JPH06230285A - Zoom lens - Google Patents

Abstract

PURPOSE:To shorten the total length of a lens, to reduce the lens diameter and to increase the variable magnification by composing the lens of five lens groups and making the photographying magnification, etc., of the respective lens groups specified values. CONSTITUTION:This lens comprizes five lens groups composed of a first group L1 of a positive refractive power, a second group L2 of a negative refractive power, a third group L3 of a positive refractive power, a fourth group L4 of a negative refractive power and a fifth group L5 of a positive refractive power. At the time of varying the power from a wide-angle end to a telescope end, the respective lens groups L1-L5 are moved so as to satisfy a prescribed condition. The optical characteristics of the respective lens groups L1-L5 are set so as to satisfy the conditions: 0.82<Z5/Z<3.0, 0.02<Z4/Z<0.12, -0.16< beta5w<-0.02 and -100<beta4w<-8. Here, betaiw is the photographying magnification of an (i)th group at the wide-angle end, Zi is the variable power ratio of an (i)th group at the telescope end to the wide-angle end and Z is the variable power ratio of the whole system at the telescope end to the wide-angle end. At the time of focusing from the object at infinity to the object at short distance, the second group L2 is drawn out toward the object side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens having a wide angle of view, which is suitable for a 35 mm camera, a video camera, an electronic still camera, etc., and in particular, has five lens groups as a whole and moves all the lens groups. The present invention relates to a zoom lens having a variable power ratio of about 4 and a high variable power ratio and a high optical performance over the entire variable power range.

[0002]

2. Description of the Related Art Conventionally, a zoom lens having a high zoom ratio and high optical performance has been required for a photographic camera, a video camera and the like. Among these, there is a demand for a zoom lens having a focal length at the wide-angle end that is shorter than the diagonal length of the screen, a zoom ratio of about 4, and high optical performance over the entire zoom range.

Japanese Patent Publication No. 61-55093 and Japanese Unexamined Patent Publication No.
In JP-A 8-127908, four lens groups are provided in order from the object side: a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. A four-group zoom lens having a zoom ratio of about 3 is disclosed. When trying to achieve a high zoom ratio of about 4 with these zoom lenses, there is a tendency that the entire lens system becomes large.

On the other hand, a small zoom lens having a high zoom ratio of about 4 has been disclosed in, for example, Japanese Patent Publication No. 58-335.
31 and Japanese Patent Laid-Open No. 60-39613. In these publications, a zoom lens is arranged in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, a fourth group having a negative refractive power, and a positive refractive power. It is composed of five lens units, which are the fifth lens unit for power.

In addition to this, Japanese Patent Laid-Open No. 63-189819 proposes a standard zoom lens including a relatively wide angle of view. In this publication, among the five lens groups having a predetermined refractive power, zooming from the wide-angle end to the telephoto end is performed by integrating the first group toward the object side, the third, fourth, and fifth groups integrally or by This is done by moving the lens group to the object side as a whole while changing the group interval.

Further, in Japanese Patent Laid-Open No. 2-168214, the first group having a positive refractive power and the second group having a negative refractive power are arranged in this order from the object side.
It has five lens groups, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power, and the fourth lens group upon zooming from the wide-angle end to the telephoto end. Is fixed, the air distance between the first group and the second group monotonically increases, and the air distance between the second group and the third group monotonically decreases, so that the first group is moved toward the object side.
A zoom lens is proposed in which the third group and the fifth group are integrated and moved to the object side.

As described above, the zoom type, which is composed of five lens groups as a whole, of which a plurality of lens groups are moved while changing the magnification while maintaining a constant relationship, secures a predetermined magnification ratio, Since it is easy to downsize the entire lens system, it is used for zoom lenses such as 35 mm cameras and video cameras.

[0008]

Generally, in a zoom lens, it is desired that the entire lens system be made compact and at the same time have a high magnification (high magnification). In order to increase the zoom lens magnification, it is necessary to increase the refracting power of the lens group that contributes to zooming, to strengthen the zooming effect, and to increase the amount of movement of the lens group that contributes to zooming. Will be.

However, in the former case, it becomes necessary to increase the number of lens components in order to satisfactorily correct various aberrations, which makes it difficult to make the entire lens system compact. .

