JP2003307676A - High variable power zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a zoom lens whose variable power ratio is a high class such as about 3, and further whose aberration is excellently corrected in spite of adopting such a simple constitution as a two-group zoom lens system. <P>SOLUTION: In the zoom lens equipped with a 1st lens group G1 having positive power and a 2nd lens group G2 having negative power, the focal distance of an entire system is changed by changing space between the lens groups, and the 2nd lens group G2 has a negative lens, a positive lens and a negative lens in order from an object side. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-magnification zoom lens, and more particularly to a high-magnification zoom lens suitable as a taking lens for a compact camera with a limited back focus.

[0002]

2. Description of the Related Art Conventionally, as a simplest zoom lens system, a so-called two-group zoom lens system having two groups is known. This method has advantages such as a simple lens frame structure, but has a drawback that the zoom ratio cannot be increased so much because the aberration variation is large.

By the way, in recent years, there has been a strong demand for a high zoom ratio of a zoom lens, and as one aiming for a high zoom ratio by using this two-group zoom lens system, there is one such as Japanese Patent Laid-Open No. 2004-242242. Among these, the variable power ratio has reached about 2.8.

[0004]

[Patent Document 1] JP-A-4-218013

[0005]

However, if an attempt is made to achieve a further high zoom ratio using the configuration of the above-mentioned prior art example, both monochromatic aberration and chromatic aberration will break down, which is a practical level in terms of imaging performance. I can't achieve things.

The present invention has been made in view of such problems of the prior art, and its object is to achieve a high zoom ratio of 3 times class while adopting a simple structure of a two-group zoom lens system. Therefore, it is to provide a zoom lens in which the aberration is corrected more favorably.

[0007]

A high zoom lens system according to the present invention which achieves the above object comprises a first lens unit having a positive power and a second lens unit having a negative power in order from the object side. In the zoom lens in which the focal length of the entire system is changed by changing the distance between these lens groups, the second lens group has, in order from the object side, a negative lens, a positive lens, and a negative lens. It is characterized by.

Another high variable power zoom lens of the present invention comprises, in order from the object side, a first lens group having a positive power and a second lens group having a negative power, and the intervals between these lens groups are set. In the zoom lens in which the focal length of the entire system is changed by changing it, the first lens group includes, in order from the object side, a first lens having negative power and a meniscus-shaped negative power having a convex surface facing the object side. And a lens group having a positive power, and the second lens group has, in order from the object side, a negative lens, a positive lens, and a negative lens. Is.

[0009]

The reason why the above-mentioned structure is adopted in the present invention and its operation will be described below.

First, regarding the configuration in the first lens group, in order to achieve a high zoom ratio, it is necessary to reduce the amount of chromatic aberration generated in each group, so at least one It is necessary to have a negative lens component and a positive lens component.

Further, in the two-group zoom lens of positive group + negative group, there is a drawback that the back focus becomes short especially when aiming at widening of the angle.

For this reason, the problem of mechanical interference is apt to occur, which is not preferable. However, as in the constitution of the present invention, the constitution in which the negative lens is arranged on the object side makes it possible to obtain a comparatively long back light. It becomes possible to secure the focus.

Next, the reason why it is preferable to employ a negative lens and a negative meniscus lens convex on the object side in order from the object side will be described.

The first lens group is composed of a negative lens group + a positive lens group. Here, since the first lens group as a whole is a positive lens group, the power of the positive lens group becomes relatively strong within the group. Therefore, the amount of under spherical aberration and the like generated here increases. Further, as in the zoom lens of the present invention, when a high zoom ratio of 3 × class is set, there is a problem in that the amount of astigmatism generated increases, particularly in the intermediate zoom state, and the image peripheral portion is affected. The image performance was significantly reduced. Such a problem becomes more remarkable when the power of the group is increased and the total length is shortened.

Therefore, in order to cancel various aberrations generated in this positive lens group, first, regarding spherical aberration and coma, in particular, by providing a negative negative meniscus lens on the object side, much spherical aberration and the like are caused. The amount of aberration generated can be reduced as a whole by the effect of the generation and cancellation.

