JP2009098585A - Zoom lens, camera and personal digital assistant device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a downsized zoom lens having a wide angle whose half field angle is 38°or more, a variable magnification of 6.5 times or more, a small number of lenses such as about 10 lenses and a resolution corresponding to an imaging element of 7-10 million pixels. <P>SOLUTION: The zoom lens includes an optical system of four groups, in order from an object side, G1, G2, G3 and G4 having positive-negative-positive-positive refractive power. When varying a field angle from a wide-angle end to a telephoto end, a first lens group G1 and a third lens group G3 are moved to be located on the object side at the telephoto end rather than the wide-angle end such that a distance between the first lens group G1 and a second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases and a distance between the third lens group G3 and a fourth lens group G4 increases. In particular, the first lens group G1 includes one negative lens and two positive lenses, at least one of the two positive lenses of the first lens group includes an aspherical surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a zoom lens, and more particularly to an imaging lens device, for example, a digital camera, a video camera, and a personal computer, which captures an object image optically by an optical system and outputs it as an electrical signal by an imaging device. The present invention relates to a zoom lens that can be used as a main component of a camera built in or externally attached to a mobile computer, a mobile phone, a personal digital assistant (PDA), etc., and can also be used as a silver salt camera or the like. .

The market for digital cameras is very large, and the demands of users for digital cameras are diverse. In particular, high image quality and miniaturization are always a particular desire of users, and there is a great demand. Therefore, a zoom lens used as a photographing lens is also required to have both high performance and downsizing.
Here, in terms of downsizing, it is necessary to shorten the total lens length (distance from the lens surface closest to the object side to the image plane) during use, and to 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 a resolving power corresponding to at least an image sensor of 7 million to 10 million pixels over the entire zoom range.
In addition, there are many users who desire a wide angle of view of the photographing lens, and it is desirable that the half angle of view at the wide angle end of the zoom lens is 38 degrees or more. A half angle of view of 38 degrees corresponds to a focal length of 28 mm in terms of a 35 mm silver salt camera (so-called Leica version).
Furthermore, it is desired that the zoom ratio is as large as possible. A zoom lens equivalent to about 28 to 200 mm (about 7.1 times) with a focal length equivalent to a 35 mm silver salt camera is considered to be able to handle almost all general photographing.

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 small zoom lens, a type in which the first lens unit is moved to the object side upon zooming from the wide-angle end to the telephoto end is desirable. 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.

On the other hand, it is known that use of a lens having anomalous dispersion is effective in correcting chromatic aberration that is likely to occur as the zoom ratio is increased, the focal length is increased, and the angle of view is increased. In order from the object side, there are a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive index. In zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group As conventional examples in which a lens having anomalous dispersion is used as a zoom lens in which the distance from the fourth lens group changes, Patent Document 1 (Japanese Patent Laid-Open No. 08-248317) and Patent Document 2 (Japanese Patent Laid-Open No. 2001-021803). Gazette), patent document 3 (Japanese Patent Laid-Open No. 2001-194590), and the like.
Further, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. When the zooming is performed 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. As a zoom lens using a zoom lens in which at least the first lens group and the third lens group move toward the object side so that the distance between the lens group and the fourth lens group is increased, Patent Document 4 (Japanese Patent Application Laid-Open No. 2004-212616). And Japanese Patent Application Laid-Open No. 2006-337592).

However, in the zoom lens described in Patent Document 1, since the first lens group is fixed at the time of zooming, no wide angle is achieved, and the half angle of view at the wide angle end is only 25 degrees. The zoom lens disclosed in Patent Document 2 performs aberration correction using an aspherical surface for the first lens group. However, since the first lens group is fixed at the time of zooming, a half-image at the wide angle end is also used. The angle is only 29 degrees. Furthermore, the zoom lens disclosed in Patent Document 3 moves the first lens group toward the object side during zooming from the wide-angle end to the telephoto end, but implements a positive / negative / positive / positive four-group configuration. In the examples (Examples 1, 2 and 6), the angle of view at the wide-angle end is about 29 to 32 degrees, which is also insufficient in terms of widening the angle.
In the variable focal length lens system described in Patent Document 4, the half angle of view at the wide-angle end is about 34 degrees to 37 degrees. However, there is still room for improvement in terms of high zooming.
Further, the zoom lens disclosed in Patent Document 5 has a sufficiently wide half field angle of 38 degrees or more and a zoom ratio of 4.5 times or more, but has a zoom ratio of about 4 to 8 million pixels. However, there is still room for improvement in terms of achieving high resolution.

Japanese Patent Laid-Open No. 08-248317 JP 2001-021803 A JP 2001-194590 A JP 2004-212616 A JP 2006-337592 A

The present invention has been made in view of the above circumstances, and the invention according to claim 1 is not less than 6.5 times while the half angle of view at the wide-angle end is a sufficiently wide angle of 38 degrees or more. An object of the present invention is to provide a zoom lens having a zoom ratio, a small number of constituent elements, such as about 10, and a small size and having a resolving power corresponding to an image sensor with 7 to 10 million pixels.
An object of the present invention is to provide a low-cost and high-performance zoom lens that can be manufactured more easily.
A third object of the present invention is to provide a high-performance zoom lens in which chromatic aberration and monochromatic aberration are corrected in a well-balanced manner.
An object of the present invention is to provide a high-performance zoom lens that corrects chromatic aberration more favorably and can easily obtain stable performance.
The object of the present invention is to provide a compact and high-performance zoom lens with further improved off-axis performance.
An object of the present invention is to provide a compact and high-performance zoom lens in which monochromatic aberration is corrected more favorably.

It is an object of the present invention to provide a high-performance zoom lens in which aberrations are corrected in a well-balanced manner over the entire zoom range.
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 6.5 times or more while the half angle of view at the wide angle end is a sufficiently wide angle of 38 degrees or more, and the number of components is as small as about 10, It is an object of the present invention to provide a small and high-quality camera using a small zoom lens having a resolving power corresponding to an image sensor with 7 million to 10 million pixels as a photographing optical system.
The invention according to claim 12 has a zoom ratio of 6.5 times or more and a small number of components, such as about 10 sheets, while the half angle of view at the wide angle end is a sufficiently wide angle of 38 degrees or more. An object of the present invention is to provide a small-sized and high-quality portable information terminal device using a small zoom lens having a resolving power corresponding to an image sensor with 7 to 10 million pixels as a photographing optical system of a camera function unit It is said.

The zoom lens according to any one of claims 1 to 10 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 the zoom lens according to claim 1, the first lens group includes one negative lens and two positive lenses, the first lens group has an aspheric surface, and ν _d is the first lens group. When the Abbe number, Δθg _{, F} of at least one positive lens in one lens group is defined as anomalous dispersion of the positive lens, the following conditional expression is satisfied.
ν _d > 60.0
Δθ _{g, F} > 0.003
Here, the anomalous dispersion Δθ _{g, F} is the Abbe number ν _d on the horizontal axis and the partial dispersion ratio θ _{g, F} = (n _g −n _F ) / (n _F −n _C ) on the vertical axis. In the graph, it is a deviation from the standard line of the glass type when a straight line connecting the glass type K7 (for example, OHARA glass type name NSL7) and the glass type F2 (for example, OHARA glass type name PBM2) is a standard line. _{Incidentally,} n _g, n F, _{n C,} respectively, g-line, F-line, the refractive index for the C line.

The zoom lens according to claim 2 is the zoom lens according to claim 1, wherein the aspherical surface of the first lens group is provided in a positive lens, and the positive lens provided with the aspherical surface is provided in the claim. 1 is not satisfied.
The zoom lens according to claim 3 is the zoom lens according to claim 2, wherein f _ap is a focal length of the positive lens of the first lens group satisfying the conditional expression of claim 1, and f _W is a wide angle. The following conditional expression is satisfied when the focal length of the entire system at the end is satisfied.
_{7.0 <f ap / f W <} 17.0
The zoom lens according to claim 4 is the zoom lens according to any one of claims 1 to 3, wherein the first lens group has a convex surface facing the object side in order from the object side. It is composed of three lenses, a positive lens having a surface with a large curvature facing the object side and a positive lens having a surface with a large curvature facing the object side, and the aspherical surface is provided on the most positive lens on the image side To do.
The zoom lens according to claim 5 is the zoom lens according to any one of claims 1 to 4, wherein an aperture stop is disposed between the second lens group and the third lens group. The aperture stop moves independently of the adjacent lens group.

A zoom lens according to a sixth aspect is the zoom lens according to any one of the first to fifth aspects, wherein the aperture stop is disposed between the second lens group and the third lens group. Each of the second lens group and the third lens group has at least one aspherical surface.
A zoom lens according to a seventh aspect is the zoom lens according to the sixth aspect, wherein L _a1-a2 W is a distance from the aspherical surface of the first lens group to the aspherical surface of the second lens group at the wide angle end, L _a1-s W is the distance from the aspherical surface of the first lens group to the aperture stop at the wide-angle end, and L _a1-a2 T is the non-spherical surface of the second lens group from the aspherical surface of the first lens group at the telephoto end. When the distance to the spherical surface, L _a1−s T, is the distance from the aspherical surface of the first lens unit to the aperture stop at the telephoto end, and each lens unit has a plurality of aspherical surfaces, the aperture stop The following conditional expression is satisfied when the numerical value for the aspheric surface closest to is satisfied.
0.40 <L _a1-a2 W / L _a1-s W <0.70
0.80 <L _a1-a2 T / L _a1-s T <1.00

The zoom lens according to claim 8 is the zoom lens according to claim 6 or 7, wherein L _s-a3 W is a distance from the aperture stop at the wide angle end to the aspherical surface of the third lens group, L _{When s-a3} T is the distance from the aperture stop at the telephoto end to the aspherical surface of the third lens group, when one lens group has a plurality of aspherical surfaces, each of the aspherical surfaces closest to the aperture stop When the numerical value of is satisfied, the following conditional expression is satisfied.
0.10 <Ls _-a3W / _La1-sW <0.40
0.00 <Ls _-a3T / _Lal-sT <0.20
The zoom lens according to claim 9 is the zoom lens according to any one of claims 1 to 8, wherein the third lens group includes two positive lenses and one negative lens. It is characterized by that.
A zoom lens according to a tenth aspect is the zoom lens according to the ninth aspect, wherein a negative lens having a strong concave surface facing the image side is disposed on the most image side of the third lens group, and R _3R is set. When the radius of curvature of the surface closest to the image side of the third lens group is satisfied, the following conditional expression is satisfied.
0.70 <| R _3R | / f _W <1.30
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 first aspect of the present invention, in order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, the third lens group having a positive refractive power, And a fourth lens group having a refractive power of 5 mm, and when zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases, and the second lens group and the second lens group The distance between the third lens group decreases, the distance between the third lens group and the fourth lens group increases, and the first lens group and the third lens group are closer to the object side at the telephoto end than at the wide angle end. In the zoom lens that moves so as to be positioned, the first lens group includes one negative lens and two positive lenses, and the first lens group has an aspheric surface,
ν _d is the Abbe number of at least one positive lens in the first lens group, Δθ _{g, F} is the anomalous dispersion of the positive lens (the Abbe number ν _d is the horizontal axis, and the partial dispersion ratio θ _{g, F} = in _(n g _-n F) _/ graph and _(n F -n _C) a longitudinal axis, when a standard line a straight line connecting the glass type K7 and glass type F2, and deviation hereinafter) from the standard line of the glass types , _{n g,} n F, _{n C,} respectively, g-line, F-line, when the refractive index for the C line,
ν _d > 60.0 (1)
Δθ _{g, F} > 0.003 (2)
By satisfying the following conditional expression, the half angle of view at the wide-angle end is a sufficiently wide angle of 38 degrees or more, but has a zoom ratio of 6.5 times or more and the number of components is about 10 It is possible to provide a zoom lens that has a small size and a resolution that is compatible with an image sensor of 7 million to 10 million pixels, and is small in size and high in image quality, and sufficiently covers a normal shooting area. It is possible to realize a camera and a portable information terminal device having a variable magnification range.

