JP4518472B2 - Zoom lens, lens unit, camera, and portable information terminal device - Google Patents

Description

  The present invention relates to a zoom lens that can be selectively set to a desired focal length within a predetermined focal length range, and achieves a wide angle of view and a high zoom ratio at the wide-angle end in addition to downsizing and high performance. A zoom lens suitable for a camera using electronic imaging means, such as a digital camera and a video camera, and a lens using such a zoom lens, although it can be used for a silver salt camera using a silver salt film. The present invention relates to a unit, a camera, and a portable information terminal device.

It is called a digital camera or an electronic camera, and a subject image is picked up by a solid-state image pickup device such as a CCD (charge coupled device) image pickup device, and image data of a still image (still image) or a moving image (movie image) of the subject. The type of camera that digitally records in a non-volatile semiconductor memory such as a flash memory has already been generalized, and is a conventional camera using a conventional silver salt film, that is, a silver salt camera. Replacement is progressing rapidly.
The market for such digital cameras has become very large, and user demands for digital cameras have also varied. Among them, high image quality and miniaturization are always desired by users and occupy a large weight. For this reason, zoom lenses used as photographic lenses are also required to have both high performance and small size.
In terms of miniaturization, it is necessary to shorten the total lens length in use, that is, the distance from the lens surface closest to the object side to the image plane, and reduce the thickness of each lens group for storage. It is also important to reduce the overall length of the hour. Furthermore, in terms of high performance, it is necessary to have a resolving power corresponding to an image sensor having at least about 3 to 5 million pixels or more over the entire zoom range.

In addition, there are many users who desire a wide angle of view of the photographing lens, and it is desirable that the half angle of view at the wide angle end of the zoom lens is 38 degrees or more. A half angle of view of 38 degrees corresponds to a focal length of 28 mm in terms of a 35 mm silver salt camera using a 35 mm (so-called Leica) silver salt film.
Further, a zoom magnification ratio as large as possible is desired. A zoom lens equivalent to 28 to 135 mm with a focal length equivalent to a 35 mm silver-salt camera is considered to be able to handle most of general photographing, and the zoom ratio of such a zoom lens is about 4 .8 times. Therefore, a zoom ratio equivalent to or higher than that is also desired for digital cameras.
Many types of zoom lenses for digital cameras are conceivable, but those having five or more lens groups are difficult to reduce the total thickness of all lens systems and are not suitable for miniaturization. . As the most common type of a zoom lens of about 3 times, a first lens group having a negative focal length, that is, negative refractive power, and a positive focal length, that is, positive refraction, in order from the object side. A second lens group having a power and a third lens group having a positive refractive power, and a diaphragm that moves integrally with the second lens group on the object side of the second lens group The second lens group monotonously moves from the image side to the object side as the magnification changes from the short focal end to the long focal end, and the first lens group changes the position of the image plane associated with the magnification change. Some move to compensate for variations. However, the zoom lens having such a configuration is not suitable for a high zoom ratio exceeding 4 times.

  For example, Patent Document 1 discloses, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, and a third lens having a positive refractive power. A lens group and a fourth lens group having a positive refractive power are disposed, and the first lens group and the third lens group monotonously toward the object side as the magnification is changed from the wide-angle end to the telephoto end. A zoom lens is disclosed that moves, the second lens group holds a fixed position, and the fourth lens group moves appropriately. For example, in Patent Document 2, the first lens group and the third lens group monotonously move toward the object side with zooming from the wide-angle end to the telephoto end, and the second lens group is an image. There is disclosed a zoom lens of a type that moves monotonously to the side and in which the fourth lens group moves appropriately. For example, in Patent Document 3, the first lens group holds a fixed position, and the second lens group moves monotonously to the image side with zooming from the wide-angle end to the telephoto end. A zoom lens in which the third lens group moves toward the object side is disclosed.

  That is, as a zoom lens well known as a type suitable for high zooming, a first lens group having a positive refractive power (focal length) and a second lens having a negative refractive power in order from the object side. A lens group, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power are disposed, and an aperture stop is provided in the vicinity of the third lens group. Along with zooming to the end, the first lens group and the third lens group hold a fixed position, the second lens group monotonously moves from the object side to the image side, and the fourth lens group Are moved so as to correct fluctuations in the image plane position due to zooming, and are disclosed in, for example, Patent Document 4 and Patent Document 5. This type of zoom lens is used in many video cameras and some digital cameras because there are only two moving lens groups and the structure of the lens barrel can be simplified. However, in this type of zoom lens, since it is necessary to ensure a large amount of movement of the second lens group that bears most of the zooming action, a stop disposed in the vicinity of the third lens group is not limited to the first lens group. If the lens is always arranged away from one lens group and attempts to widen the angle, the first lens group becomes very large.

Therefore, the second lens group and the third lens group are moved in opposite directions with the aperture stop interposed therebetween, and the third lens group is also subjected to a zooming action, thereby moving the second lens group. In order to reduce the diameter of the first lens group, there have been proposed ones in which the diameter of the first lens group is reduced. However, even in this type of zoom lens, the first lens group maintains a fixed position, and thereby the overall length of the lens becomes substantially constant. Therefore, when attempting to widen the half angle of view at the wide angle end to 38 degrees or more, Since the first lens group is also increased in size, it is difficult to widen the half angle of view at the wide angle end to 38 degrees or more. As described above, the half angle of view at the wide angle end is 38 degrees or more. In order to widen the angle, the zoom type in which the position of the first lens group is fixed is impossible, and the type in which the first lens group moves is desirable. By shortening the total lens length at the wide-angle end as compared with the telephoto end, it is possible to sufficiently widen the angle while suppressing an increase in the size of the first lens group.

  Such a zoom type, that is, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side. And a fourth lens group having a positive refractive power, and a zoom lens in which the first lens group monotonously moves toward the object side upon zooming from the wide-angle end to the telephoto end is, for example, a patent There are those disclosed in Document 1 and Patent Document 2. However, the zoom lenses disclosed in Patent Document 1 and Patent Document 2 have a half angle of view of about 25 to 32 degrees at the wide angle end, and are still insufficient in terms of widening the angle.

JP-A-11-174330 JP-A-4-296809 (Patent No. 3008380) JP 2001-56436 A JP-A-62-24213 JP-A-3-33710 JP-A-6-94997

The present invention has been made in view of the above circumstances, and includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. The fourth lens group having positive refractive power is sequentially arranged from the object side, and the first lens group and the third lens group are accompanied by zooming from the wide-angle end to the telephoto end. In a zoom lens in which the lens moves monotonously toward the object side, it is possible to sufficiently cover a normal shooting area while ensuring a sufficient wide field angle (for example, a half field angle of 38 degrees or more) at the wide angle end. Zoom lens having a magnification ratio (for example, 4.5 times or more) and having a small size and high resolution (for example, 3 to 5 million pixels), and a lens unit, a camera, and portable information using such a zoom lens To provide terminal equipment It is the target.
The object of claim 1 of the present invention is to obtain a sufficiently wide angle of view, in particular, that the half angle of view at the wide angle end is 38 degrees or more, has a zoom ratio of 4.5 times or more, and is further miniaturized . An object of the present invention is to provide a zoom lens which is suitable, particularly suitable for reducing the diameter and having a resolving power corresponding to an image sensor having 3 to 5 million pixels or more.
An object of claim 2 of the present invention is to provide a zoom lens capable of obtaining high performance by correcting each aberration better.

A third object of the present invention is to provide a zoom lens that can correct each aberration more satisfactorily and obtain high performance.
A fourth object of the present invention is to provide a zoom lens that can correct each aberration more satisfactorily and obtain high performance.
The purpose of claim 5 of the present invention, in particular, the aberrations further excellently corrected, it is to provide a zoom lens that makes it possible to obtain high performance.
The object of claim 6 of the present invention is to obtain a sufficiently wide angle of view, particularly, a half angle of view at the wide angle end of 38 degrees or more, a zoom ratio of 4.5 times or more, a small size and 300 An object of the present invention is to provide a zoom lens having another configuration that can have a resolving power corresponding to an image sensor with 10,000 to 5,000,000 pixels or more.
An object of claim 7 of the present invention is to provide a zoom lens which is suitable for further miniaturization and particularly suitable for reduction in diameter.

An object of claim 8 of the present invention is to provide a zoom lens capable of obtaining a high performance by correcting chromatic aberration more satisfactorily.
An object of claim 9 of the present invention is to provide a zoom lens that can correct chromatic aberration more satisfactorily and obtain high performance.
The object of the tenth aspect of the present invention is to obtain a sufficient wide angle of view, in particular, a half angle of view at the wide angle end of 38 degrees or more, a zoom ratio of 4.5 times or more, a small size and 300 It is an object of the present invention to provide a lens unit capable of obtaining high performance using a zoom lens having another configuration that can have a resolving power corresponding to an image sensor with 10,000 to 5,000,000 pixels or more.
The object of the eleventh aspect of the present invention is to obtain a sufficient wide angle of view, in particular, a half angle of view at the wide angle end of 38 degrees or more, a zoom ratio of 4.5 times or more, a small size and 300 It is an object of the present invention to provide a camera that is small in size and can obtain high image quality with high resolving power by using a zoom lens that can have resolving power corresponding to an image sensor with 10,000 to 5,000,000 pixels or more.
The purpose of claim 12 of the present invention, in particular, with the half angle of the wide-angle end to obtain a wide enough angle of view 38 degrees or more, has a 4.5 times higher zoom ratio, moreover and a small 300 It is an object of the present invention to provide a portable information terminal device that is small in size and can obtain high image quality with high resolution by using a zoom lens that can have a resolution corresponding to an image sensor with 10,000 to 5,000,000 pixels or more.

