JP5519928B2 - Zoom lens system, imaging device and camera - Google Patents

Description

  The present invention relates to a zoom lens system, an imaging apparatus, and a camera. In particular, the present invention provides a high-performance zoom lens system that has a high resolution and a relatively high zooming ratio of 4 times or more while having a small overall lens length and a small size, and that can be sufficiently adapted to wide-angle shooting, and the zoom lens The present invention relates to an imaging apparatus including a system, and a thin and compact camera including the imaging apparatus.

  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, in recent years, there has been a demand for a thin digital camera with the highest priority on storage and portability. As one of means for realizing such a thin digital camera, various zoom lens systems for bending light rays from an object have been proposed.

  In Patent Document 1, in order from an object, a first lens group that has a negative refractive power that is fixed during zooming, a second lens group that includes a prism for bending an optical path that is fixed and does not have a refractive power during zooming, and moves during zooming. Disclosed is a zoom lens including a third lens group having a positive refractive power, a fourth lens group having a negative refractive power that moves during zooming, and a fifth lens group that has a fixed positive refractive power during zooming. Yes.

  Patent Document 2 has a positive lens group, a negative lens group, and a diaphragm, a negative lens group is disposed on the object side of the diaphragm, and the negative lens group has a cemented lens in which a plurality of lenses are cemented. Regarding at least one lens constituting the cemented lens, the physical properties of the glass material are specified under two conditions, and an imaging optical system having a prism for bending the optical path of the optical system is disclosed.

  Patent Document 3 has a plurality of lens groups that image light from the object side on the image plane of the image sensor, and the plurality of lens groups have negative power in order from the object side to the image side. The second lens in the in-plane direction perpendicular to the optical axis direction includes at least a first lens group, a second lens group having positive power, a third lens group having negative power, and a fourth lens group having positive power. A zooming optical system is disclosed in which image blur on the image plane is corrected by moving the group, and the first lens group includes an optical axis changing element.

Patent Document 4 has a positive lens group, a negative lens group, and a stop, a negative lens group is disposed on the image plane side from the stop, and the negative lens group has a cemented lens in which a plurality of lenses are cemented. Further, the physical properties of the glass material of at least one lens constituting the cemented lens are specified under three conditions, and an imaging optical system having a prism for bending the optical path of the optical system is disclosed.
JP 2008-197594 A JP 2008-191306 A JP 2007-279147 A JP 2007-108715 A

  However, the zoom lenses and optical systems disclosed in Patent Documents 1 to 4 are all reduced in size so that they can be applied to thin and compact digital cameras, but the zooming ratio is as low as about three times or less. However, it cannot satisfy the recent demand for digital cameras.

  An object of the present invention includes a high-performance zoom lens system having a high resolution, a relatively high zooming ratio and a sufficient adaptability for wide-angle shooting, and the zoom lens system. An imaging device and a thin and compact camera including the imaging device are provided.

One of the above objects is achieved by the following zoom lens system. That is, the present invention
A zoom lens system having a plurality of lens groups each including at least one lens element and performing zooming by changing an interval between the lens groups;
In order from the object side to the image side, a first lens group having negative power, a second lens group having positive power, a third lens group having negative power, and a fourth lens having positive power A group of
During zooming from the wide-angle end to the telephoto end during imaging , the air gap between the first lens group and the second lens group, the air gap between the second lens group and the third lens group, and the first Zooming is performed by moving the lens group along the optical axis so that the air gap between the third lens group and the fourth lens group changes,
The first lens group includes a lens element having a reflecting surface for bending a light beam from an object;
The following conditions (1):
0.20 <| f _G1 | / f _T ≦ 0.380 (1)
(However, f _T / f _W ≧ 4.0)
(here,
f _G1 : composite focal length of the first lens group,
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 the above.

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
A zoom lens system having a plurality of lens groups each including at least one lens element and performing zooming by changing an interval between the lens groups;
In order from the object side to the image side, a first lens group having negative power, a second lens group having positive power, a third lens group having negative power, and a fourth lens having positive power A group of
During zooming from the wide-angle end to the telephoto end during imaging , the air gap between the first lens group and the second lens group, the air gap between the second lens group and the third lens group, and the first Zooming is performed by moving the lens group along the optical axis so that the air gap between the third lens group and the fourth lens group changes,
The first lens group includes a lens element having a reflecting surface for bending a light beam from an object;
The following conditions (1):
0.20 <| f _G1 | / f _T ≦ 0.380 (1)
(However, f _T / f _W ≧ 4.0)
(here,
f _G1 : composite focal length of the first lens group,
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 the above.