According to a second aspect of the present invention, in the zoom lens according to the first aspect, the aspherical surface of the first lens group is provided in a positive lens, and the positive lens provided with the aspherical surface is By not satisfying the conditional expression described in item 1, it is possible to provide a low-cost and high-performance zoom lens that can be manufactured more easily. An apparatus can be realized.
According to the invention of claim 3, in the zoom lens of claim 2, f _ap is a focal length of the positive lens of the first lens group that satisfies the conditional expression of claim 1, When _fw is the focal length of the entire system at the wide-angle end,
7.0 < _fap / _fw <17.0
By satisfying the above conditions, it is possible to provide a high-performance zoom lens that corrects chromatic aberration and monochromatic aberration in a well-balanced manner. As a result, color misalignment at the periphery of the screen at the wide-angle end and the entire screen at the telephoto end It is possible to realize a camera and a portable information terminal device that are excellent in resolving power while further suppressing color bleeding and the like.

According to a fourth aspect of the present invention, in the zoom lens according to any one of the first to third aspects, the first lens group is a negative lens having a convex surface directed toward the object side in order from the object side. A meniscus lens, a positive lens having a large curvature surface facing the object side, a positive lens having a large curvature surface facing the object side, and a configuration in which the aspherical surface is provided on the most image side positive lens Therefore, it is possible to provide a high-performance zoom lens that corrects chromatic aberration better and can easily obtain stable performance, and in turn, realizes a camera and a portable information terminal device that can obtain good depiction without variation. can do.
According to a fifth aspect of the present invention, in the zoom lens according to any one of the first to fourth aspects, an aperture stop is disposed between the second lens group and the third lens group. Since the aperture stop is configured to move independently of the adjacent lens group, it is possible to provide a small, high-performance zoom lens with further improved off-axis performance, and thus the entire screen. Therefore, it is possible to realize a small camera and a portable information terminal device having high resolution over a wide range and higher image quality.

According to a sixth aspect of the present invention, in the zoom lens according to any one of the first to fifth aspects, the aperture stop is disposed between the second lens group and the third lens group. In addition, by providing each of the second lens group and the third lens group having at least one aspherical surface, a compact and high-performance zoom lens in which monochromatic aberration is corrected better is provided. As a result, it is possible to realize a high-quality camera and a portable information terminal device that can obtain images with higher sharpness.
According to a seventh aspect of the present invention, in the zoom lens according to the sixth aspect, L _a1-a2 W is a distance from the aspherical surface of the first lens group to the aspherical surface of the second lens group at the wide angle end. L _{a1 −s} W is the distance from the aspherical surface of the first lens group to the aperture stop at the wide-angle end, and L _a1−a2 T is the distance from the aspherical surface of the first lens group at the telephoto end. The distance from the aspherical surface of the second lens group to the aspherical surface, and L _a1-s T is the distance from the aspherical surface of the first lens group to the aperture stop at the telephoto end, and one lens group has a plurality of aspherical surfaces. In this case, when the numerical value is about the aspheric surface closest to the aperture stop,
0.40 <L _a1-a2 W / L _a1-s W <0.70
0.80 <L _a1-a2 T / L _a1-s T <1.00
By satisfying the following conditional expression, it is possible to provide a high-performance zoom lens in which aberrations are corrected in a well-balanced manner over the entire zoom range. Thus, it is possible to realize a high-quality camera and a portable information terminal device.

According to invention of Claim 8, in the zoom lens of Claim 6 or Claim 7,
L _s-a3 W is the distance from the aperture stop at the wide-angle end to the aspherical surface of the third lens group, and L _s-a3 T is the aperture stop at the telephoto end to the aspherical surface of the third lens group. And when one lens group has a plurality of aspheric surfaces, the numerical values for the aspheric surfaces closest to the aperture stop respectively,
0.10 <Ls _-a3W / _La1-sW <0.40
0.00 <Ls _-a3T / _Lal-sT <0.20
By satisfying the following conditional expression, it is possible to provide a high-performance zoom lens in which aberrations are corrected in a well-balanced manner over the entire zoom range. Thus, it is possible to realize a high-quality camera and a portable information terminal device.
According to a ninth aspect of the present invention, in the zoom lens according to any one of the first to eighth aspects, the third lens group includes two positive lenses and one negative lens. Accordingly, it is possible to provide a high-performance zoom lens in which each aberration is corrected more satisfactorily, and further, it is possible to realize a high-quality camera and a portable information terminal device having higher resolution.

According to a tenth aspect of the present invention, in the zoom lens according to the ninth aspect, a negative lens having a strong concave surface facing the image side is disposed on the most image side of the third lens group, and
When R _3R is the radius of curvature of the most image side surface of the third lens group,
0.70 <| R _3R | / f _W <1.30
By satisfying the following conditional expression, it is possible to provide a high-performance zoom lens in which each aberration is corrected more satisfactorily, thereby realizing a high-quality camera and a portable information terminal device with higher resolution. can do.
According to the eleventh aspect of the present invention, since the zoom lens according to any one of the first to tenth aspects is provided as a photographing optical system, the half angle of view at the wide angle end is 38 degrees or more. Although it has a sufficiently wide angle of view, it has a zoom ratio of 6.5 times or more, the number of components is as small as about 10, and it has a resolution that is compatible with a small image sensor with 7 to 10 million pixels. Since a small and high-quality camera using a zoom lens as a photographing optical system can be provided, a user can take a high-quality image with a camera having excellent portability.

  According to the twelfth aspect of the invention, since the zoom lens according to any one of the first to tenth aspects is provided as a photographing optical system of the camera function unit, the half angle of view at the wide angle end is 38. It has a zoom ratio of 6.5 times or more while having a sufficiently wide angle of view of more than 1 degree, and the number of constituent elements is as small as about 10, and it is compatible with a small and 7 million to 10 million pixel image sensor. Since it is possible to provide a small-sized and high-quality portable information terminal device that uses a zoom lens having resolving power as a photographing optical system of a camera function unit, a user can display a high-quality image with a portable information terminal device that is excellent in portability. You can take a picture and send the image to the outside.

Hereinafter, based on an embodiment of the present invention, a zoom lens according to the present invention, a camera having the zoom lens as an imaging optical system, and a portable information terminal device will be described in detail with reference to the drawings.
1 to 4 are cross-sectional views showing the configurations of zoom lenses according to first to fourth embodiments of the present invention. Among these, FIG. 1 particularly shows the configuration of Example 1 according to the present invention. 2 is a cross-sectional view showing the configuration of the second embodiment, FIG. 3 is a cross-sectional view showing the configuration of the third embodiment, and FIG.
As shown in FIGS. 1 to 4, in the first to fourth embodiments of the present invention, in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power. The third lens group G3 having a positive refractive power and the fourth lens group G4 having a positive refractive power are disposed.
Upon zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens This is a zoom lens of a type in which the distance between the group G3 and the fourth lens group G4 increases, and the first lens group G1 and the third lens group G3 move so as to be positioned closer to the object side at the telephoto end than at the wide angle end.

The zoom lens shown in FIGS. 1 to 4 includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8. , A ninth lens L9, a tenth lens L10, an aperture stop S, and an optical filter OF.
In this case, the first lens L1 to the third lens L3 constitute the first lens group G1, the fourth lens L4 to the sixth lens L6 constitute the second lens group G2, and the seventh lens L7 to the ninth lens. The lens L9 constitutes a third lens group G3, and the tenth lens L10 constitutes a fourth lens group G4. Each lens L9 is supported by a common support frame or the like that is appropriate for each group. , It operates integrally for each group. 1 to 4 show surface numbers R1 to R20 of each optical surface.
The aperture stop S is disposed between the second lens group G2 and the third lens group G3, and its position is variable during zooming.
The zoom lens according to the present invention having such a lens configuration has the following characteristics.

A 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 G2 bears a main zooming action. The However, in the present invention, the third lens group G3 is also assigned a zooming action, the burden on the second lens group G2 is reduced, and the freedom of aberration correction that becomes difficult with widening and high zooming becomes difficult. The degree is secured. Further, when zooming from the wide-angle end to the telephoto end, the first lens group G1 is largely moved toward the object side, thereby reducing the height of the light beam passing through the first lens group G1 at the wide-angle end, thereby widening the angle. The enlargement of the first lens group G1 is suppressed, and at the telephoto end, a large distance DA between the first lens group G1 and the second lens group G2 is secured to achieve a long focal length.
During zooming from the wide-angle end to the telephoto end, the distance DA between the first lens group G1 and the second lens group G2 increases, the distance DB + DC between the second lens group G2 and the third lens group G3 decreases, The magnifications (absolute values) of the second lens group G2 and the third lens group G3 both increase, and share the zooming action.

Further, in the zoom lens according to the present invention, the first lens group G1 is composed of one negative lens L1 and two positive lenses L2 and L3, and an aspherical surface is disposed in the first lens group G1. Thus, the following conditional expression is satisfied (claim 1).
ν _d > 60.0
Δθ _{g, F} > 0.003
Here, ν _d is the Abbe number of at least one positive lens in the first lens group G1, and Δθ _{g, F} represents the anomalous dispersion of the positive lens.
Here, the anomalous dispersion Δθ _{g, F} is the Abbe number ν _d on the horizontal axis and the partial dispersion ratio θ _{g, F} = ( _ng −n _F ) / (n _F −n _C ) on the vertical axis. In the graph, the deviation from the standard line of the glass type when the straight line connecting the glass type K7 (Ohara Glass Type Name NSL7) and the glass type F2 (Ohara Glass Type Name PBM2) is used as a standard line. _{Incidentally,} n _g, n F, _{n C,} respectively, g-line, F-line, the refractive index for the C line.

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. The present invention intends to correct these chromatic aberrations using so-called anomalous dispersion glass (glass having a large anomalous dispersion), and has the following characteristics.
In general, in order to reduce the secondary spectrum of axial chromatic aberration, it is effective to use anomalous dispersion glass for a lens group having a high axial ray height. The first lens group G1 has the highest axial ray height, and it is possible to sufficiently reduce the secondary spectrum of axial chromatic aberration by employing low dispersion anomalous dispersion glass for the positive lens in the first lens group G1. Become. However, anomalous dispersion glass with low dispersion generally has a low refractive index, and the ability to correct monochromatic aberrations decreases. Therefore, when it is intended to reduce monochromatic aberration and chromatic aberration in a well-balanced manner while forming the first lens group G1 with a small number, it is not always possible to obtain a sufficient effect only by using anomalous dispersion glass.
Therefore, in the embodiment of the present invention, at least one aspheric surface is disposed in the first lens group G1, and the degree of freedom in correcting monochromatic aberration is ensured. This aspherical surface is effective for correcting distortion and astigmatism at the wide-angle end, spherical aberration and coma at the telephoto end, and lowering the monochromatic aberration correction capability by using special low-dispersion glass with a low refractive index. Can be fully recovered. Further, since the first lens group G1 moves during zooming, the state of light rays passing through the aspherical surface can be controlled by this movement, and the aspherical surface is compared with the case where the first lens group G1 is fixed. The effect is relatively large.

