JP2012163678A - Zoom lens, camera, and portable information terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens having a sufficiently wide angle with a half angle of view at a wide angle end of 38° or more, and a variable power ratio of 10 times or more, configured of relatively few 9 lenses, and having a resolution accommodating an image pickup device of 10,000,000-15,000,000 pixels with a compact size.SOLUTION: A zoom lens is formed by arranging, in order from an object, a first lens group G1 having a positive refractive power; a second lens group G2 having a negative refractive power; a third lens group G3 having a positive refractive power; and a fourth lens group G4 having a positive refractive power. The zoom lens further includes an aperture diaphragm AD that is disposed between the second lens group G2 and the third lens group G3 and, when varying a power, independently moves in an optical axis direction, and satisfies the following conditional expression (1): 1.0<L/|f12w|<2.5, where Lis an interval between the second lens group and the third lens group at the wide angle end, and f12w is a composite focal distance between the first lens group and the second lens group at the wide angle end.

Description

  The present invention relates to a zoom lens improved as a photographing optical system, a camera having the zoom lens as a photographing optical system, and a portable information terminal device.

In recent years, the market for digital cameras has become very large, and user demands for digital cameras are also diverse. In particular, high image quality and miniaturization are always desired by users, and the weight is large. Therefore, a zoom lens used as a photographing lens is also required to have both high performance and downsizing.
Here, in terms of miniaturization, it is first necessary to shorten the total lens length (distance from the lens surface closest to the object side to the image plane) during use, and reduce the thickness of each lens group. It is also important to reduce the overall length during storage. Furthermore, in terms of high performance, it is necessary to have at least a resolving power corresponding to an image sensor with 10 to 15 million pixels over the entire zoom range.
In addition, there are many users who wish to widen the angle of view of the photographic lens, and the half angle of view at the wide angle end of the zoom lens is 38 degrees or more equivalent to 28 mm in terms of the focal length in terms of a 35 mm silver salt camera (so-called Leica version). Is desirable.
Furthermore, it is desired that the zoom ratio is as large as possible. A zoom lens with a focal length equivalent to 28 to 200 mm (about 7.1 times) with a focal length equivalent to 35 mm silver-salt camera is considered to be able to cope with most general photography, but converted to 35 mm silver-salt camera The number of users who desire a focal length of about 28 to 300 mm (about 10.7 times) is increasing.

There are many types of zoom lenses for digital cameras, but as a type suitable for high zoom ratio, in order from the object side, a first lens group having a positive focal length and a second lens having a negative focal length. A lens group, a third lens group having a positive focal length, and a fourth lens group having a positive focal length, and at the time of zooming from the wide-angle end to the telephoto end, the first lens group and the second lens group In some cases, the distance increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group changes.
As a conventional example of this type of zoom lens, there is a type in which the first group is fixed at the time of zooming, or the first group is reciprocated in a convex arc shape on the image side. If a large amount of movement of the second lens group is to be secured, the diaphragm disposed in the vicinity of the third lens group will be separated from the first lens group even at the wide-angle end, so that a wide angle and a high zoom ratio are achieved. The first lens group becomes very large. Therefore, in order to realize a wide-angle, high-magnification, and compact zoom lens, it is desirable that the first lens unit be moved so that it is positioned closer to the object side at the telephoto end than at the wide-angle end. By making the total lens length at the wide angle end shorter than that at the telephoto end, it is possible to sufficiently widen the angle while suppressing an increase in size of the first lens group.

Furthermore, the thickness of the first lens group is reduced by configuring the first lens group with two, which is the minimum required number for correcting chromatic aberration, and between the second lens group and the third lens group. By suppressing the height of off-axis light passing through the first lens group by disposing the aperture stop at an appropriate position, a sufficiently wide angle and a high angle can be achieved while suppressing an increase in the diameter of the first lens group. A zoom ratio can be achieved.
In order from the object side, the first lens group having a negative refractive power and a positive lens having a convex surface on the object side as a whole has a positive refractive power, a second lens group having a negative refractive power, and a first lens group having a positive refractive power. Three lens groups and a fourth lens group having a positive refractive power are arranged, and the distance between the first lens group and the second lens group is increased upon zooming from the wide-angle end to the telephoto end. In the zoom lens in which the distance between the third lens group and the third lens group is reduced and the distance between the third lens group and the fourth lens group is changed, the optical axis direction is changed between the second lens group and the third lens group during zooming. The invention according to Patent Document 1 (Japanese Patent Laid-Open No. 2008-203453), Patent Document 2 (Japanese Patent Laid-Open No. 2005-326743), which was previously proposed by the present applicant as having an independently movable aperture stop. Patent Document 3 (Japanese Patent Laid-Open No. 2001-318312) Publications) and the like.
However, in any of the embodiments described in Patent Documents 1 to 3, the zoom ratio is not so large as 3 to 4.5, and the total length of the telephoto end compared to the zoom ratio and when stored. It is hard to say that the total length is short enough.

The present invention has been made in view of the above-described circumstances, and the invention according to claim 1 is capable of zooming by 10 times or more while the half angle of view at the wide angle end is sufficiently wide as 38 degrees or more. An object of the present invention is to provide a zoom lens that has a ratio and a small number of components, such as nine, is small, and has a resolving power corresponding to an image sensor with 10 to 15 million pixels.
The invention according to claim 2 has a zoom ratio of 10 times or more while the half angle of view at the wide angle end is sufficiently wide as 38 degrees or more, and the number of components is as small as about nine, It is another object of the present invention to provide a zoom lens having a resolving power corresponding to an image sensor having a size of 10 million to 15 million pixels.
An object of the present invention is to provide a high-performance zoom lens in which chromatic aberration is favorably corrected.
The invention according to claim 4 has a zoom ratio of 10 times or more while the half angle of view at the wide-angle end is a sufficiently wide angle of 38 degrees or more, the number of components is as small as about 9, and the size is small. In addition, an object of the present invention is to provide means for realizing a zoom lens having a resolving power corresponding to an image sensor with 10 to 15 million pixels at higher quality and at lower cost.

It is an object of the present invention to provide means for realizing a compact and high-performance zoom lens with higher quality and lower cost, in which each aberration is corrected better.
An object of the present invention is to provide a high-performance zoom lens in which spherical aberration and coma aberration are corrected more satisfactorily.
It is an object of the present invention to provide a high-performance zoom lens in which each aberration is corrected more satisfactorily.
The invention according to claim 11 has a zoom ratio of 10 times or more while the half angle of view at the wide angle end is 38 degrees or more and has a zoom ratio of 10 times or more. Another object of the present invention is to provide a small and high-quality camera using a zoom lens having a resolving power corresponding to an image sensor with 10 to 15 million pixels as a photographing optical system.
The invention according to claim 12 has a zoom ratio of 10 times or more while the half angle of view at the wide angle end is 38 degrees or more and has a zoom ratio of 10 times or more. Another object of the present invention is to provide a small and high-quality portable information terminal device that uses a zoom lens having a resolving power corresponding to an image sensor with 10 to 15 million pixels as a photographing optical system of a camera function unit.

The zoom lens according to any one of claims 1 to 9 has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. A third lens group, a fourth lens group having a positive refractive power, and the distance between the first lens group and the second lens group increases upon zooming from the wide-angle end to the telephoto end; The distance between the second lens group and the third lens group is decreased, the distance between the third lens group and the fourth lens group is increased, and the first lens group and the third lens group are located at a position wider than the wide-angle end. The zoom lens moves so as to be positioned on the object side at the telephoto end, and further has the following characteristics.
In order to achieve the above-described object, the zoom lens according to claim 1 is provided with an aperture stop that is independently movable in the optical axis direction during zooming between the second lens group and the third lens group. The following conditional expression (1) is satisfied.
1.0 <L _SW /|f12w|<2.5 (1)
However, Lsw represents the distance between the second lens group and the third lens group at the wide angle end, and f12w represents the combined focal length of the first lens group and the second lens group at the wide angle end.

The zoom lens according to claim 2 is characterized in that in the zoom lens according to claim 1, the following conditional expression (2) is satisfied.
0.05 <d _SW / f _T <0.20 (2)
Here, d _SW represents the axial distance between the aperture stop and the most object side surface of the third lens group at the wide angle end, and f _T represents the focal length of the entire system at the telephoto end.

The zoom lens according to claim 3 is the zoom lens according to claim 1 or 2, wherein the positive lens in the first lens group satisfies the following conditional expressions (3) and (4). It is characterized by that.
60 <νdp <95 (3)
0.007 <ΔPg _, Fp <0.05 (4)
_{However, ΔP g, F p = P} g, F p - (- 0.001802 × νdp + 0.6483),
νdp represents the dispersion of the positive lens in the first lens group, and P _{g, F} p represents the partial dispersion ratio of the positive lens.
The partial dispersion ratio _{P g, F} p _{is, P g, F p = (} n g -n F) a _{/ (n F -n C),} n g, n F, n C , respectively, the This is the refractive index of the positive lens with respect to g-line, F-line, and C-line.
A zoom lens according to a fourth aspect of the present invention is the zoom lens according to any one of the first to third aspects, wherein the following conditional expression (5) is satisfied.
5.0 <f1 / fw <8.0 (5)
However, f1 represents the focal length of the first lens group, and fw represents the focal length of the entire system at the wide angle end.
The zoom lens according to claim 5 is the zoom lens according to any one of claims 1 to 4, wherein the positive lens in the first lens group has an aspherical surface.

A zoom lens according to a sixth aspect is the zoom lens according to the fifth aspect, wherein a negative lens and a positive lens of the first lens group are cemented.
The zoom lens according to claim 7, wherein the zoom lens according to any one of claims 1 to 6 is a negative lens having a strong concave surface facing the image side closest to the image side of the third lens group. When r _3R is the radius of curvature of the surface closest to the image side of the third lens group, the following conditional expression (6) is satisfied.
0.5 <| _r3R | / fw <1.2 (6)
The zoom lens according to claim 8, in the zoom lens according to any one of claims 1 to 7, the X _1, wherein the first lens group when changing magnification from the wide-angle end to the telephoto end The following conditional expression (7) is satisfied when the total amount of movement, f _T, is the focal length of the entire system at the telephoto end.
_{0.10 <X 1 / f T <} 0.35 (7)
The zoom lens according to claim 9 is the zoom lens according to any one of claims 1 to 8, wherein f _T is a focal length of the entire system at the telephoto end, and X ₃ is from the wide angle end. When the total amount of movement of the third lens group upon zooming to the telephoto end is satisfied, the following conditional expression (8) is satisfied.
_{0.10 <X 3 / f T <} 0.30 (8)
The zoom lens according to claim 10, in the zoom lens according to claims 1 to 9, when the the f ₂ the focal length of the second lens group, the focal length of the f ₃ third lens group, the following It satisfies the following conditional expression.
_{0.50 <| f 2 | / f} 3 <0.85 (9)
A camera according to an eleventh aspect of the present invention includes the zoom lens according to any one of the first to tenth aspects as a photographing optical system.
A portable information terminal device according to a twelfth aspect of the present invention includes the zoom lens according to any one of the first to tenth aspects as a photographing optical system of a camera function unit.