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
A zoom lens system having a plurality of lens groups each including at least one lens element and performing zooming by changing an interval between the lens groups;
In order from the object side to the image side, a first lens group having negative power, a second lens group having positive power, a third lens group having negative power, and a fourth lens having positive power A group of
During zooming from the wide-angle end to the telephoto end during imaging , the air gap between the first lens group and the second lens group, the air gap between the second lens group and the third lens group, and the first Zooming is performed by moving the lens group along the optical axis so that the air gap between the third lens group and the fourth lens group changes,
The first lens group includes a lens element having a reflecting surface for bending a light beam from an object;
The following conditions (1):
0.20 <| f _G1 | / f _T ≦ 0.380 (1)
(However, f _T / f _W ≧ 4.0)
(here,
f _G1 : composite focal length of the first lens group,
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, the overall length of the lens (distance from the most object side surface of the first lens group to the image plane) is short and compact, but the resolution is high, the zooming ratio is 4 times or more, and the wide angle is wide. It is possible to provide a high-performance zoom lens system that can be sufficiently adapted to photographing, an imaging apparatus including the zoom lens system, and a thin and compact camera including the imaging apparatus.

(Embodiments 1 to 4)
1, 4, 7, and 10 are lens arrangement diagrams of the zoom lens systems according to Embodiments 1 to 4, respectively. Note that in this specification, the third embodiment is a reference embodiment.

1, 4, 7 and 10 all show a 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 ). Also, in each figure, the broken line arrows provided between FIGS. (A) and (b) are obtained by connecting the positions of the lens groups in the wide-angle end, the intermediate position, and the telephoto end in order from the top. Straight line. Therefore, between the wide-angle end and the intermediate position, and between the intermediate position and the telephoto end are simply connected by a straight line, which is different from the actual movement of each lens group. 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 negative power, a second lens group G2 having positive power, and a first lens group having negative power. 3 lens group G3 and 4th lens group G4 which has positive power are provided. The second lens element L2 (prism) in the first lens group G1 corresponds to a lens element that has a reflecting surface that bends a light beam from an object, for example, bends an axial principal ray from the object by approximately 90 °. The position is omitted. In the zoom lens system according to each embodiment, the lens element having a reflective surface is a prism, but the lens element having the reflective surface may be, for example, a mirror element. In addition, as will be described later, the prisms arranged in the zoom lens system according to each embodiment are both flat on the entrance surface and the exit surface, but at least one of the entrance surface and the exit surface depends on the lens configuration. It may be convex or concave.

  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 distance between the second lens group G2 and the third lens group G3, and the third lens group G3 and the third lens group G3. The second lens group G2 and the third lens group G3 move in the direction along the optical axis so that the distance from the four lens group G4 changes. 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, and 10, 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). Are 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 and 10, an aperture stop A is provided on the most object side of the second lens group G2, that is, between the first lens group G1 and the second lens group G2. A moves on the optical axis integrally with the second lens group G2 during zooming from the wide-angle end to the telephoto end during imaging.

  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. A second lens element L2 (prism) having both a plane of incidence and an exit plane and having a reflecting surface, a negative meniscus third lens element L3 having a convex surface facing the image side, and a convex surface facing the image side It consists of a positive meniscus fourth lens element L4. Among these, the third lens element L3 and the fourth lens element L4 are cemented. The first lens element L1 has an aspheric image side surface.

  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 biconvex fifth lens element L5, a biconvex sixth lens element L6, and both It consists of a concave seventh lens element L7 and a biconvex eighth lens element L8. Among these, the sixth lens element L6 and the seventh lens element L7 are cemented. In addition, both the fifth lens element L5 and the eighth lens element L8 have an aspheric object side surface.

  In the zoom lens system according to Embodiment 1, the third lens unit G3 comprises solely a bi-concave ninth lens element L9. The ninth lens element L9 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 second lens group G2 and the third lens group G3 are positioned at the telephoto end at the wide-angle end. The first lens group G1 and the fourth lens group G4 are fixed with respect to the image plane. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the fourth lens. The second lens group G2 and the third lens group G3 move along the optical axis so that the distance from the group G4 changes.

