JP4642883B2 - Zoom lens, camera, and portable information terminal device - Google Patents

Description

  The present invention relates to an improvement of a zoom lens used as a photographing optical system in various cameras including a so-called silver salt camera, and more particularly to a zoom lens suitable for a camera such as a digital camera and a video camera, and such a zoom lens. The present invention relates to a camera and a portable information terminal device using the.

In recent years, instead of a conventional camera using a silver salt film, that is, a silver salt camera, 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. However, a camera of a type that obtains image data of a still image (still image) or a moving image (movie image) of a subject and digitally records it in a nonvolatile semiconductor memory or the like represented by a flash memory is rapidly spreading. is there.
The market for such digital cameras is very large, and the demands of users for digital cameras are also diverse. In particular, high image quality and miniaturization are always desired by users in cameras, and occupy great weight. Therefore, a zoom lens used as a photographic lens is also required to have both high performance and small size.

Here, in terms of miniaturization, first, it is necessary to shorten the entire lens length (the distance from the lens surface closest to the object side to the image plane). Furthermore, in terms of high performance, it is necessary to have a resolving power corresponding to an image sensor with at least 3 to 6 million pixels over the entire zoom range.
In addition, there are many users who wish to widen the angle of view of the taking lens, and it is desirable that the half angle of view at the short focal point of the zoom lens is 38 degrees or more. The half angle of view of 38 degrees corresponds to 28 mm in focal length converted to a camera using a 35 mm silver salt film (so-called Leica plate).

  There are many types of zoom lenses that can be used as photographing lenses for digital cameras, but as a zoom lens suitable for miniaturization, a first group optical system having a negative focal length in order from the object side, and a positive lens. And a second group optical system having a positive focal length and a third group optical system having a positive focal length are arranged in an array, and integrated with the second group optical system on the object side of the second group optical system The second group optical system moves monotonically from the image side to the object side during zooming from the short focal end to the long focal end, and the first group optical system Some move so as to correct fluctuations in image plane position due to zooming. Such zoom lenses are disclosed in, for example, Patent Document 1, Patent Document 2, and Patent Document 3.

JP 10-39214 A JP-A-10-104518 JP 2001-296476 A

  However, what is disclosed in Patent Document 1 was filed at the earliest time as a zoom lens of the type described above, and all the basic configurations of the zoom lens of the type described above have been disclosed, but are small in size. In terms of conversion, it does not have a sufficient structure. The configuration disclosed in Patent Document 2 takes into account the occurrence of decentration during assembly using a cemented lens. However, sufficient aberration correction is not performed, and 3 to 6 million pixels. It does not have the performance that can correspond to the image pickup device. And what was disclosed by patent document 3 is comparatively small, and image performance is better than what was described previously, but the half angle of view has stopped at about 33 degree | times, and it is called widening. It ’s not enough in terms.

The present invention has been made in view of the above-described circumstances, and at least a first group optical system having a negative focal length and a second group optical system having a positive focal length are sequentially arranged from the object side. In addition, the zoom lens has a diaphragm that moves integrally with the second group optical system, and the second group optical system moves monotonically from the image side to the object side during zooming from the short focal end to the long focal end. In addition, the first group optical system is sufficiently small and can obtain a wide angle of view by using a configuration that moves so as to correct fluctuations in image plane position due to zooming, and has high performance. It is an object of the present invention to provide a zoom lens, a camera, and a portable information terminal device having sufficient resolution.
That is, the object of claim 1 of the present invention is particularly small in size and capable of obtaining a wide angle of view, has high performance, and corrects spherical aberration, astigmatism and coma well. An object of the present invention is to provide a zoom lens that can obtain a resolving power corresponding to an image sensor with 3 to 6 million pixels.
Further, an object of claim 2 of the present invention is to provide a zoom lens that can correct chromatic aberration more satisfactorily and achieve higher performance.

The object of the third aspect of the present invention is to provide a zoom lens that can correct the curvature of field mainly more favorably and achieve higher performance.
A fourth object of the present invention is to provide a zoom lens that can balance the monochromatic aberration and the chromatic aberration, and achieve higher performance.
An object of claim 5 of the present invention is to provide a zoom lens which can improve the performance by correcting mainly monochromatic aberrations more satisfactorily .

The object of claim 6 of the present invention is to obtain a resolving power corresponding to an image sensor of 3 to 6 million pixels, in particular, sufficiently small and capable of obtaining a wide angle of view and having high performance. An object of the present invention is to provide a camera that is small and can obtain high image quality by using a zoom lens as a photographing optical system.
The object of claim 7 of the present invention is to obtain a resolving power corresponding to an image sensor of 3 to 6 million pixels, in particular, sufficiently small and capable of obtaining a wide angle of view and high performance. An object of the present invention is to provide a portable information terminal device that is small in size and can obtain high image quality by using a zoom lens as a photographing optical system of a camera function unit.

In order to achieve the above-described object, the zoom lens according to the present invention described in claim 1
A first group optical system having a negative focal length, a second group optical system having a positive focal length, and a third group optical system having a positive focal length are sequentially arranged from the object side, and A diaphragm that moves integrally with the second group optical system on the object side of the second group optical system;
Upon zooming from the short focal end to the long focal end, the distance between the first group optical system and the second group optical system is gradually reduced, and the distance between the second group optical system and the third group optical system is reduced. In the zoom lens in which the first group optical system to the third group optical system are moved so that is gradually increased,
The second group optical system includes, in order from the object side, a positive lens having a large curvature surface facing the object side, a negative meniscus lens having a concave surface facing the image side, a positive meniscus lens cemented to the negative meniscus lens, and It consists of an optical system with 3 groups and 4 elements in which positive lenses are arranged.
Then, the distance from the vertex of the object side surface of the positive lens closest to the object side of the second group optical system to the vertex of the junction surface between the negative meniscus lens and the positive meniscus lens of the second group optical system is expressed as L _PN , the thickness of the optical axis direction of the second group optical system as L _2,
Conditional expression:
0.40 <(L _PN / L ₂ ) <0.70
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,
In the second group optical system, the Abbe number of the negative meniscus lens is ν ₂₂ , and the Abbe number of the positive meniscus lens joined to the negative meniscus lens is ν ₂₃ ,
Conditional expression:
25 <(ν ₂₃ −ν ₂₂ ) <50
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,
The radius of curvature of the object side surface of the most object side positive lens in the second group optical system is r _21F , the radius of curvature of the object side surface of the negative meniscus lens in the second group optical system is r _22F , and the second group optical system. _{Where the} radius of curvature of the cemented surface between the negative meniscus lens and the positive meniscus lens is r _22R and the maximum image height is Y ′.
Conditional expression:
1.40
<((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′)
<2.20
It is characterized by satisfying.

The zoom lens according to the present invention described in claim 4 is the zoom lens according to any one of claims 1 to claim 3,
The curvature of the cemented surface between the negative meniscus lens and the positive meniscus lens of the second group optical system is the largest among all the surfaces of the second group optical system.
The zoom lens according to the present invention described in claim 5 is the zoom lens according to claim 3 or 4 , wherein
It is characterized in that the most object side surface and the most image side surface of the second group optical system are aspherical surfaces.

The camera according to the present invention described in claim 6 includes the zoom lens according to any one of claims 1 to 5 as a photographing optical system in order to achieve the above-described object. It is characterized by.
According to a seventh aspect of the present invention, there is provided a portable information terminal device according to any one of the first to fifth aspects as a photographing optical system of a camera function unit in order to achieve the above-described object. The zoom lens described above is included.

  As described above, according to the present invention, at least the first group optical system having a negative focal length and the second group optical system having a positive focal length are sequentially arranged from the object side, and The zoom lens has a diaphragm that moves integrally with the second group optical system, and the second group optical system moves monotonically from the image side to the object side during zooming from the short focal end to the long focal end, The first group optical system uses a configuration that moves so as to correct fluctuations in image plane position due to zooming, and is sufficiently small and capable of obtaining a wide angle of view. It is possible to provide a zoom lens, a camera, and a portable information terminal device having high resolution.

That is, according to the zoom lens of the first aspect of the present invention, the first group optical system having the negative focal length, the second group optical system having the positive focal length, and the positive focal length sequentially from the object side. And a third group optical system having an aperture that moves integrally with the second group optical system on the object side of the second group optical system,
Upon zooming from the short focal end to the long focal end, the distance between the first group optical system and the second group optical system is gradually reduced, and the distance between the second group optical system and the third group optical system is reduced. In the zoom lens in which the first group optical system to the third group optical system are moved so that is gradually increased,
The second group optical system includes, in order from the object side, a positive lens having a large curvature surface facing the object side, a negative meniscus lens having a concave surface facing the image side, a positive meniscus lens cemented to the negative meniscus lens, and It consists of an optical system with 3 groups and 4 elements in which positive lenses are arranged.
Then, the distance from the vertex of the object side surface of the positive lens closest to the object side of the second group optical system to the vertex of the junction surface between the negative meniscus lens and the positive meniscus lens of the second group optical system is expressed as L _PN , the thickness of the optical axis direction of the second group optical system as L _2,
Conditional expression:
0.40 <(L _PN / L ₂ ) <0.70
Satisfying at least the first group optical system having a negative focal length and the second group optical system having a positive focal length sequentially from the object side, and the second group optical system The first group optical system has a stop that moves integrally, and the second group optical system moves monotonically from the image side to the object side during zooming from the short focus end to the long focus end. By using a configuration that moves so as to correct fluctuations in image plane position due to zooming, a sufficiently small size and a wide angle of view can be obtained, and it has high performance , spherical aberration, astigmatism and It is possible to obtain a resolution corresponding to an image sensor with 3 to 6 million pixels by correcting coma well .