According to the invention of claim 1,
A first lens group having a positive refractive power as a whole, a second lens group having a negative refractive power, a positive lens consisting of a negative lens and a positive lens having a convex surface on the object side sequentially from the object side to the image side. A third lens group having a refractive power of 4 and a fourth lens group having a positive refractive power, and at the time of zooming from the wide-angle end to the telephoto end, the first lens group and the second lens group So that the distance between the second lens group and the third lens group decreases, and the first lens group and the third lens group are positioned closer to the object side at the telephoto end than at the wide-angle end. In a moving zoom lens,
An aperture stop that is independently movable in the optical axis direction during zooming is disposed between the second lens group and the third lens group, and L _{sw is set} to the second lens group and the third lens at the wide-angle end. When the group interval is set, and f12w represents the combined focal length of the first lens group and the second lens group at the wide-angle end, the following conditional expression (1):
1.0 <L _SW /|f12w|<2.5 (1)
By satisfying the above, the half angle of view at the wide-angle end is 38 degrees or more, and it has a zoom ratio of 10 times or more while having a sufficiently wide angle of view. It is possible to provide a zoom lens having a resolving power corresponding to an image sensor with ˜15 million pixels.

According to invention of Claim 2,
The zoom lens according to claim 1.
When d _SW is the axial distance between the aperture stop at the wide-angle end and the most object side surface of the third lens group, and f _T is the focal length of the entire system at the telephoto end, the following conditional expression:
0.05 <d _SW / f _T <0.20 (2)
By satisfying the above, the half angle of view at the wide-angle end is 38 degrees or more, and it has a zoom ratio of 10 times or more while being a sufficiently wide angle of view, the number of components is as small as about 9, and the size is small. It is possible to provide a zoom lens having a resolving power corresponding to an image sensor with 10 to 15 million pixels.
According to invention of Claim 3,
The zoom lens according to claim 1 or 2,
νdp is the dispersion of the positive lens in the first lens group, P _{g, F} p is the partial dispersion ratio of the positive lens, and the partial dispersion ratios P _{g, F} p are
And P _{g, F} p ₌ a _{(n g -n F) / (} n F -n C),
Let n _g , n _F , and n _{C be the} refractive indices of the positive lens with respect to g line, F line, and C line, respectively.
_{ΔP g, F p = P g} , F p - (- 0.001802 × νdp + 0.6483) and the time,
Conditional expressions (3) and (4) below:
60 <νdp <95 (3)
0.007 <ΔPg _, Fp <0.05 (4)
By satisfying the above, it is possible to provide a high-performance zoom lens in which chromatic aberration is favorably corrected.

According to invention of Claim 4,
The zoom lens according to any one of claims 1 to 3,
When f1 is the focal length of the first lens group and fw is the focal length of the entire system at the wide angle end, the following conditional expression (5):
5.0 <f1 / fw <8.0 (5)
By satisfying the above, the half angle of view at the wide-angle end is 38 degrees or more, and it has a zoom ratio of 10 times or more while having a sufficiently wide angle of view. It is possible to provide a means for realizing a zoom lens having a resolving power corresponding to an image pickup element of ˜15 million pixels with higher quality and lower cost.
According to the invention of claim 5,
5. The zoom lens according to claim 1, wherein the positive lens of the first lens group has an aspherical surface, whereby each aberration is corrected more favorably and has a small size and high performance. It is possible to provide means for realizing a zoom lens with higher quality and lower cost.

According to the invention of claim 6,
6. The zoom lens according to claim 5, wherein a negative lens and a positive lens in the first lens group are cemented to each other so that a small and high-performance zoom lens in which each aberration is corrected better is improved. It is possible to provide means for realizing quality and low cost.
According to the invention of claim 7,
The zoom lens according to any one of claims 1 to 6, wherein a negative lens having a strong concave surface facing the image side is disposed closest to the image side of the third lens group,
When r _3R is the radius of curvature of the most image-side surface of the third lens group, the following conditional expression (6):
0.5 <| _r3R | / fw <1.2 (6)
By satisfying the above, it is possible to provide a high-performance zoom lens in which spherical aberration and coma are corrected more satisfactorily.

According to the invention described in claim 8,
The zoom lens according to any one of claims 1 to 7,
When X ₁ is the total amount of movement of the first lens group upon zooming from the wide-angle end to the telephoto end, and f _T is the focal length of the entire system at the telephoto end, the following conditional expression (7):
_{0.10 <X 1 / f T <} 0.35 (7)
By satisfying the above, it is possible to provide a high-performance zoom lens in which each aberration is corrected more satisfactorily.
According to the invention of claim 9,
The zoom lens according to any one of claims 1 to 8,
When the X _3, and the total amount of movement of the third lens group when changing magnification from the wide-angle end to the telephoto end, the following conditional expression (8):
_{0.10 <X 3 / f T <} 0.30 (8)
By satisfying the above, it is possible to provide a high-performance zoom lens in which each aberration is corrected more satisfactorily.

According to the invention of claim 10,
The zoom lens according to any one of claims 1 to 9,
The f _2, a focal length of the second lens group, when the f _3, and the focal length of the third lens group, the following conditional expression (9):
_{0.50 <| f 2 | / f} 3 <0.85 (9)
By satisfying the above, it is possible to provide a high-performance zoom lens in which each aberration is corrected more satisfactorily.

According to the invention of claim 11,
By having the zoom lens according to any one of claims 1 to 10 as a photographing optical system, the half angle of view at the wide-angle end is 38 degrees or more and a sufficiently wide angle of view is 10 times or more. The zoom lens has a zoom ratio of about 9 and is small and has a resolution that is compatible with an image sensor with 10 to 15 million pixels. A camera can be provided.
According to the invention of claim 12,
By having the zoom lens according to any one of claims 1 to 10 as a photographing optical system of a camera function unit, a half angle of view at a wide angle end is sufficiently wide as 38 degrees or more. On the other hand, a zoom lens having a zoom ratio of 10 times or more, a small number of constituent elements, such as nine, a small size, and a resolving power corresponding to an image sensor with 10 to 15 million pixels is used as a photographing optical system of the camera function unit. A small and high-quality portable information terminal device used can be provided.

It is a figure which shows the structure of the optical system of the zoom lens based on Example 1 of the 1st Embodiment of this invention, and the zoom locus | trajectory accompanying zooming, (a) is a short focus end (wide-angle end, Wide), (b) ) Is an intermediate focal length (Wide-Mean) between a short focal end (wide angle end) and an intermediate focal length, (c) is an intermediate focal length (Mean), and (d) is an intermediate focal length and a long focal end (telephoto end). (Mean-Tele) and (e) are sectional views along the optical axis at each of the long focal ends (telephoto end, Tele). FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the short focal end (wide angle end) of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end (telephoto end) of the zoom lens according to Embodiment 1 of the present invention shown in FIG. 1. It is a figure which shows the structure of the optical system of the zoom lens based on Example 2 of the 1st Embodiment of this invention, and the zoom locus | trajectory accompanying zooming, (a) is a short focus end (wide angle end, Wide), (b) ) Is an intermediate focal length (Wide-Mean) between a short focal end (wide angle end) and an intermediate focal length, (c) is an intermediate focal length (Mean), and (d) is an intermediate focal length and a long focal end (telephoto end). (Mean-Tele) and (e) are sectional views along the optical axis at each of the long focal ends (telephoto end, Tele). FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma at the short focal end (wide angle end) of the zoom lens according to Embodiment 2 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 Example 2 of the present invention shown in FIG. 5. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma at the long focal end (telephoto end) of the zoom lens according to Embodiment 2 of the present invention shown in FIG. 5. It is a figure which shows the structure of the optical system of the zoom lens which concerns on Example 3 of the 1st Embodiment of this invention, and the zoom locus | trajectory accompanying zooming, (a) is a short focus end (wide-angle end, Wide), (b) ) Is an intermediate focal length (Wide-Mean) between a short focal end (wide angle end) and an intermediate focal length, (c) is an intermediate focal length (Mean), and (d) is an intermediate focal length and a long focal end (telephoto end). (Mean-Tele) and (e) are sectional views along the optical axis at each of the long focal ends (telephoto end, Tele). FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the short focal end (wide angle end) of the zoom lens according to Example 3 illustrated in FIG. 9; 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 Example 3 illustrated in FIG. 9. FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end (telephoto end) of the zoom lens according to Example 3 illustrated in FIG. 9; It is a figure which shows the structure of the optical system of the zoom lens based on Example 4 of the 1st Embodiment of this invention, and the zoom locus | trajectory accompanying zooming, (a) is a short focus end (wide-angle end, Wide), (b) ) Is an intermediate focal length (Wide-Mean) between a short focal end (wide angle end) and an intermediate focal length, (c) is an intermediate focal length (Mean), and (d) is an intermediate focal length (telephoto end) and a long focal length. The focal lengths (Mean-Tele) and (e) intermediate to the end are cross-sectional views along the optical axis at each of the long focal ends (telephoto end, Tele). FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration, and coma aberration at the short focal end (wide angle end) of the zoom lens according to Example 4 illustrated in FIG. 13; FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 4 illustrated in FIG. 13. FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end (telephoto end) of the zoom lens according to Embodiment 4 of the present invention shown in FIG. 13; It is a figure which shows the structure of the optical system of the zoom lens based on Example 5 of the 1st Embodiment of this invention, and the zoom locus | trajectory accompanying zooming, (a) is a short focus end (wide-angle end, Wide), (b) ) Is an intermediate focal length (Wide-Mean) between a short focal end (wide angle end) and an intermediate focal length, (c) is an intermediate focal length (Mean), and (d) is an intermediate focal length and a long focal end (telephoto end). (Mean-Tele) and (e) are sectional views along the optical axis at each of the long focal ends (telephoto end, Tele). FIG. 18 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the short focal end (wide angle end) of the zoom lens according to Example 5 illustrated in FIG. 17; FIG. 18 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration in the intermediate focal length of the zoom lens according to Example 5 illustrated in FIG. 17. FIG. 18 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end (telephoto end) of the zoom lens according to Example 5 illustrated in FIG. 17; It is the perspective view seen from the to-be-photographed object side which shows typically the external appearance structure of the digital camera as an imaging device which concerns on the 2nd Embodiment of this invention. It is the perspective view seen from the photographer side which shows typically the external appearance structure of the digital camera of FIG. It is a block diagram which shows typically the function structure of the digital camera of FIG. It is a schematic diagram of the imaging visual field for demonstrating the electronic correction | amendment of the distortion aberration by the image processing used by this invention.