  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 second lens element L2 (prism) that is flat on both the entrance surface and the exit surface and has a reflection surface, a biconcave third lens element L3, and a biconvex fourth lens element L4. Among these, the third lens element L3 and the fourth lens element L4 are cemented. The first lens element L1 has an aspheric image side surface.

  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 biconvex fifth lens element L5, a biconvex sixth lens element L6, and both It consists of a concave seventh lens element L7 and a biconvex eighth lens element L8. Among these, the sixth lens element L6 and the seventh lens element L7 are cemented. In addition, both the fifth lens element L5 and the eighth lens element L8 have an aspheric object side surface.

  In the zoom lens system according to Embodiment 2, the third lens unit G3 comprises solely a bi-concave ninth lens element L9. The ninth lens element L9 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 second lens group G2 and the third lens group G3 are positioned at the telephoto end at the wide-angle end. The first lens group G1 and the fourth lens group G4 are fixed with respect to the image plane. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the fourth lens. The second lens group G2 and the third lens group G3 move along the optical axis so that the distance from the group G4 changes.

  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. A second lens element L2 (prism) having both a plane of incidence and an exit plane and having a reflecting surface, a negative meniscus third lens element L3 having a convex surface facing the image side, and a convex surface facing the image side It consists of a positive meniscus fourth lens element L4. Among these, the third lens element L3 and the fourth lens element L4 are cemented. The first lens element L1 has an aspheric image side surface.

  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 biconvex fifth lens element L5, a biconvex sixth lens element L6, and both It consists of a concave seventh lens element L7 and a biconvex eighth lens element L8. Among these, the sixth lens element L6 and the seventh lens element L7 are cemented. In addition, both the fifth lens element L5 and the eighth lens element L8 have an aspheric object side surface.

  In the zoom lens system according to Embodiment 3, the third lens unit G3 comprises solely a bi-concave ninth lens element L9. The ninth lens element L9 has an aspheric object side surface.

  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 second lens group G2 and the third lens group G3 are positioned at the telephoto end at the wide-angle end. The first lens group G1 and the fourth lens group G4 are fixed with respect to the image plane. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the fourth lens. The second lens group G2 and the third lens group G3 move along the optical axis so that the distance from the group G4 changes.

  As shown in FIG. 10, 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 second lens element L2 (prism) that is flat on both the entrance surface and the exit surface and has a reflection surface, a biconcave third lens element L3, and a biconvex fourth lens element L4. Among these, the third lens element L3 and the fourth lens element L4 are cemented. The first lens element L1 has two aspheric surfaces.

  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 biconvex fifth lens element L5, a biconvex sixth lens element L6, and both It consists of a concave seventh lens element L7 and a biconvex eighth lens element L8. Among these, the sixth lens element L6 and the seventh lens element L7 are cemented. In addition, both the fifth lens element L5 and the eighth lens element L8 have an aspheric object side surface.

  In the zoom lens system according to Embodiment 4, the third lens unit G3 comprises solely a bi-concave ninth lens element L9. The ninth lens element L9 has an aspheric object side surface.

  In the zoom lens system according to Embodiment 4, 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 4, 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 4, during zooming from the wide-angle end to the telephoto end during imaging, the second lens group G2 and the third lens group G3 are positioned at the telephoto end at the wide-angle end. The first lens group G1 and the fourth lens group G4 are fixed with respect to the image plane. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the fourth lens. The second lens group G2 and the third lens group G3 move along the optical axis so that the distance from the group G4 changes.

  In the zoom lens systems according to Embodiments 1 to 4, the first lens group G1 has a reflecting surface that can bend light rays from an object, for example, can bend an axial principal ray from an object by approximately 90 °. Since the second lens element L2 (prism) is included, the zoom lens system can be made thin in the optical axis direction of the axial ray from the object in the imaging state.

  In the zoom lens systems according to Embodiments 1 to 4, since the first lens group G1 does not move along the optical axis during zooming from the wide-angle end to the telephoto end during imaging, the zoom lens system is housed. As the lens barrel, a lens barrel that does not change its shape due to zooming can be used, and a camera with a high degree of freedom in shape and excellent impact resistance can be manufactured.

