JP4905779B2 - Zoom lens - Google Patents

Description

  The present invention relates to a variable magnification optical system used for a video camera, an electronic still camera, and the like, and more particularly to a small zoom lens suitable for a surveillance camera for a dome used from a visible range to a near infrared range.

2. Description of the Related Art Conventionally, as a variable power optical system used in video cameras and electronic still cameras, zooming is performed by moving the second group along the optical axis, and the image plane is corrected by moving the first group. A group-type zoom lens is known. In such a zoom lens system, particularly in surveillance camera applications, it is required that aberration performance such as chromatic aberration be maintained well. Patent Document 1 discloses a lens configuration in which chromatic aberration is corrected in a monitoring camera lens system including a negative first group and a positive second group. Specifically, the first group has a configuration including two negative single lenses and a cemented lens made up of a negative lens and a positive lens in order from the object side. With such a configuration, it is possible to satisfactorily correct chromatic aberration from the visible region to the near-infrared region while reducing the size.
JP 2005-134877 A

  However, in recent years, even in a monitoring lens system, in addition to maintaining the aberration performance, it is required to have a high zoom ratio. In the configuration of Patent Document 1, the zoom ratio is about twice, but a higher zoom ratio (for example, three times or more) is desired. On the other hand, with the widespread use of small surveillance dome cameras, there is an increasing demand for optical systems that are small enough to fit within the dome. Furthermore, in surveillance camera applications, it is preferable that various aberrations from the visible range to the near infrared range are corrected well in each zoom range from the wide-angle end to the telephoto end. In the configuration of Patent Document 1, a cemented lens is used for the first group, which is advantageous for correcting chromatic aberration. However, when the zoom ratio is increased, the amount of aberration generated in the first group is the second group. In particular, correction of spherical aberration at the telephoto end becomes insufficient. Therefore, it is desired to realize a zoom lens system having a small size and a high zoom ratio in which various aberrations from the visible range to the near infrared range are satisfactorily corrected in each zoom range, particularly for a surveillance camera application.

  The present invention has been made in view of the above problems, and its purpose is to reduce various aberrations from the visible region to the near infrared region in each variable power range, and to make it small and highly suitable for surveillance camera applications. It is to provide a double zoom lens.

  The zoom lens according to the present invention includes, in order from the object side, a first group having negative refractive power, a stop, and a second group having positive refractive power. At the time of zooming from the wide-angle end to the telephoto end, zooming is performed by moving the second lens unit toward the object side along the optical axis, and correction of the image plane accompanying zooming is performed on the first lens group. This is done by moving along the optical axis. In particular, the first group has a four-group four-lens configuration of three single lenses having negative refractive power and one single lens having positive refractive power in order from the object side. The object side surface has a convex shape, and the absolute value of the radius of curvature of the object side surface is smaller than that of the image side surface.

  In the zoom lens according to the present invention, zooming is performed by moving the second group to the object side along the optical axis, and the image plane is thereby corrected by moving the first group. In particular, the first group is composed of four single lenses having negative, negative, negative, and positive refractive power in order from the object side, and a strong positive refractive power is disposed on the object side surface of the positive single lens. As a result, the amount of aberration generated in the first lens group is suppressed, and various aberrations in each zooming region, particularly spherical aberration at the telephoto end, are effectively suppressed while achieving miniaturization, and high zooming is easy to achieve. Become.

  The second group preferably includes a twenty-first lens having positive refractive power and a biconvex twenty-second lens in order from the object side. This is advantageous for correcting various aberrations.

Moreover, it is preferable that the following conditional expressions are satisfied. Here, mt is the paraxial imaging magnification of the second group at the telephoto end. As a result, spherical aberrations are corrected particularly well at the telephoto end, which is advantageous for high zooming.
-1.5 <mt <-1.0 (1)

  Furthermore, the three single lenses having negative refractive power in the first group may be, in order from the object side, two negative meniscus lenses having a concave surface facing the image side and one biconcave lens. preferable. This is advantageous for correcting various aberrations.

