JPH1152241A - Zoom lens, video camera and electronic still camera using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens having a zooming ratio of about 11.5-18 times, a small number of lenses in spite of a wide-angle and high performance. SOLUTION: A first lens group 1 has a positive refractive power, a second lens group 2 has a negative refractive power and by moving them on an optical axis, variable power action can be exerted, a third lens group 3 has a positive refractive power, a fourth lens group 4 has a positive refractive power and they can be moved on the optical axis so that an image plane fluctuated in accompany with the movements of the second lens group 2 and an object, is kept at a constant position from a reference plane, at least one surface of the respective lens groups 2-4 is aspherical surface and a focal distance at the wide-angle end fw, a half viewing angle at the wide-angle end ω, the focal distance of the first lens group f1 and the focal distance of the second lens group f2 satisfy 0.39<(fw.tanω)/(f1.|f2|)<1/2> <1.07. Consequently, spherical aberration is compensated and a sufficient back focas and a wide viewing angle are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact zoom lens having a wide angle of view (52 ° or more) and a high zoom ratio of about 11.5 to 18 times, which is used for a single-panel video camera or the like. .

[0002]

2. Description of the Related Art In recent years, demands from the market for video cameras have been diversified, and there has been a strong demand for miniaturization of imaging devices and miniaturization of lens systems. In recent years, with the spread of multimedia personal computers, inexpensive and small electronic still cameras have appeared. Furthermore, in order to enhance market competitiveness, a lens system that achieves low cost with a small number of components while maintaining high performance has been demanded. As a result, a compact, high-resolution zoom lens with a small number of lenses has been realized. There is a strong pressure.

An example of a zoom lens for a video camera has been proposed in Japanese Patent Application Laid-Open No. Hei 6-109975. This conventional video camera zoom lens will be described with reference to the drawings. FIG. 32 shows a configuration diagram of an example of a conventional zoom lens for a video camera.

Reference numeral 321 denotes a first lens group as a light condensing unit,
22 is a second lens group as a magnification section, 323 is a third lens group as a condenser section, 324 is a fourth lens group as a focus section, and 325 is equivalent to a crystal filter or a face plate of an image sensor. Glass plate, 32
Reference numeral 6 denotes an imaging plane.

The first lens group 321 fixed to the image plane has an image forming function, and the second lens group 322 moves on the optical axis.
Changes the focal length of the entire lens system by changing the magnification.
The third lens group 323, which is a fixed group, has a function of condensing divergent light generated by the second lens group, and the fourth lens group 324 that moves on the optical axis has a focusing function.

Also, the second lens group 322 during zooming
The variation of the image plane position caused by the movement is corrected so that the fourth lens group 324 moves to form an image at a fixed position, and the image plane is always kept constant.

[0007]

However, in the above-mentioned zoom lens, although the number of lenses is 10 and the zoom ratio is about 10 times, the FNo. Is 1.6 or more, it is not possible to cope with insufficient sensitivity, which is a problem when the image size is reduced. In addition, although the number of lenses is small, the overall length is relatively long and lacks compactness, and there has been a problem that the recent demand for downsizing and high performance of zoom lenses for video cameras has not been met.

Further, it has been difficult for the conventional zoom lens design technique to achieve all of a large aperture, a high magnification, a small size, and a high resolution. A zoom lens according to the present invention and a video camera and an electronic still camera using the same solve the above-mentioned conventional problems, and have a compact and high-performance zoom lens having a zoom ratio of about 11.5 to 18 times. And a video camera and an electronic still camera using the same.

[0009]

In order to achieve the above object, a zoom lens according to the present invention comprises, in order from the object side, a first lens group having a positive refractive power and fixed to an image plane; A second lens group having a refracting power and acting on the optical axis to effect a magnification change, a third lens group having a positive refracting power and fixed to an image plane, and the second lens A fourth lens group having a positive refractive power that moves on the optical axis so as to keep the image plane that fluctuates with the movement of the group and the movement of the object as a subject at a fixed position from the reference plane; The first lens group includes, in order from the object, a lens having a negative refractive power, a lens having a positive refractive power, and a meniscus lens having a positive refractive power on the object side having a convex surface. A lens having a negative refractive power, a biconcave lens, and a A lens having a positive refractive power whose convex side is the object side, at least one surface of the second lens group is aspherical, and the third lens group has a positive refractive power in order from the object side. A lens having a positive refractive power and a lens having a negative refractive power; at least one surface of the third lens group is aspheric; and the fourth lens group includes one or more lenses. At least one surface of the fourth lens group is aspherical, and has a focal length fw at the wide-angle end, a half angle of view ω at the wide-angle end, a focal length f1 of the first lens group, and a focal point of the second lens group. The distance f2 is 0.39 <(fw · tanω) / (f1 · | f2 |) ^1/2 <
1.07, and the zoom ratio (focal length at the telephoto end / focal length at the wide-angle end) is greater than 10 times.

According to the above-described zoom lens, since it has an aspherical surface, spherical aberration can be corrected. By satisfying the above expression, a sufficient back focus and a wide angle of view can be obtained.

In the zoom lens, the lens having a positive refractive power on the object side of the third lens group is a biconvex lens,
The lens having the negative refractive power has a concave surface facing the image surface side, and the refractive power p3c of the concave surface and the focal length fw at the wide-angle end satisfy a relationship of 0.37 <fw · | p3c | <0.84. Is preferred. According to the preferable zoom lens as described above, it is possible to make the zoom lens very compact while securing a sufficient F-number and back focus.

In the zoom lens, the third lens group includes, in order from the object side, a biconvex lens having a positive refractive power, a lens having a positive refractive power with a convex surface facing the object side, and And a lens having a negative refractive power and a concave surface on the image surface side, the cemented lens preferably having a negative refractive power.

The third lens group includes, in order from the object side, a biconvex lens having a positive refractive power, a lens having a positive refractive power with the convex surface facing the object side, and a negative lens with a concave surface facing the image surface side. It is preferable that a lens having a refractive power of? Is provided, and a space is provided between the lenses of the third lens group.

The focal length fw at the wide-angle end and the focal length fi (i = 1, 2, 3, 4) of the i-th lens unit are 0.11 <fw / f1 <0.83 0.66 < It is preferable to satisfy the relationship of fw / | f2 | <1.69 0.21 <fw / f3 <0.52 0.21 <fw / f4 <0.46.

