = -4.93909E-10, A16 = 6.87949E-13
21st page
K = 0.00000E + 00, A4 = -9.03803E-04, A6 = 7.96172E-05, A8 = -1.34273E-05
A10 = 7.25544E-07, A12 = -1.80856E-08, A14 = 3.95732E-10, A16 = -6.69981E-12

Table 18 (various data)

Zoom ratio 11.02287
Wide angle Medium telephoto Focal length 4.3008 13.8156 47.4068
F number 3.26165 4.24209 5.08129
Angle of View 42.5203 14.6148 4.2714
Image height 3.5000 3.6000 3.6000
Total lens length 43.1633 45.9912 54.9059
BF 0.88315 0.88011 0.86611
d6 0.3402 8.9311 18.1547
d12 15.2947 5.0260 1.2415
d19 3.8356 3.6957 12.7992
d21 3.9057 8.5543 2.9404
Entrance pupil position 11.7233 32.1123 103.6880
Exit pupil position -14.5669 -18.9414 -53.9620
Front principal point position 14.8268 36.2985 110.1048
Rear principal point position 38.8626 32.1757 7.4991

Single lens data Lens Start surface Focal length
1 1 -83.1380
2 3 49.2339
3 5 40.9708
4 7 -6.6768
5 9 -10.9635
6 11 13.4721
7 14 8.6607
8 16 12.4456
9 18 -7.0312
10 20 22.4580

Zoom lens group data Group Start surface Focal length Lens composition length Front principal point position Rear principal point position
1 1 31.49407 5.94800 0.97373 3.20547
2 7 -5.98650 5.55900 0.35026 1.33891
3 13 10.16527 5.03700 -2.46799 0.41145
4 20 22.45799 1.58000 0.00744 0.54649
Zoom lens group magnification Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 7 -0.27119 -0.44398 -1.40526
3 13 -0.70146 -1.93358 -1.40649
4 20 0.71785 0.51099 0.76159

  Table 19 below shows corresponding values of the respective conditions in the zoom lens systems of the respective numerical examples.

Table 19 (corresponding values of conditions)

  The zoom lens system according to the present invention is applicable to digital input devices such as a digital camera, a mobile phone device, a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a web camera, an in-vehicle camera, etc. It is suitable for a photographing optical system that requires high image quality.

Lens arrangement diagram showing an infinitely focused state of the zoom lens system according to Embodiment 1 (Example 1) Longitudinal aberration diagram of the zoom lens system according to Example 1 in an infinitely focused state Lateral aberration diagram in the basic state where image blur correction is not performed and in the image blur correction state at the telephoto end of the zoom lens system according to Embodiment 1 Lens arrangement diagram showing an infinitely focused state of the zoom lens system according to Embodiment 2 (Example 2) Longitudinal aberration diagram of the zoom lens system according to Example 2 in an infinitely focused state Lateral aberration diagrams in the basic state where image blur correction is not performed and in the image blur correction state at the telephoto end of the zoom lens system according to Example 2 Lens arrangement diagram showing an infinitely focused state of the zoom lens system according to Embodiment 3 (Example 3) Longitudinal aberration diagram of the zoom lens system according to Example 3 in an infinitely focused state Lens arrangement diagram showing an infinitely focused state of the zoom lens system according to Embodiment 4 (Example 4) Longitudinal aberration diagram of the zoom lens system according to Example 4 in an infinitely focused state Lens arrangement diagram showing an infinitely focused state of a zoom lens system according to Embodiment 5 (Example 5) Longitudinal aberration diagram of the zoom lens system according to Example 5 in focus at infinity Lateral aberration diagrams in the basic state where image blur correction is not performed and in the image blur correction state at the telephoto end of the zoom lens system according to Example 5 Lens arrangement diagram showing an infinitely focused state of a zoom lens system according to Embodiment 6 (Example 6) Longitudinal aberration diagram of the zoom lens system according to Example 6 in focus at infinity Lateral aberration diagrams in the basic state where image blur correction is not performed and in the image blur correction state at the telephoto end of the zoom lens system according to Example 6 Schematic configuration diagram of a digital still camera according to Embodiment 7

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group L1 1st lens element L2 2nd lens element L3 3rd lens element L4 4th lens element L5 5th lens element L6 6th lens element L7 7th lens element L8 8th lens element L9 9th lens element L10 10th lens element A Aperture stop P Parallel plate S Image plane 1 Zoom lens system 2 Imaging element 3 Liquid crystal monitor 4 Case 5 Main lens barrel 6 Moving lens barrel 7 Cylindrical cam

Claims (14)