In addition, the movement of the first lens group G1 during zooming is effective in the degree of freedom in correcting chromatic aberration by using special low dispersion glass, and not only on-axis chromatic aberration but also in reducing the secondary spectrum of lateral chromatic aberration. It is possible to have an effect.
As described above, according to the embodiment of the present invention, the secondary lens of the chromatic aberration is reduced and the monochromatic aberration is sufficiently corrected while the first lens group G1 is configured with a small number of three in total. For example, a smaller zoom lens can be realized using the increased degree of freedom. In this case, [nu _d is insufficient is the chromatic aberration correction in 60 or less, [Delta] [theta] _{g, F} becomes insufficient is the chromatic aberration of the secondary spectrum of the corrected 0.003.
In the zoom lens of the present invention, the aspherical surface of the first lens group G1 is preferably provided on the positive lens. Further, it is desirable that the positive lens provided with the aspheric surface does not satisfy the conditional expression described in claim 1 (claim 2).
The negative lens of the first lens group G1 is a glass type with a high refractive index and a high dispersion for the sake of chromatic aberration correction, but an aspherical lens using a glass type with a high refractive index and a high dispersion is difficult to process. . In the case of a glass mold type in which glass is softened at a high temperature and molded, glass types with high refractive index and high dispersion suitable for it are limited. Further, in the case of a hybrid type in which an aspherical layer is formed of an ultraviolet curable resin on the surface of a spherical polishing lens, there is a problem of poor ultraviolet transmittance, which is a characteristic of a glass type having a high refractive index and high dispersion.

On the other hand, the positive lens of the first lens group G1 does not have high dispersion like a negative lens, and it is relatively easy to make it an aspherical lens. It is easy to select a glass type suitable for a glass mold, and in the case of a hybrid, there is little problem with the transmittance of ultraviolet rays. However, the anomalous dispersion glass that satisfies the conditional expression described in claim 1 is not suitable for a glass mold, and is not suitable for a hybrid that requires post-processing because it is soft and easily damaged. .
In the zoom lens of the present invention, it is desirable that the positive lens made of the anomalous dispersion glass of the first lens group G1 has a refractive power that satisfies the following conditional expression (claim 3).
_{7.0 <f ap / f W <} 17.0
However, f _ap represents the focal length of the positive lens of the first lens group G1 that satisfies the conditional expression according to claim 1, and f _W represents the focal length of the entire system at the wide angle end.
If f _ap / f _W is 17.0 or more, the refractive power of a lens using anomalous dispersion glass is not sufficient to sufficiently reduce the secondary spectrum, and sufficient chromatic aberration correction may not be performed. On the other hand, if f _ap / f _W is 7.0 or less, it is difficult to balance chromatic aberration correction and monochromatic aberration correction such as spherical aberration at the telephoto end.

The first lens group G1 includes, in order from the object side, a negative meniscus lens L1 having a convex surface facing the object side, a positive lens L2 having a large curvature surface facing the object side, and a positive lens having a large curvature surface facing the object side Preferably, the positive lens L3 closest to the image side is provided with an aspherical surface.
As the configuration of the first lens group G1 of the positive leading zoom lens including the wide-angle region, the negative, positive, and positive configurations from the object side as described above are excellent in aberration correction capability. Also, considering that an aspherical lens is easier to make with a smaller diameter, the object side of the two positive lenses is an anomalous dispersion glass lens and the image side is an aspherical lens. This is the most reasonable configuration. The first lens group G1 is an important lens group in that a basic real image is formed at the beginning of the zoom lens. However, by adopting the above-described configuration, sufficient aberration correction can be performed.
In the zoom lens of the present invention, an aperture stop S is disposed between the second lens group G2 and the third lens group G3, and the aperture stop S is moved independently of the adjacent lens groups (G2 and G3). (Claim 5). With such a configuration, it is possible to select a more optimal ray path at any position in a large zooming region of 6.5 times or more, and in particular, the degree of freedom in correcting coma aberration and field curvature is improved. In addition, an improvement in off-axis performance can be achieved.

The distance DC between the aperture stop S and the third lens group G3 is preferably wider at the wide-angle end than at the telephoto end. The aperture stop S can be brought closer to the first lens group G1 at the wide-angle end, and the height of the light beam passing through the first lens group G1 can be made lower, so that further downsizing of the first lens group G1 can be achieved. effective.
For the reasons described above, when the distance between the aperture stop S and the third lens group G3 is wider than the telephoto end at the wide angle end, it is desirable to satisfy the following conditional expression with respect to the distance.
_{0.05 <d SW / f T <} 0.20
Here, d _SW represents the axial distance between the aperture stop S and the most object side surface of the third lens group G3 at the wide angle end, and f _T represents the focal length of the entire system at the wide angle end.
When d _SW / f _T is set to 0.05 or less, the height of the light beam passing through the first lens group G1 at the wide angle end increases, and the first lens group G1 tends to increase in size. The contribution to the off-axis aberration of the lens group G3 is reduced. On the other hand, when d _SW / f _T is set to 0.20 or more, the height of the light beam passing through the third lens group G3 at the wide angle end becomes too large, the image surface falls over, and barrel distortion is large. In any case, it is difficult to secure performance in a wide angle range.

In the zoom lens of the present invention, an aperture stop S is disposed between the second lens group G2 and the third lens group G3, and at least one surface is provided in each of the second lens group G2 and the third lens group G3. It is desirable to have an aspherical surface (claim 6). By providing an aspheric surface for each of the first lens group G1, the second lens group G2, and the third lens group G3 that play an important role in image formation and zooming, the degree of freedom in correcting monochromatic aberrations is dramatically improved. To do.
The aspheric surfaces of the first lens group G1 and the second lens group G2 are preferably provided so as to satisfy the following conditional expression (claim 7).
0.40 <L _a1-a2 W / L _a1-s W <0.70
0.80 <L _a1-a2 T / L _a1-s T <1.00
However, L _a1-a2 W is the distance from the aspherical surface of the first lens group G1 to the aspherical surface of the second lens group G2 at the wide-angle end, and L _a1-s W is the non-aperture of the first lens group G1 at the wide-angle end. The distance from the spherical surface to the aperture stop S, L _a1-a2 T is the distance from the aspheric surface of the first lens group G1 to the aspheric surface of the second lens group G2 at the telephoto end, and L _a1-s T is the first distance at the telephoto end. The distance from the aspherical surface of one lens group G1 to the aperture stop S is expressed. When one lens group has a plurality of aspherical surfaces, the numerical values are set for the aspherical surface closest to the aperture stop S.

The distance between the aspherical surfaces arranged in each lens group changes due to the movement for zooming. On the other hand, the distance between each aspherical surface and the aperture stop S also changes due to the movement for zooming. The distance between each aspheric surface and the aperture stop S is deeply related to the height of the off-axis principal ray and the height of the on-axis marginal ray, and the effect of correcting the aberration of the aspheric surface arranged in each lens group is also aspheric. The distance varies depending on the distance between them and the distance from the aperture stop S. For the aspheric surfaces provided in the first lens group G1 and the second lens group G2, the above conditional expressions are satisfied, so that distortion and astigmatism are observed at the wide angle end, and spherical aberration and coma aberration are observed at the telephoto end. It can contribute more effectively to the correction.
The aspheric surfaces of the first lens group G1 and the third lens group G3 are preferably provided so as to satisfy the following conditional expression (claim 8).
0.10 <Ls _-a3W / _La1-sW <0.40
0.00 <Ls _-a3T / _Lal-sT <0.20
Where L _s-a3 W is the distance from the aperture stop S at the wide-angle end to the aspherical surface of the third lens group G3, and L _s-a3 T is the aspherical surface of the third lens group G3 from the aperture stop S at the telephoto end. In the case where one lens group has a plurality of aspheric surfaces, the numerical values for the aspheric surfaces closest to the aperture stop S are used.

As for the aspheric surfaces provided in the first lens group G1 and the third lens group G3, by satisfying the above conditional expressions, distortion and astigmatism at the wide angle end, and spherical aberration and coma aberration at the telephoto end. It can contribute more effectively to the correction.
Of course, it is most desirable that the aspheric surfaces provided in each of the first lens group G1, the second lens group G2, and the third lens group G3 are arranged so as to satisfy the above four conditional expressions. The effect of the aspherical surface can be maximized, and good imaging performance can be secured even if the size is further reduced.
In the zoom lens according to the present invention, it is desirable that the third lens group G3 includes two positive lenses L7 and L8 and one negative lens L9. The third lens group G3 is an important lens group having both a zooming action and an image forming action, and it is difficult to satisfactorily correct monochromatic aberration and chromatic aberration with one or two lenses. On the other hand, using four or more lenses is disadvantageous in terms of miniaturization.
For better aberration correction, it is desirable to dispose a negative lens L10 having a strong concave surface on the image side closest to the image side of the third lens group G3 and satisfy the following conditional expression (claim) Item 10).
0.70 <| R _3R | / f _W <1.30
Here, R _3R represents the radius of curvature of the most image-side surface of the third lens group G3.

When | R _3R | / f _W is 0.70 or less, the spherical aberration is likely to be overcorrected, and when | R _3R | / f _W is 1.30 or more, the spherical aberration is undercorrected. Cheap. Further, outside the range of the conditional expression, as with spherical aberration, it is difficult to balance coma, and outward or inward coma tends to occur in the off-axis peripheral part.
Furthermore, regarding the amount of movement of the first lens group G1 that is important for widening the angle and increasing the focal length, the following conditional expression is satisfied, so that sufficient aberration correction can be performed.
_{0.20 <X 1 / f T <} 0.50
However, X ₁ is the total amount of movement of the first lens group G1 upon zooming from the wide-angle end to the telephoto end, f _T represents the focal length of the entire system at the telephoto end.
If X ₁ / f _T is 0.20 or less, the contribution of the second lens group G2 to zooming is reduced and the burden on the third lens group G3 is increased, or the first lens group G1 and the second lens are increased. The refractive power of the group G2 must be increased, and in any case, various aberrations are deteriorated. In addition, the total lens length at the wide-angle end is increased, the height of the light beam passing through the first lens group G1 is increased, and the size of the first lens group G1 is increased. On the other hand, the X ₁ / f _T, if 0.50 or more, or the total length at the wide angle end becomes too short, so that 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 G3 is limited, and the contribution to zooming of the third lens group G3 is reduced, making it 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 barrel will be tilted. Degradation of image performance due to errors is also likely to occur.

More preferably, the following conditional expression should be satisfied.
_{0.25 <X 1 / f T <} 0.45
Regarding the movement amount of the third lens group G3, it is desirable to satisfy the following conditional expression.
_{0.10 <X 3 / f T <} 0.35
However, X ₃ represents the total amount of movement of the third lens group G3 upon zooming from the wide-angle end to the telephoto end.
When X ₃ / f _T is set to 0.10 or less, the contribution of the third lens group G3 to zooming is reduced, the burden on the second lens group G2 is increased, or the third lens group G3 itself is refracted. In any case, it will cause deterioration of various aberrations. On the other hand, if X ₃ / f _T is set to 0.35 or more, the total lens length at the wide-angle end becomes long, the height of the light beam passing through the first lens group G1 increases, and the size of the first lens group G1 increases. Invite.