  In the zoom lens systems according to Embodiments 1 to 4, the third lens group G3, which is the succeeding lens group on the most object side disposed on the image side of the second lens group G2, has negative power. The third lens group G3 having the following power can be moved during zooming to contribute to zooming, and the zooming ratio can be increased to four times or more while keeping the total lens length short.

  In the zoom lens systems according to Embodiments 1 to 4, the first lens group G1, the second lens group G2, and the third lens that is the most object side subsequent lens group disposed on the image side of the second lens group G2. Each group G3 includes at least one lens element having an aspherical surface. Thus, by disposing a lens element having an aspheric surface in the first lens group G1, distortion can be corrected well, and by disposing a lens element having an aspheric surface in the second lens group G2. Spherical aberration can be corrected satisfactorily, and by placing a lens element having an aspheric surface in the third lens group G3, curvature of field can be corrected well.

  In the zoom lens systems according to Embodiments 1 to 4, since the aperture stop A is disposed between the first lens group G1 and the second lens group G2, the effective lens diameter of the first lens group G1 is reduced. Thus, the first lens group G1 including the second lens element L2 having a reflecting surface can be configured more compactly.

  The zoom lens systems according to Embodiments 1 to 4 have the four-group configuration of the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4. The number of lens groups is not particularly limited as long as the lens system includes a first lens group having negative power, a second lens group having positive power, and at least one subsequent lens group having power. It may be a three-group configuration, a four-group configuration, or any other configuration.

  As described above, it is preferable that the third lens group G3, which is the subsequent lens group on the most object side, has a negative power, but the power of each subsequent lens group is not particularly limited.

  In the zoom lens systems according to Embodiments 1 to 4, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group are used during zooming from the wide-angle end to the telephoto end during imaging. Among G4, the second lens group G2 and the third lens group G3 are moved along the optical axis to perform zooming. The first lens group G1, the second lens group G2, the third lens group G3, and the third lens group G3 By moving any lens group of the four lens groups G4, or some sub-lens groups of each lens group in a direction perpendicular to the optical axis, the image point movement due to vibration of the entire system is corrected, that is, Image blur due to camera shake, vibration, or the like can be optically corrected.

  When correcting the image point movement due to the vibration of the entire system, for example, by moving the fourth lens group G4 in a direction orthogonal to the optical axis, while 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 4. 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, as in the zoom lens systems according to Embodiments 1 to 4, the zoom lens system includes a plurality of lens groups each including at least one lens element, and performs zooming by changing the interval between the lens groups. In order from the object side to the image side, the first lens group having negative power, the second lens group having positive power, the third lens group having negative power, and the positive power An air gap between the first lens group and the second lens group and an air gap between the second lens group and the third lens group during zooming from the wide-angle end to the telephoto end during imaging. And a reflecting surface on which the first lens unit bends light rays from the object by moving the lens unit along the optical axis so as to change the air gap between the third lens unit and the fourth lens unit. (Hereinafter referred to as this label). The's configuration, the basic configuration of) a zoom lens system of the embodiment satisfies the following condition (1).
0.20 <| f _G1 | / f _T ≦ 0.380 (1)
(However, f _T / f _W ≧ 4.0)
here,
f _G1 : composite focal length of the first lens group,
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 (1) is a condition relating to the focal length of the first lens group and the focal length of the entire system at the telephoto end. If the lower limit of the condition (1) is not reached, the focal length of the first lens group is shortened, and the image plane performance at the wide angle end is deteriorated. On the contrary, if the upper limit of condition (1) is exceeded, the amount of movement of the second lens group at the time of zooming becomes large, and the lens system cannot be downsized.

In addition, when the following condition (1) ′ is further satisfied, the above effect can be further achieved.
0.27 <| f _G1 | / f _T (1) ′
(However, f _T / f _W ≧ 4.0)

The conditions (1), (1) ′, and (1) ″ are more preferably satisfied under the following conditions.
f _T / f _W ≧ 4.3

For example, a zoom lens system having a basic configuration like the zoom lens systems according to Embodiments 1 to 4 preferably satisfies the following condition (2).
0.20 <f _G2 / f _T <0.62 (2)
(However, f _T / f _W ≧ 4.0)
here,
f _G2 : Composite focal length of the second lens group,
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 (2) is a condition relating to the focal length of the second lens group and the focal length of the entire system at the telephoto end. If the lower limit of condition (2) is not reached, spherical aberration at the telephoto end may be deteriorated. On the contrary, if the upper limit of the condition (2) is exceeded, the amount of movement of the second lens unit at the time of zooming becomes large and it may be difficult to reduce the size of the lens system.