Hereinafter, based on an embodiment of the present invention, a zoom lens, an imaging device, and an information device according to the present invention will be described in detail with reference to the drawings. Before describing specific examples, first, a fundamental embodiment of the present invention will be described.
The zoom lens according to the first embodiment of the present invention has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. A third lens group having a positive refractive power and a fourth lens group having a positive refractive power, and the first lens group at the time of zooming from the short focal end (wide angle end) to the long focal end (telephoto end). And the distance between the second lens group increases, the distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group increases, and The zoom lens in which the first lens group and the third lens group move so that they are located closer to the object side at the long focal end than at the short focal end further has the following characteristics. .
The zoom lens having four positive, negative, positive and positive lens groups as in the present invention is generally configured as a so-called variator in which the second lens group bears a main zooming action. However, in the present invention, the third lens group also shares the zooming action, reduces the burden on the second lens group, and provides the degree of freedom of aberration correction that becomes difficult with widening and high zooming. Secured. Further, at the time of zooming from the wide angle end (short focal length end) to the telephoto end (long focal length end), the light beam that passes through the first lens group at the wide angle end is largely moved to the object side. The height is reduced to suppress the enlargement of the first lens group due to the wide angle, and the distance between the first lens group and the second lens group is kept large at the telephoto end to achieve a long focal length. Yes.

During zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group is increased, and the distance between the second lens group and the third lens group is decreased, so that the second lens group and the third lens group are Both magnifications (absolute values) of the lens group increase and share the zooming action.
Further, in the zoom lens according to the present invention, the first lens group is composed of, in order from the object side, a negative lens and a positive lens having a convex surface on the object side, and between the second lens group and the third lens group. An aperture stop that is independently movable in the optical axis direction during zooming is disposed, and the following conditional expression (1) is satisfied (corresponding to claim 1).
1.0 <Lsw / | f12w | <2.5 (1)
Here, Lsw represents the distance between the second lens group and the third lens group at the wide angle end, and f12w represents the combined focal length of the first lens group and the second lens group at the wide angle end.
When the first lens group has the two-lens configuration as described above, it is possible to suppress the beam height of the off-axis light and prevent the radial size from increasing. In addition, the main point is arranged in front of the first lens group of a three-lens configuration consisting of a cemented lens of a negative lens and a positive lens and a positive lens, which is often seen in a positive / negative / positive / four-group zoom lens type. It is possible to reduce the total length at the telephoto end where the first lens group and the second lens group are arranged apart from each other.

In addition, by arranging an aperture stop between the second lens group and the third lens group and moving the aperture stop independently of the adjacent lens group, any position in a large zooming area of 10 times or more can be obtained. In this case, since it is possible to select a more optimal ray path, the degree of freedom in correcting coma aberration, field curvature and the like is improved, and off-axis performance can be improved.
The distance between the aperture stop and the third lens group is desirably wider at the wide angle end than at the telephoto end. The third lens group using the anomalous dispersion material moves away from the aperture stop at the wide-angle end and approaches the aperture stop at the telephoto end, so that the anomalous dispersion is effective in correcting the secondary spectrum of lateral chromatic aberration at the wide-angle end. It works effectively at the telephoto end to correct the secondary spectrum of axial chromatic aberration. Therefore, chromatic aberration can be corrected more satisfactorily in the entire zoom range. In addition, the aperture stop can be brought closer to the first lens group at the wide-angle end, and the height of the light beam passing through the first lens group can be made lower, thereby further reducing the size of the first lens group. Also produces.
Therefore, in the present invention, the aperture stop is disposed at a position close to the first lens group at the wide-angle end to suppress the beam height of the off-axis light in the first lens group and the second lens group. Appropriate conditions are given to the combined refractive power of the first lens group and the second lens group and the distance between the second lens group and the third lens group. This makes it possible to widen the angle while suppressing the increase in size of the optical system. If the upper limit value of conditional expression (1) is exceeded, the height of off-axis light passing through the first lens group increases, and the radial direction and thickness direction of the first lens group may increase in size. If the lower limit of conditional expression (1) is exceeded, the negative refractive power closer to the object side than the stop may be insufficient, making it difficult to widen the angle. Alternatively, there is a risk that excessive aberration exchange occurs between the second lens group and the third lens group and the decentering sensitivity is increased.
More preferably, the following conditional expression should be satisfied.
1.5 <Lsw / | f12w | <2.0 (1) ′
For the above-described reason, when the distance between the aperture stop and the third lens group is wider than the telephoto end at the wide angle end, it is desirable that the following conditional expression (2) is satisfied with respect to the distance (corresponding to claim 2). To do).
_{0.05 <dsw / f T <0.20} (2)
Here, dsw represents the axial distance between the aperture stop at the wide angle end and the most object side surface of the third lens group.
If the lower limit value of conditional expression (2) is not reached, the height of the light beam passing through the third lens group at the wide angle end becomes small, and the secondary spectrum of lateral chromatic aberration on the wide angle side cannot be effectively reduced. Similarly, the height of the light beam passing through the first lens group at the wide angle end becomes too large, leading to an increase in the size of the first lens group. On the other hand, if the upper limit value of conditional expression (2) is exceeded, the height of the light beam passing through the third lens group at the wide-angle end becomes too large, the image surface falls over, and barrel distortion becomes large. In particular, it is difficult to ensure performance in a wide angle range.

If an attempt is made to increase the zoom ratio, particularly to increase the focal length at the telephoto end, it becomes difficult to correct the secondary spectrum of longitudinal chromatic aberration on the telephoto side. In addition, if the focal length at the wide angle end is shortened to make the angle wider, it is difficult to correct the secondary spectrum of lateral chromatic aberration on the wide angle side. In order to reduce the secondary spectrum of axial chromatic aberration, special low-dispersion glass is highly effective for a lens group having a high axial ray height. In particular, at least on the telephoto side, the first lens group has the highest axial ray height, and the use of special low dispersion glass makes it possible to sufficiently reduce the secondary spectrum of axial chromatic aberration. However, special low-dispersion glass generally has a low refractive index, resulting in a reduction in monochromatic aberration correction capability. Therefore, when it is intended to reduce monochromatic aberration and chromatic aberration in a well-balanced manner while configuring the first lens group with a small number of lenses, the use of special low dispersion glass does not necessarily give a sufficient effect.
Therefore, in order to reduce the secondary spectrum of chromatic aberration and enable sufficient correction of monochromatic aberration even when the number of first lens groups is as small as two, the positive lenses of the first lens group are as follows. It is preferable to use an optical glass having an Abbe number in the range satisfying the conditional expressions (3) and (4) (corresponding to claim 3).
60 <νdp <95 (3)
0.007 <ΔP _{g, F} p <0.05 (4)
_{However, ΔP g, F p = P} g, F p - (- 0.001802 × νdp + 0.6483),
νdp represents the dispersion of the positive lens in the first lens group, and Pg and Fp represent the partial dispersion ratio of the positive lens.

When the lower limit value of conditional expression (3) is exceeded, correction of chromatic aberration is insufficient, and when the lower limit value of conditional expression (4) is not reached, correction of the secondary spectrum of chromatic aberration is insufficient. There is no optical glass that exceeds the upper limit of conditional expressions (3) and (4), or even if it exists, it is very special and expensive, and is not practical.
Further, in order to reduce the size of the entire optical system while favorably correcting other aberrations, it is desirable to satisfy the following conditional expression (5) (corresponding to claim 4).
_{5.0 <f 1 / fw <8.0} (5)
If the lower limit value of conditional expression (5) is not reached, the imaging magnification of the second lens unit approaches the same magnification and the zooming efficiency increases, which is advantageous for high zooming. In addition to the adverse effects such as the deterioration of chromatic aberrations at the telephoto end, the first lens unit is made thicker and larger in diameter, so that it can be reduced in size especially in the retracted state. Disadvantageous above. On the other hand, if the upper limit value of conditional expression (5) is exceeded, the contribution of the second lens group to zooming becomes small, and high zooming becomes difficult.
In order to increase the degree of freedom of aberration correction, it is desirable that the positive lens of the first lens group has an aspherical surface on at least one surface (corresponding to claim 5).

Many optical glasses suitable for aspherical molding by glass mold technology have been developed, and there are a plurality of optical glasses for glass mold that satisfy the conditional expressions (3) and (4) described in claim 3. Therefore, by using these, it is possible to obtain an aspheric lens having stable performance at low cost.
In this case, it is desirable that the negative lens and the positive lens of the first lens group are cemented (corresponding to claim 6).
At the telephoto end, a thick light beam passes through the first lens group, so each lens surface of the first lens group is required to have high surface accuracy. Aspherical lenses molded as molded products are difficult to ensure high surface accuracy with respect to spherical lenses molded as cutting products, so a positive lens that is an aspherical lens and a negative lens that is a spherical lens are joined. Accordingly, it is possible to suppress deterioration in image performance due to a decrease in surface accuracy of the joint surface.
For better aberration correction, it is desirable to dispose a negative lens having a strong concave surface on the image side closest to the image side of the third lens group and satisfy the following conditional expression (6) ( Corresponding to claim 7).
0.5 <| r _3R | / fw <1.2 (6)
Here, r _3R represents the radius of curvature of the most image-side surface of the third lens group.

If the lower limit value of conditional expression (6) is not reached, spherical aberration tends to be overcorrected. If the upper limit value of conditional expression (6) is exceeded, spherical aberration tends to be undercorrected. Further, outside the range of conditional expression (6), it is difficult to balance coma as well as spherical aberration, and outward or inward coma tends to occur in the off-axis peripheral part.
It is more desirable to satisfy the following conditional expression (6) ′.
0.7 <| r _3R | / fw <1.0 (6) ′
Further, in relation to the amount of movement of the first lens group that is important for widening the angle and increasing the focal length, the following conditional expression (7) is satisfied, so that sufficient aberration correction is possible. Corresponding to).
_{0.10 <X 1 / f T <} 0.35 (7)
However, X ₁ is the total amount of movement of the first lens group when changing magnification from the wide-angle end to the telephoto end, f _T represents the focal length of the entire system at the telephoto end.
If the lower limit of conditional expression (7) is not reached, the contribution of the second lens group to zooming will be reduced and the burden on the third lens group will increase, or the refractive power of the first lens group and the second lens group will be reduced. In any case, it causes deterioration of various aberrations. In addition, the total lens length at the wide-angle end is increased, the height of light passing through the first lens group is increased, and the size of the first lens group is increased.