According to the zoom lens of claim 2 of the present invention, in the zoom lens of claim 1, the Abbe number of the negative meniscus lens in the second group optical system is ν ₂₂ , and the negative meniscus lens is joined to the negative lens. The Abbe number of the positive meniscus lens is ν ₂₃ ,
Conditional expression:
25 <(ν ₂₃ −ν ₂₂ ) <50
In particular, the chromatic aberration can be corrected more satisfactorily and higher performance can be achieved.

According to the zoom lens of claim 3 of the present invention, in the zoom lens of claim 1 or 2, the radius of curvature of the object side surface of the most object-side positive lens in the second group optical system is r _21F , The radius of curvature of the object side surface of the negative meniscus lens in the second group optical system is r _22F , the radius of curvature of the joint surface between the negative meniscus lens and the positive meniscus lens in the second group optical system is r _22R , and the maximum Let the image height be Y ',
Conditional expression:
1.40
<((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′)
<2.20
By satisfying the above, in particular, it is possible to correct the curvature of field more favorably and achieve higher performance.

According to the zoom lens according to claim 4 of the present invention, claims 1 at any zoom lens according to one of claim 3, wherein the positive meniscus lens and the negative meniscus lens of the second group optical system With the configuration in which the curvature of the cemented surface is the largest among all the surfaces of the second group optical system, it is possible to achieve a higher performance particularly by balancing monochromatic aberration and chromatic aberration.

According to the zoom lens of claim 5 of the present invention, in the zoom lens of claim 3 or claim 4, the most object side surface and the most image side surface of the second group optical system are aspherical surfaces. According to the configuration, particularly, monochromatic aberration can be corrected more satisfactorily and higher performance can be achieved.

According to the camera of claim 6 of the present invention, the zoom lens according to any one of claims 1 to 5 is included as a photographing optical system, so that it is sufficiently small and wide. It is possible to obtain a small angle and high image quality by using a zoom lens that can obtain an angle of view, has high performance, and has a resolving power corresponding to an image sensor with 3 to 6 million pixels as a photographing optical system. it can.

According to the portable information terminal device of the seventh aspect of the present invention, the zoom lens according to any one of the first to fifth aspects is included as an imaging optical system of the camera function unit. A zoom lens that is sufficiently small and capable of obtaining a wide angle of view, has high performance, and has a resolving power corresponding to an image sensor with 3 to 6 million pixels is used as a photographing optical system of the camera function unit. Thus, it is small and high image quality can be obtained.

[Action]
That is, the zoom lens according to claim 1 of the present invention is:
A first group optical system having a negative focal length, a second group optical system having a positive focal length, and a third group optical system having a positive focal length are sequentially arranged from the object side, and A diaphragm that moves integrally with the second group optical system on the object side of the second group optical system;
Upon zooming from the short focal end to the long focal end, the distance between the first group optical system and the second group optical system is gradually reduced, and the distance between the second group optical system and the third group optical system is reduced. In the zoom lens in which the first group optical system to the third group optical system are moved so that is gradually increased,
The second group optical system includes, in order from the object side, a positive lens having a large curvature surface facing the object side, a negative meniscus lens having a concave surface facing the image side, a positive meniscus lens cemented to the negative meniscus lens, and It consists of an optical system with 3 groups and 4 elements in which positive lenses are arranged.
Then, the distance from the vertex of the object side surface of the positive lens closest to the object side of the second group optical system to the vertex of the junction surface between the negative meniscus lens and the positive meniscus lens of the second group optical system is expressed as L _PN , the thickness of the optical axis direction of the second group optical system as L _2,
Conditional expression:
0.40 <(L _PN / L ₂ ) <0.70
Satisfied.

With such a configuration, at least a first group optical system having a negative focal length and a second group optical system having a positive focal length are sequentially arranged from the object side, and the second group optical system The first group optical system has a stop that moves integrally, and the second group optical system moves monotonically from the image side to the object side during zooming from the short focus end to the long focus end. , using the configuration that moves so as to correct the variation of the image plane position accompanying the magnification, sufficiently possible to obtain a small and wide angle of view, yet a high-performance, spherical aberration, astigmatism, and It is possible to obtain a resolving power corresponding to an image sensor with 3 to 6 million pixels by correcting coma well .

A zoom lens according to a second aspect of the present invention is the zoom lens according to the first aspect,
In the second group optical system, the Abbe number of the negative meniscus lens is ν ₂₂ , and the Abbe number of the positive meniscus lens joined to the negative meniscus lens is ν ₂₃ ,
Conditional expression:
25 <(ν ₂₃ −ν ₂₂ ) <50
Satisfied.

With such a configuration, in particular, chromatic aberration can be corrected more satisfactorily and higher performance can be achieved.
A zoom lens according to a third aspect of the present invention is the zoom lens according to the first or second aspect,
The radius of curvature of the object side surface of the most object side positive lens in the second group optical system is r _21F , the radius of curvature of the object side surface of the negative meniscus lens in the second group optical system is r _22F , and the second group optical system. _{Where the} radius of curvature of the cemented surface between the negative meniscus lens and the positive meniscus lens is r _22R and the maximum image height is Y ′.
Conditional expression:
1.40
<((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′)
<2.20
Satisfied.

With such a configuration, in particular, it is possible to correct the curvature of field more favorably and achieve higher performance .

The zoom lens according to claim 4 of the present invention, in the zoom lens according to any one of claims 1 to claim 3, wherein said negative meniscus lens in the second group optical system and between the positive meniscus lens The curvature of the cemented surface is the largest among all the surfaces of the second group optical system.
With such a configuration, it is possible to balance the monochromatic aberration and chromatic aberration, and to further improve the performance.
The zoom lens according to a fifth aspect of the present invention is the zoom lens according to the third or fourth aspect , wherein the most object side surface and the most image side surface of the second group optical system are aspherical surfaces.
With such a configuration, in particular, it is possible to further improve the performance by mainly correcting the monochromatic aberration more satisfactorily.

A camera according to a sixth aspect of the present invention includes the zoom lens according to any one of the first to fifth aspects as a photographing optical system.
With such a configuration, a zoom lens that is sufficiently small and has a wide angle of view and that has high performance and that has a resolution corresponding to an image sensor with 3 to 6 million pixels is used as a photographing optical system. Thus, it is possible to obtain a small image quality.
A portable information terminal device according to a seventh aspect of the present invention includes the zoom lens according to any one of the first to fifth aspects as a photographing optical system of a camera function unit.
With such a configuration, a zoom lens capable of obtaining a sufficiently small and wide angle of view and having high performance and a resolving power corresponding to an image sensor with 3 to 6 million pixels can be captured by the camera function unit. By using it as an optical system, it is possible to obtain a small image quality.

Hereinafter, a zoom lens, a camera, and a portable information terminal device of the present invention will be described in detail based on examples with reference to the drawings. Before describing specific embodiments, first, in order to explain the basic configuration of the present invention, configurations and functions defined in the claims of the claims will be described.
The zoom lens according to the present onset Ming, in order from the object side, a third group having a first group optical system having a negative focal length, and the second group optical system having a positive focal length, a positive focal length And an aperture that moves integrally with the second group optical system on the object side of the second group optical system, and at the time of zooming from the short focus end to the long focus end, A zoom lens in which the optical system of each group moves so that the distance between the first group optical system and the second group optical system is gradually decreased and the distance between the second group optical system and the third group optical system is gradually increased. , and the these zoom lens is further respectively have the following characteristics.

In the zoom lens according to claim 1, the second group optical system includes, from the object side, a positive lens having a large curvature surface facing the object side, a negative meniscus lens having a concave surface facing the image side, and the negative meniscus a positive meniscus lens bonded to the lens, and a positive lens Ri Do three groups of four configurations of arranging the front SL most object side of the positive lens and the second group optical system from the apex of the object side surface of the second group optical system When the distance to the apex of the cemented surface between the negative meniscus lens and the positive meniscus lens is L _PN , and the thickness in the optical axis direction of the second group optical system is L ₂ , the following conditional expression is satisfied.
0.40 <(L _PN / L ₂ ) <0.70
The zoom lens according to claim 2 is the zoom lens according to claim 1, wherein an Abbe number of the negative meniscus lens of the second group optical system is ν ₂₂ , and an Abbe number of the positive meniscus lens joined to the negative meniscus lens. When ν ₂₃ is satisfied, the following conditional expression is satisfied.

25 <(ν ₂₃ −ν ₂₂ ) <50
A zoom lens according to a third aspect is the zoom lens according to the first or second aspect, wherein the radius of curvature of the object side surface of the positive lens closest to the object side of the second group optical system is r _21F , and the second group optical system. R _{22F is} the radius of curvature of the object side surface of the negative meniscus lens, r _{22R is} the radius of curvature of the junction surface between the negative meniscus lens and the positive meniscus lens of the second optical system, and Y ′ is the maximum image height. When the following conditional expression is satisfied.

1.40
<((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′)
<2.2 0

The zoom lens according to 請 Motomeko 4, in the zoom lens according to any one of claims 1 to claim 3, bonding between the negative meniscus lens and the positive meniscus lens of the second group optical system The curvature of the surface is the largest curvature among all the surfaces of the second group optical system.
A zoom lens according to a fifth aspect is the zoom lens according to the third or fourth aspect , wherein the most object side surface and the most image side surface of the second group optical system are aspherical surfaces.

A camera according to a sixth aspect of the present invention includes the zoom lens according to any one of the first to fifth aspects as a photographing optical system.
A portable information terminal device according to a seventh aspect of the present invention includes the zoom lens according to any one of the first to fifth aspects as a photographing optical system of a camera function unit.

