JPH11119098A - Small-sized zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accomplish drastic miniaturization for a zoom lens and to obtain a high performance by constituting the lens of three groups, each of which has a positive refractive power, a positive one and a negative one, respectively, from an object side, moving each group to the object side in the case of varying the power from a wide angle end to a telephoto end, and also, satisfying specified conditions. SOLUTION: The lens is constituted of the 1st to 3rd lens groups G1 to G3 having the positive refractive power, the positive one and the negative one, respectively from the object side in order, and in the case of varying the power from the wide angle end to the telephoto end, each lens group G1 to G3 is moved to the object side by taking the wide angle end as a reference. The 1st group G1 is constituted of negative and positive lenses, each of which has a convex face on the object side, the 2nd group G2 is constituted of a 1st lens which has a convex face on the object side and a 2nd positive lens which has a face of curvature on the image side, and the 3rd lens group G3 is constituted of a positive lens having a convex face on the image side and a negative lens having a face of curvature on the object side. Each lens group G1 to G3 is provided with at least one aspherical surface, and satisfies the following inequalities; 0.1<ϕ1 /ϕW<0.6 and 1.3<m3 T/m3 W<4W. Provided that the synthetic refractive power of the 1st group G1 at the wide angle end is expressed by ϕ1 , the refractive power of the whole system is expressed by ϕW, the horizontal magnification of the 3rd group G3 at the wide angle end is expressed by m3 W and the horizontal magnification at the telephoto end is expressed by m3 T.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small zoom lens, and more particularly to a small zoom lens applied to an optical system of a conventional compact camera or electronic image equipment.

[0002]

2. Description of the Related Art The basic form of a zoom lens according to the present invention described later is disclosed in Japanese Patent Publication No. 8-3580 by the present applicant, but a method of shortening the overall length as a hybrid configuration by using a small aperture ratio and using an aspherical surface. Has already been proposed.
For example, JP-A-4-260016, JP-A-4-362
No. 910, JP-A-5-113538, JP-A-5-18
No. 8296, JP-A-6-67093, JP-A-8-10
1341 and JP-A-8-262325.
These are proposals incorporating the idea that each lens unit has an achromatized lens configuration, and that the performance is improved by using an aspherical surface against performance degradation due to reduction in the number of lens components. However, in each case, only the result that the aperture ratio is about 1: 8 to 1:10 at the telephoto end where the maximum aperture diameter is maximum is obtained.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and has as its object to correct spherical aberration on the telephoto side, which is a problem in increasing the aperture ratio, and to reduce the aperture ratio. Accordingly, it is an object of the present invention to provide a zoom lens which achieves a reduction in the number of lens components and a reduction in the size of the lens system, in response to the deterioration of aberration caused by an increase in the amount of peripheral light, which becomes necessary due to an increase in the lens size.

[0004]

According to the present invention, there is provided a small-sized zoom lens which, in order from the object side, has a first unit having a positive refractive power, a second unit having a positive refractive power, and a second unit having a negative refractive power. When zooming from the wide-angle end to the telephoto end, each group moves to the object side with respect to the wide-angle end, and the first group is a negative meniscus lens having a convex surface facing the object side. The second group is composed of a first meniscus lens having a convex surface facing the object side and a second lens of a positive lens having a surface with a strong curvature on the image side. Consists of a positive meniscus lens having a convex surface facing the image side and a negative lens having a surface with a strong curvature on the object side, and each lens group has at least one aspheric surface and satisfies the following conditions. It is characterized by the following. 0.1 <φ ₁ / φ _W <0.6 (1) 1.3 <m _3T / m _3W <4 (2) where φ ₁ is the combined refraction of the first lens unit at the wide-angle end. Power, φ _W is the refractive power of the entire system at the wide-angle end, m _3W is the lateral magnification of the third lens unit at the wide-angle end, and m _3T is the lateral magnification of the third lens unit at the telephoto end.

Another small 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 positive refractive power, and a third group having a negative refractive power. When zooming from the wide-angle end to the telephoto end, each group moves to the object side,
The group includes a positive lens having a convex surface facing the object side and a negative lens. The second group includes an aperture stop, a first meniscus lens having a convex surface facing the object side, and a convex surface having a strong curvature on the image side. The third group is composed of a positive meniscus lens having a convex surface facing the image side and a negative lens having a strong curvature surface on the object side. Has at least one aspheric surface and satisfies the following conditions. 0.1 <φ ₁ / φ _W <0.6 (1) 1.3 <m _3T / m _3W <4 (2) where φ ₁ is the combined refraction of the first lens unit at the wide-angle end. Power, φ _W is the refractive power of the entire system at the wide-angle end, m _3W is the lateral magnification of the third lens unit at the wide-angle end, and m _3T is the lateral magnification of the third lens unit at the telephoto end.

In these cases, it is desirable that the first lens of the second group is constituted by a negative meniscus lens.
It is also desirable to use an aspheric surface on the object side surface of the first lens of the second group. It is desirable that the Abbe number of the medium of the second lens of the second group satisfies the following condition. ν _d > 60 (3) where ν _d is the Abbe number of the medium of the second lens of the second group.

Hereinafter, the reason and operation of the above-described configuration in the present invention will be described. In recent years, zoom lenses for compact cameras have been compared to single-lens reflex cameras.
The telephoto side aperture ratio is greatly reduced. That is, reduction in the number of lens components is realized by reducing the size and weight.

In the present invention, an attempt is made to compare the performance with a conventional lens system using only a spherical surface, and the aim is to maintain the performance as much as possible even if the size is reduced. In other words, the aperture ratio is set to the same level as the aperture ratio shown in the basic form by the present applicant. This was intended to be achieved by effective use of the lens configuration and aspherical surface. The zoom lens type is a three-group zoom lens as shown in Japanese Patent Publication No. 8-3580 by the present applicant, and is as follows. Further, the lens configuration is intended to reduce the number of components themselves and downsize the lens system.

That is, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power are provided. This is a zoom lens type in which each group moves to the object side with respect to the wide angle end.

With this power arrangement, it is possible to make the overall length of the lens extremely short at the wide-angle end. A feature of this zoom lens is that a large zoom ratio can be achieved in the lens system depending on the zoom ratio due to the movement of the third unit. In this regard, it is clear that a higher performance potential is inherent in the two-unit zoom lens composed of the positive first unit and the negative second unit in order from the object side. Also, by reducing the number of lens components,
Although the overall length at the wide-angle end is shortened, the effective use of aspherical surfaces,
Alternatively, a radial GRI capable of correcting chromatic aberration
There is a method of using an N lens.