In addition, when the following condition (2) ′ is further satisfied, the above effect can be further achieved.
0.31 <f _G2 / f _T (2) ′
(However, f _T / f _W ≧ 4.0)

The conditions (2) and (2) ′ are more preferably satisfied under the following conditions.
f _T / f _W ≧ 4.3

  Each lens group constituting the zoom lens system according to Embodiments 1 to 4 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 5)
FIG. 13 is a schematic configuration diagram of a digital still camera according to the fifth embodiment. In FIG. 13, 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 1 is used. In FIG. 13, the zoom lens system 1 includes a first lens group G1, an aperture stop A, a second lens group G2, 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.

  Thus, by using the zoom lens system according to Embodiment 1 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. 13, any of the zoom lens systems according to Embodiments 2 to 4 may be used instead of the zoom lens system according to Embodiment 1. The optical system of the digital still camera shown in FIG. 13 can also 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 fifth embodiment, the zoom lens system according to the first to fourth embodiments is shown as the zoom lens system 1, but these zoom lens systems need to use all zooming areas. There is no. That is, a range in which the optical performance is ensured may be cut out according to a desired zooming area, and used as a zoom lens system having a lower magnification than the zoom lens system described in the first to fourth embodiments.

  In addition, an imaging apparatus including the zoom lens system according to Embodiments 1 to 4 described above and an imaging element such as a CCD or a 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及びＡ１０は、それぞれ４次、６次、８次及び１０次の非球面係数である。なお、本明細書において、数値実施例（実施例）３は数値参考例（参考例）である。 Hereinafter, numerical examples in which the zoom lens systems according to Embodiments 1 to 4 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, and A10 are fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, respectively. In the present specification, Numerical Example (Example) 3 is a numerical reference example (reference example).

  2, 5, 8 and 11 are longitudinal aberration diagrams of the zoom lens systems according to Embodiments 1 to 4, 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, 9 and 12 are lateral aberration diagrams at the telephoto end of the zoom lens systems according to Embodiments 1 to 4, respectively.

  In each lateral aberration diagram, the upper three aberration diagrams show a basic state where image blur correction is not performed at the telephoto end, and the lower three aberration diagrams show that the entire fourth lens group G4 is moved 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 75% 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 −75% of the maximum image height. Respectively. Of the lateral aberration diagrams in the image blur correction state, the upper stage is the lateral aberration at the image point of 75% of the maximum image height, the middle stage is the lateral aberration at the axial image point, and the lower stage is at the image point of -75% 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 fourth lens group G4.

In the zoom lens system of each example, the amount of movement in the direction perpendicular to the optical axis of the fourth lens group G4 in the image blur correction state at the telephoto end is as follows.
Example 1 0.321 mm
Example 2 0.327 mm
Example 3 0.389 mm
Example 4 0.278 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 fourth lens group G4 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 + 75% image point and the lateral aberration at the −75% 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. Accordingly, 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 65.98770 0.70000 1.80470 41.0
2 * 10.42920 2.15000
3 ∞ 8.70000 1.84666 23.8
4 ∞ 2.25880
5 -6.73950 0.40000 1.72916 54.7
6 -156.11850 1.35690 1.84666 23.8
7 -13.29920 Variable
8 (Aperture) ∞ -0.20000
9 * 6.96010 2.37360 1.51443 63.3
10 -58.40670 0.47960
11 10.60450 2.41110 1.49700 81.6
12 -13.18500 0.40000 1.80610 33.3
13 11.01460 0.52340
14 * 14.63870 1.72540 1.51443 63.3
15 -13.70590 Variable
16 * -21.97800 0.70000 1.60602 57.4
17 7.83670 Variable
18 * 14.92530 3.19200 1.60602 57.4
19 * -15.19790 3.00000
20 ∞ 0.90000 1.51680 64.2
21 ∞ (BF)
Image plane ∞

Table 2 (Aspheric data)