More preferably, the following conditional expression should be satisfied.
_{0.15 <X 3 / f T <} 0.30
In addition, it is desirable to satisfy the following conditional expressions concerning the refractive power of each group from the viewpoint of aberration correction (claims 9 and 10).
_{0.50 <| f 2 | / f} 3 <0.85
_{4.5 <f 1 / f W <} 7.5
However, _{f 1} is the focal length of the first lens group G1, _{f 2} is the focal length of the second lens group G2, _{f 3} is the focal length of the third lens group G3, _{f W} is the entire system at the wide angle end Represents the focal length of.
If | f ₂ | / f ₃ is 0.50 or less, the refractive power of the second lens group G2 becomes too strong. If | f ₂ | / f ₃ is 0.85 or more, the third lens group G3 The refractive power of the lens becomes too strong, and in any case, the aberration fluctuation during zooming tends to increase.
The f ₁ / f _W, when a 4.5 or less, scaling efficiency is increased by the imaging magnification of the second lens group G2 approaches the magnification, it is advantageous for high zoom ratio, the first lens group Each lens of G1 requires a large refractive power, which is not only harmful to chromatic aberration particularly at the telephoto end, but also the first lens group G1 is made thicker and larger in diameter, especially in the retracted state. This is disadvantageous for downsizing.
On the other hand, if f ₁ / f _W is set to 7.5 or more, the contribution of the second lens group G2 to zooming becomes small, and high zooming becomes difficult.
The second lens group G2, in order from the object side, is a negative lens L4 having a large curvature surface facing the image side, a positive lens L5 having a large curvature surface facing the image side, and a negative lens having a large curvature surface facing the object side. It is desirable that the lens consists of three lenses L6.

As a variable power group having a negative refractive power, in the case where this is constituted by three lenses, an arrangement of a negative lens, a negative lens, and a positive lens in order from the object side is well known. Thus, the above configuration is excellent in the ability to correct lateral chromatic aberration associated with widening the angle. Here, the second lens and the third lens from the object side may be appropriately joined.
At this time, it is desirable that each lens of the second lens group G2 satisfies the following conditional expression.
1.80 <N21 <2.15, 25 <ν21 <50
1.80 <N22 <2.15, 15 <ν22 <30
1.80 <N23 <2.15, 25 <ν23 <50
Here, N2i represents the refractive index of the i-th lens counted from the object side in the second lens group G2, and ν2i represents the Abbe number of the i-th lens counted from the object side in the second lens group G2.
By selecting a glass type having such a refractive index and an Abbe number, it becomes possible to correct monochromatic aberration and chromatic aberration better, and thus the second lens group G2 can be made thinner.

The third lens group G3 is preferably composed of three lenses in order from the object side: a positive lens L7, a positive lens L8, and a negative lens L9. Here, the second lens L8 and the third lens L9 from the object side may be appropriately joined.
An aspherical surface is indispensable for further downsizing while maintaining good aberration correction, and it is desirable that at least the second lens group G2 and the third lens group G3 each have one or more aspherical surfaces. In particular, in the second lens group G2, if both the most object-side surface and the most image-side surface are aspherical surfaces, it is highly effective in correcting distortion and astigmatism that tend to increase with a wide angle. Is obtained.
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, the change in the F number accompanying zooming can be reduced by increasing the length of the long focal point compared to the short focal end of the open diameter. Further, when it is necessary to reduce the amount of light reaching the image plane, the diameter of the stop may be reduced. However, if the amount of light is reduced by inserting an ND filter or the like without greatly changing the diameter of the stop, the diffraction phenomenon may occur. It is preferable because a decrease in resolution can be prevented.
The first to fourth embodiments of the present invention described above have a positive, negative, positive, and positive four-group configuration, that is, a first lens group having a positive refractive power in order from the object side, a negative Although it has a four-group configuration including a second lens group having a refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, a fifth embodiment will be described below. A positive, negative, positive, positive, and negative five-group configuration, that is, 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 first lens group having a positive refractive power. A zoom lens having a five-group configuration including three lens groups, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power will be described below.

FIG. 5 is a cross-sectional view showing a configuration of a zoom lens according to the fifth embodiment of the present invention.
As shown in FIG. 5, in the fifth embodiment of the present invention, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refraction. A third lens group G3 having power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power are disposed.
Upon zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens The distance between the group G3 and the fourth lens group G4 increases, the fifth lens group G5 is fixed and does not move, and the first lens group G1 and the third lens group G3 are closer to the object side at the telephoto end than at the wide angle end. This is a type of zoom lens that moves so as to be positioned.

The zoom lens shown in FIG. 5 includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a ninth lens. A lens L9, a tenth lens L10, an eleventh lens L11, an aperture stop S, and an optical filter OF are provided.
In this case, the first lens L1 to the third lens L3 constitute the first lens group G1, the fourth lens L4 to the sixth lens L6 constitute the second lens group G2, and the seventh lens L7 to the ninth lens. The lens L9 constitutes the third lens group G3, the tenth lens L10 constitutes the fourth lens group G4, and the eleventh lens L11 constitutes the fifth lens group G5. It is supported by an appropriate common support frame or the like, and operates integrally for each group during zooming or the like. FIG. 5 shows the surface numbers R1 to R22 of each optical surface.
The aperture stop S is disposed between the second lens group G2 and the third lens group G3, and its position is variable during zooming.
The zoom lens according to the fifth embodiment of the present invention having such a lens configuration has the following characteristics.

A zoom lens having five positive, negative, positive, positive, and negative lens groups as in the present invention is generally used as a so-called variator in which the second lens group G2 bears a main zooming action. Composed. However, in the present invention, the third lens group G3 is also assigned a zooming action, the burden on the second lens group G2 is reduced, and the freedom of aberration correction that becomes difficult with widening and high zooming becomes difficult. The degree is secured. Further, when zooming from the wide-angle end to the telephoto end, the first lens group G1 is largely moved toward the object side, thereby reducing the height of the light beam passing through the first lens group G1 at the wide-angle end, thereby widening the angle. The enlargement of the first lens group G1 is suppressed, and at the telephoto end, a large distance DA between the first lens group G1 and the second lens group G2 is secured to achieve a long focal length.
During zooming from the wide-angle end to the telephoto end, the distance DA between the first lens group G1 and the second lens group G2 increases, the distance DB + DC between the second lens group G2 and the third lens group G3 decreases, The magnifications (absolute values) of the second lens group G2 and the third lens group G3 both increase, and share the zooming action.

Further, in the zoom lens according to the fifth embodiment of the present invention, the first lens group G1 is composed of one negative lens L1 and two positive lenses L2 and L3, and the first lens group G1 is not. A spherical surface was provided, and in addition, the following conditional expression was satisfied.
νd> 60.0
Δθg, F> 0.003
However, νd represents the Abbe number of at least one positive lens in the first lens group G1, and Δθg, F represents the anomalous dispersion of the positive lens.
Here, the anomalous dispersion Δθg, F is a graph in which the Abbe number νd is abscissa and the partial dispersion ratio θg, F = (ng−nF) / (nF−nC) is ordinate, The deviation from the standard line of the glass type when the straight line connecting company OHARA glass type name NSL7) and glass type F2 (Ohara glass type name PBM2) is used as the standard line. In addition, ng, nF, and nC are refractive indexes with respect to g-line, F-line, and C-line, respectively.

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. The present invention intends to correct these chromatic aberrations using so-called anomalous dispersion glass (glass having a large anomalous dispersion), and has the following characteristics.
In general, in order to reduce the secondary spectrum of axial chromatic aberration, it is effective to use anomalous dispersion glass for a lens group having a high axial ray height. The first lens group G1 has the highest axial ray height, and it is possible to sufficiently reduce the secondary spectrum of axial chromatic aberration by employing low dispersion anomalous dispersion glass for the positive lens in the first lens group G1. Become. However, anomalous dispersion glass with low dispersion generally has a low refractive index, and the ability to correct monochromatic aberrations decreases. Therefore, when it is intended to reduce monochromatic aberration and chromatic aberration in a well-balanced manner while forming the first lens group G1 with a small number, it is not always possible to obtain a sufficient effect only by using anomalous dispersion glass.
Therefore, in the fifth embodiment of the present invention, as in the first to fourth embodiments described above, at least one aspherical surface is disposed in the first lens group G1 to correct monochromatic aberration. Secured a degree of freedom. This aspherical surface is effective for correcting distortion and astigmatism at the wide-angle end, spherical aberration and coma at the telephoto end, and lowering the monochromatic aberration correction capability by using special low-dispersion glass with a low refractive index. Can be fully recovered. Further, since the first lens group G1 moves during zooming, the state of light rays passing through the aspherical surface can be controlled by this movement, and the aspherical surface is compared with the case where the first lens group G1 is fixed. The effect is relatively large.

In addition, the movement of the first lens group G1 during zooming is effective in the degree of freedom in correcting chromatic aberration by using special low dispersion glass, and not only on-axis chromatic aberration but also in reducing the secondary spectrum of lateral chromatic aberration. It is possible to have an effect.
As described above, according to the embodiment of the present invention, the secondary lens of the chromatic aberration is reduced and the monochromatic aberration is sufficiently corrected while the first lens group G1 is configured with a small number of three in total. For example, a smaller zoom lens can be realized using the increased degree of freedom. In this case, [nu _d is insufficient is the chromatic aberration correction in 60 or less, [Delta] [theta] _{g, F} becomes insufficient is the chromatic aberration of the secondary spectrum of the corrected 0.003.
In the zoom lens of the present invention, the aspherical surface of the first lens group G1 is preferably provided on the positive lens. Further, it is desirable that the positive lens provided with the aspheric surface does not satisfy the conditional expression described in claim 1.
The negative lens of the first lens group G1 is a glass type with a high refractive index and a high dispersion for the sake of chromatic aberration correction, but an aspherical lens using a glass type with a high refractive index and a high dispersion is difficult to process. . In the case of a glass mold type in which glass is softened at a high temperature and molded, glass types with high refractive index and high dispersion suitable for it are limited. Further, in the case of a hybrid type in which an aspherical layer is formed of an ultraviolet curable resin on the surface of a spherical polishing lens, there is a problem of poor ultraviolet transmittance, which is a characteristic of a glass type having a high refractive index and high dispersion.

On the other hand, the positive lens of the first lens group G1 does not have high dispersion like a negative lens, and it is relatively easy to make it an aspherical lens. It is easy to select a glass type suitable for a glass mold, and in the case of a hybrid, there is little problem with the transmittance of ultraviolet rays. However, the anomalous dispersion glass that satisfies the conditional expression described in claim 1 is not suitable for a glass mold, and is not suitable for a hybrid that requires post-processing because it is soft and easily damaged. .
In the zoom lens of the present invention, it is desirable that the positive lens made of the anomalous dispersion glass of the first lens group G1 has a refractive power that satisfies the following conditional expression.
_{7.0 <f ap / f W <} 17.0
However, f _ap represents the focal length of the positive lens of the first lens group G1 that satisfies the conditional expression according to claim 1, and f _W represents the focal length of the entire system at the wide angle end.
If f _ap / f _W is 17.0 or more, the refractive power of a lens using anomalous dispersion glass is not sufficient to sufficiently reduce the secondary spectrum, and sufficient chromatic aberration correction may not be performed. On the other hand, if f _ap / f _W is 7.0 or less, it is difficult to balance chromatic aberration correction and monochromatic aberration correction such as spherical aberration at the telephoto end.

Hereinafter, in the fifth embodiment as well, the description part of the specification related to claims 4 to 10 that describes the above-described first to fourth embodiments, particularly the first to fourth including conditional expressions. The description of the embodiment is used, and redundant description is omitted.
Specific examples (first to fifth examples) of the zoom lens according to the present invention will be described below. In all the examples, the maximum image height is 4.05 mm.
In the first to fourth embodiments, the parallel lens disposed on the image plane side of the fourth lens group G4, and in the fifth embodiment, the parallel plane disposed on the image plane side of the fifth lens G5. The flat plate OF assumes various filters such as an optical low-pass filter and an infrared cut filter, and a cover glass (seal glass) of a light receiving element such as a CCD sensor.