In order to achieve the above object, a zoom lens according to the present invention described in claim 1 is provided.
In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a positive refractive power. Zoom lens in which the first lens group and the third lens group move monotonously toward the object side in response to zooming from the wide-angle end to the telephoto end. In
During zooming from the wide-angle end to the telephoto end, the second lens group holds its position fixedly, and the fourth lens group moves at the telephoto end so that it is positioned closer to the image side than the wide-angle end.
The imaging magnification of the fourth lens group at the telephoto end is m4T , the total movement amount of the first lens group accompanying the zooming from the wide-angle end to the telephoto end is X1, and the focal length of the entire system at the telephoto end is fT.
Conditional expression:
0.65 <m4T <0.80
0.60 <X1 / fT <0.75
It is characterized by satisfying.

The zoom lens according to the present invention described in claim 2 is the zoom lens according to claim 1,
The imaging magnification of the fourth lens group at the telephoto end is m4T, and the imaging magnification of the fourth lens group at the wide angle end is m4W.
Conditional expression:
1.0 <m4T / m4W <1.3
It is characterized by satisfying .

The zoom lens according to a third aspect of the present invention is the zoom lens according to the first or second aspect ,
X3 is the total amount of movement of the third lens unit during zooming from the wide-angle end to the telephoto end, and fT is the focal length of the entire system at the telephoto end.
Conditional expression:
0.25 <X3 / fT <0.50
It is characterized by satisfying.
A zoom lens according to a fourth aspect of the present invention is the zoom lens according to any one of the first to third aspects,
The focal length of the second lens group is f2, and the focal length of the third lens group is f3.
Conditional expression:
0.6 <| f2 | / f3 <1.0
It is characterized by satisfying.

A zoom lens according to a fifth aspect of the present invention is the zoom lens according to any one of the first to fourth aspects,
The focal length of the first lens group is f1, and the focal length of the entire system at the wide angle end is fW.
Conditional expression:
6.0 <f1 / fW <12.0
It is characterized by satisfying.
In order to achieve the above-described object, a zoom lens according to the present invention described in claim 6 is provided.
In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a positive refractive power. Zoom lens in which the first lens group and the third lens group move monotonously toward the object side in response to zooming from the wide-angle end to the telephoto end. In
During zooming from the wide-angle end to the telephoto end, the second lens group holds its position fixedly, and the fourth lens group moves at the telephoto end so that it is positioned closer to the image side than the wide-angle end.
Assuming that the total movement amount of the first lens group accompanying the zooming from the wide angle end to the telephoto end is X1, the focal length of the entire system at the telephoto end is fT,
Conditional expression:
0. 60 <X1 / fT <0. 75
It is characterized by satisfying.

A zoom lens according to the present invention described in claim 7 is the zoom lens according to any one of claims 1 to 6 ,
The aperture stop moves independently of adjacent lens groups, and the distance between the aperture stop and the third lens group is the widest at the wide angle end and the narrowest at the telephoto end.
The zoom lens according to the present invention described in claim 8 is the zoom lens according to any one of claims 1 to 7 ,
The second lens group includes, from the object side, a negative lens having a large curvature surface facing the image side, a positive lens having a large curvature surface facing the image side, and a large curvature surface facing the object side. The negative lens is characterized by comprising three lenses arranged in sequence.
A zoom lens according to the present invention described in claim 9 is the zoom lens according to claim 8 ,
The refractive index of the i-th lens counted from the object side in the second lens group is N2i, and the Abbe number of the i-th lens counted from the object side in the second lens group is ν2i.
Conditional expression:
1.75 <N21 <1.90, 35 <ν21 <50
1.65 <N22 <1.90, 20 <ν22 <35
1.75 <N23 <1.90, 35 <ν23 <50
It is characterized by satisfying.

The lens unit according to the present invention described in claim 10 is:
An optical system including the zoom lens according to any one of claims 1 to 9 ,
And a mechanism for supporting each optical element constituting the optical system and moving each optical element at least for each lens group.
A camera according to the present invention described in claim 11 is provided.
The zoom lens according to any one of claims 1 to 9 is included as a photographing optical system.
The portable information terminal device according to the present invention described in claim 12 is
The zoom lens according to any one of claims 1 to 9 is included as an imaging optical system of the camera function unit.

According to the present invention, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a positive refractive power. Are arranged in order from the object side, and the first lens group and the third lens group are directed toward the object side as the magnification is changed from the wide-angle end to the telephoto end. In a zoom lens that moves monotonically, the zoom lens has a high zoom ratio that can sufficiently cover a normal shooting area while ensuring a sufficient wide angle of view at the wide-angle end, and is small and has high resolving power In addition, a lens unit, a camera, and a portable information terminal device using such a zoom lens can be provided.
That is, according to the zoom lens of the first aspect of the present invention, from the object side, in order, the first lens group having a positive refractive power, the second lens group having a negative refractive power, an aperture stop, and a positive aperture A third lens group having refracting power and a fourth lens group having positive refracting power are arranged, and the first lens group and the third lens group are changed with zooming from the wide-angle end to the telephoto end. In a zoom lens in which the lens group moves monotonously toward the object side,
During zooming from the wide-angle end to the telephoto end, the second lens group holds its position fixedly, and the fourth lens group moves at the telephoto end so that it is positioned closer to the image side than the wide-angle end. The imaging magnification of the fourth lens group at the telephoto end is m4T , the total movement amount of the first lens group accompanying the zooming from the wide-angle end to the telephoto end is X1, and the focal length of the entire system at the telephoto end is fT.
Conditional expression:
0.65 <m4T <0.80
0.60 <X1 / fT <0.75
In particular, in a limited space, the half angle of view at the wide-angle end is 38 degrees or more and a sufficient wide angle of view is obtained, and the zoom ratio is 4.5 or more. It is possible to obtain a resolving power that is more compact and particularly suitable for reducing the diameter and corresponding to an image sensor with 3 to 5 million pixels or more.

The zoom lens according to claim 2 of the present invention is the zoom lens according to claim 1, wherein the imaging magnification of the fourth lens group at the telephoto end is m4T, and the fourth lens group at the wide-angle end is connected. When the image magnification is m4W,
Conditional expression:
1.0 <m4T / m4W <1.3
By satisfying the above, it is possible to correct each aberration more satisfactorily and obtain high performance particularly with respect to the change in the magnification of the fourth lens group due to zooming .

According to the zoom lens of claim 3 of the present invention, the zoom lens of claim 1 or claim 2, wherein the total amount of movement of the third lens group upon zooming from the wide-angle end to the telephoto end is X3, Let fT be the focal length of the entire system at the telephoto end.
Conditional expression:
0.25 <X3 / fT <0.50
By satisfying the above, it is possible to obtain a high performance by correcting each aberration more favorably with respect to the movement amount of the third lens group.
According to a zoom lens of a fourth aspect of the present invention, in the zoom lens according to any one of the first to third aspects, the focal length of the second lens group is f2, and the third lens group. Let f3 be the focal length of
Conditional expression:
0.6 <| f2 | / f3 <1.0
In particular, it is possible to correct each aberration more satisfactorily and obtain high performance.

According to the zoom lens according to claim 5 of the present invention, be any one of the zoom lens of claims 1 to 4, the focal length of the first lens group f1, the entire system at the wide angle end Let fW be the focal length of
Conditional expression:
6.0 <f1 / fW <12.0
In particular, it is possible to correct each aberration more satisfactorily and obtain high performance.

According to the zoom lens according to claim 6 of the present invention, in order from the object side, a first lens group having positive refractive power, a second lens group having a negative refractive power, an aperture stop, a positive refractive A third lens group having a power and a fourth lens group having a negative refractive power are disposed, and the first lens group and the third lens are accompanied by zooming from the wide-angle end to the telephoto end. In the zoom lens in which the group moves monotonously toward the object side, the second lens group holds its position fixedly at the time of zooming from the wide-angle end to the telephoto end, and the fourth lens group is at the telephoto end. While moving so as to be located on the image side with respect to the wide-angle end, the total movement amount of the first lens group accompanying the zooming from the wide-angle end to the telephoto end is X1, and the focal length of the entire system at the telephoto end is fT.
Conditional expression:
0. 60 <X1 / fT <0. 75
By satisfying the above, in particular, using a configuration slightly different from that of claim 1, a half angle of view at the wide angle end is 38 degrees or more, and a sufficient wide angle of view is obtained, and a zoom ratio of 4.5 times or more is obtained. In addition, it is possible to obtain a resolving power corresponding to an image sensor having a small size and 3 million to 5 million pixels or more.
According to a zoom lens of a seventh aspect of the present invention, in the zoom lens according to any one of the first to sixth aspects, the aperture stop moves independently of an adjacent lens group, The distance between the aperture stop and the third lens group is widest at the wide-angle end and narrowest at the telephoto end, so that a zoom lens suitable for further miniaturization and particularly suitable for small diameter can be obtained.

According to a zoom lens of an eighth aspect of the present invention, in the zoom lens according to any one of the first to seventh aspects, the second lens group is sequentially moved from the object side to the image side. By a configuration comprising three lenses, in which a negative lens having a large curvature surface, a positive lens having a large curvature surface on the image side, and a negative lens having a large curvature surface on the object side are sequentially arranged In particular, it becomes possible to correct chromatic aberration more satisfactorily and obtain high performance.

According to the zoom lens of claim 9 of the present invention, in the zoom lens of claim 8 , the refractive index of the i-th lens counted from the object side in the second lens group is N2i, and the second lens group. The Abbe number of the i-th lens counted from the object side is ν2i,
Conditional expression:
1.75 <N21 <1.90, 35 <ν21 <50
1.65 <N22 <1.90, 20 <ν22 <35
1.75 <N23 <1.90, 35 <ν23 <50
In particular, it is possible to correct chromatic aberration more satisfactorily and obtain high performance.
Furthermore, according to the lens unit of claim 10 of the present invention, an optical system including the zoom lens according to any one of claims 1 to 9 and each optical element constituting the optical system are provided. In particular, by providing a mechanism for supporting and moving each optical element at least for each lens group, the half angle of view at the wide angle end is 38 degrees or more and a sufficient wide angle of view is obtained, and 4.5 times It is possible to obtain high performance by using a zoom lens having another zoom ratio having the above zoom ratio and having a resolution that is compatible with an image sensor having a size of 3 to 5 million pixels or more. .

