JP6066277B2 - Zoom lens, imaging device, and information device - Google Patents

Description

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

In recent years, instead of a conventional camera using a silver salt film, that is, a silver salt camera, it is called a digital camera or an electronic camera, and a subject image is picked up by a solid-state image pickup device such as a CCD (charge coupled device) image pickup device. However, a camera as an imaging device of a type that obtains image data of a still image (still image) or a moving image (movie image) of a subject and digitally records it in a nonvolatile semiconductor memory or the like represented by a flash memory is rapidly used. It is becoming popular.
The market for such digital cameras has become very large, and the demands of users for digital cameras have also varied. In particular, high image quality and miniaturization are always desired by users in cameras, and occupy a great demand for digital cameras by users. Therefore, a zoom lens used as a photographing lens is also required to achieve both high performance and downsizing.
Here, in terms of miniaturization, first, it is necessary to shorten the entire lens length (the distance from the lens surface closest to the object side to the image plane). It is also important to reduce the thickness of each lens group to reduce the total length when stored (carrying). Furthermore, in terms of high performance, it is necessary to have a resolving power corresponding to an image sensor of at least 10 million to 15 million pixels over the entire zoom range.

In recent years, users who desire a wide angle of view and a large aperture of a photographing lens are increasing.
There are many types of zoom lenses that can be used as a photographing lens of a digital camera. As a zoom lens suitable for miniaturization, a first lens group having a negative focal length in order from the object side, and a positive lens A second lens group having a refractive power and a third lens group having a positive refractive power are arranged, and the first lens group is changed along with the zooming from the wide-angle end (short focal end) to the telephoto end (long focal end). In some cases, the two lens groups move monotonously from the image side to the object side, and the first lens group moves so as to correct fluctuations in the image plane position due to zooming. As this type of zoom lens, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2012-042927), Patent Document 2 (Japanese Patent Laid-Open No. 2009-037092), and Patent Document 3 (Japanese Patent Laid-Open No. 2008-158320). Etc. are disclosed.

Numerical Example 4 of Patent Document 1 is a large-aperture wide-angle zoom lens having a half field angle of 51 degrees or more and a minimum F number of 2.06, but has a distortion of about -14%. If distortion is large, the amount of electronic distortion correction increases, and the resolution of the corrected image tends to decrease.
Patent Document 2 has a configuration in which the number of lenses is small, but distortion is as large as about −10%. Also, the half angle of view is 42 degrees and the minimum F number is 2.6, which is not sufficient in terms of wide angle and large aperture, and it can be said that there is room for improvement.
In Patent Document 3, distortion is suppressed to a small level, but since the half angle of view is about 32 degrees and the minimum F number is 2.77, it cannot be said that the wide angle and the large aperture are sufficient. There can be room for improvement.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a high-performance zoom lens that has a large aperture and a wide angle, and that has little distortion.

In order to achieve the above object, a zoom lens according to claim 1 is provided.
A first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged in order from the object side to the image side. In zooming from the wide-angle end to the telephoto end, zooming is performed by moving the second lens group to the object side along the optical axis, and correction of the image plane accompanying the zooming is performed. In the zoom lens performed by moving the first lens group along the optical axis,
The first lens group includes three negative lenses and one positive lens,
When zooming from the wide-angle end to the telephoto end, the diaphragm moves independently,
The focal length of the entire system at the wide-angle end is fw, the focal length of the first lens group is f1 , the distance between the following stop at the wide-angle end and the second lens group is DS2W, and the stop and the second lens group at the telephoto end. When the interval is DS2T , the following conditional expressions (1) and (2) :
−3.5 <f1 / fw <−3.0 (1)
0.8 <(DS2W−DS2T) / fw <2.0 (2)
It is characterized by satisfying.

According to the invention of claim 1,
A first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged in order from the object side to the image side. In zooming from the wide-angle end to the telephoto end, zooming is performed by moving the second lens group to the object side along the optical axis, and correction of the image plane accompanying the zooming is performed. In the zoom lens performed by moving the first lens group along the optical axis,
The first lens group includes three negative lenses and one positive lens,
When zooming from the wide-angle end to the telephoto end, the diaphragm moves independently,
The focal length of the entire system at the wide-angle end is fw, the focal length of the first lens group is f1 , the distance between the following stop at the wide-angle end and the second lens group is DS2W, and the stop and the second lens group at the telephoto end. When the interval is DS2T , the following conditional expressions (1) and (2) :
−3.5 <f1 / fw <−3.0 (1)
0.8 <(DS2W−DS2T) / fw <2.0 (2)
By satisfying the above, it is possible to provide a zoom lens that has a large aperture and a wide angle while suppressing the occurrence of distortion.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the zoom locus | trajectory accompanying the structure of the optical system of the zoom lens which concerns on the 1st Embodiment of this invention and Example (numerical example, hereafter is the same) 1, and zooming, and (a) is a wide angle end. (Wide) and (b) are cross-sectional views along the optical axis at the intermediate focal length (Mean) and (c) at the telephoto end (Tele), respectively. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Embodiment 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 6 is a diagram illustrating a configuration of an optical system of a zoom lens according to a second embodiment of the present invention and a zoom locus associated with zooming, in which (a) is a wide-angle end (Wide) and (b) is an intermediate view. It is sectional drawing along the optical axis in each of a focal distance (Mean) and (c) telephoto end (Tele). FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Embodiment 2 of the present invention shown in FIG. 5. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 2 of the present invention shown in FIG. 5. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration and coma aberration at the telephoto end of the zoom lens according to Embodiment 2 of the present invention shown in FIG. 5. It is a figure which shows the zoom locus | trajectory accompanying the structure of the optical system of the zoom lens which concerns on the 3rd Embodiment of this invention, and Example 3, and zooming, (b) is an intermediate angle (b). Focal lengths (Mean) and (c) are cross-sectional views along the optical axis at the telephoto end and (Tele), respectively. FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide-angle end of the zoom lens according to Example 3 illustrated in FIG. 9. FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 3 illustrated in FIG. 9. FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Embodiment 3 of the present invention shown in FIG. 9. FIG. 10 is a diagram illustrating a configuration of an optical system of a zoom lens according to a fourth embodiment of the present invention and a zoom locus associated with zooming, in which (a) is a wide-angle end (Wide) and (b) is an intermediate view. Focal lengths (Mean) and (c) are cross-sectional views along the optical axis at each telephoto end (Tele). FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration, and coma aberration at the short focal end (wide angle end) of the zoom lens according to Example 4 illustrated in FIG. 13; FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 4 illustrated in FIG. 13. FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Example 4 shown in FIG. 13. It is the perspective view seen from the to-be-photographed object side which shows typically the external appearance structure of the digital camera as an imaging device which concerns on the 5th Embodiment of this invention. It is the perspective view seen from the photographer side which shows typically the external appearance structure of the digital camera of FIG. FIG. 18 is a block diagram schematically illustrating a functional configuration of the digital camera in FIG. 17.

