JPH0763993A - Telescopic zoom lens - Google Patents

Abstract

PURPOSE:To miniaturize the total length on the wide angle end by making a lens group a simple constitution having positive, negative and positive refractive powers, satisfying specified conditions and moving a first lens group to the object side at the time of varying the power from the wide-angle end to the telescopic end. CONSTITUTION:In order from the object side, this lens comprises a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power and a third lens group G3 having a positive refractive power. At the time of varying the power from the wide-angle end to the telescopic end, at least the first lens group G1 and the third lens group G3 are moved in the direction to the object, the air gap between the first lens group G1 and the second lens group G2 is increased and the air gap between the second lens group G2 and the third lens group G3 is decreased. By representing the focal distances of the respective lens groups G1, G2, G3 by f1, f2, f3 and the focal distance of the whole system at the wide-angle end by fw, the conditions: 1.25<=f1/fw<=1.50 -0.37<=f2/fw<=-0.30, 0.37<=f3/fw<=0.46 are satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephoto zoom lens suitable for a single-lens reflex camera, and particularly, the focal length at the wide-angle end is 1.4 to 2 times the diagonal length of the effective screen.
The present invention relates to a compact telephoto zoom lens having a zoom ratio exceeding 2.5 times.

[0002]

2. Description of the Related Art Conventionally, as this type of zoom lens,
(1) Positive, negative, positive, positive 4 groups afocal zoom lens, (2) Positive, negative, positive, negative double telephoto type 4 groups zoom lens, (3) Positive, negative, positive 3 groups Zoom lenses and the like have been proposed. The four-group afocal zoom lens of (1) is a zoom type in which the functional division of each lens group is clear and which is suitable for high performance.

The double telephoto type (2) is a zoom type suitable for downsizing of the entire length because the four groups are used as negative lens groups to provide a magnifying power. The three-group zoom lens of (3) is a zoom type that has a small number of lens groups and is suitable for downsizing and cost reduction.

[0004]

However, the four-group afocal zoom lens of the above (1) has a constant total length from the wide-angle end to the telephoto end, and it is difficult to shorten the total length. For this reason, it tends to be large and heavy, which makes it unsuitable for carrying. On the other hand, in the double telephoto type (2), the total length at the wide-angle end can be made smaller than that at the telephoto end, and portability can be improved. However, since four lens groups are required, the lens barrel structure is complicated and cost reduction is insufficient. In addition, (3)
The positive / negative / positive three-group zoom has a small number of lens groups of three and is suitable for cost reduction, and the overall length at the wide-angle end can be shortened, which is also advantageous for portability. As such a zoom lens, for example, JP-A-63-118116 is proposed.

The present invention employs the positive / negative / positive three-group zoom type (3), which is advantageous for downsizing and cost reduction, and is more effective than the embodiment disclosed in JP-A-63-118116. The purpose is to reduce the size.

[0006]

According to the present invention, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power are arranged in this order from the object side. A lens group, and at the time of zooming from the wide-angle end to the telephoto end, at least the first lens group and the third lens group move in the object direction, and the air gap between the first lens group and the second lens group increases. However, the air distance between the second lens group and the third lens group is a telephoto zoom lens, the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the third lens group is Is f3 and the focal length of the entire system at the wide-angle end is fW, 1.25≤f1 / fW≤1.50 (1) -0.37≤f2 / fW≤-0.30 (2 ) 0.37≤f3 / fw≤0.46 (3) The conditions are satisfied.

The third lens group comprises, in order from the object side, a 3a lens group having a positive refractive power and a 3b lens group having a negative refractive power, and the focal length of the 3b lens group is f3b, where D is the air gap between the 3a-th lens group and the 3b-th lens group, -5≤f3b / f3≤-3 (4) 0.3≤D / fw ≤0.6 (5) The configuration satisfies the various conditions.

Further, the 3a-th lens group comprises, in order from the object side, two biconvex positive lens components and a meniscus-shaped lens component with a concave surface facing the image plane side. The group is composed of, in order from the object side, a negative meniscus lens having a concave surface facing the object side and a positive lens having a convex surface facing the image side, and when the imaging magnification of the 3b-th lens group at the wide-angle end is β3b, 1.2 ≦ β3b ≦ 1.7 The condition (6) is satisfied.

[0009]

According to the present invention, the positive / negative / positive structure is simple, and the first lens group is moved to the object side during zooming from the wide-angle end to the telephoto end to reduce the overall length at the wide-angle end. I'm thinking. Further, by moving the third lens group toward the object side during zooming from the wide-angle end to the telephoto end, the zooming action is also shared by the third lens group, which causes a change in imaging magnification of the second lens group. Can be made smaller than the zoom ratio, and variations in various aberrations during zooming can be reduced.