Moreover, it is preferable that the following conditional expressions are satisfied. However, ν _d14 is an Abbe number with respect to the d-line of the single lens having positive refractive power in the first group. Thereby, especially at the telephoto end, the chromatic aberration on the short wavelength side is corrected well, which is advantageous for maintaining the aberration performance from the visible range to the near infrared range.
ν _d14 <30.0 (2)

More preferably, the following conditional expression is satisfied. This is advantageous for maintaining aberration performance from the visible region to the near infrared region.
ν _d14 <25.0 (3)

  The second group includes, in order from the object side, a 21st lens having positive refractive power, a biconvex 22nd lens, and a meniscus second lens having negative refractive power and having a concave surface facing the image side. 23 lenses and a 24th lens having a positive refractive power are preferably included. This is advantageous for correcting various aberrations.

Moreover, it is preferable that the following conditional expressions are satisfied. However, ν _db is the Abbe number for at least one d-line of the 21st lens and the 22nd lens in the second group. Thereby, the occurrence of longitudinal chromatic aberration in the second group is suppressed.
ν _db > 75.0 (4)

  According to the zoom lens of the present invention, in the zoom lens of the two-group system in which zooming is performed by moving the second group along the optical axis, and the image plane is corrected by the first group. Since the group has a four-group four-lens configuration composed of three negative single lenses and one positive single lens, and a strong positive refractive power is arranged on the object side surface of the positive single lens. Various aberrations from the visible region to the near-infrared region can be satisfactorily corrected in each variable magnification region while achieving downsizing and high variable magnification. Therefore, it is possible to realize a small zoom lens system that is particularly suitable for a small dome surveillance camera.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a first configuration example of a zoom lens according to an embodiment of the present invention. This configuration example corresponds to the lens configuration of Numerical Example 1 (FIGS. 6A, 6B, and 7) described later. FIG. 2 shows a second configuration example, which corresponds to the lens configuration of Numerical Example 2 (FIGS. 8A, 8B, and 9) described later. FIG. 3 shows a third configuration example, which corresponds to a lens configuration of Numerical Example 3 (FIGS. 10A, 10B, and 11) described later. FIG. 4 shows a fourth configuration example, which corresponds to the lens configuration of Numerical Example 4 (FIGS. 12A, 12B, and 13) described later. FIG. 5 shows a fifth configuration example, which corresponds to the lens configuration of Numerical Example 5 (FIGS. 14A, 14B, and 15) described later. Since the basic configuration is the same in FIGS. 1 to 5, the following description is based on the configuration example of FIG. 1.

  In FIG. 1, the reference symbol Ri denotes the curvature radius (mm) of the i-th surface that is given a number so as to increase sequentially toward the image side (imaging side), with the surface of the component closest to the object side being first. ). Reference symbol Di indicates a surface interval (mm) between the i-th surface and the (i + 1) -th surface on the optical axis Z1. About this code | symbol Di, it shows only about the part which changes with zooming.

  This zoom lens is used for a video camera, an electronic still camera, and the like, and is particularly suitable for a small dome surveillance camera. This zoom lens includes, in order from the object side along the optical axis Z1, a first group 10 having a negative refractive power, a diaphragm St, and a second group 20 having a positive refractive power. An imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) (not shown) is disposed on the imaging plane. Between the second group 20 and the imaging device, a flat optical member CG such as a cover glass for protecting the imaging surface and an infrared cut filter is disposed according to the configuration on the camera side where the lens is mounted. .

  In the above configuration, when zooming from the wide-angle end to the telephoto end, zooming is performed by moving the second group 20 to the object side along the optical axis Z1, and the image plane is corrected accordingly. This is done by moving the first group 10 along the optical axis Z1. At this time, the first group 10 and the second group 20 move so as to draw a locus shown by a solid line in FIG. In FIG. 1, W represents the lens position at the wide-angle end, and T represents the lens position at the telephoto end.

  The first group 10 includes, in order from the object side, three single lenses having negative refractive power, an eleventh lens L11, a twelfth lens L12 and a thirteenth lens L13, and a fourteenth lens L14 having positive refractive power. It consists of 4 groups and 4 groups. In particular, in the fourteenth lens L14, the object-side surface has a convex shape, and the absolute value of the radius of curvature of the object-side surface is smaller than that of the image-side surface. The eleventh lens L11 and the twelfth lens L12 preferably have a meniscus shape with a strong concave surface facing the image side. The thirteenth lens L13 is preferably biconcave. For example, the fourteenth lens L14 has a meniscus shape with a convex surface facing the object side.