Hereinafter, the zoom lens, the imaging device, and the information device according to the first to fourth embodiments of the present invention will be described in detail with reference to the drawings based on the first to fourth embodiments. Explained. Before describing specific embodiments, first, in order to explain the basic configuration of the present invention, configurations and functions defined in the claims of the claims will be described.
The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a first lens group having a positive refractive power. When the zooming from the wide angle end to the telephoto end is performed, zooming is performed by moving the second lens group along the optical axis toward the object side. The zoom lens that corrects the image plane accompanying zooming by moving the first lens group along the optical axis has the following features.
The first lens group according to the present invention includes three negative lenses and one positive lens, and the aperture moves independently during zooming from the wide-angle end to the telephoto end. The focal length is fw, the focal length of the first lens group is f1 , the distance between the following stop and the second lens group at the wide angle end is DS2W, and the distance between the stop and the second lens group at the telephoto end is DS2T . Conditional expressions (1) , (2) :
−3.5 <f1 / fw <−3.0 (1)
0.8 <(DS2W−DS2T) / fw <2.0 (2)
Is satisfied (corresponding to claim 1).

Conditional expression (1) is a conditional expression that prescribes the power of the first lens group disposed on the object side of the stop among the lens groups constituting the zoom lens. Distortion is determined by the power of the lens and the distance from the stop, and if a lens group having a strong negative power is arranged at a position away from the stop toward the object side, negative distortion tends to occur. By using three negative lenses in the first lens group having negative refractive power, it is possible to share negative power among the negative lenses and suppress the occurrence of various aberrations.
When the upper limit of conditional expression (1) is exceeded, the power of the first lens group having negative refractive power becomes too strong, and it becomes difficult to suppress the occurrence of distortion. Further, if the power of the first lens group is increased, the influence of manufacturing errors such as decentration tends to increase, which is not preferable.
If the lower limit of conditional expression (1) is not reached, the amount of movement of the lens unit at the time of zooming becomes large, which is disadvantageous for downsizing of the entire lens length. In addition, it becomes difficult to correct spherical aberration at the telephoto end with the first lens group having negative refractive power. Further, the negative power of the first lens group becomes weak, so that it is difficult to widen the angle.

Conditional expression (2) is a conditional expression for specifying the throttle position is arranged between the first lens group and the second lens group, and is aimed at isolating the lower coma flare in the intermediate angle .
More specifically, if the lower limit of conditional expression (2) is not reached, the distance between the stop and the second lens group at the wide angle end becomes small, and the lower coma tends to become large at an intermediate angle of view, which is not preferable. Further, the distance between the first lens group having negative refractive power and the stop is increased, which is disadvantageous for suppressing negative distortion.
If the upper limit of conditional expression (2) is exceeded, the effective diameter of the first lens group can be reduced, but it is not preferable because the light rays at the maximum angle of view are also blocked, leading to insufficient peripheral light quantity. Further, if the aperture diameter of the aperture is constant regardless of zooming, the F number at the telephoto end becomes large. By making the open diameter at the telephoto end larger than that at the wide-angle end, the change in the F number accompanying zooming can be reduced, but this is not preferable because the mechanism is complicated.

Further, it is desirable that the lens closest to the object side in the first lens group is a lens having at least one aspheric surface (corresponding to claim 2) .
The first lens of the first lens group is a negative lens arranged closest to the object side from the stop. Therefore, it is advantageous to suppress negative distortion by using an aspheric surface in which the negative power becomes weaker toward the periphery of the lens arranged closest to the object side. Here, a glass molded aspherical lens may be used, but the cost in the case of using a hybrid aspherical surface can be reduced as compared with the glass molded aspherical surface.
Moreover, the radius of curvature of the object side surface of the most object side lens of the first lens group and R 11, the radius of curvature of an image side of the most object side lens of the first lens group and R 12 When the following conditional expression (3):
2.5 <(R 11 + R 12 ) / (R 11 −R 12 ) <3.0 (3)
Is preferably satisfied (corresponding to claim 3 ).
Conditional expression (3) is an expression relating to the shape of the negative lens disposed on the most object side of the first lens group.
When the upper limit of conditional expression (3) is exceeded, the curvature of the lens increases, and thus the manufacturing error sensitivity tends to increase. Further, if the curvature is increased, a hybrid lens is not preferable because it becomes difficult to process an aspherical surface.
Note that the values of the radii of curvature R11 and R12 in the molded aspherical lens when a hybrid aspherical surface is used indicate the value of the surface of the substrate (aspherical glass lens).