In order to shorten the overall length of the lens, as long as the zoom lens is used, it is necessary to correct chromatic aberration in each group in order to minimize fluctuations during zooming. It is required to use a radial GRIN lens. The present invention realizes optimizing the configuration of the lens system and compensating for the aberration correction capability that changes due to simplification of the lens configuration by effectively using an aspheric surface. According to the following relational expression, a great effect can be expected for the paraxial configuration of the zoom lens in this case. That is, the relationship between the refractive power of the first lens unit and the zooming unit of the third lens unit satisfies Expressions (1) and (2).

0.1 <φ ₁ / φ _W <0.6 (1) 1.3 <m _3T / m _3W <4 (2) Conditional expression (1) is intended for miniaturization. This is a relational expression that determines the overall length of the lens when the zooming is performed, and relates to the refractive power of the first lens group. Exceeding the upper limit of 0.6 to condition (1) is suitable for miniaturization, but is undesired in correcting aberrations, because it deteriorates peripheral performance at the wide-angle end, deteriorates chromatic aberration, and increases field curvature. . If the lower limit of 0.1 is exceeded, the aberration correction surface is good, but the overall length is large, so that it does not meet the gist of the present invention.

Conditional expression (2) means the zoom ratio by the paraxial lateral magnification of the third lens unit.
Configuration becomes difficult. If the lower limit of 1.3 is exceeded, the zoom range will be narrowed, and the advantage of this type of zoom lens will be lost.

Next, the lens configuration will be described. The first group includes a negative meniscus lens having a convex surface facing the object side and a positive lens. The second group includes a negative meniscus lens having a convex surface facing the object side and a positive lens having a strong curvature surface on the image side. The third group is composed of a positive meniscus lens having a convex surface facing the image side and a negative lens having a strong curvature surface on the object side, and each lens group uses at least one aspheric surface. I do.

If the first lens unit is composed of a negative lens and a positive lens from the object side, the negative lens of the first lens will have a concave surface facing the object side even if the overall length is short on the optical axis to maintain the back focus. Easy to be. In the present invention, the negative lens of the first lens is also constituted by a negative meniscus lens having a convex surface having a relatively small curvature directed to the object side in order to reduce the overall length of the lens. As the positive lens, a positive lens having a strong curvature is disposed on the object side for correcting spherical aberration. In the second group, a negative meniscus lens having a relatively small power with the convex surface facing the object side and a positive lens having a strong curvature on the image side are arranged at a somewhat wide axial interval. This configuration prevents extremely large high-order aberrations from occurring between the negative lens and the positive lens.

In the use of the aspherical surface in the second lens group,
The use of the front surface of the first lens and the image side surface of the second lens is effective. The former relates to distortion correction, but has a great effect on astigmatism at the wide-angle end. The latter can be expected to have a great effect on coma aberration correction. On other surfaces, it can be said that spherical aberration correction is large. This is a necessary technique when a large system ratio is required.

The third unit includes a positive meniscus lens and a negative lens. The configuration of the third lens group is closely related to aberration correction at the wide-angle end, and the use of an aspherical surface is the most effective part in flattening the image surface. Also, regarding the use of an aspherical surface, the first surface of the second lens group is particularly involved in correcting astigmatism, generating higher-order aberrations and sometimes having a undulating shape. Great effect for correction.

The first lens group has a large outer shape and is indispensable for stable correction of off-axis aberrations. Since a significant difference in effect due to the aspherical lens surface in the first group cannot be obtained, the first lens group is manufactured. It is advisable to determine the part to be used in consideration of the surface. However, when an air lens is provided, since this surface is a surface on which higher-order aberrations occur, it can be said that the use of another surface increases the degree of freedom of aberration correction.

Further, in order to reduce the power of the first lens of the second group, it is desirable that the glass material used for the second lens satisfies the following condition of small dispersion.

Ν _d > 60 (3) where ν _d is the Abbe number of the medium of the second lens of the second group.

If possible, glass having anomalous dispersibility is desirable. This is because the power of the first lens of the second group is reduced, so that it is required that the second lens be independently corrected for chromatic aberration.

As another structure, the structure of the first group is as follows.
Consisting of a positive lens with a convex surface facing the object side and a negative lens,
The second group includes an aperture stop, a negative meniscus lens having a convex surface facing the object side, and a positive lens having a convex surface having a strong curvature facing the image side. The third group includes a positive meniscus having a convex surface facing the image side. A zoom lens composed of a lens and a negative lens having a surface with a strong curvature on the object side, and using at least one aspheric surface for each lens group is established. In view of the achromatic condition, it is possible to configure a lens system with this configuration of the first group.

In particular, in the case where a negative lens of the first group is disposed on the object side and then a positive lens is disposed, it is known as a basic system. However, the negative lens as the first lens has a relatively small power. It is not unusual to have a concave surface facing the object side. In this case, even if the total length by the optical axis distance is short,
There is a fact that the actual overall length is determined by the lens outer diameter. This is because the negative lens arranged on the object side of the positive / negative two-unit zoom lens tends to have the same shape. To avoid this, the positive lens may be arranged on the object side in the configuration of the first group.

That is, in order from the object side, the first lens unit has a positive refractive power, a second lens unit has a positive refractive power, and a third lens unit has a negative refractive power. Each group moves to the object side, the first group is composed of a positive lens and a negative lens having a convex surface facing the object side, and the second group is composed of an aperture stop and a negative meniscus having a convex surface facing the object side. The third group is composed of a lens and a positive lens having a convex surface with a strong curvature on the image side. The third group is composed of a positive meniscus lens having a convex surface on the image side and a negative lens having a surface with a strong curvature on the object side. And each lens group has at least one aspheric surface.
Regarding conditional expressions, there is the same relationship as described above.

Each lens constituting the first to third groups of the present invention is a concept including a single lens and a cemented lens, but if more compact lens system is required,
It is desirable that all the lenses are constituted by a single lens as described below. That is, each of the groups is composed of only two lenses, and the total lens length at the wide-angle end can be reduced by making the lens configuration three and six.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 7 of the zoom lens according to the present invention will be described below. FIGS. 1 to 6 show lens sectional views including the optical axis at the wide-angle end (a), the intermediate focal length (b), and the telephoto end (c) of Examples 1 to 4, 6, and 7, respectively. The fifth embodiment is the same as FIG. 4 and is not shown. Numerical data of each embodiment will be described later.