According to the camera of the eleventh aspect of the present invention, the zoom lens according to any one of the first to ninth aspects is included as the photographing optical system, and in particular, the half-angle at the wide angle end. An angle of view of 38 degrees or more provides a sufficiently wide angle of view, a zoom ratio of 4.5 or more, and a resolution that is compatible with small image sensors with 3 to 5 million pixels. By using the zoom lens to be obtained, it is possible to obtain a high quality image with a small size and high resolution.
According to the portable information terminal device of the twelfth aspect of the present invention, by including the zoom lens according to any one of the first to ninth aspects as a photographing optical system of the camera function unit, in particular, a wide angle. Resolving power corresponding to an image sensor with a zoom ratio of 4.5 times or more, a small size, and 3 to 5 million pixels or more, while obtaining a sufficient wide field angle of 38 degrees or more at the end. It is possible to obtain a high quality image with a small size and high resolution using a zoom lens that can have

Hereinafter, based on an embodiment of the present invention, a zoom lens, a lens unit, a camera, and a portable information terminal device according to the present invention will be described in detail with reference to the drawings. Before describing specific examples, first, in order to explain the principle embodiments of the present invention, configurations and functions defined in the claims of the claims will be described.
A zoom lens according to claims 1 to 9 of the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, and a third lens having a positive refractive power. And a fourth lens group having a positive refractive power, and the first lens group, the second lens group, the aperture stop, the third lens group, and the fourth lens group are sequentially arranged from the object side. The first lens group and the third lens group monotonously move toward the object side with zooming from the wide-angle end to the telephoto end, and zoom from the wide-angle end to the telephoto end. At this time, the second lens group holds its position fixedly, and the fourth lens group is a zoom lens that moves so as to be positioned closer to the image side than the wide angle end at the telephoto end. It has the following features.
In the zoom lens according to claim 1, m4T is an imaging magnification of the fourth lens group at the telephoto end, and X1 is a total movement amount of the first lens group accompanying the zooming from the wide angle end to the telephoto end . When fT is the focal length of the entire system at the telephoto end , the following conditional expression is satisfied.
0.65 <m4T <0.80
0.60 <X1 / fT <0.75

The zoom lens according to a second aspect satisfies the following conditional expression in the zoom lens according to the first aspect, when m4W is an imaging magnification of the fourth lens group at the wide angle end.
1.0 <m4T / m4W <1. 3
The zoom lens according to 請 Motomeko 3, first in claims 1 or claim 2 zoom lens, the focal length of the entire system at the telephoto end of fT, further when the X3 in zooming from the wide-angle end to the telephoto end When the total movement amount of the three lens groups is satisfied, the following conditional expression is satisfied.
0.25 <X3 / fT <0.50
The zoom lens according to claim 4 is the zoom lens according to any one of claims 1 to 3 , wherein f2 is a focal length of the second lens group and f3 is a focal length of the third lens group. The following conditional expression is satisfied.
0.6 <| f2 | / f3 <1.0

The zoom lens according to claim 5 is the zoom lens according to any one of claims 1 to 4 , wherein f1 is a focal length of the first lens group and fW is a focal length of the entire system at the wide angle end. Satisfies the following conditional expression.
6.0 <f1 / fW <12.0
In the zoom lens according to claim 6 , when X1 is a total moving amount of the first lens unit accompanying zooming from the wide-angle end to the telephoto end, and fT is a focal length of the entire system at the telephoto end, the following conditional expression Satisfied.
0. 60 <X1 / fT <0. 75

The zoom lens according to a seventh aspect is the zoom lens according to any one of the first to sixth aspects, wherein the aperture stop moves independently of an adjacent lens group, and the aperture stop and the third lens The distance from the lens group is widest at the wide angle end and narrowest at the telephoto end.
A zoom lens according to an eighth aspect of the present invention is the zoom lens according to any one of the first to seventh aspects, wherein the second lens group is a negative lens having a surface with a large curvature facing the image side sequentially from the object side. The lens is composed of three lenses: a positive lens having a large curvature surface on the image side, and a negative lens having a large curvature surface on the object side.

Zoom lens according to claim 9, in the zoom lens according to claim 8, and the refractive index of the i th lens counted from the object side N2i in the second group, counted from the object side ν2i in the second group When the Abbe number of the i-th lens is used, the following conditional expression is satisfied.
1.75 <N21 <1.90, 35 <ν21 <50
1.65 <N22 <1.90, 20 <ν22 <35
1.75 <N23 <1.90, 35 <ν23 <50
A lens unit according to a tenth aspect of the present invention supports the optical system including the zoom lens according to any one of the first to ninth aspects, and each optical element constituting the optical system, and the optical element. And a mechanism for moving at least each lens group.
A camera according to an eleventh aspect of the present invention includes the zoom lens according to any one of the first to ninth aspects as a photographing optical system.

A portable information terminal device according to a twelfth aspect of the present invention includes the zoom lens according to any one of the first to ninth aspects as a photographing optical system of a camera function unit.
Next, the embodiments defined in the claims of the above-described claims of the present invention will be described in more detail.
The zoom lens according to the present invention has a positive-negative-positive-positive four-group configuration, that is, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. A third lens group having a positive refractive power and a fourth lens group having a positive refractive power are sequentially disposed from the object side, and an aperture stop is disposed between the second lens group and the third lens group. Is done. A zoom lens composed of four positive-negative-positive-positive lens groups as described above is generally configured as a so-called variator in which the second lens group bears a main zooming action. However, in the zoom lens according to the present invention, the third lens unit also shares the zooming action, reduces the burden on the second lens unit, and corrects aberrations that become difficult with widening and high zooming. A degree of freedom is secured. Further, when zooming from the wide-angle end to the telephoto end, the height of the light beam (distance from the optical axis) passing through the first lens group at the wide-angle end is greatly moved by moving the first lens unit toward the object side. The distance between the first lens group and the second lens group is kept large at the telephoto end to achieve a long focal length while suppressing the enlargement of the first lens group accompanying the wide angle.

Furthermore, in the zoom lens according to the present invention, consideration is given to simplifying the lens barrel configuration and ensuring the accuracy of decentration between groups by holding the second lens group at a fixed position during zooming. Of course, if aberration correction is prioritized, it is advantageous to move all the lens groups. However, if this is done, the structure of the lens barrel becomes complicated and manufacturing errors are likely to occur. It is a major premise of the present invention that the second lens group is fixed during zooming.
During zooming from the wide-angle end to the telephoto end, the first lens group and the third lens group move monotonously toward the object side, the distance between the first lens group and the second lens group increases, and the second lens and the third lens group increase. The distance from the lens group is reduced, the magnifications of the second lens group and the third lens group are both increased, and the zooming action is shared with each other.
The fourth lens group is moved so that it is positioned closer to the image side than the wide-angle end at the telephoto end. Due to such movement, the magnification of the fourth lens unit also increases in zooming from the wide-angle end to the telephoto end, and the zooming action can be borne. Therefore, the zoom lens is effectively changed in a limited space. Can be doubled.

In addition, by satisfying the following condition, in terms of achieving a wide-angle and a high zoom ratio which is aimed, that Do is possible to sufficiently correct aberrations.
0.65 <m4T <0.80
However, m4T represents the imaging magnification of the fourth lens group at the telephoto end.
In this case, if m4T is set to 0.65 or less, the light beam emitted from the third lens group approaches afocal, and the third lens group cannot effectively contribute to zooming. As a result, the variable magnification burden of the second lens group increases, and it becomes difficult to correct field curvature and astigmatism that increase with a wide angle. On the other hand, if m4T is 0.80 or more, the fourth lens group will be too close to the image plane and the required back focus cannot be secured, or the refractive power of the fourth lens group will be too small. If the refractive power of the fourth lens group becomes too small, the exit pupil moves closer to the image plane, the light incident angle on the periphery of the light receiving element increases, and it becomes easy to cause a shortage of light in the periphery.

It is more desirable that the following conditional expression is satisfied.
0.65 <m4T <0.80
Further, with respect to the magnification change in the fourth lens group upon zooming from the wide-angle end to the telephoto end, it has to desirable to satisfy the following condition.
1.0 <m4T / m4W <1.3
However, m4W represents the imaging magnification of the fourth lens group at the wide angle end.
In this case, if (m4T / m4W) is 1.0 or less, the fourth lens group does not contribute to zooming, and the zooming burden of the second lens group and the third lens group is increased, so It becomes difficult to balance the image plane. On the other hand, if (m4T / m4W) is set to 1.3 or more, the variable magnification burden of the fourth lens group becomes too large, and the aberration is corrected if the fourth lens group remains a simple configuration, for example, one positive lens. It becomes difficult.

It is more desirable that the following conditional expression is satisfied.
1.05 <m4T / m4W <1.2
In the present invention, the second lens group is held at a fixed position during zooming, and the distance between the first lens group and the second lens group is determined only by the amount of movement of the first lens group. In this regard, it was desired to satisfy the following condition.
0.50 <X1 / fT <0.85
Here, X1 represents the total amount of movement of the first lens group upon zooming from the wide-angle end to the telephoto end, and fT represents the focal length of the entire system at the telephoto end.

In this case, if (X1 / fT) is 0.50 or less, the contribution of the second lens group to the zooming is reduced and the burden on the third lens group is increased, or the first lens group / second lens group is increased. However, in any case, various aberrations will be deteriorated. Further, the total lens length at the wide-angle end is increased, and the height of the light beam passing through the first lens group is increased, leading to an increase in size of the first lens group. On the other hand, if (X1 / fT) is 0.85 or more, the total length at the wide-angle end will be too short, or the total length at the telephoto end will be too long. If the total length at the wide-angle end becomes too short, the moving space of the third lens group is limited, the contribution of the third lens group to zooming becomes small, and it becomes difficult to correct the entire aberration. If the total length at the telephoto end becomes too long, it will not only hinder downsizing in the full-length direction, but the radial direction will be enlarged to secure the amount of peripheral light at the telephoto end, and the lens barrel will be tilted. Degradation of image performance due to errors is also likely to occur.
It is more desirable that the following conditional expression is satisfied.
0.60 <X1 / fT <0.75
Just as the distance between the first lens group and the second lens group is determined only by the movement amount of the first lens group, the distance between the second lens group and the third lens group is determined only by the movement amount of the third lens group. Determined. In this regard, it was desired to satisfy the following condition.
0.25 <X3 / fT <0.50
X3 represents the total amount of movement of the third lens group upon zooming from the wide-angle end to the telephoto end.