Second side
K = 0.00000E + 00, A4 = -1.49464E-04, A6 = -1.58314E-06, A8 = 4.17563E-09
A10 = -4.79826E-10
9th page
K = -5.82917E-01, A4 = 1.30605E-04, A6 = 1.98173E-08, A8 = 9.67527E-08
A10 = 9.66103E-10
14th page
K = 0.00000E + 00, A4 = -1.03877E-03, A6 = -5.40190E-06, A8 = -9.66942E-07
A10 = 0.00000E + 00
16th page
K = 0.00000E + 00, A4 = 8.21295E-05, A6 = -1.49070E-05, A8 = 1.34122E-06
A10 = 0.00000E + 00
18th page
K = 0.00000E + 00, A4 = 8.39781E-05, A6 = -2.02414E-06, A8 = -2.87245E-07
A10 = 0.00000E + 00
19th page
K = 0.00000E + 00, A4 = 4.71514E-04, A6 = -1.90431E-05, A8 = 0.00000E + 00
A10 = 0.00000E + 00

Table 3 (various data)

Zoom ratio 4.36001
Wide angle Medium telephoto Focal length 5.0600 10.9698 22.0617
F number 3.42032 5.37244 6.09970
Angle of View 41.0733 19.4013 9.6628
Image height 3.8300 3.8300 3.8300
Total lens length 54.8694 54.8725 54.8989
BF 0.36937 0.37248 0.39889
d7 16.8199 8.0052 0.9000
d15 3.8000 5.5758 13.1619
d17 2.8093 9.8482 9.3673

Zoom lens group data Group Start surface Focal length
1 1 -8.20945
2 8 10.00098
3 16 -9.44873
4 18 12.94317

(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 20.29870 0.70000 1.80470 41.0
2 * 9.12120 2.30360
3 ∞ 8.76000 1.84666 23.8
4 ∞ 1.55580
5 -9.88260 0.40000 1.72916 54.7
6 18.44150 1.32940 1.84666 23.8
7 -61.66310 Variable
8 (Aperture) ∞ -0.20000
9 * 8.05600 2.39450 1.51443 63.3
10 -55.46670 0.30000
11 9.52760 2.55560 1.49700 81.6
12 -15.06270 0.40000 1.80610 33.3
13 14.77460 0.54890
14 * 18.21700 1.79420 1.51443 63.3
15 -13.27360 Variable
16 * -24.99250 0.70000 1.60602 57.4
17 6.02440 Variable
18 * 12.16420 2.78040 1.60602 57.4
19 * -23.38690 3.00000
20 ∞ 0.90000 1.51680 64.2
21 ∞ (BF)
Image plane ∞

Table 5 (Aspheric data)

Second side
K = 0.00000E + 00, A4 = -4.14435E-05, A6 = -1.42629E-06, A8 = 8.46111E-08
A10 = -1.65884E-09
9th page
K = -5.37131E-01, A4 = 1.10009E-04, A6 = -7.66573E-07, A8 = 1.26355E-07
A10 = -4.74800E-10
14th page
K = 0.00000E + 00, A4 = -9.53499E-04, A6 = -2.03088E-06, A8 = -5.12543E-07
A10 = 0.00000E + 00
16th page
K = 0.00000E + 00, A4 = 2.24120E-04, A6 = -2.16424E-05, A8 = 2.46375E-06
A10 = 0.00000E + 00
18th page
K = 0.00000E + 00, A4 = 3.24834E-04, A6 = 5.65419E-06, A8 = -4.96504E-08
A10 = 0.00000E + 00
19th page
K = 0.00000E + 00, A4 = 5.49934E-04, A6 = -3.71238E-06, A8 = 0.00000E + 00
A10 = 0.00000E + 00

Table 6 (various data)

Zoom ratio 4.49999
Wide angle Medium telephoto Focal length 6.1719 10.9699 27.7733
F number 3.41944 4.76199 6.09949
Angle of view 35.3519 19.9384 7.8018
Image height 3.8300 3.8300 3.8300
Total lens length 54.8801 54.8866 54.8404
BF 0.38005 0.38658 0.34042
d7 16.3236 9.9741 0.9000
d15 3.8000 5.0398 14.8262
d17 4.1540 9.2637 8.5514

Zoom lens group data Group Start surface Focal length
1 1 -8.34735
2 8 9.45624
3 16 -7.94247
4 18 13.60585