Regarding the correction of astigmatism and distortion, it is preferable to provide a lens that satisfies the following conditional expression (1).

(1) -5 <SF _L1 <0 Here, SF _L1 is the shaping factor of the first lens in the first lens group, and the radius of curvature of the object side surface and the image side surface of the first lens is r ₁ , When r ₂ , SF _L1 = (r ₁
This is a parameter given by + r ₂ ) / (r ₁ −r ₂ ).

That is, the expression (1) defines the shape of the negative first lens. According to this expression (1), the first surface of the first lens is relatively larger than the second surface. It has a curvature. Therefore, by defining the value in the range of this equation, it is possible to increase the amount of astigmatism or distortion and to cancel the amount generated in the positive group. Further, since the principal plane position of this lens is closer to the object side, the shift of the principal plane position to the image side due to the meniscus-shaped negative lens is canceled to widen the angle of view or
There is also an effect of reducing the axial thickness in the lens group. If the upper limit value 0 or the lower limit value -5 of the above formula (1) is exceeded, the action of canceling the above-mentioned astigmatism and distortion is not achieved, and the wide angle of view or the axis in the first lens group is not achieved. It becomes difficult to reduce the upper thickness.

Regarding the order of arrangement of the above-mentioned two negative lenses, a lens which produces a lot of aberrations such as astigmatism and distortion is arranged at a place where off-axis rays are high, that is, near the image plane side. By adopting a configuration in which a lens with a large amount of spherical aberration and coma generated has a relatively high axial ray, that is, a configuration in which it is arranged closer to the object side, the configuration of the first lens group is the most effective for aberration correction. Efficient placement.

With the above arrangement, it is possible to obtain a zoom lens system having a high zoom ratio and various aberrations favorably corrected. With regard to the expression (1), by setting the range of (1) ′ − 2 <SF _L1 <−0.1, the balance of the amount of astigmatism and distortion generated is optimized, and high image quality is achieved without difficulty. It is preferable because an image is obtained.

In the zoom lens of the present invention,
By defining the shape of the negative meniscus convex to the object side of the second lens in the first lens group by the following equation (2),
More desirable.

(2) 1 <SF _L2 <10 Here, SF _L2 is the shaping factor of the second lens in the first lens group, and the radius of curvature of the object side surface and the image side surface of the second lens is r ₃ , r _{If 4} , then SF _L2 = (r ₃
+ R ₄₎ is a parameter given by / (r ₃ -r _4).

That is, if the upper limit of 10 in the equation (2) is exceeded, the radius of curvature becomes too small to maintain the same power, and the amount of high-order aberrations increases, which is not preferable. On the other hand, if the lower limit of 1 is exceeded, the meniscus shape as defined above will not be obtained, and the effect on aberration correction will not appear, which is not preferable.

In the zoom lens of the present invention,
By defining the range of the radius of curvature of the first surface of the first lens as in the following expression (3), a more desirable configuration is obtained from the viewpoint of aberration correction.

(3) -2 <f _W / r ₁ <-0.6 where f _W is the focal length at the wide-angle end of the entire system and r ₁ is the first
It is the radius of curvature of the first surface of the lens.

That is, when the upper limit of -0.6 of the equation (3) is exceeded, the incident angle with respect to the off-axis ray is too small to obtain a desired aberration correction ability, but conversely, the lower limit of -2 is used.
When the value exceeds 1.0, the curvature of the first surface becomes too small, and the amount of aberration generated on this surface becomes too large. Especially, the amount of astigmatism and field curvature aberration increases, which is not preferable.

Further, with respect to (3), in particular, (3) '- 1.6 <by paying a range of f _W / r ₁ <-0.8, the generation amount of the aberration of the first surface is It is more desirable because it becomes the optimum range and the number of lenses and the number of aspherical surfaces can be suppressed.

Further, in the zoom lens of the present invention, it is more desirable to set the ratio of the focal lengths of the first lens and the second lens of the first lens group as follows.