If the lower limit of conditional expression (3) is not reached, the curvature of a lens having negative power becomes small, and it becomes difficult to correct spherical aberration at the telephoto end, which is not preferable.
Further, when the Abbe number of the most object-side negative lens constituting the first lens group is νdn1, the following conditional expression (4):
50.0 <νdn1 (4)
Is preferably satisfied (corresponding to claim 4 ).
Conditional expression (4) is a conditional expression that prescribes the Abbe number of a single lens having a negative refractive power arranged on the most object side in the negative lens group.
If the lower limit of conditional expression (4) is not reached, correction of longitudinal chromatic aberration and lateral chromatic aberration becomes difficult, which is not preferable.
The third lens group is preferably a focus lens group including a single positive lens having an aspherical surface (corresponding to claim 5 ).
By using an aspherical surface for the focus lens group, it is possible to reduce aberration fluctuations when focusing on a short-distance object. For example, when a hybrid aspherical surface is used as the aspherical surface, the cost can be reduced compared to a glass mold aspherical surface. Further, the third lens group, which is the focus lens group, is a single lens having a positive refractive power, which is advantageous in that the moving group is reduced in weight and the AF driving speed is increased.

Further, it is desirable that the second lens constituting the first lens group is a double-sided aspheric lens (corresponding to claim 6 ).
In order to suppress distortion aberration, it is desirable to use an aspheric lens for the second lens in the first lens group. In particular, it is possible to correct distortion more satisfactorily by making both surfaces aspherical. It becomes possible.
When the focal length of the first lens group is f1, and the focal length of the second lens group is f2, the following conditional expression (5):
−1.0 <f1 / f2 <−0.7 (5)
Is preferably satisfied (corresponding to claim 7 ).
Conditional expression (5) is a conditional expression that defines the power ratio of the first lens group and the second lens group.
If the lower limit of conditional expression (5) is not reached, the power of the second lens group becomes too strong. As a result, aberration variation such as spherical aberration and coma aberration increases during zooming. Furthermore, if the power of the second lens group is increased, performance deterioration due to decentration tends to increase, which is not preferable.

When the upper limit of conditional expression (5) is exceeded, the power of the second lens group becomes too weak. This undesirably increases the amount of movement of the second lens group for zooming and increases the overall length of the lens. Alternatively, the power of the first lens group having negative power becomes too strong, the axial ray passing through the second lens group becomes high, and it is difficult to correct spherical aberration and coma aberration in the second lens group. become.
Further, an imaging apparatus including the zoom lens according to any one of the above-described embodiments can be provided as the imaging optical system (corresponding to claim 8) .
In addition, an information apparatus including the zoom lens according to any of the above-described embodiments can be provided as an imaging optical system (corresponding to claim 9 ).
Next, embodiments and specific examples of the zoom lens, the imaging apparatus, and the information apparatus according to the present invention reflecting the above-described configuration will be described in detail. The first, second, third, and fourth embodiments relate to the zoom lenses of Examples 1, 2, 3, and 4, and the fifth embodiment is shown in Examples 1-4. 1 is an embodiment of an information device such as a camera (imaging device) or a portable information terminal device according to the present invention using a zoom lens as described above as an imaging optical system.

In the embodiment showing the zoom lens according to the present invention, the configuration of the zoom lens and specific numerical examples thereof are shown. Note that the maximum image height in all of Examples 1 to 4 is 4.98 mm. In each of Examples 1 to 4, a zoom lens that has a large aperture with an F number of 1.85 and a wide angle of view with a half angle of view ω of 48.2 degrees while suppressing the occurrence of distortion is small. Can be provided.
In the description related to the following Examples 1 to 4, the following various symbols are used.
f: Focal length of the entire system F: F number ω: Half angle of view
r : radius of curvature D: spacing between surfaces Nd: refractive index νd: Abbe number K: conic constant of aspherical surface

A4: 4th-order aspheric coefficient A6: 6th-order aspheric coefficient A8: 8th-order aspheric coefficient A10: 10th-order aspheric coefficient A12: 12th-order aspheric coefficient A14: 14th-order aspheric coefficient A16: 16th-order aspherical coefficient A18: 18th-order aspherical coefficient However, the aspherical surface used here is C, the reciprocal (paraxial curvature) of the paraxial radius of curvature r , H, the height from the optical axis, and the conic constant Where K is the aspherical coefficient of each order, and X is the amount of aspherical surface in the X-axis direction.

FIG. 1 shows a configuration of an optical system of a zoom lens according to Example 1 of the first embodiment of the present invention.
The zoom lens shown in FIG. 1 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, a diaphragm S, and an optical filter F are provided. In this case, the first lens L1 to the fourth lens L4 constitute the first lens group G1, the fifth lens L5 to the tenth lens L10 constitute the second lens group G2, and the eleventh lens L11 is the first lens group G1. The three lens groups G3 are configured to be supported by a common support frame or the like appropriate for each group. For zooming or the like, the first lens group G1, the diaphragm S, the second lens group G2, and the third lens group. G3 moves independently so that the distance between the first lens group G1 and the second lens group G2 decreases and the distance between the second lens group G2 and the third lens group G3 increases. FIG. 1 schematically shows the movement trajectory of each group from the short focal length end, which is the wide-angle end, through the intermediate focal length to the long focal length end, which is the telephoto end, so that the zooming operation can also be grasped. Shown with arrows. FIG. 1 also shows the surface numbers of the optical surfaces. In addition, in order to avoid complication of explanation due to an increase in the number of digits of the reference code, each reference code for FIG. 1 is used independently for each embodiment. Therefore, even if a common reference code is attached, This is not a configuration common to the embodiments.