FIG. 1 is a sectional view of a zoom lens according to the first embodiment. In this embodiment, the focal length is 38.9 to 102.
5, F-number 4.5-5.6 zoom lens,
The aperture ratio at the telephoto end is 5.6, which is larger than previous proposals.
And the lens configuration is six.

The first group G1 of the zoom lens includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second group G2 includes an aperture stop and an object side. The third group G3 is composed of a positive meniscus lens having a convex surface facing the image side and a bi-convex lens having a stronger curvature of the image side surface. Consists of a strong biconcave lens.

In order to stabilize optical performance with this configuration,
The front surface of the second lens (positive meniscus lens) of the first group G1, the front surface of the first lens (negative meniscus lens) of the second group G2, both surfaces of the second lens (biconvex lens), and the first lens of the third group G3 Aspheric surfaces are used on the front surface of the (positive meniscus lens) and the front surface of the second lens (biconcave lens). In this configuration, the effect of the aspherical surface used for the first surface of the negative meniscus lens of the second group G2 is effective in correcting astigmatism in a wide-angle region, but is seen in the astigmatism in the aberration diagram described later. As described above, an aberration shape showing undulation on the wide-angle side may occur.
In the third group G3, the use of an aspheric surface for the positive meniscus lens is effective in correcting field curvature in a wide-angle region.
As shown in the lens cross-sectional view of FIG. 1, this zoom lens has a very simple configuration. The lens outer diameter depends on the aperture ratio. The aperture stop is arranged on the object side of the second group G2. In this lens configuration, it is not desirable to dispose an aperture stop on the image side of the second group G2. FIG. 7 shows aberration diagrams of this embodiment. In the drawing, (a) is the wide-angle end, (b) is the intermediate focal length, (c) is the axial spherical aberration SA at the telephoto end,
9 shows astigmatism AS and distortion DT (the same applies hereinafter). This shows that stable performance is obtained from the wide-angle end to the telephoto end. Also, it can be seen that the distortion is very small.

FIG. 2 is a sectional view of a zoom lens according to the second embodiment. This embodiment has a focal length of 38.9 to 102.
5, F-number 4.5-5.7 zoom lens,
There are six lenses.

The first group G1 of the zoom lens includes a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side. The second group G2 has an aperture stop and an object side. The third group G3 is composed of a positive meniscus lens having a convex surface facing the image side and a bi-convex lens having a stronger curvature of the image side surface. It consists of a negative meniscus lens with the convex surface facing the strong image side.

In order to further enhance the optical performance in this configuration, one aspheric surface is added to the first lens unit G1. That is, the front surface of the first lens (positive meniscus lens), the front surface of the second lens (negative meniscus lens), and the second surface of the first group G1.
The front surface of the first lens (negative meniscus lens) of the group G2, both surfaces of the second lens (biconvex lens), the front surface of the first lens (positive meniscus lens) of the third group G3, and the front surface of the second lens (negative meniscus lens) Uses an aspheric surface.

In this configuration, a positive lens is disposed on the object side of the first group G1. In the third group G3, the use of aspherical surfaces for the positive meniscus lens and the negative meniscus lens has an effect on correction of field curvature in a wide-angle region.
As shown in the lens cross-sectional view of FIG. 2, in this zoom lens, the distance between the two lenses of the second group G2 is narrow.
As shown in the aberration diagram in FIG. 8, it can be seen that the aberration amount including the axial chromatic aberration is smaller than in the first embodiment.

FIG. 3 is a cross-sectional view of the zoom lens according to the third embodiment. This embodiment has a focal length of 38.9 to 102.
5, a zoom lens having an F number of 4.5 to 5.51, and six lenses.

The first group G1 of the zoom lens comprises a biconvex lens having a stronger curvature on the object side and a biconcave lens having a stronger curvature on the image side. The second group G2 has an aperture stop, The third group G3 is composed of a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the image side where the curvature of the image side surface is stronger. And a biconcave lens having a stronger curvature of the object side surface.

In this configuration, the front surface of the first lens (biconvex lens) of the first group G1, the rear surface of the second lens (biconcave lens), the front surface of the first lens (negative meniscus lens) of the second group G2, the second surface Third side of lens (positive meniscus lens)
Aspheric surfaces are used on the front surface of the first lens (positive meniscus lens) and the front surface of the second lens (biconcave lens) of the group G3.

This embodiment is an example in which the aberration balance is different from that of the second embodiment. In particular, it can be seen from the aberration diagram of FIG. 9 that the shape of spherical aberration at the telephoto end has changed due to a change in the method of using glass.

FIG. 4 is a sectional view of a zoom lens according to the fourth embodiment. This embodiment has a focal length of 38.9 to 132.5.
5, a zoom lens having an F number of 4.45 to 8.01 and a six-lens configuration.

The first group G1 of the zoom lens includes a biconvex lens and a biconcave lens, and the second group G2 includes an aperture stop, a negative meniscus lens having a convex surface facing the object side, and a curvature of the image side surface. The third group G3
Is composed of a positive meniscus lens having a convex surface facing the image side and a biconcave lens having a stronger curvature on the object side surface.

In this configuration, the front surface of the first lens (biconvex lens) of the first group G1, the rear surface of the second lens (biconcave lens), the front surface of the first lens (negative meniscus lens) of the second group G2, the second surface Aspheric surfaces are used on both surfaces of the lens (biconvex lens), the front surface of the first lens (positive meniscus lens), and the front surface of the second lens (biconcave lens) of the third group G3.

The zoom ratio of this embodiment is larger than that of the above embodiments. In order to enhance the optical performance with this configuration, the effect of the two aspheric surfaces of the first group G1 is increased in the configuration of the second embodiment. This is the same for the following embodiment 5, which is a necessary means for coping with a high zoom ratio. As shown in the aberration diagram of FIG. 10, stable performance is obtained.

The sectional view of the zoom lens of Embodiment 5 is similar to that of FIG. 4, and this embodiment has a focal length of 38.9 to 17
This is a zoom lens having a 6.2 and an F number of 4.45 to 10.66, and has six lenses.