(4) 0.2 <f _L1 / f _L2 <1 where f _L1 is the focal length of the first lens of the first lens group,
f _L2 is the focal length of the second lens of the first lens group.

That is, by defining the conditional expression (4) within the range, the power of the first lens having negative power is made stronger than the power of the negative meniscus lens. This is preferable because it leads to a shift to, and thus a back focus is secured.

Also regarding the equation (4), the balance of the power ratio is optimum if it is set within the range of (4) '0.2 <f _L1 / f _L2 <0.6.

Further, in the zoom lens of the present invention, by using an aspherical surface on any surface in the first lens group, it is possible to reduce the total generation amount of various aberrations in the entire system. Therefore, it is effective for size reduction by deleting the number of sheets and increasing the power.

Further, the zoom lens of the present invention can provide a simple zoom lens having a high zoom ratio even if the following configuration is adopted.

That is, in order from the object side, it is composed of a first lens group having a positive power and a second lens group having a negative power, and the second lens group comprises, in order from the object side, a negative lens and a positive lens. , And the negative lens is a zoom lens arranged in this order.

This is mainly about the configuration of the second lens group, but in the two-group zoom lens, it is particularly the second lens group.
Since only the lens group has a zooming effect, it is important to reduce the amount of chromatic aberration generated in this group in order to reduce the fluctuation of axial chromatic aberration. Therefore, regarding the lens arrangement, first, it is necessary to provide at least one negative lens group and a positive lens group, and a configuration in which a negative lens group having a relatively strong power is arranged on the image side is the main plane position in the image plane. It is preferable that it is located on the side because it can secure the back focus.

From the viewpoint of correcting lateral chromatic aberration, it is preferable to use a glass material having a large Abbe number for the negative lens. However, in the above-mentioned method of using a glass material, the variation of the axial chromatic aberration becomes large when the zoom ratio is increased.

Therefore, for this correction, by providing a negative lens at a position where the axial ray is high, that is, on the object side of the positive lens, it is possible to reduce variations in both chromatic aberrations of magnification and on axis, which is desirable. .

Further, when the above-mentioned structure is adopted, if the following conditional expression (5) is satisfied, the amount of axial chromatic aberration generated can be reduced as achromaticity of the negative lens group, which is desirable.

(5) ν ₁ > ν ₂ where ν ₁ is the Abbe number of the first lens of negative power in the second lens group, and ν ₂ is the Abbe number of the second lens of positive power in the second lens group. is there.

As described above, the above-mentioned effects can be achieved by using three negative, positive, and negative lenses. However, from the viewpoint of manufacturing, using any combination of these lenses as a cemented lens has the effect of decentering. Is desirable because it can be made smaller.

Further, by satisfying the following conditional expression (6), a higher performance zoom lens can be obtained, which will be explained.

(6) -3 <f ₂₂ / f ₂₁ <0 where f ₂₁ is the focal length of the first lens of the second lens group having negative power, and f ₂₂ is the second focal length of the second lens group of positive power. The focal length of the lens.

Equation (6) defines the ratio of the refracting powers of the negative lens and the positive lens on the object side of the second lens group.
This is because by setting it in the range of the expression (6), the amount of chromatic aberration generated can be reduced in the range where a general glass material is used. Here, if the lower limit of -3 of the conditional expression (6) is exceeded, the power of the second lens becomes relatively strong, and the achromatizing effect of the positive lens becomes insufficient, and conversely, the upper limit of When it exceeds 0, the effect of providing the negative lens on the object side is lost, and it becomes difficult to reduce the fluctuation of the axial chromatic aberration in particular.

As described above, it has been explained that a zoom lens with a high zoom ratio can be obtained by adopting the above-mentioned structure. Furthermore, with respect to this second lens group, either Providing an aspherical surface
This is desirable because it has the same effect as the aspherical surface in the first lens group described above.

The shape of these aspherical surfaces is expressed by the following equation, where x is an optical axis with the traveling direction of light being positive and y is a direction perpendicular to the optical axis.