In the latter case, a large space for moving the lens group must be secured and the total length of the lens becomes long. Especially when the moving form of the lens group is complicated, the lens barrel of the moving lens group is required. It becomes difficult to support the inside of the lens system, and it becomes difficult to make the entire lens system compact.

According to the present invention, the zoom lens as a whole is composed of five lens groups having a predetermined refracting power, and the refracting power of each lens group and the moving conditions of each lens group for varying the magnification are appropriately set. Accordingly, it is an object of the present invention to provide a zoom lens having a zoom ratio of 4 and a high zoom ratio, which has high optical performance over the entire zoom range, while shortening the overall lens length and reducing the diameter of the front lens.

[0012]

A zoom lens according to the present invention comprises, in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a negative refractive power. It has five lens groups, a fourth lens group of power and a fifth lens group of positive refracting power, and when zooming from the wide-angle end to the telephoto end, the distance between the first and second groups monotonically increases. , The distance between the second group and the third group decreases monotonically, the distance between the third group and the fourth group increases on the telephoto side, and the distance between the fourth group and the fifth group increases on the telephoto side. The first group, the third group, the fourth group, and the fifth group are moved to the object side, and the second group is moved to the object side or the image plane side so as to decrease, and a short distance from an infinite object When focusing on the object, the second lens unit is extended toward the object side, the imaging magnification of the i-th lens unit at the wide-angle end is βiw, and the zoom ratio of the i-th lens unit at the telephoto end to the wide-angle end is Z.
i, where Z is the zoom ratio of the telephoto end to the wide-angle end of the entire system: 0.82 <Z5 / Z <3.0 (1) 0.02 <Z4 / Z <0.12 (2) -0.16 <β5w <-0.02 (3) -100 <β4w <-8 (4) It has a feature.

[0013]

1 to 3 are cross-sectional views of lenses according to Numerical Examples 1 to 3 of the present invention. 4 to 6 are numerical examples 1 of the present invention.
4A to 4C are aberration diagrams. In the aberration diagram, (A) is the wide-angle end,
(B) shows the telephoto end.

In the figure, L ₁ is a first group having a positive refractive power, L ₂ is a second group having a negative refractive power, L ₃ is a third group having a positive refractive power, L ₄
Is the fourth group of negative refractive power, L ₅ is the fifth group of positive refractive power, S
P is a diaphragm. The arrows indicate the movement loci of the respective lens groups during zooming from the wide-angle end to the telephoto end.

In the present embodiment, when zooming from the wide-angle end to the telephoto end, the first to fifth lens units are arranged so that the above-mentioned conditions are satisfied.
By moving each lens group up to the group and setting the optical characteristics of each lens group so as to satisfy the above-mentioned conditional expressions (1) to (4), the variable magnification effect is shared among the lens groups in a well-balanced manner. , While making it possible to shorten the overall lens length and facilitate high zooming. The diaphragm SP is moved integrally with the third lens group.

When focusing from an object at infinity to an object at a short distance, the second lens unit is extended to the object side so that the aberration fluctuation during focusing is reduced.

Generally, from the object side, the first refractive power is first
In a so-called four-group zoom lens having four lens groups, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power, the total lens length is shortened and the magnification is changed ( In order to reduce the amount of lens movement during zooming and to reduce the diameter of the front lens, a method of increasing the refractive power of each lens group is adopted.

However, if the refracting power of the lens groups is strengthened in this way, it becomes difficult to correct aberrations by each lens group alone, and large aberration fluctuations will occur especially during zooming.

For example, in the first group having a relatively large zoom stroke as compared with the other lens groups, the negative displacement of spherical aberration is large during zooming. In addition, in the second group having a stronger refractive power than the other lens groups, not only spherical aberration but also astigmatism displacement in the positive direction becomes large during zooming.

In the third lens group, which has a relatively high refractive power next to the second lens group, coma tends to be displaced in the negative direction (inward coma) during zooming. Further, in the third lens unit, the height of the light beam incident on the third lens unit from the optical axis becomes high due to the diverging action of the second lens unit, so that high-order aberrations are significantly generated.

Therefore, it is necessary to increase the number of positive lenses in order to suppress the spherical aberration in particular, and as a result, the entire lens system becomes large.