According to the preferred zoom lens as described above, by satisfying the above expressions, a strong refractive power for realizing a compact zoom lens can be obtained. Also, the focal length fw at the wide-angle end and the focal length f of the i-th lens group
i (i = 1, 2, 3, 4) and the half angle of view ω at the wide angle end
And the refractive power p3c of the image-side surface of the lens having negative refractive power of the third lens group is 0.533 <(fw · tanω) / (f1 · | f2 |) ^1/2
<0.857 0.504 <fw · | p3c | <0.670 0.147 <fw / f1 <0.226 0.894 <fw / | f2 | <1.358 0.286 <fw / f3 <0 .420 0.298 <fw / f4 <0.368.

In the third lens group, the focal length f31 of the lens having a positive refractive power on the object side and the combined focal length f323 of the lens having a positive refractive power and the lens having a negative refractive power on the image plane side. Preferably satisfies the relationship of 0.34 <f31 / | f323 | <1.05. According to the preferable zoom lens as described above, it is possible to make the zoom lens very compact while securing a sufficient F-number and back focus.

The lens having a positive refractive power on the object side of the third lens group has an aspherical surface on the object side, and a local radius of curvature r311 at a diameter of 10% of the effective diameter of the lens.
And the local radius of curvature r31 at 90% of the effective diameter
9 preferably satisfies the relationship of 0.29 <r311 / r319 <1.00. According to the preferable zoom lens as described above, a sufficient aberration correction capability for realizing high resolution of the zoom lens can be obtained.

The lens having a positive refractive power on the object side of the third lens group has an aspheric surface on the image side, and has a local radius of curvature r321 at 10% of the effective diameter of the lens.
And a local radius of curvature r32 at 90% of the effective diameter
9 preferably satisfies the relationship of 0.14 <r321 / r329 <0.72. According to the preferable zoom lens as described above, a sufficient aberration correction capability for realizing high resolution of the zoom lens can be obtained.

Further, the biconcave lens of the second lens group is
The lens has an aspherical surface on the object side, and has a local radius of curvature r211 at 10% of the effective diameter of the lens, and an effective diameter of 9%.
It is preferable that the local radius of curvature r219 at the relatively large diameter satisfies the relationship of 0.10 <r211 / r219 <1.52. According to the preferable zoom lens as described above, a sufficient aberration correction capability for realizing high resolution of the zoom lens can be obtained.

The lens of the fourth lens group has an aspherical surface on the object side, and has a local radius of curvature r411 at a diameter of 10% of the effective diameter of the lens and a diameter of 90% of the effective diameter. It is preferable that the local radius of curvature r419 satisfy the relationship of 0.34 <r411 / r419 <1.03. According to the preferable zoom lens as described above, a sufficient aberration correction capability for realizing high resolution of the zoom lens can be obtained.

The lens of the fourth lens group has an aspherical surface on the image side, and has a local radius of curvature r421 at 10% of the effective diameter of the lens, and a diameter of 90% of the effective diameter. It is preferable that the local radius of curvature r429 satisfy the following relationship: 0.64 <| r421 / r429 | <1.91. According to the preferable zoom lens as described above, a sufficient aberration correction capability for realizing high resolution of the zoom lens can be obtained.

The lens having a positive refractive power on the object side of the third lens group has an aspherical surface on the object side and the image side.
The biconcave lens of the second lens group has an aspheric surface on the object side surface, the lens of the fourth lens group has an aspheric surface on the object side or image plane side, and the object side of the third lens group has an aspheric surface. The focal length f31 of the lens having a positive refractive power and the combined focal length f323 of the lens having a positive refractive power and the lens having a negative refractive power on the image plane side.
And the effective diameter on the object side of the lens having a positive refractive power on the object side is 1
A local radius of curvature r311 at a radius of 90%, a local radius of curvature r319 at a radius of 90% of the effective diameter, and a radius of 10% of the effective diameter on the image plane side of a lens having a positive refractive power on the object side. A local radius of curvature r321, a local radius of curvature r329 at 90% of the effective diameter, a radius of curvature r211 at a radius of 10% of the object-side effective diameter of the biconcave lens of the second lens group, A local radius of curvature r219 at a diameter of 90% of the diameter, and 10% of the effective diameter of the object-side lens when the lens of the fourth lens group has an aspheric surface on the object-side surface. The local radius of curvature is r411,
The local radius of curvature at the diameter of 90% of the effective diameter is r419.
A local radius of curvature r421 at 10% of the effective diameter of the image-side lens when the lens of the fourth lens group has an aspheric surface on the image-side side, and 90% of the effective diameter. Is the local radius of curvature at r 429, where 0.492 <f31 / | f323 | <0.827 0.412 <r311 / r319 <0.767 0.193 <r321 / r329 <0.689 1.040 < It is preferable to satisfy the following relationships: r211 / r219 <1.170, 0.490 <r411 / r419 <0.875, or 0.640 <| r421 / r429 | <1.470.

According to the preferred zoom lens as described above, it is possible to make the zoom lens very compact while securing a sufficient F-number and back focus, and to obtain a sufficient aberration correction capability for realizing a high resolution of the zoom lens. Further, the optical total length (distance from the most object surface of the first lens unit to the image surface) L when the air from the lens surface closest to the image surface side of the fourth lens unit to the image surface is air. , The focal length fw at the wide-angle end, and the focal length ft at the telephoto end
Preferably satisfies the relationship of 2.24 <L.fw / ft <4.7. According to the preferable zoom lens as described above, it is possible to make the zoom lens very compact while securing a sufficient aberration correction capability for realizing high resolution.

Next, a video camera according to the present invention is characterized in that one of the above-mentioned zoom lenses is used. According to the video camera as described above, a single-panel video camera having a very compact zoom ratio of about 11.5 to 18 times can be realized.

Next, an electronic still camera according to the present invention is characterized in that one of the zoom lenses is used. According to the electronic still camera as described above, an electronic still camera which is very compact and has a zoom ratio of about 11.5 to 18 times can be realized.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a zoom lens, a video camera and an electronic still camera according to the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a configuration diagram of a zoom lens according to Embodiment 1. The zoom lens according to the present embodiment includes lens groups 1 to 4 in order from the object side. The first lens group 1 has a positive refractive power and is fixed to the image plane 6. The second lens group 2 has a negative refractive power and can exert a zooming effect by moving on the optical axis. The third lens group 3 has a positive refractive power and is fixed with respect to the image plane 6.

The fourth lens group has a positive refractive power,
The image plane is moved on the optical axis so that the image plane, which fluctuates with the movement of the lens group 2 and the movement of the object, is kept at a fixed position from the reference plane. Further, a flat plate 5 equivalent to an optical low-pass filter, a face plate of an image sensor, or the like is provided between the fourth lens group 4 and the imaging surface 6.