X = (y ² / r) / [1+ {1-P (y / r) ² } ^1/2 ] + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰ ... ( a) where r is the paraxial radius of curvature, P is the conic coefficient, A ₄ , A ₆ ,
A ₈ and A ₁₀ are aspherical coefficients of the 4th, 6th, 8th and 10th orders, respectively.

In the zoom lens of the present invention,
The first lens group includes, in order from the object side, a first lens having a negative power, a second lens having a meniscus negative power with a convex surface facing the object side, and a lens having a positive power following the first lens. And a second lens group,
By adopting a configuration in which a negative lens, a positive lens, and a negative lens are arranged in this order from the object side, the effects as described above can be obtained, which is sufficient to achieve a high zoom ratio. .

[0048]

EXAMPLES Next, Examples 1 to 3 of the zoom lens of the present invention will be described.
Will be described.

FIGS. 1 to 3 are sectional views showing the arrangement of lens groups at the wide-angle end, the intermediate focal length, and the telephoto end of Embodiments 1 to 3 for comparison. The numerical data of each example will be described later, but the configuration of each example will be described below.

The configuration of the first lens group G1 is the same as that of the first to third embodiments.
The first lens L _{1 is} a biconcave lens, the second lens L ₂ is a negative meniscus lens having a convex surface directed toward the object side, and the subsequent biconvex lens is the negative meniscus lens having a convex surface directed toward the object side and the biconvex lens. Positive lens group L consisting of cemented lenses
_It consists of _P. The stop is arranged so as to move integrally with the first lens group G1 closest to the image plane side.

In the first embodiment, the construction of the second lens group G2 includes, in order from the object side, a negative meniscus lens having a convex surface facing the image surface side, a biconvex lens, and a negative meniscus lens having a convex surface facing the image surface side. In the case of Example 2, it is composed of a cemented lens of a biconcave lens and a biconvex lens in order from the object side, and a negative meniscus lens having a convex surface facing the image side, and in the case of Example 3, a biconcave lens, an image side. It is composed of a positive meniscus lens having a convex surface facing toward and a negative meniscus lens having a convex surface facing toward the image side.

The aspherical surface is the surface on the object side of the second lens L ₂ of the first lens group G1 and the second lens group G in Examples 1 to 3.
It is used for two of the two object-side surfaces.

Numerical data of each of the above-mentioned embodiments will be shown below. Symbols are other than the above, f is the focal length of the entire system, F _NO is the F number, ω is the half angle of view, f _B is the back focus, and r ₁ , R
₂ ... is the radius of curvature of each lens surface, d ₁ , d ₂ ... Is the distance between the lens surfaces, n _d1 , n _d2 ... Is the d-line refractive index of each lens,
ν _d1 , ν _d2 ... Are Abbe numbers of each lens. The aspherical shape is represented by the above equation (a).