Taking the behavior of spherical aberration as an example,
In the four-group zoom lens having the above-described configuration, the variation of the residual spherical aberration from the first group to the third group cannot be corrected between the lens groups, and the lens groups are largely displaced in the negative direction. In order to correct this, it is general to move the fourth lens unit to eliminate the fluctuation of spherical aberration (floating action).

At this time, since the fourth lens group has almost no zooming action, as a result, the zooming load of the second lens group and the third lens group becomes large, and it is attempted to obtain a high zooming ratio by keeping the total lens length small. When you do, the limits will naturally come out. Therefore, in order to achieve high zooming and downsizing, the zooming load of the second and third groups is reduced, and highly efficient zooming is achieved in the entire lens system without significantly increasing the refractive power of each lens group. Will be required.

Therefore, the zoom lens of the present invention has five lens groups having a predetermined refracting power as described above, and the moving conditions, photographing magnification, etc. associated with the magnification change of each lens group are appropriately set, and each lens group By appropriately sharing the variable magnification, it is possible to easily achieve a high variable magnification while maintaining good optical performance.

In particular, in the present invention, the variable power distribution of the fifth lens group is increased, the variable power distribution of the second lens group and the third lens group is suppressed, and a highly efficient variable power is obtained for the entire lens system, whereby each lens group We have obtained a high zoom ratio and compact zoom lens without making the refracting power of the extremely strong.

Next, the technical meanings of the above conditional expressions will be described.

Conditional expression (1) represents the ratio of the fifth group to the zoom ratio of the entire system, and the larger the value is, the larger the variable share of the fifth group is. If the variable ratio of the fifth lens unit is increased beyond the upper limit of conditional expression (1), the moving amount of the fifth lens unit is increased, and it is necessary to secure a space for the movement, and the lens system is large in size together with the front lens diameter. Turn into.

Further, as the amount of movement increases, the height from the optical axis of the light beam incident on the fifth group at the wide-angle end and the telephoto end greatly changes, so spherical aberration and coma aberration fluctuate, and other lens groups change. And it is not good because the fluctuation cannot be corrected within the fifth group.

On the contrary, when the lower limit of conditional expression (1) is exceeded and the variable power distribution of the fifth lens unit becomes small, the variable power distribution of the second lens unit and the third lens unit becomes large, and the refracting power of the second lens unit and the third lens unit becomes large. Are both stronger. At that time, especially spherical aberration is deteriorated in both low-order and high-order regions, coma aberration and astigmatism are deteriorated, and aberration fluctuation during zooming is greatly changed, which is not preferable.

Conditional expression (2) represents the ratio of the entire system of the fourth group to the zoom ratio, and the larger the value, the fourth
It means that the variable magnification is increased in the group. Although the fourth group itself has a demagnifying effect, it functions to connect the image points in the direction in which the zooming effect of the fifth group is intensified with the position of the image point of the third group as the object point.

Even if the upper limit or the lower limit of the conditional expression (2) is exceeded, the balance of the variable power distribution between the fifth lens group, the second lens group, and the third lens group is lost, and the lens system is made compact to achieve high zooming power. It's not good because it can't be achieved.

Conditional expressions (3) and (4) are photographing magnifications of the fifth group and the fourth group at the wide-angle end, and conditional expressions (1) and (4)
This is to achieve the variable magnification share of (2) and to shorten the total lens length at the wide-angle end while maintaining the optical performance and the desired back focus.

When the upper limit of the conditional expression (3) is exceeded and the absolute value of the image pickup magnification of the fifth lens unit becomes small, it becomes difficult to secure the back focus, and the lens interval between the fourth lens unit and the fifth lens unit becomes long, and the lens length increases. This is not preferable because the lens diameter of the fifth lens group or the front lens diameter increases in order to obtain a desired peripheral light amount at the same time as the total length becomes long.

On the contrary, when the absolute value of the photographing magnification of the fifth lens unit becomes large beyond the lower limit value of the conditional expression (3), the back focus is secured but the distance between the fourth lens unit and the fifth lens unit becomes narrower, which is a desired value. This is not good because the amount of movement of the fifth lens unit to obtain the variable power ratio becomes large.