(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 1001.79760 0.70000 1.80470 41.0
2 * 9.25290 2.32000
3 ∞ 8.76000 1.84666 23.8
4 ∞ 2.71790
5 -6.08970 0.40000 1.72916 54.7
6 -18.90120 1.40010 1.84666 23.8
7 -9.07790 Variable
8 (Aperture) ∞ -0.20000
9 * 6.77300 3.18120 1.51443 63.3
10 -39.17620 0.74890
11 25.31540 2.27680 1.49700 81.6
12 -7.14450 0.40000 1.80610 33.3
13 24.66600 0.36590
14 * 25.89720 2.16020 1.51443 63.3
15 -10.29080 Variable
16 * -21.97800 0.70000 1.60602 57.4
17 11.59350 Variable
18 * 26.58070 2.51440 1.60602 57.4
19 * -12.51780 3.00000
20 ∞ 0.90000 1.51680 64.2
21 ∞ (BF)
Image plane ∞

Table 8 (Aspherical data)

Second side
K = 0.00000E + 00, A4 = -2.01792E-04, A6 = -4.37333E-06, A8 = 1.66380E-08
A10 = -5.75782E-10
9th page
K = -5.49906E-01, A4 = 1.24190E-04, A6 = 1.47047E-06, A8 = -9.51055E-09
A10 = 6.33967E-09
14th page
K = 0.00000E + 00, A4 = -8.48846E-04, A6 = -2.27336E-06, A8 = -5.96615E-07
A10 = 0.00000E + 00
16th page
K = 0.00000E + 00, A4 = -1.72324E-04, A6 = -2.88270E-05, A8 = 1.58378E-06
A10 = 0.00000E + 00
18th page
K = 0.00000E + 00, A4 = -4.38292E-05, A6 = 1.49332E-05, A8 = 1.80473E-07
A10 = 0.00000E + 00
19th page
K = 0.00000E + 00, A4 = 1.67595E-04, A6 = 2.25549E-05, A8 = 0.00000E + 00
A10 = 0.00000E + 00

Table 9 (various data)

Zoom ratio 4.04998
Wide angle Medium telephoto Focal length 4.3500 7.4474 17.6174
F number 3.42015 4.79568 6.09994
Angle of View 42.9474 26.2633 11.3236
Image height 3.6000 3.6000 3.6000
Total lens length 56.8964 56.8410 56.8992
BF 0.39644 0.34098 0.39923
d7 17.7546 11.1758 0.9000
d15 3.8000 3.7257 8.9165
d17 2.6000 9.2531 14.3381

Zoom lens group data Group Start surface Focal length
1 1 -8.49995
2 8 10.91766
3 16 -12.42629
4 18 14.39184

(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 * 32.16900 0.50000 1.85976 40.6
2 * 8.84280 2.40000
3 ∞ 8.20000 1.90366 31.3
4 ∞ 1.65900
5 -8.81320 0.40000 1.72916 54.7
6 46.52790 1.38800 1.84666 23.8
7 -19.52110 Variable
8 (Aperture) ∞ -0.20000
9 * 7.44880 3.63340 1.51443 63.3
10 -27.36940 0.35780
11 11.74260 2.11680 1.49700 81.6
12 -13.21450 0.40000 1.80610 33.3
13 11.19570 0.42130
14 * 12.64190 1.79540 1.51443 63.3
15 -15.80390 Variable
16 * -22.33870 1.00000 1.60602 57.4
17 6.88070 Variable
18 * 11.22100 3.27260 1.60602 57.4
19 * -17.08940 3.00000
20 ∞ 0.90000 1.51680 64.2
21 ∞ (BF)
Image plane ∞

Table 11 (Aspheric data)

First side
K = 0.00000E + 00, A4 = -1.01669E-04, A6 = 6.67457E-06, A8 = -5.20404E-08
A10 = 0.00000E + 00
Second side
K = 0.00000E + 00, A4 = -2.01288E-04, A6 = 4.19898E-06, A8 = 1.75627E-07
A10 = -2.12548E-09
9th page
K = 4.31402E-01, A4 = -2.47963E-04, A6 = -8.89222E-06, A8 = 2.13615E-07
A10 = -9.80776E-09
14th page
K = 0.00000E + 00, A4 = -7.68546E-04, A6 = -2.35540E-06, A8 = -4.09337E-07
A10 = 0.00000E + 00
16th page
K = 0.00000E + 00, A4 = 1.09701E-04, A6 = 1.20136E-05, A8 = -1.27262E-06
A10 = 0.00000E + 00
18th page
K = 0.00000E + 00, A4 = 2.30030E-04, A6 = 7.28810E-07, A8 = -2.88100E-07
A10 = 0.00000E + 00
19th page
K = 0.00000E + 00, A4 = 7.77861E-04, A6 = -2.13214E-05, A8 = 0.00000E + 00
A10 = 0.00000E + 00