In this case, if (X3 / fT) is 0.25 or less, the contribution of the third lens group to the zooming is reduced, and the burden on the second lens group is increased, or the refractive power of the third lens group itself is increased. In any case, various aberrations will be worsened. On the other hand, if (X3 / fT) is 0.45 or more, the total lens length at the wide-angle end becomes long, the height of the light beam passing through the first lens group increases, and the size of the first lens group increases.
It is more desirable that the following conditional expression is satisfied.
0.30 <X3 / fT <0.45
Respect aberration correction, have to desirable to further satisfy the following condition.
0.6 <| f2 | / f3 <1.0
6.0 <f1 / fW <10.0
However, f1 represents the focal length of the first lens group, f2 represents the focal length of the second lens group, f3 represents the focal length of the third lens group, and fW represents the entire system at the wide angle end. Represents the focal length.

In this case, if (| f2 | / f3) is 0.6 or less, the refractive power of the second lens group becomes too strong. If (| f2 | / f3) is 1.0 or more, the third lens group The refractive power becomes too strong, and in any case, the aberration variation at the time of zooming tends to become large.
If (f1 / fW) is 6.0 or less, the imaging magnification of the second lens unit approaches the same magnification and the zooming efficiency is improved, which is advantageous for high zooming. Each lens requires a large refractive power, which not only has adverse effects such as worsening chromatic aberrations at the telephoto end, but also the first lens group becomes thicker and larger in diameter, and is particularly compact in the retracted state. Disadvantageous. On the other hand, if (f1 / fW) is set to 12.0 or more, the contribution of the second lens group to zooming becomes small, and high zooming becomes difficult.
The above-described object of the present invention can also be achieved by the following configuration. That is, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power. The lens group is sequentially arranged from the object side, and the first lens group and the third lens group move monotonously to the object side as the magnification changes from the wide-angle end to the telephoto end. When zooming from the telephoto end to the telephoto end, the following condition is satisfied in the zoom lens in which the second lens group holds a fixed position and the fourth lens group moves at the telephoto end so as to be positioned closer to the image side than the wide-angle end. also not good as a configuration that satisfies the equation.
0. 60 <X1 / fT <0. 75
Here, X1 represents the total amount of movement of the first lens group upon zooming from the wide-angle end to the telephoto end, and fT represents the focal length of the entire system at the telephoto end.

In the zoom lens of the present invention, the aperture stop moves independently of the adjacent second lens group and third lens group, and the distance between the aperture stop and the third lens group is widest at the wide-angle end. , have to desirable narrowest at the telephoto end.
By making the distance between the aperture stop and the third lens group the widest at the wide-angle end, the aperture stop can be brought closer to the first lens group at the wide-angle end, and the height of the light beam passing through the first lens group can be made lower. As a result, further downsizing of the first lens group can be achieved.
Next, conditions for performing better aberration correction within a range that does not hinder downsizing are examined.
The second lens group includes, from the object side, a negative lens having a large curvature surface facing the image side, a positive lens having a large curvature surface facing the image side, and a large curvature surface facing the object side. negative lens and a not to want to become a three lenses.

As a variable power group having a negative refractive power, in the case where it is composed of three lenses, an arrangement of negative lens-negative lens-positive lens in order from the object side is well known. Compared to the configuration, the above-described configuration is excellent in the ability to correct lateral chromatic aberration associated with widening the angle. Here, the second lens and the third lens from the object side of the second lens group may be appropriately joined.
In this case, each lens of the second lens group, not to desired to satisfy the following condition.
1.75 <N21 <1.90, 35 <ν21 <50
1.65 <N22 <1.90, 20 <ν22 <35
1.75 <N23 <1.90, 35 <ν23 <50
N2i represents the refractive index of the i-th lens counted from the object side in the second lens group, and ν2i represents the Abbe number of the i-th lens counted from the object side in the second lens group.
By selecting such a glass type, it is possible to correct chromatic aberration better.

  The first lens group preferably has a configuration in which at least one negative lens and at least one positive lens are sequentially arranged from the object side. More specifically, from the object side, the lens is composed of two lenses in which a negative meniscus lens having a convex surface facing the object side and a positive lens having a strong convex surface facing the object side are arranged, or the object In order from the side, the lens is composed of three lenses, a negative meniscus lens having a convex surface facing the object side, a positive lens having a strong convex surface facing the object side, and a positive lens having a strong convex surface facing the object side. It is desirable to do this.

The third lens group is preferably composed of three lenses in which a positive lens, a positive lens, and a negative lens are sequentially arranged from the object side. Here, the second lens and the third lens from the object side of the third lens group may be appropriately joined.
The fourth lens group is preferably composed of one positive lens. Further, when focusing to a finite distance, the method of moving only the fourth lens group may require the smallest weight of the object to be moved. In addition, the fourth lens group has a merit that a moving amount at the time of zooming is small, and a moving mechanism for zooming can be used as a moving mechanism for focusing.
In order to further reduce the size while maintaining good aberration correction, it is indispensable to use an aspheric surface, and at least the second lens group and the third lens group should each have one or more aspheric surfaces. Is desirable. In particular, in the second lens group, if both the most object-side surface and the most image-side surface are aspherical surfaces, it is highly effective in correcting distortion and astigmatism that tend to increase as the angle of view increases. Obtainable.

As an aspheric lens, optical glass and optical plastic are molded (referred to as glass mold aspheric surface and plastic mold aspheric surface, respectively), or a thin resin layer is molded on the surface of the glass lens. An aspherical surface (referred to as a hybrid aspherical surface or a replica aspherical surface) can be used.
It may be simplified in terms of the mechanism that the aperture diameter of the aperture is constant regardless of zooming. However, by making the open diameter of the long focal end larger than that of the short focal end, the change in F number (F value) associated with zooming can be reduced. Further, when it is necessary to reduce the amount of light reaching the image plane, the aperture may be reduced, but the amount of light is reduced by inserting an ND (intermediate density) filter or the like without greatly changing the aperture diameter. This is preferable because it can prevent a decrease in resolution due to a diffraction phenomenon.

If a camera is configured using the zoom lens as described above or a lens unit using the same as a photographing optical system, a sufficient wide angle of view with a half angle of view of 38 degrees or more at the wide angle end can be obtained. Using a zoom lens that can obtain a zoom ratio of 5 times or more, is small, and has a resolving power corresponding to an image sensor with 3 million to 5 million pixels or more, it is small, excellent in portability, and high. that Do not it possible to obtain a high-quality by the resolution.
Further, if a portable information terminal device is configured using the zoom lens as described above or a lens unit using the same as a photographing optical system of the camera function unit, the half angle of view at the wide-angle end is sufficiently 38 degrees or more. Using a zoom lens that has a wide angle of view, a zoom ratio of 4.5 times or more, and is small and capable of resolving power corresponding to an image sensor with 3 to 5 million pixels or more. excellent portability, moreover possible to obtain high image quality due to high resolution and that Do.

Next, specific examples based on the above-described embodiment of the present invention will be described in detail. Example 1, Example 2, Example 3 and Example 4 described below are examples of specific configurations based on specific numerical examples of the zoom lens according to the present invention, and Example 5 is an example of Examples 1 to 1. FIG. 9 is a specific example of a camera or a portable information terminal device according to the present invention in which a lens unit having a zoom lens as shown in Example 4 is used as a photographing optical system.
In the first to fourth embodiments of the zoom lens according to the present invention, the configuration of the zoom lens and specific numerical examples thereof are shown. In Examples 1 to 4, the maximum image height is 3.70 mm.
In the first to fourth embodiments, the optical element formed of a parallel plate disposed on the image plane side of the fourth lens group includes various optical filters such as an optical low-pass filter and an infrared cut filter, and light reception by a CCD sensor or the like. An element cover glass (seal glass) is assumed, and is referred to as a filter / cover here.

The materials of the lenses are all optical glass except that optical plastic is used for the ninth lens of Example 1 and the tenth lens of Example 3 (both are the fourth lens group).
In Examples 1 to 4, both the most object-side surface and the most image-side surface of the second lens group, both surfaces of the most object-side lens of the third lens group, and the most object of the fourth lens group Each side surface is aspherical. As described above, the aspheric surfaces in Examples 1 to 4 are described as directly aspherical surfaces, like so-called molded aspherical lenses. An aspherical lens of the so-called hybrid lens type obtained by laying a resin thin film forming an aspherical surface on the lens surface of the spherical lens may be configured.
Aberrations in Examples 1 to 4 are sufficiently corrected, and can correspond to light receiving elements with 3 to 5 million pixels. It is clear from Examples 1 to 4 that by configuring the zoom lens according to the present invention, it is possible to ensure a very good image performance while achieving a sufficient size reduction.

The meanings of the symbols in Examples 1 to 4 are as follows.
f: Focal length of entire system F: F number ω: Half angle of view R: Radius of curvature D: Surface spacing N _d : Refractive index (d is lens number = 1 to 10)
ν _d : Abbe number (d is lens number = 1-10)
K: aspherical conic constant A _4: 4-order aspherical coefficients A _6: 6-order aspherical coefficients A _8: 8-order aspherical coefficients A _10: 10-order aspherical coefficients, however, non-used here The spherical surface is defined by the following equation, where C is the reciprocal of the paraxial radius of curvature (paraxial curvature) and H is the height from the optical axis.