The first group G1 of the zoom lens includes a biconvex lens and a biconcave lens, and the second group G2 includes an aperture stop, a negative meniscus lens having a convex surface facing the object side, and a curvature of the image side surface. The third group G3
Is composed of a positive meniscus lens having a convex surface facing the image side and a biconcave lens having a stronger curvature on the object side surface.

In this configuration, the front surface of the first lens (biconvex lens) of the first group G1, the rear surface of the second lens (biconcave lens), the front surface of the first lens (negative meniscus lens) of the second group G2, the second surface Aspheric surfaces are used on both surfaces of the lens (biconvex lens), the front surface of the first lens (positive meniscus lens), and the front surface of the second lens (biconcave lens) of the third group G3.

The zoom ratio of this embodiment is larger than that of the above embodiments. The zoom ratio is higher than that of the fourth embodiment, and it covers a range from quasi-wide angle to telephoto with a simple configuration. Considering the focal length at the telephoto end, the aperture ratio is 1: 10.66, which means that the aperture is large. The function of the aspherical surface of the first surface of the first lens unit G1 of this embodiment is large. An aberration diagram is shown in FIG.

FIG. 5 is a cross-sectional view of the zoom lens according to the sixth embodiment. This embodiment has a focal length of 35.77-68.
5, a zoom lens having an F number of 2.88 to 4.52, and six lens configurations.

The first group G1 of the zoom lens includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second group G2 includes an aperture stop and an object side. The third group G3 includes a negative meniscus lens having a convex surface directed toward the image side and a positive meniscus lens having a convex surface directed toward the image side having a stronger curvature of the image side surface. It consists of a biconcave lens with a stronger curvature on the object side.

In this configuration, the rear surface of the first lens (negative meniscus lens) of the first group G1, the front surface of the first lens (negative meniscus lens) of the second group G2, the front surface of the second lens (positive meniscus lens), Aspheric surfaces are used on both surfaces of the first lens (positive meniscus lens) of the third group G3 and on the front surface of the second lens (biconcave lens).

The zoom ratio of this embodiment is smaller than that of the above embodiment, but the aperture ratio is increased. With this configuration, an aperture ratio comparable to a single-lens reflex camera can be realized. The configuration is the same as that of the first embodiment.
As shown in FIG. 2, although pincushion-type distortion occurs, high imaging performance can be expected. This also shows that the zoom ratio and the aperture ratio are in a trade-off relationship.

FIG. 6 is a cross-sectional view of the zoom lens according to the seventh embodiment. In this embodiment, the focal length ranges from 29.2 to 48.5.
The zoom lens has an F number of 3.4 to 4.85, and has six lenses.

The first group G1 of the zoom lens includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second group G2 has an aperture stop and an object side. The third group G3 includes a positive meniscus lens having a convex surface facing the image side, and a positive meniscus lens having a convex surface facing the image side where the curvature of the image side surface is stronger. It consists of a biconcave lens with a stronger curvature on the object side.

In this configuration, the rear surface of the first lens (negative meniscus lens) of the first group G1, the front surface of the second lens (positive meniscus lens) of the second group G2, and the first lens (positive meniscus lens) of the third group G3. An aspheric surface is used on the front surface of the lens (lens) and the front surface of the second lens (biconcave lens).

Although the zoom ratio of this embodiment is smaller than that of the above embodiment, the zoom angle is increased and the aperture ratio is increased. The lens configuration is the same as that of the sixth embodiment, but the number of aspherical surfaces used is reduced. As shown in FIG.
The astigmatism image plane difference appears.

In the following, numerical data of the above embodiments are shown. Symbols other than those described above, f is the overall system focal length, F _NO is the F number, ω is the half angle of view, f _B is the back focus, r ₁ ,
r ₂ ... curvature radius of each lens surface, d _1, d ₂ ... the spacing between the lens surfaces, n _d1, n _d2 ... d-line refractive index of each lens, ν _d1, ν _d2 ... Each lens Is the Abbe number of In addition,
The aspherical shape has x as an optical axis where the traveling direction of light is positive,
If y is taken in a direction perpendicular to the optical axis, it is expressed by the following equation. ^{x = (y 2 / r)} / [1+ {1- (K + 1) (y / r)
_{^{2} 1/2] + A 4 y}} 4 + A 6 y 6 + A 8 y 8 + A 10 y 10 where, r is the paraxial radius of curvature, K is a conical coefficient, A _4, A _6,
A ₈ and A ₁₀ are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.

[0055] Example 1 f = 38.90 ~ 63.00 ~102.50 F NO = 4.49 ~ 4.84 ~ 5.51 ω = 29.08 ° ~ 18.96 ° ~ 11.92 ° f B = 8.2513~ 24.2310~ 46.3388 r 1 = 517.77500 d 1 = 2.000000 n d1 = 1.69895 ν _d1 = 30.1 r ₂ = 40.62427 d ₂ = 0.120000 r ₃ = 21.35513 (aspherical surface) d ₃ = 3.600000 nd ₂ = 1.77250 ν _d2 = 49.6 r ₄ = 84.25217 d ₄ = (variable) r ₅ = ∞ (aperture) _{d 5 = 0.700000 r 6 = 16.62891} ( _{aspherical) d 6 = 3.708279 n d3 =} 1.84666 ν d3 = 23.8 r 7 = 13.14871 d 7 = 5.949181 r 8 = 108.03346 ( _{aspherical) d 8 = 4.831743 n d4 =} 1.49700 ν d4 = 81.6 r ₉ = -13.36230 (aspherical surface) d ₉ = (variable) r ₁₀ = -17.31597 (aspherical surface) d ₁₀ = 2.430000 n _d5 = 1.84666 ν _d5 = 23.8 r ₁₁ = -13.15695 d ₁₁ = 0.250000 r ₁₂ = -14.38951 _{(aspherical) d 12 = 1.650000 n d6 =} 1.77250 ν d6 = 49.6 r 13 = 188.86532 Aspheric surface third surface K = 0 A ₄ = -0.567940 × 10 ^-5 A ₆ = -0.173165 × 10 ^-7 A ₈ = 0.629539 × 10 ^-10 A ₁₀ = -0.326441 × 10 ^-12 Surface 6 K = 0 A ₄ = -0.206075 × 10 ^-4 A ₆ = -0.556584 × 10 ^-6 A ₈ = 0.109802 × 10 ^-7 A ₁₀ = -0.146408 × 10 ^-9 Surface 8 K = 0 A ₄ = -0.376837 × 10 ^-4 A ₆ = 0.238314 × 10 ^-6 A ₈ = -0.105290 × 10 ^-7 A ₁₀ = 0.825390 × 10 ^-10 Surface 9 K = 0 A ₄ = 0.120140 × 10 ^-5 A ₆ = 0.608314 × 10 ^-7 A ₈ = -0.641437 × ₁₀ ^-8 A 10 = 0 10th surface _{K = 0 A 4 = -0.474221 ×} 10 -4 A 6 = -0.121512 × 10 -5 A 8 = 0.914992 × 10 -8 A 10 = -0.425789 × 10 - ^10th twelfth surface K = 0 A ₄ = 0.652495 × 10 ^-4 A ₆ = 0.101071 × 10 ^-5 A ₈ = -0.712984 × 10 ^-8 A ₁₀ = 0.206774 × 10 ^-10 .