The parallel flat plate disposed on the image plane side of the third lens group G3 is assumed to be 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 CMOS or CCD sensor. These are collectively referred to as a filter F here. A subject image is formed behind the filter F.
In FIG. 1, the first lens group G1 is composed of a negative meniscus lens having a convex surface directed toward the object side in order from the object side to the image surface side, and a first lens L1 having a hybrid aspheric surface R3 on the image surface side. A second lens L2 made of a negative meniscus lens having a convex surface facing the object side, a third lens L3 made of a positive meniscus lens having a convex surface facing the object side, and a concave surface having a larger curvature than the image side surface on the object side 4th lens L4 which consists of a biconcave lens which faced.
The second lens group G2 is composed of a biconvex lens having a convex surface with a larger curvature than the image side on the object side, an aspheric lens having aspheric surfaces on both surfaces, and an image side on the object side. A sixth lens L6 composed of a biconvex lens having a convex surface with a larger curvature than the surface, a seventh lens L7 composed of a biconcave lens with a concave surface having a larger curvature than the object side surface on the image side, and a convex surface facing the object side An eighth lens L8 composed of a positive meniscus lens, a ninth lens L9 composed of a negative meniscus lens having a convex surface facing the object side, and a tenth lens composed of a biconvex lens having a convex surface having a larger curvature than the image side surface facing the object side. It consists of a lens L10.

Among the second lens group G2, the three lenses of the sixth lens L6, the seventh lens L7, and the eighth lens L8 are bonded closely together and are integrally joined, and are a cemented lens formed by joining the three lenses. In addition, the two lenses of the ninth lens L9 and the tenth lens L10 are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses. .
The third lens group G3 is composed of a positive meniscus lens having a convex surface directed toward the object side, and has a hybrid aspheric surface R22 on the image surface side.
Focusing is performed by moving the third lens group G3.
The optical characteristics of each optical element in Example 1 are as shown in Table 1 below.

In Table 1, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspheric surface, and the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, and Each optical surface of the 22nd surface is an aspheric surface, and the parameters of each aspheric surface in the equation (6) are as follows.
Aspherical third surface
K = 0
A4 = -6.31989E-05
A6 = 6.29238E-07
A8 = -5.57415E-09
A10 = 6.80755E-12
4th page
K = 0
A4 = 1.36792E-04
A6 = -1.30874E-06
A8 = 4.44149E-09

5th page
K = 0
A4 = 1.30744E-04
A6 = -3.30509E-06
A8 = 3.49526E-08
A10 = -1.23304E-09
A12 = 3.08432E-11
A14 = -4.50771E-13
A16 = 3.49489E-15
A18 = -1.14525E-17

11th page
K = 0
A4 = -3.36872E-05
A6 = -1.07607E-07
A8 = -7.59673E-09
A10 = 4.58012E-11
12th page
K = 0
A4 = 6.70915E-05
A6 = -4.54669E-07
22nd page
K = 0
A4 = 3.98708E-05
A6 = -6.62464E-06
A8 = 1.87096E-07
A10 = -2.43174E-09
Here, E-n represents a power of 10.

During zooming from the wide-angle end to the telephoto end, the second lens group G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first lens group G1 changes in image plane position due to zooming. Move to correct. More specifically, the distance between the first lens group G1 and the second lens group G2 is gradually decreased with the zooming from the wide angle end to the telephoto end, and the distance between the second lens group G2 and the third lens group G3. The optical system of each group is moved so as to gradually increase.
In Example 1, the focal length f of the entire optical system, the variable distance DA between the first lens group G1 and the stop S, the variable distance DB between the aperture stop S and the second lens group G2, the second The variable distance DC between the lens group G2 and the third lens group G3 and the variable distance DD between the third lens group G3 and the optical filter F are changed as shown in Table 2 along with zooming.
That is, in the first embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 4.63 to 14.95 and F = 1.85 to 3, respectively, by zooming. .45 and ω = 48.2 to 18.4. The characteristics of each optical surface are as shown in Table 2 below.

  The values corresponding to the conditional expressions (1) to (5) according to the first embodiment are as shown in Table 3 below, and satisfy the conditional expressions (1) to (5), respectively.

  2, FIG. 3 and FIG. 4 show respective aberration diagrams of spherical aberration, astigmatism, distortion aberration and coma aberration (lateral aberration) at the wide-angle end, intermediate focal length and telephoto end of Example 1. ing. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.

FIG. 5 shows the configuration of the optical system of the zoom lens according to the second embodiment of the present invention.
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, a diaphragm S, and an optical filter F are provided. In this case, the first lens L1 to the fourth lens L4 constitute the first lens group G1, the fifth lens L5 to the tenth lens L10 constitute the second lens group G2, and the eleventh lens L11 is a single lens. Constitutes the third lens group G3. The first lens group G1 to the third lens group G3 are respectively supported by a common support frame or the like that is appropriate for each group. During zooming, the first lens group G1, the diaphragm S, the second lens group G2, the second lens group G2, and the like. The third lens group G3 moves independently, the distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. FIG. 5 schematically shows the movement trajectory of each group from the short focal length end, which is the wide-angle end, through the intermediate focal length to the long focal length end, which is the telephoto end, so that the zooming operation can also be grasped. Shown with arrows. FIG. 5 also shows the surface numbers of the optical surfaces. In addition, in order to avoid complication of explanation due to an increase in the number of digits of the reference code, each reference code for FIG. 5 is used independently for each embodiment. This is not a configuration common to the embodiments.