FIG. 1 shows a configuration of an optical system of a zoom lens according to Embodiment 1 of the present invention, where (a) is a short focal end, that is, a wide angle end, (b) is an intermediate focal length, and (c) is a long focal length. The focal end, that is, the telephoto end is shown.
The zoom lens shown in FIG. 1 includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, and a ninth lens. A lens E9, an aperture FA, and a filter / cover FC are provided. In this case, the first lens E1 and the second lens E2 constitute the first lens group G1, the third lens E3 to the fifth lens E5 constitute the second lens group G2, and the sixth lens E6 to the eighth lens. The lens E8 constitutes the third lens group G3, and the ninth lens E9 alone constitutes the fourth lens group G4, and is supported by a common support frame or the like appropriate for each group, and zooming is performed. At the same time, each group operates integrally. FIG. 1 also shows the surface numbers of the optical surfaces. 1 are used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, the same reference numerals as those in FIGS. However, they are not necessarily in common with other embodiments.

In FIG. 1, each optical element constituting the optical system of the zoom lens includes, for example, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a fifth lens sequentially from the object side such as a subject. E5, stop FA, sixth lens E6, seventh lens E7, eighth lens E8, ninth lens E9 and filter / cover FC are arranged in this order, and an image is formed behind the filter / cover FC.
The first lens E1 is a negative meniscus lens that is convex on the object side, and the second lens E2 is a positive meniscus lens that is convex on the object side. The first lens group G1 configured by the first lens E1 and the second lens E2 has a positive focal length, that is, a positive refractive power as a whole. The third lens E3 is a negative meniscus lens that is convex toward the object side, has an aspheric surface on the object side, and a strong concave surface on the image side. The fourth lens E4 is a positive lens composed of a biconvex lens with a strong convex surface on the image side, and the fifth lens E5 is a negative lens composed of a biconcave lens with a strong concave surface on the object side and an aspheric surface on the image side. In other words, the fourth lens E4 and the fifth lens E5 are closely bonded and joined together to form a cemented lens.

  The second lens group G2 constituted by the third lens E3 to the fifth lens E5 has a negative focal length, that is, negative refractive power as a whole. The sixth lens E6 is a positive lens composed of a biconvex lens having both aspheric surfaces. The seventh lens E7 is a positive lens made up of a biconvex lens with a strong convex surface facing the image side, and the eighth lens E8 is a negative lens made up of a biconcave lens. The seventh lens E7 and the eighth lens E8 are closely And bonded together to form a cemented lens. The third lens group G3 constituted by the sixth lens E6 to the eighth lens E8 has a positive refractive power as a whole. The ninth lens E9 is a positive lens composed of a biconvex lens having a strong convex surface made of an aspheric surface facing the object side. Of course, the fourth lens group G4 constituted solely by the ninth lens E9 has a positive focal length.

In zooming from the short focal end, that is, the wide-angle end, to the long focal end, that is, the telephoto end, the variable interval between the groups, that is, the most image-side surface of the first lens group G1, that is, the second lens E2 The distance DA between the image side surface (surface number 4) and the most object side surface of the second lens group G2, that is, the object side surface (surface number 5) of the third lens E3, and the most distance of the second lens group G2. Distance DB between the image side surface, that is, the image side surface (surface number 9) of the fifth lens E5 and the surface of the aperture FA (surface number 10), the surface of the aperture FA (surface number 10), and the third lens The distance DC between the most object side surface of the group G3, that is, the object side surface (surface number 11) of the sixth lens E6, the most image side surface of the third lens group G3, that is, the image side of the eighth lens E8. Surface (surface number 15) and the most object-side surface of the fourth lens group G4, that is, the object-side surface of the ninth lens E9 (surface number 1) ) And the most image side surface of the fourth lens group G4, that is, the image side surface (surface number 16) of the ninth lens E9, and the object side surface (surface number 18) of the filter / cover FC. , And the first lens group G1 and the third lens group G3 move monotonously toward the object side as the magnification changes from the wide-angle end to the telephoto end. At the time of zooming to the telephoto end, the second lens group G2 holds its position fixedly, and the first lens group is arranged such that the fourth lens group G4 is positioned closer to the image side than the wide angle end at the telephoto end. G1, the third lens group G3, and the fourth lens group G4 move.
In the first embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 4.74 to 21.59, F = 3.32 to 4.98, and ω = by zooming, respectively. It varies in the range of 39.14 to 9.55. The characteristics of each optical surface are as shown in the following table.

In Table 1, the optical surfaces of the fifth surface, the ninth surface, the eleventh surface, the twelfth surface, and the sixteenth surface indicated by “* (asterisk)” in the surface number are aspheric surfaces, and each aspheric surface. The parameters in the equation (1) are as follows.
Aspherical surface: 5th surface K = 0.0,
A ₄ = 2.42400 × 10 ⁻⁴ ,
A ₆ = −2.92208 × 10 ⁻⁶ ,
A ₈ = 9.40210 × 10 ⁻⁹ ,
A ₁₀ = −4.16456 × 10 ⁻¹¹
Aspherical surface: 9th surface K = 0.0,
A ₄ = −5.16761 × 10 ⁻⁴ ,
A ₆ = 1.81605 × 10 ⁻⁶ ,
A ₈ = −1.01642 × 10 ⁻⁶ ,
A ₁₀ = −1.75699 × 10 ⁻⁸

Aspheric surface: Eleventh surface K = 0.0,
A ₄ = −1.08496 × 10 ⁻³ ,
A ₆ = −2.117192 × 10 ⁻⁵ ,
A ₈ = 5.79037 × 10 ⁻⁶ ,
A ₁₀ = −5.25493 × 10 ⁻⁷
Aspheric surface: 12th surface K = 0.0,
A ₄ = 4.885474 × 10 ⁻⁴ ,
A ₆ = −4.49460 × 10 ⁻⁵ ,
A ₈ = 8.998429 × 10 ⁻⁶ ,
A ₁₀ = −5.668154 × 10 ⁻⁷
Aspheric surface: 16th surface K = 0.0,
A ₄ = −5.44644 × 10 ⁻⁵ ,
A ₆ = 1.86063 × 10 ⁻⁵ ,
A ₈ = −9.177793 × 10 ⁻⁷ ,
A ₁₀ = 2.09899 × 10 ⁻⁸
A variable distance DA between the first lens group G1 and the second lens group G2, a variable distance DB between the second lens group G2 and the aperture FA, a variable distance DC between the aperture FA and the third lens group, The variable distance DD between the third lens group G3 and the fourth lens group G4 and the variable distance DE between the fourth lens group G4 and the optical filter FC are changed as shown in the following table with zooming. .

Further, the values relating to the conditional expressions described in the first embodiment are as follows.
Conditional expression numerical value m4T = 0.718
m4T / m4W = 1.098
X1 / fT = 0.698
X3 / fT = 0.366
| F2 | /f3=0.792
f1 / fW = 8.44
Therefore, the numerical values related to the conditional expressions described in the first embodiment are within the range of the conditional expressions.

FIG. 2 shows the configuration of an optical system of a zoom lens according to Example 2 of the present invention, where (a) is a wide angle end (short focal end), (b) is an intermediate focal length, and (c) is telephoto. The state of the end (long focal end) is shown.
The zoom lens shown in FIG. 2 includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, and a ninth lens. A lens E9, an aperture FA, and a filter / cover FC are provided. In this case, the first lens E1 and the second lens E2 constitute the first lens group G1, the third lens E3 to the fifth lens E5 constitute the second lens group G2, and the sixth lens E6 to the eighth lens. The lens E8 constitutes the third lens group G3, and the ninth lens E9 alone constitutes the fourth lens group G4, and is supported by a common support frame or the like appropriate for each group, and zooming is performed. At the same time, each group operates integrally. FIG. 2 also shows the surface numbers of the optical surfaces. 2 are used independently for each embodiment. Therefore, even if the same reference symbols as those in FIGS. 1, 3, and 4 are given, they are not necessarily different from the other embodiments. It is not a common configuration.

In FIG. 2, each optical element constituting the optical system of the zoom lens includes, for example, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a fifth lens sequentially from the object side such as a subject. E5, stop FA, sixth lens E6, seventh lens E7, eighth lens E8, ninth lens E9 and filter / cover FC are arranged in this order, and an image is formed behind the filter / cover FC.
The first lens E1 is a negative meniscus lens convexly formed on the object side, and the second lens E2 is a positive meniscus lens convexly formed on the object side. The first lens E1 and the second lens E2 are They are stuck together and joined together to form a cemented lens. The first lens group G1 configured by the cemented lens of the first lens E1 and the second lens E2 has a positive refractive power as a whole. The third lens E3 is a negative meniscus lens that is convex toward the object side, has an aspheric surface on the object side, and a strong concave surface on the image side. The fourth lens E4 is a positive lens composed of a biconvex lens with a strong convex surface on the image side, and the fifth lens E5 is a negative lens composed of a biconcave lens with a strong concave surface on the object side and an aspheric surface on the image side. In other words, the fourth lens E4 and the fifth lens E5 are closely bonded and joined together to form a cemented lens. The second lens group G2 constituted by the third lens E3 to the fifth lens E5 has a negative focal length, that is, negative refractive power as a whole. The sixth lens E6 is a positive lens composed of a biconvex lens having both aspheric surfaces.