On the other hand, when the upper limit value of conditional expression (7) is exceeded, the total length at the wide-angle end becomes too short, or the total length at the telephoto end becomes too long. If the total length at the wide-angle end becomes too short, the moving space of the third lens group is limited, the contribution of the third lens group to zooming becomes small, and it becomes difficult to correct the entire aberration. If the total length at the telephoto end becomes too long, it will not only hinder downsizing in the full-length direction, but the radial direction will be enlarged to secure the amount of peripheral light at the telephoto end, and the lens barrel will be tilted. Degradation of image performance due to errors is also likely to occur.
It is more desirable to satisfy the following conditional expression (7) ′.
_{0.15 <X 1 / f T <} 0.30 (7) '
Regarding the movement amount of the third lens group that shares the zooming action with the second lens group, it is desirable that the following conditional expression (8) is satisfied (corresponding to claim 8).
_{0.10 <X 3 / f T <} 0.30 (8)
However, X ₃ represents the total amount of movement of the third lens group when changing magnification from the wide-angle end to the telephoto end.
If the lower limit value of conditional expression (8) is not reached, the contribution of the third lens group to zooming will be reduced, increasing the burden on the second lens group, or increasing the refractive power of the third lens group itself. In any case, various aberrations are deteriorated. On the other hand, if the upper limit value of conditional expression (8) is exceeded, the total lens length at the wide-angle end becomes long, the height of light rays passing through the first lens group increases, and the size of the first lens group increases.

More preferably, the following conditional expression (8) ′ should be satisfied.
_{0.14 <X 3 / f T <} 0.25 (8) '
In addition, it is desirable to satisfy the following conditional expression (9) regarding the refractive power of each group from the viewpoint of aberration correction (corresponding to claim 10).
_{0.50 <| f 2 | / f} 3 <0.85 (9)
Where f ₁ is the focal length of the first lens group, f ₂ is the focal length of the second lens group, f ₃ is the focal length of the third lens group, and fw is the focal length of the entire system at the wide angle end. To express.
If the lower limit value of conditional expression (9) is not reached, the refractive power of the second lens group becomes too strong. If the upper limit value of conditional expression (9) is exceeded, the refractive power of the third lens group becomes too strong. In any case, the aberration fluctuation during zooming tends to increase.
More preferably, the following conditional expression (9) ′ should be satisfied.
_{0.60 <| f 2 | / f} 3 <0.75 (9) '
The first lens group preferably has one negative lens and one positive lens sequentially from the object side to the image side. More specifically, in order from the object side to the image side, a negative meniscus lens having a convex surface facing the object side and a positive lens having a strong convex surface facing the object side may be used.

In order to increase the zoom ratio, in particular to increase the focal length at the telephoto end, it is necessary to increase the combined magnification of the second lens group, the third lens group, and the fourth lens group at the telephoto end. The aberration generated in the lens group is magnified on the image plane. For this reason, in order to advance the zooming ratio, it is necessary to sufficiently reduce the amount of aberration generated in the first lens group. For this purpose, the first lens group is preferably configured as described above.
The second lens group includes, in order from the object side to the image side, a negative lens having a large curvature surface facing the image side, a negative lens having a large curvature surface facing the image side, and a large curvature surface facing the object side. It is desirable to consist of three positive lenses facing. Thus, the second lens group is arranged in the order of the negative lens, the negative lens, and the positive lens in order from the object side to the image side, thereby lowering (moving) the principal point of the second lens group to the image side. And can contribute to shortening the overall length of the optical system at the telephoto end.
At this time, it is desirable that each lens of the second lens group satisfies the following conditional expressions (10), (11), and (12).
1.75 <N21 <2.10, 25 <ν21 <55 (10)
1.75 <N22 <2.10, 25 <ν22 <55 (11)
1.75 <N23 <2.10, 15 <ν23 <35 (12)
However, N2i represents the refractive index of the i-th lens counted from the object side in the second lens group, and ν2i represents the Abbe number of the i-th lens counted from the object side in the second lens group.

By selecting such a glass type, it is possible to correct chromatic aberration more satisfactorily while keeping monochromatic aberration sufficiently small.
The third lens group is preferably composed of three lenses in order from the object side to the image side: a positive lens, a positive lens, and a negative lens. Here, the second lens and the third lens from the object side may be appropriately joined. In addition, if optical glass satisfying the following conditional expressions (13) and (14) is employed for at least one positive lens in the third lens group, it is effective for good correction of chromatic aberration.
60.0 <νdp3 <93.0 (13)
0.007 <P _{g, F} p3-(− 0.001802 × νd + 0.6483) <0.055 (14)
Here, νdp3 represents the dispersion of the positive lens in the third lens group, and P _{g and F} p3 represent the partial dispersion ratio of the positive lens.
In the zoom lens of the present invention, the fourth lens group is provided mainly for securing an exit pupil distance (telecentricity) and focusing by movement thereof. In order to reduce the size of the lens system, the fourth lens group needs to be as simple as possible, and is preferably composed of one positive lens.

The zoom lens of the present invention is not limited to the four-group configuration. Since it is necessary to increase the degree of freedom in order to ensure performance, such as suppressing fluctuations in aberrations during zooming, a configuration in which the fifth lens group is provided on the image side of the fourth lens group may be employed.
In order to further reduce the size while maintaining good aberration correction, an aspheric surface is indispensable, and at least the second lens group and the third lens group each preferably have one or more aspheric surfaces. Particularly in the second lens group, when the object side surface of the lens on the most object side is an aspheric surface, a high effect can be obtained in correcting distortion aberration, astigmatism, etc., which tend to increase with widening of the angle.
In addition, as an aspherical lens, optical glass or optical plastic molded (glass molded aspherical surface, plastic molded aspherical surface), or a thin resin layer is molded on the surface of the glass lens, and the surface is aspherical. A thing (it is called a hybrid aspherical surface, a replica aspherical surface, etc.) etc. can be used.
It may be simplified in terms of the mechanism that the aperture diameter of the aperture is constant regardless of zooming. However, by changing the open diameter at the telephoto end compared to the wide-angle end, the change in the F number accompanying zooming can be reduced.
In addition, the aperture stop can be arranged at an arbitrary position with a higher degree of freedom by finely changing the aperture diameter according to the changing focal length range. When it is necessary to reduce the amount of light reaching the image plane, the aperture stop diameter may be reduced. However, if the amount of light is reduced by inserting an ND filter or the like without greatly changing the stop diameter, it is caused by the diffraction phenomenon. It is preferable because a decrease in resolution can be prevented.

Next, specific examples (numerical examples) of the zoom lens based on the above-described first embodiment of the present invention will be described in detail. Example 1, Example 2, Example 3, Example 4, and Example 5 are examples of specific configurations based on specific numerical examples of the zoom lens according to the present invention. In the first to fifth embodiments of the zoom lens according to the present invention, the configuration of the zoom lens and specific numerical examples thereof are shown.
In the first to fifth embodiments, the optical element formed of a parallel plate disposed on the image plane side of the fourth lens group includes various optical filters such as an optical low-pass filter and an infrared cut filter, and a CMOS image sensor. Such a cover glass (seal glass) of the light receiving element is assumed, and here, these are collectively referred to as a filter or the like (FM).
In addition, regarding the material forming the lens in the zoom lenses of Examples 1 to 5, except that the positive lens material of the fourth lens group in all the zoom lenses of Examples 1 to 5 is an optical plastic. All lenses are made of optical glass.

Specific numerical examples of the zoom lens of the present invention are shown below. In all the examples, the maximum image height is 3.93 mm. However, at the wide-angle end, in order to apply distortion-corrected image processing that generates an image by magnifying the generated negative distortion, the maximum image height is reduced in consideration of the amount of distortion as follows. It is set.
Distortion amount at wide-angle end Maximum image height at wide-angle end Example 1 -12.7% 3.698
Example 2 -15.0% 3.511
Example 3-14.6% 3.613
Example 4-13.7% 3.613
Example 5 -16.3% 3.470
In the zoom lenses according to the first to fifth embodiments, as described above, aberration correction is performed by image processing for distortion. That is, in the zoom lenses of Examples 1 to 5, in FIG. 24, the imaging range of the light receiving element (and the imaging range at the intermediate focal length and the long focal end (telephoto end)) is TF, and the short focal end (wide angle). The imaging range at the end) is denoted as WF, and a barrel-shaped distortion like the imaging range WF is generated at the short focal point on the light receiving surface TF having a rectangular shape as shown in FIG.

  On the other hand, the occurrence of distortion is suppressed in the intermediate focal length, the vicinity thereof, and the long focal end. In order to electrically correct distortion, the effective imaging range is a barrel shape (WF) at the short focal end and a rectangular shape (TF) at the intermediate focal length or the long focal end. Then, the effective imaging range (WF) at the short focal end is image-converted by image processing, and converted into rectangular image information with reduced distortion. Therefore, in the first to fourth embodiments, the image height at the short focal end is made smaller than the image height at the intermediate focal length and the image height at the long focal end. As a result, the aberrations of the respective examples are sufficiently corrected, and it is possible to deal with light receiving elements with 10 to 15 million pixels. It is clear from Examples 1 to 5 that by configuring the zoom lens as in the present invention, a very good image performance can be secured while achieving a sufficiently small size.

  In addition, the meaning of the symbol in Example 1- Example 5 is as follows.

f: Focal length of the entire system F: F value (F number)
omega: half field angle R: curvature radius D: surface interval Nd: refractive index [nu] d: Abbe number K: aspherical conic constant A _4: 4-order aspherical coefficients A _6: 6-order aspherical coefficients A _8: 8 the following aspherical coefficients a _10: 10-order aspherical coefficients a _12: 12-order aspherical coefficients a _14: 14-order aspherical coefficients, however, non-spherical, as used herein, the paraxial curvature radius of the reciprocal (near The aspherical surface is defined by the following equation, where C is the axial curvature and H is the height from the optical axis, and A _2i is the amount of displacement in the optical axis direction from the surface apex.

FIG. 1 shows a configuration of an optical system of a zoom lens according to Example 1 of the first embodiment of the present invention and from a short focal end (wide angle end) to a long focal end (telephoto end) through a predetermined intermediate focal length. 2 schematically shows a zoom locus associated with zooming, in which (a) is a cross-sectional view along the optical axis at the short focal end (Wide), and (b) is an intermediate focal length between the short focal end and the intermediate focal length. (Wide-Mean) is a cross-sectional view along the optical axis, (c) is a cross-sectional view along the optical axis at the intermediate focal length (Mean), (d) is the intermediate focal length and the long focal end (telephoto end) A sectional view along the optical axis at an intermediate focal length (Mean-Tele) and (e) are sectional views along the optical axis at the long focal end (telephoto end to Tele). In FIG. 1 showing the lens group arrangement of Example 1, the left side in the figure is the object (subject) side.
The zoom lens shown in FIG. 1 includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power in order from the object side to the image side along the optical axis. A third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power, and an aperture stop AD between the second lens group G2 and the third lens group G3. Arranged. The first lens group G1 includes a first lens L1 and a second lens L2, and the second lens group G2 includes a third lens L3, a fourth lens L4, and a fifth lens L5. The third lens group G3 includes a sixth lens L6, a seventh lens L7, and an eighth lens L8, and the fourth lens group G4 includes a single lens L9.