The materials of the lenses are all optical glass except that the positive lens L10 included in the fourth lens group G4 in all embodiments is an optical plastic.
The aberration in the example is sufficiently corrected and can correspond to a light receiving element of 7 million to 10 million pixels. It is clear from the embodiment that a very good image performance can be ensured while achieving a sufficiently small size by configuring the zoom lens as in the present invention.
The meanings of symbols in the examples are as follows.
f: the focal length F of the entire system: F number omega: half field angle R: curvature radius D: surface interval N _d: refractive index [nu _d: Abbe number K: aspherical conic constant A _4: 4-order aspheric coefficients A ₆ : 6th-order aspheric coefficient A ₈ : 8th-order aspheric coefficient A ₁₀ : 10th-order aspheric coefficient A ₁₂ : 12th-order aspheric coefficient A ₁₄ : 14th-order aspheric coefficient A ₁₆ : 16th-order Aspherical coefficient A ₁₈ : 18th-order aspherical coefficient

However, the aspherical surface used here is defined by the following equation, where C is the reciprocal of the paraxial radius of curvature (paraxial curvature) and H is the height from the optical axis.

  In the aberration diagrams described below, in spherical aberration, a solid line represents a spherical aberration, a broken line represents a sine condition, and, in astigmatism, a solid line represents a sagittal image plane and a broken line represents a meridional image plane. One solid line represents the d line (587.56 nm) and the other solid line g line (435.83 nm).

[Example 1]
FIG. 1 is a cross-sectional view showing a configuration of an optical system of a zoom lens according to Example 1 of the present invention.
The upper part of FIG. 1 shows the configuration of the optical system of the zoom lens according to Example 1 of the present invention, the middle part shows the intermediate focal length, and the lower part shows the configuration at the telephoto end.
The zoom lens shown in FIG. 1 includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, an aperture stop S, and a seventh lens. L7, the eighth lens L8, the ninth lens L9, the tenth lens L10, and the optical filter OF are arranged in this order, and an image is formed behind the optical filter OF having various optical filtering functions. In this case, the first lens L1 to the third lens L3 constitute the first lens group G1, the fourth lens L4 to the sixth lens L6 constitute the second lens group G2, and the seventh lens L7 to the ninth lens. The lens L9 constitutes the third lens group G3, and the tenth lens L10 constitutes the fourth lens group G4. Each lens L9 is supported by an appropriate support frame or the like for each group optical system. Each lens group operates integrally.

  The first lens L1 is a negative meniscus lens with a convex surface facing the object side, the second lens L2 is a positive lens with a large curvature surface facing the object side, and the third lens L3 has a large curvature surface facing the object side. It is a positive lens aimed at. Among these, the first lens L1 and the second lens L2 are sequentially closely bonded and integrally joined to form a cemented lens, and the first lens L1 to the third lens L3 are configured. The one lens group G1 as a whole has a positive focal length, that is, positive refractive power. The fourth lens L4 is a negative meniscus lens having a convex surface facing the object side, the fifth lens L5 is a biconvex lens having a surface with a large curvature on the image side, and the sixth lens L6 is a negative lens having a convex surface facing the image surface side. It is a meniscus lens. Of these, the fifth lens L5 and the sixth lens L6 are sequentially closely bonded and integrally joined to form a cemented lens, and a second lens constituted by the fourth lens L4 to the sixth lens L6. The group G2 as a whole has a negative focal length, that is, negative refractive power. S is an aperture stop that moves during zooming.

The seventh lens L7 is a biconvex lens with a large curvature surface facing the object side, the eighth lens L8 is a biconvex lens with a large curvature surface facing the image side, and the ninth lens L9 has a large curvature toward the image side. It is a biconcave lens with its surface facing. The eighth lens L8 and the ninth lens L9 are integrally joined. The third lens G3 including the seventh lens L7 to the ninth lens L9 has a positive focal length, that is, positive refractive power as a whole.
The tenth lens L10 is a biconvex lens having a surface with a large curvature toward the object side, and the fourth lens group G4 is configured only by the tenth lens L10, and has a positive focal length, that is, a positive refractive power. Have.
When changing the focal length from the wide-angle end (short focal end) to the telephoto end (long focal end), the distance between the first lens group G1 and the second lens group G2 increases, and the second lens group G2 and the second lens group G2 The distance between 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 are closer to the object side at the telephoto end than at the wide angle end. Move to be located at.

Focusing can be performed by moving the second lens group G2 or the fourth lens group G4 or moving the light receiving element.
The optical filter OF composed of parallel flat plates arranged on the most image side is a filter such as a crystal low-pass filter or an infrared cut filter.
Due to the movement of the lens groups G1 to G4 accompanying the change in focal length, the variable interval between the lens groups, that is, the most image side surface of the first lens group G1, that is, the image side surface of the third lens L3 (surface number). R5) and the distance DA between the most object side surface (surface number R6) of the second lens group G2, the most image side surface of the second lens group G2, that is, the image side surface (surface number R10) of the sixth lens L6. ) And the aperture stop S, the distance DC between the aperture stop S and the most object side surface (surface number R12) of the third lens group G3, the most image side surface of the third lens group G3, that is, the first lens surface. Distance DD between the image side surface (surface number R16) of the 9th lens L9 and the most object side surface of the fourth lens group G4, that is, the image side surface (surface number R17) of the 10th lens L10, the 4th lens group. The most image-side surface of G4, that is, the image-side surface of the tenth lens L10 (surface number R18) Spacing DE between the surface (surface number R19) on the object side of the optical filter OF are changed respectively.

In Example 1, along with the focal length change from the wide-angle end to the telephoto end,
Focal length f of entire system: 5.16 to 35.09
F number (F value): 3.49 to 5.49
Half angle of view: 39.34-6.50
And change.
The characteristics of each optical surface are as shown in the following table (Table 1).

In Table 1, the optical surfaces of the fourth surface, the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface and the seventeenth surface marked with an asterisk “*” are aspheric surfaces, The parameters in the aspheric formula are as follows.
Aspheric surface; fourth surface K = 0.0,
A ₄ = −2.99145 × 10 ⁻⁶ ,
A ₆ = −2.331719 × 10 ⁻⁸ ,
A ₈ = 1.30994 × 10 ⁻¹⁰ ,
A ₁₀ = −1.04295 × 10 ⁻¹²
Aspherical surface; 6th surface K = 0.0,
A ₄ = 5.30475 × 10 ⁻⁵ ,
A ₆ = −3.02550 × 10 ⁻⁶ ,
A ₈ = 1.775806 × 10 ⁻⁷ ,
A ₁₀ = −4.4619 × 10 ⁻⁹
A ₁₂ = −5.03303 × 10 ⁻¹¹ ,
A ₁₄ = 2.21259 × ^{10 -12}

Aspherical surface; tenth surface K = 0.0,
A ₄ = −5.772615 × 10 ⁻⁴ ,
A ₆ = 2.64313 × 10 ⁻⁷ ,
A ₈ = −1.43524 × 10 ⁻⁶ ,
A ₁₀ = −4.46966 × 10 ⁻⁸
Aspherical surface; twelfth surface K = 0.0,
A ₄ = −7.886511 × 10 ⁻⁴ ,
A ₆ = 2.14725 × 10 ⁻⁵ ,
A ₈ = -1.35163 × ^{10 -6,}
A ₁₀ = 4.222984 × 10 ⁻⁸
Aspherical surface; thirteenth surface K = 0.0,
A ₄ = 4.01016 × 10 ⁻⁴ ,
A ₆ = 2.39857 × 10 ⁻⁵ ,
A ₈ = −1.41367 × 10 ⁻⁶ ,
A ₁₀ = 4.90779 × 10 ⁻⁸

Aspheric surface: 17th surface K = 0.0,
A ₄ = −8.522233 × 10 ⁻⁵ ,
A ₆ = 1.17201 × 10 ⁻⁵ ,
A ₈ = −4.70061 × 10 ⁻⁷ ,
A ₁₀ = 8.05532 × 10 ⁻⁹

The variable distance DA between the first lens group G1 and the second lens group G2, the variable distance DB between the second lens group G2 and the aperture stop S, and the variable distance between the aperture stop S and the third lens group G3. The distance DC, the variable distance DD between the third lens group G3 and the fourth lens group G4, and the variable distance DE between the fourth lens group G4 and the optical filter OF are as shown in the following table (Table 2). It can be changed as follows.

In addition, the values of the parameters related to the conditional expressions described above in the first embodiment are as follows.
Conditional numerical value ν _d , Δθ _{g, F} : as shown in Table 1 f _ap / f _W = 11.1
L _a1-a2 W / L _a1-s W = 0.566
L _{a1 −a2} T / L _a1 −s T = 0.962
_{L s-a3 W / L a1} -s W = 0.219
L _s-a3 T / L _a1-s T = 0.027
| R _3R | / f _W = 0.938
X ₁ / f _T = 0.356
X ₃ / f _T = 0.226
| F ₂ | / f ₃ = 0.665
f ₁ / f _W = 5.81
d _SW / f _T = 0.109

Therefore, the values of the parameters related to the conditional expression described in FIG. 1 in the first embodiment are within the range of the conditional expression.

6 to 8 show aberration curve diagrams of respective aberrations in the zoom lens shown in FIG. 1 according to Example 1 described above. FIG. 6 shows aberration curve diagrams at the wide angle end, and FIG. FIG. 8 is an aberration curve diagram at the intermediate focal length, and FIG. 8 is an aberration curve diagram at the telephoto end.
In each aberration curve diagram, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional.
According to the aberration curve diagrams of FIGS. 6 to 8, it is confirmed that the aberration is corrected or suppressed satisfactorily by the zoom lens having the configuration shown in FIG. 1 according to the first embodiment of the present invention described above. I understand.
In this way, various aberrations can be satisfactorily corrected in the positive-negative-positive-positive four-group zoom lens, and the half angle of view at the wide-angle end is 38 degrees or more, while the angle of view is sufficiently wide. Therefore, it is possible to provide a zoom lens having a zoom ratio of 6.5 times or more, a small number of constituent elements, such as about 10, and a small size and a resolving power corresponding to an image sensor with 7 to 10 million pixels.
By providing this zoom lens, it is possible to realize a camera and a portable information terminal device that have a zooming area that can sufficiently cover a normal photographing area with a small size and high image quality.

[Example 2]
FIG. 2 shows configurations of the optical system of the zoom lens according to Example 2 of the present invention at the short focal end (wide angle end), the intermediate focal length, and the long focal end (telephoto end), respectively.
The zoom lens shown in FIG. 2 has the same basic configuration as that of the zoom lens shown in FIG. 1, and therefore, repeated description of the configuration and operation is omitted.
2 are used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, in FIG. 2, the same reference numerals as those in FIG. However, they are not specifically the same as the first embodiment.
In Example 2, along with the change in the focal length from the wide-angle end to the telephoto end,
Focal length f of entire system: 5.16 to 35.09
F number: 3.49-5.49
Half angle of view ω: 39.32 to 6.53
And change.
The characteristics of each optical surface are as shown in the following table (Table 3).