The seventh lens E7 is a positive lens composed of a biconvex lens with a strong convex surface facing the image side, and the eighth lens E8 is a negative lens composed of a biconcave lens. The seventh lens E7 and the eighth lens E8 are closely And bonded together to form a cemented lens. The third lens group G3 constituted by the sixth lens E6 to the eighth lens E8 has a positive refractive power as a whole. The ninth lens E9 is a positive lens composed of a biconvex lens having a strong convex surface made of an aspheric surface facing the object side. Of course, the fourth lens group G4 constituted solely by the ninth lens E9 has a positive focal length.
Upon zooming from the wide-angle end (short focal end) to the telephoto end (long focal end), the variable interval between the groups, that is, the most image-side surface of the first lens group G1, that is, the image of the second lens E2. Distance DA between the second surface group (surface number 3) and the most object side surface of the second lens group G2, that is, the object side surface (surface number 4) of the third lens E3, and the most image of the second lens group G2. Side DB, that is, the distance DB between the image side surface (surface number 8) of the fifth lens E5 and the surface of the aperture FA (surface number 9), the surface of the aperture FA (surface number 9), and the third lens group The distance DC between the most object side surface of G3, that is, the object side surface (surface number 10) of the sixth lens E6, the most image side surface of the third lens group G3, that is, the image side surface of the eighth lens E8. The distance D between (surface number 14) and the most object side surface of the fourth lens group G4, that is, the object side surface (surface number 15) of the ninth lens E9. The distance DE between the most image side surface of the fourth lens group G4, that is, the image side surface (surface number 16) of the ninth lens E9, and the object side surface (surface number 17) of the filter / cover FC is The first lens group G1 and the third lens group G3 monotonously move toward the object side with zooming from the wide-angle end to the telephoto end, and change from the wide-angle end to the telephoto end. At the time of magnification, the first lens group G1 and the third lens are arranged such that the second lens group G2 holds its position fixedly, and the fourth lens group G4 is positioned closer to the image side than the wide angle end at the telephoto end. The group G3 and the fourth lens group G4 move.

  In Example 2, the focal length f, F number F, and half angle of view ω of the entire system are f = 4.74 to 21.57, F = 3.56 to 5.00, and ω = by zooming, respectively. It varies in the range of 39.15 to 9.57. The characteristics of each optical surface are as shown in the following table.

The optical surfaces of the fourth surface, the eighth surface, the tenth surface, the eleventh surface, and the fifteenth surface indicated with “*” in the surface number in Table 3 are aspherical surfaces. The parameters in the equation are as follows:
Aspherical surface: 4th surface K = 0.0,
A ₄ = 1.998102 × 10 ⁻⁴ ,
A ₆ = −3.6668 × 10 ⁻⁶ ,
A ₈ = 4.52405 × 10 ⁻⁸ ,
A ₁₀ = −2.66763 × 10 ⁻¹⁰
Aspheric surface: 8th surface K = 0.0,
A ₄ = −4.56912 × 10 ⁻⁴ ,
A ₆ = −2.343635 × 10 ⁻⁶ ,
A ₈ = −7.3048 × 10 ⁻⁷ ,
A ₁₀ = −1.13163 × 10 ⁻⁸

Aspheric surface: 10th surface K = 0.0,
A ₄ = −7.28261 × 10 ⁻⁴ ,
A ₆ = 5.77787 × 10 ⁻⁶ ,
A ₈ = 1.03208 × 10 ⁻⁶ ,
A ₁₀ = −1.81386 × 10 ⁻⁷
Aspheric surface: Eleventh surface K = 0.0,
A ₄ = 4.665357 × 10 ⁻⁴ ,
A ₆ = 1.34799 × 10 ⁻⁵ ,
A ₈ = −4.337956 × 10 ⁻⁷ ,
A ₁₀ = 6.85503 × 10 ⁻⁸
Aspheric surface: 15th surface K = 0.0,
A ₄ = −6.80550 × 10 ⁻⁵ ,
A ₆ = 1.42409 × 10 ⁻⁵ ,
A ₈ = −6.37766 × 10 ⁻⁷ ,
A ₁₀ = 1.29041 × 10 ⁻⁸
A variable distance DA between the first lens group G1 and the second lens group G2, a variable distance DB between the second lens group G2 and the aperture FA, a variable distance DC between the aperture FA and the third lens group, The variable distance DD between the third lens group G3 and the fourth lens group G4 and the variable distance DE between the fourth lens group G4 and the optical filter FC are changed as shown in the following table with zooming. .

Further, the values according to the conditional expressions described in the second embodiment are as follows.
Conditional expression numerical value m4T = 0.722
m4T / m4W = 1.117
X1 / fT = 0.672
X3 / fT = 0.396
| F2 | /f3=0.799
f1 / fW = 8.84
Therefore, the numerical values related to the conditional expressions described in the second embodiment are within the range of the conditional expressions.

FIG. 3 shows the configuration of an optical system of a zoom lens according to Example 3 of the present invention, where (a) is a wide angle end (short focal end), (b) is an intermediate focal length, and (c) is telephoto. The state of the end (long focal end) is shown.
The zoom lens shown in FIG. 3 includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, and a ninth lens. A lens E9, a tenth lens E10, an aperture FA and a filter / cover FC are provided. In this case, the first lens E1 to the third lens E3 constitute the first lens group G1, the fourth lens E4 to the sixth lens E6 constitute the second lens group G2, and the seventh lens E7 to the ninth lens. The lens E9 constitutes the third lens group G3, and the tenth lens E10 alone constitutes the fourth lens group G4. Each lens E9 is supported by a common support frame or the like appropriate for each group, and zooming is performed. At the same time, each group operates integrally. 3 are used independently for each embodiment. Therefore, even if the same reference symbols as those in FIGS. 1, 2, and 4 are given, they are not necessarily different from the other embodiments. It is not a common configuration.

In FIG. 3, each optical element constituting the optical system of the zoom lens includes, for example, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a fifth lens sequentially from the object side such as a subject. E5, sixth lens E6, aperture FA, seventh lens E7, eighth lens E8, ninth lens E9, tenth lens E10 and filter / cover FC are arranged in this order, and are connected behind the filter / cover FC. Imaged.
The first lens E1 is a negative meniscus lens that is convex on the object side, and the second lens E2 is a positive lens that is a biconvex lens with a strong convex surface on the object side. The first lens E1 and the second lens E2 Are closely bonded and bonded together to form a cemented lens. The third lens E3 is a positive meniscus lens that is convexly formed on the object side. The first lens group G1 constituted by the first lens E1 to the third lens E3 has a positive refractive power as a whole. The fourth lens E4 is a negative meniscus lens that is convex toward the object side, has an aspheric surface on the object side, and a strong concave surface on the image side. The fifth lens E5 is a positive lens composed of a plano-convex lens having a flat surface on the object side, and the sixth lens E6 is a negative meniscus lens that is convex on the image side and has an aspheric surface on the image side. The fifth lens E5 and the sixth lens E6 are closely bonded and joined together to form a cemented lens. The second lens group G2 constituted by the fourth lens E4 to the sixth lens E6 has a negative focal length, that is, negative refractive power as a whole.

  The seventh lens E7 is a positive lens composed of a biconvex lens having both aspheric surfaces. The eighth lens E8 is a positive lens made up of a biconvex lens with a strong convex surface facing the image side, and the ninth lens E9 is a negative lens made up of a biconcave lens. The eighth lens E8 and the ninth lens E9 are in close contact with each other. And bonded together to form a cemented lens. The third lens group G3 constituted by the seventh lens E7 to the ninth lens E9 has a positive refractive power as a whole. The tenth lens E10 is a positive lens made of a biconvex lens having a strong convex surface made of an aspheric surface facing the object side. Of course, the fourth lens group G4 constituted solely by the tenth lens E10 has a positive focal length.

In zooming from the wide-angle end (short focal end) to the telephoto end (long focal end), the variable interval between the groups, that is, the most image side surface of the first lens group G1, that is, the image of the third lens E3. Distance DA between the second surface group (surface number 5) and the most object side surface of the second lens group G2, that is, the object side surface (surface number 6) of the fourth lens E4, and the most image of the second lens group G2. Side, that is, the distance DB between the image side surface (surface number 10) of the sixth lens E6 and the surface of the aperture FA (surface number 11), the surface of the aperture FA (surface number 11), and the third lens group The distance DC between the most object side surface of G3, that is, the object side surface (surface number 12) of the seventh lens E7, the most image side surface of the third lens group G3, that is, the image side surface of the ninth lens E9. (Surface number 16) and the most object-side surface of the fourth lens group G4, that is, the object-side surface of the tenth lens E10 (surface number 17) And the most image side surface of the fourth lens group G4, that is, the image side surface (surface number 18) of the tenth lens E10 and the object side surface (surface number 19) of the filter / cover FC. The first lens group G1 and the third lens group G3 move monotonously toward the object side as the distance DE changes and the magnification changes from the wide-angle end to the telephoto end. The first lens group G1, so that the second lens group G2 holds its position fixedly and the fourth lens group G4 is positioned closer to the image side than the wide-angle end at the telephoto end. The third lens group G3 and the fourth lens group G4 move.

  In the third embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 4.74 to 21.67, F = 3.46 to 4.91, and ω = by zooming, respectively. It varies in the range of 39.15-9.50. The characteristics of each optical surface are as shown in the following table.

In Table 5, each optical surface of the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface, and the seventeenth surface indicated by adding “*” to the surface number is an aspheric surface. The parameters in the equation are as follows:
Aspherical surface: 6th surface K = 0.0,
A ₄ = −1.225579 × 10 ⁻⁴ ,
A ₆ = −2.998179 × 10 ⁻⁷ ,
A ₈ = −1.93092 × 10 ⁻⁸ ,
A ₁₀ = −3.32554 × 10 ⁻¹⁰
Aspheric surface: 10th surface K = 0.0,
A ₄ = −8.25512 × 10 ⁻⁴ ,
A ₆ = −1.82812 × 10 ⁻⁵ ,
A ₈ = 8.50623 × 10 ⁻⁸ ,
A ₁₀ = −1.90374 × 10 ⁻⁷

Aspheric surface: 12th surface K = 0.0,
A ₄ = −8.08852 × 10 ⁻⁴ ,
A ₆ = 1.58812 × 10 ⁻⁵ ,
A ₈ = −1.00403 × 10 ⁻⁶ ,
A ₁₀ = 2.775151 × 10 ⁻⁸
Aspheric surface: 13th surface K = 0.0,
A ₄ = 4.007275 × 10 ⁻⁴ ,
A ₆ = −7.886358 × 10 ⁻⁶ ,
A ₈ = 1.660507 × 10 ⁻⁶ ,
A ₁₀ = −9.33131 × 10 ⁻⁸
Aspheric surface: 17th surface K = 0.0,
A ₄ = −1.29441 × 10 ⁻⁵ ,
A ₆ = 5.93123 × 10 ⁻⁶ ,
A ₈ = −3.01006 × 10 ⁻⁷ ,
A ₁₀ = 7.06450 × 10 ⁻⁹
A variable distance DA between the first lens group G1 and the second lens group G2, a variable distance DB between the second lens group G2 and the aperture FA, a variable distance DC between the aperture FA and the third lens group, The variable distance DD between the third lens group G3 and the fourth lens group G4 and the variable distance DE between the fourth lens group G4 and the optical filter FC are changed as shown in the following table with zooming. .