The first lens group 1 includes, in order from the object side, a lens 1a having a negative refractive power, a lens 1b having a positive refractive power, and a meniscus lens 1c having a positive refractive power on the object side. ing. The second lens group 2 includes, in order from the object side, a lens 2a having a negative refractive power, a biconcave lens 2b, and a lens 2c having a positive refractive power on the object side joined to the biconcave lens 2b. At least one of them is aspheric.

The third lens group 3 includes, in order from the object side, a biconvex lens 3a having a positive refractive power and aspherical surfaces on both surfaces, a lens 3b having a positive refractive power on the object side and a negative refractive power. And a lens 3c.

In particular, the lens 3b having a positive refractive power and the lens 3c having a negative refractive power are cemented, and the refractive power of the lens 3a having a positive refractive power is the combined power of the lenses 3b and 3c. It is set stronger than the refractive power. With this condition,
At the same time as obtaining a sufficient back focus, it is possible to perform sufficient aberration correction while being very compact. The fourth lens group 4 is composed of a single biconvex lens, and has an aspheric surface on the object surface side.

In FIG. 1, ri (i = 1 to 17) represents the radius of curvature of the lens, and dk (k = 1 to 18) represents the thickness of the lens or the air gap between the lenses. In the present embodiment, f
When w is the focal length at the wide-angle end, f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, and ω is the half angle of view at the wide-angle end, the following expression (1) is satisfied. Is set to

Equation (1) 0.39 <(fw · tanω) / (f
1 · | f2 |) ^1/2 <1.07 Equation (1) is an equation relating to the back focus and the angle of view.
If the angle is smaller than the lower limit, the angle of view becomes wide, but sufficient back focus cannot be obtained. On the other hand, if the upper limit is exceeded, a sufficient back focus can be obtained, but a wide angle of view cannot be obtained.

In this embodiment, since the expression (1) is satisfied, a sufficient back focus and a wide angle of view can be obtained. It is more preferable that the range of the expression (1) be the range of the following expression (7).

Equation (7) 0.533 <(fw · tanω) /
(F1 · | f2 |) ^1/2 <0.857 Also, assuming that the refractive power of the image-side surface of the lens 3c having a negative refractive power is p3c and the focal length at the wide-angle end of the entire zoom lens system is fw. This embodiment satisfies the following expression (2).

Equation (2): 0.37 <fw · | p3c | <0.84 Here, the refractive power of the surface is defined as n 1, the refractive index of the medium on the entrance side to the surface, and the refraction of the medium on the exit side. Assuming that the ratio is n2 and the radius of curvature of the surface is r, this is a value obtained by (n2-n1) / r.

Equation (2) is an equation relating to the F number and the back focus, and has a close relation to the compactness of the zoom lens. When the value is smaller than the lower limit of the above conditional expression, a small F-number can be secured, but sufficient back focus cannot be obtained. On the other hand, if the upper limit is exceeded, the back focus becomes long in order to secure a sufficient F-number, and the compactness of the lens system is impaired.

In this embodiment, since equation (2) is satisfied, a very compact zoom lens can be obtained while securing a sufficient F-number and back focus. It is more preferable that the range of the expression (2) be the range of the following expression (8).

Equation (8) 0.504 <fw · | p3c | <0.670 If fi (i = 1, 2, 3, 4) is the focal length of the i-th lens group, the following equation (3) ) To (6) are satisfied.

Equation (3) 0.11 <fw / f1 <0.83 Equation (4) 0.66 <fw / | f2 | <1.69 Equation (5) 0.21 <fw / f3 <0.52 Expression (6) 0.21 <fw / f4 <0.46 Expressions (3) to (6) are conditional expressions that define the refractive power of each lens unit. Strong refracting power that achieves compactness is obtained. First
In the expression (3) relating to the refractive power of the lens group 1, if the refractive index is smaller than the lower limit, the refractive power of the first lens group 1 becomes too large, so that it becomes difficult to correct spherical aberration on the long focal length side and off-axis coma. . On the other hand, when the value exceeds the upper limit, the lens length increases, and a compact zoom lens cannot be realized.

In the equation (4) relating to the refractive power of the second lens group 2, if the value is smaller than the lower limit, the lens can be made compact. However, the Petzval sum of the entire system becomes largely negative. Can not. On the other hand, when the value exceeds the upper limit, aberration correction is easy, but the variable power system becomes long, and the entire system cannot be made compact.

In the expression (5) relating to the refractive power of the third lens group 3, if it is smaller than the lower limit, the refractive power of the third lens group 3 becomes too large, so that it is impossible to obtain a back focus for inserting a crystal or the like. In addition, it becomes difficult to correct spherical aberration. On the other hand, if the upper limit is exceeded, the combined focal length of the first lens group 1, the second lens group, and the third lens group becomes a divergent system, so that the lens outer diameter of the fourth lens group becomes large, and the Petzval of the entire system becomes large. The sum cannot be reduced.

In the equation (6) relating to the refractive power of the fourth lens unit 4, if the value is smaller than the lower limit, the image coverage range becomes narrow,
In order to obtain a desired range, it is necessary to make the lens diameter of the first lens group 1 sufficiently large, so that reduction in size and weight cannot be realized. On the other hand, if the upper limit is exceeded, aberration correction is easy,
It becomes difficult to correct the imbalance of off-axis aberrations at the time of short-range shooting and the long-range shooting.

The respective ranges of the equations (3) to (6) correspond to the following equations, respectively.
It is more preferable to set the range of (9) to (12). Equation (9) 0.147 <fw / f1 <0.226 Equation (10) 0.894 <fw / | f2 | <1.358 Equation (11) 0.286 <fw / f3 <0.420 Equation (12) 0.298 <fw / f4 <0.368 Also, the focal length f31 of the lens 3a of the third lens group 3
And the combined focal length f323 of the lens 3b and the lens 3c
Satisfies the following expression (13).

Expression (13) 0.34 <f31 / | f323 | <1.05 Expression (13) is a conditional expression relating to the back focus and the F-number. In addition, since the lens diameter of the third lens unit becomes large and the back focus becomes long, a compact zoom lens cannot be realized. If the upper limit is exceeded, sufficient F
Although the number can be secured, sufficient back focus cannot be obtained. The range of Expression (13) is more preferably the range of Expression (20) below. Expression (20) 0.492 <f31 / | f323 | <0.827 Furthermore, the aspherical surface on the object side of the lens 3a is The local radius of curvature at 10% of the effective lens diameter is r311, the local radius of curvature at 90% of the effective diameter is r319, and the local effective radius of the aspherical lens on the image plane side of the lens 3a is 10%. The local radius of curvature at the radius is r321, the local radius of curvature at 90% of the effective diameter is r329, the radius of curvature at 10% of the effective diameter of the aspherical lens on the object side of the lens 2b is r211, The local radius of curvature at the diameter of 90% of the effective diameter is r219, and the locality at the diameter of 10% of the effective diameter of the lens when the lens of the fourth lens group has an aspheric surface on the object side surface. Radius of curvature at r411, 90% of the effective diameter Tokoro curvature radius R419, also when having an aspherical surface on the image plane side, the effective diameter of the lens 1
Assuming that the local radius of curvature in the split is r421 and the local radius of curvature in 90% of the effective diameter is r429, the following equations (14) to (18) are satisfied.