In a zoom lens composed of three groups of negative, positive and positive, such as the zoom lens according to the present invention, the second group optical system is generally arranged from the image side at the time of zooming from the short focal end to the long focal end. It moves monotonously toward the object side, and the first group optical system moves so as to correct the fluctuation of the image plane position due to zooming. Most of the zooming function is performed by the second group optical system, and the third group optical system is provided mainly to keep the exit pupil away from the image plane.
In order to realize a zoom lens with a small amount of various aberrations and a high resolving power, aberration variation due to zooming must be kept small, and the second group optical system, which is the main zooming group, is particularly good in the entire zooming range. It is necessary to correct the aberration. For this reason, it is conceivable to increase the number of components of the second group optical system. However, the increase in the number of components leads to an increase in the thickness of the second group optical system in the optical axis direction, and a sufficient size reduction can be achieved. Not only will it disappear, it will also increase costs.
The second group optical system composed of four or less lenses includes a positive lens, a negative lens, and a positive lens arranged in order from the object side, and a positive lens and a positive lens in order from the object side. And three negative lenses, four lenses, positive lens, positive lens, negative lens and positive lens in order from the object side, and positive lens and negative lens in order from the object side There are known a negative lens and a positive lens that are arranged in four, and the present invention realizes the configuration of the second group optical system having an aberration correction capability exceeding these.

  That is, in the present invention, the second group optical system is composed of four lenses arranged in the order of a positive lens, a negative lens, a positive lens, and a positive lens from the object side. Since the aperture stop is disposed on the object side of the second group optical system, the off-axis rays pass away from the optical axis toward the lens surface on the image side farther from the aperture stop in the second group optical system. Increased involvement in correction of external aberrations. The second group optical system as a whole has a symmetrical arrangement with positive power on both sides of the negative power, but two positive powers on the image side that are deeply involved in correcting off-axis aberrations. By dividing the lens, the degree of freedom increases, and good correction of off-axis aberrations becomes possible.

  Further, in the present invention, the second group optical system is sequentially joined from the object side to a positive lens having a large curvature surface facing the object side, a negative meniscus lens having a concave surface facing the image side, and the negative meniscus lens. The positive meniscus lens and the three lens groups and four lens groups in which the positive lenses are arranged. Joining the second negative lens and the third positive lens from the object side is effective in suppressing assembly eccentricity and reducing assembly man-hours. Furthermore, the second negative lens from the object side is formed in a meniscus shape to give positive power to the side surface of the object, thereby sharing the positive power with the most positive lens on the object side, and the third positive lens from the object side. By making the lens a meniscus shape and giving negative power to the image side surface, the negative power is shared with the cemented surface to prevent excessive aberration from occurring on a specific surface, and the entire second group optical system The reduction in the amount of aberration and the reduction in manufacturing error sensitivity are both achieved.

In addition, with the configuration that satisfies the following condition, that Do is possible to sufficiently correct aberrations.

0.15 <(N ₂₂ −N ₂₃ ) <0.40
N ₂₂ represents the refractive index of the negative meniscus lens of the second group optical system, and N ₂₃ represents the refractive index of the positive meniscus lens cemented to the negative meniscus lens.
In this case, if (N ₂₂ −N ₂₃ ) is 0.15 or less, it becomes difficult to give a sufficient negative power to the joint surface, and the curvature of field cannot be corrected completely. On the other hand, when (N ₂₂ −N ₂₃ ) is 0.4 or more, a very high refractive index is required for the negative meniscus lens, resulting in an increase in manufacturing cost. It is more desirable to configure so as to satisfy the following conditional expression.

0.20 <(N ₂₂ −N ₂₃ ) <0.40
To perform a more satisfactory chromatic aberration correction is not to desired be configured to satisfy the following condition.

25 <(ν ₂₃ −ν ₂₂ ) <50
Here, ν ₂₂ represents the Abbe number of the negative meniscus lens of the second group optical system, and ν ₂₃ represents the Abbe number of the positive meniscus lens joined to the negative meniscus lens.
In this case, if (ν ₂₃ −ν ₂₂ ) is 25 or less, chromatic aberration cannot be sufficiently controlled on the joint surface, and it is difficult to achieve both correction of axial chromatic aberration and correction of lateral chromatic aberration. On the other hand, setting (ν ₂₃ −ν ₂₂ ) to 50 or more requires very small dispersion for the positive meniscus lens, which leads to an increase in manufacturing cost. It is more desirable to configure so as to satisfy the following conditional expression.

30 <(ν ₂₃ −ν ₂₂ ) <50
Furthermore, in order to improve the image plane curvature is not to desired be configured to satisfy the following condition.
1.40
<((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′)
<2.20
Where r _21F is the radius of curvature of the object side surface of the positive lens closest to the object side of the second group optical system, r _22F is the radius of curvature of the object side surface of the negative meniscus lens of the second group optical system, and r _22R is The radius of curvature of the cemented surface between the negative meniscus lens and the positive meniscus lens of the second group optical system, and Y ′ represent the maximum image height.

In this case, if ((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′) is increased beyond 1.40, the field curvature of the second group optical system can be increased. It is possible to sufficiently correct, and it is possible to maintain the flatness of the image plane over the entire zoom range. However, if ((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′) is increased to 2.20 or more, the aberration generated on each surface of the second group optical system is increased. As the size increases, the exchange of aberration increases, and the manufacturing error sensitivity increases. It is more desirable to configure so as to satisfy the following conditional expression.

1.55
<((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′)
<2.05
Further, spherical aberration, in order to improve the astigmatism and coma aberration are not to desired be configured to satisfy the following condition.

0.40 <(L _PN / L ₂ ) <0.70
Where L _PN is the distance from the vertex of the object side surface of the positive lens closest to the object side of the second group optical system to the vertex of the cemented surface of the negative meniscus lens and the positive meniscus lens of the second group optical system, L ₂ Represents the thickness of the second group optical system in the optical axis direction.

In the second group optical system, the object side surface of the positive lens closest to the object side and the cemented surface of the negative meniscus lens and the positive meniscus lens both have a small curvature, greatly exchange aberrations with each other, and contribute most to aberration correction. is doing. In order to perform good aberration correction, the height of the light beam passing through these two surfaces is important. When (L _PN / L ₂ ) is 0.40 or less, the height of the off-axis principal ray on the image side surface of the second negative lens from the object side becomes too small, and correction of astigmatism and coma is insufficient. The case comes out. On the other hand, when (L _PN / L ₂ ) is 0.70 or more, the axial marginal ray height on the image side surface of the second negative lens from the object side becomes too small, and correction of spherical aberration may be insufficient. Come. It is more desirable to configure so as to satisfy the following conditional expression.

0.45 <(L _PN / L ₂ ) <0.65
In order to achieve a better balance between monochromatic aberration and chromatic aberration, the curvature of the cemented surface between the negative meniscus lens and the positive meniscus lens of the second group optical system must be the same among all surfaces of the second group optical system. it is not to demand that the largest structure. In the second group optical system, if the curvature of the surface other than the cemented surface is larger than the curvature of the cemented surface, it is difficult to balance axial chromatic aberration and lateral chromatic aberration while correcting the monochromatic aberration well.

In order to correct the monochromatic aberration more satisfactorily, it is desirable that the second group optical system has two or more aspheric surfaces. By using the two aspherical surfaces at locations where light beams pass through differently, the degree of freedom in correcting aberrations can be improved. Incidentally, most for effective aberration correction, it is not to want the most image side surface of the most object-side surface of the second group optical system and aspherical. The most object-side surface of the second group optical system is near the stop, so that the on-axis and off-axis light beams pass almost without separation, and the aspheric surface provided here is mainly used for correcting spherical aberration and coma. Contribute. On the other hand, since the surface closest to the image side of the second group optical system is far from the stop, the on-axis and off-axis light beams are separated to some extent, and the aspheric surface provided here contributes to correction of astigmatism and the like. To do. By using two aspheric surfaces for the most object-side surface and the most image-side surface in this way, each aspheric surface has a sufficiently different effect, and the degree of freedom in correcting aberrations is dramatically increased. It will increase.

Note that the present invention may achieve the intended purpose as one of the following three configurations.
That is, the first group optical system having a negative focal length, the second group optical system having a positive focal length, and the third group optical system having a positive focal length are sequentially arranged from the object side, An aperture that moves integrally with the second group optical system is provided on the object side of the second group optical system, and the first group optical system and the second group are used for zooming from the short focal end to the long focal end. In the zoom lens in which each group moves so that the interval between the group optical systems is reduced and the interval between the second group optical system and the third group optical system is increased, the second group optical system is Consists of three elements in four groups: a positive lens with a large curvature on the object side, a negative meniscus lens with a concave surface on the image side, a positive meniscus lens cemented to the negative meniscus lens, and a positive lens. , it shall be the configuration that satisfies the following condition.

1.40
<((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′)
<2.20
Alternatively, the first group optical system having a negative focal length, the second group optical system having a positive focal length, and the third group optical system having a positive focal length are sequentially arranged from the object side, An aperture that moves integrally with the second group optical system is provided on the object side of the second group optical system, and the first group optical system and the second group are used for zooming from the short focal end to the long focal end. In the zoom lens in which each group moves so that the interval between the group optical systems is reduced and the interval between the second group optical system and the third group optical system is increased, the second group optical system is Consists of three elements in four groups: a positive lens with a large curvature on the object side, a negative meniscus lens with a concave surface on the image side, a positive meniscus lens cemented to the negative meniscus lens, and a positive lens. , it shall be the configuration that satisfies the following condition.