Further, the values according to the conditional expressions described in the third embodiment are as follows.
Conditional expression numerical value m4T = 0.712
m4T / m4W = 1.085
X1 / fT = 0.646
X3 / fT = 0.351
| F2 | /f3=0.744
f1 / fW = 7.49
Therefore, the numerical values related to the conditional expressions described in the third embodiment are within the range of the conditional expressions.

FIG. 4 shows the configuration of an optical system of a zoom lens according to Example 4 of the present invention, where (a) is a wide angle end (short focal end), (b) is an intermediate focal length, and (c) is telephoto. The state of the end (long focal end) is shown.
The zoom lens shown in FIG. 4 includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, and a ninth lens. A lens E9, a tenth lens E10, an aperture FA and a filter / cover FC are provided. In this case, the first lens E1 to the third lens E3 constitute the first lens group G1, the fourth lens E4 to the sixth lens E6 constitute the second lens group G2, and the seventh lens E7 to the ninth lens. The lens E9 constitutes the third lens group G3, and the tenth lens E10 alone constitutes the fourth lens group G4. Each lens E9 is supported by a common support frame or the like appropriate for each group, and zooming is performed. At the same time, each group operates integrally. 4 are used independently for each embodiment. Therefore, even if the same reference symbols as in FIGS. 1 to 3 are given, they are not necessarily different from the other embodiments. is not.

In FIG. 4, each optical element constituting the optical system of the zoom lens includes, for example, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, and a fifth lens sequentially from the object side such as a subject. E5, sixth lens E6, aperture FA, seventh lens E7, eighth lens E8, ninth lens E9, tenth lens E10 and filter / cover FC are arranged in this order, and are connected behind the filter / cover FC. Imaged.
The first lens E1 is a negative meniscus lens that is convex on the object side, and the second lens E2 is a positive lens that is a biconvex lens with a strong convex surface on the object side. The first lens E1 and the second lens E2 Are closely bonded and bonded together to form a cemented lens. The third lens E3 is a positive meniscus lens that is convexly formed on the object side. The first lens group G1 constituted by the first lens E1 to the third lens E3 has a positive refractive power as a whole. The fourth lens E4 is a negative meniscus lens that is convex toward the object side, has an aspheric surface on the object side, and a strong concave surface on the image side. The fifth lens E5 is a positive lens composed of a biconvex lens having a strong convex surface on the image side, and the sixth lens E6 is a negative lens having a biconcave lens having a strong concave surface on the object side, and an aspheric surface on the image side. The fifth lens E5 and the sixth lens E6 are intimately bonded and joined together to form a cemented lens.

The second lens group G2 constituted by the fourth lens E4 to the sixth lens E6 has a negative focal length, that is, negative refractive power as a whole. The seventh lens E7 is a positive lens composed of a biconvex lens having both aspheric surfaces. The eighth lens E8 is a positive lens made up of a biconvex lens with a strong convex surface facing the image side, and the ninth lens E9 is a negative lens made up of a biconcave lens. The eighth lens E8 and the ninth lens E9 are in close contact with each other. And bonded together to form a cemented lens. The third lens group G3 constituted by the seventh lens E7 to the ninth lens E9 has a positive refractive power as a whole. The tenth lens E10 is a positive lens made of a biconvex lens having a strong convex surface made of an aspheric surface facing the object side. Of course, the fourth lens group G4 constituted solely by the tenth lens E10 has a positive focal length.
In zooming from the wide-angle end (short focal end) to the telephoto end (long focal end), the variable interval between the groups, that is, the most image side surface of the first lens group G1, that is, the image of the third lens E3. Distance DA between the second surface group (surface number 5) and the most object side surface of the second lens group G2, that is, the object side surface (surface number 6) of the fourth lens E4, and the most image of the second lens group G2. Side, that is, the distance DB between the image side surface (surface number 10) of the sixth lens E6 and the surface of the aperture FA (surface number 11), the surface of the aperture FA (surface number 11), and the third lens group The distance DC between the most object side surface of G3, that is, the object side surface (surface number 12) of the seventh lens E7, the most image side surface of the third lens group G3, that is, the image side surface of the ninth lens E9. (Surface number 16) and the most object-side surface of the fourth lens group G4, that is, the object-side surface of the tenth lens E10 (surface number 17) And the most image side surface of the fourth lens group G4, that is, the image side surface (surface number 18) of the tenth lens E10 and the object side surface (surface number 19) of the filter / cover FC. The first lens group G1 and the third lens group G3 move monotonously toward the object side as the distance DE changes and the magnification changes from the wide-angle end to the telephoto end. The first lens group G1, so that the second lens group G2 holds its position fixedly and the fourth lens group G4 is positioned closer to the image side than the wide-angle end at the telephoto end. The third lens group G3 and the fourth lens group G4 move.
In the fourth embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 4.74-21.62, F = 3.42-4.99, and ω = by zooming, respectively. It varies in the range of 39.12 to 9.50. The characteristics of each optical surface are as shown in the following table.

In Table 7, each optical surface of the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface, and the seventeenth surface indicated by adding “*” to the surface number is an aspheric surface. The parameters in the equation are as follows:
Aspherical surface: 6th surface K = 0.0,
A ₄ = −8.08791 × 10 ⁻⁵ ,
A ₆ = −2.03124 × 10 ⁻⁶ ,
A ₈ = 6.26663 × 10 ⁻⁹ ,
A ₁₀ = −6.132352 × 10 ⁻¹¹
Aspheric surface: 10th surface K = 0.0,
A ₄ = −7.52609 × 10 ⁻⁴ ,
A ₆ = −1.24401 × 10 ⁻⁵ ,
A ₈ = −9.665466 × 10 ⁻⁷ ,
A ₁₀ = −8.33332 × 10 ⁻⁸

Aspheric surface: 12th surface K = 0.0,
A ₄ = −7.07947 × 10 ⁻⁴ ,
A ₆ = −1.116179 × 10 ⁻⁶ ,
A ₈ = 6.752505 × 10 ⁻⁸ ,
A ₁₀ = −2.53913 × 10 ⁻⁸
Aspheric surface: 13th surface K = 0.0,
A ₄ = 3.43658 × 10 ⁻⁴ ,
A ₆ = −1.44022 × 10 ⁻⁶ ,
A ₈ = −1.333484 × 10 ⁻⁷ ,
A ₁₀ = −1.40822 × 10 ⁻⁸
Aspheric surface: 17th surface K = 0.0,
A ₄ = −4.754010 × 10 ⁻⁵ ,
A ₆ = 1.15429 × 10 ⁻⁵ ,
A ₈ = −4.887258 × 10 ⁻⁷ ,
A ₁₀ = 9.55404 × 10 ⁻⁹
A variable distance DA between the first lens group G1 and the second lens group G2, a variable distance DB between the second lens group G2 and the aperture FA, a variable distance DC between the aperture FA and the third lens group, The variable distance DD between the third lens group G3 and the fourth lens group G4 and the variable distance DE between the fourth lens group G4 and the optical filter FC are changed as shown in the following table with zooming. .

Further, the values according to the conditional expressions described in the fourth embodiment are as follows.
Conditional expression numerical value m4T = 0.721
m4T / m4W = 1.095
X1 / fT = 0.668
X3 / fT = 0.369
| F2 | /f3=0.955
f1 / fW = 8.14
Therefore, the numerical values related to the conditional expressions described in the fourth embodiment are within the range of the conditional expressions.

5 to 7 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration in the zoom lens shown in FIG. 1 according to Example 1 described above, and FIG. FIG. 6 is an aberration curve diagram at the intermediate focal length, and FIG. 7 is an aberration curve diagram at the telephoto end. In each aberration curve diagram, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, the broken line represents meridional, the thick line represents the d line, and the thin line represents the g line.
8 to 10 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration in the zoom lens shown in FIG. 2 according to Example 2 described above, and FIG. FIG. 9 is an aberration curve diagram at the intermediate focal length, and FIG. 10 is an aberration curve diagram at the telephoto end. Also in this case, in each aberration curve diagram, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, the broken line represents meridional, the thick line represents the d line, and the thin line represents the g line. .

FIGS. 11 to 13 show aberration curve diagrams of spherical aberration, astigmatism, distortion and coma aberration in the zoom lens shown in FIG. 3 according to Example 3 described above. FIG. FIG. 12 is an aberration curve diagram at the intermediate focal length, and FIG. 13 is an aberration curve diagram at the telephoto end. Also in this case, in each aberration curve diagram, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, the broken line represents meridional, the thick line represents the d line, and the thin line represents the g line. .
14 to 16 show aberration curve diagrams of spherical aberration, astigmatism, distortion aberration, and coma aberration in the zoom lens shown in FIG. 4 according to Example 4 described above, and FIG. FIG. 15 is an aberration curve diagram at the intermediate focal length, and FIG. 16 is an aberration curve diagram at the telephoto end. Also in this case, in each aberration curve diagram, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, the broken line represents meridional, the thick line represents the d line, and the thin line represents the g line. .
According to the aberration curve diagrams of FIGS. 5 to 16, all the zoom lenses having the configurations shown in FIGS. 1 to 4 according to the first to fourth embodiments of the present invention described above are corrected favorably. It can be seen that it is suppressed or suppressed.