Each of the optical surfaces of the fourth surface, the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface, and the seventeenth surface in Table 3 is an aspheric surface, and represents the above-mentioned aspheric surface shape in each aspheric surface. The parameters related to are as follows.
Aspheric surface; fourth surface K = 0.0,
A ₄ = −4.49172 × 10 ⁻⁶ ,
A ₆ = −1.89922 × 10 ⁻⁸ ,
A ₈ = −2.51390 × 10 ⁻¹¹ ,
A ₁₀ = −3.42764 × 10 ⁻¹³
Aspherical surface; 6th surface K = 0.0,
A ₄ = 4.22736 × 10 ⁻⁵ ,
A ₆ = −3.36978 × 10 ⁻⁶ ,
A ₈ = 2.28125 × 10 ⁻⁷ ,
A ₁₀ = −7.59455 × 10 ⁻⁹
A ₁₂ = 8.48001 × ^{10 -11}

Aspherical surface; tenth surface K = 0.0,
A ₄ = −4.335735 × 10 ⁻⁴ ,
A ₆ = -1.90121 × 10 ⁻⁶ ,
A ₈ = −3.37380 × 10 ⁻⁷ ,
A ₁₀ = −3.96486 × 10 ⁻⁸
Aspherical surface; twelfth surface K = 0.0,
A ₄ = −6.885996 × 10 ⁻⁴ ,
A ₆ = 1.46020 × 10 ⁻⁵ ,
A ₈ = −9.03857 × 10 ⁻⁷ ,
A ₁₀ = 3.76431 × 10 ⁻⁸

Aspherical surface; thirteenth surface K = 0.0,
A ₄ = 3.36919 × 10 ⁻⁴ ,
A ₆ = 2.03718 × 10 ⁻⁵ ,
A ₈ = −1.332828 × 10 ⁻⁶ ,
A ₁₀ = 5.88476 × 10 ⁻⁸
Aspheric surface: 17th surface K = 0.0,
A ₄ = −9.17625 × 10 ⁻⁵ ,
A ₆ = 1.09530 × 10 ⁻⁵ ,
A ₈ = −4.30254 × 10 ⁻⁷ ,
A ₁₀ = 7.41524 × 10 ⁻⁹

A variable distance DA between the first lens group G1 and the second lens group G2, a variable distance DB between the second lens group G2 and the aperture stop S, and a variable distance between the aperture stop S and the third lens group G3. DC, the variable distance DD between the third lens group G3 and the fourth lens group G4, and the variable distance DE between the fourth lens group G4 and the optical filter OF are as shown in the following table (Table 4) along with zooming. To be changed.

Further, the values of the parameters related to the conditional expressions described above in the second embodiment are as follows.
Conditional expression numerical value ν _d , Δθ _{g, F} : as shown in Table 3 f _ap / f _W = 13.4
L _a1-a2 W / L _a1-s W = 0.538
L _a1-a2 T / L _a1-s T = 0.964
L _s-a3 W / L _a1-s W = 0.234
L _s-a3 T / L _a1-s T = 0.026
| R _3R | / f _W = 0.949
X ₁ / f _T = 0.345
X ₃ / f _T = 0.247
| F ₂ | / f ₃ = 0.686
f ₁ / f _W = 6.17
d _SW / f _T = 0.120

Therefore, the value of the parameter related to the conditional expression described in the second embodiment is within the range of the conditional expression.
9 to 11 show aberration curve diagrams of the respective aberrations in the zoom lens shown in FIG. 2 according to Example 2 described above. FIG. 9 is an aberration curve diagram at the wide angle end, and FIG. FIG. 11 is an aberration curve diagram at the telephoto end, and FIG. 11 is an aberration curve diagram at the telephoto end.
In each aberration curve diagram, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional.
According to the aberration curve diagrams of FIGS. 9 to 11, the aberration is corrected or suppressed satisfactorily by the zoom lens having the configuration shown in FIG. 2 according to the second embodiment of the present invention described above. I understand.
In this way, various aberrations can be satisfactorily corrected in the positive-negative-positive-positive four-group zoom lens, and the half angle of view at the wide-angle end is 38 degrees or more, while the angle of view is sufficiently wide. Therefore, it is possible to provide a zoom lens having a zoom ratio of 6.5 times or more, a small number of constituent elements, such as about 10, and a small size and a resolving power corresponding to an image sensor with 7 to 10 million pixels.
By providing this zoom lens, it is possible to realize a camera and a portable information terminal device that have a zooming area that can sufficiently cover a normal photographing area with a small size and high image quality.

[Example 3]
FIG. 3 shows configurations of the optical system of the zoom lens according to Example 3 of the present invention at the short focal end (wide angle end), the intermediate focal length, and the long focal end (telephoto end), respectively.
The zoom lens shown in FIG. 3 has the same basic configuration as that of the zoom lens shown in FIG. 1, and therefore, repeated description of the configuration and operation is omitted.
3 are used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, in FIG. 3, the same reference numerals as those in FIG. However, they are not specifically the same as the first embodiment.
In Example 3, along with the change in the focal length from the wide-angle end to the telephoto end,
Focal length f of entire system: 5.16 to 35.09
F number: 3.50 to 5.29
Half angle of view ω: 39.33 to 6.50
And change.
The characteristics of each optical surface are as shown in the following table (Table 5).

The optical surfaces of the fourth surface, the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface, and the seventeenth surface in Table 5 are aspherical surfaces, and are related to an expression that represents the above-mentioned aspherical shape in each aspherical surface. The parameters are as follows:
Aspheric surface; fourth surface K = 0.0,
A ₄ = −3.86254 × 10 ⁻⁶ ,
A ₆ = -2.3155 × 10 ⁻⁸ ,
A ₈ = 9.887125 × 10 ⁻¹¹ ,
A ₁₀ = −7.57988 × 10 ⁻¹³
Aspherical surface; 6th surface K = 0.0,
A ₄ = 1.456622 × 10 ⁻⁴ ,
A ₆ = −6.888560 × 10 ⁻⁶ ,
A ₈ = 3.08656 × 10 ⁻⁷ ,
A ₁₀ = −6.72175 × 10 ⁻⁹
A ₁₂ = −4.03500 × 10 ⁻¹¹ ,
A ₁₄ = 2.262201 × 10 ⁻¹²

Aspherical surface; tenth surface K = 0.0,
A ₄ = −4.85100 × 10 ⁻⁴ ,
A ₆ = −5.683898 × 10 ⁻⁶ ,
A ₈ = −4.17876 × 10 ⁻⁷ ,
A ₁₀ = −5.85888 × 10 ⁻⁸
Aspherical surface; twelfth surface K = 0.0,
A ₄ = −7.28384 × 10 ⁻⁴ ,
A ₆ = 1.77639 × 10 ⁻⁵ ,
A ₈ = −9.37789 × 10 ⁻⁷ ,
A ^₁₀ = 5.36548 × ₁₀ ^-8
Aspherical surface; thirteenth surface K = 0.0,
A ₄ = 4.78008 × 10 ⁻⁴ ,
A ₆ = 2.52291 × 10 ⁻⁵ ,
A ₈ = −1.67212 × 10 ⁻⁶ ,
A ₁₀ = 9.81679 × 10 ⁻⁸

Aspheric surface: 17th surface K = 0.0,
A ₄ = −5.442838 × 10 ⁻⁵ ,
A ₆ = 9.52406 × 10 ⁻⁶ ,
A ₈ = −3.666158 × 10 ⁻⁷ ,
A ₁₀ = 6.05533 × 10 ⁻⁹

A variable distance DA between the first lens group G1 and the second lens group G2, a variable distance DB between the second lens group G2 and the aperture stop S, and a variable distance between the aperture stop S and the third lens group G3. DC, the variable distance DD between the third lens group G3 and the fourth lens group G4, and the variable distance DE between the fourth lens group G4 and the optical filter OF are as shown in the following table (Table 6) along with zooming. To be changed.

The values of the parameters related to the conditional expressions described in the third embodiment are as follows.
Conditional numerical value ν _d , Δθ _{g, F} : as shown in Table 5 f _ap / f _W = 12.7
L _a1-a2 W / L _a1-s W = 0.545
L _{a1 −a2} T / L _a1 −s T = 0.962
L _s-a3 W / L _a1-s W = 0.244
L _s-a3 T / L _a1-s T = 0.027
| R _3R | / f _W = 0.938
X ₁ / f _T = 0.317
X ₃ / f _T = 0.217
| F ₂ | / f ₃ = 0.657
f ₁ / f _W = 5.69
d _SW / f _T = 0.117
Therefore, the value of the parameter related to the conditional expression described in the third embodiment is within the range of the conditional expression.

FIGS. 12 to 14 show aberration curve diagrams of the respective aberrations in the zoom lens shown in FIG. 3 according to Example 3 described above. FIG. 12 is an aberration curve diagram at the wide angle end, and FIG. FIG. 14 is an aberration curve diagram at a telephoto end.
In each aberration curve diagram, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional.
According to the aberration curve diagrams of FIGS. 12 to 14, the aberration is corrected or suppressed satisfactorily by the zoom lens having the configuration shown in FIG. 3 according to the third embodiment of the present invention described above. I understand.
In this way, various aberrations can be satisfactorily corrected in the positive-negative-positive-positive four-group zoom lens, and the half angle of view at the wide-angle end is 38 degrees or more, while the angle of view is sufficiently wide. Therefore, it is possible to provide a zoom lens having a zoom ratio of 6.5 times or more, a small number of constituent elements, such as about 10, and a small size and a resolving power corresponding to an image sensor with 7 to 10 million pixels.
By providing this zoom lens, it is possible to realize a camera and a portable information terminal device that have a zooming area that can sufficiently cover a normal photographing area with a small size and high image quality.

[Example 4]
FIG. 4 shows configurations of the optical system of the zoom lens according to Example 4 of the present invention at the short focal end (wide angle end), the intermediate focal length, and the long focal end (telephoto end), respectively.
The zoom lens shown in FIG. 4 has the same basic configuration as that of the zoom lens shown in FIG.
4 are used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, in FIG. 4, the same reference numerals as those in FIG. However, they are not specifically the same as the first embodiment.
In Example 4, along with the change in the focal length from the wide-angle end to the telephoto end,
Focal length f of entire system: 5.16 to 35.10
F number: 3.51-5.52
Half angle of view ω: 39.31 to 6.56
And change.
The characteristics of each optical surface are as shown in the following table (Table 7).

In Table 7, the optical surfaces of the fourth surface, the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface, and the seventeenth surface indicated by “* (asterisk)” attached to the surface number are aspherical surfaces. The parameters in the above formula representing the shape of each aspheric surface are as follows.
Aspheric surface; fourth surface K = 0.0,
A ₄ = −2.37737 × 10 ⁻⁶ ,
A ₆ = −1.32783 × 10 ⁻⁸ ,
A ₈ = 4.71055 × 10 ⁻¹¹ ,
A ₁₀ = -3.779840 × 10 ⁻¹³
Aspherical surface; 6th surface K = 0.0,
A ₄ = 5.331335 × 10 ⁻⁵ ,
A ₆ = −339028 × 10 ⁻⁶ ,
A ₈ = 1.84162 × 10 ⁻⁷ ,
A ₁₀ = −5.02309 × 10 ⁻⁹
A ₁₂ = 4.90722 × 10 ⁻¹¹

Aspherical surface; tenth surface K = 0.0,
A ₄ = −3.82769 × 10 ⁻⁴ ,
A ₆ = −4.86262 × 10 ⁻⁶ ,
A ₈ = 8.555590 × 10 ⁻⁸ ,
A ₁₀ = −3.09753 × 10 ⁻⁸
Aspherical surface; twelfth surface K = 0.0,
A ₄ = −5.446320 × 10 ⁻⁴ ,
A ₆ = 1.08094 × 10 ⁻⁵ ,
A ₈ = −5.66844 × 10 ⁻⁷ ,
A ₁₀ = 1.807292 × 10 ⁻⁸
Aspherical surface; thirteenth surface K = 0.0,
A ₄ = 4.18671 × 10 ⁻⁴ ,
A ₆ = 8.36986 × 10 ⁻⁶ ,
A ₈ = −8.57805 × 10 ⁻⁸ ,
A ₁₀ = −1.45620 × 10 ⁻⁹

Aspheric surface: 17th surface K = 0.0,
A ₄ = 2.54680 × 10 ⁻⁴ ,
A ₆ = 1.91839 × 10 ⁻⁶ ,
A ₈ = −1.47697 × 10 ⁻⁷ ,
A ₁₀ = 3.98032 × 10 ⁻⁹
Aspherical surface: 18th surface K = −52.73201

A variable distance DA between the first lens group G1 and the second lens group G2, a variable distance DB between the second lens group G2 and the aperture stop S, and a variable distance between the aperture stop S and the third lens group G3. The distance DC, the variable distance DD between the third lens group G3 and the fourth lens group G4, and the variable distance DE between the fourth lens group G4 and the optical filter OF are as shown in the following table (Table 8). It can be changed as follows.