Equation (14) 0.29 <r311 / r319 <1.00 Equation (15) 0.14 <r321 / r329 <0.72 Equation (16) 0.10 <r211 / r219 <1.52 Formula (17) or (18) is satisfied.

Equation (17) 0.34 <r411 / r419 <1.03 Equation (18) 0.64 <| r421 / r429 | <1.91 Equations (14) to (18) define the aspherical amount. Is a conditional expression
By satisfying this condition, sufficient aberration correction capability for realizing high resolution of the zoom lens can be obtained. In Equations (14) and (15) for the aspherical surface of the lens element closest to the object side in the third group, if the value deviates from the lower limit, the correction amount of the spherical aberration is too small. ,
Sufficient aberration performance cannot be obtained.

The local radius of locality referred to here is a value obtained by algebraically calculating based on the aspheric coefficient obtained from the sag amount of the surface shape. In the formula (16) relating to the aspheric surface of the object-side surface of the second biconcave lens from the object side in the second group, if it deviates from the lower limit and the upper limit, large coma aberration occurs at an intermediate position between wide-angle and telephoto, and flare occurs. Cause.

In equations (17) and (18) relating to the aspheric surface on the object side of the single lens of the fourth group, if the values deviate from the lower limit and the upper limit, large curvature of field and spherical aberration occur, and sufficient performance cannot be obtained. .

More preferably, each range of the formulas (14) to (18) is set to the range of the following formulas (21) to (25). Equation (21) 0.412 <r311 / r319 <0.767 Equation (22) 0.193 <r321 / r329 <0.689 Equation (23) 1.040 <r211 / r219 <1.170 Equation (24) 0 .490 <r411 / r419 <0.875 Equation (25) 0.640 <| r421 / r429 | <1.4
The relationship between the total length of the optical system and the zoom ratio in the compact and high-resolution zoom lens according to the present invention is based on the total optical length when the space between the fourth unit and the image plane is air (most of the first lens unit). Let L be the distance from the surface of the object to the image plane, and the focal length between the wide-angle end and the telephoto end (the object point is at infinity)
Are expressed as fw and ft, respectively, and are expressed by the following formulas when expressed in units of mm. Equation (26) 2.24 <L.fw / ft <4.7 In Equation (26), if the value is smaller than the lower limit, the light beam must be bent to a large extent in a short range. Sufficient aberration performance to be achieved cannot be obtained. If the upper limit is exceeded, the aberration performance will be improved, but the overall length will be longer than the magnification, resulting in a lack of compactness.

(Embodiment 2) Next, Embodiment 2 will be described. FIG. 2 shows a configuration diagram of the zoom lens according to the second embodiment. The configuration of the zoom lens according to the second embodiment is as follows.
The configuration is the same as that of the zoom lens according to the first embodiment, except that the lens 3b and the lens 3c are arranged at an air interval. The refractive power of the lens 3a is set to be stronger than the combined refractive power of the lens 3b having a positive refractive power and the lens 3c having a negative refractive power. Under these conditions, sufficient back focus can be obtained, and sufficient aberration correction can be performed while being very compact.

In FIG. 2, ri (i = 1 to 18) represents the radius of curvature of the lens, and dk (k = 1 to 19) represents the thickness of the lens or the air gap between the lenses. In the second embodiment, as in the first embodiment, the settings are made so as to satisfy the above-described equations.

According to the first and second embodiments, the aberrations are sufficiently corrected by the interaction of the lens groups, and the angle of view at the wide-angle end is about 52 ° or more, and the zoom ratio is about 11. A compact zoom lens of about 5 to 18 times can be obtained with a simple configuration.

(Embodiment 3) FIG. 30 shows a configuration diagram of an embodiment of a video camera using the zoom lens according to Embodiment 1 or 2. In this embodiment,
Zoom lens 301, low-pass filter 302, image sensor 303, and microphone 30 according to the first or second embodiment
4, a signal processing circuit 305, a viewfinder 306, an audio monitor 307, and a recording system 308. Further, additional functions may be added.

In this embodiment, by using the zoom lens according to the first or second embodiment, a single-panel video camera having a very compact zoom ratio of about 11.5 to 18 times can be obtained. did it.

(Embodiment 4) FIG. 31 is a configuration diagram of an embodiment of an electronic still camera using a zoom lens according to Embodiment 1 or 2. The zoom lens 31 according to the present embodiment is the zoom lens 31 according to the first or second embodiment.
1, a low-pass filter 312, an image sensor 313, a signal processing circuit 313, a liquid crystal monitor 315, and a recording system 316. The recording system 316 has a function of recording shooting conditions and the like in addition to the subject video. Further, additional functions may be added.

In this embodiment, by using the zoom lens according to the first or second embodiment, an electronic still camera which is very compact and has a zoom ratio of about 11.5 to 18 can be realized. .

[0058]

(Example 1) In Example 1, the zoom lens according to Embodiment 1 was used (the same applies to Examples 2 to 8 below). When the radius of curvature of the lens is r (mm), the thickness of the lens or the air gap between the lenses is d (mm), the refractive index of each lens for the d-line is n, and the Abbe number of each lens for the d-line is ν. , Each value is shown in Table 1 below.

[0059]

[Table 1]

The aspheric shape is defined by the following equation (the same applies to the following Examples 2 to 9).

[0061]

(Equation 1)

Here, Z is the distance from the aspherical vertex to a point on the aspheric surface at a height from the optical axis of Y, Y is the height from the optical axis, and C is the curvature (1 / r) of the aspherical vertex. ) And K are conical constants, and D, E and F are aspherical coefficients.

The eighth, eleventh, twelfth and sixteenth surfaces are aspherical surfaces (the same applies to the following Examples 2 to 7), and their aspherical surface coefficients are shown in Table 2 below.

