JPH068932B2 - Large aperture zoom lens - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens for photographing, and particularly to a compact large-diameter zoom lens suitable for a photographing device using an electronic image pickup tube or a solid-state image pickup device as an image pickup device.

2. Description of the Related Art An electronic image pickup tube is used as an image pickup device, and a zoom lens is almost used as a lens for a photographing device using a solid-state image pickup element. These zoom lenses are brighter than F / 2.0 and have a zoom ratio of 3x or more, which is superior to steel camera lenses that use a 35mm Leica size film, but they are compact and compact. It wasn't considered much in terms of cost. However, recently, a photographing device using a popular electronic image pickup device has begun to appear, and its optical system is also required to be compact and cost effective. Therefore, there is an increasing need for a zoom lens in which the diameter of the front lens group is small, the total length is short, and the number of constituent lenses is small as this type.

Since this type of lens system has a strong character as one element of the system, there is a regulation of the back focus length, and a gravity regulation for performing autofocus and power zoom with low power consumption. It is preferable to use rear focus instead of focus by groups, reduce the number of lens groups to be moved during zooming, or use a relay system that lengthens back focus.

There are many zoom lenses for photography that have a brightness of F / 2.0 or more and a zoom ratio of 3 or more, but are compact (the overall length is short and the front lens diameter is small), and the cost is high (especially the lens configuration). A high-performance zoom lens that satisfies all of the requirements for the number of pixels and the length of the back focus and is sufficiently capable of coping with an increase in the number of pixels of image pickup devices in the future has not yet been known. In particular, no attempt has been made to improve the performance while setting the back focus at 0.9 times or more the geometric mean f _S of the shortest focal length f _W and the longest focal length f _T of the zoom lens.

The need for a lens with a long back focus arises from the need to insert various optical members between the rear end of the lens and the imaging surface, but as the screen size becomes smaller and the focal length of the lens system becomes shorter, the back focus becomes shorter. The need to increase the ratio of f _B to f _S increases. Japanese Patent Sho 55-40
No. 852, Japanese Patent Publication No. 48-32387, and other zoom lenses having a small number of constituents are known, but these prior art examples do not take into consideration a short back focus or a long back focus.

Further, in the conventional example, even during autofocusing, focusing is performed while driving the front lens group having a large diameter and heavy weight.
By adopting a rear focus that drives a lens group that has a small diameter and is light to focus on it, autofocus with low power consumption becomes possible. As a zoom lens using this method, the one described in JP-A-57-78513 is known. However, although this type of autofocus has the above-described merits, Example 1 is not preferable in terms of performance due to large fluctuations in aberrations when focusing on a short distance, especially fluctuations in astigmatism, and in Example 2 F /
It is a dark lens at 5.6. As described above, this conventional example satisfies the requirement that the back focus is 0.9 times or more of f _S at F / 2.0 or more as described above, and the fluctuation of aberrations at the time of short-distance focusing, particularly spherical aberration and coma aberration, It does not meet certain conditions to reduce fluctuations.

Purpose The present invention has a zoom ratio of 3 in which the total angle of view is 15 ° to 45 °, is bright and high-performance in the F / 2.0 class, has a short overall length, has a long back focus, and has a driving torque even when autofocus is adopted. It is an object of the present invention to provide a large-aperture zoom lens capable of rear focusing with a small size.

In order to achieve the above-mentioned object, the zoom lens of the present invention comprises:
As shown in FIG. 1, in order from the object side, a first group having a positive focal length, a second group of variators and a third group of compensators having negative focal lengths and having a negative focal length. And a relay system, the relay system is composed of a front group and a rear group, the front group in order from the object side, a positive lens, a positive lens, a biconcave lens, The rear lens group is composed of four positive lenses, and the rear lens group is composed of two positive lens elements. The first lens group is fixed, and the rear lens group of the relay system is extended toward the object side along the optical axis. Focusing is performed and the following conditions are satisfied.

(1) −0.3 <f _W / f _A <0.2 where f _W is the shortest focal length of the entire system, and f _A is the combined focal length from the first group to the front group of the relay system.

In the zoom lens of the present invention, focusing on a short-distance object point may be performed by moving the first group I toward the object side. However, in this focusing method, vignetting increases as the object point approaches a closer distance. In order to easily prevent this, it is necessary to increase the diameter of the first group I. In addition, when autofocusing is performed using the first group I having a large diameter and a large weight, the torque of the motor increases, and power consumption tends to increase. For this reason, there is a lens having a small lens diameter and a part of a light rear lens group that is moved to perform autofocus.