[0056] Example 2 f = 38.90 ~ 63.00 ~102.49 F NO = 4.50 ~ 4.85 ~ 5.70 ω = 29.07 ° ~ 18.95 ° ~ 11.92 ° f B = 8.1406~ 25.2729~ 52.2006 r 1 = 18.49857 ( aspherical) d ₁ = 3.000000 n _d1 = 1.60342 ν _d1 = 38.0 r ₂ = 62.51333 d ₂ = 0.120000 r ₃ = 44.69607 (aspheric surface) d ₃ = 1.850000 nd ₂ = 1.84666 ν _d2 = 23.8 r ₄ = 22.99295 d ₄ = (variable) r ₅ = ∞ _{(stop) d 5 = 0.700000 r 6 =} 17.10251 ( _{aspherical) d 6 = 3.000000 n d3 =} 1.74077 ν d3 = 27.8 r 7 = 12.27490 d 7 = 3.588289 r 8 = 120.61439 ( aspherical) d ₈ = 6.504213 n _{d4 = 1.49700 ν d4 = 81.6 r 9} = -11.29267 ( aspherical) d ₉ = (variable) r ₁₀ = -15.22807 _{(aspherical) d 10 = 2.430000 n d5 =} 1.84666 ν d5 = 23.8 r 11 = -12.95740 d 11 = 2.488967 r ₁₂ = -14.04508 (aspherical surface) d ₁₂ = 1.650000 nd ₆ = 1.74100 ν _d6 = 52.7 r ₁₃ = -1381.78078 Aspheric surface first surface K = 0 A ₄ = 0.525673 × 10 ^-5 A ₆ = -0.103955 × 10 ^-6 A ₈ = 0.513662 × 10 ^-9 A ₁₀ = -0.105214 × 10 ^-10 Third surface K = 0 A ₄ = -0.859375 × 10 ^-5 A ₆ = 0.119036 × 10 ^-6 A ₈ = -0.262707 × 10 ^-9 A ₁₀ = 0.615198 × 10 ^-11 Surface 6 K = 0 A ₄ = -0.584914 × 10 ^-4 A ₆ = -0.101336 × 10 ^-5 A ₈ = 0.121361 × 10 ^-7 A ₁₀ = -0.399212 × 10 ^-9 Surface 8 K = 0 A ₄ = -0.318414 × 10 ^-4 A ₆ = 0.151829 × 10 ^-6 A ₈ = -0.109722 × 10 ^-7 A ₁₀ = 0.259649 × 10 ^-9 Surface 9 K = 0 A ₄ = -0.903062 × 10 ^-7 A ₆ = -0.251294 × 10 ^-6 A ₈ = -0.620397 × 10 ^-8 A ₁₀ = 0 Surface 10 K = 0 A ₄ = 0.172263 × 10 ^-5 A ₆ = -0.879896 × 10 ^-6 A ₈ = 0.660168 × 10 ^-8 A ₁₀ = -0.422676 × 10 ^-10 Surface 12 K = 0 A ₄ = 0.157850 x 10 ^-4 A ₆ = 0.713553 x 10 ^-6 A ₈ = -0.349518 x 10 ^-8 A ₁₀ = 0.141283 x 10 ^-10 .

[0057] Example 3 f = 38.90 ~ 63.00 ~102.50 F NO = 4.49 ~ 4.84 ~ 5.51 ω = 29.10 ° ~ 18.95 ° ~ 11.92 ° f B = 8.1465~ 24.9036~ 50.4184 r 1 = 25.88441 ( aspherical) d ₁ = 3.000000 n _d1 = 1.72916 v _d1 = 54.7 r ₂ = -134.39800 d ₂ = 0.100000 r ₃ = -419.78353 d ₃ = 1.850000 n _d2 = 1.80100 v _d2 = 35.0 r ₄ = 36.93486 (aspherical) d ₄ = (variable) r ₅ = ∞ (aperture) d ₅ = 0.700000 r ₆ = 18.12806 (aspherical surface) d ₆ = 3.000000 n _d3 = 1.69895 ν _d3 = 30.1 r ₇ = 14.00163 d ₇ = 3.170891 r ₈ = -484.53231 (aspherical surface) d ₈ = _{5.686798 n d4 = 1.49700 ν d4 =} 81.6 r 9 = -11.73312 ( aspherical) d ₉ = (variable) r ₁₀ = -15.27798 _{(aspherical) d 10 = 2.430000 n d5 =} 1.84666 ν d5 = 23.8 r 11 = -13.01365 _{d 11 = 1.253472 r 12 = -14.15786} ( _{aspherical) d 12 = 1.650000 n d6 =} 1.72916 ν d6 = 54.7 r 13 = 769.28220 Aspheric surface first surface K = 0 A ₄ = -0.296373 × 10 ^-4 A ₆ = -0.165440 × 10 ^-6 A ₈ = 0.591936 × 10 ^-10 A ₁₀ = -0.638549 × 10 ^-12 Fourth surface K = 0 A ₄ = -0.409524 × 10 ^-4 A ₆ = -0.230156 × 10 ^-6 A ₈ = 0.595887 × 10 ^-9 A ₁₀ = -0.962000 × 10 ^-12 Surface 6 K = 0 A ₄ = -0.608955 × 10 ^-4 A ₆ = -0.101161 × 10 ^-5 A ₈ = 0.904478 × 10 ^-8 A ₁₀ = -0.270076 × 10 ^-9 Surface 8 K = 0 A ₄ = -0.278171 × 10 ^-4 A ₆ = 0.157960 × 10 ^-6 A ₈ = 0.519863 × 10 ^-8 A ₁₀ = 0.137430 × 10 ^-9 Surface 9 K = 0 A ₄ = 0.711250 × 10 ^-5 A ₆ = -0.350560 × 10 ^-6 A ₈ = -0.145531 × 10 ^-8 A ₁₀ = 0 10th surface K = 0 A ₄ = -0.142061 × 10 ^-4 A ₆ = -0.115449 × 10 ^-5 A ₈ = 0.996954 × 10 ^-8 A ₁₀ = -0.597049 × 10 ^-10 12th surface K = 0 A ₄ = 0.443017 x 10 ^-4 A ₆ = 0.887543 x 10 ^-6 A ₈ = -0.531 850 x 10 ^-8 A ₁₀ = 0.183791 x 10 ^-10 .