Example 1 f = 32.8 to 57.3 to 104.9 F _NO = 4.7 to 6.6 to 9.3 ω = 33.4 ° to 20.7 ° to 11.6 ° f _B = 4.9 to 33.1 to 87.8 r ₁ = -34.0405 d ₁ = 1.300 n _d1 = 1.48749 ν _d1 = 70.21 r ₂ = 45.5988 d ₂ = 0.380 r ₃ = 24.7296 (aspherical surface) d ₃ = 1.760 n _d2 = 1.51823 ν _d2 = 58.98 r ₄ = 14.5247 d ₄ = 4.830 r ₅ = 36.1164 d ₅ = 3.700 n _d3 = 1.59270 ν _d3 = 35.30 r ₆ = -28.8962 d ₆ = 0.380 r ₇ = 111.4152 d ₇ = 1.080 n _d4 = 1.76182 ν _d4 = 26.52 r ₈ = 18.6680 d ₈ = 8.090 n _d5 = 1.48749 ν _d5 = 70.21 r ₉ = -15.6221 d ₉ = 1.000 r ₁₀ = ∞ (aperture) d ₁₀ = (variable) r ₁₁ = -76.1412 (aspherical surface) d ₁₁ = 1.700 n _d6 = 1.60311 ν _d6 = 60.68 r ₁₂ = -529.1814 d ₁₂ = 0.800 r ₁₃ = 8265.8776 d ₁₃ = 3.400 n _d7 = 1.60342 ν _d7 = 38.02 r ₁₄ = -33.5011 d ₁₄ = 4.530 r ₁₅ = -13.7032 d ₁₅ = 1.880 n _d8 = 1.77250 ν _d8 = 49.60 r ₁₆ = -66.1061 Aspheric coefficient 3rd surface P = 1.4179 A ₄ = -0.80383 × 10 ^-4 A ₆ = -0.43771 × 10 ^-6 A ₈ = 0.21893 × 10 ^-8 A ₁₀ = -0.13754 × 10 ^-10 11th surface P = 1.0000 A ₄ = 0.28913 × 10 ^-4 A ₆ = 0.80503 × 10 ^-7 A ₈ = 0.34547 × 10 ^-9 A ₁₀ = 0.13239 × 10 ^-11 (1) SF _L1 = -0.15 (2) SF _L2 = 3.85 (3) f _W / r ₁ = -0.96 (4) f _L1 / f _L2 = 0.55 (6) f ₂₂ / f ₂₁ = -0.37.

Example 2 f = 35.2 to 56.9 to 105.6 F _NO = 4.6 to 6.6 to 9.7 ω = 31.5 ° to 20.8 ° to 11.6 ° f _B = 6.0 to 30.0 to 83.7 r ₁ = -32.5553 d ₁ = 1.250 n _d1 = 1.48749 ν _d1 = 70.21 r ₂ = 54.9496 d ₂ = 0.380 r ₃ = 22.1057 (aspherical surface) d ₃ = 1.740 n _d2 = 1.51823 ν _d2 = 58.98 r ₄ = 15.6175 d ₄ = 3.940 r ₅ = 35.1000 d ₅ = 2.590 n _d3 = 1.59270 ν _d3 = 35.30 r ₆ = -35.3450 d ₆ = 0.380 r ₇ = 93.3222 d ₇ = 1.070 n _d4 = 1.76182 ν _d4 = 26.52 r ₈ = 17.9674 d ₈ = 8.000 n _d5 = 1.48749 ν _d5 = 70.21 r ₉ = -15.0689 d ₉ = 1.000 r ₁₀ = ∞ (aperture) d ₁₀ = (variable) r ₁₁ = -42.2935 (aspherical surface) d ₁₁ = 1.250 n _d6 = 1.48749 ν _d6 = 70.21 r ₁₂ = 97.9308 d ₁₂ = 4.000 n _d7 = 1.57501 ν _d7 = 41.49 r ₁₃ = -30.5666 d ₁₃ = 4.700 r ₁₄ = -11.7741 d ₁₄ = 1.880 n _d8 = 1.77250 ν _d8 = 49.60 r ₁₅ = -33.5326 Aspherical coefficient 3rd surface P = 1.5239 A ₄ = -0.82698 × 10 ^-4 A ₆ = -0.48832 × 10 ^-6 A ₈ = 0.13526 × 10 ^-8 A ₁₀ = -0.12961 × 10 ^-10 11th surface P = 1.0000 A ₄ = 0.58364 × 10 ^-4 A ₆ = 0.18349 × 10 ^-6 A ₈ = 0.16159 × 10 ^-8 A ₁₀ = 0.21409 × 10 ^-11 (1) SF _L1 = -0.26 (2) SF _L2 = 5.81 (3) _{f W / r 1 = -0.92 (} 4) f L1 / f L2 = 0.37 (6) f 22 / f 21 = -0.81.