[0064]

[Table 2]

Next, as an example of the air gap that can be changed by zooming, the value of the air gap (mm) corresponding to each surface when the object point is at infinity is shown in Table 3 below. From this table, the standard position is the zoom position where the magnification borne by the second lens unit is 1. Note that f (mm), F / No, and ω are the focal length, F number, and half angle of view at the wide-angle end and the standard position, respectively at the telephoto end (the same applies to Examples 2 to 9 below).

[0066]

[Table 3]

The respective set values of the first embodiment in the ranges shown in the expressions (1) to (6), (13) to (17) and (26) are shown below. Equation (1) (fw · tanω) / (f1 || f2 |) ^1/2 =
0.8162 Equation (2) fw · | p3c | = 0.532 Equation (3) fw / f1 = 0.215 Equation (4) fw / | f2 | = 1.223 Equation (5) fw / f3 = 0. 384 Equation (6) fw / f4 = 0.350 Equation (13) f31 / | f323 | = 0.788 Equation (14) r311 / r319 = 0.515 Equation (15) r321 / r329 = 0.568 Equation (16) ) r211 / r219 = 1.108 Equation (17) r411 / r419 = 0.592 Equation (26) L · fw / ft = 3.513 FIGS. 3 to 5 show the aspherical zoom of this embodiment shown in Table 1. 4 shows the aberration performance of the lens. In FIGS. 3 to 5, (a)
Is a diagram of spherical aberration, a solid line indicates a value for the d-line, and a dotted line indicates a sine condition. (B) is a diagram of astigmatism, where a solid line indicates sagittal field curvature and a dotted line indicates meridional field curvature. Further, (c) shows distortion. (D) is a diagram of the axial aberration, in which the solid line shows the value for the d line, the dotted line shows the value for the F line, and the broken line shows the value for the C line. (E) is a diagram of the chromatic aberration of magnification, where the dotted line shows the value for the F line and the broken line shows the value for the C line. The above (a)-
The description of (d) is the same in FIGS.

From the results shown in FIGS. 3 to 5, it can be seen that the zoom lens of Example 1 has good optical performance. (Example 2) Table 4 shows the values of the radius of curvature r of the lens, the thickness of the lens or the air gap d between the lenses, the refractive index n of each lens for the d-line, and the Abbe number ν of each lens for the d-line. Shown in

[0069]

[Table 4]

The aspherical coefficients of each aspherical surface are shown in Table 5 below.
Shown in

[0071]

[Table 5]

Next, as an example of the air spacing that can be changed by zooming, the values when the object point is at infinity are shown in Table 6 below.

[0073]

[Table 6]

The respective set values of the second embodiment in the ranges shown in the expressions (1) to (6), (13) to (17) and (26) are shown below. Equation (1) (fw · tanω) / (f1 || f2 |) ^1/2 =
0.766 Equation (2) fw · | p3c | = 0.568 Equation (3) fw / f1 = 0.205 Equation (4) fw / | f2 | = 1.275 Equation (5) fw / f3 = 0. 390 Equation (6) fw / f4 = 0.325 Equation (13) f31 / | f323 | = 0.646 Equation (14) r311 / r319 = 0.624 Equation (15) r321 / r329 = 0.604 Equation (16) ) r211 / r219 = 1.124 Equation (17) r411 / r419 = 0.334 Equation (26) L · fw / ft = 3.419 FIGS. 6 to 8 show the aspherical zoom of the present embodiment shown in Table 4. 4 shows the aberration performance of the lens. The results shown in FIGS. 6 to 8 indicate that the zoom lens of Example 2 has good optical performance.

(Embodiment 3) The values of the radius of curvature r of the lens, the thickness of the lens or the air gap d between the lenses, the refractive index n of each lens for the d line, and the Abbe number ν of each lens for the d line are as follows. Is shown in Table 7.

[0076]

[Table 7]

The aspherical coefficients of each aspherical surface are shown in Table 8 below.
Shown in

[0078]

[Table 8]

Next, as an example of the air spacing that can be changed by zooming, the values when the object point is at infinity are shown in Table 9 below.

[0080]

[Table 9]

The respective set values of the third embodiment in the ranges shown in the expressions (1) to (6), (13) to (17) and (26) are shown below. Equation (1) (fw · tanω) / (f1 || f2 |) ^1/2 =
0.754 Equation (2) fw · | p3c | = 0.617 Equation (3) fw / f1 = 0.199 Equation (4) fw / | f2 | = 1.293 Equation (5) fw / f3 = 0. 399 Equation (6) fw / f4 = 0.325 Equation (13) f31 / | f323 | = 0.684 Equation (14) r311 / r319 = 0.719 Equation (15) r321 / r329 = 0.117 Equation (16) ) r211 / r219 = 1.178 Formula (17) r411 / r419 = 0.826 Formula (26) L · fw / ft = 3.235 FIGS. 9 to 11 show the aspherical zoom of the present embodiment shown in Table 7. 4 shows the aberration performance of the lens. 9 to 11 show that the zoom lens of Example 3 has good optical performance.

(Embodiment 4) The values of the radius of curvature r of the lens, the thickness of the lens or the air gap d between the lenses, the refractive index n of each lens for the d-line, and the Abbe number ν of each lens for the d-line are as follows. Is shown in Table 10.

[0083]

[Table 10]

The aspherical coefficients of each aspherical surface are shown in Table 1 below.
It is shown in FIG.

[0085]

[Table 11]

Next, as an example of the air spacing that can be changed by zooming, the values when the object point is at infinity are shown in Table 12 below.

[0087]

[Table 12]

The set values of the fourth embodiment in the ranges shown in the expressions (1) to (6), (13) to (17) and (26) are shown below. Equation (1) (fw · tanω) / (f1 || f2 |) ^1/2 =
0.637 Equation (2) fw · | p3c | = 0.622 Equation (3) fw / f1 = 0.171 Equation (4) fw / | f2 | = 1.018 Equation (5) fw / f3 = 0. 346 Equation (6) fw / f4 = 0.319 Equation (13) f31 / | f323 | = 0.636 Equation (14) r311 / r319 = 0.626 Equation (15) r321 / r329 = 0.331 Equation (16) ) r211 / r219 = 1.087 Equation (17) r411 / r419 = 0.807 Equation (26) L · fw / ft = 3.348 FIGS. 12 to 14 show the aspherical zoom of the present embodiment shown in Table 10. 4 shows the aberration performance of the lens. The results shown in FIGS. 12 to 14 show that the zoom lens of Example 4 has good optical performance.

(Embodiment 5) The values of the radius of curvature r of the lens, the thickness of the lens or the air gap d between the lenses, the refractive index n of each lens for the d line, and the Abbe number ν of each lens for the d line are as follows. Is shown in Table 13.

