JPH05346542A - Small-sized two-group zoom lens - Google Patents

Abstract

PURPOSE:To obtain the zoom lens which has a wide field angle and a high variable power ratio while its compactness and high performance are maintained by providing a negative lens element with at least one aspherical surface. CONSTITUTION:This lens consists of a front group which has negative refracting power and a rear group which has positive refracting power and varies in power with the distance between both the groups; and the rear group consists of a positive lens element, a negative lens element, and a negative lens element in order from the object side and the negative lens element has at least one aspherical surface. The rear group which has large power between the front group which has the negative refracting power and the rear group which has the positive refracting power consists of three elements which are a positive lens element, a negative lens element, and a negative lens element. In this case, the positive lens element on the most object side among the elements converges diverged luminous flux made incident on the rear group to compensate the spherical aberration, and the two negative lens elements excellently compensate the chromatic aberration and off-axis aberration together with the one aspherical surface that each negative lens element has.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens including two lens groups, a front lens group having a negative refractive power and a rear lens group having a positive refractive power, and more particularly to a zoom lens having a reduced number of lens components. .

[0002]

2. Description of the Related Art Conventionally, the zoom lens of the type described above has been widely used as a so-called standard zoom lens including a standard angle of view, as an interchangeable lens for a single-lens reflex camera. This type of lens system constitutes a retrofocus paraxial arrangement in which two lens groups, a front group having negative refracting power and a rear group having positive refracting power, are arranged apart from each other. It is easy to secure a long back focus, which is necessary to mount the quick return mirror of the reflex camera, and it is easy to obtain good performance in addition to being compact as a whole.

In such a negative / positive two-unit zoom type, as a conventional example in which the number of constituent elements is reduced, there is Japanese Patent Laid-Open No.
No. 9-64811 can be mentioned. This lens system is a zoom lens with a focal length of approximately 35 to 70 mm, but the front group consists of 2 groups of 2 groups and the rear group consists of 4 groups of 4 groups. We are making corrections.

Further, as an example in which the number of sheets is reduced, Japanese Patent Application Laid-Open No.
-46308 is available. This lens system is about 35
In a zoom lens with a focal length of around 70 mm, the front lens group consists of 2 lens groups in 2 groups, and the rear lens group consists of 2 lens groups in 2 group or 3 lens groups in 3 group. We are making corrections.

On the other hand, as an example of applying this type of lens system to a lens shutter camera, Japanese Patent Laid-Open No. 62-507.
No. 18 is given. With a lens shutter camera, it is not necessary to lengthen the back focus, so the overall length can be shortened by that amount, but the rear group configuration is arranged so that the positive refracting power and the negative refracting power are separated, so-called telephoto paraxial. By arranging them, the overall length is further shortened. The lens system of this conventional example has a focal length of about 35 to 70 mm, the front lens group is composed of 3 lenses in 3 groups, the rear lens group is composed of 6 lenses in 4 groups, and the front and rear lens groups are made aspheric by aberration. We are making corrections.

[0006]

Problems to be Solved by the Invention JP-A-59-648
The lens system of No. 11 is composed of 6 lenses even in the whole system, and the number of lenses is small, but the effective diameter of the front lens group is large due to the setting of the refractive power distribution to each lens group, which leads to a compact size. It is not preferable in terms. Further, since the two lenses included in the front group have large effective diameters, both material cost and processing cost thereof are high, which is not preferable. In particular, when the focal length at the wide-angle end is shortened to achieve a wider angle, the drawback becomes remarkable.

Further, the lens system of Japanese Patent Laid-Open No. 4-46308 has a structure of 4 to 5 lenses in total, but
The aberration correction situation is not practical.

The lens system disclosed in JP-A-62-50718 is
Although the overall length and effective diameter have been reduced, the total system is 9
As many lenses as used are used, which is not preferable in terms of cost. The present invention mainly aims to reduce the number of constituent elements in a two-group zoom lens including a front group having a negative refractive power and a rear group having a positive refractive power, while maintaining sufficient compactness and high performance. The objective is to provide a zoom lens with a wide angle of view and a high zoom ratio.

[0009]

A zoom lens according to the present invention comprises a front group having a negative refracting power and a rear group having a positive refracting power, and zooms by changing an interval between the two groups. so,
The rear group is a lens system that is composed of a positive lens component, a negative lens component, and a negative lens component in order from the object side, and that has at least one aspherical surface in the negative lens component.