0.40 <(L _PN / L ₂ ) <0.70
Alternatively, the first group optical system having a negative focal length, the second group optical system having a positive focal length, and the third group optical system having a positive focal length are sequentially arranged from the object side, An aperture that moves integrally with the second group optical system is provided on the object side of the second group optical system, and the first group optical system and the second group are used for zooming from the short focal end to the long focal end. In the zoom lens in which each group moves so that the interval between the group optical systems is reduced and the interval between the second group optical system and the third group optical system is increased, the second group optical system is Consists of three elements in four groups: a positive lens with a large curvature on the object side, a negative meniscus lens with a concave surface on the image side, a positive meniscus lens cemented to the negative meniscus lens, and a positive lens. The negative meniscus lens and the positive meniscus lens of the second group optical system Curvature of the cemented surfaces of shall be the largest made structure in all aspects of the second group optical system.
By adopting these respective configurations, it is possible to independently obtain the aberration correction effects as described above.

The feature of the present invention lies in the configuration of the second group optical system as described above. The conditions for performing better aberration correction as a zoom lens will be additionally described below.
In the first group optical system, in order from the object side, at least one negative lens having a large curvature surface facing the image side and at least one positive lens having a large curvature surface facing the object side are arranged. It is desirable that the image side surface of the negative lens be an aspherical surface. Such a configuration of the first group optical system can reduce the curvature of field, and an aspherical surface with a large refraction angle of off-axis rays can be used for distortion particularly at the short focal point. Aberration can be suppressed.

  More specifically, in the first group optical system from the object side to the image side, a negative meniscus lens having a convex surface directed toward the object side, and a negative lens having a large curvature surface directed toward the image side, Three positive lenses having a surface with a large curvature facing the object side may be arranged, and the image side surface of the negative lens may be an aspherical surface. According to such a configuration, the aberration correction capability is further increased, which is advantageous for widening the angle of view.

  The third group optical system is preferably a positive lens having a surface with a large curvature facing the object side, and preferably has at least one aspheric surface. According to such a configuration, off-axis aberrations such as astigmatism can be corrected better while minimizing the thickness of the third group optical system. Further, the third group optical system may be fixed at the time of zooming, but the degree of freedom of aberration correction can be increased by moving the third group optical system by a small amount.

Next, specific examples of the zoom lens, the camera, and the portable information terminal device according to the present invention reflecting the above-described configuration will be described in detail. The first, second, third, fourth, fifth, and sixth examples are examples of the zoom lens according to the present invention, and the seventh example corresponds to the first to sixth examples. 1 is an embodiment of a camera or a portable information terminal device according to the present invention using a zoom lens as shown as an imaging optical system.
In the first to sixth embodiments showing the zoom lens according to the present invention, the configuration of the zoom lens and specific numerical examples thereof are shown. The maximum image height in all the first to sixth embodiments is 4.65 mm. In each of the first to sixth embodiments, the aberration is sufficiently corrected, and it is possible to cope with a light receiving element having 3 to 6 million pixels. It will be apparent from these first to sixth embodiments that by constructing a zoom lens as in the present invention, it is possible to ensure a very good image performance while achieving a sufficiently small size. .

In the description related to the following first to sixth embodiments, the following various symbols are used.
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 ν _d : Abbe number K: Conic constant of aspheric surface A ₄ : Fourth-order aspheric coefficient A ₆ : 6th-order aspheric coefficient A ₈ : 8th-order aspheric coefficient A ₁₀ : 10th-order aspheric coefficient A ₁₂ : 12th-order aspheric coefficient A ₁₄ : 14th-order aspheric coefficient A ₁₆ : 16th-order A ₁₈ : 18th-order aspheric coefficient where the aspherical surface used here is the following when the reciprocal of the paraxial radius of curvature (paraxial curvature) is C and the height from the optical axis is H: It is defined by an expression.

FIG. 1 shows the configuration of an optical system of a zoom lens according to the first embodiment of the present invention.
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 an aperture FA. And an optical filter OF. In this case, the first lens E1 to the third lens E3 constitute the first group optical system G1, the fourth lens E4 to the seventh lens E7 constitute the second group optical system G2, and the eighth lens E8 is The third group optical system G3 is configured and supported by a common support frame or the like that is appropriate for each group, and operates integrally for each group during zooming and the like. FIG. 1 schematically shows the movement trajectory of each group from the short focal length end, which is the wide-angle end, through the intermediate focal length to the long focal length end, which is the telephoto end, so that the zooming operation can also be grasped. Shown with arrows. FIG. 1 also shows the surface numbers of the optical surfaces. In addition, in order to avoid complication of explanation due to an increase in the number of digits of the reference code, each reference code for FIG. 1 is used independently for each embodiment. Therefore, even if a common reference code is attached, This is not a configuration common to the embodiments.

  In FIG. 1, for example, in order from the object side such as a subject, a first lens E1, a second lens E2, a third lens E3, an aperture FA, a fourth lens E4, a fifth lens E5, a sixth lens E6, and a seventh lens. E7, the eighth lens E8 and the optical filter OF are arranged in this order, and an image is formed behind the optical filter OF having various optical filtering functions.

  The first lens E1 is a negative meniscus lens that is convex on the object side, the second lens E2 is a negative meniscus lens that is convex on the object side, and the third lens E3 is a positive lens with a convex surface on the object side. The first group optical system G1 that is a lens (plano-convex lens) and includes the first lens E1 to the third lens E3 exhibits a negative focal length as a whole. The fourth lens E4 is a positive meniscus lens that is convex on the object side, the fifth lens E5 is a negative meniscus lens that is convex on the object side, and the sixth lens E6 is convex on the object side. The positive meniscus lens and the seventh lens E7 are positive lenses (biconvex lenses), and the fifth lens E5 and the sixth lens E6 are cemented together. The second group optical system G2 configured by E7 exhibits a positive focal length as a whole. The eighth lens E8 is a positive meniscus lens convexly formed on the object side, and only the eighth lens E8 forms a third group optical system G3 having a positive focal length. The stop FA disposed on the object side of the second group optical system G2 operates integrally with the second group optical system G2.

  During zooming from the short focus end to the long focus end, the second group optical system G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first group optical system G1 changes the magnification. The third group optical system moves mainly so as to move the exit pupil away from the image plane. More specifically, the distance between the first group optical system G1 and the second group optical system G2 is gradually reduced in accordance with the zooming from the short focal end to the long focal end, and the second group optical system G2 and the third group optical system G3. The optical system of each group is moved so that the interval between the group optical systems G3 is gradually increased.

  In this first embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 5.93 to 16.78 and F = 2.57 to 4.37, respectively, by zooming. , And ω = 39.42 to 15.62. The characteristics of each optical surface are as shown in the following table.

In Table 1, the optical surfaces of the fourth surface, the eighth surface, the fourteenth surface, and the fifteenth surface with an asterisk “*” attached to the surface number are aspheric surfaces, and the parameters of each aspheric surface are as follows.
Aspherical surface: fourth surface K = 0.0, A ₄ = −2.778493 × 10 ⁻⁴ , A ₆ = −4.57252 × 10 ⁻⁶ , A ₈ = 2.85397 × 10 ⁻⁷ , A ₁₀ = -1.90695 × 10 ⁻⁸ , A ₁₂ = 5.07288 × 10 ⁻¹⁰ , A ₁₄ = −1.190194 × 10 ⁻¹² , A ₁₆ = −1.68241 × 10 ⁻¹³ , A ₁₈ = 2.31370 × 10 ^-15
Aspherical surface: Eighth surface K = 0.0, A ₄ = −8.545669 × 10 ⁻⁵ , A ₆ = −3.660180 × 10 ⁻⁷ , A ₈ = −3.63648 × 10 ⁻⁸ , A ₁₀ = 9.613335 × 10 ⁻¹⁰
Aspheric surface: 14th surface K = 0.0, A ₄ = 1.671112 × 10 ⁻⁴ , A ₆ = 6.29478 × 10 ⁻⁶ , A ₈ = −3.996383 × 10 ⁻⁷ , A ₁₀ = 2 14222 × 10 ⁻⁸
Aspherical surface: 15th surface K = 0.0, A ₄ = −1.51122 × 10 ⁻⁵ , A ₆ = 2.994709 × 10 ⁻⁶ , A ₈ = −1.16281 × 10 ⁻⁷ , A ₁₀ = 2.05071 × 10 ⁻⁹
The distance D _A between the first group optical system G1 and the stop FA integrated with the second group optical system G2, the distance D _B between the second group optical system G2 and the third group optical system G3, and The distance D _C between the third group optical system G3 and the optical filter OF is variable, and these variable distances D _{A to} D _C are changed as shown in the following table during zooming.

The numerical values related to the conditional expressions of the present invention described above in the first embodiment are as follows, and are within the range of the conditional expressions.
Conditional expression numerical value (N ₂₂ −N ₂₃ ) = 0.359
(Ν ₂₃ −ν ₂₂ ) = 46.7
((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′) = 1.79
(L _PN / L ₂ ) = 0.589

FIG. 2 shows the configuration of the optical system of the zoom lens according to the second embodiment of the present invention.
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 an aperture FA. And an optical filter OF. In this case, the first lens E1 to the third lens E3 constitute the first group optical system G1, the fourth lens E4 to the seventh lens E7 constitute the second group optical system G2, and the eighth lens E8 is The third group optical system G3 is configured and supported by a common support frame or the like that is appropriate for each group, and operates integrally for each group during zooming and the like. In FIG. 2 also, in order to be able to grasp the zooming operation, the schematic movement trajectory of each group from the short focal length end that is the wide angle end to the long focal length end that is the telephoto end through the intermediate focal length is shown. This is schematically indicated by an arrow. FIG. 2 also shows the surface numbers of the respective optical surfaces. As described above, the reference numerals for FIG. 2 are also used independently of the other embodiments.