Each conditional expression of the present invention will be described below. Conditional expression (1) defines an appropriate range of the focal length f1 of the first lens group for reducing the overall length of the zoom lens. If the upper limit of conditional expression (1) is exceeded, the focal length of the first lens unit becomes long and the total length of the zoom lens becomes large, which is contrary to the object of the present invention and is not preferable. On the other hand, if the lower limit of conditional expression (1) is exceeded, the focal length of the first lens group becomes short, the back focus of the first lens group becomes small accordingly, and the range of the distance between the first lens group and the second lens becomes possible. It becomes narrow and it becomes difficult to obtain a high zoom ratio. Furthermore, it becomes difficult to correct various aberrations such as spherical aberration and astigmatism in a well-balanced manner.

Conditional expression (2) defines an appropriate range of the focal length f2 of the second lens unit for increasing the zoom ratio of the zoom lens. If the lower limit of conditional expression (2) is exceeded, the focal length of the second lens group will become negatively large, and it will be difficult to obtain a high zoom ratio under conditional expression (1). On the other hand, if the upper limit of conditional expression (2) is exceeded, the focal length of the second lens group will become negative, and fluctuations in various aberrations such as spherical aberration, astigmatism, and distortion will be kept small. Becomes difficult.

Conditional expression (3) defines an appropriate range of the focal length f3 of the third lens group in order to reduce the overall length of the zoom lens. When the upper limit of the conditional expression (3) is exceeded, the focal length of the third lens group becomes long, and two conjugate points (object points with respect to the third lens group, that is, the first lens group and the second lens group) with respect to the third lens group. The distance between the image point formed by the group and the image point with respect to the third lens group, that is, the image point in the entire zoom lens system) becomes large, which causes an increase in the total length of the zoom lens, which is not preferable. On the contrary, if the lower limit of conditional expression (3) is exceeded, the focal length of the third lens group becomes short,
It becomes difficult to correct various aberrations including spherical aberration in a well-balanced manner. Also, the back focus at the wide-angle end becomes short, which is unsuitable for a single-lens reflex camera.

In the present invention as described above, in order to further reduce the total length, the third lens group G3 is arranged in order from the object side, the third lens group G3a having a positive refractive power, and the negative refractive power. It is preferable that the second lens group G3b has a third lens group G3b. With such a configuration, the third lens group is a telephoto type, the overall length of the zoom lens can be shortened, and positive distortion is generated in the negative 3b lens group. It is possible to cancel the negative distortion that tends to occur in. At this time, it is desirable to satisfy the conditional expressions (4) and (5).

If the lower limit of conditional expression (4) is exceeded, the focal length of the 3b-th lens group will become negative, and the action of making the third lens group a telephoto type will become weak, leading to an increase in the overall length. On the other hand, if the upper limit of conditional expression (4) is exceeded, the focal length of the 3b-th lens group will become negative, making it difficult to satisfactorily correct various aberrations including spherical aberration. Further, the back focus at the wide-angle end becomes short, which is unsuitable for a single-lens reflex camera.

Conditional expression (5) indicates the optimum range of the air gap between the 3a-th lens group and the 3b-th lens group under the conditional expression (4), and exceeds the upper limit of the conditional expression (5). Therefore, the entire length of the third lens group becomes long, and it becomes difficult to achieve a reduction in the overall length of the zoom lens. On the other hand, if the lower limit of conditional expression (5) is exceeded, it will be difficult to correct the negative distortion that tends to occur in the second lens group.

Further, in order to satisfactorily correct various aberrations, the third-a lens group G3a comprises, in order from the object side, two biconvex positive lens components and a meniscus shape with a concave surface facing the image side. It is desirable that the third-b lens group G3b comprises, in order from the object side, a negative meniscus lens having a concave surface facing the object side and a positive lens having a convex surface facing the image side. And conditional expressions (4) and (5)
Under the above conditions, it is desirable to satisfy the condition of conditional expression (6) in order to surely reduce the total length.

If the lower limit of conditional expression (6) is exceeded, the action of making the third lens group a telephoto type becomes weak, leading to an increase in the overall length. On the other hand, if the upper limit of conditional expression (6) is exceeded, the action of making the third lens group a telephoto type becomes excessive, and it becomes difficult to correct various aberrations including spherical aberration. In the 3a lens group, in order to balance and correct various aberrations such as spherical aberration and axial chromatic aberration, in the 3a lens group, the biconvex positive lens and the biconvex positive lens L32 are sequentially arranged from the object side. And a negative meniscus lens L33, and a cemented positive lens composed of a biconvex positive lens L34 and a biconcave negative lens L35. It is desirable that a stop be arranged immediately after the 3a lens group. I want it.

At this time, in order to satisfactorily correct the spherical aberration and set the Petzval sum to an appropriate value, it is desirable to satisfy the following conditional expression. n33-n32≥0.2 (7) n35-n34≥0.2 (8) Note that n32 is the refractive index of the biconvex positive lens L32, n33 is the refractive index of the negative meniscus lens L33, and n34 is the biconvex positive lens L34. , And n35 is the refractive index of the biconcave negative lens L35.