The first lens group G1 to the fourth lens group G4 are supported by a common support frame or the like that is appropriate for each group, and operate integrally for each group during zooming or the like. Works independently. FIG. 1 also shows the surface numbers of the optical surfaces. Note that each reference symbol in FIG. 1 is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference symbol. Therefore, a reference symbol common to the drawings according to the other embodiments. Even if attached, they are not necessarily a common configuration with other embodiments.
When zooming from the short focal end (wide angle end) to the long focal end (telephoto end), the first lens group G1 to the fourth lens group G4 are moved, and the first lens group G1 and the second lens group are moved. The distance between the group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 increases, and the first lens group G1 and the third lens group G3 move so that their positions at the long focal end are closer to the object side than the positions at the short focal end.
The first lens group G1 includes, from the object side to the image side, a first lens (negative lens) L1 including a negative meniscus lens having a convex surface directed toward the object side, and a biconvex surface having a stronger convex surface directed toward the object side. A second lens L2, which is a positive lens and is formed of an aspheric lens that forms an aspheric surface on the image plane side, is disposed. The two lenses of the first lens L1 and the second lens L2 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.

The second lens group G2 is a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side to the image side, and a third aspherical lens formed with aspheric surfaces on both sides thereof. A lens L3, a fourth lens L4 made of a plano-concave lens having a concave surface facing the image side, and a fifth lens L5 made of a positive meniscus lens having a convex surface facing the object side are arranged.
The aperture stop AD is interposed between the second lens group G2 and the third lens group G3.
The third lens group G3 is a biconvex positive lens having a stronger convex surface directed toward the object side sequentially from the object side, and a sixth lens L6 including an aspheric lens having aspheric surfaces formed on both surfaces, and is stronger on the object side. A seventh lens L7 composed of a biconvex positive lens having a convex surface and an eighth lens L8 composed of a biconcave negative lens having a stronger concave surface on the image side are disposed. The two lenses of the seventh lens L7 and the eighth lens L8 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The fourth lens group G4 is a positive meniscus lens having a stronger convex surface on the object side, and a ninth lens L9 including only a single positive lens made of an aspheric lens having an aspheric surface on the object side. Yes.

In this case, as shown in FIG. 1, the first lens group G1 moves substantially monotonously from the image side to the object side with zooming from the short focal end (wide angle end) to the long focal end (telephoto end). The second lens group G2 moves along a locus on the image side, the third lens group G3 moves from the image side to the object side, and the fourth lens group G4 moves along a locus convex toward the object side. To do.
The optical characteristics of each optical element in Example 1 are as shown in Table 1 below.
In the examples, “HOYA” is the name of the optical glass manufactured by HOYA, and “OHARA” is the name of the optical glass manufactured by OHARA.

In Table 1, the lens surface with the surface number indicated by “* (asterisk)” attached to the surface number is an aspheric surface, and after the glass name, the manufacturer name of the glass material is HOYA (HOYA Corporation). ) And OHARA (Ohara Inc.). The same applies to the other embodiments.
That is, in Table 1, the optical surfaces of the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, and the sixteenth surface to which “*” is attached are aspherical surfaces. The parameters of each aspheric surface in) are as follows.
Third side
K = 0.0, A4 = 1.38534E-05, A6 = -1.36558E-07, A8 = 4.23666E-09, A10 = -7.91700E-11, A12 = 7.38515E-13, A14 = -2.69924E-15
4th page
K = 0.0, A4 = -9.98880E-04, A6 = 8.92076E-05, A8 = -4.18167E-06, A10 = 1.11131E-07, A12 = -1.55688E-09, A14 = 8.27730E-12
5th page
K = -2.19466, A4 = 8.79976E-04, A6 = 8.83949E-05, A8 = -7.03657E-07, A10 = 2.18952E-09, A12 = -1.14906E-09, A14 = 4.93038E-11
11th page
K = -0.92885, A4 = -2.87456E-04, A6 = 8.66987E-06, A8 = -6.95226E-08, A10 = -4.94536E-08, A12 = 3.37194E-10,
12th page
K = -0.26012, A4 = 3.33383E-04, A6 = 1.65180E-05, A8 = -1.35670E-06
16th page
K = 2.72476, A4 = -3.92208E-04, A6 = 1.65553E-05, A8 = -2.19423E-06, A10 = 7.28806E-08, A12 = -3.73628E-10, A14 = -4.47617E-11
In Example 1, the focal length f of the entire optical system, the variable distance DA between the first lens group G1 and the second lens group G2, and the variable distance DB between the second lens group G2 and the aperture stop AD. , Variable distance DC between the aperture stop AD and the third lens group G3, variable distance DD between the third lens group G3 and the fourth lens group G4, and between the fourth lens group G4 and the filter FM, etc. The variable interval DE is changed as shown in the following table with zooming.

The image height Y ′ at the wide angle end (Tele) is as described above. Referring to FIG. 24, as described above, in order to perform aberration correction by image processing of distortion aberration, the imaging range at the telephoto end (and the intermediate focal length) is substantially matched with the imaging range of the light receiving element, and the rectangular shape is obtained. At the wide-angle (Wide) end, Y ′ generates a distortion aberration such that the image-capturing range at the wide-angle end has a barrel shape. Then, the barrel-shaped effective imaging range at the wide-angle end is image-converted by image processing and converted into rectangular image information with reduced distortion.
The values corresponding to the conditional expressions (1) to (9) in the first embodiment are as follows, and satisfy the conditional expressions (1) to (9), respectively.
Value of conditional expression (1) 1.67
Value of conditional expression (2) 0.137
Value of conditional expression (3) 63.85
Value of conditional expression (4) 0.0084
Value of conditional expression (5) 6.31
Value of conditional expression (6) 0.87
Value of conditional expression (7) 0.223
Value of conditional expression (8) 0.161
The value of conditional expression (9) 0.650
2, FIG. 3 and FIG. 4 show respective aberration diagrams of spherical aberration, astigmatism, distortion aberration and coma aberration (lateral aberration) at the wide-angle end, intermediate focal length and telephoto end of Example 1. ing. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.

FIG. 5 shows the configuration of the optical system of the zoom lens according to Example 2 of the first embodiment of the present invention and from the short focal point (wide angle end) to the long focal point (telephoto end) through a predetermined intermediate focal length. 2 schematically shows a zoom locus associated with zooming, where (a) is a cross-sectional view along the optical axis at the short focal end (wide angle end, Wide), and (b) is an intermediate between the short focal end and the intermediate focal length. (C) is a sectional view along the optical axis at the intermediate focal length (Mean), and (d) is the intermediate focal length and the long focal end (telephoto end). ) Is a cross-sectional view along the optical axis at an intermediate focal length (Mean-Tele) and (e) is a cross-sectional view along the optical axis at the long focal end (telephoto end to Tele). In FIG. 2 showing the arrangement of the lens groups of Example 2, the left side in the figure is the object (subject) side.
The zoom lens shown in FIG. 5 includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power in order from the object side to the image side along the optical axis. A third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power, and an aperture stop AD between the second lens group G2 and the third lens group G3. Arranged. The first lens group G1 includes a first lens L1 and a second lens L2, and the second lens group G2 includes a third lens L3, a fourth lens L4, and a fifth lens L5. The third lens group G3 includes a sixth lens L6, a seventh lens L7, and an eighth lens L8, and the fourth lens group G4 includes a single lens L9.

The first lens group G1 to the fourth lens group G4 are supported by a common support frame or the like that is appropriate for each group, and operate integrally for each group during zooming or the like. Works independently. FIG. 5 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 in FIG. 5 is used independently for each embodiment. Even if attached, they are not necessarily a common configuration with other embodiments.
When zooming from the short focal end (wide angle end) to the long focal end (telephoto end), the first lens group G1 to the fourth lens group G4 are moved, and the first lens group G1 and the second lens group are moved. The distance between the group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 increases, and the first lens group G1 and the third lens group G3 move so that their positions at the long focal end are closer to the object side than the positions at the short focal end.

The first lens group G1 includes, from the object side to the image side, a first lens (negative lens) L1 including a negative meniscus lens having a convex surface directed toward the object side, and a biconvex surface having a stronger convex surface directed toward the object side. A second lens L2, which is a positive lens and is formed of an aspheric lens that forms an aspheric surface on the image plane side, is disposed. The two lenses of the first lens L1 and the second lens L2 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The second lens group G2 is a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side to the image side, and a third aspherical lens formed with aspheric surfaces on both sides thereof. A lens L3, a fourth lens L4 made of a plano-concave lens having a concave surface facing the image side, and a fifth lens L5 made of a positive meniscus lens having a convex surface facing the object side are arranged.
The aperture stop AD is interposed between the second lens group G2 and the third lens group G3.
The third lens group G3 is a biconvex positive lens having a stronger convex surface directed toward the object side sequentially from the object side, and a sixth lens L6 including an aspheric lens having aspheric surfaces formed on both surfaces, and is stronger on the object side. A seventh lens L7 composed of a biconvex positive lens having a convex surface and an eighth lens L8 composed of a biconcave negative lens having a stronger concave surface on the image side are disposed. The two lenses of the seventh lens L7 and the eighth lens L8 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.

The fourth lens group G4 is a biconvex lens having a stronger convex surface on the object side, and a ninth lens L9 including only a single positive lens including an aspheric lens having an aspheric surface on the object side. .
In this case, as shown in FIG. 5, the first lens group G1 moves almost monotonously from the image side to the object side with zooming from the short focal end (wide angle end) to the long focal end (telephoto end). The second lens group G2 moves along a locus on the image side, the third lens group G3 moves from the image side to the object side, and the fourth lens group G4 moves along a locus convex toward the object side. To do.
The optical characteristics of the optical elements in Example 2 are as shown in Table 3 below.
In the examples, “HOYA” is the name of the optical glass manufactured by HOYA, and “OHARA” is the name of the optical glass manufactured by OHARA.