In this case, focusing can be performed by moving the rear group IVb toward the object side along the optical axis by using a relatively large air space between the front group IVa and the rear group IVb of the relay system. However, this focusing method tends to have a large variation in aberration when focusing on an object point at a short distance, and in particular, as in the present invention, F /
This focusing method is difficult to apply to zoom lenses that are brighter than 2.0.

In the lens system of the present invention, the system from the first group I to the front group IVa of the relay system (system shown by A in the drawing) is configured to be substantially afocal so that the above focusing method can be applied. I am doing it. In consideration of satisfying one of the objects of the present invention that the back focus is longer than 0.9 f _S , the system A (the system from the first group I to the front group IVa of the relay system) described above is considered. The combined focal length f _A must satisfy the above condition (1).

If the lower limit of this condition (1) is exceeded, spherical aberration tends to be overcorrected when focusing on a near object point, and if it exceeds the upper limit, spherical aberration is likely to be undercorrected and the back focus is set to 0.9 f _S or more. Becomes difficult.

The magnification of the afocal system when the focal length of the zoom lens is f _S is preferably around 0.9. Further, in order to reduce the variation of astigmatism when focusing on an object point at a short distance, it is desirable to make the positive lens component on the object side of the rear lens group IVb of the relay system concentric with respect to the pupil. A convex surface having a strong curvature is provided on the image side of the lens component. This is also advantageous for correction of spherical aberration in order to obtain a large-diameter zoom lens brighter than F / 2.0. It is also advantageous for correction of spherical aberration that the object side surface of the positive lens component on the image side of the rear group IVb has a convex surface having a curvature which is obviously stronger than that on the image side.

Further, in order to lengthen the back focus which is one of the objects of the present invention, the front lens group IVa of the relay group is made to include a negative lens component of relatively strong power, and thereafter the lens group IVb is composed of two positive lenses. Configured. Further, the front group of the relay system is composed of four components which are necessary and sufficient to satisfactorily correct spherical aberration and coma even if the lens system is as bright as F / 2.0. Considering both the lengthening of the back focus and the excellent correction of aberrations, it is preferable to make the air space between the front group IVa and the rear group IVb a little larger. Further, if the total length of the lens system is also taken into consideration, it is preferable that the lens configuration of the front lens group IVa has two positive lens components, a negative lens component, and a positive lens component in order from the object side. It is necessary to increase the curvature of the negative lens component of the front lens group IVa in order to lengthen the back focus, so that high-order aberrations such as spherical aberration and coma are likely to occur. This is because it is better to move the lens component as close to the object side as possible.

The air gap D between the front group IVa and the rear group IVb is preferably selected within the range of the following condition (2).

(2) 0.14f _IV <D <0.5f _{IV where} f _IV is the focal length of the relay system.

If the lower limit of condition (2) is exceeded, the curvature of the negative lens component of the front lens group IVa of the relay system will become strong, and higher-order aberrations such as spherical aberration and coma will easily occur. If the upper limit is exceeded, the total length of the lens system will increase. It tends to be long.

Further, it is desirable that the distance l of the rear lens principal point position of the negative lens component of the front lens group IVa of the relay system from the rear focus position of the entire zoom lens system satisfies the following condition (3).

(3) 1.5f _IV <l <2.2f _IV where f _IV is the focal length of the relay IV.

When the value goes below the lower limit of the condition (3), the curvature of the negative lens component of the front lens group IVa becomes strong, and higher-order aberrations such as spherical aberration and coma are likely to occur. On the contrary, if the upper limit is exceeded, the total length of the lens system tends to be long.

An object of the present invention is to provide a high-performance zoom lens that has a surplus for current electronic image pickup devices in view of the future. Therefore, in the zoom lens according to the present invention, the first group is composed of a positive lens component in which a negative meniscus lens and a biconvex lens are cemented in order from the object side, and a positive meniscus lens component of a single lens. II is composed of a negative meniscus component of a single lens and a negative lens component in which a biconvex lens and a positive lens are cemented, and the third lens group III is configured to include one negative lens component. The front lens group IVa of the fourth lens group is composed of a positive lens element, a positive lens element, a negative lens element and a positive lens element and has a four-element four-lens element, and the air gap between them is as small as possible. It is composed of two positive lenses arranged with an air gap. Further, the following conditions (4) to (13) are satisfied.