Example 3 f = 35.2 to 57.1 to 112.6 F _NO = 4.6 to 6.6 to 9.2 ω = 31.5 ° to 20.7 ° to 10.9 ° f _B = 5.6 to 31.5 to 97.3 r ₁ = -85.2875 d ₁ = 1.300 n _d1 = 1.48749 ν _d1 = 70.21 r ₂ = 29.3007 d ₂ = 0.400 r ₃ = 23.0828 (aspherical surface) d ₃ = 3.220 n _d2 = 1.51823 ν _d2 = 58.98 r ₄ = 14.5343 d ₄ = 4.950 r ₅ = 52.9605 d ₅ = 3.700 n _d3 = 1.59270 ν _d3 = 35.30 r ₆ = -28.0124 d ₆ = 0.380 r ₇ = 517.4441 d ₇ = 1.080 n _d4 = 1.76182 ν _d4 = 26.52 r ₈ = 24.6431 d ₈ = 8.090 n _d5 = 1.48749 ν _d5 = 70.21 r ₉ = -15.0647 d ₉ = 1.000 r ₁₀ = ∞ (aperture) d ₁₀ = (variable) r ₁₁ = -150.8830 (aspherical surface) d ₁₁ = 1.700 n _d6 = 1.60311 ν _d6 = 60.68 r ₁₂ = 1396.8392 d ₁₂ = 0.800 _{r 13 = -350.1608 d 13 = 3.400} n d7 = 1.60342 ν d7 = 38.02 r 14 = -36.1047 d 14 = 4.530 r 15 = -14.4031 d 15 = 1.880 n d8 = 1.77250 ν d8 = 49.60 r 16 = -60.0956 Aspheric coefficient 3rd surface P = 1.3899 A ₄ = -0.82663 × 10 ^-4 A ₆ = -0.43672 × 10 ^-6 A ₈ = 0.50830 × 10 ^-9 A ₁₀ = -0.64099 × 10 ^-11 11th surface P = 1.0000 A ₄ = 0.25070 × 10 ^-4 A ₆ = 0.94881 × 10 ^-7 A ₈ = 0.65637 × 10 ^-10 A ₁₀ = 0.11165 × 10 ^-11 (1) SF _L1 = 0.49 (2) SF _L2 = 4.4 (3) f _{W / r 1 = -0.41 (4} ) f L1 / f L2 = 0.51 (6) f 22 / f 21 = -0.29.

Next, FIG. 4 to FIG. 4 show aberration diagrams at the wide-angle end, the intermediate focal length, and the telephoto end, respectively, when focusing on infinity in the first embodiment.
FIG. 6 shows similar aberration diagrams of Example 2 in FIGS. 7 to 9, and similar aberration diagrams of Example 3 in FIGS. In each aberration diagram, (a) is spherical aberration, (b) is astigmatism,
(C) shows distortion and (d) shows lateral chromatic aberration.

The above-described high variable power zoom lens of the present invention can be constructed, for example, as follows. [1] A zoom that includes, in order from the object side, a first lens group having a positive power and a second lens group having a negative power, and changing the distance between these lens groups to change the focal length of the entire system. In the lens, the first lens group includes
In order from the object side, a first lens having negative power and a second lens having a meniscus-shaped negative power with a convex surface facing the object side.
A high variable power zoom lens having a lens and a lens group having a positive power. [2] A zoom which includes, in order from the object side, a first lens group having a positive power and a second lens group having a negative power, and changing the interval between these lens groups to change the focal length of the entire system. In the lens, the second lens group is
A high-zoom zoom lens comprising a negative lens, a positive lens, and a negative lens in order from the object side. [3] A zoom that includes, in order from the object side, a first lens group having a positive power and a second lens group having a negative power, and changing the distance between these lens groups to change the focal length of the entire system. In the lens, the first lens group includes
In order from the object side, a first lens having negative power and a second lens having a meniscus-shaped negative power with a convex surface facing the object side.
A high zoom lens having a lens and a lens group having a positive power, and the second lens group has a negative lens, a positive lens, and a negative lens in order from the object side. . [4] The high-zoom zoom lens according to the above [1] or [3], wherein the first lens satisfies the following conditions.