  Also in FIG. 2, for example, from the object side such as a subject, the first lens E1, the second lens E2, the third lens E3, the aperture FA, the fourth lens E4, the fifth lens E5, the sixth lens E6, and the seventh lens sequentially. The lens E7, the eighth lens E8, and the optical filter OF are arranged in this order, and an image is formed behind the optical filter OF having various optical filtering functions.

  The first lens E1 is a negative meniscus lens that is convex on the object side, the second lens E2 is a negative meniscus lens that is convex on the object side, and the third lens E3 is a convex surface with a large curvature on the object side. The first group optical system G1 constituted by the first lens E1 to the third lens E3 exhibits a negative focal length as a whole. The fourth lens E4 is a positive meniscus lens that is convex on the object side, the fifth lens E5 is a negative meniscus lens that is convex on the object side, and the sixth lens E6 is convex on the object side. The positive meniscus lens and the seventh lens E7 are positive lenses (biconvex lenses), and the fifth lens E5 and the sixth lens E6 are cemented together. The second group optical system G2 configured by E7 exhibits a positive focal length as a whole. The eighth lens E8 is a positive meniscus lens convexly formed on the object side, and only the eighth lens E8 forms a third group optical system G3 having a positive focal length. The stop FA disposed on the object side of the second group optical system G2 operates integrally with the second group optical system G2.

  During zooming from the short focal end to the long focal end, the second group optical system G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first group optical system G1 is an image accompanying zooming. The third group optical system moves so as to correct the fluctuation of the surface position, and operates mainly to move the exit pupil away from the image plane. More specifically, the distance between the first group optical system G1 and the second group optical system G2 is gradually reduced in accordance with the zooming from the short focal end to the long focal end, and the second group optical system G2 and the third group optical system G3. The optical system of each group is moved so that the interval between the group optical systems G3 is gradually increased.

  In the second embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 5.97 to 16.86 and F = 2.58 to 4.34, respectively, by zooming. And ω = 39.21 to 15.54. The characteristics of each optical surface are as shown in the following table.

In Table 3, the optical surfaces of the fourth surface, the eighth surface, the fourteenth surface, and the fifteenth surface with an asterisk “*” attached to the surface number are aspheric surfaces, and the parameters of each aspheric surface are as follows.
Aspherical surface: fourth surface K = 0.0, A ₄ = −3.66574 × 10 ⁻⁴ , A ₆ = −6.99803 × 10 ⁻⁶ , A ₈ = 3.3139 × 10 ⁻⁷ , A ₁₀ = −2.120223 × 10 ⁻⁸ , A ₁₂ = 4.75955 × 10 ⁻¹⁰ , A ₁₄ = −1.53407 × 10 ⁻¹² , A ₁₆ = −1.261119 × 10 ⁻¹³ , A ₁₈ = 1.33821 × 10 ^-15
Aspherical surface: 8th surface K = 0.0, A ₄ = −8.22942 × 10 ⁻⁵ , A ₆ = −3.449540 × 10 ⁻⁷ , A ₈ = −4.26200 × 10 ⁻⁸ , A ₁₀ = 1.43521 × 10 ⁻⁹
Aspheric surface: 14th surface K = 0.0, A ₄ = 8.62336 × 10 ⁻⁵ , A ₆ = 1.08403 × 10 ⁻⁵ , A ₈ = −1.143432 × 10 ⁻⁶ , A ₁₀ = 5 .55500 × 10 ⁻⁸
Aspheric surface: 15th surface K = 0.0, A ₄ = −1.42708 × 10 ⁻⁵ , A ₆ = 3.1235 × 10 ⁻⁶ , A ₈ = −1.33726 × 10 ⁻⁷ , A ₁₀ = 2.51387 × 10 ⁻⁹
The distance DA between the first group optical system G1 and the aperture stop FA integrated with the second group optical system G2, the distance D _B between the second group optical system G2 and the third group optical system G3, and the first The distance D _C between the third group optical system G3 and the optical filter OF is variable, and these variable distances D _{A to} D _C are changed as shown in the following table during zooming.

The numerical values related to the conditional expressions of the present invention described above in the second embodiment are as follows, and are within the range of the conditional expressions.
Conditional expression numerical value (N ₂₂ −N ₂₃ ) = 0.330
(Ν ₂₃ −ν ₂₂ ) = 40.4
((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′) = 1.73
(L _PN / L ₂ ) = 0.594

FIG. 3 shows the configuration of the optical system of a zoom lens according to the third embodiment of the present invention.
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 an aperture FA. And an optical filter OF. In this case, the first lens E1 to the third lens E3 constitute the first group optical system G1, the fourth lens E4 to the seventh lens E7 constitute the second group optical system G2, and the eighth lens E8 is The third group optical system G3 is configured and supported by a common support frame or the like that is appropriate for each group, and operates integrally for each group during zooming and the like. Also in FIG. 3, in order to grasp the zooming operation, the schematic movement trajectory of each group from the short focal length end which is the wide angle end to the long focal length end which is the telephoto end through the intermediate focal length is shown. This is schematically indicated by an arrow. FIG. 3 also shows the surface numbers of the respective optical surfaces. As described above, the reference numerals for FIG. 3 are also used independently of the other embodiments.

  Also in FIG. 3, for example, from the object side such as the subject, the first lens E1, the second lens E2, the third lens E3, the aperture FA, the fourth lens E4, the fifth lens E5, the sixth lens E6, and the seventh lens sequentially. The lens E7, the eighth lens E8, and the optical filter OF are arranged in this order, and an image is formed behind the optical filter OF that controls various optical filtering functions.

  The first lens E1 is a negative meniscus lens that is convex on the object side, the second lens E2 is a negative meniscus lens that is convex on the object side, and the third lens E3 is a convex surface with a large curvature on the object side. The first group optical system G1 constituted by the first lens E1 to the third lens E3 exhibits a negative focal length as a whole. The fourth lens E4 is a positive meniscus lens that is convex on the object side, the fifth lens E5 is a negative meniscus lens that is convex on the object side, and the sixth lens E6 is convex on the object side. The positive meniscus lens and the seventh lens E7 are positive lenses (biconvex lenses), and the fifth lens E5 and the sixth lens E6 are cemented together. The second group optical system G2 configured by E7 exhibits a positive focal length as a whole. The eighth lens E8 is a positive meniscus lens convexly formed on the object side, and only the eighth lens E8 forms a third group optical system G3 having a positive focal length. The stop FA disposed on the object side of the second group optical system G2 operates integrally with the second group optical system G2.

  During zooming from the short focal end to the long focal end, the second group optical system G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first group optical system G1 is an image accompanying zooming. The third group optical system moves so as to correct the fluctuation of the surface position, and operates mainly to move the exit pupil away from the image plane. More specifically, the distance between the first group optical system G1 and the second group optical system G2 is gradually reduced in accordance with the zooming from the short focal end to the long focal end, and the second group optical system G2 and the third group optical system G3. The optical system of each group is moved so that the interval between the group optical systems G3 is gradually increased.

  In the third embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 5.97 to 16.86 and F = 2.60 to 4.36, respectively, by zooming. And ω = 39.23 to 15.53. The characteristics of each optical surface are as shown in the following table.

In Table 5, the optical surfaces of the fourth surface, the eighth surface, the fourteenth surface, and the fifteenth surface with an asterisk “*” attached to the surface number are aspheric surfaces, and the parameters of each aspheric surface are as follows.
Aspherical surface: 4th surface K = 0.0, A ₄ = −3.774529 × 10 ⁻⁴ , A ₆ = −7.07111 × 10 ⁻⁶ , A ₈ = 3.3080 × 10 ⁻⁷ , A ₁₀ = −2.12578 × 10 ⁻⁸ , A ₁₂ = 4.72698 × 10 ⁻¹⁰ , A ₁₄ = −1.41429 × 10 ⁻¹² , A ₁₆ = −1.23287 × 10 ⁻¹³ , A ₁₈ = 1.226129 × 10 ^-15
Aspheric surface: 8th surface K = 0.0, A ₄ = −9.272221 × 10 ⁻⁵ , A ₆ = −2.000691 × 10 ⁻⁷ , A ₈ = −5.999813 × 10 ⁻⁸ , A ₁₀ = 1.95311 × 10 ⁻⁹
Aspheric surface: 14th surface K = 0.0, A ₄ = 1.17533 × 10 ⁻⁴ , A ₆ = 1.28941 × 10 ⁻⁵ , A ₈ = −1.26885 × 10 ⁻⁶ , A ₁₀ = 6 .09645 × 10 ⁻⁸
Aspheric surface: 15th surface K = 0.0, A ₄ = −1.91397 × 10 ⁻⁵ , A ₆ = 3.80313 × 10 ⁻⁶ , A ₈ = −1.67517 × 10 ⁻⁷ , A ₁₀ = 3.09028 × 10 ⁻⁹
The distance D _A between the first group optical system G1 and the stop FA integrated with the second group optical system G2, the distance D _B between the second group optical system G2 and the third group optical system G3, and The distance D _C between the third group optical system G3 and the optical filter OF is variable, and these variable distances D _{A to} D _C are changed as shown in the following table during zooming.

Further, the numerical values related to the conditional expressions of the present invention described above in the third embodiment are as follows, and are within the range of the conditional expressions.
Conditional expression numerical value (N ₂₂ −N ₂₃ ) = 0.288
(Ν ₂₃ −ν ₂₂ ) = 35.7
((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′) = 1.66
(L _PN / L ₂ ) = 0.590

FIG. 4 shows the configuration of the optical system of the zoom lens according to the fourth embodiment of the present invention.
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 an aperture FA. And an optical filter OF. In this case, the first lens E1 to the third lens E3 constitute the first group optical system G1, the fourth lens E4 to the seventh lens E7 constitute the second group optical system G2, and the eighth lens E8 is The third group optical system G3 is configured and supported by a common support frame or the like that is appropriate for each group, and operates integrally for each group during zooming and the like. Also in FIG. 4, in order to be able to grasp the zooming operation, the schematic movement trajectory of each group from the short focal length end that is the wide angle end to the long focal length end that is the telephoto end through the intermediate focal length is shown. This is schematically indicated by an arrow. FIG. 4 also shows the surface numbers of the respective optical surfaces. As described above, the reference numerals for FIG. 4 are also used independently of the other embodiments.