[0090]

[Table 13]

The aspherical surface coefficients of each aspherical surface are shown in Table 1 below.
It is shown in FIG.

[0092]

[Table 14]

Next, as an example of the air spacing that can be changed by zooming, the values when the object point is at infinity are shown in Table 15 below.

[0094]

[Table 15]

The respective set values of the fifth embodiment in the ranges shown in the expressions (1) to (6), (13) to (17) and (26) are shown below. Equation (1) (fw · tanω) / (f1 || f2 |) ^1/2 =
0.563 Equation (2) fw · | p3c | = 0.598 Equation (3) fw / f1 = 0.156 Equation (4) fw / | f2 | = 0.942 Equation (5) fw / f3 = 0. 329 Equation (6) fw / f4 = 0.321 Equation (13) f31 / | f323 | = 0.720 Equation (14) r311 / r319 = 0.640 Equation (15) r321 / r329 = 0.635 Equation (16) ) r211 / r219 = 1.096 Equation (17) r411 / r419 = 0.834 Equation (26) L · fw / ft = 3.615 FIGS. 15 to 17 show the aspherical zoom of the present embodiment shown in Table 13. 4 shows the aberration performance of the lens. The results shown in FIGS. 15 to 17 indicate that the zoom lens of Example 5 has good optical performance.

(Embodiment 6) The values of the radius of curvature r of the lens, the thickness of the lens or the air gap d between the lenses, the refractive index n of each lens for the d line, and the Abbe number ν of each lens for the d line are as follows. Is shown in Table 16.

[0097]

[Table 16]

The aspherical coefficients of each aspherical surface are shown in Table 1 below.
FIG.

[0099]

[Table 17]

Next, as an example of the air spacing that can be changed by zooming, the values when the object point is at infinity are shown in Table 18 below.

[0101]

[Table 18]

The respective set values of the sixth embodiment in the ranges shown in the equations (1) to (6), (13) to (17) and (26) are shown below. Equation (1) (fw · tanω) / (f1 || f2 |) ^1/2 =
0.682 Equation (2) fw · | p3c | = 0.605 Equation (3) fw / f1 = 0.164 Equation (4) fw / | f2 | = 0.997 Equation (5) fw / f3 = 0. 338 Equation (6) fw / f4 = 0.304 Equation (13) f31 / | f323 | = 0.720 Equation (14) r311 / r319 = 0.625 Equation (15) r321 / r329 = 0.605 Equation (16) ) r211 / r219 = 1.084 Equation (17) r411 / r419 = 0.799 Equation (26) L · fw / ft = 3.064 FIGS. 18 to 20 show the aspherical surface zoom of this embodiment shown in Table 16. 4 shows the aberration performance of the lens. The results shown in FIGS. 18 to 20 indicate that the zoom lens of Example 6 has good optical performance.

(Embodiment 7) The values of the radius of curvature r of the lens, the thickness of the lens or the air gap d between the lenses, the refractive index n of each lens for the d-line, and the Abbe number ν of each lens for the d-line are as follows. Is shown in Table 19.

[0104]

[Table 19]

The aspherical coefficients of each aspherical surface are shown in Table 2 below.
0 is shown.

[0106]

[Table 20]

Next, as an example of the air spacing that can be changed by zooming, the values when the object point is at infinity are shown in Table 21 below.

[0108]

[Table 21]

The respective set values of the seventh embodiment in the ranges shown in the expressions (1) to (6), (13) to (17) and (26) are shown below. Equation (1) (fw · tanω) / (f1 || f2 |) ^1/2 =
0.654 Equation (2) fw · | p3c | = 0.623 Equation (3) fw / f1 = 0.166 Equation (4) fw / | f2 | = 1.005 Equation (5) fw / f3 = 0. 341 Equation (6) fw / f4 = 0.320 Equation (13) f31 / | f323 | = 0.722 Equation (14) r311 / r319 = 0.624 Equation (15) r321 / r329 = 0.593 Equation (16) ) r211 / r219 = 1.124 Equation (17) r411 / r419 = 0.779 Equation (26) L · fw / ft = 3.353 FIGS. 21 to 23 show the aspherical zoom of the present embodiment shown in Table 19 of this embodiment. 4 shows the aberration performance of the lens. The results shown in FIGS. 21 to 23 show that the zoom lens of Example 7 has good optical performance.

(Embodiment 8) The values of the radius of curvature r of the lens, the thickness of the lens or the air gap d between the lenses, the refractive index n of each lens for the d-line, and the Abbe number ν of each lens for the d-line are as follows. Is shown in Table 22 below.

[0111]

[Table 22]

In the eighth embodiment, unlike the first to seventh embodiments, the eighth, eleventh, twelfth and seventeenth surfaces are aspherical, and the aspherical coefficients of each aspherical surface are shown in Table 23 below. Show.

[0113]

[Table 23]

Next, as an example of the air spacing that can be changed by zooming, the values when the object point is at infinity are shown in Table 24 below.

[0115]

[Table 24]

The above formulas (1) to (6), (13) to (16), (18) and
The respective set values of the eighth embodiment in the range shown in (26) are shown below. Equation (1) (fw · tanω) / (f1 || f2 |) ^1/2 =
0.673 Equation (2) fw · | p3c | = 0.611 Equation (3) fw / f1 = 0.166 Equation (4) fw / | f2 | = 1.012 Equation (5) fw / f3 = 0. 336 Equation (6) fw / f4 = 0.302 Equation (13) f31 / | f323 | = 0.705 Equation (14) r311 / r319 = 0.699 Equation (15) r321 / r329 = 0.275 Equation (16) ) r211 / r219 = 1.043 Formula (18) r421 / r429 = −0.675 Formula (26) L · fw / ft = 3.337 FIGS. 24 to 26 show the aspheric surfaces of the present embodiment shown in Table 22. 9 illustrates aberration performance of the zoom lens. The results shown in FIGS. 24 to 26 show that the zoom lens of Example 8 has good optical performance.

Example 9 In Example 9, the zoom lens according to Embodiment 2 was used. The radius of curvature r of the lens,
Table 25 shows the values of the thickness of the lenses or the air gap d between the lenses, the refractive index n of each lens for the d-line, and the Abbe number ν of each lens for the d-line.

[0118]

[Table 25]

The eighth, eleventh, twelfth, and seventeenth surfaces in FIG. 2 are aspherical surfaces, and the aspherical surface coefficients of each aspherical surface are shown in Table 26 below.

[0120]

[Table 26]

Next, as an example of the air interval that can be changed by zooming, the values when the object point is at infinity are shown in Table 27 below.