When the absolute value of the image pickup magnification of the fourth lens unit becomes smaller than the upper limit of the conditional expression (4), the divergence of the light beam emitted from the fourth lens group with respect to the incident light beam is weakened, which is slightly advantageous for aberration correction. This is not good because the back focus becomes shorter.

On the contrary, when the absolute value of the photographing magnification of the fourth lens unit is increased beyond the lower limit value of the conditional expression (4), the divergence of the light beam emitted from the fourth lens group with respect to the incident light beam is increased and it becomes difficult to correct the aberration. It's not good because it comes.

Although the deterioration of astigmatism is relatively small, the spherical aberration is overcorrected, and the fluctuation due to zooming becomes large. Then, inward coma often occurs on the telephoto side. Further, the back focus becomes long, the total lens length becomes long, and the diameter of the front lens increases, which is not preferable.

In the present invention, in order to correct aberration fluctuations and obtain high optical performance over the entire zoom range while achieving high zoom ratio, it is preferable to configure each lens group as follows.

In order from the object side, the first group is made up of three groups of three lenses, namely, a cemented lens of a meniscus negative lens having a concave surface facing the image side and a positive lens, and a meniscus positive lens having a convex surface facing the object side. The second group is composed of four meniscus negative lenses having a strongly concave surface facing the image side, a negative lens, a positive lens and a negative lens, and the third group is at least two positive lenses and at least one meniscus. A negative lens, and at least one meniscus negative lens and at least one positive lens are cemented together, and the fourth group includes at least one positive lens and at least one negative lens. ,
At least one positive lens and at least one negative lens are cemented together, and the fifth lens unit has at least a positive lens and a positive lens with a strong convex surface facing the image side and a strong concave surface toward the object side. That is, the configuration includes a negative lens.

In the present invention, focusing is performed by moving the second lens unit toward the object side so that an object at infinity can be focused on an object at a short distance. By adopting this method, the front lens (first group) when compared at the same close range
The increase in the front lens diameter for obtaining a desired amount of peripheral light is suppressed as compared with focusing.

In the present invention, it is preferable that the following conditions be satisfied during focusing.

1.0 <ESw (5) Here, ESw is the moving amount of the image point with respect to the unit moving amount of the second lens unit at the wide angle end, and is given by the following.

ESw = (1−β2w ² ) · β3w ² · β
4w ² · β5w ² where βiw is the photographing magnification of each lens group at the wide-angle end. That is, when ESw has a large value, the amount of extension of the second group becomes small, and vice versa.

If conditional expression (5) is not satisfied, the amount of extension of the second lens unit during focusing will increase, and the air space between the first lens unit and the first lens unit will have to be wide, which not only increases the overall lens length, but also increases the front distance. It is not good because the ball diameter increases.

In Numerical Example 2, by providing R25 with an aspherical surface whose negative refracting power weakens toward the periphery of the lens, the fluctuations of spherical aberration, coma and astigmatism associated with zooming can be satisfactorily corrected. is doing.

Next, numerical examples of the present invention will be shown. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air gap from the object side, and Ni and νi are respectively from the object side of the i-th lens. The refractive index of glass and the Abbe number.

The aspherical shape has an X axis in the optical axis direction, an H axis in a direction perpendicular to the optical axis, a positive light traveling direction, and R as paraxial radiuses of curvature A, B, C, D, and E, respectively. When

[0048]