The values of the parameters related to the conditional expressions described in the fourth embodiment are as follows.
Conditional numerical value ν _d , Δθ _{g, F} : as described in Table 7 f _ap / f _W = 11.1
L _a1-a2 W / L _a1-s W = 0.510
L _a1-a2 T / L _a1-s T = 0.964
L _s-a3 W / L _a1-s W = 0.216
L _s-a3 T / L _a1-s T = 0.026
| R _3R | / f _W = 0.942
X ₁ / f _T = 0.309
X ₃ / f _T = 0.240
| F ₂ | / f ₃ = 0.701
f ₁ / f _W = 6.27
d _SW / f _T = 0.116

Therefore, the value of the parameter related to the conditional expression described in the fourth embodiment is within the range of the conditional expression.

FIGS. 15 to 17 show aberration curve diagrams of the respective aberrations in the zoom lens shown in FIG. 4 according to Example 4 described above. FIG. 15 is an aberration curve diagram at the wide angle end, and FIG. FIG. 17 is an aberration curve diagram at a telephoto end.
In each aberration curve diagram, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional.
According to the aberration curve diagrams of FIGS. 15 to 17, the aberration is corrected or suppressed satisfactorily by the zoom lens having the configuration shown in FIG. 4 according to Example 4 of the present invention described above. I understand.
In this way, various aberrations can be satisfactorily corrected in the positive-negative-positive-positive four-group zoom lens, and the half angle of view at the wide-angle end is 38 degrees or more, while the angle of view is sufficiently wide. Therefore, it is possible to provide a zoom lens having a zoom ratio of 6.5 times or more, a small number of constituent elements, such as about 10, and a small size and a resolving power corresponding to an image sensor with 7 to 10 million pixels.
By providing this zoom lens, it is possible to realize a camera and a portable information terminal device that have a zooming area that can sufficiently cover a normal photographing area with a small size and high image quality.

[Example 5]
FIG. 5 is a cross-sectional view showing a configuration of an optical system of a zoom lens according to Example 5 of the present invention.
The upper part of FIG. 5 shows the configuration of the optical system of the zoom lens according to Example 5 of the present invention, the middle part shows the intermediate focal length, and the lower part shows the configuration at the telephoto end.
The zoom lens illustrated in FIG. 5 includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, an aperture stop S, and a seventh lens. L7, the eighth lens L8, the ninth lens L9, the tenth lens L10, the eleventh lens L11, and the optical filter OF are arranged in this order, and an image is formed behind the optical filter OF having various optical filtering functions. In this case, the first lens L1 to the third lens L3 constitute the first lens group G1, the fourth lens L4 to the sixth lens L6 constitute the second lens group G2, and the seventh lens L7 to the ninth lens. The lens L9 constitutes the third lens group G3, and the tenth lens L10 constitutes the fourth lens group G4. Each lens L9 is supported by an appropriate support frame or the like for each group optical system. Each lens group operates integrally.

  The first lens L1 is a negative meniscus lens having a convex surface facing the object side, the second lens L2 is a positive meniscus lens having a large curvature surface facing the object side, and the third lens L3 is a surface having a large curvature toward the object side. Is a positive meniscus lens. Among these, the first lens L1 and the second lens L2 are sequentially closely bonded and integrally joined to form a cemented lens, and the first lens L1 to the third lens L3 are configured. The one lens group G1 as a whole has a positive focal length, that is, positive refractive power. The fourth lens L4 is a negative meniscus lens having a convex surface facing the object side, the fifth lens L5 is a biconvex lens having a surface with a large curvature on the image side, and the sixth lens L6 is a negative lens having a convex surface facing the image surface side. It is a meniscus lens. Of these, the fifth lens L5 and the sixth lens L6 are sequentially closely bonded and integrally joined to form a cemented lens, and a second lens constituted by the fourth lens L4 to the sixth lens L6. The group G2 as a whole has a negative focal length, that is, negative refractive power. S is an aperture stop that moves during zooming.

The seventh lens L7 is a biconvex lens with a large curvature surface facing the object side, the eighth lens L8 is a biconvex lens with a large curvature surface facing the image side, and the ninth lens L9 has a large curvature toward the image side. It is a biconcave lens with its surface facing. The eighth lens L8 and the ninth lens L9 are integrally joined. The third lens G3 including the seventh lens L7 to the ninth lens L9 has a positive focal length, that is, positive refractive power as a whole.
The tenth lens L10 is a biconvex lens having a surface with a large curvature toward the object side, and the fourth lens group G4 is configured only by the tenth lens L10, and has a positive focal length, that is, a positive refractive power. Have.
The eleventh lens L11 is a negative meniscus lens having a surface with a large curvature toward the object side, and the fifth lens group G5 is configured only by the tenth lens L10, and has a negative focal length, that is, negative refractive power. Have
When changing the focal length from the wide-angle end (short focal end) to the telephoto end (long focal end), the distance between the first lens group G1 and the second lens group G2 increases, and the second lens group G2 and the second lens group G2 The distance between 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 are closer to the object side at the telephoto end than at the wide angle end. Move to be located at.

Focusing can be performed by moving the second lens group G2 or the fourth lens group G4 or moving the light receiving element.
The optical filter OF composed of parallel flat plates arranged on the most image side is a filter such as a crystal low-pass filter or an infrared cut filter.
Due to the movement of the lens groups G1 to G4 accompanying the change in focal length, the variable interval between the lens groups, that is, the most image side surface of the first lens group G1, that is, the image side surface of the third lens L3 (surface number). R5) and the distance DA between the most object side surface (surface number R6) of the second lens group G2, the most image side surface of the second lens group G2, that is, the image side surface (surface number R10) of the sixth lens L6. ) And the aperture stop S, the distance DC between the aperture stop S and the most object side surface (surface number R12) of the third lens group G3, the most image side surface of the third lens group G3, that is, the first lens surface. Distance DD between the image side surface (surface number R16) of the 9th lens L9 and the most object side surface of the fourth lens group G4, that is, the image side surface (surface number R17) of the 10th lens L10, the 4th lens group. The most image-side surface of G4, that is, the image-side surface of the tenth lens L10 (surface number R18) Spacing DE between the surface (surface number R19) on the object side of the fifth lens group G5 are changed respectively.
In Example 5, along with the change in the focal length from the wide-angle end to the telephoto end,
Focal length f of entire system: 5.16 to 35.10
F number: 3.51-5.52
Half angle of view ω: 39.31 to 6.56
And change.
The characteristics of each optical surface are as shown in the following table (Table 9).

In Table 9, the optical surfaces of the fourth surface, the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface, and the seventeenth surface, which are indicated by attaching “* (asterisk)” to the surface number, are aspherical surfaces. The parameters in the above formula representing the shape of each aspheric surface are as follows.
Aspheric surface; fourth surface K = 0.0,
A ₄ = −1.05372 × 10 ⁻⁷ ,
A ₆ = −1.08491 × 10 ⁻⁸ ,
A ₈ = 1.01529 × 10 ⁻¹⁰ ,
A ₁₀ = −4.57835 × 10 ⁻¹³
Aspherical surface; 6th surface K = 0.0,
A ₄ = −1.48758 × 10 ⁻⁵ ,
A ₆ = 8.667499 × 10 ⁻⁷ ,
A ₈ = −5.66369 × 10 ⁻⁸ ,
A ₁₀ = 6.10824 × 10 ⁻¹⁰

Aspherical surface; tenth surface K = 0.0,
A ₄ = −4.33693 × 10 ⁻⁴ ,
A ₆ = −2.885998 × 10 ⁻⁶ ,
A ₈ = -2.000782 × 10 ⁻⁷ ,
A ₁₀ = −3.442078 × 10 ⁻⁸
Aspherical surface; twelfth surface K = 0.0,
A ₄ = −7.73201 × 10 ⁻⁴ ,
A ₆ = 4.83062 × 10 ⁻⁶ ,
A ₈ = −2.60149 × 10 ⁻⁷ ,
A ₁₀ = −3.28255 × 10 ⁻⁸

Aspherical surface; thirteenth surface K = 0.0,
A ₄ = 2.36156 × 10 ⁻⁴ ,
A ₆ = 2.50539 × 10 ⁻⁶ ,
A ₈ = -2.77789 × 10 ⁻⁸ ,
A ₁₀ = −3.56150 × 10 ⁻⁸
Aspheric surface: 17th surface K = 0.0,
A ₄ = −8.58174 × 10 ⁻⁵ ,
A ₆ = 7.68289 × 10 ⁻⁶ ,
A ₈ = −3.48643 × 10 ⁻⁷ ,
A ₁₀ = 6.55532 × 10 ⁻⁹
The variable distance DA between the first lens group G1 and the second lens group G2, the variable distance DB between the second lens group G2 and the aperture stop S, and the variable distance between the aperture stop S and the third lens group G3. The distance DC, the variable distance DD between the third lens group G3 and the fourth lens group G4, and the variable distance DE between the fourth lens group G4 and the fifth lens group G5 are shown in the following table (table). 10).

The values of the parameters related to the conditional expressions described in the fifth embodiment are as follows.
Conditional numerical value ν _d , Δθ _{g, F} : as described in Table 9 f _ap / f _W = 9.51
L _a1-a2 W / L _a1-s W = 0.527
L _{a1 − a2} T / L _{a1 −s} T = 0.963
L _s-a3 W / L _a1-s W = 0.276
L _s-a3 T / L _a1-s T = 0.027
| R _3R | / f _W = 1.032
X ₁ / f _T = 0.307
X ₃ / f _T = 0.223
| F ₂ | / f ₃ = 0.624
f ₁ / f _W = 5.86
d _SW / f _T = 0.136

Therefore, the value of the parameter related to the conditional expression described in the fifth embodiment is within the range of the conditional expression.