  Next, referring to FIGS. 17 to 19 for Embodiment 5 of the present invention in which the zoom lens according to the present invention as shown in Embodiments 1 to 4 described above is employed as a photographing optical system to constitute a camera. To explain. 17 is a perspective view showing the appearance of the camera as seen from the front side that is the object, that is, the subject side, and FIG. 18 is a perspective view showing the appearance of the camera as seen from the back side that is the photographer side. These are block diagrams which show the function structure of a camera. Although a camera is described here, a camera in which a camera function is incorporated in a personal digital assistant such as a so-called PDA (personal data assistant) or a mobile phone has recently appeared. Such a portable information terminal device also includes substantially the same function and configuration as a camera although the appearance is slightly different. Even if the zoom lens according to the present invention is adopted in such a portable information terminal device, Good.

As shown in FIGS. 17 and 18, the camera includes a photographing lens 101, a shutter button 102, a zoom lever 103, a finder 104, a strobe 105, a liquid crystal monitor 106, an operation button 107, a power switch 108, a memory card slot 109, and a communication card. A slot 110 and the like are provided. Furthermore, as shown in FIG. 19, the camera also includes a light receiving element 201, a signal processing device 202, an image processing device 203, a central processing unit (CPU) 204, a semiconductor memory 205, a communication card 206, and the like.
The camera includes a photographing lens 101 and a light receiving element 201 as an area sensor such as a CCD (Charge Coupled Device) imaging element, and is an object to be photographed, that is, a subject formed by the photographing lens 101 that is a photographing optical system. These images are read by the light receiving element 201. As the photographing lens 101, the zoom lens according to the present invention as described in the first to fourth embodiments is used. Specifically, the lens unit is configured using a lens or the like that is an optical element configuring the zoom lens. This lens unit has a mechanism for holding each lens or the like so that it can be moved and operated at least for each lens group. The photographing lens 101 incorporated in the camera is usually incorporated in the form of this lens unit.
The output of the light receiving element 201 is processed by the signal processing device 202 controlled by the central processing unit 204 and converted into digital image information.

The image information digitized by the signal processing device 202 is subjected to predetermined image processing in the image processing device 203 which is also controlled by the central processing unit 204 and then recorded in the semiconductor memory 205 such as a nonvolatile memory. In this case, the semiconductor memory 205 may be a memory card loaded in the memory card slot 109 or a semiconductor memory built in the camera body. The liquid crystal monitor 106 can display an image being shot, and can also display an image recorded in the semiconductor memory 205. The image recorded in the semiconductor memory 205 can also be transmitted to the outside via a communication card 206 or the like loaded in the communication card slot 110.
When the camera is carried, the photographic lens 101 is in the retracted state and buried in the camera body as shown in FIG. 17A. When the user operates the power switch 108 to turn on the power, FIG. (B), the lens barrel is extended and protrudes from the camera body. At this time, in the lens barrel of the photographing lens 101, the optical systems of the respective groups constituting the zoom lens are arranged at the wide-angle end, for example, and by operating the zoom lever 103, the arrangement of the respective group optical systems is arranged. Is changed, and the zooming operation to the telephoto end can be performed. It is desirable that the optical system of the finder 104 is also used for zooming in conjunction with the change in the angle of view of the photographing lens 101.

In many cases, focusing is performed by half-pressing the shutter button 102. Positive according to the present invention - negative - positive - Focusing definitive in Zumuren's composed of a positive four groups, the movement of the first lens group G1, or may result from the movement of the second lens group G2. When the shutter button 102 is further pushed down to the fully depressed state, photographing is performed, and then the processing as described above is performed.
When the image recorded in the semiconductor memory 205 is displayed on the liquid crystal monitor 106 or transmitted to the outside via the communication card 206 or the like, the operation button 107 is operated in a predetermined manner. The semiconductor memory 205 and the communication card 206 are used by being loaded into dedicated or general-purpose slots such as the memory card slot 109 and the communication card slot 110, respectively.
When the photographing lens 101 is in the retracted state, each group of zoom lenses does not necessarily have to be aligned on the optical axis. For example, if the third lens group G3 is retracted from the optical axis when retracted and is accommodated in parallel with the first lens group G1 and the second lens group G2, the camera can be made thinner. be able to.
In the above-described camera or portable information terminal device, as described above, the photographing lens 101 including the lens unit using the zoom lens as described in the first to fourth embodiments is used as a photographing optical system. be able to. Accordingly, it is possible to realize a small camera or a portable information terminal device with high image quality using a light receiving element of 3 to 5 million pixel class.

1 is a cross-sectional view along an optical axis schematically showing the configuration of an optical system of a zoom lens according to Example 1 of the present invention. It is sectional drawing along the optical axis which shows typically the structure of the optical system of the zoom lens which concerns on Example 2 of this invention. It is sectional drawing along the optical axis which shows typically the structure of the optical system of the zoom lens which concerns on Example 3 of this invention. It is sectional drawing along the optical axis which shows typically the structure of the optical system of the zoom lens which concerns on Example 4 of this invention. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Embodiment 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Embodiment 2 of the present invention shown in FIG. 2. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 2 of the present invention shown in FIG. 2. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Example 2 of the present invention shown in FIG. 2. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Embodiment 3 of the present invention shown in FIG. 3. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Embodiment 3 of the present invention shown in FIG. 3. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Embodiment 3 of the present invention shown in FIG. 3. FIG. 5 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Embodiment 4 of the present invention shown in FIG. 4. FIG. 5 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Embodiment 4 of the present invention shown in FIG. 4. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Embodiment 4 of the present invention shown in FIG. 4. FIG. 7A is a perspective view schematically showing an external configuration of a camera according to Example 5 of the present invention as viewed from the object side, in which FIG. 9A is a state in which the photographing lens is retracted in the camera body, and FIG. It shows a state in which the taking lens protrudes from the camera body. It is the perspective view seen from the photographer side which shows typically the external appearance structure of the camera of FIG. It is a block diagram which shows typically the function structure of the camera of FIG.

Explanation of symbols

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group E1 to E10 Lens FA Aperture FC filter / cover 101 Shooting lens 102 Shutter button 103 Zoom lever 104 Viewfinder 105 Strobe 106 Liquid crystal Monitor 107 Operation button 108 Power switch 109 Memory card slot 110 Communication card slot 201 Light receiving element (area sensor)
202 Signal Processing Unit 203 Image Processing Unit 204 Central Processing Unit (CPU)
205 Semiconductor memory 206 Communication card, etc.

Claims (12)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a positive refractive power. Zoom lens in which the first lens group and the third lens group move monotonously toward the object side in response to zooming from the wide-angle end to the telephoto end. In
During zooming from the wide-angle end to the telephoto end, the second lens group holds its position fixedly, and the fourth lens group moves at the telephoto end so that it is positioned closer to the image side than the wide-angle end.
The imaging magnification of the fourth lens group at the telephoto end is m4T , the total movement amount of the first lens group accompanying the zooming from the wide-angle end to the telephoto end is X1, and the focal length of the entire system at the telephoto end is fT.
Conditional expression:
0.65 <m4T <0.80
0.60 <X1 / fT <0.75
A zoom lens characterized by satisfying The imaging magnification of the fourth lens group at the telephoto end is m4T, and the imaging magnification of the fourth lens group at the wide angle end is m4W.
Conditional expression:
1.0 <m4T / m4W <1.3
The zoom lens according to claim 1, wherein: X3 is the total amount of movement of the third lens unit during zooming from the wide-angle end to the telephoto end, and fT is the focal length of the entire system at the telephoto end.
Conditional expression:
0.25 <X3 / fT <0.50
The zoom lens according to claim 1 or claim 2, characterized by satisfying the. The focal length of the second lens group is f2, and the focal length of the third lens group is f3.
Conditional expression:
0.6 <| f2 | / f3 <1.0
Any zoom lens according to one of claims 1 to claim 3, characterized by satisfying the. The focal length of the first lens group is f1, and the focal length of the entire system at the wide angle end is fW.
Conditional expression:
6.0 <f1 / fW <12.0
The zoom lens according to any one of claims 1 to claim 4, characterized by satisfying the. In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a positive refractive power. Zoom lens in which the first lens group and the third lens group move monotonously toward the object side in response to zooming from the wide-angle end to the telephoto end. In
During zooming from the wide-angle end to the telephoto end, the second lens group holds its position fixedly, and the fourth lens group moves at the telephoto end so that it is positioned closer to the image side than the wide-angle end.
Assuming that the total movement amount of the first lens group accompanying the zooming from the wide angle end to the telephoto end is X1, the focal length of the entire system at the telephoto end is fT,
Conditional expression:
0. 60 <X1 / fT <0. 75
A zoom lens characterized by satisfying The aperture stop moves independently of an adjacent lens group, and an interval between the aperture stop and the third lens group is widest at a wide angle end and narrowest at a telephoto end. The zoom lens according to any one of claims 1 to 6 . The second lens group includes, from the object side, a negative lens having a large curvature surface facing the image side, a positive lens having a large curvature surface facing the image side, and a large curvature surface facing the object side. The zoom lens according to any one of claims 1 to 7 , wherein the zoom lens includes three lenses sequentially arranged with a negative lens. The refractive index of the i-th lens counted from the object side in the second lens group is N2i, and the Abbe number of the i-th lens counted from the object side in the second lens group is ν2i.
Conditional expression:
1.75 <N21 <1.90, 35 <ν21 <50,
1.65 <N22 <1.90, 20 <ν22 <35,
1.75 <N23 <1.90, 35 <ν23 <50
The zoom lens according to claim 8 , wherein: An optical system including the zoom lens according to any one of claims 1 to 9 , and each optical element constituting the optical system, and each optical element is provided at least for each lens group. A lens unit comprising a moving mechanism. A camera comprising the zoom lens according to any one of claims 1 to 9 as a photographing optical system. As the camera function of the photographic optical system, a portable information terminal device which comprises a zoom lens according to any one of claims 1 to 9.

Images