[Equation 1] It is expressed by Table 1 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples. (Numerical Example 1) F = 29 to 101 FNO = 1: 3.5 to 4.6 2 ω = 73 ° to 24 ° R 1 = 100.57 D 1 = 2.00 N 1 = 1.84666 ν 1 = 23.8 R 2 = 50.50 D 2 = 5.70 N 2 = 1.69680 ν 2 = 55.5 R 3 = 233.31 D 3 = 0.12 R 4 = 45.95 D 4 = 4.80 N 3 = 1.71300 ν 3 = 53.8 R 5 = 130.54 D 5 = variable R 6 = 58.72 D 6 = 1.20 N 4 = 1.83400 ν 4 = 37.2 R 7 = 13.17 D 7 = 5.73 R 8 = -70.16 D 8 = 1.10 N 5 = 1.80 400 ν 5 = 46.6 R 9 = 33.86 D 9 = 0.10 R10 = 22.71 D10 = 4.35 N 6 = 1.84666 ν 6 = 23.9 R11 = -52.07 D11 = 0.60 R12 = -30.56 D12 = 1.10 N 7 = 1.83481 ν 7 = 42.7 R13 = 345.58 D13 = Variable R14 = (Aperture) D14 = 0.00 R15 = 24.44 D15 = 1.20 N 8 = 1.84666 ν 8 = 23.8 R16 = 13.71 D16 = 5.85 N 9 = 1.60311 ν 9 = 60.7 R17 = -42.36 D17 = 0.12 R18 = 29.24 D18 = 2.05 N10 = 1.77250 ν10 = 49.6 R19 = 72.04 D19 = variable R20 = -51.38 D20 = 3.35 N11 = 1.75520 ν11 = 27.5 R21 = -12.69 D21 = 1.10 N12 = 1.80400 ν12 = 46.6 R22 = 87.85 D22 = Variable R23 = 214.12 D23 = 5.45 N13 = 1.48749 ν13 = 70.2 R24 = -17.47 D24 = 0.12 R25 = 70.48 D25 = 2.60 N14 = 1.69680 ν14 = 55.5 R26 = -89.32 D26 = 3.04 R27 = -18.09 D27 = 1.40 N15 = 1.84666 ν1 5 = 23.8 R28 = -58.27

[0049]

[Table 1] (Numerical Example 2) F = 29 to 101.6 FNO = 1: 3.5 to 4.6 2ω = 73 ° to 24 ° R 1 = 112.67 D 1 = 2.00 N 1 = 1.84666 ν 1 = 23.8 R 2 = 50.62 D 2 = 5.89 N 2 = 1.69187 ν 2 = 55.6 R 3 = 343.43 D 3 = 0.12 R 4 = 43.02 D 4 = 4.83 N 3 = 1.72440 ν 3 = 53.0 R 5 = 119.69 D 5 = Variable R 6 = 54.27 D 6 = 1.20 N 4 = 1.83578 ν 4 = 36.6 R 7 = 12.78 D 7 = 5.44 R 8 = -62.15 D 8 = 1.10 N 5 = 1.77109 ν 5 = 49.7 R 9 = 33.91 D 9 = 0.21 R10 = 21.95 D10 = 4.25 N 6 = 1.84666 ν 6 = 23.9 R11 = -48.49 D11 = 1.07 R12 = -27.59 D12 = 1.10 N 7 = 1.82698 ν 7 = 43.5 R13 = 154.99 D13 = Variable R14 = (Aperture) D14 = 0.00 R15 = 25.15 D15 = 1.20 N 8 = 1.84666 ν 8 = 23.8 R16 = 13.86 D16 = 5.67 N 9 = 1.60505 ν 9 = 60.6 R17 = -47.24 D17 = 0.12 R18 = 35.08 D18 = 2.24 N10 = 1.80412 ν10 = 46.6 R19 = 233.91 D19 = variable R20 = -55.61 D20 = 2.99 N11 = 1.74473 ν11 = 27.9 R21 = -13.81 D21 = 1.10 N12 = 1.80779 ν12 = 46.2 R22 = 93.38 D22 = Variable R23 = 239.63 D23 = 5.50 N13 = 1.50802 ν13 = 70.2 R24 = -18.22 D24 = 0.12 R25 = 71.29 (aspheric surface) D25 = 2.87 N14 = 1.58313 ν14 = 59.4 R26 = -88.80 D26 = 3.22 R27 = -18.26 D27 = 1 .40 N15 = 1.84666 ν15 = 23.8 R28 = -49.64

[0050]