18 to 20 show aberration curve diagrams of the respective aberrations in the zoom lens shown in FIG. 5 according to Example 5 described above. FIG. 18 is an aberration curve diagram at the wide angle end, and FIG. FIG. 20 is an aberration curve diagram at a telephoto end.
In each aberration curve diagram, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional.
According to the aberration curve diagrams of FIGS. 18 to 20, the aberration is favorably corrected or suppressed by the zoom lens having the configuration shown in FIG. 5 according to the fifth embodiment of the present invention described above. I understand.
According to the fifth embodiment, various aberrations can be satisfactorily corrected in the five positive-negative-positive-positive-positive-negative zoom lenses, and the half angle of view at the wide-angle end is sufficiently wide as 38 degrees or more. Provided is a zoom lens having a zoom ratio of 6.5 times or more, having a zoom ratio of 6.5 or more, having a small number of constituent elements of 11 and having a resolving power corresponding to an image sensor with 7 to 10 million pixels. be able to.
By providing this zoom lens, it is possible to realize a camera and a portable information terminal device that have a zooming area that can sufficiently cover a normal photographing area with a small size and high image quality.

Next, an embodiment of the present invention in which a camera (including a portable information terminal device) is configured by employing a photographing optical system as a zoom lens according to the present invention as shown in the first to fifth embodiments described above. A form is demonstrated with reference to FIGS. 21-22. FIG. 21A is a perspective view schematically showing the appearance of the retracted state of the camera as viewed from the front side, that is, the object, that is, the subject side, and FIG. 21B is a state of use of the camera as viewed from the front side. FIG. 21C is a perspective view schematically showing the appearance of the camera as seen from the back side that is the photographer side, and FIG. 22 shows the functional configuration of the camera. It is a block diagram. Although a camera is described here, a camera in which a camera function is incorporated in a personal digital assistant such as a so-called PDA (personal data assistant) or a mobile phone has recently appeared. Such a portable information terminal device also includes substantially the same functions and configuration as a camera, although the appearance is slightly different, and the photographing optical system or camera according to the present invention is included in such a portable information terminal device. It may be adopted.
As shown in FIGS. 21A, 21B, and 21C, the camera 1 includes a photographing lens 2, a shutter button 3, a zoom lever 4, a finder 5, a strobe 6, a liquid crystal monitor 7, an operation button 8, and a power switch. 9. A memory / communication card slot 10 is provided. Further, as shown in FIG. 22, the camera 1 also includes a light receiving element 12, a signal processing device 13, an image processing device 14, a central processing unit (CPU) 15, a semiconductor memory 16, a communication card 17 and the like.

The camera 1 includes a photographic lens 2 that is a photographic optical system and a light receiving element 12 as an area sensor such as a CCD (charge coupled device) imaging element. An image is read by the light receiving element 12. As the photographing lens 2, the photographing optical system according to the present invention as described in the first to fifth embodiments is used. Specifically, a lens unit is configured using a lens or the like that is an optical element that constitutes a photographing optical system as a zoom lens. This lens unit has a mechanism for holding each lens or the like so that it can be moved and operated at least for each lens group. The taking lens 2 incorporated in the camera is usually incorporated in the form of this lens unit.
The output of the light receiving element 12 is processed by the signal processing device 13 controlled by the central processing unit 15 and converted into digital image information. The image information digitized by the signal processing device 13 is subjected to predetermined image processing in the image processing device 14 also controlled by the central processing unit 15 and then recorded in the semiconductor memory 16 such as a nonvolatile memory. In this case, the semiconductor memory 16 may be a memory card loaded in the memory / communication card slot 10 or a semiconductor memory built in the camera body. On the liquid crystal monitor 7, an image being photographed can be displayed, and an image recorded in the semiconductor memory 16 can be displayed. The image recorded in the semiconductor memory 16 can also be transmitted to the outside via a communication card 17 or the like loaded in the memory / communication card slot 10.

When the camera 1 is carried, the photographing lens 2 is in a retracted state and buried in the body of the camera 1 as shown in FIG. 21A. When the user operates the power switch 9 to turn on the power, As shown in 21 (b), the lens barrel is extended and protrudes from the body of the camera 1. At this time, in the lens barrel of the photographing lens 2, the optical systems of the respective groups constituting the zoom lens are, for example, arranged at the wide-angle end. Is changed, and the zooming operation to the telephoto end can be performed. It is desirable that the optical system of the finder 5 is also scaled in conjunction with the change in the angle of view of the photographic lens 2.
In many cases, focusing is performed by half-pressing the shutter button 3. When the shutter button 3 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 16 is displayed on the liquid crystal monitor 7 or transmitted to the outside via the communication card 17 or the like, the operation button 8 is operated in a predetermined manner. The semiconductor memory 16 and the communication card 17 are used by being loaded into dedicated or general-purpose slots such as the memory / communication card slot 10 or the like.

When the photographic lens 2 is in the retracted state, the zoom lens groups do not necessarily have to be arranged on the optical axis, and if a mechanism that accommodates a plurality of optical systems in parallel is provided, Further thinning of the camera device can be realized.
In the camera device or the portable information terminal device as described above, as described above, the photographing lens 2 using the zoom lens as shown in the first to fifth embodiments is used as a photographing optical system. Can do. Accordingly, it is possible to realize a small camera device or portable information terminal device with high image quality using a light receiving element of a class of 7 to 10 million pixels.

It is sectional drawing which shows the structure of the zoom lens of Example 1 of this invention. It is sectional drawing which shows the structure of the zoom lens of Example 2 of this invention. It is sectional drawing which shows the structure of the zoom lens of Example 3 of this invention. It is sectional drawing which shows the structure of the zoom lens of Example 4 of this invention. It is sectional drawing which shows the structure of the zoom lens of Example 5 of this invention. FIG. 6 is an aberration curve diagram at the short focal point of the zoom lens according to Example 1 of the present invention. FIG. 6 is an aberration curve diagram at an intermediate focal length of the zoom lens according to the first exemplary embodiment of the present invention. FIG. 4 is an aberration curve diagram at the long focal end of the zoom lens according to the first exemplary embodiment of the present invention. It is an aberration curve figure in the short focus end of the zoom lens of Example 2 of the present invention. It is an aberration curve figure in intermediate focal length of the zoom lens of Example 2 of the present invention. It is an aberration curve figure in the long focal end of the zoom lens of Example 2 of the present invention. It is an aberration curve figure in the short focus end of the zoom lens of Example 3 of the present invention. It is an aberration curve figure in the intermediate focal length of the zoom lens of Example 3 of the present invention. It is an aberration curve figure in the long focal end of the zoom lens of Example 3 of the present invention. It is an aberration curve figure in the short focus end of the zoom lens of Example 4 of the present invention. It is an aberration curve figure in intermediate focal length of the zoom lens of Example 4 of the present invention. It is an aberration curve figure in the long focal end of the zoom lens of Example 4 of the present invention. The broken line of spherical aberration represents the sine condition. In the figure of astigmatism, the solid line represents sagittal and the broken line represents meridional. It is an aberration curve figure in the short focal end of the zoom lens of Example 5 of the present invention. It is an aberration curve figure in the intermediate focal length of the zoom lens of Example 5 of the present invention. It is an aberration curve figure in the long focal end of the zoom lens of Example 5 of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is an external view of the digital camera which shows one Embodiment as a camera (personal digital assistant device) by this invention, (a) is a perspective view of the front side at the time of carrying (when retracted), (b) is at the time of use ( The perspective view which shows a part of the front side (at the time of lens extension), (c) is a perspective view of the back side. It is a block diagram which shows the outline of the system structure of a camera apparatus.

Explanation of symbols

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens L7 7th lens L8 8th lens L9 9th lens L10 10th lens L11 11th lens OF Optical filter S Aperture stop 1 Camera 2 Shooting lens 3 Shutter button 4 Zoom lever 5 Viewfinder 6 Strobe 7 Liquid crystal monitor 8 Operation button 9 Power switch 10 Memory / communication card slot 12 Light receiving element 13 Signal processing device 14 Image processing device 15 Central processing unit 16 Semiconductor memory 17 Communication card, etc.

Claims (12)

In order from the object side, there are a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. When 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. In the zoom lens in which the distance between the third lens group and the fourth lens group is increased, and the first lens group and the third lens group move so as to be positioned closer to the object side at the telephoto end than at the wide angle end, A zoom lens, wherein the first lens group includes one negative lens and two positive lenses, the first lens group has an aspherical surface, and satisfies the following conditional expression.
ν _d > 60.0
Δθ _{g, F} > 0.003
However, ν _d represents the Abbe number of at least one positive lens in the first lens group, and Δθ _{g, F} represents the anomalous dispersion of the positive lens.
Here, anomalous dispersion [Delta] [theta] _g, and _F, the Abbe number [nu _d on the horizontal axis, the partial dispersion ratio theta _{g, F} = a _{(n g -n F) / (} n F -n C) was the vertical axis In the graph, the deviation from the standard line of the glass type when the straight line connecting the glass type K7 and the glass type F2 is taken as the standard line. _{Incidentally,} n _g, n F, _{n C,} respectively, g-line, F-line, the refractive index for the C line. 2. The zoom lens according to claim 1, wherein the aspherical surface of the first lens group is provided in a positive lens, and the positive lens provided with the aspherical surface does not satisfy the conditional expression according to claim 1. Zoom lens characterized by. The zoom lens according to claim 2, wherein the following conditional expression is satisfied.
7.0 < _fap / _fw <17.0
However, f _ap represents the focal length of the positive lens of the first lens group that satisfies the conditional expression according to claim 1, and f _w represents the focal length of the entire system at the wide angle end. 4. The zoom lens according to claim 1, wherein the first lens group includes, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side, and a surface with a large curvature on the object side. A zoom lens comprising a positive lens directed toward the object and a positive lens having a surface with a large curvature toward the object side, and the aspherical surface provided on the most positive lens on the image side. 5. The zoom lens according to claim 1, wherein an aperture stop is disposed between the second lens group and the third lens group, and the aperture stop is connected to an adjacent lens group. Is a zoom lens that moves independently. 6. The zoom lens according to claim 1, wherein the aperture stop is disposed between the second lens group and the third lens group, and the second lens group and the third lens group. Each of the lens groups has at least one aspheric surface. 7. The zoom lens according to claim 6, wherein the following conditional expression is satisfied.
0.40 <L _a1-a2 W / L _a1-s W <0.70
0.80 <L _a1-a2 T / L _a1-s T <1.00
Where L _a1-a2 W is the distance from the aspherical surface of the first lens group to the aspherical surface of the second lens group at the wide-angle end, and L _a1-s W is the non-aperture of the first lens group at the wide-angle end. The distance from the spherical surface to the aperture stop, L _a1-a2 T is the distance from the aspherical surface of the first lens group to the aspherical surface of the second lens group at the telephoto end, and L _a1-s T is the distance at the telephoto end. The distance from the aspherical surface of the first lens group to the aperture stop is expressed, and when one lens group has a plurality of aspherical surfaces, the numerical values are set for the aspherical surface closest to the aperture stop. 8. The zoom lens according to claim 6, wherein the following conditional expression is satisfied.
0.10 <Ls _-a3W / _La1-sW <0.40
0.00 <Ls _-a3T / _Lal-sT <0.20
Where L _s-a3 W is the distance from the aperture stop to the aspherical surface of the third lens group at the wide angle end, and L _s-a3 T is the aspherical surface of the third lens group from the aperture stop at the telephoto end. In the case where one lens group has a plurality of aspheric surfaces, the numerical values are set for the aspheric surfaces closest to the aperture stop. 9. The zoom lens according to claim 1, wherein the third lens group includes two positive lenses and one negative lens. 10. 10. The zoom lens according to claim 9, 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 is satisfied: lens.
0.70 <| r _3R | / f _W <1.30
Here, r _3R represents the radius of curvature of the most image side surface of the third lens group. 11. A camera comprising the zoom lens according to claim 1 as a photographing optical system. 12. A portable information terminal device comprising the zoom lens according to claim 1 as a photographing optical system of a camera function unit.

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