(1) -5 <SF _L1 <0 where SF _L1 is the shaping factor of the first lens in the first lens group, and the radius of curvature of the object side surface and the image side surface of the first lens is r ₁ , When r ₂ , SF _L1 = (r ₁
This is a parameter given by + r ₂ ) / (r ₁ −r ₂ ). [5] In the above [1] or [3], the high-zoom zoom lens, wherein the second lens satisfies the following conditions.

(2) 1 <SF _L2 <10 Here, SF _L2 is the shaping factor of the second lens in the first lens group, and the radius of curvature of the object side surface and the image side surface of the second lens is r ₃ , r _{If 4} , then SF _L2 = (r ₃
+ R ₄₎ is a parameter given by / (r ₃ -r _4). [6] A high-zoom zoom lens that satisfies the following conditions in [1] or [3] above.

(3) −2 <f _W / r ₁ <−0.6 where f _W is the focal length at the wide-angle end of the entire system, and r ₁ is the first
It is the radius of curvature of the first surface of the lens. [7] A high-magnification zoom lens characterized by satisfying the following conditions in [1], [3] or [6].

(4) 0.2 <f _L1 / f _L2 <1 where f _L1 is the focal length of the first lens of the first lens group,
f _L2 is the focal length of the second lens of the first lens group. [8] A high-zoom zoom lens that satisfies the following conditions in [2] or [3].

(5) ν ₁ > ν ₂ where ν ₁ is the Abbe number of the first lens of negative power in the second lens group, and ν ₂ is the Abbe number of the second lens of positive power in the second lens group. is there.

[9] A high-magnification zoom lens which satisfies the following condition in [2], [3] or [8].

(6) -3 <f ₂₂ / f ₂₁ <0 where f ₂₁ is the focal length of the first lens of the second lens group having negative power, and f ₂₂ is the second focal length of the second lens group of positive power. The focal length of the lens. [10] The high-zoom zoom lens according to the above [1], wherein the positive lens group in the first lens group includes a positive lens and a cemented positive lens. [11] The high-zoom zoom lens according to the above [2] or [3], wherein the object-side negative lens and the positive lens in the second lens group are cemented together. [12] A high-zoom zoom lens according to the above [1], [2] or [3], including at least one aspherical surface. [13] In the above [1] or [3], the distance between the first lens and the second lens is narrower than the distance between the second lens and the lens group having positive power following the second lens. A high-zoom zoom lens that can

[0065]

As is apparent from the above description, according to the present invention, while adopting the simple structure of the two-group zoom lens system, the zoom ratio is high in the 3 × class, and the aberration is further favorably corrected. It is possible to obtain a zoom lens with high zoom ratio.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view showing, in contrast, lens arrangements at a wide-angle end, an intermediate focal length, and a telephoto end of a high-magnification zoom lens of Embodiment 1 of the present invention.

FIG. 2 is a lens cross-sectional view similar to FIG. 1 of a high variable power zoom lens of Embodiment 2.

FIG. 3 is a lens cross-sectional view similar to FIG. 1 of a high magnification zoom lens of Embodiment 3.

FIG. 4 is an aberration diagram for Example 1 at the wide-angle end when focused on infinity.

FIG. 5 is an aberration diagram of Example 1 at an intermediate focal length when focused on an object at infinity.

FIG. 6 is an aberration diagram for Example 1 at the telephoto end when focused on infinity.

FIG. 7 is an aberration diagram for Example 2 at the wide-angle end when focused on infinity.

FIG. 8 is an aberration diagram for Example 2 at the intermediate focal length when focused on infinity.

FIG. 9 is an aberration diagram of Example 2 at the telephoto end when focused on infinity.

FIG. 10 is an aberration diagram of Example 3 at the wide-angle end when focused on infinity.

FIG. 11 is an aberration diagram for Example 3 at the intermediate focal length when focused on infinity.

FIG. 12 is an aberration diagram for Example 3 at the telephoto end when focused on infinity.