(4) 0.5f _S <f _IVa <1.6f _S (5) 0.42f _S <| f _IVan ｜ <0.64f _S (6) 2.5f _W <f _I <3.5f _W (7) -1.2f _W <f _II <-0.8f _W (8) 1.7 <n ₄ (9) 0.05 <n ₆ −n ₅ (10) 1.6 <n ₅ (11) 13 <ν ₅ −ν ₆ (12) 1.78 <n _IVan (13) ν _IVap <ν _{IVbp where} f _IVa is the focal length of the front lens group of the relay system, f _IVan is the focal length of the negative lens of the front lens group of the relay system, f _I is the focal length of the first lens group, and f _II is the second lens group. Focal length, n ₄ is the refractive index of the negative meniscus lens of the second group, n ₅ and ν ₅ are the refractive index of the biconcave lens of the second group, and the Atsube number, n ₆ and ν ₆ are the positive lenses of the second group the refractive index and Abbe's number, n _Ivan the refractive index of the negative lens of the front group of the relay system, ν _IVap the Abbe's number of the mean value of the positive lens of the front group of the relay system, ν _IVbp the positive group of the relay system It is the average value of the Abbe number of the lens.

Next, the contents of the above conditions (4) to (13) will be described in detail.

Conditions (4) and (5) are the negative lens component in the front group IV _a and the front group IV _a of the relay system so that the back focus is lengthened and the total length of the lens system is shortened so that each aberration becomes good. This is a condition for setting the focal length of. If the upper limit of condition (4) is exceeded, the total length of the relay system will become long, and if the lower limit is exceeded, the back focus will tend to be short. If the upper limit of the condition (5) is exceeded, the back focus becomes short, and if the lower limit of the condition (5) is exceeded, higher-order aberrations are likely to occur and it becomes difficult to correct the aberration.

The condition (6) defines the focal length of the first lens group I. If the upper limit of this condition is exceeded, the overall length of the variable power system becomes long, and if the lower limit is exceeded, the radius of curvature of each surface of the first lens group I becomes small, and the wall thickness becomes large in order to obtain the required lens diameter. Absent. In addition, the aberration is deteriorated and the correction becomes difficult.

The condition (7) defines the focal length of the second lens group II, and if it exceeds the upper limit, it is advantageous for shortening the total length of the zooming system, but the aberration fluctuation during zooming becomes too large. Become a trend. If the lower limit is exceeded, the total length of the variable power system becomes long.

Further, if the powers of the first group I and the second group II become too strong, the angle formed between the two groups and the optical axis of the off-axis ray becomes large, and the entrance pupil is directed toward the image side unless the distance between them is considerably reduced. As a result, the diameter of the front lens must be increased.

The conditions (8) to (11) define the glass material of the lens of the second lens group II.

If the lower limits of the conditions (8) to (10) are exceeded, the aberration variation during zooming tends to be large, which is not preferable.

If the lower limit of condition (11) is exceeded, the variation of chromatic aberration during zooming will increase.

Conditions (12) and (13) are conditions regarding selection of the glass material of the lens of the relay system (fourth group).

The surface of the zoom lens having the highest aberration coefficient is the surface of the negative lens of the relay system on the object side. Therefore, it is necessary to increase the refractive index of the lens in order to obtain a predetermined power while loosening the curvature of this surface. As to that defines the refractive index n _Ivan of the lens due to the condition (1
2). When the value goes below the lower limit of this condition, high-order spherical aberration is likely to occur.

The condition (13) is provided in order to satisfactorily correct lateral chromatic aberration. If this condition is not satisfied, axial chromatic aberration can be corrected but lateral chromatic aberration will be insufficiently corrected.

EXAMPLES Next, examples of the large-diameter zoom lens of the present invention described in detail above will be shown.