  Also in FIG. 4, for example, from the object side such as the subject, the first lens E1, the second lens E2, the third lens E3, the aperture FA, the fourth lens E4, the fifth lens E5, the sixth lens E6, and the seventh lens sequentially. The lens E7, the eighth lens E8, and the optical filter OF are arranged in this order, and an image is formed behind the optical filter OF having various optical filtering functions.

  The first lens E1 is a negative meniscus lens that is convex on the object side, the second lens E2 is a negative meniscus lens that is convex on the object side, and the third lens E3 is convex on the object side. The first group optical system G1 that is a positive meniscus lens and includes the first lens E1 to the third lens E3 exhibits a negative focal length as a whole. The fourth lens E4 is a positive meniscus lens that is convex on the object side, the fifth lens E5 is a negative meniscus lens that is convex on the object side, and the sixth lens E6 is convex on the object side. The positive meniscus lens and the seventh lens E7 are positive lenses (biconvex lenses), and the fifth lens E5 and the sixth lens E6 are cemented together. The second group optical system G2 configured by E7 exhibits a positive focal length as a whole. The eighth lens E8 is a positive meniscus lens convexly formed on the object side, and only the eighth lens E8 forms a third group optical system G3 having a positive focal length. The stop FA disposed on the object side of the second group optical system G2 operates integrally with the second group optical system G2.

  During zooming from the short focal end to the long focal end, the second group optical system G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first group optical system G1 is an image accompanying zooming. The third group optical system moves so as to correct the fluctuation of the surface position, and operates mainly to move the exit pupil away from the image plane. More specifically, the distance between the first group optical system G1 and the second group optical system G2 is gradually reduced in accordance with the zooming from the short focal end to the long focal end, and the second group optical system G2 and the third group optical system G3. The optical system of each group is moved so that the interval between the group optical systems G3 is gradually increased.

  In the fourth embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 5.97 to 16.88 and F = 2.68 to 4.42 by zooming, respectively. , And ω = 39.20 to 15.52. The characteristics of each optical surface are as shown in the following table.

In Table 7, the optical surfaces of the fourth surface, the eighth surface, the fourteenth surface, and the fifteenth surface with an asterisk “*” attached to the surface number are aspheric surfaces, and the parameters of each aspheric surface are as follows.
Aspherical surface: 4th surface K = 0.0, A ₄ = −3.502 130 × 10 ⁻⁴ , A ₆ = −8.445461 × 10 ⁻⁶ , A ₈ = 3.887166 × 10 ⁻⁷ , A ₁₀ = -2.37791 × 10 ⁻⁸ , A ₁₂ = 4.886388 × 10 ⁻¹⁰ , A ₁₄ = −3.779112 × 10 ⁻¹³ , A ₁₆ = −1.52048 × 10 ⁻¹³ , A ₁₈ = 1.32883 × 10 ^-15
Aspherical surface: Eighth surface K = 0.0, A ₄ = −9.80638 × 10 ⁻⁵ , A ₆ = −3.447779 × 10 ⁻⁷ , A ₈ = −4.447522 × 10 ⁻⁸ , A ₁₀ = −8.37430 × 10 ⁻¹⁰
Aspheric surface: 14th surface K = 0.0, A ₄ = 1.83538 × 10 ⁻⁴ , A ₆ = 6.09812 × 10 ⁻⁷ , A ₈ = 3.772360 × 10 ⁻⁷ , A ₁₀ = −1 70939 × 10 ⁻⁸
Aspherical surface: 15th surface K = 0.0, A ₄ = −4.21513 × 10 ⁻⁵ , A ₆ = 2.95957 × 10 ⁻⁶ , A ₈ = −1.23500 × 10 ⁻⁷ , A ₁₀ = 2.32351 × 10 ⁻⁹
The distance D _A between the first group optical system G1 and the stop FA integrated with the second group optical system G2, the distance D _B between the second group optical system G2 and the third group optical system G3, and The distance D _C between the third group optical system G3 and the optical filter OF is variable, and these variable distances D _{A to} D _C are changed as shown in the following table during zooming.

The numerical values related to the conditional expressions of the present invention described above in the fourth embodiment are as follows, and are within the range of the conditional expressions.
Conditional expression numerical value (N ₂₂ −N ₂₃ ) = 0.359
(Ν ₂₃ −ν ₂₂ ) = 46.7
((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′) = 1.94
(L _PN / L ₂ ) = 0.556

FIG. 5 shows the configuration of an optical system of a zoom lens according to the fifth embodiment of the present invention.
The zoom lens shown in FIG. 5 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, a ninth lens. A lens E9, an aperture FA, and an optical filter OF are provided. In this case, the first lens E1 to the fourth lens E4 constitute the first group optical system G1, the fifth lens E5 to the eighth lens E8 constitute the second group optical system G2, and the ninth lens E9 The third group optical system G3 is configured and supported by a common support frame or the like that is appropriate for each group, and operates integrally for each group during zooming and the like. Also in FIG. 5, in order to be able to grasp the zooming operation, the schematic movement trajectory of each group from the short focal length end that is the wide angle end to the long focal length end that is the telephoto end through the intermediate focal length is shown. This is schematically indicated by an arrow. FIG. 5 also shows the surface numbers of the optical surfaces. As described above, the reference numerals for FIG. 5 are also used independently of the other embodiments.

  Also in FIG. 5, for example, from the object side such as a subject, the first lens E1, the second lens E2, the third lens E3, the fourth lens E4, the aperture FA, the fifth lens E5, the sixth lens E6, and the seventh lens sequentially. The lens E7, the eighth lens E8, the ninth lens E9, and the optical filter OF are arranged in this order, and an image is formed behind the optical filter OF having various optical filtering functions.

  The first lens E1 is a negative meniscus lens that is convex on the object side, the second lens E2 is a negative meniscus lens that is convex on the object side, and the third lens E3 has a convex surface with a large curvature on the object side. The positive lens (biconvex lens) and the fourth lens E4 are negative lenses (biconcave lenses), and the third lens E3 and the fourth lens E4 are cemented, and the first lens of the three-group four-lens configuration The first group optical system G1 including the E1 to fourth lenses E4 exhibits a negative focal length as a whole. The fifth lens E5 is a positive meniscus lens that is convex on the object side, the sixth lens E6 is a negative meniscus lens that is convex on the object side, and the seventh lens E7 is convex on the object side. The positive meniscus lens and the eighth lens E8 are positive lenses (biconvex lenses), and the sixth lens E6 and the seventh lens E7 are cemented together. The second group optical system G2 configured by E8 exhibits a positive focal length as a whole. The ninth lens E9 is a positive lens (biconvex lens) having a convex surface with a large curvature toward the object side. The third lens optical system G3 having a positive focal length is configured only by the ninth lens E9. . The stop FA disposed on the object side of the second group optical system G2 operates integrally with the second group optical system G2.

  During zooming from the short focal end to the long focal end, the second group optical system G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first group optical system G1 is an image accompanying zooming. The third group optical system moves so as to correct the fluctuation of the surface position, and operates mainly to move the exit pupil away from the image plane. More specifically, the distance between the first group optical system G1 and the second group optical system G2 is gradually reduced in accordance with the zooming from the short focal end to the long focal end, and the second group optical system G2 and the third group optical system G3. The optical system of each group is moved so that the interval between the group optical systems G3 is gradually increased.

  In the fifth embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 5.98 to 16.89 and F = 2.62 to 4.51 by zooming, respectively. And ω = 39.18 to 15.52. The characteristics of each optical surface are as shown in the following table.

In Table 9, the optical surfaces of the fourth surface, the ninth surface, the fifteenth surface, and the sixteenth surface with an asterisk “*” attached to the surface number are aspheric surfaces, and the parameters of each aspheric surface are as follows.
Aspherical surface: 4th surface K = 0.0, A ₄ = −3.119923 × 10 ⁻⁴ , A ₆ = −7.449996 × 10 ⁻⁶ , A ₈ = 3.11483 × 10 ⁻⁷ , A ₁₀ = -1.94211 × 10 ⁻⁸ , A ₁₂ = 3.991258 × 10 ⁻¹⁰ , A ₁₄ = −2.01103 × 10 ⁻¹² , A ₁₆ = −5.49008 × 10 ⁻¹⁴ , A ₁₈ = 3.18700 × 10 ^-16
Aspheric surface: 9th surface K = 0.0, A ₄ = −9.62105 × 10 ⁻⁵ , A ₆ = −9.778873 × 10 ⁻⁷ , A ₈ = 1.62625 × 10 ⁻⁸ , A ₁₀ = −8.46903 × 10 ⁻¹⁰
Aspherical surface: 15th surface K = 0.0, A ₄ = 1.62639 × 10 ⁻⁴ , A ₆ = 2.90705 × 10 ⁻⁵ , A ₈ = −3.6616 × 10 ⁻⁶ , A ₁₀ = 2 .00067 × 10 ⁻⁷
Aspheric surface: 16th surface K = 0.0, A ₄ = −1.57048 × 10 ⁻⁵ , A ₆ = 5.243326 × 10 ⁻⁶ , A ₈ = −2.39620 × 10 ⁻⁷ , A ₁₀ = 4.62003 × 10 ⁻⁹
The distance D _A between the first group optical system G1 and the stop FA integrated with the second group optical system G2, the distance D _B between the second group optical system G2 and the third group optical system G3, and The distance D _C between the third group optical system G3 and the optical filter OF is variable, and these variable distances D _{A to} D _C are changed as shown in the following table during zooming.