[0058] Example 4 f = 38.90 ~ 64.60 ~132.55 F NO = 4.45 ~ 5.45 ~ 8.02 ω = 29.09 ° ~ 18.51 ° ~ 9.28 ° f B = 8.1678~ 26.7938~ 72.9799 r 1 = 39.80842 ( aspherical) d ₁ = 3.000000 n _d1 = 1.60300 v _d1 = 65.5 r ₂ = -34.07202 d ₂ = 0.100000 r ₃ = -38.49500 d ₃ = 1.850000 n _d2 = 1.67790 v _d2 = 50.7 r ₄ = 99.86819 (aspheric) d ₄ = (variable) r ₅ = ∞ _{(stop) d 5 = 0.700000 r 6 =} 16.40761 ( _{aspherical) d 6 = 3.496314 n d3 =} 1.75520 ν d3 = 27.5 r 7 = 12.03637 d 7 = 4.073250 r 8 = 260.70426 ( aspherical) d ₈ = 5.462459 _{n d4 = 1.49700 ν d4 = 81.6} r 9 = -11.39110 ( aspherical) d ₉ = (variable) r ₁₀ = -15.88023 _{(aspherical) d 10 = 2.430000 n d5 =} 1.84666 ν d5 = 23.8 r 11 = -13.05299 d ₁₁ = 0.868923 r ₁₂ = -14.39908 (aspherical surface) d ₁₂ = 1.650000 nd ₆ = 1.71992 ν _d6 = 53.1 r ₁₃ = 187.56223 Aspheric surface first surface K = 0 A ₄ = -0.369384 × 10 ^-4 A ₆ = -0.201390 × 10 ^-6 A ₈ = 0.955882 × 10 ^-10 A ₁₀ = 0.651815 × 10 ^-13 Fourth surface K = 0 A ₄ = -0.438056 × 10 ^-4 A ₆ = -0.222638 × 10 ^-6 A ₈ = 0.793156 × 10 ^-9 A ₁₀ = -0.151285 × 10 ^-11 Surface 6 K = 0 A ₄ = -0.527052 × 10 ^-4 A ₆ = -0.890524 × 10 ^-6 A ₈ = 0.106263 × 10 ^-7 A ₁₀ = -0.268781 × 10 ^-9 Surface 8 K = 0 A ₄ = -0.330925 × 10 ^-4 A ₈ = -0.578278 × 10 ^-8 A ₁₀ = 0.184818 × 10 ^-9 Surface 9 K = 0 A ₄ = 0.114008 × 10 ^-5 A ₆ = -0.331717 × 10 ^-6 A ₈ = -0.392908 × 10 ^-8 A ₁₀ = 0 Surface 10 K = 0 A ₄ = 0.168018 × 10 ^-4 A ₆ = -0.127195 × 10 ^-5 A ₈ = 0.776293 × 10 ^-8 A ₁₀ = -0.421904 × 10 ^-10 Surface 12 K = 0 A ₄ = 0.278806 × 10 ^-5 A ₆ = 0.104468 × 10 ^-5 A ₈ = -0.418803 × 10 ^-8 A ₁₀ = 0.104664 × 10 ^-10 .

[0059] Example 5 f = 38.90 ~ 63.76 ~176.20 F NO = 4.45 ~ 5.38 ~ 10.66 ω = 29.11 ° ~ 18.73 ° ~ 7.01 ° f B = 8.1682~ 25.8711~101.8657 r 1 = 39.41755 ( aspherical) d ₁ = 3.000000 n _d1 = 1.60300 v _d1 = 65.5 r ₂ = -38.67280 d ₂ = 0.100000 r ₃ = -44.95027 d ₃ = 1.850000 n _d2 = 1.67790 v _d2 = 50.7 r ₄ = 86.39684 (aspheric) d ₄ = (variable) r ₅ = ∞ _{(stop) d 5 = 0.700000 r 6 =} 17.73835 ( _{aspherical) d 6 = 3.000000 n d3 =} 1.75520 ν d3 = 27.5 r 7 = 13.52957 d 7 = 3.914785 r 8 = 1027.11475 ( aspherical) d ₈ = 6.123340 _{n d4 = 1.49700 ν d4 = 81.6} r 9 = -11.45207 ( aspherical) d ₉ = (variable) r ₁₀ = -16.03689 _{(aspherical) d 10 = 2.430000 n d5 =} 1.84666 ν d5 = 23.8 r 11 = -13.24028 d ₁₁ = 0.986902 r ₁₂ = -14.57723 (aspherical surface) d ₁₂ = 1.650000 nd ₆ = 1.73211 ν _d6 = 53.5 r ₁₃ = 155.44298 Aspheric surface first surface K = 0 A ₄ = -0.369066 × 10 ^-4 A ₆ = -0.194068 × 10 ^-6 A ₈ = 0.103454 × 10 ^-9 A ₁₀ = 0.443898 × 10 ^-12 Fourth surface K = 0 A ₄ = -0.438368 × 10 ^-4 A ₆ = -0.225585 × 10 ^-6 A ₈ = 0.887736 × 10 ^-9 A ₁₀ = -0.150114 × 10 ^-11 Surface 6 K = 0 A ₄ = -0.551729 × 10 ^-4 A ₆ = -0.916230 × 10 ^-6 A ₈ = 0.108673 × 10 ^-7 A ₁₀ = -0.264949 × 10 ^-9 Surface 8 K = 0 A ₄ = -0.351889 × 10 ^-4 A ₆ = 0.380438 × 10 ^-6 A ₈ = -0.531284 × 10 ^-8 A ₁₀ = 0.137428 × 10 ^-9 Surface 9 K = 0 A ₄ = 0.107752 × 10 ^-4 A ₆ = -0.196017 × 10 ^-6 A ₈ = -0.245889 × 10 ^-8 A ₁₀ = 0 Surface 10 K = 0 A ₄ = 0.183609 × 10 ^-4 A ₆ = -0.127147 × 10 ^-5 A ₈ = 0.790811 × 10 ^-8 A ₁₀ = -0.429998 × 10 ^-10 Surface 12 K = 0 A ₄ = 0.279610 × 10 ^-5 A ₆ = 0.104503 × 10 ^-5 A ₈ = -0.419592 × 10 ^-8 A ₁₀ = 0.104060 × 10 ^-10 .