[0122]

[Table 27]

The respective set values of the eighth embodiment in the ranges shown in the equations (1) to (6), (13) to (17) and (26) are shown below. Equation (1) (fw · tanω) / (f1 || f2 |) ^1/2 =
0.624 Equation (2) fw · | p3c | = 0.638 Equation (3) fw / f1 = 0.175 Equation (4) fw / | f2 | = 1.040 Equation (5) fw / f3 = 0. 354 Equation (6) fw / f4 = 0.322 Equation (13) f31 / | f323 | = 0.657 Equation (14) r311 / r319 = 0.609 Equation (15) r321 / r329 = 0.656 Equation (16) ) r211 / r219 = 1.054 Equation (17) r411 / r419 = 0.761 Equation (26) L fw / ft = 3.375 Figs. 27 to 29 show the aspherical zoom of the present embodiment shown in Table 25. 4 shows the aberration performance of the lens. The results shown in FIGS. 27 to 29 indicate that the zoom lens of Example 9 has good optical performance.

The zoom ratio in each of the above embodiments is 12.
84 (Example 1) to 16.53 (Example 6). These values indicate that the zoom ratio is the zoom interval (d5,
The fine adjustment of d10, d16, d18) can be changed by about ± 10% with almost no change in the aberration characteristic.

[0125]

As described above, according to the zoom lens of the present invention, ten compact and high-performance aspherical zoom lenses having an F-number of about 1.8 and a zoom ratio of about 11.5 to 18 times are provided. With a small number of lenses.

According to the video camera of the present invention, since the zoom lens of the present invention is used, a compact, lightweight and high-performance video camera can be realized. Also,
According to the electronic still camera of the present invention, since the zoom lens of the present invention is used, a compact, lightweight, and high-performance electronic still camera can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an aspherical zoom lens according to Embodiment 1 of the present invention.

FIG. 2 is a configuration diagram of an aspherical zoom lens according to Embodiment 2 of the present invention.

FIG. 3 is a diagram illustrating an example of aberration performance at the wide-angle end according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of aberration performance at a standard position according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of aberration performance at the telephoto end according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of aberration performance at a wide-angle end according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of aberration performance at a standard position according to the second embodiment of the present invention.

FIG. 8 is a diagram illustrating an example of aberration performance at a telephoto end according to a second embodiment of the present invention.

FIG. 9 is a diagram illustrating an example of aberration performance at the wide-angle end according to a third embodiment of the present invention.

FIG. 10 is a diagram illustrating an example of aberration performance at a standard position according to the third embodiment of the present invention.

FIG. 11 is a diagram illustrating an example of aberration performance at the telephoto end according to a third embodiment of the present invention.

FIG. 12 is a diagram illustrating an example of aberration performance at the wide-angle end according to a fourth embodiment of the present invention.

FIG. 13 is a diagram illustrating an example of aberration performance at a standard position according to the fourth embodiment of the present invention.

FIG. 14 is a diagram illustrating an example of aberration performance at the telephoto end according to a fourth embodiment of the present invention.

FIG. 15 is a diagram illustrating an example of aberration performance at the wide-angle end according to a fifth embodiment of the present invention.

FIG. 16 is a diagram illustrating an example of aberration performance at a standard position according to the fifth embodiment of the present invention.

FIG. 17 is a diagram illustrating an example of aberration performance at the telephoto end according to a fifth embodiment of the present invention.

FIG. 18 is a diagram illustrating an example of aberration performance at a wide-angle end according to a sixth embodiment of the present invention.

FIG. 19 is a diagram illustrating an example of aberration performance at a standard position according to the sixth embodiment of the present invention.

FIG. 20 is a diagram illustrating an example of aberration performance at the telephoto end according to a sixth embodiment of the present invention.

FIG. 21 is a diagram illustrating an example of aberration performance at the wide-angle end according to a seventh embodiment of the present invention.

FIG. 22 is a diagram illustrating an example of aberration performance at a standard position according to the seventh embodiment of the present invention.

FIG. 23 is a diagram illustrating an example of aberration performance at a telephoto end according to a seventh embodiment of the present invention.

FIG. 24 is a diagram illustrating an example of aberration performance at the wide-angle end according to the eighth embodiment of the present invention.

FIG. 25 is a diagram illustrating an example of aberration performance at a standard position according to the eighth embodiment of the present invention.

FIG. 26 is a diagram showing an example of aberration performance at the telephoto end according to an eighth embodiment of the present invention.

FIG. 27 is a diagram illustrating an example of aberration performance at the wide-angle end according to a ninth embodiment of the present invention.

FIG. 28 is a diagram illustrating an example of aberration performance at a standard position according to the ninth embodiment of the present invention.

FIG. 29 is a diagram illustrating an example of aberration performance at the telephoto end according to a ninth embodiment of the present invention.

FIG. 30 is a configuration diagram of a video camera according to an embodiment of the present invention.

FIG. 31 is a configuration diagram of an embodiment of an electronic still camera according to the present invention.

FIG. 32 is a configuration diagram of an example of a conventional zoom lens.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st lens group 1a, 2a, 3c Lens having negative refractive power 1b Lens having positive refractive power 1c Meniscus lens 2 2nd lens group 2b Biconcave lens 2c, 3b Lens having positive refractive power with a convex object side. 3 Third lens group 3a Biconvex lens having aspherical surfaces on both surfaces 4 Fourth lens group 5 Flat plate 6 Image plane

Claims (16)