Example 1 f = 14 to 24.25 to 42 r ₁ = 84.1276 d ₁ = 1.1600 n ₁ = 1.80518 v ₁ = 25.43 r ₂ = 29.0902 d ₂ = 7.3000 n ₂ = 1.62012 v ₂ = 49.66 r ₃ = -273.1915 d ₃ = _{0.1700 r 4 = 28.7778 d 4 =} 5.6000 n 3 = 1.62012 ν 3 = 49.66 r 5 = 203.0683 d 5 = 0.6000 r 6 = 29.7145 d 6 = 1.0400 n 4 = 1.73400 ν 4 = 51.49 r 7 = 11.3398 d 7 = 3.9500 r _{8 = -21.5403 d 8 = 1.0400 n} 5 = 1.69350 ν 5 = 53.23 r 9 = 15.9303 d 9 = 3.1000 n 6 = 1.84666 ν 6 = 23.88 r 10 = 1554.6274 d 10 = 12.9984 r 11 = -14.7944 d 11 = 1.0000 n _{7 = 1.69680 ν 7 = 55.52 r} 12 = -36.0319 d 12 = 4.9325 r 13 = 50.3787 d 13 = 2.6753 n 8 = 1.74950 ν 8 = 35.27 r 14 = -29.8033 d 14 = 0.6469 r 15 = ∞ ( stop) _{d 15} = 2.0000 r ₁₆ = 20.2193 d ₁₆ = 5.3125 n ₉ = 1.69350 ν ₉ = 53.2 _{3 r 17 = -440.8891 d 17 =} 0.8000 r 18 = -25.3662 d 18 = 1.4008 n 10 = 1.84666 ν 10 = 23.88 r 19 = 18.0976 d 19 = 1.8984 r 20 = 104.9452 d 20 = 3.0000 n 11 = 1.56873 ν 11 = 63.16 r ₂₁ = -33.8872 d ₂₁ = 6.0137 r ₂₂ = -1877.6563 d ₂₂ = 3.6497 n ₁₂ = 1.48749 v ₁₂ = 70.15 r ₂₃ = -18.1673 d ₂₃ = 0.1342 r ₂₄ = 27.7264 d ₂₄ = 3.315649 n ₁₃ = _13. = 70.15 r ₂₅ = -111.3847 l / f _IV = 1.642, D / f _IV = 0.237, f _W / f _A = -0.221 f _IVa / f _S = 1.186, f _IVan / f _S = -0.507 f _I / f _{W = 2.996, f II / f W} = -1.098, n 4 = 1.73400 n 6 -n 5 = 0.15316, n 5 = 1.69350, ν 5 -ν 6 = 29.35 n IVan = 1.84666, ν IVap -ν IVbp = -19.597 f _B = 23.3 Example 2 f = 14 to 24.25 to 42 r ₁ = 82.8380 d ₁ = 1.1600 n ₁ = 1.80518 ν ₁ = 25.43 r ₂ = 28.9584 d _{2 = 7.3000 n 2 = 1.62012 ν 2} = 49.66 r 3 = -243.9198 d 3 = 0.1700 r 4 = 28.9601 d 4 = 5.6000 n 3 = 1.62374 ν 3 = 47.10 r 5 = 203.8797 d 5 = 0.6000 r 6 = 29.0358 d 6 = _{1.0400 n 4 = 1.73400 ν 4 =} 51.49 r 7 = 11.4509 d 7 = 3.9500 r 8 = -21.5434 d 8 = 1.0400 n 5 = 1.69680 ν 5 = 55.52 r 9 = 16.1419 d 9 = 3.1000 n 6 = 1.84666 ν 6 = 23.88 _{r 10 = 327.0857 d 10 = 12.7201} r 11 = -15.1829 d 11 = 1.0000 n 7 = 1.69680 ν 7 = 55.52 r 12 = -38.3036 d 12 = 4.8880 r 13 = 50.2085 d 13 = 2.6726 n 8 = 1.76200 ν 8 = 40.10 r ₁₄ = -29.8907 d ₁₄ = 0.6433 r ₁₅ = ∞ (aperture) d ₁₅ = 2.0000 r ₁₆ = 20.1914 d ₁₆ = 5.5367 n ₉ = 1.69680 ν ₉ = 55.52 r ₁₇ = 2178.6990 d ₁₇ = 0.8000 r ₁₈ = -25.67 ₁₈ = 1.4025 n ₁₀ = 1.84666 ν ₁₀ = 23.88 r _{19 = 18.2541 d 19 = 1.8967 r} 20 = 89.3959 d 20 = 3.0000 n 11 = 1.62041 ν 11 = 60.27 r 21 = -41.7577 d 21 = 6.1391 r 22 = -2160.7673 d 22 = 3.6490 n 12 = 1.56873 ν 12 = 63.16 r _{23 = -20.1024 d 23 = 0.1342 r} 24 = 28.7875 d 24 = 3.3002 n 13 = 1.48749 ν 13 = -70.15 r 25 = 70.15 l / f IV = 1.752, D / f IV = 0.258, f W / f A = - 0.253 f _IVa / f _S = 1.180, f _IVan / f _S = -0.508 f _I / f _W = 2.951, f _II / f _W = -1.068, n ₄ = 1.73400 n ₆ -n ₅ = 0.14986, n ₅ = 1.69680 , Ν ₅ −ν ₆ = 31.64 n _IVan = 1.84666, ν _IVap −ν _IVbp = -14.692 f _B = 23.3 Example 3 f = 14 to 24.25 to 42 r ₁ = 83.0383 d ₁ = 1.1600 n ₁ = 1.80518 ν ₁ = 25.43 r ₂ = 29.1400 d ₂ = 7.3000 n ₂ = 1.62012 ν ₂ = 49.66 r ₃ = -253.1450 d ₃ = 0.1700 r ₄ = 28.6874 d ₄ = 5.6000 n ₃ = 1.6 _{2012 ν 3 = 49.66 r 5 =} 210.2929 d 5 = 0.6000 r 6 = 30.3630 d 6 = 1.0400 n 4 = 1.73400 ν 4 = 51.49 r 7 = 11.3638 d 7 = 3.9500 r 8 = -21.4761 d 8 = 1.0400 n 5 = 1.69350 _{ν 5 = 53.23 r 9 = 17.0207} d 9 = 3.1000 n 6 = 1.84666 ν 6 = 23.88 r 10 = 1069.1825 d 10 = 13.0418 r 11 = -14.1675 d 11 = 1.0000 n 7 = 1.69680 ν 7 = 55.52 r 12 = -36.2700 _{d 12 = 4.5289 r 13 = 55.6389} d 13 = 2.6729 n 8 = 1.74950 ν 8 = 35.27 r 14 = -31.9536 d 14 = 0.6353 r 15 = ∞ ( _{stop) d 15 = 2.0000 r 16 =} 21.0858 d 16 = 5.0173 n 9 _{= 1.69350 ν 9 = 53.23 r 17} = -708.9650 d 17 = 0.8000 r 18 = -27.0343 d 18 = 1.4021 n 10 = 1.84666 ν 10 = 23.88 r 19 = 19.1950 d 19 = 1.9053 r 20 = 45.3739 d 20 = 3.0000 n 11 = 1.56873 ν ₁₁ = 63.16 r _{21 = -24.8871 d 21 = 6.6760 r 22} = -119.5541 d 22 = 3.6491 n 12 = 1.48749 ν 12 = 70.15 r 23 = -20.3750 d 23 = 0.1342 r 24 = 28.5509 d 24 = 3.3004 n 13 = 1.48749 ν 13 = 70.15 r ₂₅ = 144.4908 l / f _IV = 1.863, D / f _IV = 0.296, f _W / f _A = -0.016 f _IVa / f _S = 1.071, f _IVan / f _S = -0.539 f _I / f _W = 2.939, f _II / f _W = -1.071, n ₄ = 1.73400 n ₆ -n ₅ = 0.15316, n ₅ = 1.69350, ν ₅ -ν ₆ = 29.35 n _IVan = 1.84666, ν _IVap −ν _IVbp −19.597 f _B = 23.3 Implemented example _{4 f = 14~24.25~42 r 1 = 82.6129} d 1 = 1.1600 n 1 = 1.80518 ν 1 = 25.43 r 2 = 29.2181 d 2 = 7.3000 n 2 = 1.62012 ν 2 = 49.66 r 3 = -246.0953 d 3 = 0.1700 _{r 4 = 28.4664 d 4 = 5.6000} n 3 = 1.62012 ν 3 = 49.66 r 5 = 217.2658 d 5 = 0.6000 r 6 = 34.0022 d 6 = 1.0400 n 4 = 1.73400 ν 4 = 51.49 _{7 = 11.4972 d 7 = 3.9500 r} 8 = -20.9945 d 8 = 1.0400 n 5 = 1.69350 ν 5 = 53.23 r 9 = 16.3829 d 9 = 3.1000 n 6 = 1.84666 ν 6 = 23.88 r 10 = 646.6454 d 10 = 12.8886 r 11 = -14.2623 d ₁₁ = 1.0000 n ₇ = 1.69680 ν ₇ = 55.52 r ₁₂ = -30.9806 d ₁₂ = 4.5295 r ₁₃ = 50.7675 d ₁₃ = 2.6656 n ₈ = 1.74950 ν ₈ = 35.27 r ₁₄ = -30.6539 921 d _{14 15} = ∞ _{(stop) d 15 = 2.0000 r 16 =} 19.1840 d 16 = 5.6618 n 9 = 1.69350 ν 9 = 53.23 r 17 = 3649.8366 d 17 = 0.8000 r 18 = -24.4207 d 18 = 1.4073 n 10 = 1.84666 ν 10 = _{23.88 r 19 = 18.4904 d 19 =} 3.8044 r 20 = 80.9804 d 20 = 3.0000 n 11 = 1.56873 ν 11 = 63.16 r 21 = -23.6744 d 21 = 4.3200 r 22 = -81.0091 d 22 = 3.6442 n 12 = 1.48749 ν 12 = 70.15 r ₂₃ =- 19.6764 d ₂₃ = 0.1342 r ₂₄ = 28.3524 d ₂₄ = 3.3101 n ₁₃ = 1.48749 ν ₁₃ = 70.15 r ₂₅ = -150.6774 l / f _IV = 1.771, D / f _IV = 0.184, f _W / f _A = -0.010 f _IVa / F _S = 1.095, f _IVan / f _S = -0.505 f _I / f _W = 2.894, f _II / f _W = -1.021, n ₄ = 1.73400 n ₆ -n ₅ = 0.15316, n ₅ = 1.69350, ν ₅ −ν ₆ = 29.35 n _IVan = 1.84666, ν _IVap −ν _IVbp −19.597 f _B = 23.3 where r ₁ , r ₂ , ... Are the radii of curvature of each lens surface, and d ₁ , d ₂ ,. The thickness and air gap of each lens, n ₁ , n ₂ , ... Is the refractive index of each lens, ν ₁ , ν ₂ ,
... is the Abbe number of each lens, f is the focal length of the entire system, f
_B is the back focus.

All of the first to fourth embodiments are shown in FIG. 1, and the front group IVa of the relay system is composed of positive, positive, negative and positive. Regarding the aberrations of these examples, Example 1 is shown in FIG. 2 (wide), FIG. 3 (standard), FIG. 4 (tele), and Example 2 is shown in FIG. 5 (wide) and FIG. 6 (standard). ，
FIG. 7 (tele), Example 3 is FIG. 8 (wide), FIG. 9 (standard), FIG. 10 (tele), and Example 4 is first.
They are shown in FIG. 1 (wide), FIG. 12 (standard), and FIG. 13 (tele), respectively.

In each of these embodiments, focusing is performed by extending the rear group IVb of the relay system IV. The amount of feeding at that time is as follows.

f = 14f = 24.25f = 42 Example 1 0.183 0.542 1.633 Example 2 0.186 0.552 1.672 Example 3 0.173 0.510 1.505 Example 4 0.173 0.510 1.499 Advantages of the Invention As described in detail above, the zoom lens of the present invention is as follows. Further, as is apparent from the embodiment, by appropriately setting the configuration of the fourth group IV which is a relay system, F / 2.0, zoom ratio 3, angle of view of 15 ° to 45 ° and back focus of 0.9 f.
It is a high-performance zoom lens in which aberrations are favorably corrected while lengthening to _S or more, and can sufficiently cope with future increase in the number of pixels of the image pickup device.

[Brief description of drawings]

FIG. 1 is a sectional view of Embodiments 1 to 4 of the present invention, and FIG.
4 to 4 are aberration curve diagrams of Embodiment 1, and FIGS.
8 is an aberration curve diagram of Example 2, FIGS. 8 to 10 are aberration curve diagrams of Example 3, and FIGS. 11 to 13 are aberration curve diagrams of Example 4.

Claims (2)

[Claims] 1. A first group having a positive focal length, a second group of variators each having a negative focal length that moves during zooming, and a third group of compensators each having a negative focal length in order from the object side. A variable power system including a group, and a relay system, wherein the relay lens system includes a front group and a rear group, and the front group includes, in order from the object side, a positive lens, a positive lens, and both lenses. The rear lens group is composed of four lenses, a concave lens and a positive lens, and the rear lens group is composed of two positive lenses. The first lens group is fixed, and the rear lens group of the relay lens system is extended toward the object side along the optical axis to bring the lens closer. A large-aperture zoom lens that focuses on a distance object and satisfies the following conditions. (1) −0.3 <f _W / f _A <0.2 where f _W is the shortest focal length of the entire system, and f _A is the combined focal length from the first group to the front group of the relay system. 2. A positive lens closest to the object in the rear group is a convex surface having a stronger curvature on the image side, and a positive lens closer to the image is a convex surface having a stronger curvature on the object side. A large-diameter zoom lens according to claim 1.