[0060] Example 6 f = 35.77 ~ 50.50 ~ 68.50 F NO = 2.88 ~ 3.66 ~ 4.52 ω = 31.16 ° ~ 23.19 ° ~ 17.52 ° f B = 8.0899~ 19.0526~ 32.1385 r 1 = 517.77500 d 1 = 2.000000 n d1 = 1.72151 ν _d1 = 29.2 r ₂ = 44.00391 (aspherical surface) d ₂ = 0.120000 r ₃ = 20.68156 d ₃ = 3.600000 nd ₂ = 1.77250 ν _d2 = 49.6 r ₄ = 79.99374 d ₄ = (variable) r ₅ = ∞ (aperture) _{d 5 = 0.700000 r 6 = 19.15290} ( _{aspherical) d 6 = 3.371112 n d3 =} 1.80518 ν d3 = 25.4 r 7 = 14.56995 d 7 = 2.600000 r 8 = -90.65254 ( _{aspherical) d 8 = 4.695293 n d4 =} 1.49700 ν _{d4 = 81.6 r 9 = -10.68862 d} 9 = ( variable) r ₁₀ = -15.21401 _{(aspherical) d 10 = 2.430000 n d5 =} 1.84666 ν d5 = 23.8 r 11 = -12.92559 ( aspherical) d ₁₁ = 2.850000 r ₁₂ = -13.99499 _{(aspherical) d 12 = 1.650000 n d6 =} 1.69350 ν d6 = 50.8 r 13 = 491.35330 Aspheric coefficient Second surface K = 0 A ₄ = 0.511096 × 10 ^-5 A ₆ = 0.118094 × 10 ^-8 A ₈ = 0.951352 × 10 ^-11 A ₁₀ = 0 Sixth surface K = 0 A ₄ = -0.761340 × 10 ^-4 A ₆ = -0.103714 × 10 ^-5 A ₈ = -0.218881 × 10 ^-8 A ₁₀ = -0.288 105 × 10 ^-9 Surface 8 K = 0 A ₄ = -0.306499 × 10 ^-4 A ₆ = 0.237361 × 10 ^{_{-5 A 8 = -0.380474 × 10 -7}} A 10 = 0.109291 × 10 -8 10th surface _{K = 0 A 4 = -0.302512 ×} 10 -4 A 6 = -0.218136 × 10 -6 A 8 = 0.297237 × 10 - ⁸ A ₁₀ = -0.495078 × 10 ^-10 Surface 11 K = 0 A ₄ = 0.117287 × 10 ^-4 A ₆ = 0.255880 × 10 ^-6 A ₈ = -0.158499 × 10 ^-8 A ₁₀ = 0.545484 × 10 ^-12 12 planes K = 0 A ₄ = 0.817768 x 10 ^-4 A ₆ = 0.522390 x 10 ^-6 A ₈ = -0.370928 x 10 ^-8 A ₁₀ = 0.171407 x 10 ^-10 .

[0061] Example 7 f = 29.20 ~ 38.40 ~ 48.50 F NO = 3.41 ~ 4.17 ~ 4.85 ω = 36.61 ° ~ 29.40 ° ~ 24.03 ° f B = 8.0873~ 15.6133~ 23.6724 r 1 = 425.50000 d 1 = 2.000000 n d1 = 1.68034 ν _d1 = 31.7 r ₂ = 23.83577 (aspherical surface) d ₂ = 0.120000 r ₃ = 15.14929 d ₃ = 3.600000 nd ₂ = 1.77250 ν _d2 = 49.6 r ₄ = 47.73625 d ₄ = (variable) r ₅ = ∞ (aperture) _{d 5 = 0.700000 r 6 = 14.77875} d 6 = 3.000000 n d3 = 1.56255 ν d3 = 68.9 r 7 = 24.45556 d 7 = 2.600000 r 8 = -14.04628 ( _{aspherical) d 8 = 4.518938 n d4 =} 1.49700 ν d4 = 81.6 r ₉ = -7.51664 d ₉ = (variable) r ₁₀ = -40.46094 _{(aspherical) d 10 = 2.430000 n d5 =} 1.84666 ν d5 = 23.8 r 11 = -21.53449 d 11 = 2.082081 r 12 = -12.69028 ( aspherical) d ₁₂ = 1.650000 n _d6 = 1.81117 ν _d6 = 34.0 r ₁₃ = 177.00069 Aspheric coefficient Second surface K = 0 A ₄ = 0.173022 × 10 ^-4 A ₆ = 0.641879 × 10 ^-7 A ₈ = 0.753061 × 10 ^-10 A ₁₀ = 0 Eighth surface K = 0 A ₄ = -0.601026 × 10 ^-3 A ₆ = -0.374216 × 10 ^-5 A ₈ = -0.231852 × 10 ^-6 A ₁₀ = -0.139288 × 10 ^-8 Surface 10 K = 0 A ₄ = -0.319537 × 10 ^-5 A ₆ = -0.791614 × _{^{10 -7 A 8 = 0.771038 × 10}} -10 A 10 = -0.198293 × 10 -10 12th surface _{K = 0 A 4 = 0.111901 ×} 10 -3 A 6 = 0.547549 × 10 -6 A 8 = -0.299544 × 10 - ⁸ A ₁₀ = 0.313857 x 10 ^-10 .

Next, the conditional expressions (1) of the above-mentioned Examples 1 to 7,
The value of (2) is shown.