  The second group 20 preferably includes, in order from the object side, a twenty-first lens L21 having positive refractive power and a biconvex twenty-second lens L22. These subsequent lenses may include, for example, a meniscus 23rd lens L23 having negative refractive power and a concave surface facing the image side, and a 24th lens L24 having positive refractive power. . The second group 20 preferably has at least one aspheric lens. In particular, it is preferable that at least one surface of the 21st lens L21 closest to the object side has an aspherical shape.

Moreover, in order to realize high zoom ratio, it is preferable that the following conditional expression (5) is satisfied. Here, m is the paraxial imaging magnification of the second group 20.
-1.5 <m <-0.35 (5)

In particular, it is preferable that the following conditional expression is satisfied at the telephoto end. Here, mt is the paraxial imaging magnification of the second group 20 at the telephoto end.
-1.5 <mt <-1.0 (1)

Moreover, it is preferable that the following conditional expression (2) is satisfied, and it is more preferable that conditional expression (3) is satisfied. However, ν _d14 is the Abbe number with respect to the d line of the single lens L14 having positive refractive power in the first group 10.
ν _d14 <30.0 (2)
ν _d14 <25.0 (3)

Furthermore, it is preferable that the following conditional expression is satisfied. However, ν _db is an Abbe number for at least one of the 21st lens L21 and the 22nd lens L22 in the second group 20 with respect to the d line.
ν _db > 75.0 (4)

  Next, operations and effects of the zoom lens configured as described above will be described.

  In this zoom lens, zooming is performed by moving the second group 20 toward the object side along the optical axis, and the image plane is corrected by the first group 10. In particular, in the first group 10, a four-group four-lens configuration composed of four single lenses, and by appropriately setting the refractive power and surface shape of each single lens, Various aberrations, particularly spherical aberration on the telephoto side, can be corrected well while downsizing. If the first lens group 10 includes a cemented lens, for example, if the two lenses on the image side are cemented lenses, various aberrations occurring in the first lens group 10 may occur when the zoom ratio is increased. Since the aberration performance is not sufficiently maintained in each zooming region, it is difficult to achieve high zooming. On the other hand, in the present embodiment, in the first group 10, since the fourteenth lens L14 has a strong positive refractive power on the object side, the amount of aberration generated in the first group 10 can be suppressed. As a result, even when a high zoom ratio is achieved, the spherical aberration is favorably corrected particularly at the telephoto end.

  Further, in the first group 10, if two negative lenses on the object side have a meniscus shape with a concave surface facing the image side, and the subsequent negative lens is a biconcave lens, it is possible to correct spherical aberration particularly at the telephoto end. It will be advantageous.

  Furthermore, the second group 20 has at least one aspheric lens, and more particularly, at least one surface of the 21st lens L21 closest to the object side has an aspheric shape, so that spherical aberration can be corrected more effectively. Is done.

  Conditional expression (5) is an expression related to the paraxial imaging magnification of the second group 20, and contributes to high zooming. If the upper limit of conditional expression (5) is exceeded, the negative refractive power of the first group 10 will weaken, the amount of movement associated with zooming will increase, and compactification will be hindered. Exceeding the lower limit of conditional expression (5) is not preferable because the negative refractive power of the first lens group 10 is increased, and correction of spherical aberration on the telephoto side is particularly insufficient.

  Conditional expression (1) is an expression relating to the paraxial imaging magnification of the second group 20 at the telephoto end. If the upper limit of conditional expression (1) is exceeded, high zooming becomes difficult, and if the lower limit is exceeded, the negative refractive power of the first group 10 increases, and in particular, correction of spherical aberration on the telephoto side is insufficient. Therefore, it is not preferable.

  Conditional expression (2) and conditional expression (3) are expressions relating to the Abbe number with respect to the d-line of the positive lens L14 in the first group 10. Exceeding the upper limit of conditional expression (2) is not preferable because correction of chromatic aberration on the short wavelength side becomes insufficient particularly at the telephoto end, and it becomes difficult to maintain aberration performance from the visible range to the near infrared range. . Further, satisfying conditional expression (3) is advantageous in maintaining aberration performance from the visible region to the near infrared region.