In Table 3, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspheric surface, and after the glass name, the manufacturer name of the glass material is HOYA (HOYA Corporation). ) And OHARA (Ohara Inc.). The same applies to the other embodiments.
That is, in Table 3, the optical surfaces of the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, and the sixteenth surface to which “*” is attached are aspherical surfaces. The parameters of each aspheric surface in) are as follows.
Third side
K = 0.0, A4 = 1.60890E-05, A6 = -1.80391E-07, A8 = 4.53264E-09, A10 = -6.60808E-11, A12 = 4.50767E-13, A14 = -1.03037E-15
4th page
K = 0.0, A4 = -1.59015E-03, A6 = 1.25181E-04, A8 = -5.06732E-06, A10 = 1.14533E-07, A12 = -1.30081E-09, A14 = 4.79409E-12
5th page
K = -0.38578, A4 = -1.72646E-03, A6 = 1.39845E-04, A8 = -2.34125E-06, A10 = 4.33206E-08, A12 = -7.99599E-10, A14 = 1.91470E-11
11th page
K = 0.81202, A4 = -1.22486E-03, A6 = -4.81345E-05, A8 = 2.13060E-06, A10 = -1.87468E-07, A12 = -3.08470E-09,
12th page
K = -7.04399, A4 = -7.35147E-04, A6 = 3.77826E-05, A8 = -1.14398E-06
16th page
K = 3.13290, A4 = -2.51764E-04, A6 = 6.28570E-06, A8 = -1.32660E-06, A10 = 4.61734E-08, A12 = -5.37347E-10, A14 = -2.06217E-11
In the second embodiment, the focal length f of the entire optical system, the variable distance DA between the first lens group G1 and the second lens group G2, and the variable distance DB between the second lens group G2 and the aperture stop AD. , Variable distance DC between the aperture stop AD and the third lens group G3, variable distance DD between the third lens group G3 and the fourth lens group G4, and between the fourth lens group G4 and the filter FM, etc. The variable interval DE is changed as shown in the following table with zooming.

Further, the image height Y ′ at the wide-angle end (Tele) is as described above. As described above with reference to FIG. The image pickup range at the telephoto end (and the intermediate focal length) is substantially matched to the range to obtain a rectangular image pickup range. At the wide angle end (Wide end), Y ′ is the above-described value, Distortion is generated. Then, the barrel-shaped effective imaging range at the wide-angle end is image-converted by image processing and converted into rectangular image information with reduced distortion.
The values corresponding to the conditional expressions (1) to (9) in the second embodiment are as follows, and satisfy the conditional expressions (1) to (9), respectively.

Value of conditional expression (1) 1.66
The value of conditional expression (2) 0.140
Value of conditional expression (3) 67.02
Value of conditional expression (4) 0.0081
Value of conditional expression (5) 6.27
Value of conditional expression (6) 0.91
The value of conditional expression (7) 0.220
The value of conditional expression (8) 0.166
The value of conditional expression (9) 0.656
FIGS. 6, 7, and 8 show aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration (lateral aberration) at the wide-angle end, intermediate focal length, and telephoto end, respectively, in Example 2. ing. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.

FIG. 9 shows the configuration of the optical system of the zoom lens according to Example 3 of the first embodiment of the present invention and from the short focal end (wide angle end) to the long focal end (telephoto end) through a predetermined intermediate focal length. 2 schematically shows a zoom locus associated with zooming, in which (a) is a cross-sectional view along the optical axis at the short focal end (Wide), and (b) is an intermediate focal length between the short focal end and the intermediate focal length. (Wide-Mean) is a cross-sectional view along the optical axis, (c) is a cross-sectional view along the optical axis at the intermediate focal length (Mean), (d) is the intermediate focal length and the long focal end (telephoto end) A sectional view along the optical axis at an intermediate focal length (Mean-Tele) and (e) are sectional views along the optical axis at the long focal end (telephoto end to Tele). In FIG. 9 showing the lens group arrangement of the third embodiment, the left side in the figure is the object (subject) side.
The zoom lens shown in FIG. 9 includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power in order from the object side to the image side along the optical axis. A third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power, and an aperture stop AD between the second lens group G2 and the third lens group G3. Arranged. The first lens group G1 includes a first lens L1 and a second lens L2, and the second lens group G2 includes a third lens L3, a fourth lens L4, and a fifth lens L5. The third lens group G3 includes a sixth lens L6, a seventh lens L7, and an eighth lens L8, and the fourth lens group G4 includes a single lens L9.

When zooming from the short focal end (wide angle end) to the long focal end (telephoto end), the first lens group G1 to the fourth lens group G4 are moved, and the first lens group G1 and the second lens group are moved. The distance between the group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 increases, and the first lens group G1 and the third lens group G3 move so that their positions at the long focal end are closer to the object side than the positions at the short focal end.
The first lens group G1 includes, from the object side to the image side, a first lens (negative lens) L1 including a negative meniscus lens having a convex surface directed toward the object side, and a biconvex surface having a stronger convex surface directed toward the object side. A second lens L2, which is a positive lens and is formed of an aspheric lens that forms an aspheric surface on the image plane side, is disposed. The two lenses of the first lens L1 and the second lens L2 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The second lens group G2 is a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side to the image side, and a third aspherical lens formed with aspheric surfaces on both sides thereof. A lens L3, a fourth lens L4 made of a plano-concave negative lens having a concave surface facing the image side, and a fifth lens L5 made of a positive meniscus lens having a convex surface facing the object side are arranged.

The aperture stop AD is interposed between the second lens group G2 and the third lens group G3.
The third lens group G3 is a biconvex positive lens having a stronger convex surface directed toward the object side sequentially from the object side, and a sixth lens L6 including an aspheric lens having aspheric surfaces formed on both surfaces, and is stronger on the object side. A seventh lens L7 composed of a biconvex positive lens having a convex surface and an eighth lens L8 composed of a biconcave negative lens having a stronger concave surface on the image side are disposed. The two lenses of the seventh lens L7 and the eighth lens L8 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The fourth lens group G4 is a positive meniscus lens having a stronger convex surface on the object side, and a ninth lens L9 including only a single positive lens made of an aspheric lens having an aspheric surface on the object side. Yes.
In this case, as shown in FIG. 9, the first lens group G1 moves from the image side to the object side almost monotonously with zooming from the short focus end (wide angle end) to the long focus end (telephoto end). The second lens group G2 moves along a locus on the image side, the third lens group G3 moves from the image side to the object side, and the fourth lens group G4 moves along a locus convex toward the object side. To do.
The optical characteristics of the optical elements in Example 3 are as shown in Table 5 below.
In the examples, “HOYA” is the name of the optical glass manufactured by HOYA, and “OHARA” is the name of the optical glass manufactured by OHARA.

In Table 5, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspheric surface, and after the glass name is the name of the glass manufacturer, HOYA (HOYA Corporation). ) And OHARA (Ohara Inc.). The same applies to the other embodiments.
That is, in Table 5, the optical surfaces of the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, and the sixteenth surface to which “*” is attached are aspherical surfaces. The parameters of each aspheric surface in) are as follows.
Third side
K = 0.0, A4 = 1.47088E-05, A6 = -1.27888E-07, A8 = 3.95861E-09, A10 = -7.48959E-11, A12 = 7.10833E-13, A14 = -2.64943E-15
4th page
K = 0.0, A4 = -1.26621E-03, A6 = 1.03053E-04, A8 = -4.35090E-06, A10 = 1.06357E-07, A12 = -1.45333E-09, A14 = 8.62186E-12
5th page
K = -2.38476, A4 = 4.68507E-04, A6 = 8.47748E-05, A8 = -2.61143E-07, A10 = -2.70309E-08, A12 = -1.14906E-09, A14 = 4.93038E-11
11th page
K = -0.95725, A4 = -2.26398E-04, A6 = 1.23171E-05, A8 = -1.22399E-06, A10 = -2.39294E-08, A12 = 3.37194E-10
12th page
K = 0.02305, A4 = 2.46666E-04, A6 = 1.51715E-05, A8 = -1.84438E-06
16th page
K = 2.40182, A4 = -4.38803E-04, A6 = 1.44573E-05, A8 = -2.12058E-06, A10 = 7.12042E-08, A12 = -3.73628E-10, A14 = -4.47617E-11
In Example 3, the focal length f of the entire optical system, the variable distance DA between the first lens group G1 and the second lens group G2, and the variable distance DB between the second lens group G2 and the aperture stop AD. , Variable distance DC between the aperture stop AD and the third lens group G3, variable distance DD between the third lens group G3 and the fourth lens group G4, and between the fourth lens group G4 and the filter FM, etc. The variable interval DE is changed as shown in the following table with zooming.

Further, the image height Y ′ at the wide-angle end (Tele) is as described above. As described above with reference to FIG. The image pickup range at the telephoto end (and the intermediate focal length) is substantially matched to the range to obtain a rectangular image pickup range. At the wide angle end (Wide end), Y ′ is the above-described value, Distortion is generated. Then, the barrel-shaped effective imaging range at the wide-angle end is image-converted by image processing and converted into rectangular image information with reduced distortion.
The values corresponding to the conditional expressions (1) to (9) in the third embodiment are as follows, and satisfy the conditional expressions (1) to (9), respectively.

Value of conditional expression (1) 1.71
Value of conditional expression (2) 0.115
Value of conditional expression (3) 71.68
Value of conditional expression (4) 0.0211
Value of conditional expression (5) 6.73
The value of conditional expression (6) 0.89
The value of conditional expression (7) 0.244
Value of conditional expression (8) 0.185
The value of conditional expression (9) 0.656
10, FIG. 11, and FIG. 12 show aberration diagrams of spherical aberration, astigmatism, distortion aberration, and coma aberration (lateral aberration) at the wide-angle end, intermediate focal length, and telephoto end, respectively, in Example 3. ing. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.

FIG. 13 shows the configuration of the optical system of the zoom lens according to Example 4 of the first embodiment of the present invention and from the short focus end (wide angle end) to the long focus end (telephoto end) through a predetermined intermediate focal length. 2 schematically shows a zoom locus associated with zooming, in which (a) is a cross-sectional view along the optical axis at the short focal end (Wide), and (b) is an intermediate focal length between the short focal end and the intermediate focal length. (Wide-Mean) is a cross-sectional view along the optical axis, (c) is a cross-sectional view along the optical axis at the intermediate focal length (Mean), (d) is the intermediate focal length and the long focal end (telephoto end) A sectional view along the optical axis at an intermediate focal length (Mean-Tele) and (e) are sectional views along the optical axis at the long focal end (telephoto end to Tele). In FIG. 13 showing the lens group arrangement of Example 4, the left side in the figure is the object (subject) side.
The zoom lens shown in FIG. 13 includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power in order from the object side to the image side along the optical axis. A third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power, and an aperture stop AD between the second lens group G2 and the third lens group G3. Arranged. The first lens group G1 includes a first lens L1 and a second lens L2, and the second lens group G2 includes a third lens L3, a fourth lens L4, and a fifth lens L5. The third lens group G3 includes a sixth lens L6, a seventh lens L7, and an eighth lens L8, and the fourth lens group G4 includes a single lens L9.