The present invention aims to reduce the number of lens constituents as much as possible, but simply reducing the number of lenses only causes deterioration of aberrations, and also impairs the degree of freedom in aberration correction. Therefore, how to reduce the number of sheets while maintaining high performance becomes a problem.

According to the present invention, of the front group having a negative refracting power and the rear group having a positive refracting power, a rear group having a stronger power is divided into a positive lens component, a negative lens component and a negative lens component. Composed of two ingredients. Of these lens components, the positive lens component closest to the object side converges the divergent light flux incident on the rear group to enable correction of spherical aberration, and the two negative lens components are at least one of these negative lens components. Together with the aspherical surface included in one surface, chromatic aberration and off-axis aberration, particularly astigmatism and distortion, are well corrected.

On the other hand, no matter how much the number of constituent lenses is reduced to achieve the cost reduction, the lens system becomes huge and has no commercial value. Therefore, in order to achieve sufficient compactness and high performance with the above-described small number of lens configurations, it is preferable to first give appropriate refractive power distribution to the front and rear groups. Therefore, it is desirable that the lens system of the present invention having the above-described structure satisfy the following conditions (1) and (2). (1) 1 <| f ₁ | / f _W <2 (2) 0.7 <f ₂ / f _W <1.4 where f ₁ and f ₂ are focal lengths of the front and rear groups, respectively.
f _W is the focal length of the entire system at the wide-angle end.

As is well known, the negative / positive two-group zoom type has an intermediate focal length f _S [f _S = (f _W
f _T ) ^1/2 where f _W and f _T are the focal lengths of the entire system at the wide-angle end and the telephoto end, respectively. ], The amount of movement of the front group due to zooming is minimized when the rear group is imaged at the same magnification. In the present invention, the condition (1) is satisfied in consideration of reducing the movement amount of the front group and the possibility of aberration correction.
The rear-unit same-magnification imaging position is arranged between the vicinity of the intermediate focal length and the wide-angle end. Therefore, if the upper limit of condition (1) is exceeded, the amount of movement of the front group naturally increases, and
Since the distance between the front and rear groups increases, the effective diameter of the front group increases, which is not preferable. If the lower limit of the condition (1) is exceeded, sufficient aberration correction cannot be performed with a small number of lens components.

The condition (2) was set based on the amount of movement of the rear lens group that is associated with zooming and the possibility of aberration correction. The stronger the refracting power of the rear group is, the smaller the movement amount can be. However, if the refracting power of the rear group becomes strong beyond the lower limit of the condition (2), the lens structure of the present invention cannot correct aberrations sufficiently. On the other hand, when the upper limit of the condition (2) is exceeded and the refractive power of the rear group becomes weak, the amount of movement becomes large and the effective distance of the front group becomes large because the distance between the front and rear groups widens, which is not preferable.

Further, in order to achieve good aberration correction,
It is important to make the negative lens component in the rear group aspherical. At this time, it is desirable that at least one aspherical surface satisfies the following conditional expression (3). (3) 0 <Δ _RN / φ _RN where φ _RN is the paraxial radius of curvature of the aspherical surface provided in the negative lens component of the rear group, r _R3 , and the refractive index of the medium before and after the aspherical surface is n. _{When R3} and n _R3 'are given, the following equation is expressed, and Δ _RN is an aspherical amount at the effective radius. φ _R3 = (n _R3 '−n _R3 ) / r _R3 Condition (3) means that the shape of the aspherical surface is such that the negative refracting power gradually increases with distance from the optical axis. If the condition (3) is not satisfied, the correction of astigmatism and distortion at the wide-angle end becomes insufficient.

In the zoom lens of the present invention, the focal length of the positive lens component closest to the object in the rear group is f _R1.
Then, it is preferable to satisfy the following condition (4). (4) 0.5 <f _R1 / f ₂ <1.5 In the lens system of the present invention, the light beam emitted from the front group becomes a divergent light beam with negative power and enters the rear group. This divergent light beam is converged on the image plane by the positive power of the rear group, but all the converging action is borne by the positive lens component in the rear group. Therefore, when the upper limit of the condition (4) is exceeded, the power of the negative lens component becomes zero. Therefore, the upper limit of the condition (4) is not exceeded. On the other hand, when the value goes below the lower limit of the condition (4), the power of the positive lens component in the rear lens group becomes too strong, and sufficient aberration correction cannot be performed.