Table 12 (various data)

Zoom ratio 4.35970
Wide angle Medium telephoto Focal length 5.0600 10.9688 22.0602
F number 3.42015 5.33715 6.09987
Angle of View 40.1023 19.5124 9.6954
Image height 3.7300 3.8300 3.8300
Total lens length 54.8782 54.8645 54.8790
BF 0.37823 0.36451 0.37897
d7 17.0557 8.0561 0.9000
d15 3.6000 5.5359 12.7897
d17 2.6000 9.6637 9.5660

Zoom lens group data Group Start surface Focal length
1 1 -8.37748
2 8 10.04190
3 16 -8.56958
4 18 11.68678

  Table 13 below shows the corresponding values for each condition in the zoom lens system of each numerical example.

Table 13 (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 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 Example 3 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 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 4 Schematic configuration diagram of a digital still camera according to Embodiment 5

Explanation of symbols

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group L1 First lens element L2 Second lens element (prism)
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 Image sensor 3 LCD monitor 4 Case

Claims (7)

A zoom lens system having a plurality of lens groups each including at least one lens element, and performing zooming by changing an interval between the lens groups,
In order from the object side to the image side, a first lens group having negative power, a second lens group having positive power, a third lens group having negative power, and a fourth lens having positive power A group of
During zooming from the wide-angle end to the telephoto end during imaging , the air gap between the first lens group and the second lens group, the air gap between the second lens group and the third lens group, and the first Zooming is performed by moving the lens group along the optical axis so that the air gap between the third lens group and the fourth lens group changes,
The first lens group includes a lens element having a reflecting surface for bending a light beam from an object;
A zoom lens system that satisfies the following condition (1):
0.20 <| f _G1 | / f _T ≦ 0.380 (1)
(However, f _T / f _W ≧ 4.0)
here,
f _G1 : composite focal length of the first lens group,
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 first lens unit does not move along the optical axis during zooming from the wide-angle end to the telephoto end during imaging.   The zoom lens system according to claim 1, wherein each of the first lens group, the second lens group, and the third lens group includes at least one lens element having an aspheric surface.   The zoom lens system according to claim 1, wherein the aperture stop is disposed between the first lens group and the second lens group. The zoom lens system according to claim 1, satisfying the following condition (2):
0.20 <f _G2 / f _T <0.62 (2)
(However, f _T / f _W ≧ 4.0)
here,
f _G2 : composite focal length of the second lens group,
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. 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
A zoom lens system having a plurality of lens groups each including at least one lens element and performing zooming by changing an interval between the lens groups;
In order from the object side to the image side, a first lens group having negative power, a second lens group having positive power, a third lens group having negative power, and a fourth lens having positive power A group of
During zooming from the wide-angle end to the telephoto end during imaging , the air gap between the first lens group and the second lens group, the air gap between the second lens group and the third lens group, and the first Zooming is performed by moving the lens group along the optical axis so that the air gap between the third lens group and the fourth lens group changes,
The first lens group includes a lens element having a reflecting surface for bending a light beam from an object;
The following conditions (1):
0.20 <| f _G1 | / f _T ≦ 0.380 (1)
(However, f _T / f _W ≧ 4.0)
(here,
f _G1 : composite focal length of the first lens group,
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 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
A zoom lens system having a plurality of lens groups each including at least one lens element and performing zooming by changing an interval between the lens groups;
In order from the object side to the image side, a first lens group having negative power, a second lens group having positive power, a third lens group having negative power, and a fourth lens having positive power A group of
During zooming from the wide-angle end to the telephoto end during imaging , the air gap between the first lens group and the second lens group, the air gap between the second lens group and the third lens group, and the first Zooming is performed by moving the lens group along the optical axis so that the air gap between the third lens group and the fourth lens group changes,
The first lens group includes a lens element having a reflecting surface for bending a light beam from an object;
The following conditions (1):
0.20 <| f _G1 | / f _T ≦ 0.380 (1)
(However, f _T / f _W ≧ 4.0)
(here,
f _G1 : composite focal length of the first lens group,
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