  Conditional expression (4) is an expression relating to the Abbe number for at least one of the 21st lens L21 and the 22nd lens L22 in the second group 20 with respect to the d-line. When both the 21st lens L21 and the 22nd lens L22 exceed the lower limit of the conditional expression (4), the longitudinal chromatic aberration generated in the second group 20 increases, and the aberration performance from the visible range to the near infrared range is maintained. It becomes difficult.

  As described above, according to the zoom lens according to the present embodiment, in the first group 10 in particular, a four-group four-lens configuration including three negative single lenses and one positive single lens is provided. By arranging strong positive refracting power on the object side surface of the positive lens and adopting the preferred modes described above as appropriate, the zoom lens can be reduced in size and increased in magnification, and from the visible region to the near red region in each variable magnification region. Various aberrations up to the outer region are corrected well. Therefore, a small and highly variable zoom lens system suitable as a dome monitoring camera can be realized.

  Next, specific numerical examples 1 to 5 of the zoom lens according to the present embodiment will be described together based on the first example.

  As Example 1, specific lens data corresponding to the configuration of the zoom lens shown in FIG. 1 is shown in FIGS. 6 (A), 6 (B), and 7. FIG. FIG. 6A shows basic lens data, FIG. 6B shows zooming data, and FIG. 7 shows aspherical data.

  In FIG. 6A, in the field of the surface number Si, the surface of the component on the most object side is the first, and the i-th (i = 1 to 1) is attached so as to increase sequentially toward the image side. 19) shows the surface number. In the column of the curvature radius Ri, the value (mm) of the curvature radius of the i-th surface from the object side is shown in correspondence with the reference symbol Ri in FIG. Similarly, the column of the surface interval Di indicates the interval (mm) on the optical axis between the i-th surface Si and the i + 1-th surface Si + 1 from the object side. In the columns Ndj and νdj, the values of the refractive index and the Abbe number for the d-line (wavelength 587.6 nm) of the j-th (j = 1 to 9) optical element from the object side are shown. The symbol “*” attached to the left side of the surface number indicates that the lens surface has an aspheric shape, and the curvature radius Ri of the aspheric surface indicates the value of the curvature radius near the optical axis. In addition, since the 1st group 10 and the 2nd group 20 move on an optical axis with zooming, the value of surface spacing D8, D9, D17 is variable.

  In FIG. 6B, values at the wide-angle end and the telephoto end for the variable surface distances D8, D9, and D17 are shown as data relating to zoom. 6B shows the focal length f (mm) of the entire system at the wide angle end and the telephoto end, the F number (FNO.), The angle of view 2ω (ω: half angle of view), and the second group 20. The value of the paraxial imaging magnification m is also shown.

  In particular, in the zoom lens of Example 1, both surfaces (the 10th surface and the 11th surface) of the 21st lens L21 are aspherical. The zoom ratio from the wide angle end to the telephoto end is about 3.5 times. However, in Example 4 described later, the zoom ratio is about 3.0.

In FIG. 7, in the numerical values shown as aspherical data, the symbol “E” indicates that the subsequent numerical value is a “power exponent” with 10 as the base, and is represented by an exponential function with 10 as the base. Indicates that the numerical value to be multiplied with the numerical value before "E". For example, “1.0E-02” indicates “1.0 × 10 ⁻² ”.

As the aspheric surface data, the values of the respective coefficients RB _i and KA in the aspheric surface shape expression expressed by the following expression (A) are described. Z represents the length (mm) of a perpendicular line drawn from a point on the aspheric surface at a height h from the optical axis to the tangent plane (plane perpendicular to the optical axis) of the apex of the aspheric surface. As the aspheric coefficient RB _i , the third to twentieth coefficients RB _{3 to} RB ₂₀ are effectively used.
Z = C · h ² / {1+ (1−KA · C ² · h ² ) ^1/2 } + ΣRB _i · h ⁱ (A)
(I = 3 to n, n: an integer of 3 or more)
However,
Z: Depth of aspheric surface (mm)
h: Distance from the optical axis to the lens surface (height) (mm)
KA: Conic constant C: Paraxial curvature = 1 / R
(R: paraxial radius of curvature)
RB _i : i-th aspherical coefficient