Furthermore, it is desirable that the Abbe number of the positive lens component in the rear lens group satisfies the following condition (5). (5) 70 <ν _R1 where ν _R1 is the Abbe's number of the positive lens component in the rear group, and when this positive lens component is a cemented lens, etc. It is the sum of Abbe numbers.

As will be described later in Examples, the power of the negative lens component does not necessarily have to be strong. Therefore, even if the power of the negative lens component is not strong, it is necessary to reduce the chromatic aberration generated in the positive lens component in the rear group in order to suppress the variation of the chromatic aberration due to zooming. Therefore, it is desirable to satisfy the above condition (5).

On the other hand, in the lens system of the present invention, it is desirable that the front group is composed of a negative lens component and a positive lens component in order from the object side, and has at least one aspherical surface. At this time, the aspherical surface preferably satisfies the following condition (6). (6) 0 <Δ _F / φ _{F where} φ _F is given by φ _F = (n _F '−n _F ) / r _F ,
In this equation, r _F is the paraxial radius of curvature of the aspherical surface provided in the front group, and n _F and n _F 'are the refractive indices of the media before and after the aspherical surface,
Δ _F is the amount of aspherical surface at the effective radius.

The condition (6) means that, like the condition (3), the shape of the aspherical surface is such that the negative refracting power gradually increases as the distance from the optical axis increases.

When the total thickness of the positive lens component in the rear group is d _R1 , it is desirable to satisfy the following condition (7). (7) 0.1 <d _R1 / f ₂ <0.5 Further, in order to make the entire length of the lens system compact, it is desirable to satisfy the following condition (8). (8) 0.2 <f _BW / IH <1, where f _BW is the back focus at the wide-angle end, and IH is the diagonal length of the screen. When the back focus becomes longer than the upper limit of the condition (8), the distance from the first surface to the image surface becomes long, and the camera thickness tends to become thick accordingly, which is not preferable. If the back focus becomes shorter than the lower limit of the condition (8), it is advantageous to shorten the total length, but the diameter of the lens on the image plane side in the rear group becomes large, which is not preferable in terms of size reduction and cost.

[0022]