Further, the numerical values relating to the conditional expressions of the present invention described above in the fifth embodiment are as follows, and are within the range of the conditional expressions.
Conditional expression numerical value (N ₂₂ −N ₂₃ ) = 0.208
(Ν ₂₃ −ν ₂₂ ) = 31.7
((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′) = 1.86
(L _PN / L ₂ ) = 0.498

FIG. 6 shows the configuration of an optical system of a zoom lens according to the sixth embodiment of the present invention.
The zoom lens shown in FIG. 6 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, a ninth lens. A lens E9, an aperture FA, and an optical filter OF are provided. In this case, the first lens E1 to the fourth lens E4 constitute the first group optical system G1, the fifth lens E5 to the eighth lens E8 constitute the second group optical system G2, and the ninth lens E9 The third group optical system G3 is configured and supported by a common support frame or the like that is appropriate for each group, and operates integrally for each group during zooming and the like. Also in FIG. 5, in order to be able to grasp the zooming operation, the schematic movement trajectory of each group from the short focal length end that is the wide angle end to the long focal length end that is the telephoto end through the intermediate focal length is shown. This is schematically indicated by an arrow. FIG. 6 also shows the surface numbers of the respective optical surfaces. As described above, the reference numerals for FIG. 6 are also used independently of the other embodiments.

  Also in FIG. 6, for example, from the object side such as a subject, the first lens E1, the second lens E2, the third lens E3, the fourth lens E4, the aperture FA, the fifth lens E5, the sixth lens E6, and the seventh lens are sequentially arranged. The lens E7, the eighth lens E8, the ninth lens E9, and the optical filter OF are arranged in this order, and an image is formed behind the optical filter OF having various optical filtering functions.

  The first lens E1 is a negative meniscus lens that is convex on the object side, the second lens E2 is a negative meniscus lens that is convex on the object side, and the third lens E3 is convex on the object side. The negative meniscus lens and the fourth lens E4 are positive meniscus lenses formed convex on the object side, and the first group optical system G1 configured by the first lens E1 to the fourth lens E4 having a four-group four-lens configuration. Exhibits a negative focal length as a whole. The fifth lens E5 is a positive meniscus lens that is convex on the object side, the sixth lens E6 is a negative meniscus lens that is convex on the object side, and the seventh lens E7 is convex on the object side. The positive meniscus lens and the eighth lens E8 are positive lenses (biconvex lenses), and the sixth lens E6 and the seventh lens E7 are cemented together. The second group optical system G2 configured by E8 exhibits a positive focal length as a whole. The ninth lens E9 is a positive meniscus lens convexly formed on the object side, and the third lens optical system G3 having a positive focal length is configured only by the ninth lens E9. The stop FA disposed on the object side of the second group optical system G2 operates integrally with the second group optical system G2.

  During zooming from the short focal end to the long focal end, the second group optical system G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first group optical system G1 is an image accompanying zooming. The third group optical system moves so as to correct the fluctuation of the surface position, and operates mainly to move the exit pupil away from the image plane. More specifically, the distance between the first group optical system G1 and the second group optical system G2 is gradually reduced in accordance with the zooming from the short focal end to the long focal end, and the second group optical system G2 and the third group optical system G3. The optical system of each group is moved so that the interval between the group optical systems G3 is gradually increased.

  In the sixth embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 5.97-16.88 and F = 2.63-4. 45 and ω = 39.20 to 15.52. The characteristics of each optical surface are as shown in the following table.

In Table 9, the sixth, tenth, sixteenth, and seventeenth optical surfaces with an asterisk “*” in the surface number are aspheric surfaces, and the parameters of each aspheric surface are as follows.
Aspheric surface: 6th surface K = 0.0, A ₄ = −3.77707 × 10 ⁻⁴ , A ₆ = −7.57114 × 10 ⁻⁶ , A ₈ = 3.224559 × 10 ⁻⁷ , A ₁₀ = −2.06841 × 10 ⁻⁸ , A ₁₂ = 4.43898 × 10 ⁻¹⁰ , A ₁₄ = −1.72365 × 10 ⁻¹² , A ₁₆ = −9.21688 × 10 ⁻¹⁴ , A ₁₈ = 7.66062 × 10 ^-16
Aspherical surface: 10th surface K = 0.0, A ₄ = −9.000752 × 10 ⁻⁵ , A ₆ = 3.09052 × 10 ⁻⁸ , A ₈ = −7.156556 × 10 ⁻⁸ , A ₁₀ = 2.25617 × 10 ⁻⁹
Aspherical surface: 16th surface K = 0.0, A ₄ = 1.02677 × 10 ⁻⁴ , A ₆ = 1.82551 × 10 ⁻⁵ , A ₈ = −1.97083 × 10 −6, A ₁₀ = 9 .81276 × 10−8
Aspherical surface: 17th surface K = 0.0, A ₄ = −1.59462 × 10 ⁻⁵ , A ₆ = 4.762213 × 10 ⁻⁶ , A ₈ = −2.249929 × 10 ⁻⁷ , A ₁₀ = 4.30948 × 10 ⁻⁹
The distance D _A between the first group optical system G1 and the stop FA integrated with the second group optical system G2, the distance D _B between the second group optical system G2 and the third group optical system G3, and The distance D _C between the third group optical system G3 and the optical filter OF is variable, and the variable distance D _A D _C is changed as shown in the following table during zooming.

The numerical values related to the conditional expressions of the present invention described above in the sixth embodiment are as follows, and are within the range of the conditional expressions.
Conditional expression numerical value (N ₂₂ −N ₂₃ ) = 0.258
(Ν ₂₃ −ν ₂₂ ) = 37.5
((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′) = 1.80
(L _PN / L ₂ ) = 0.538
7 to 9 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration in the zoom lens shown in FIG. 1 according to the first embodiment described above. FIG. FIG. 8 is an aberration curve diagram at the intermediate focal length, and FIG. 9 is an aberration curve diagram at the long focal 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, and the broken line represents meridional.
10 to 12 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration in the zoom lens shown in FIG. 2 according to the second embodiment described above, and FIG. FIG. 11 is an aberration curve diagram at the intermediate focal length, and FIG. 12 is an aberration curve diagram at the long focal end. In this case as well, 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 the sagittal, and the broken line represents the meridional.

FIGS. 13 to 15 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration in the zoom lens shown in FIG. 3 according to the third embodiment described above. FIG. 14 is an aberration curve diagram at the intermediate focal length, and FIG. 15 is an aberration curve diagram at the long focal end. In this case as well, 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 the sagittal, and the broken line represents the meridional.
FIGS. 16 to 18 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration in the zoom lens shown in FIG. 4 according to the fourth embodiment described above. FIG. 17 is an aberration curve diagram at the intermediate focal length, and FIG. 18 is an aberration curve diagram at the long focal end. In this case as well, 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 the sagittal, and the broken line represents the meridional.
FIGS. 19 to 21 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration in the zoom lens shown in FIG. 5 according to the fifth embodiment described above. FIG. FIG. 20 is an aberration curve diagram at the intermediate focal length, and FIG. 21 is an aberration curve diagram at the long focal end. In this case as well, 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 the sagittal, and the broken line represents the meridional.
22 to 24 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration in the zoom lens shown in FIG. 6 according to the sixth embodiment described above, and FIG. FIG. 23 is an aberration curve diagram at the intermediate focal length, and FIG. 24 is an aberration curve diagram at the long focal end. In this case as well, 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 the sagittal, and the broken line represents the meridional.
According to the aberration curve diagrams of FIGS. 7 to 24, according to the zoom lens having the configuration shown in FIGS. 1 to 6 according to the first to sixth embodiments of the present invention described above, all aberrations are It can be seen that it is corrected or suppressed well.

  Next, FIGS. 25 to 25 show a seventh embodiment of the present invention in which a zoom lens according to the present invention as shown in the first to sixth embodiments described above is employed as a photographing optical system. This will be described with reference to FIG. FIG. 25 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. 26 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. 25 and 26, 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. 27, 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 photographic lens 101 and a light receiving element 201 as an area sensor such as a CCD (charge coupled device) imaging device, and is an object to be photographed, that is, a subject formed by the photographic lens 101 that is a photographing optical system. The image is read by the light receiving element 201. As the photographing lens 101, a zoom lens according to the present invention (that is, defined in claims 1 to 5 ) as described in the first to sixth embodiments is used (claims 6 and 7 ). Corresponding to).

  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 photographed, or can 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. 25A. 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, for example, at the short focal end. By operating the zoom lever 103, the optical systems of the respective groups of optical systems are arranged. The arrangement can be changed, and the zooming operation to the long focal end can be performed. Preferably, the viewfinder 104 is also scaled in conjunction with a change in the angle of view of the taking lens 101.
In many cases, focusing is performed by half-pressing the shutter button 102. Focusing in the zoom lens composed of three negative-positive-positive groups as shown in the first to sixth embodiments described above is performed by moving the first group optical system G1 or the third group optical system G3. Alternatively, it can be performed by moving the light receiving element 201. 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.
As described above, the zoom lens as shown in the first to sixth embodiments can be used as the photographing optical system for the camera or the portable information terminal device as described above. Therefore, it is possible to achieve a small camera or portable information terminal device with high image quality using a light receiving element of 3 to 6 million pixel class.