The parallel flat plate disposed on the image plane side of the third lens group G3 is assumed to be 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 CMOS or CCD sensor. These are collectively referred to as a filter F here. A subject image is formed behind the filter F.
In FIG. 5, the first lens group G1 is composed of a negative meniscus lens having a convex surface facing the object side sequentially from the object side to the image surface side, and a first lens L1 having a hybrid aspheric surface R3 on the image surface side. A second meniscus lens composed of a negative meniscus lens having a convex surface facing the object side, an aspheric lens having aspheric surfaces formed on both surfaces, and a third lens L3 composed of a positive meniscus lens having a convex surface facing the object side. And a fourth lens L4 made of a biconcave lens having a concave surface having a larger curvature than the image side surface on the object side.
The second lens group G2 is composed of a biconvex lens having a convex surface having a larger curvature than the image side surface on the object side, and a fifth lens L5 composed of an aspheric lens having aspheric surfaces formed on both surfaces, and an image on the object side. A sixth lens L6 composed of a biconvex lens having a convex surface with a larger curvature than the surface on the side, a seventh lens L7 composed of a biconcave lens with a concave surface with a greater curvature on the image side than the surface on the object side, and a convex surface on the object side An eighth lens L8 made of a positive meniscus lens facing the lens, a ninth lens L9 made of a negative meniscus lens having a convex surface facing the object side, and a biconvex lens having a convex surface having a larger curvature than the image side surface facing the object side A tenth lens L10.

Among the second lens group G2, the three lenses of the sixth lens L6, the seventh lens L7, and the eighth lens L8 are bonded closely together and are integrally joined, and are a cemented lens formed by joining the three lenses. In addition, the two lenses of the ninth lens L9 and the tenth lens L10 are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses. .
The third lens group G3 is composed of a positive meniscus lens having a convex surface directed toward the object side, and an eleventh lens L11 having a hybrid aspheric surface R22 on the image surface side.
Focusing is performed by moving the third lens group G3.
The optical characteristics of the optical elements in Example 2 are as shown in Table 4 below.

In Table 4, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspheric surface, and the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, and Each optical surface of the 22nd surface is an aspheric surface, and the parameters of each aspheric surface in the equation (6) are as follows.
Aspherical third surface
K = 0
A4 = -5.85894E-005
A6 = 5.79122E-007
A8 = -6.09009E-009
A10 = 8.50344E-012
4th page
K = 0
A4 = 1.28761E-004
A6 = -1.36143E-006
A8 = 4.86929E-009

5th page
K = 0
A4 = 1.17006E-004
A6 = -3.33077E-006
A8 = 3.74234E-008
A10 = -1.23626E-009
A12 = 3.05372E-011
A14 = -4.48730E-013
A16 = 3.52645E-015
A18 = -1.17387E-017
11th page
K = 0
A4 = -3.61258E-005
A6 = 1.06063E-007
A8 = -4.32931E-009
A10 = 5.17997E-011

12th page
K = 0
A4 = 6.62040E-005
A6 = 1.26536E-008
22nd page
K = 0
A4 = 5.18957E-005
A6 = -6.65588E-006
A8 = 1.89405E-007
A10 = -2.56063E-009
Here, E-n represents a power of 10.

During zooming from the wide-angle end to the telephoto end, the second lens group G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first lens group G1 changes in image plane position due to zooming. Move to correct. More specifically, the distance between the first lens group G1 and the second lens group G2 is gradually decreased with the zooming from the wide angle end to the telephoto end, and the distance between the second lens group G2 and the third lens group G3. The optical system of each group is moved so as to gradually increase.
In Example 2, the focal length f of the entire optical system, the variable distance DA between the first lens group G1 and the diaphragm S, the variable distance DB between the diaphragm S and the second lens group G2, the second lens The variable distance DC between the group G2 and the third lens group G3 and the variable distance DD between the third lens group G3 and the optical filter F are changed as shown in Table 5 along with zooming.
That is, in the second embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 4.63 to 14.95 and F = 1.85 to 3, respectively, by zooming. .54 and ω = 48.2 to 18.4.

  The values corresponding to the conditional expressions (1) to (5) according to the second embodiment are as shown in the following Table 6 and satisfy the conditional expressions (1) to (5), respectively.

  FIGS. 6, 7, and 8 show aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration (lateral aberration) at the wide-angle end, intermediate focal length, and telephoto end, respectively, in Example 2. ing. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.

FIG. 9 shows a configuration of an optical system of a zoom lens according to Example 3 of the third embodiment of the present invention.
The zoom lens shown in FIG. 9 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, a diaphragm S, and an optical filter F are provided. In this case, the first lens L1 to the fourth lens L4 constitute the first lens group G1, the fifth lens L5 to the tenth lens L10 constitute the second lens group G2, and the eleventh lens L11 is a single lens. The third lens group G3 is configured to be supported by a common support frame or the like that is appropriate for each group. For zooming or the like, the first lens group G1, the diaphragm S, the second lens group G2, and the third lens group G3 are supported. The lens group G3 moves independently, the distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. FIG. 9 schematically shows the movement trajectory of each group from the short focal length end, which is the wide angle end, to the long focal length end, which is the telephoto end, in order to grasp the zooming operation. Shown with arrows. FIG. 9 also shows the surface numbers of the optical surfaces. In addition, in order to avoid complication of explanation due to an increase in the number of digits of the reference code, each reference code with respect to FIG. 9 is used independently for each embodiment. This is not a configuration common to the embodiments.