[Embodiments] Next, each of the small-sized two-group zoom lenses of the present invention will be described.
An example is shown. Example 1 f = 28 to 44.3 to 70 mm, F / 4.6 to F / 5.78 to F / 7.64 f_B = 34.3 to 47.0 to 67.1 mm, 2ω = 75.30 ° to 51.99 ° to 34.30 ° r₁ = 67.7540 d₁ = 1.8000 n₁ = 1.79952 ν₁ = 42.24 r₂ = 14.1700 (aspherical surface) d₂ = 6.0000 r₃ = 20.7220 d₃ = 4.0000 n₂ = 1.84666 ν₂ = 23.78 r_Four = 32.6080 d_Four = D r_Five = ∞ (aperture) d_Five = 1.0000 r₆ = 14.8240 (aspherical surface) d₆ = 5.4700 n₃ = 1.58913 ν₃ = 61.18 r₇ = -21.3360 d₇ = 1.5000 n_Four = 1.74077 ν_Four = 27.79 r₈ = -110.5550 d₈ = 7.2300 r₉ = -51.8190 d₉ = 1.8000 n_Five = 1.69680 ν_Five = 55.52 r_Ten= -239.2890 d_Ten= 2.5600 r₁₁= -34.0540 (aspherical surface) d₁₁= 1.8000 n₆ = 1.49241 ν₆ = 57.66 r₁₂= -40.2100 (aspherical surface) aspherical surface coefficient (r₂ Surface) P = 0.6360, A_Four = 0.22340 x 10^-Five, A₆ = 0.15985 x 10^-7 A₈ = -0.89313 x 10^-Ten , A_Ten= 0 (r₆ Surface) P = 1.0000, A_Four = -0.25333 x 10^-Five, A₆ = 0.28475 x 10^-7 A₈ = -0.11140 x 10^-8, A_Ten= 0.14457 x 10^-Ten (R₁₁Surface) P = 0.9989, A_Four = -0.34820 x 10^-3 , A₆ = -0.25868 × 10^-Five A₈ = 0.51062 x 10^-8 , A_Ten= 0 (r₁₂Surface) P = 1.0000, A_Four = -0.21561 x 10^-3 , A₆ = -0.13920 x 10^-Five A₈ = 0.18243 x 10^-7 , A_Ten= 0 f 28 44.3 70 D 29.574 13.056 2.638 ｜ f₁ ｜ / f_W = 1.43, f₂ / F_W = 1.12 Δ_RN/ Φ_RN= 58.034 (Y = 6.570) r₁₁Surface, -56.242 (Y = 7.337) r₁₂Face f_R1/ F₂ = 0.82, ν_R1= 88.97, Δ_F / Φ_F = 15.802 (Y = 12.334) r₂ Surface d _R1 / F₂ = 0.22, f_BW/IH=0.80 Example 2 f = 28 to 44.3 to 70 mm, F / 4.6 to F / 5.78 to F / 7.65 f_B = 28.0 to 39.4 to 57.3 mm, 2ω = 75.30 ° to 51.99 ° to 34.30 ° r₁ = 102.0380 d₁ = 1.8000 n₁ = 1.80610 ν₁ = 40.95 r₂ = 15.4510 (aspherical surface) d₂ = 5.5100 r₃ = 22.9950 d₃ = 4.1000 n₂ = 1.80518 ν₂ = 25.43 r_Four = 45.5240 d_Four = D r_Five = ∞ (aperture) d_Five = 1.0000 r₆ = 12.5750 (aspherical surface) d₆ = 5.5000 n₃ = 1.58313 ν₃ = 59.36 r₇ = -23.9680 d₇ = 1.5000 n_Four = 1.74077 ν_Four = 27.79 r₈ = ∞ d₈ = 7.5700 r₉ = -56.8360 (aspherical surface) d₉ = 1.8000 n_Five = 1.72916 ν_Five = 54.68 r_Ten= 635.4610 d_Ten= 4.5600 r₁₁= -41.4020 d₁₁= 1.8000 n₆ = 1.69680 ν₆ = 55.52 r₁₂= -56.3110 (aspherical surface) aspherical surface coefficient (r₂ Surface) P = 0.6289, A_Four = 0.27458 x 10^-6, A₆ = 0.89015 x 10^-8 A₈ = -0.71846 x 10^-Ten , A_Ten= 0 (r₆ Surface) P = 1.0000, A_Four = -0.44084 x 10^-Five, A₆ = -0.43704 x 10^-7 A₈ = 0.75813 x 10^-9, A_Ten= 0 (r₉ Surface) P = 0.9982, A_Four = -0.15417 x 10^-3 , A₆ = -0.86017 x 10^-6 A₈ = -0.21284 x 10^-7 , A_Ten= 0 (r₁₂Surface) P = 1.0000, A_Four = -0.18827 x 10^-Four , A₆ = -0.13806 x 10^-6 A₈ = 0.21554 x 10^-9 , A_Ten= 0 f 28 44.3 70 D 32.290 14.188 2.771 ｜ f₁ ｜ / f_W = 1.59, f₂ / F_W = 1.11 Δ_RN/ Φ_RN= 18.353 (Y = 5.805) r₉Surface, -11.181 (Y = 8.420) r₁₂Face f_R1/ F₂ = 0.79, ν_R1 = 87.15, Δ_F / Φ_F = 16.876 (Y = 13.090) r₂Face d_R1/ f₂ = 0.23, f_BW/IH=0.65 