The first lens group G1 to the fourth lens group G4 are supported by a common support frame or the like that is appropriate for each group, and operate integrally for each group during zooming or the like. Works independently.
When zooming from the short focal end (wide angle end) to the long focal end (telephoto end), the first lens group G1 to the fourth lens group G4 are moved, and the first lens group G1 and the second lens group are moved. The distance between the group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 increases, and the first lens group G1 and the third lens group G3 move so that their positions at the long focal end are closer to the object side than the positions at the short focal end.
The first lens group G1 includes, from the object side to the image side, a first lens (negative lens) L1 including a negative meniscus lens having a convex surface directed toward the object side, and a biconvex surface having a stronger convex surface directed toward the object side. A second lens L2, which is a positive lens and is formed of an aspheric lens that forms an aspheric surface on the image plane side, is disposed. The two lenses of the first lens L1 and the second lens L2 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.

The second lens group G2 is a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side to the image side, and a third aspherical lens formed with aspheric surfaces on both sides thereof. A lens L3, a fourth lens L4 made of a plano-concave negative lens having a concave surface facing the image side, and a fifth lens L5 made of a positive meniscus lens having a convex surface facing the object side are arranged.
The aperture stop AD is interposed between the second lens group G2 and the third lens group G3.
The third lens group G3 is a biconvex positive lens having a stronger convex surface directed toward the object side sequentially from the object side, and a sixth lens L6 including an aspheric lens having aspheric surfaces formed on both surfaces, and is stronger on the object side. A seventh lens L7 composed of a biconvex positive lens having a convex surface and an eighth lens L8 composed of a biconcave negative lens having a stronger concave surface on the image side are disposed. The two lenses of the seventh lens L7 and the eighth lens L8 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The fourth lens group G4 is a positive meniscus lens having a stronger convex surface on the object side, and a ninth lens L9 including only a single positive lens made of an aspheric lens having an aspheric surface on the object side. Yes.

In this case, as shown in FIG. 13, the first lens group G1 moves substantially monotonously from the image side to the object side with zooming from the short focal end (wide angle end) to the long focal end (telephoto end). The second lens group G2 moves along a locus on the image side, the third lens group G3 moves from the image side to the object side, and the fourth lens group G4 moves along a locus convex toward the object side. To do.
The optical characteristics of the optical elements in Example 1 are as shown in Table 7 below.
In the examples, “HOYA” is the name of the optical glass manufactured by HOYA, and “OHARA” is the name of the optical glass manufactured by OHARA.

In Table 7, the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface. The glass name is followed by the name of the glass manufacturer, HOYA (HOYA Corporation). ) And OHARA (Ohara Inc.). The same applies to the other embodiments.
That is, in Table 7, the optical surfaces of the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, and the sixteenth surface to which “*” is attached are aspherical surfaces. The parameters of each aspheric surface in) are as follows.
Third side
K = 0.0, A4 = 1.49894E-05, A6 = -1.40144E-07, A8 = 4.23245E-09, A10 = -7.76864E-11, A12 = 7.14614E-13, A14 = -2.58018E-15
4th page
K = 0.0, A4 = -1.20047E-03, A6 = 9.84183E-05, A8 = -4.31381E-06, A10 = 1.11173E-07, A12 = -1.54068E-09, A14 = 8.27730E-12
5th page
K = -2.38739, A4 = 6.43740E-04, A6 = 9.06969E-05, A8 = -1.76778E-06, A10 = 6.78323E-08, A12 = -1.14906E-09, A14 = 4.93038E-11
11th page
K = -0.91650, A4 = -2.51890E-04, A6 = 8.55324E-06, A8 = -2.78172E-07, A10 = -4.11220E-08, A12 = 3.37194E-10
12th page
K = -0.04544, A4 = 2.91654E-04, A6 = 1.67121E-05, A8 = -1.39509E-06
16th page
K = 2.46757, A4 = -4.24708E-04, A6 = 1.47288E-05, A8 = -2.13510E-06, A10 = 7.15894E-08, A12 = -3.73628E-10, A14 = -4.47617E-11
In the fourth embodiment, the focal length f of the entire optical system, the variable distance DA between the first lens group G1 and the second lens group G2, and the variable distance DB between the second lens group G2 and the aperture stop AD. , Variable distance DC between the aperture stop AD and the third lens group G3, variable distance DD between the third lens group G3 and the fourth lens group G4, and between the fourth lens group G4 and the filter FM, etc. The variable interval DE is changed as shown in the following table with zooming.

Further, the image height Y ′ at the wide-angle end (Tele) is as described above. As described above with reference to FIG. The image pickup range at the telephoto end (and the intermediate focal length) is substantially matched to the range to obtain a rectangular image pickup range. At the wide angle end (Wide end), Y ′ is the above-described value, Distortion is generated. Then, the barrel-shaped effective imaging range at the wide-angle end is image-converted by image processing and converted into rectangular image information with reduced distortion.
Values corresponding to the conditional expressions (1) to (9) in the fourth embodiment described above are as follows, and satisfy the conditional expressions (1) to (9), respectively.
Value of conditional expression (1) 1.66
Value of conditional expression (2) 0.154
Value of conditional expression (3) 71.68
Value of conditional expression (4) 0.0211
The value of conditional expression (5) 6.74
Value of conditional expression (6) 0.90
Value of conditional expression (7) 0.257
The value of conditional expression (8) 0.181
The value of conditional expression (9) 0.667
FIGS. 14, 15, and 16 show aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration (lateral aberration) at the wide-angle end, the intermediate focal length, and the telephoto end, respectively, in Example 4. ing.

FIG. 17 shows the configuration of the optical system of the zoom lens according to Example 5 of the first embodiment of the present invention and from the short focal point (wide angle end) to the long focal point (telephoto end) through a predetermined intermediate focal length. 4A and 4B show zoom loci associated with zooming, where (a) is a cross-sectional view along the optical axis at the short focal end (wide angle end, Wide), and (b) is an intermediate focal length between the short focal end and the intermediate focal length. (Wide-Mean) is a cross-sectional view along the optical axis, (c) is a cross-sectional view along the optical axis at the intermediate focal length (Mean), (d) is the intermediate focal length and the long focal end (telephoto end) A sectional view along the optical axis at an intermediate focal length (Mean-Tele) and (e) are sectional views along the optical axis at the long focal end (telephoto end to Tele). In FIG. 17 showing the lens group arrangement of Example 5, the left side in the figure is the object (subject) side.
The zoom lens shown in FIG. 17 includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power in order from the object side to the image side along the optical axis. A third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power, and an aperture stop AD between the second lens group G2 and the third lens group G3. Arranged. The first lens group G1 includes a first lens L1 and a second lens L2, and the second lens group G2 includes a third lens L3, a fourth lens L4, and a fifth lens L5. The third lens group G3 includes a sixth lens L6, a seventh lens L7, and an eighth lens L8, and the fourth lens group G4 includes a single lens L9.

The first lens group G1 to the fourth lens group G4 are supported by a common support frame or the like that is appropriate for each group, and operate integrally for each group during zooming or the like. Works independently.
When zooming from the short focal end (wide angle end) to the long focal end (telephoto end), the first lens group G1 to the fourth lens group G4 are moved, and the first lens group G1 and the second lens group are moved. The distance between the group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 increases, and the first lens group G1 and the third lens group G3 move so that their positions at the long focal end are closer to the object side than the positions at the short focal end.
The first lens group G1 includes, from the object side to the image side, a first lens (negative lens) L1 including a negative meniscus lens having a convex surface directed toward the object side, and a biconvex surface having a stronger convex surface directed toward the object side. A second lens L2, which is a positive lens and is formed of an aspheric lens that forms an aspheric surface on the image plane side, is disposed. The two lenses of the first lens L1 and the second lens L2 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.

The second lens group G2 is a biconcave lens having a strong concave surface directed toward the image side sequentially from the object side to the image side, and a third aspherical lens having aspheric surfaces formed on both surface sides thereof. A lens L3, a fourth lens L4 made of a plano-concave negative lens having a concave surface facing the image side, and a fifth lens L5 made of a positive meniscus lens having a convex surface facing the object side are arranged.
The aperture stop AD is interposed between the second lens group G2 and the third lens group G3.
The third lens group G3 is a biconvex positive lens having a stronger convex surface directed toward the object side sequentially from the object side, and a sixth lens L6 including an aspheric lens having aspheric surfaces formed on both surfaces, and is stronger on the object side. A seventh lens L7 composed of a biconvex positive lens having a convex surface and an eighth lens L8 composed of a biconcave negative lens having a stronger concave surface on the image side are disposed. The two lenses of the seventh lens L7 and the eighth lens L8 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The fourth lens group G4 is a positive meniscus lens having a stronger convex surface on the object side, and a ninth lens L9 including only a single positive lens made of an aspheric lens having an aspheric surface on the object side. Yes.
In this case, as shown in FIG. 17, the first lens group G1 moves from the image side to the object side almost monotonously with zooming from the short focal end (wide angle end) to the long focal end (telephoto end). The second lens group G2 moves along a locus on the image side, the third lens group G3 moves from the image side to the object side, and the fourth lens group G4 moves along a locus convex toward the object side. To do.
The optical characteristics of the optical elements in Example 5 are as shown in Table 9 below.

In Table 9, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface.
That is, in Table 9, the optical surfaces of the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, and the sixteenth surface to which “*” is attached are aspherical surfaces. The parameters of each aspheric surface in) are as follows.
Third side
K = 0.0, A4 = 1.32759E-05, A6 = -1.27159E-07, A8 = 4.01608E-09, A10 = -7.60338E-11, A12 = 7.16671E-13, A14 = -2.62900E-15
4th page
K = 0.0, A4 = -1.02996E-03, A6 = 9.62879E-05, A8 = -4.27896E-06, A10 = 1.09299E-07, A12 = -1.54650E-09, A14 = 9.38849E-12
5th page
K = -2.80066, A4 = 4.78146E-04, A6 = 8.02750E-05, A8 = -1.04189E-06, A10 = -3.41761E-09, A12 = -1.14906E-09, A14 = 4.93038E-11
11th page
K = -0.87344, A4 = -2.59886E-04, A6 = 1.02268E-05, A8 = -6.00996E-07, A10 = -2.57211E-08, A12 = 3.37194E-10
12th page
K = -0.15171, A4 = 2.54774E-04, A6 = 1.23862E-05, A8 = -1.20226E-06
16th page
K = 2.85885, A4 = -3.58595E-04, A6 = 1.26921E-05, A8 = -2.00267E-06, A10 = 6.96542E-08, A12 = -3.73628E-10, A14 = -4.47617E-11
In Example 5, the focal length f of the entire optical system, the variable distance DA between the first lens group G1 and the second lens group G2, and the variable distance DB between the second lens group G2 and the aperture stop AD. , Variable distance DC between the aperture stop AD and the third lens group G3, variable distance DD between the third lens group G3 and the fourth lens group G4, and between the fourth lens group G4 and the filter FM, etc. The variable interval DE is changed as shown in the following table with zooming.