The parallel flat plate disposed on the image plane side of the third lens group G3 is assumed to be 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 CMOS or CCD sensor. These are collectively referred to as a filter F here. A subject image is formed behind the filter F.
In FIG. 9, the first lens group G1 is a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side to the image surface side, and a first lens L1 having a hybrid aspheric surface R3 on the image surface side. A second lens L2 made of a negative meniscus lens having a convex surface facing the object side, a third lens L3 made of a negative meniscus lens having a convex surface facing the image side, and a positive meniscus lens having a convex surface facing the object side. The fourth lens L4.
The second lens group G2 is composed of a biconvex lens having a convex surface having a larger curvature than the image side on the object side and an aspheric lens having aspheric surfaces on both surfaces, and an image side surface on the object side. A sixth lens L6 composed of a biconvex lens having a convex surface having a larger curvature, a seventh lens L7 composed of a biconcave lens having a concave surface having a larger curvature than the object side surface on the image side, and a convex surface directed to the object side An eighth lens L8 made of a positive meniscus lens, a ninth lens L9 made of a negative meniscus lens having a convex surface facing the object side, and a biconvex lens tenth lens L10 having a convex surface having a larger curvature than the image side surface facing the object side. It consists of.

Among the second lens group G2, the three lenses of the sixth lens L6, the seventh lens L7, and the eighth lens L8 are bonded closely together and are integrally joined, and are a cemented lens formed by joining the three lenses. In addition, the two lenses of the ninth lens L9 and the tenth lens L10 are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses. .
The third lens group G3 is composed of an eleventh lens L11 made of a positive meniscus lens having a convex surface directed toward the object side, and has a hybrid aspheric surface R22 on the image surface side.
Focusing is performed by moving the third lens group G3.
The optical characteristics of the optical elements in Example 3 are as shown in Table 7 below.

In Table 7, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspheric surface, and the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, and Each optical surface of the 22nd surface is an aspheric surface, and the parameters of each aspheric surface in the equation (6) are as follows.
Aspherical third surface
K = 0
A4 = -1.02880E-004
A6 = 1.49333E-006
A8 = -1.53031E-008
A10 = 4.13739E-011
4th page
K = 0
A4 = 2.17913E-004
A6 = -2.07563E-006
A8 = 7.89969E-009

5th page
K = 0
A4 = 2.62219E-004
A6 = -4.71891E-006
A8 = 5.01114E-008
A10 = -1.30555E-009
A12 = 3.01649E-011
A14 = -4.34073E-013
A16 = 3.40412E-015
A18 = -1.16960E-017
11th page
K = 0
A4 = -3.06358E-005
A6 = 7.72203E-008
A8 = -1.88302E-009
A10 = 4.32116E-011

12th page
K = 0
A4 = 7.20582E-005
A6 = 8.32665E-008
22nd page
K = 0
A4 = 2.53534E-005
A6 = -6.23505E-006
A8 = 1.60532E-007
A10 = -2.23559E-009
Here, E-n represents a power of 10.

During zooming from the wide-angle end to the telephoto end, the second lens group G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first lens group G1 changes in image plane position due to zooming. Move to correct. More specifically, the distance between the first lens group G1 and the second lens group G2 is gradually decreased with the zooming from the wide angle end to the telephoto end, and the distance between the second lens group G2 and the third lens group G3. The optical system of each group is moved so as to gradually increase.
In Example 3, the focal length f of the entire optical system, the variable distance DA between the first lens group G1 and the diaphragm S, the variable distance DB between the diaphragm S and the second lens group G2, the second lens The variable distance DC between the group G2 and the third lens group G3 and the variable distance DD between the third lens group G3 and the optical filter F are changed as shown in Table 8 along with zooming.
That is, in the second embodiment, the focal length f, F number F, and half angle of view ω of the entire system are f = 4.63 to 14.96 and F = 1.85 to 3, respectively, by zooming. .54 and ω = 48.2 to 18.4.

  The values corresponding to the conditional expressions (1) to (5) related to the above-described third embodiment are as shown in Table 9 below, and satisfy the conditional expressions (1) to (5), respectively.

  10, FIG. 11, and FIG. 12 show aberration diagrams of spherical aberration, astigmatism, distortion aberration, and coma aberration (lateral aberration) at the wide-angle end, intermediate focal length, and telephoto end, respectively, in Example 3. ing. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.

FIG. 13 shows the configuration of the optical system of the zoom lens according to Example 4 of the fourth embodiment of the present invention.
The zoom lens shown in FIG. 13 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, a diaphragm S, and an optical filter F are provided. In this case, the first lens L1 to the fourth lens L4 constitute the first lens group G1, the fifth lens L5 to the tenth lens L10 constitute the second lens group G2, and the eleventh lens L11 is a single lens. The third lens group G3 is configured by a common support frame that is appropriate for each group. During zooming or the like, the first lens group G1, the diaphragm S, the second lens group G2, and the third lens group G3 move independently, and the distance between the first lens group G1 and the second lens group G2 decreases, and the second The distance between the lens group G2 and the third lens group G3 is increased. FIG. 13 schematically shows the movement trajectory of each group from the short focal length end, which is the wide-angle end, to the long focal length end, which is the telephoto end, from the short focal length end that is the wide-angle end. Shown with arrows.