Example 3 f = 35 to 49.5 to 70 mm, F / 4.6 to F / 5.42 to F / 6.58 f_B = 36.5 to 45.6 to 58.4 mm, 2ω = 63.36 ° to 47.15 ° to 34.30 ° r₁ = 240.6810 d₁ = 1.8000 n₁ = 1.80610 ν₁ = 40.95 r₂ = 21.5360 (aspherical surface) d₂ = 6.9200 r₃ = 31.2160 d₃ = 3.9200 n₂ = 1.80518 ν₂ = 25.43 r_Four = 65.5500 d_Four = D r_Five = ∞ (aperture) d_Five = 1.0000 r₆ = 15.0920 (aspherical surface) d₆ = 6.0700 n₃ = 1.58313 ν₃ = 59.36 r₇ = -24.3260 d₇ = 1.5000 n_Four = 1.74077 ν_Four = 27.79 r₈ = -168.6280 d₈ = 5.6800 r₉ = -53.2690 d₉ = 1.8000 n_Five = 1.72916 ν_Five = 54.68 r_Ten= -120.3020 d_Ten= 4.5600 r₁₁= -113.6740 (aspherical surface) d₁₁= 1.8000 n₆ = 1.49241 ν₆ = 57.66 r₁₂= 88.9710 (aspherical surface) aspherical surface coefficient (r₂ Surface) P = 0.7823, A_Four = -0.12430 x 10^-Five, A₆ = 0.20857 x 10^-8 A₈ = -0.19934 x 10^-Ten , A_Ten= 0 (r₆ Surface) P = 1.0000, A_Four = -0.22122 x 10^-Five, A₆ = -0.74253 x 10^-8 A₈ = 0.24774 x 10^-9, A_Ten= 0 (r₁₁Surface) P = 1.0000, A_Four = -0.37379 x 10^-3 , A₆ = -0.33626 x 10^-6 (R₁₂Surface) P = 1.0000, A_Four = -0.26163 x 10^-3 , A₆ = 0.57877 x10^-6 A₈ = 0.35854 x 10^-8 , A_Ten= 0 f 35 49.5 70 D 32.119 14.747 2.466 ｜ f₁ ｜ / f_W = 1.64, f₂ / F_W = 1.03 Δ_RN/ Φ_RN= 179.199 (Y = 6.646) r₁₁Surface, 116.475 (Y = 7.359) r₁₂Face f_R1/ F₂ = 0.76, ν_R1 = 87.15, Δ_F / Φ_F = 3.591 (Y = 12.613) r₂ Face d _R1 / f₂ = 0.21, f_BW/IH=0.85 Example 4 f = 28 to 44.3 to 70 mm, F / 4.6 to F / 5.79 to F / 7.68 f_B = 40.0 to 53.5 to 74.8 mm, 2ω = 75.30 ° to 51.99 ° to 34.30 ° r₁ = 64.9860 (aspherical surface) d₁ = 1.8000 n₁ = 1.78590 ν₁ = 44.18 r₂ = 13.6870 (aspherical surface) d₂ = 6.6000 r₃ = 21.6840 d₃ = 4.1000 n₂ = 1.80518 ν₂ = 25.43 r_Four = 35.7490 d_Four = D r_Five = ∞ (aperture) d_Five = 1.0000 r₆ = 13.2490 (aspherical surface) d₆ = 9.4600 n₃ = 1.49700 ν₃ = 81.61 r₇ = -81.0620 d₇ = 1.0800 r₈ = -60.2680 d₈ = 1.8000 n_Four = 1.75520 ν_Four = 27.51 r₉ = 87.0610 d₉ = 2.9900 n_Five = 1.64000 ν_Five = 60.09 r_Ten= -63.0520 d_Ten= 1.9400 r₁₁= -33.4450 (aspherical surface) d₁₁= 1.8000 n₆ = 1.69350 ν₆ = 50.81 r₁₂= -94.4320 Aspheric coefficient (r₁ Surface) P = 1.0000, A_Four = -0.60799 x 10^-Five, A₆ = 0.95516 x 10^-8 A₈ = -0.39330 x 10^-11 , A_Ten= 0 (r₂ Surface) P = 0.6280, A_Four = -0.86532 x 10^-Five, A₆ = -0.87852 x 10^-8 A₈ = 0.14244 x 10^-9, A_Ten= 0 A₈ = 0.86781 x 10^-9 , A_Ten= -0.52146 x 10^-11 (R₁₁Surface) P = 0.8618, A_Four = -0.885415 x 10^-Four , A₆ = -0.42285 x 10^-6 A₈ = -0.72431 x 10^-8 , A_Ten= 0 f 28 44.3 70 D 29.964 13.528 3.163 ｜ f₁ ｜ / f_W = 1.39, f₂ / F_W = 1.15 Δ_RN/ Φ_RN= 7.128 (Y = 6.052) r₁₁Face f_R1/ F₂ = 0.74, ν_R1 = 81.61 Δ_F / Φ_F = -19.342 (Y = 15.551) r₁ Surface, 26.995 (Y = 12.363) r₂ Face d_R1/ f₂ = 0.29, f_BW/ IH = 0.93 where r₁ , R_Two , Is the radius of curvature of each lens surface, d₁ , D_Two , ... is the thickness of each lens and the lens interval, n₁ , N_Two , ... is the refractive index of each lens, ν₁ , Ν_Two , ... is the Abbe number of each lens.