[Table 2] (Numerical Example 3) F = 29 to 101 FNO = 1: 3.5 to 4.6 2ω = 73 ° to 24 ° R 1 = 118.15 D 1 = 2.00 N 1 = 1.84666 ν 1 = 23.8 R 2 = 53.76 D 2 = 5.93 N 2 = 1.65160 ν 2 = 58.5 R 3 = 489.68 D 3 = 0.12 R 4 = 43.31 D 4 = 4.93 N 3 = 1.71300 ν 3 = 53.8 R 5 = 120.72 D 5 = variable R 6 = 61.63 D 6 = 1.20 N 4 = 1.83400 ν 4 = 37.2 R 7 = 13.11 D 7 = 5.49 R 8 = -76.59 D 8 = 1.10 N 5 = 1.77250 ν 5 = 49.6 R 9 = 32.49 D 9 = 0.11 R10 = 22.01 D10 = 4.42 N 6 = 1.84666 ν 6 = 23.9 R11 = -56.97 D11 = 1.54 R12 = -31.43 D12 = 1.10 N 7 = 1.83638 ν 7 = 42.4 R13 = 182.58 D13 = Variable R14 = (Aperture) D14 = 0.00 R15 = 25.27 D15 = 1.10 N 8 = 1.84666 ν 8 = 23.8 R16 = 13.43 D16 = 4.50 N 9 = 1.62375 ν 9 = 59.7 R17 = 554.40 D17 = 0.12 R18 = 51.31 D18 = 2.02 N10 = 1.80384 ν10 = 47.7 R19 = -846.45 D19 = 0.12 R20 = 55.75 D20 = 2.03 N11 = 1.81019 ν11 = 46.0 R21 = -261.23 D21 = variable R22 = -59.76 D22 = 3.02 N12 = 1.75195 ν12 = 27.4 R23 = -13.86 D23 = 1.10 N13 = 1.81688 ν13 = 46.7 R24 = 61.16 D24 = variable R25 = 214.70 D25 = 5.50 N14 = 1.48749 ν14 = 70.2 R26 = -17.55 D26 = 0.12 R27 = 46.19 D27 = 3.05 N15 = 1.60311 ν1 5 = 60.7 R28 = -114.02 D28 = 2.87 R29 = -19.14 D29 = 1.30 N16 = 1.84666 ν16 = 23.8 R30 = -63.90

[0051]

[Table 3]

[0052]

[Table 4]

[0053]

According to the present invention, the zoom lens as a whole is composed of five lens groups having a predetermined refractive power,
By setting the moving conditions of each lens unit and the lens configuration of each lens unit with zooming as described above, the total lens length and the front lens diameter can be shortened, and aberration variation over the entire zoom range. It is possible to achieve a compact zoom lens having a variable power ratio of 4, and an F number of about 3.5, which has a high optical performance with a small number of lenses.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view of Numerical Example 1 of the present invention.

FIG. 2 is a lens cross-sectional view of Numerical Example 2 of the present invention.

FIG. 3 is a lens cross-sectional view of Numerical Example 3 of the present invention.

FIG. 4 is an aberration diagram of Numerical example 1 of the present invention.

FIG. 5 is an aberration diagram of Numerical example 2 of the present invention.

FIG. 6 is an aberration diagram of Numerical example 3 of the present invention.

[Explanation of symbols]

L ₁ 1st group L ₂ 2nd group L ₃ 3rd group L ₄ 4th group d d line g g line SC Sine condition ΔS Sagittal image plane ΔM Meridional image plane

Claims (1)

[Claims] 1. A first group of positive refracting power, a second group of negative refracting power, a third group of positive refracting power, a fourth group of negative refracting power and a positive refracting power of a positive refracting power in order from the object side. The zoom lens system has five lens units, which are the fifth lens unit, and the distance between the first lens unit and the second lens unit increases monotonically during zooming from the wide-angle end to the telephoto end. The first group, the first group, the second group so that the distance between the third group and the fourth group increases on the telephoto side, and the distance between the fourth group and the fifth group decreases on the telephoto side. The third group, the fourth group, and the fifth group are moved to the object side, and the second group is moved to the object side or the image plane side, respectively, and when focusing from an object at infinity to a near object, the second group is moved. To the object side, the imaging magnification of the i-th group at the wide-angle end is βiw, the zoom ratio of the i-th lens unit at the telephoto end to the wide-angle end is Zi, and the zoom ratio of the entire system to the telephoto end is Z. 0.82 <Z5 / Z <3.0 0.02 <Z4 / Z <0.12-0.16 <[beta] 5w <-0.02-100 <[beta] 4w <-8 A zoom lens characterized by satisfying the following condition.