  Lens data of the zoom lens according to Example 2 is shown in FIGS. 8A, 8B, and 9 in the same manner as in Example 1 above. Similarly, lens data of the zoom lens according to Example 3 are shown in FIGS. 10 (A), 10 (B), and 11. FIG. Similarly, lens data of the zoom lens according to Example 4 are shown in FIGS. 12 (A), 12 (B), and 13. FIG. Similarly, lens data of the zoom lens according to Example 5 are shown in FIGS. 14 (A), 14 (B), and 15. FIG.

  In FIG. 16, what put together the value regarding the above-mentioned conditional expression (1)-(4) about each Example is shown. As shown in FIG. 16, Examples 1, 2, and 5 are within the numerical ranges of the conditional expressions. Example 4 is outside the range of conditional expression (3).

  FIGS. 17A to 17C show spherical aberration, astigmatism, and distortion (distortion aberration) at the wide-angle end in the zoom lens according to Example 1. FIGS. FIGS. 18A to 18C show similar aberrations at the telephoto end. Each aberration diagram shows aberrations with the d-line (wavelength 587.6 nm) as a reference wavelength. The spherical aberration diagram also shows aberrations in the near infrared region with a wavelength of 880 nm. In the astigmatism diagram, the solid line indicates the sagittal direction and the broken line indicates the tangential direction. FNO. Indicates an F value, and ω indicates a half angle of view.

  Similarly, various aberrations of the zoom lens according to Example 2 are shown in FIGS. 19A to 19C (wide-angle end) and FIGS. 20A to 20C (telephoto end). Similarly, various aberrations of the zoom lens according to Example 3 are shown in FIGS. 21A to 21C (wide-angle end) and FIGS. 22A to 22C (telephoto end). Similarly, various aberrations of the zoom lens according to Example 4 are illustrated in FIGS. 23A to 23C (wide-angle end) and FIGS. 24A to 24C (telephoto end). Similarly, various aberrations of the zoom lens according to Example 5 are shown in FIGS. 25A to 25C (wide-angle end) and FIGS. 26A to 26C (telephoto end).

  As can be seen from the numerical data and aberration diagrams described above, in each example, various aberrations are corrected well, and a zoom lens suitable for a surveillance camera for a dome and capable of high zooming can be realized. .

  In addition, this invention is not limited to the said embodiment and each Example, A various deformation | transformation implementation is possible. For example, the radius of curvature, the surface interval, and the refractive index of each lens component are not limited to the values shown in the above numerical examples, and may take other values.