The above-mentioned compact zoom lens of the present invention can be constituted, for example, as follows. [1] In order from the object side, the first lens unit includes a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. With the wide-angle end as a reference, each group moves to the object side, the first group is composed of a negative meniscus lens having a convex surface facing the object side and a positive lens, and the second group has a convex surface facing the object side. The third group includes a meniscus first lens and a positive second lens having a surface with a strong curvature on the image side. The third group includes a positive meniscus lens having a convex surface facing the image side and a strong curvature on the object side. And a negative lens having at least one aspheric surface in each lens group and satisfying the following conditions. 0.1 <φ ₁ / φ _W <0.6 (1) 1.3 <m _3T / m _3W <4 (2) where φ ₁ is the combined refraction of the first lens unit at the wide-angle end. Power, φ _W is the refractive power of the entire system at the wide-angle end, m _3W is the lateral magnification of the third lens unit at the wide-angle end, and m _3T is the lateral magnification of the third lens unit at the telephoto end.

[2] In order from the object side, the first positive refractive power
Group, a second group of positive refracting power, and a third group of negative refracting power. When zooming from the wide-angle end to the telephoto end, each group moves to the object side. The second unit includes an aperture stop, a meniscus-shaped first lens having a convex surface facing the object side, and a positive lens having a strong curvature facing the image side. The third group is composed of a positive meniscus lens having a convex surface facing the image side and a negative lens having a strong curvature surface on the object side. Each lens group has at least one lens. It has an aspheric surface,
A compact zoom lens characterized by satisfying the following conditions. 0.1 <φ ₁ / φ _W <0.6 (1) 1.3 <m _3T / m _3W <4 (2) where φ ₁ is the combined refraction of the first lens unit at the wide-angle end. Power, φ _W is the refractive power of the entire system at the wide-angle end, m _3W is the lateral magnification of the third lens unit at the wide-angle end, and m _3T is the lateral magnification of the third lens unit at the telephoto end.

[3] The compact zoom lens as described in [1] or [2], wherein the first lens of the second group is constituted by a negative meniscus lens.

[4] The compact zoom lens according to any one of [1] to [3], wherein an aspheric surface is used on the object side surface of the first lens of the second group.

[5] At the time of zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group is increased, and the distance between the second group and the third group is reduced. The compact zoom lens according to any one of [1] to [4], wherein the group moves.

[6] The compact zoom lens according to any one of [1] to [5], wherein the second lens of the second group satisfies the following condition. ν _d > 60 (3) where ν _d is the Abbe number of the medium of the second lens of the second group.

[7] Each of the above-mentioned groups is composed of only two lenses, and the total lens length at the wide-angle end is reduced by making the lens configuration six lenses in three groups. The compact zoom lens according to any one of [1] to [6].

[0070]

As is apparent from the above description, according to the present invention, the first group of positive refractive power, the second group of positive refractive power, and the third group of negative refractive power are arranged in order from the object side. When zooming from the wide-angle end to the telephoto end, each group moves to the object side,
It is a configuration that satisfies the above conditions (1) and (2), and it is possible to greatly reduce the size and obtain high performance by effectively using the lens configuration and the aspherical surface with a small number of lenses. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a zoom lens according to a first embodiment of the present invention, including an optical axis at a wide-angle end, an intermediate focal length, and a telephoto end.

FIG. 2 is a lens sectional view similar to FIG. 1 of Embodiment 2 of the zoom lens of the present invention.

FIG. 3 is a lens sectional view similar to FIG. 1 of Embodiment 3 of the zoom lens of the present invention.

FIG. 4 is a sectional view similar to FIG. 1 of a zoom lens according to a fourth embodiment of the present invention;

FIG. 5 is a sectional view similar to FIG. 1 of a zoom lens according to a sixth embodiment of the present invention.

FIG. 6 is a lens sectional view similar to FIG. 1 of a zoom lens according to a seventh embodiment of the present invention.

FIG. 7 is an aberration diagram of the first embodiment.

FIG. 8 is an aberration diagram of the second embodiment.

FIG. 9 is an aberration diagram of the third embodiment.

FIG. 10 is an aberration diagram of the fourth embodiment.

FIG. 11 is an aberration diagram of the fifth embodiment.

FIG. 12 is an aberration diagram of the sixth embodiment.

FIG. 13 is an aberration diagram of the seventh embodiment.

[Explanation of symbols]

 G1: first lens group G2: second lens group G3: third lens group

Claims (3)

[Claims] 1. A first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power are arranged in order from the object side when zooming from the wide-angle end to the telephoto end. On the basis of the wide-angle end, each group moves toward the object side, and the first group includes a negative meniscus lens having a convex surface facing the object side and a positive lens,
The second group has a first meniscus shape with the convex surface facing the object side.
The third group includes a lens, a positive meniscus lens having a convex surface facing the image side, and a negative lens having a strong curvature surface on the object side. Wherein each lens group has at least one aspheric surface and satisfies the following conditions. 0.1 <φ ₁ / φ _W <0.6 (1) 1.3 <m _3T / m _3W <4 (2) where φ ₁ is the combined refraction of the first lens unit at the wide-angle end. Power, φ _W is the refractive power of the entire system at the wide-angle end, m _3W is the lateral magnification of the third lens unit at the wide-angle end, and m _3T is the lateral magnification of the third lens unit at the telephoto end. 2. A zoom lens system comprising, in order from the object side, a first unit having a positive refractive power, a second unit having a positive refractive power, and a third unit having a negative refractive power. Each group moves to the object side, the first group is composed of a positive lens and a negative lens having a convex surface facing the object side, and the second group is a meniscus shape having an aperture stop and a convex surface facing the object side. And a second lens of a positive lens having a convex surface with a strong curvature directed to the image side,
The third group includes a positive meniscus lens having a convex surface facing the image side and a negative lens having a strong curvature surface on the object side. Each lens group has at least one aspheric surface. A compact zoom lens that satisfies the conditions. 0.1 <φ ₁ / φ _W <0.6 (1) 1.3 <m _3T / m _3W <4 (2) where φ ₁ is the combined refraction of the first lens unit at the wide-angle end. Power, φ _W is the refractive power of the entire system at the wide-angle end, m _3W is the lateral magnification of the third lens unit at the wide-angle end, and m _3T is the lateral magnification of the third lens unit at the telephoto end. 3. The compact zoom lens according to claim 1, wherein the first lens of the second group is constituted by a negative meniscus lens.