[Explanation of symbols]

G1 ... positive lens group of the first lens group G2 ... second lens L _P ... first lens group of the first lens L ₂ ... the first lens group in the second lens group L ₁ ... the first lens group

Claims (15)

[Claims] 1. A first lens group having a positive power and a second lens group having a negative power are provided in this order from the object side, and the focal length of the entire system is changed by changing the distance between these lens groups. In the zoom lens, the second lens group has a negative lens, a positive lens, and a negative lens in order from the object side. 2. A first lens group having a positive power and a second lens group having a negative power are provided in this order from the object side, and the focal length of the entire system is changed by changing the distance between these lens groups. In the zoom lens, the first lens group includes, in order from the object side, a first lens having a negative power, a second lens having a meniscus negative power with a convex surface facing the object side, and a positive power. A high-zoom zoom lens, wherein the second lens group has a negative lens, a positive lens, and a negative lens in order from the object side. 3. The high zoom lens according to claim 2, wherein the first lens satisfies the following condition. (1) -5 <SF _L1 <0 Here, SF _L1 is the shaping factor of the first lens in the first lens group, and the radius of curvature of the object side surface and the image side surface of the first lens is r ₁ , r ₂ . When SF _L1 = (r ₁
This is a parameter given by + r ₂ ) / (r ₁ −r ₂ ). 4. The zoom lens according to claim 2, wherein the second lens satisfies the following condition. (2) 1 <SF _L2 <10 Here, SF _L2 is the shaping factor of the second lens in the first lens group, and the curvature radii of the object side surface and the image side surface of the second lens are r ₃ and r ₄ . When SF _L2 = (r ₃
+ R ₄₎ is a parameter given by / (r ₃ -r _4). 5. The high zoom lens according to claim 2, wherein the following condition is satisfied. (3) −2 <f _W / r ₁ <−0.6 where f _W is the focal length at the wide-angle end of the entire system, and r ₁ is the first
It is the radius of curvature of the first surface of the lens. 6. A high variable power zoom lens according to claim 2, wherein the following conditions are satisfied. (4) 0.2 <f _L1 / f _L2 <1 where f _L1 is the focal length of the first lens of the first lens group,
f _L2 is the focal length of the second lens of the first lens group. 7. A high variable power zoom lens according to claim 1, wherein the following condition is satisfied. (5) ν ₁ > ν ₂ where ν ₁ is the Abbe number of the first lens of negative power in the second lens group, and ν ₂ is the Abbe number of the second lens of positive power in the second lens group. 8. A high variable power zoom lens according to claim 1, 2 or 7, wherein the following condition is satisfied. (6) −3 <f ₂₂ / f ₂₁ <0 where f ₂₁ is the focal length of the first lens of negative power in the second lens group, and f ₂₂ is the focus of the second lens of positive power in the second lens group It is a distance. 9. The zoom lens according to claim 3, wherein the positive lens group in the first lens group comprises a positive lens and a cemented positive lens. 10. The high variable power zoom lens according to claim 1, wherein a negative lens and a positive lens on the object side in the second lens group are cemented together. 11. The high variable power zoom lens according to claim 1, comprising at least one aspherical surface. 12. The high variation according to claim 2, wherein a distance between the first lens and the second lens is narrower than a distance between the second lens and a lens unit having a positive power following the second lens. Double zoom lens. 13. The zoom lens according to claim 2, wherein the first lens satisfies the following condition. (1) ′ − 2 <SF _L1 <−0.1 where SF _L1 is the shaping factor of the first lens in the first lens group, and the radius of curvature of the object side surface and the image side surface of the first lens is r ₁ , R ₂ , SF _L1 = (r ₁
This is a parameter given by + r ₂ ) / (r ₁ −r ₂ ). 14. A high variable power zoom lens according to claim 2, wherein the following condition is satisfied. (3) ′ − 1.6 <f _W / r ₁ <−0.8 where f _W is the focal length at the wide-angle end of the entire system, and r ₁ is the first
It is the radius of curvature of the first surface of the lens. 15. A high-zoom zoom lens according to claim 2, wherein the following condition is satisfied. (4) '0.2 <f _L1 / f _L2 <0.6 where f _L1 is the focal length of the first lens of the first lens group,
f _L2 is the focal length of the second lens of the first lens group.