Based on the above-described embodiments, the present invention is arranged corresponding to each claim. The zoom lens according to claim 1 of the present invention comprises:
A first group optical system having a negative focal length, a second group optical system having a positive focal length, and a third group optical system having a positive focal length are sequentially arranged from the object side, and A diaphragm that moves integrally with the second group optical system on the object side of the second group optical system;
Upon zooming from the short focal end to the long focal end, the distance between the first group optical system and the second group optical system is gradually reduced, and the distance between the second group optical system and the third group optical system is reduced. In the zoom lens in which the first group optical system to the third group optical system are moved so that is gradually increased,
The second group optical system includes, in order from the object side, a positive lens having a large curvature surface facing the object side, a negative meniscus lens having a concave surface facing the image side, a positive meniscus lens cemented to the negative meniscus lens, and It consists of an optical system with 3 groups and 4 elements in which positive lenses are arranged.

Then, the distance from the vertex of the object side surface of the positive lens closest to the object side of the second group optical system to the vertex of the junction surface between the negative meniscus lens and the positive meniscus lens of the second group optical system is expressed as L _PN , the thickness of the optical axis direction of the second group optical system as L _2,
Conditional expression:
0.40 <(L _PN / L ₂ ) <0.70
Satisfied.
According to the first aspect, a and wide angle of view at a sufficiently small, yet a high-performance, spherical aberration, good astigmatism and coma aberration correcting the 3 million to 6 million pixels imaging as possible out to realize a zoom lens having a resolution corresponding to the element.

The zoom lens according to claim 2 of the present invention is
The zoom lens according to claim 1.
In the second group optical system, the Abbe number of the negative meniscus lens is ν ₂₂ , and the Abbe number of the positive meniscus lens joined to the negative meniscus lens is ν ₂₃ ,
Conditional expression:
25 <(ν ₂₃ −ν ₂₂ ) <50
Satisfied.

  According to the configuration of the second aspect, it is possible to provide a high-performance zoom lens in which chromatic aberration is corrected more satisfactorily, and as a result, it is possible to realize a camera or a portable information terminal device with higher image quality.

The zoom lens according to claim 3 of the present invention is
The zoom lens according to claim 1 or 2,
The radius of curvature of the object side surface of the most object side positive lens in the second group optical system is r _21F , the radius of curvature of the object side surface of the negative meniscus lens in the second group optical system is r _22F , and the second group optical system. _{Where the} radius of curvature of the cemented surface between the negative meniscus lens and the positive meniscus lens is r _22R and the maximum image height is Y ′.
Conditional expression:
1.40
<((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′)
<2.20
Satisfied.

  According to the configuration of the third aspect, it is possible to provide a high-performance zoom lens that mainly corrects the field curvature more favorably. As a result, there is little deterioration in image quality around the screen, and a higher-quality camera or mobile phone. An information terminal device can be realized.

The zoom lens according to claim 4 of the present invention is:
In the zoom lens according to any one of claims 1 to 3 ,
The curvature of the cemented surface between the negative meniscus lens and the positive meniscus lens of the second group optical system is the largest among all the surfaces of the second group optical system.

According to the configuration of claim 4 , it is possible to provide a high-performance zoom lens in which monochromatic aberration and chromatic aberration are balanced, and as a result, a high-quality camera or portable information with little color blur at the periphery of the screen. A terminal device can be realized.

A zoom lens according to claim 5 of the present invention comprises:
The zoom lens according to claim 3 or 4 ,
The most object side surface and the most image side surface of the second group optical system are aspherical surfaces.

According to the configuration of claim 5 , it is possible to provide a higher-performance zoom lens that mainly corrects monochromatic aberration more favorably, so that a higher-quality camera or portable information terminal device is realized over the entire screen. Can do.

A camera according to a sixth aspect of the present invention includes the zoom lens according to any one of the first to fifth aspects as a photographing optical system.

According to the configuration of the sixth aspect , a zoom lens having a sufficiently small size, a wide angle of view, a high performance, and a resolving power corresponding to an image sensor with 3 to 6 million pixels is used as a photographing optical system. Thus, a small camera with a wide angle of view and a high image quality can be provided. As a result, the user can take a high-quality image with a camera having excellent portability.
A portable information terminal device according to a seventh aspect of the present invention includes the zoom lens according to any one of the first to fifth aspects as a photographing optical system of a camera function unit.

According to the configuration of the seventh aspect , a zoom lens having a sufficiently small size, a wide angle of view, a high performance, and a resolving power corresponding to an image sensor of 3 to 6 million pixels is photographed by the camera function unit. use as an optical system, compact and can provide high quality portable information terminal device, so that the user photographed a high-quality image in a portable information terminal apparatus having excellent portability, outside the image Can be sent to.

1 is a cross-sectional view along an optical axis schematically showing the configuration of an optical system of a zoom lens according to a first example of the present invention. FIG. 6 is a cross-sectional view along the optical axis schematically showing the configuration of an optical system of a zoom lens according to a second example of the present invention. FIG. 6 is a cross-sectional view along an optical axis schematically showing the configuration of an optical system of a zoom lens according to a third example of the present invention. FIG. 6 is a cross-sectional view taken along an optical axis schematically showing a configuration of an optical system of a zoom lens according to a fourth example of the present invention. FIG. 7 is a cross-sectional view along an optical axis schematically showing the configuration of an optical system of a zoom lens according to Example 5 of the present invention. FIG. 10 is a cross-sectional view along the optical axis schematically showing the configuration of an optical system of a zoom lens according to Example 6 of the present invention. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the short focal end of the zoom lens according to the first embodiment 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 the first embodiment 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 long focal end of the zoom lens according to the first embodiment 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 short focal end of the zoom lens according to the second embodiment of the present invention shown in FIG. 2. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration and coma aberration at the intermediate focal length of the zoom lens according to the second embodiment 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 long focal end of the zoom lens according to the second embodiment of the present invention shown in FIG. 2. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration and coma aberration at the short focal point of the zoom lens according to the third embodiment 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 the third embodiment of the present invention shown in FIG. 3. FIG. 7 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end of the zoom lens according to the third embodiment 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 short focal point of the zoom lens according to the fourth embodiment 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 intermediate focal length of the zoom lens according to the fourth embodiment 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 long focal end of the zoom lens according to the fourth embodiment of the present invention shown in FIG. 4. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration and coma aberration at the short focal point of the zoom lens according to the fifth embodiment of the present invention shown in FIG. 5. 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 the fifth embodiment of the present invention shown in FIG. 5. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end of the zoom lens according to the fifth embodiment of the present invention shown in FIG. 5. FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the short focal end of the zoom lens according to the sixth example of the present invention shown in FIG. 6. FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to the sixth example of the present invention shown in FIG. 6. FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end of the zoom lens according to the sixth example of the present invention shown in FIG. 6. It is the perspective view seen from the object side which shows typically the appearance composition of the camera concerning the 7th example of the present invention, and (a) is the state where the photographic lens is retracted in the camera body, (b ) Shows a state in which the taking lens protrudes from the body of the camera. It is the perspective view seen from the photographer side which shows typically the external appearance structure of the camera of FIG. FIG. 26 is a block diagram schematically illustrating a functional configuration of the camera in FIG. 25.

Explanation of symbols

G1 First group optical system G2 Second group optical system G3 Third group optical system E1 to E9 Lens FA Aperture OF Various optical filters 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 device 203 Image processing device 204 Central processing unit (CPU)
205 Semiconductor memory 206 Communication card, etc.

Claims (7)

A first group optical system having a negative focal length, a second group optical system having a positive focal length, and a third group optical system having a positive focal length are sequentially disposed from the object side, and A diaphragm that moves integrally with the second group optical system on the object side of the second group optical system;
Upon zooming from the short focal end to the long focal end, the distance between the first group optical system and the second group optical system is gradually reduced, and the distance between the second group optical system and the third group optical system is reduced. In the zoom lens in which the first group optical system to the third group optical system are moved so that is gradually increased,
The second group optical system includes, in order from the object side, a positive lens having a large curvature surface facing the object side, a negative meniscus lens having a concave surface facing the image side, a positive meniscus lens cemented to the negative meniscus lens, and It consists of an optical system with 3 groups and 4 elements in which positive lenses are arranged.
A distance from the vertex of the object side surface of the positive lens closest to the object side of the second group optical system to the vertex of the cemented surface of the negative meniscus lens and the positive meniscus lens of the second group optical system is expressed as L _PN , the thickness of the optical axis direction of the second group optical system as L _2,
Conditional expression:
0.40 <(L _PN / L ₂ ) <0.70
A zoom lens characterized by satisfying In the second group optical system, the Abbe number of the negative meniscus lens is ν ₂₂ , and the Abbe number of the positive meniscus lens joined to the negative meniscus lens is ν ₂₃ ,
Conditional expression:
25 <(ν ₂₃ −ν ₂₂ ) <50
The zoom lens according to claim 1, wherein: The radius of curvature of the object side surface of the most object side positive lens in the second group optical system is r _21F , the radius of curvature of the object side surface of the negative meniscus lens in the second group optical system is r _22F , and the second group optical system. _{Where the} radius of curvature of the cemented surface between the negative meniscus lens and the positive meniscus lens is r _22R and the maximum image height is Y ′.
Conditional expression:
1.40
<((1 / r _21F ) + (1 / r _22F ) + (1 / r _22R )) × Y ′)
<2.20
The zoom lens according to claim 1, wherein the zoom lens satisfies the following. The curvature of the cemented surface between the negative meniscus lens and the positive meniscus lens of the second group optical system is the largest among all the surfaces of the second group optical system. any zoom lens according to one of the 3. The zoom lens according to claim 3 or claim 4, wherein the most image side surface of the most object-side surface of the second group optical system is an aspherical surface. A camera comprising the zoom lens according to any one of claims 1 to 5 as a photographing optical system. A portable information terminal device comprising the zoom lens according to any one of claims 1 to 5 as a photographing optical system of a camera function unit.

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