In order from the object side to the image side, a first lens group having a positive power, a second lens group having a negative power, a third lens group having a positive power, and a fourth lens having a positive power A group of
The first lens group is composed of three lens elements,
The second lens group is composed of three lens elements,
During zooming from the wide-angle end to the telephoto end during imaging, the first lens group, the second lens group, the third lens group, and the fourth lens group have an air space between each lens group and the lens group. Move each along the optical axis so that it changes,
Zoom lens system satisfying the following conditions (7), (8), (a-2) and (b):
−3.12 ≦ T _G1 / f _W ≦ −2.36 (7)
1.26 ≦ T _G2 / f _W ≦ 1.78 (8)
ω _W ≧ 37 (a-2)
f _T / f _W ≧ 10 (b)
here,
T _G1 : the amount of movement on the optical axis from the object side to the image side of the first lens group during zooming from the wide-angle end to the telephoto end during imaging,
T _G2 : the amount of movement on the optical axis from the object side to the image side of the second lens group during zooming from the wide-angle end to the telephoto end during imaging,
ω _W : Half angle of view (°) at the wide-angle end,
f _T : focal length of the entire system at the telephoto end,
f _W : the focal length of the entire system at the wide angle end. The zoom lens system according to claim 1, wherein the zoom lens system satisfies the following condition (10):
4.00 ≦ m _2T / m _2W ≦ 8.00 (10)
here,
m _2T : lateral magnification of the second lens unit at the telephoto end and infinite focus state,
m _2W : The lateral magnification of the second lens group at the wide-angle end and at infinity in-focus state. The zoom lens system according to claim 1, satisfying the following condition (11):
1.00 ≦ L _T / f _T ≦ 2.00 (11)
here,
L _T : Total lens length at the telephoto end (distance from the most object side surface of the first lens group to the image plane),
f _T is the focal length of the entire system at the telephoto end. The zoom lens system according to claim 1, satisfying the following condition (12):
1.00 ≦ f _T / f _G1 ≦ 2.00 (12)
here,
f _G1 : composite focal length of the first lens group,
f _T is the focal length of the entire system at the telephoto end. The zoom lens system according to claim 1, satisfying the following condition (13):
1.00 ≦ L _W / f _G1 ≦ 2.00 (13)
here,
L _W : total lens length at the wide-angle end (distance from the most object side surface of the first lens group to the image plane),
f _G1 is the combined focal length of the first lens group. The zoom lens system according to claim 1, satisfying the following condition (14):
1.50 ≦ L _T / f _G1 ≦ 2.00 (14)
here,
L _T : Total lens length at the telephoto end (distance from the most object side surface of the first lens group to the image plane),
f _G1 is the combined focal length of the first lens group. The zoom lens system according to claim 1, satisfying the following condition (15):
4.50 ≦ f _G1 / | f _G2 | ≦ 7.00 (15)
here,
f _G1 : composite focal length of the first lens group,
f _G2 is the combined focal length of the second lens group.   Of the three lens elements constituting the first lens group and the three lens elements constituting the second lens group, only the object side surface of the lens element arranged at the center of the second lens group has a negative radius of curvature. The zoom lens system according to claim 1, comprising:   The zoom lens system according to claim 1, wherein the third lens group includes two or three lens elements.   The zoom lens system according to claim 9, wherein the third lens group includes a lens element having positive power on the most object side.   10. The zoom lens system according to claim 9, wherein the third lens group includes at least one lens element having a concave surface on the image side and having a negative power.   The zoom lens system according to claim 1, wherein the fourth lens group includes one lens element having positive power. An imaging apparatus capable of outputting an optical image of an object as an electrical image signal,
A zoom lens system that forms an optical image of the object;
An image sensor that converts an optical image formed by the zoom lens system into an electrical image signal;
The zoom lens system is
In order from the object side to the image side, a first lens group having a positive power, a second lens group having a negative power, a third lens group having a positive power, and a fourth lens having a positive power A group of
The first lens group is composed of three lens elements,
The second lens group is composed of three lens elements,
During zooming from the wide-angle end to the telephoto end during imaging, the first lens group, the second lens group, the third lens group, and the fourth lens group have an air space between each lens group and the lens group. Move each along the optical axis so that it changes,
The following conditions (7), (8), (a-2) and (b):
−3.12 ≦ T _G1 / f _W ≦ −2.36 (7)
1.26 ≦ T _G2 / f _W ≦ 1.78 (8)
ω _W ≧ 37 (a-2)
f _T / f _W ≧ 10 (b)
(here,
T _G1 : the amount of movement on the optical axis from the object side to the image side of the first lens group during zooming from the wide-angle end to the telephoto end during imaging,
T _G2: moving amount of the optical axis from a wide-angle end at the time of imaging during zooming to the telephoto end, from the object side to the image side of the second lens group,
ω _W : Half angle of view (°) at the wide-angle end,
f _T : focal length of the entire system at the telephoto end,
f _W is the focal length of the entire system at the wide-angle end)
An image pickup apparatus that is a zoom lens system satisfying the above. A camera that converts an optical image of an object into an electrical image signal, and displays and stores the converted image signal;
An image pickup apparatus including a zoom lens system that forms an optical image of an object, and an image sensor that converts an optical image formed by the zoom lens system into an electrical image signal;
The zoom lens system is
In order from the object side to the image side, a first lens group having a positive power, a second lens group having a negative power, a third lens group having a positive power, and a fourth lens having a positive power A group of
The first lens group is composed of three lens elements,
The second lens group is composed of three lens elements,
During zooming from the wide-angle end to the telephoto end during imaging, the first lens group, the second lens group, the third lens group, and the fourth lens group have an air space between each lens group and the lens group. Move each along the optical axis so that it changes,
The following conditions (7), (8), (a-2) and (b):
−3.12 ≦ T _G1 / f _W ≦ −2.36 (7)
1.26 ≦ T _G2 / f _W ≦ 1.78 (8)
ω _W ≧ 37 (a-2)
f _T / f _W ≧ 10 (b)
(here,
T _G1 : the amount of movement on the optical axis from the object side to the image side of the first lens group during zooming from the wide-angle end to the telephoto end during imaging,
T _G2 : the amount of movement on the optical axis from the object side to the image side of the second lens group during zooming from the wide-angle end to the telephoto end during imaging,
ω _W : Half angle of view (°) at the wide-angle end,
f _T : focal length of the entire system at the telephoto end,
f _W is the focal length of the entire system at the wide-angle end)
A zoom lens system that satisfies the requirements.

Images