[Claims] 1. A first lens unit having a positive refractive power and fixed with respect to an image plane, and a zooming effect by moving on an optical axis having a negative refractive power in order from the object side. A second lens group to be applied, a third lens group having a positive refractive power and fixed with respect to the image plane, and an image plane that fluctuates with the movement of the second lens group and the movement of an object as a reference. A fourth lens group having a positive refractive power, which moves on the optical axis so as to be kept at a constant position from the surface, is disposed. The first lens group includes, in order from the object side, a lens having a negative refractive power and a positive lens. The second lens group includes, in order from the object side, a lens having a negative refractive power, a biconcave lens, and the biconcave lens. A lens having a positive refractive power whose object side is a convex surface joined to the At least one of the second lens groups
The surface is an aspheric surface, and the third lens group includes, in order from the object, a lens having a positive refractive power, a lens having a positive refractive power, and a lens having a negative refractive power. At least one of the surfaces is aspherical, the fourth lens group includes one or more lenses, and at least one surface of the fourth lens group is aspherical and has a focal length fw at a wide-angle end.
And the half angle of view ω at the wide-angle end, the focal length f1 of the first lens group, and the focal length f2 of the second lens group are: 0.39 <(fw · tanω) / (f1 · | f2 |) ^{1 / 2} <
A zoom lens satisfying a relationship of 1.07 and having a zoom ratio (focal length at a telephoto end / focal length at a wide-angle end) of more than 10 times. 2. The lens having a positive refractive power on the object side of the third lens group is a biconvex lens, and the lens having a negative refractive power has a concave surface facing the image plane, and has a refractive power p3c of the concave surface and a wide angle. The zoom lens according to claim 1, wherein a focal length fw at an end satisfies a relationship of 0.37 <fw · | p3c | <0.84. 3. The third lens group includes, in order from the object side, a biconvex lens having a positive refractive power, a lens having a positive refractive power with the convex surface facing the object side, and a positive lens with a convex surface facing the object side. 3. The zoom lens according to claim 1, further comprising: a lens having a negative refractive power, which is cemented to the lens having a negative refractive power and having a concave surface on the image surface side, wherein the cemented lens has a negative refractive power. 4. The third lens group includes, in order from the object side, a biconvex lens having a positive refractive power, a lens having a positive refractive power with the convex surface facing the object side, and a negative lens with a concave surface facing the image plane side. 3. The zoom lens according to claim 1, further comprising a lens having a refractive power of (a), and a space provided between the lenses of the third lens group. 4. 5. The focal length fw at the wide-angle end and the focal length fi (i = 1, 2, 3, 4) of the i-th lens group are: 0.11 <fw / f1 <0.83 0.66 < The zoom lens according to any one of claims 1 to 4, wherein a relationship of fw / | f2 | <1.69 0.21 <fw / f3 <0.52 0.21 <fw / f4 <0.46 is satisfied. 6. The focal length fw at the wide-angle end, the focal length fi (i = 1, 2, 3, 4) of the i-th lens unit, the half angle of view ω at the wide-angle end, and the negative value of the third lens unit. The refractive power p3c of the image-side surface of the lens having the refractive power is 0.533 <(fw · tanω) / (f1 | f2 |) ^1/2
<0.857 0.504 <fw · | p3c | <0.670 0.147 <fw / f1 <0.226 0.894 <fw / | f2 | <1.358 0.286 <fw / f3 <0 The zoom lens according to any one of claims 1 to 4, which satisfies the following relationship: 420 0.298 <fw / f4 <0.368. 7. In the third lens group, a focal length f31 of a lens having a positive refractive power on the object side and a combined focal length f of a lens having a positive refractive power and a lens having a negative refractive power on the image plane side.
7. The zoom lens according to claim 1, wherein satisfies the following relationship: 0.34 <f31 / | f323 | <1.05. 8. The lens having a positive refractive power on the object side of the third lens group has an aspheric surface on the object side, and has a local radius of curvature r311 at a diameter of 10% of an effective diameter of the lens. ,
The zoom lens according to any one of claims 1 to 7, wherein a local radius of curvature r319 at a diameter of 90% of the effective diameter satisfies a relationship of 0.29 <r311 / r319 <1.00. 9. A lens having a positive refractive power on the object side of the third lens group having an aspheric surface on an image-side surface, and a local radius of curvature r321 at a diameter of 10% of an effective diameter of the lens. When,
The zoom lens according to any one of claims 1 to 8, wherein a local radius of curvature r329 at a diameter of 90% of the effective diameter satisfies a relationship of 0.14 <r321 / r329 <0.72. 10. The biconcave lens of the second lens group has an aspheric surface on the object side, and has a local radius of curvature r211 at 10% of the effective diameter of the lens and 90% of the effective diameter. The zoom lens according to any one of claims 1 to 9, wherein a local radius of curvature r219 at the diameter satisfies the following relationship: 0.10 <r211 / r219 <1.52. 11. The lens of the fourth lens group has an aspheric surface on the object side, and has a local radius of curvature r411 at a diameter of 10% of the effective diameter of the lens and a diameter of 90% of the effective diameter. The zoom lens according to any one of claims 1 to 10, wherein a local radius of curvature r419 satisfies the following relationship: 0.34 <r411 / r419 <1.03. 12. The lens of the fourth lens group has an aspheric surface on the image side, and has a local radius of curvature r421 at a diameter of 10% of the effective diameter of the lens, and a diameter of 90% of the effective diameter. The zoom lens according to any one of claims 1 to 11, wherein a local radius of curvature r429 satisfies the following relationship: 0.64 <| r421 / r429 | <1.91. 13. The lens having a positive refractive power on the object side of the third lens group has an aspheric surface on the object side and the image plane side, and the biconcave lens of the second lens group has an aspheric surface on the object side. The fourth lens group has an aspheric surface on an object side or an image plane side, and has a focal length f31 of a positive refractive power lens on the object side of the third lens group; Focal length f323 of the positive refractive power lens and the negative refractive power lens on the side
And the effective diameter on the object side of the lens having a positive refractive power on the object side is 1
A local radius of curvature r311 at a radius of 90%, a local radius of curvature r319 at a radius of 90% of the effective diameter, and a radius of 10% of the effective diameter on the image plane side of a lens having a positive refractive power on the object side. A local radius of curvature r321, a local radius of curvature r329 at 90% of the effective diameter, a radius of curvature r211 at a radius of 10% of the object-side effective diameter of the biconcave lens of the second lens group, A local radius of curvature r219 at a diameter of 90% of the diameter, and 10% of the effective diameter of the object-side lens when the lens of the fourth lens group has an aspheric surface on the object-side surface. The local radius of curvature is r411,
The local radius of curvature at the diameter of 90% of the effective diameter is r419.
A local radius of curvature r421 at 10% of the effective diameter of the image-side lens when the lens of the fourth lens group has an aspheric surface on the image-side side, and 90% of the effective diameter. Is the local radius of curvature at r 429, where 0.492 <f31 / | f323 | <0.827 0.412 <r311 / r319 <0.767 0.193 <r321 / r329 <0.689 1.040 < 13. The method according to claim 1, wherein the following relationship is satisfied: r211 / r219 <1.170 and 0.490 <r411 / r419 <0.875 or 0.640 <| r421 / r429 | <1.470. Zoom lens. 14. The optical total length when the air between the lens surface closest to the image surface side of the fourth lens group and the image surface is air (from the surface of the first lens group which is closest to the object to the image surface). The distance) L, the focal length fw at the wide-angle end, and the focal length ft at the telephoto end satisfy a relationship of 2.24 <L.fw / ft <4.7. Zoom lens 15. A video camera using the zoom lens according to claim 1. Description: 16. An electronic still camera using the zoom lens according to claim 1. Description: