JPH0833515B2 - Compact high-magnification zoom lens - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact high-magnification zoom lens having a magnification of 2 or more and aberrations well corrected.

[Conventional technology]

In recent years, with the miniaturization of cameras, a compact zoom lens having a short total length has been required. Among these,
The same applies to a lens shutter camera in which portability is emphasized due to the advancement of full automation. However, although the restrictions on the back focus are loose, there is a strong demand for further miniaturization.

As a lens system of this type, there is a zoom lens for a lens shutter camera disclosed in Japanese Patent Laid-Open No. 57-201213, which is characterized by a simple lens structure.

These zoom lenses consist of a first lens group having a positive refracting power and a second lens group having a negative refracting power in order from the object side, and change the magnification by changing the interval between these two lens groups. This is a so-called two-group zoom system.

Further, there has been proposed a zoom lens of a three-group zoom system which is considered to be a development of the above-mentioned two-group zoom system as disclosed in JP-A-58-137813. With a zoom lens having such a structure, a compact zoom lens with a small number of lens components can be used if the magnification is about 1.5 times, but if the magnification is increased to about 2 times, the lens group for magnification will bear the burden. Larger magnification, which results in larger aberration fluctuation during zooming, increased number of lens components required for aberration correction, and increased overall size of the lens system, resulting in good optical performance and compact lens system. I can't.

In order to solve such a drawback, a two-group zoom type zoom lens using a lens of a medium whose refractive index continuously changes according to the distance from the optical axis, that is, a gradient index lens has recently been disclosed. It is disclosed in Japanese Patent Publication No. 61-148414.

This lens system uses a so-called radial type gradient index lens having a refractive index distribution in the radial direction from the optical axis among its constituent elements to share the refractive power with the lens medium and keep the refractive power of each lens strong. This is intended to suppress the aberration fluctuation during zooming and to maintain a good Petzval sum that contributes to the flatness of the image plane.

However, this zoom lens is intended for use at zoom ratios of up to about 2 times, and although it has achieved a sufficient effect for correction of the aberration of interest, it cannot be said that correction of other aberrations is sufficient. Without leaving issues in the future. Further, the drawback that the back focus of the lens system is extremely short remains. Therefore, the problem that the rear lens unit becomes large has not been solved, and compactness cannot be achieved.

[Problems to be solved by the invention]

The present invention has a compact zoom ratio with a zoom ratio from the wide-angle end to the telephoto end of more than 2 times, a small aberration variation, an extremely flat image plane, and excellent optical performance over the entire zoom range. It is intended to provide a lens.

[Means for solving problems]

In order to solve the above problems, that is, in order to achieve a high zoom ratio and to make the zoom lens compact, a so-called four-group zoom system including four lens groups is used, and a refractive index distribution is appropriately set. By using a mold lens, the aberration variation from the wide-angle end to the telephoto end is small, and the image surface is flat from the central part of the screen to the peripheral part of the screen.

The zoom lens of the present invention comprises, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a third lens group having a negative refractive power. It is composed of four lens groups, and moves each of the first lens group to the fourth lens group on the optical axis when zooming to the telephoto end with the wide-angle end as a reference. At least one gradient index lens having a gradient index distribution in the optical axis direction is provided.

As described above, in the present invention, by using a so-called axial type gradient index lens having a refractive index distribution in the optical axis direction in the lens group, it is possible to reduce the residual aberration amount of the lens group and thereby the aberration fluctuation during zooming. It is intended to suppress and to achieve extremely good imaging performance.

The zoom lens of the present invention is characterized in that a zoom ratio exceeding at least 2 is secured, and the load of the zoom ratio of the fourth lens unit having negative refractive power becomes large in order to shorten the overall length of the lens system. It is a group zoom system. This is because it is possible to achieve a high zoom ratio reasonably by sharing the zoom ratio with each lens group.

In order to shorten the total length of the lens system, it is effective to adopt a so-called telephoto type refractive power arrangement. In the zoom lens according to the present invention, the first lens group to the third lens group have positive refractive power as a whole, and the fourth lens group having negative refractive power shortens the back focus of the lens system at the wide-angle end. There is.

In order to make such a structure and further make the lens system compact, it is necessary to increase the refractive power of each lens group.
However, it becomes difficult to correct the balance of various aberrations, especially astigmatism and distortion at the wide-angle end, spherical aberration, astigmatism, and distortion at the telephoto end.

In the zoom lens of the present invention, the above-mentioned various aberrations are satisfactorily corrected by using the gradient index lens so that a good imaging performance is obtained.

Generally known gradient index lenses include a radial type in which the refractive index changes in the radial direction from the optical axis and an axial type in which the refractive index changes in the optical axis direction. The radial type is superior in the compactness of the lens system and the ability to correct aberrations, but it is difficult to obtain a lens having a large outer diameter. On the other hand, the axial type has a low correction effect on the Petzval sum due to its structure and is almost equivalent to an aspherical lens, but it is superior to the aspherical lens in terms of workability, and when used as an optical component, Its feasibility is higher.

In consideration of the above points, according to the present invention, an axial type gradient index lens is used as the gradient index lens used in the zoom lens having the above-described configuration to satisfactorily correct various aberrations.

This axial gradient index lens has no refractive power in the lens medium portion and does not have the Petzval sum correction effect as described above, so the refractive power arrangement of the zoom lens in the state where no refractive index distribution is attached It is necessary to determine the behavior during zooming.

First, in order to obtain a compact lens system having a required magnification, the fourth lens group has the following condition (1),
It is necessary to satisfy (2).

(1) 0.4 <| f ₄ / f _W | <2 (2) 1 <β _4T / β _4W <3 where f _W is the focal length of the entire system at the wide end, f ₄ is the focal length of the fourth lens group, β _4W is the lateral magnification of the fourth lens unit at the wide-angle end, and β _4T is the lateral magnification of the fourth lens unit at the telephoto end.

The condition (1) defines the refracting power of the fourth lens group and relates to downsizing of the lens system. If the upper limit of this condition is exceeded, the refracting power of the fourth lens group will be weakened, and as a result, the lens system will be large, which is contrary to the object of the present invention. When the value goes below the lower limit, the refracting power of the fourth lens group becomes too strong, and the amount of aberration generated in this lens group becomes significant, so that aberration fluctuations due to zooming become large and it becomes difficult to obtain good optical performance. It is not preferable.

The condition (2) defines the zoom ratio of the fourth lens group when zooming from the wide-angle end to the telephoto end. If the upper limit of this condition is exceeded, the zooming range of the fourth lens group will become wider than necessary, and the amount of zooming movement of the fourth lens group itself will become large, so the share of magnification of the lens groups other than this lens group will decrease, The meaning of using the 4-group zoom system becomes weak, and the overall length of the lens system becomes long, and the flatness of the image plane cannot be compensated. When the value goes below the lower limit of the condition (2), the magnification of the second lens group and the third lens group becomes large, and the moving amount of the second lens group and the third lens group is increased or the refractive power is increased. It has to be big. In the former case, the total length of the lens system becomes long, especially at the wide-angle end, which is contrary to the object of the present invention. In the latter case, the residual amount of aberration increases and the balance of various aberrations deteriorates, and aberration cannot be corrected well even if an axial type gradient index lens is used.

Further, it is desirable that the third lens group be constructed so as to satisfy the following conditions (3) and (4).

(3) | β _3W | <0.75 (4) 0.5 <β _3T / β _3W <1.5 However, β _3W and β _3T are the third at the wide-angle end and the telephoto end, respectively.
It is the lateral magnification of the lens group.

When the condition (3) is exceeded, the refracting power of the third lens unit becomes weak and the amount of zooming movement becomes large.

When the value goes below the lower limit of the condition (4), the demagnifying action of the third lens group becomes large, the magnification load of the second lens group becomes large, and the zooming movement space of this lens group becomes insufficient. It becomes difficult to correct the aberration. When the value exceeds the upper limit of the condition (4), the magnification of the third lens group itself becomes large, and it becomes necessary to change the zooming movement method, which makes it difficult to shorten the total length at the wide-angle end.

The refractive index distribution of the axial type gradient index lens used in the lens system of the present invention is represented by the following equation.

n (x) = n ₀ + n ₁ x + n ₂ x ² + n ₃ x ³ + ... where x is the distance in the optical axis direction with the apex on the object side of the lens as the origin, and n ₀ is the refractive index at the apex on the object side of the lens. , N ₁ , n ₂ ,
n ₃ , ... are coefficients of the first order, second order, third order, ...

The gradient index lens used in the present invention preferably satisfies the following conditions.

(5) Δn _A <0.15 (6) | n ₁ · f _W | <3.0 where Δn _A is the maximum refractive index difference between the object-side apex and the image-side apex on the optical axis.

Currently, the manufacturing method of gradient index lenses is the ion exchange method,
Various methods such as the molecular stuffing method have been proposed. However, the maximum refractive index difference cannot be so large.

The condition (5) is defined in consideration of the above points, and if it exceeds this condition, it is extremely difficult in manufacturing.

The condition (6) defines the degree of the gradient of the refractive index. If the condition (6) is exceeded, the condition (5) is satisfied.
The coefficients of high-order apexes such as n ₂ , n ₃ , ... must be taken to be large, and high-order aberrations will be generated significantly.

〔Example〕

Next, each embodiment of the zoom lens of the present invention described above will be described.

Example 1 f = 39.00~103.46, F / 4.65~5.80 r 1 = ∞ d 1 = 2.397 n 01 = 1.85026 ν 01 = 32.28 r 2 = 29.204 d 2 = 4.804 n 02 = 1.72000 ν 02 = 46.03 r 3 = 201.839 _{d 3 = 0.049 r 4 = 26.784} d 4 = 3.003 n 03 = 1.53172 ν 03 = 48.90 r 5 = 678.471 d 5 = D 1 ( _{variable) r 6 = -36.191 d 6 =} 1.599 n 04 = 1.78650 ν 04 = 50.00 r ₇ = 23.392 d ₇ = 2.737 n ₀₅ = 1.80518 ν ₀₅ = 25.43 r ₈ = 97.276 d ₈ = D ₂ (variable) r ₉ = ∞ (aperture) d ₉ = 1.505 r ₁₀ = 89.145 d ₁₀ = 2.402 n ₀₆ Refractive index Distributed lens r ₁₁ = -37.448 d ₁₁ = 0.081 r ₁₂ = 15.678 d ₁₂ = 3.857 n ₀₇ = 1.57309 ν ₀₇ = 42.57 r ₁₃ = -445.852 d ₁₃ = 0.940 r ₁₄ = -61.134 d ₁₄ = 1.667 n ₀₈ = 1.84666 ν ₀₈ ＝ 23.88 r ₁₅ ＝ 18.466 d ₁₅ ＝ 2.340 r ₁₆ ＝ 37.897 d ₁₆ ＝ 3.931 n ₀₉ ＝ 1.57501 ν ₀₉ ＝ 41.49 r ₁₇ ＝ －35.137 d ₁₇ ＝ D ₃ (variable) r ₁₈ ＝ －33.144 d ₁₈ ＝ 2.973 n ₀₁₀ = 1.76182 ν ₀₁₀ = 26.52 r ₁₉ = -19.278 d ₁₉ = 3.253 r ₂₀ = -15.960 d ₂₀ = 2.397 n ₀₁₁ = 1.78650 ν ₀₁₁ = 50.00 r ₂₁ = 1417.734 f 39.00 61.20 103.46 D ₁ 1.501 7.720 11.342 D ₂ 11.230 6.852 1.800 D ₃ 12.920 7.098 2.232 Example 2 f = 39.52~100.80, F / 4.66~6.38 r 1 = 348.884 d 1 = 1.500 n 01 = 1.84666 ν 01 = 23.88 r 2 = 42.212 d 2 = 0.880 r 3 = 59.856 d 3 = 3.454 n 02 refractive index Distributed lens r ₄ = −12021.350 d ₄ = 0.200 r ₅ ＝ 27.466 d ₅ ＝ 4.500 n ₀₃ = 1.50378 ν ₀₃ ＝ 66.81 r ₆ ＝ －168.595 d ₆ ＝ D ₁ (variable) r ₇ ＝ －49.262 d ₇ = 1.300 n ₀₄ = 1.77250 ν ₀₄ ＝ 49.66 r ₈ ＝ 15.287 d ₈ ＝ 2.506 n ₀₅ = 1.80518 ν ₀₅ ＝ 25.43 r ₉ ＝ 50.384 d ₉ = 1.900 r ₁₀ ＝ −233.766 d ₁₀ = 1.300 n ₀₆ = 1.77250 ν ₀₆ ＝ 49.66 r ₁₁ = 512.917 d ₁₁ = D ₂ (variable) r ₁₂ = ∞ (aperture) d ₁₂ = 1.913 r ₁₃ = 25.371 d ₁₃ = 2.634 n ₀₇ = 1.61700 ν ₀₇ = 62.79 r ₁₄ = -51.148 d ₁₄ = 0.100 r ₁₅ = 24.624 d ₁₅ = 2.800 n ₀₈ = 1.59551 ν ₀₈ = 39.21 r ₁₆ = −163.875 d ₁₆ = 1.159 r ₁₇ = −28.916 d ₁₇ = 1.618 n ₀₉ = 1.80518 ν ₀₉ = 25.43 r ₁₈ = 22.563 d ₁₈ = 2.362 r ₁₉ = 68.569 d ₁₉ = 2.831 n ₀₁₀ = 1.60562 ν ₀₁₀ = 43.72 r ₂₀ = -21.454 d ₂₀ = D ₃ (variable) r ₂₁ = -35.663 d ₂₁ = 3.650 n ₀₁₁ = 1.78472 ν ₀₁₁ = 25.68 r ₂₂ = -20.124 d ₂₂ = 2.800 r ₂₃ = -17.065 d ₂₃ = 1.601 n ₀₁₂ = 1.78650 ν ₀₁₂ = 50.00 r ₂₄ = 3049.052 f 39.52 63.11 100.8 D ₁ 2.023 6.696 11.156 D ₂ 11.928 7.255 2.796 D ₃ 16.536 8.935 2.500 Example 3 f = 39.52~100.80, F / 4.66~6.38 r 1 = 348.884 d 1 = 1.500 n 01 = 1.84666 ν 01 = 23.88 r 2 = 41.075 d 2 = 0.880 r 3 = 61.331 d 3 = 3.454 n 02 = 1.72000 ν ₀₂ ＝ 41.98 r ₄ ＝ 549.867 d ₄ ＝ 0.200 r ₅ ＝ 25.404 d ₅ ＝ 4.500 n ₀₃ ＝ 1.51454 ν ₀₃ ＝ 54.69 r ₆ ＝ －786.113 d ₆ ＝ D ₁ (variable) r ₇ ＝ －39.868 d ₇ = 1.300 n ₀₄ = 1.75700 ν ₀₄ ＝ 47.87 r ₈ ＝ 15.287 d ₈ ＝ 2.506 n ₀₅ ＝ 1.80518 ν ₀₅ ＝ 25.43 r ₉ ＝ 55.979 d ₉ ＝ D ₂ (variable) r ₁₀ ＝ ∞ (diaphragm) d ₁₀ ＝ 1.913 r ₁₁ ＝ 35.831 d ₁₁ = 2.634 n ₀₆ Gradient distribution type lens r ₁₂ = −44.612 d ₁₂ = 0.100 r ₁₃ = 24.931 d ₁₃ = 2.800 n ₀₇ = 1.59270 ν ₀₇ = 35.29 r ₁₄ = −108.150 d ₁₄ = 1.159 r ₁₅ = − 26.351 d ₁₅ = 1.618 n ₀₈ = 1.80518 ν ₀₈ ＝ 25.43 r ₁₆ ＝ 32.157 d ₁₆ ＝ 2.362 r ₁₇ ＝ 239.410 d ₁₇ ＝ 2.831 n ₀₉ ＝ 1.62041 ν ₀₉ ＝ 60.27 r ₁₈ ＝ -21.614 d ₁₈ ＝ D ₃ (variable) _{r 19 = -38.559 d 19 = 3.650} n 010 = 1.78472 ν 010 = 25.68 r 20 = -21.025 d 20 = 2.800 r 21 = -17.065 d ₂₁ = 1.601 n ₀₁₁ = 1.78590 ν ₀₁₁ = 44.18 r ₂₂ = 470.539 f 39.52 63.11 100.80 D ₁ 2.023 6.683 11.177 D ₂ 11.928 7.269 2.774 D ₃ 15.494 8.206 2.500 Example 4 f = 39.52~100.80, F / 4.66~6.38 r 1 = 348.884 d 1 = 1.500 n 01 = 1.84666 ν 01 = 23.88 r 2 = 102.416 d 2 = 0.880 r 3 = 32.984 d 3 = 4.015 n 02 = 1.61800 ν ₀₂ ＝ 63.38 r ₄ ＝ －692.292 d ₄ ＝ D ₁ (variable) r ₅ ＝ －42.344 d ₅ = 1.300 n ₀₃ ＝ 1.80440 ν ₀₃ ＝ 39.58 r ₆ ＝ 15.287 d ₆ ＝ 2.506 n ₀₄ = 1.80518 ν ₀₄ ＝ 25.43 _{r 7 = 83.662 d 7 = D} 2 ( variable) r ₈ = ∞ _{(stop) d 8 = 1.913 r 9 =} 33.225 d 9 = 2.634 n 05 = 1.62012 ν 05 = 49.66 r 10 = -71.746 d 10 = 0.100 r 11 ＝ 24.813 d ₁₁ ＝ 2.800 n ₀₆ ＝ 1.62374 ν ₀₆ ＝ 47.10 r ₁₂ ＝ －46.320 d ₁₂ ＝ 1.159 r ₁₃ ＝ －25.590 d ₁₃ = 1.618 n ₀₇ = 1.80518 ν ₀₇ ＝ 25.43 r ₁₄ ＝ 24.380 d ₁₄ ＝ 2.362 r ₁₅ ＝ 73.296 d ₁₅ ＝ 2.831 n ₀₈ ＝ 1.62004 ν ₀₈ ＝ 36.25 r ₁₆ ＝ －21.044 d ₁₆ ＝ D ₃ (variable) r ₁₇ ＝ －30.707 d ₁₇ ＝ 3.632 n ₀₉ Gradient distribution type lens r ₁₈ ＝ －18.946 d ₁₈ = 2.578 r ₁₉ = -17.065 d ₁₉ = 1.601 n ₀₁₀ = 1.78650 ν ₀₁₀ = 50.00 r ₂₀ = 234.664 f 39.52 63.11 100.80 D ₁ 2.018 6.678 11.165 D ₂ 11.927 7.267 2.781 D ₃ 15.273 8.107 2.500 Where r ₁ , r ₂ , ... are the radii of curvature of each lens surface, d ₁ , d ₂ , ... are the wall thicknesses and lens intervals of each lens, n ₀₁ , n ₀₂ , ... are the refractive indices of each lens, ν ₀₁ , ν ₀₂ , ... Is the Abbe number of each lens. The refractive index distribution coefficients are shown for the d-line and the g-line.

Each of the above embodiments has a lens configuration as shown in FIGS. That is, the first lens group I includes at least one negative lens and at least one positive lens,
The second lens group II includes at least a cemented lens of a negative lens and a positive lens, the third lens group III includes two positive lenses, a negative lens and a positive lens, and a fourth lens group IV.
Is composed of a positive meniscus lens and a negative lens.

Example 1 is the third lens group having the lens configuration shown in FIG.
The first lens closest to the object in III is an axial type gradient index lens. In this embodiment, the above-mentioned gradient index lens is provided with a distribution in which the refractive index increases from the apex of the object side surface in the optical axis direction, so that the light ray height increases from the apex of the image side refracting surface to the refractive index. By lowering the index and controlling the degree of refraction, spherical aberration and coma are corrected in particular, and negative distortion is generated when propagating through the lens medium to contribute to correction of distortion at the telephoto end. ing. The aberration situation in this embodiment is as shown in FIG.

Example 2 has a lens configuration as shown in FIG. In this embodiment, the second lens group of the first lens group I is an axial type gradient index lens. This gradient index lens is designed to control the refraction of light rays incident on the refractive surface on the object side of the lens by adding a refractive index distribution from the object side so that the refractive index decreases in the optical axis direction. Therefore, astigmatism at the wide-angle end, spherical aberration at the telephoto end, and astigmatism are corrected. The aberration situation of this example is as shown in FIG.

The third embodiment is as shown in FIG. 3, and the first lens of the third lens group III is an axial type gradient index lens. In this embodiment, like the first embodiment, the refractive index distribution of the gradient index lens is so arranged that the refractive index increases from the object side toward the image side, but unlike the first embodiment, the third lens group Suppress the spherical aberration that occurs when III does not include the gradient index lens, and overcorrect the spherical aberration in the entire lens system to increase the curvature of the object-side refractive surface of the gradient index lens. Thus, the correction was made so that a negative spherical aberration was generated with respect to the incident light beam. Further, positive astigmatism is generated by increasing the refractive index gradient of the gradient index lens, that is, the third-order aberration coefficient equation shown below The term of is set to a positive and large value so that astigmatism in the entire system can be corrected well. The aberration situation in this example is the seventh.
As shown in the figure.

Example 4 is as shown in FIG. 4, and the first lens of the fourth lens group IV is an axial type gradient index lens.

At the wide-angle end, the fourth lens group IV passes through the lens group passing through different heights of the light flux that forms an on-axis image point and the light ray that forms an off-axis image point, and passes through a distance between them. Therefore, it is effective to correct the off-axis aberration without affecting the on-axis aberration. However, since the way of passing a ray passing through this lens group is greatly different between the wide-angle end and the telephoto end, if aberration correction is performed by focusing only on the wide-angle end, aberration variation in the fourth lens group becomes large. Therefore, it is necessary to pay attention to this point and perform aberration correction.

In Embodiment 4, as described above, the first lens unit of the fourth lens unit
The lens is an axial type gradient index lens, and various aberrations are satisfactorily corrected by providing an appropriate gradient index distribution. The refractive index distribution of this gradient index lens is set so that the refractive index increases from the object side in the optical axis direction, and the maximum refractive index difference between the apex of the object-side surface and the image-side surface. By setting the value to about 0.018, excessive aberration fluctuation is suppressed. By this effect, off-axis aberrations at the wide-angle end, spherical aberrations at the telephoto end, and astigmatism are corrected in good balance. The aberration situation of this example is as shown in FIG.

Since the lens system of the present invention uses a gradient index lens in its constituent elements, the third-order aberration coefficient is expressed in the following form.

Where σ _S ⁽ⁱ⁾ is the amount of aberration that occurs in the i-plane when a homogeneous optical material having the refractive index at the apex of the lens is used, and σ _HS ⁽ⁱ⁾ is obtained by using a gradient index lens. Aberration correction by changing the amount of refraction due to the change in refractive index at σ _HT
⁽ⁱ⁾ is the amount of aberration caused by the light beam drawing a curve when the light beam propagates from the i-th surface to the (i + 1) -plane by using the gradient index lens.

〔The invention's effect〕

As described above in detail and as apparent from the embodiments, the zoom lens of the present invention adopts a four-group zoom system, has an appropriate configuration, and uses an axial type gradient index lens. As a result, it is possible to obtain a compact one that has a zoom ratio of more than 2 times, has little aberration variation, and can be incorporated in a lens shutter camera or the like.

[Brief description of drawings]

1 to 4 are sectional views of Examples 1 to 4 of the zoom lens of the present invention, and FIGS. 5 to 8 are aberration curve diagrams of Examples 1 to 4 of the present invention, respectively. Is.

Claims (4)

[Claims] 1. A first lens group having a positive refracting power, a second lens group having a negative refracting power, and a third lens group having a positive refracting power in order from the object side.
A lens unit and a fourth lens unit having a negative refractive power, and each of the four lens units moves toward the object side along the optical axis during zooming from the wide end to the tele end, and at least one lens A compact high-magnification zoom lens in which at least one gradient index lens having a gradient index distribution in the optical axis direction is provided in the group, and which satisfies the following conditions. (1) 0.75 <f ₄ / f _W <2 where f _W is the focal length of the entire system at the wide end and f ₄ is the fourth
It is the focal length of the lens group. 2. A compact high-magnification zoom lens according to claim 1, which satisfies the following condition. (2) 1 <β _4T / β _4W <3 where β _4W is the lateral magnification of the fourth lens group at the wide-angle end, β
_4T is the lateral magnification of the fourth lens group at the telephoto end. 3. A compact high variable power zoom lens according to claim 2, which satisfies the following condition. (3) | β _3W | <0.75 (4) 0.5 <β _3T / β _3W <1.5 where β _3W and β _3T are lateral magnifications of the third lens group at the wide-angle end and the telephoto end, respectively. 4. A compact high-magnification zoom lens according to claim 1, which satisfies the following conditions. (5) Δn _A <0.15 (6) | n ₁ · f _W | <3.0 where Δn _A is the maximum refractive index difference between the apex of the object side surface and the apex of the image side surface on the off-axis.