The parallel flat plate arranged on the image plane side of the third lens group G3 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 CMOS or CCD sensor. These are collectively referred to as a filter F here. A subject image is formed behind the filter F.
In FIG. 13, the first lens group G1 is composed of a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side to the image surface side, and a first lens L1 having a hybrid aspheric surface R3 on the image surface side. A second lens L2 composed of an aspheric lens having a negative meniscus lens having a convex surface facing the object side and an aspheric surface formed on both surfaces, and a third lens L3 composed of a negative meniscus lens having a convex surface facing the image side. And a fourth lens L4 made of a positive meniscus lens having a convex surface facing the object side.
The second lens group G2 is composed of a biconvex lens having a convex surface having a larger curvature than the image side surface on the object side, and a fifth lens L5 composed of an aspheric lens having aspheric surfaces formed on both surfaces, and an image on the object side. A sixth lens L6 composed of a biconvex lens having a convex surface with a larger curvature than the surface on the side, a seventh lens L7 composed of a biconcave lens with a concave surface with a greater curvature on the image side than the surface on the object side, and a convex surface on the object side An eighth lens L8 made of a positive meniscus lens facing the lens, a ninth lens L9 made of a negative meniscus lens having a convex surface facing the object side, and a biconvex lens having a convex surface having a larger curvature than the image side surface facing the object side And a tenth lens L10 made of an aspherical lens having an aspherical surface formed on the image plane side.

Among the second lens group G2, the three lenses of the sixth lens L6, the seventh lens L7, and the eighth lens L8 are bonded closely together and are integrally joined, and are a cemented lens formed by joining the three lenses. In addition, the two lenses of the ninth lens L9 and the tenth lens L10 are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses. .
The third lens group G3 is composed of a positive meniscus lens having a convex surface directed toward the object side, and has a hybrid aspheric surface R22 on the image surface side.
Focusing is performed by moving the third lens group G3.
The optical characteristics of the optical elements in Example 4 are as shown in Table 10 below.

In Table 10, the lens surface with the surface number indicated by attaching “* (asterisk)” to the surface number is an aspheric surface, and the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, Each optical surface of the 19th surface and the 22nd surface is aspherical, and the parameters of each aspherical surface in the equation (6) are as follows.
Aspherical third surface
K = 0
A4 = -9.88689E-005
A6 = 1.23525E-006
A8 = -1.29860E-008
A10 = 3.29568E-011
4th page
K = 0
A4 = 2.15872E-004
A6 = -2.14035E-006
A8 = 7.80003E-009

5th page
K = 0
A4 = 2.75454E-004
A6 = -4.20863E-006
A8 = 4.33950E-008
A10 = -1.30780E-009
A12 = 3.07779E-011
A14 = -4.33311E-013
A16 = 3.39125E-015
A18 = -1.16960E-017
11th page
K = 0
A4 = -3.28284E-005
A6 = 1.17396E-007
A8 = -4.58073E-009
A10 = 6.56317E-011

12th page
K = 0
A4 = 6.33588E-005
A6 = 5.88872E-008
19th page
K = 0
A4 = 2.10587E-005
A6 = 8.17545E-007
A8 = -1.17012E-008
A10 = 1.09839E-010
22nd page
K = 0
A4 = -5.65875E-006
A6 = -5.67189E-006
A8 = 1.31349E-007
A10 = -1.74788E-009
Here, E-n represents a power of 10.

During zooming from the wide-angle end to the telephoto end, the second lens group G2 mainly responsible for the zooming function moves monotonically from the image side to the object side, and the first lens group G1 changes in image plane position due to zooming. Move to correct. More specifically, as the magnification is changed from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 is gradually reduced, and the distance between the second lens group G2 and the third group optical system G3. The optical system of each group is moved so as to gradually increase.
In Example 4, the focal length f of the entire optical system, the variable distance DA between the first lens group G1 and the diaphragm S, the variable distance DB between the diaphragm S and the second lens group G2, the second lens The variable distance DC between the group G2 and the third lens group G3 and the variable distance DD between the third lens group G3 and the optical filter F are changed as shown in the following Table 11 with zooming.
That is, in Example 4, the focal length f, F number F, and half angle of view ω of the entire system are f = 4.63 to 14.95 and F = 1.85 to 3.58, respectively, by zooming. , And varies in the range of ω = 48.2 to 18.6.

  The values corresponding to the conditional expressions (1) to (5) related to the above-described fourth embodiment are as shown in the following Table 12, and satisfy the conditional expressions (1) to (5), respectively.

FIGS. 14, 15, and 16 show aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration (lateral aberration) at the wide-angle end, the intermediate focal length, and the telephoto end, respectively, in Example 4. ing. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.
According to the aberration curve diagrams of FIGS. 2 to 4, FIGS. 6 to 8, FIGS. 10 to 12, and FIGS. 14 to 16, the zoom lenses according to the first to fourth embodiments of the present invention described above. In any case, it can be seen that the aberration is corrected or suppressed satisfactorily.

[Fifth Embodiment]
Next, the zoom lens according to the present invention as described in the first to fourth embodiments and shown in the first to fourth embodiments is adopted as a photographing optical system, and the camera as an image pickup apparatus. A fifth embodiment of the present invention having the above structure will be described with reference to FIGS. 17 is a perspective view showing the appearance of the camera as seen from the front side that is the object, that is, the subject side, and FIG. 18 is a perspective view showing the appearance of the camera as seen from the back side that is the photographer side. These are block diagrams which show the function structure of a camera. Although a camera is described here, a camera in which a camera function is incorporated in a personal digital assistant such as a so-called PDA (personal data assistant) or a mobile phone has recently appeared. Such a portable information terminal device has substantially the same function and configuration as a camera, although the appearance is slightly different. The zoom lens according to the present invention is included in such a portable information terminal device (information device). It may be adopted.

As shown in FIGS. 17 and 18, the camera includes a photographing lens 101, a shutter button 102, a zoom lever 103, a finder 104, a strobe 105, a liquid crystal monitor 106, an operation button 107, a power switch 108, a memory card slot 109, and a communication card. A slot 110 and the like are provided. Furthermore, as shown in FIG. 19, the camera also includes a light receiving element 201, a signal processing device 202, an image processing device 203, a central processing unit (CPU) 204, a semiconductor memory 205, a communication card 206, and the like.
The camera includes a photographic lens 101 and a light receiving element 201 as an area sensor such as a CCD (charge coupled device) imaging device, and is an object to be photographed, that is, a subject formed by the photographic lens 101 that is a photographing optical system. The image is read by the light receiving element 201. As the photographing lens 101, a zoom lens according to the present invention (that is, defined in claims 1 to 7 ) as described in the first to fourth embodiments is used (corresponding to claims 8 and 9 ). ).