Further, the image height Y ′ at the wide-angle end (Tele) is as described above. As described above with reference to FIG. The image pickup range at the telephoto end (and the intermediate focal length) is substantially matched to the range to obtain a rectangular image pickup range. At the wide angle end (Wide end), Y ′ is the above-described value, Distortion is generated. Then, the barrel-shaped effective imaging range at the wide-angle end is image-converted by image processing and converted into rectangular image information with reduced distortion.
The values corresponding to the conditional expressions (1) to (9) in the fifth embodiment are as follows, and satisfy the conditional expressions (1) to (9), respectively.

Value of conditional expression (1) 1.82
Value of conditional expression (2) 0.128
Value of conditional expression (3) 63.85
Value of conditional expression (4) 0.0084
Value of conditional expression (5) 6.33
The value of conditional expression (6) 0.89
The value of conditional expression (7) 0.153
Value of conditional expression (8) 0.163
The value of conditional expression (9) 0.645
18, 19 and 20 show aberration diagrams of spherical aberration, astigmatism, distortion aberration and coma aberration (lateral aberration) at the wide-angle end, intermediate focal length and telephoto end, respectively, in Example 5. ing. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.

  Next, a digital camera as an imaging apparatus according to the second embodiment of the present invention configured by adopting the zoom lens according to the first embodiment of the present invention described above as an imaging optical system will be described with reference to FIGS. This will be described with reference to FIG. FIG. 21 is a perspective view schematically showing the external appearance of the digital camera viewed from the front side that is the object side, that is, the subject side, and FIG. 22 is a schematic external view of the digital camera viewed from the back side that is the photographer side. FIG. 23 is a schematic block diagram showing a functional configuration of a digital camera. Here, the image pickup apparatus is described taking a digital camera as an example, but the zoom lens according to the present invention may be employed in a silver salt film camera using a silver salt film as a conventional image recording medium. In addition, an information device such as a so-called PDA (personal data assistant) or a portable information terminal device such as a cellular phone in which a camera function is incorporated is widely used. Although such an information device also has a slightly different appearance, it includes substantially the same functions and configuration as a digital camera, and the zoom lens according to the present invention is adopted as an imaging optical system in such an information device. May be.

As shown in FIGS. 21 and 22, the digital camera includes a photographing lens 101, an optical viewfinder 102, a strobe (flash light) 103, a shutter button 104, a camera body 105, a power switch 106, a liquid crystal monitor 107, an operation button 108, a memory. A card slot 109 and a zoom switch 110 are provided. Furthermore, as shown in FIG. 23, the digital camera includes a central processing unit (CPU) 111, an image processing device 112, a light receiving element 113, a signal processing device 114, a semiconductor memory 115, a communication card 116, and the like.
The digital camera includes a photographing lens 101 as an imaging optical system and a light receiving element 113 configured as an image sensor using a CMOS (complementary metal oxide semiconductor) imaging element or a CCD (charge coupled device) imaging element. The light receiving element 113 reads an optical image of a subject (object) formed by the photographing lens 101. As the taking lens 101, the zoom lens according to the present invention as described in the first embodiment is used (corresponding to claim 11 or claim 12).
The output of the light receiving element 113 is processed by a signal processing device 114 controlled by the central processing unit 111 and converted into digital image information. That is, such a digital camera includes means for converting a captured image (subject image) into digital image information. This means substantially controls the light receiving element 113, the signal processing device 114, and these. Central processing unit (CPU) 111 and the like.

The image information digitized by the signal processing device 114 is recorded in a semiconductor memory 115 such as a nonvolatile memory after being subjected to predetermined image processing in the image processing device 112 which is also controlled by the central processing unit 111. In this case, the semiconductor memory 115 may be a memory card loaded in the memory card slot 109 or a semiconductor memory built in the camera body (on-board). The liquid crystal monitor 107 can display an image being photographed, or can display an image recorded in the semiconductor memory 115. The image recorded in the semiconductor memory 115 can also be transmitted to the outside via a communication card 116 or the like loaded in a communication card slot (not shown).
When the camera is carried, the objective surface of the photographic lens 101 is covered with a lens barrier (not shown). When the user operates the power switch 106 to turn on the power, the lens barrier is opened and the objective surface is The structure is exposed. At this time, in the lens barrel of the photographing lens 101, the optical systems of the respective groups constituting the zoom lens are arranged at, for example, a short focal end (wide angle end), and each zoom switch 110 is operated by operating the zoom switch 110. The arrangement of the group optical system is changed, and the zooming operation to the long focal end (telephoto end) can be performed via the intermediate focal length. It is desirable that the optical system of the optical finder 102 is also scaled in conjunction with the change in the angle of view of the photographing lens 101.

In many cases, focusing is performed by half-pressing the shutter button 104. Focusing in the zoom lens according to the present invention (the zoom lens defined in claims 1 to 10 or shown in the first to fifth embodiments described above) is one of a plurality of optical systems constituting the zoom lens. This can be done by moving a group of parts or moving a light receiving element. When the shutter button 104 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 115 is displayed on the liquid crystal monitor 107 or transmitted to the outside via the communication card 116 or the like, the operation button 108 is operated as specified. The semiconductor memory 115 and the communication card 116 are used by being loaded into dedicated or general-purpose slots such as the memory card slot 109 and the communication card slot, respectively.
As described above, in the digital camera (imaging device) or information device as described above, the photographic lens 101 configured using the zoom lens as described in the first embodiment is used as the imaging optical system. can do. Therefore, it is possible to realize a small digital camera (imaging device) or information device with high image quality using light receiving elements having 10 million to 15 million pixels or more.

  Also, it can be applied as a zoom photographing lens of a silver salt camera and a projection lens of a projector.

G1 first lens group (positive)
G2 Second lens group (negative)
G3 Third lens group (positive)
G4 4th lens group (positive)
L1, L2, L3, L4, L5, L6, L7, L8, L9 1st lens, 2nd lens, 3rd lens, 4th lens, 5th lens, 6th lens, 7th lens, 8th lens, 1st lens 9 lenses AD aperture stop FM filter, etc. 101 Shooting lens 102 Optical viewfinder 103 Strobe (flash light)
104 Shutter button 105 Camera body 106 Power switch 107 Liquid crystal monitor 108 Operation button 109 Memory card slot 110 Zoom switch 111 Central processing unit (CPU)
112 Image processing device 113 Light receiving element 114 Signal processing device 115 Semiconductor memory 116 Communication card, etc.

JP 2008-203453 A JP 2005-326743 A Japanese Patent Laid-Open No. 2001-318312

Claims (12)

A first lens group having a positive refractive power as a whole, a second lens group having a negative refractive power, a positive lens consisting of a negative lens and a positive lens having a convex surface on the object side sequentially from the object side to the image side. A third lens group having a refractive power of 4 and a fourth lens group having a positive refractive power, and at the time of zooming from the wide-angle end to the telephoto end, the first lens group and the second lens group So that the distance between the second lens group and the third lens group decreases, and the first lens group and the third lens group are positioned closer to the object side at the telephoto end than at the wide-angle end. In a moving zoom lens,
An aperture stop movable independently in the optical axis direction during zooming is disposed between the second lens group and the third lens group, and the following conditional expression (1) is satisfied: lens.
_{1.0 <L sw / | f12w |} <2.5 (1)
Where L _sw is the distance between the second lens group and the third lens group at the wide-angle end, and f12w is the combined focal length of the first lens group and the second lens group at the wide-angle end. The zoom lens according to claim 1, wherein the following conditional expression (2) is satisfied.
0.05 <d _SW / f _T <0.20 (2)
Here, d _SW represents the axial distance between the aperture stop at the wide-angle end and the most object side surface of the third lens group, and f _T represents the focal length of the entire system at the telephoto end. 3. The zoom lens according to claim 1, wherein the positive lens in the first lens group satisfies the following conditional expressions (3) and (4): 4.
60 <νdp <95 (3)
0.007 <ΔPg _, Fp <0.05 (4)
_{However, ΔP g, F p = P} g, F p - (- 0.001802 × νdp + 0.6483),
νdp represents the dispersion of the positive lens in the first lens group, and P _{g, F} p represents the partial dispersion ratio of the positive lens.
The partial dispersion ratio _{P g, F} p _{is, P g, F p = (} n g -n F) a _{/ (n F -n C),} n g, n F, n C , respectively, the This is the refractive index of the positive lens with respect to g-line, F-line, and C-line. The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression (5) is satisfied.
5.0 <f1 / fw <8.0 (5)
However, f1 represents the focal length of the first lens group, and fw represents the focal length of the entire system at the wide angle end.   5. The zoom lens according to claim 1, wherein the positive lens of the first lens group has an aspherical surface. 6.   6. The zoom lens according to claim 5, wherein the negative lens and the positive lens of the first lens group are cemented. 7. The zoom lens according to claim 1, wherein a negative lens having a strong concave surface facing the image side is disposed closest to the image side of the third lens group, and the following conditional expression: A zoom lens satisfying (6).
0.5 <| _r3R | / fw <1.2 (6)
Here, r _3R represents the radius of curvature of the most image side surface of the third lens group. 8. The zoom lens according to claim 1, wherein the following conditional expression (7) is satisfied.
_{0.10 <X 1 / f T <} 0.35 (7)
However, X ₁ is the total amount of movement of the first lens group when changing magnification from the wide-angle end to the telephoto end, f _T represents the focal length of the entire system at the telephoto end. 9. The zoom lens according to claim 1, wherein the following conditional expression (8) is satisfied.
_{0.10 <X 3 / f T <} 0.30 (8)
However, X ₃ represents the total amount of movement of the third lens group when changing magnification from the wide-angle end to the telephoto end. 10. The zoom lens according to claim 1, wherein the following conditional expression (9) is satisfied: 10.
_{0.50 <| f 2 | / f} 3 <0.85 (9)
However, f ₂ is the focal length of the second lens group, f ₃ represents the focal length of the third lens group.   11. A camera comprising the zoom lens according to claim 1 as a photographing optical system.   11. A portable information terminal device comprising the zoom lens according to claim 1 as a photographing optical system of a camera function unit.

Images