The above-described first to fourth embodiments have the configurations shown in FIGS. 1 to 4, respectively. The front group in each of these examples has a two-group, two-lens configuration including, in order from the object side, a negative lens and a positive lens, and has one or two aspherical surfaces.
The rear group consists of a positive lens component, a negative lens component, and a negative lens component. Among them, the positive lens component has two types, that is, a single lens and a cemented lens. The first negative lens component also has two types, that is, a single lens and a cemented lens. The second negative lens component is a single lens. Therefore, the rear group is composed of four lenses in three groups and has two or three aspherical surfaces. In the case of a cemented lens, even if the cemented positive lens and the cemented negative lens are disposed slightly apart from each other, there is no problem in configuring the present invention.

Further, the embodiment uses glass material and plastic material. In particular, if plastic is used for a lens having a weak power as in the first embodiment, the plastic material can be used without being strongly affected by temperature and humidity changes.

The shape of the aspherical surface used in the above embodiments is represented by the following equation when the Z axis is taken in the traveling direction of light on the optical axis and the Y axis is taken in the direction orthogonal to the optical axis.

Where r is a paraxial radius of curvature, P, A ₄ ,
A ₆ , A ₈ and A ₁₀ are aspherical coefficients. The value of Y shown in the data of the examples, the aspherical amount delta _R3, delta _F
Indicates the effective radius when calculating.

[0027]

The zoom lens of the present invention is a negative / positive two-unit zoom type, compact and high-performance lens system with a small number of lenses.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a sectional view of a second embodiment.

FIG. 3 is a sectional view of a third embodiment.

FIG. 4 is a sectional view of a fourth embodiment.

FIG. 5 is an aberration curve diagram at the wide-angle end in Example 1.

FIG. 6 is an aberration curve diagram at the intermediate focal length of Example 1.

7 is an aberration curve diagram of Example 1 at a telephoto end. FIG.

FIG. 8 is an aberration curve diagram of Example 2 at the wide-angle end.

FIG. 9 is an aberration curve diagram at the intermediate focal length of Example 2.

FIG. 10 is an aberration curve diagram for Example 2 at the telephoto end.

FIG. 11 is an aberration curve diagram of Example 3 at the wide-angle end.

FIG. 12 is an aberration curve diagram for Example 3 at the intermediate focal length.

FIG. 13 is an aberration curve diagram for Example 3 at the telephoto end.

FIG. 14 is an aberration curve diagram of Example 4 at the wide-angle end.

FIG. 15 is an aberration curve diagram for Example 4 at the intermediate focal length.

FIG. 16 is an aberration curve diagram for Example 4 at the telephoto end.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 3

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

Further, in order to achieve good aberration correction,
It is important to make the negative lens component in the rear group aspherical. At this time, it is desirable that at least one aspherical surface satisfies the following conditional expression (3). (3) 0 <Δ _RN / φ _RN where φ _RN is the paraxial radius of curvature of the aspherical surface provided in the negative lens component of the rear group, r _RN , and the refractive index of the medium before and after the aspherical surface is n. _{When RN} and n _RN ′, the following formula is expressed, and Δ _RN is an aspherical surface amount at the effective radius. φ _RN = (n _RN ′ −n _RN ) / r _RN Condition (3) means that the aspherical surface has an aspherical surface shape that gradually increases the negative refracting power as the distance from the optical axis increases. If the condition (3) is not satisfied, the correction of astigmatism and distortion at the wide-angle end becomes insufficient.

Claims (3)

[Claims] 1. A zoom lens comprising a front group having a negative refracting power and a rear group having a positive refracting power, in which zooming is performed by changing an interval between the two groups, the rear group being arranged in order from an object side. A zoom lens that includes a positive lens component, a negative lens component, and a negative lens component, and has at least one aspherical surface in the negative lens component. 2. A zoom lens according to claim 1, wherein the following conditions (1) and (2) are satisfied. (1) 1 <| f ₁ | / f _W <2 (2) 0.7 <f ₂ / f _W <1.4 where f ₁ and f ₂ are the focal lengths of the front and rear groups, respectively, f _W Is the focal length of the entire system at the wide-angle end. 3. The zoom lens according to claim 1, wherein at least one aspherical surface provided in the negative lens component of the rear group satisfies the following condition (3). (3) 0 <Δ _R3 / φ _R3 φ _R3 = (n _R3 '−n _R3 ) / r _{R3 where} r _R3 is the paraxial radius of curvature of the aspherical surface provided in the negative lens component in the rear group, n _R3 , n _R3 'is the refractive index of the medium before and after the aspherical surface, and Δ _R3 is the aspherical surface amount at the effective radius.