The output of the light receiving element 201 is processed by the signal processing device 202 controlled by the central processing unit 204 and converted into digital image information. The image information digitized by the signal processing device 202 is subjected to predetermined image processing in the image processing device 203 which is also controlled by the central processing unit 204 and then recorded in the semiconductor memory 205 such as a nonvolatile memory. In this case, the semiconductor memory 205 may be a memory card loaded in the memory card slot 109 or a semiconductor memory built in the camera body. The liquid crystal monitor 106 can display an image being photographed, or can display an image recorded in the semiconductor memory 205. The image recorded in the semiconductor memory 205 can also be transmitted to the outside via a communication card 206 or the like loaded in the communication card slot 110.
When the camera is carried, the taking lens 101 is in a retracted state as shown in FIG. 17 and is buried in the body of the camera. When the user operates the power switch 108 to turn on the power, the lens barrel is extended. The structure protrudes from the camera body. At this time, in the lens barrel of the photographing lens 101, each group of optical systems constituting the zoom lens has, for example, a wide-angle end (short focal end). By changing the arrangement of the group optical system, the zooming operation to the telephoto end (long focal end) can be performed. Preferably, the viewfinder 104 is also scaled in conjunction with a change in the angle of view of the taking lens 101.

In many cases, focusing is performed by half-pressing the shutter button 102. Focusing in a zoom lens composed of three negative-positive-positive groups as described in the first to fourth embodiments is performed by moving the first lens group G1 or the third lens group G3, or by a light receiving element. This can be done by moving 201. When the shutter button 102 is further pushed down to the fully depressed state, photographing is performed, and then the processing as described above is performed.
When the image recorded in the semiconductor memory 205 is displayed on the liquid crystal monitor 106 or transmitted to the outside via the communication card 206 or the like, the operation button 107 is operated in a predetermined manner. The semiconductor memory 205 and the communication card 206 are used by being loaded into dedicated or general-purpose slots such as the memory card slot 109 and the communication card slot 110, respectively.
As described above, a zoom lens as shown in Embodiments 1 to 4 can be used as a photographing optical system in the camera or the portable information terminal device as the imaging device as described above. Therefore, it is possible to provide an imaging device (digital camera) or information device that has a large aperture and a wide angle, but generates little distortion.

G1 first lens group (negative)
G2 Second lens group (positive)
G3 Third lens group (positive)
L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11
First lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, eighth lens, ninth lens, tenth lens, eleventh lens S aperture F optical filter 101 photographing Lens 102 Shutter button 103 Zoom lever 104 Viewfinder 105 Strobe 106 Liquid crystal monitor 107 Operation button 108 Power switch 109 Memory card slot 110 Communication card slot 201 Light receiving element 202 Signal processing device 203 Image processing device 204 Central processing unit (CPU)
205 Semiconductor memory 206 Communication card, etc.

JP 2012-042927 A JP 2009-037092 A JP 2008-158320 A

Claims (9)

A first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged in order from the object side to the image side. In zooming from the wide-angle end to the telephoto end, zooming is performed by moving the second lens group to the object side along the optical axis, and correction of the image plane accompanying the zooming is performed. In the zoom lens performed by moving the first lens group along the optical axis,
The first lens group includes three negative lenses and one positive lens,
When zooming from the wide-angle end to the telephoto end, the diaphragm moves independently,
The focal length of the entire system at the wide-angle end is fw, the focal length of the first lens group is f1 , the distance between the following stop at the wide-angle end and the second lens group is DS2W, and the stop and the second lens group at the telephoto end. When the interval is DS2T , the following conditional expressions (1) and (2) :
−3.5 <f1 / fw <−3.0 (1)
0.8 <(DS2W−DS2T) / fw <2.0 (2)
A zoom lens characterized by satisfying 2. The zoom lens according to claim 1, wherein the lens closest to the object side of the first lens group is a lens having at least one aspheric surface. When the radius of curvature of the object side surface of the most object side lens of the first lens group and R 11, the radius of curvature of an image side of the most object side lens of the first lens group and R 12 Conditional formula (3) below:
2.5 <(R11 + R12) / (R11-R12) <3.0 (3)
The zoom lens according to claim 1 , wherein the zoom lens satisfies the following.
However, the curvature radii R11 and R12 when the most object side lens is a hybrid aspherical lens are the curvature radii of the surface of the substrate. When the Abbe number of the most object-side negative lens constituting the first lens group is νdn1, the following conditional expression (4):
50.0 <νdn1 (4)
The zoom lens according to any one of claims 1 to 3, characterized by satisfying the. The third lens group, a single zoom lens according to any one of claims 1 to 4, characterized in that the focusing lens group and a positive lens having an aspherical surface. The zoom lens according to any one of claims 1 to 5 , wherein the second lens constituting the first lens group is a double-sided aspherical lens. When the focal length of the first lens group is f1, and the focal length of the second lens group is f2, the following conditional expression (5):
−1.0 <f1 / f2 <−0.7 (5)
The zoom lens according to any one of claims 1 to 6, characterized by satisfying the. An imaging apparatus comprising the zoom lens according to any one of claims 1 to 7 as an imaging optical system. It has an imaging function, as an imaging optical system, the information device characterized by comprising the zoom lens according to any one of claims 1 to 7.

Images