FIG. 1 is a lens cross-sectional view illustrating a first configuration example of a zoom lens according to an embodiment of the present invention and corresponding to Example 1; FIG. 2 is a lens cross-sectional view illustrating a second configuration example of a zoom lens according to an embodiment of the present invention and corresponding to Example 2; FIG. 9 is a lens cross-sectional view illustrating a third configuration example of a zoom lens according to an embodiment of the present invention and corresponding to Example 3; 4 is a lens cross-sectional view illustrating a fourth configuration example of a zoom lens according to an embodiment of the present invention and corresponding to Example 4; FIG. 5 is a lens cross-sectional view illustrating a fifth configuration example of a zoom lens according to an embodiment of the present invention and corresponding to Example 5. FIG. FIG. 2 is a diagram illustrating lens data of a zoom lens according to Example 1, where (A) shows basic lens data and (B) shows data related to zoom. FIG. 3 is a diagram illustrating data relating to an aspheric surface of the zoom lens according to Example 1; FIG. 6 is a diagram illustrating lens data of a zoom lens according to Example 2, where (A) shows basic lens data and (B) shows data related to zoom. FIG. 6 is a diagram illustrating data relating to an aspherical surface of a zoom lens according to Example 2. FIG. 7 is a diagram illustrating lens data of a zoom lens according to Example 3, where (A) illustrates basic lens data and (B) illustrates data related to zoom. FIG. 6 is a diagram illustrating data relating to an aspherical surface of a zoom lens according to Example 3; FIG. 10 is a diagram illustrating lens data of a zoom lens according to Example 4, where (A) illustrates basic lens data and (B) illustrates data related to zoom. FIG. 6 is a diagram illustrating data relating to an aspheric surface of a zoom lens according to Example 4; FIG. 10 is a diagram illustrating lens data of a zoom lens according to Example 5, where (A) shows basic lens data and (B) shows data related to zoom. FIG. 10 is a diagram illustrating data relating to an aspherical surface of a zoom lens according to Example 5; It is the figure which showed the value regarding a conditional expression collectively about each Example. FIG. 4 is an aberration diagram illustrating various aberrations at the wide-angle end of the zoom lens according to Example 1; (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 4 is an aberration diagram illustrating various aberrations at the telephoto end of the zoom lens according to Example 1, where (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 6 is an aberration diagram showing various aberrations at the wide-angle end of the zoom lens according to Example 2, wherein (A) shows spherical aberration, (B) shows astigmatism, and (C) shows distortion. FIG. 6 is an aberration diagram illustrating various aberrations at the telephoto end of the zoom lens according to Example 2, where (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 6 is an aberration diagram illustrating various aberrations at the wide-angle end of the zoom lens according to Example 3, where (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 6 is an aberration diagram illustrating various aberrations at the telephoto end of the zoom lens according to Example 3, where (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 7A is an aberration diagram illustrating various aberrations at the wide-angle end of the zoom lens according to Example 4; (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 7A is an aberration diagram illustrating various aberrations at the telephoto end of the zoom lens according to Example 4; (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 7A is an aberration diagram illustrating various aberrations at the wide-angle end of the zoom lens according to Example 5; (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 7A is an aberration diagram illustrating various types of aberration at the telephoto end of the zoom lens according to Example 5, where FIG. 9A illustrates spherical aberration, FIG. 9B illustrates astigmatism, and FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... 1st group, 20 ... 2nd group, CG ... Optical member, St ... Diaphragm, Ri ... Radius of curvature of i-th lens surface from object side, Di ... I-th and i + 1-th lens from object side Distance between surfaces, Z1... Optical axis.

Claims (6)

In order from the object side, a first lens unit having negative refractive power, a second lens unit having a diaphragm, a positive refractive power,
At the time of zooming from the wide-angle end to the telephoto end, zooming is performed by moving the second group toward the object side along the optical axis, and correction of the image plane accompanying the zooming is performed. It is done by moving a group along the optical axis,
The first group has a four-group four-lens configuration including three single lenses having negative refractive power and one single lens having positive refractive power in order from the object side.
The second group includes, in order from the object side, a twenty-first lens having positive refractive power, a biconvex twenty-second lens, and a meniscus twenty-third lens having negative refractive power and a concave surface facing the image side. A lens and a 24th lens having a positive refractive power,
The single lens having positive refractive power of the first group has a convex surface on the object side, and an absolute value of a radius of curvature of the object side surface is smaller than that on the image side. lens. The zoom lens according to claim 1 , further satisfying the following conditional expression:
-1.5 <mt <-1.0 (1)
However,
mt: The paraxial imaging magnification of the second group at the telephoto end. The three single lenses having negative refractive power in the first group are composed of, in order from the object side, two negative meniscus lenses having a concave surface on the image side and one biconcave lens. the zoom lens according to any one of claims 1 or 2, characterized in that. The zoom lens according to any one of claims 1 to 3 , further satisfying the following conditional expression.
ν _d14 <30.0 (2)
However,
ν _d14 : An Abbe number with respect to the d-line of a single lens having positive refractive power in the first group. Furthermore, the following conditional expressions are satisfied. The zoom lens according to claim 4 characterized by things.
ν _d14 <25.0 (3)
However,
ν _d14 : An Abbe number with respect to the d-line of a single lens having positive refractive power in the first group. Furthermore, the zoom lens according to any one of claims 1 to 5, characterized by satisfying the following conditional expression.
ν _db > 75.0 (4)
However,
ν _db : Abbe number for at least one d-line of the 21st lens and the 22nd lens in the second group.

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