In order to satisfactorily correct the axial chromatic aberration,
It is desirable to satisfy the following conditional expressions. ν32−ν33 ≧ 10 (9) ν34−ν35 ≧ 25 (10) where ν32 is the Abbe number of the biconvex positive lens L32, ν33 is the Abbe number of the negative meniscus lens L33, and ν34 is the biconvex positive lens L.
The Abbe number of 34, ν35 is the Abbe number of the biconcave negative lens L35.

[0020]

EXAMPLES Each example according to the present invention will be described below. Example 1 FIG. 1 is a lens configuration diagram of Example 1,
From the object side, in order from the object side, a first lens unit G1 having a positive refracting power composed of a cemented positive lens composed of a negative meniscus lens L11 and a biconvex lens L12, and a biconvex positive lens L13, a biconcave negative lens L21 and a positive meniscus lens L22. Second lens group G2 having a negative refracting power, which is composed of a cemented negative lens of No. 2 and a biconcave negative lens L23 with a stronger concave surface facing the object side, a biconvex positive lens L31, a biconvex positive lens L32, and a negative meniscus lens L33. The third-a lens unit G3a having a positive refracting power, which is composed of a cemented positive lens composed of and a cemented positive lens composed of a biconvex positive lens L34 and a biconcave negative lens L35, a diaphragm S, and a concave surface directed toward the object side. It is composed of a third lens group G3 of positive refracting power composed of a third b lens group G3b of negative refracting power composed of a negative meniscus lens L36 and a positive meniscus lens L37 having a convex surface facing the image plane side.

During zooming from the wide-angle end to the telephoto end, both the first lens group G1 and the third lens group G3 move toward the object, and the second lens group G2 is closer to the object than at the wide-angle end at least at the telephoto end. It moves like a drop, and the first lens group G1 and the second lens group
The air gap between the lens group G2 increases and the air gap between the second lens group G2 and the third lens group G3 decreases. In the first embodiment, the second lens group G2 is moved toward the object to perform focusing from a long distance to a short distance. By using the second lens group G2 for focusing, it is possible to reduce the lens diameter of the first lens group G1 and shorten the closest shooting distance.

Table 1 below lists values of specifications of the first embodiment of the present invention. F in the specification table of the embodiment is the focal length,
F is the F number and 2ω is the angle of view. The leftmost number represents the order from the object side, r is the radius of curvature of the lens surface, d is the distance between the lens surfaces, and n and ν are the values of the refractive index and Abbe number for the d line (λ = 587.6 nm). .

[0023]

[Table 1] f = 70.60 to 202.44 F = 4.09 to 5.68 2ω = 35.2 to 11.9 ° (Variable spacing during zooming) f 70.5987 133.3121 202.4442 d 5 4.5707 28.4524 35.0774 d10 16.1257 7.7669 1.6901 Bf 41.7660 51.9255 69.3959 (conditional value) (1) f1 / fW = 1.452 (2) f2 / fW = -0.351 (3) f3 / fw = 0.436 (4) f3b / f3 = -3.89 (5) D / fw = 0.449 (6) β3b = 1.441 (7) n33-n32 = 0.27808 ( 8) n35-n34 = 0.28778 (9) ν32-ν33 = 18.1 (10) ν34-ν35 = 38.6 FIGS. 2, 3 and 4 show various aberrations at the wide angle end of the first embodiment. The figure shows various aberration diagrams in the intermediate focal length state and various aberration diagrams in the telephoto end state. In each aberration diagram, H is the incident ray height, Y is the image height, A is the incident angle of the chief ray, and d is the d line (λ = 58
7.6 nm) and g indicate the g-line (λ = 435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane and the broken line indicates the meridional image plane.

From each aberration diagram, it is apparent that various aberrations are satisfactorily corrected and that this embodiment has excellent image forming performance. Example 2 FIG. 5 is a lens configuration diagram of Example 2,
From the object side, in order from the object side, a first lens unit G1 having a positive refracting power composed of a cemented positive lens composed of a negative meniscus lens L11 and a biconvex lens L12, and a biconvex positive lens L13, a biconcave negative lens L21 and a positive meniscus lens L22. Second lens group G2 having a negative refracting power, which is composed of a cemented negative lens of No. 2 and a biconcave negative lens L23 with a stronger concave surface facing the object side, a biconvex positive lens L31, a biconvex positive lens L32, and a negative meniscus lens L33. The third-a lens unit G3a having a positive refracting power, which is composed of a cemented positive lens composed of and a cemented positive lens composed of a biconvex positive lens L34 and a biconcave negative lens L35, a diaphragm S, and a concave surface directed toward the object side. It is composed of a third lens group G3 of positive refracting power composed of a third b lens group G3b of negative refracting power composed of a negative meniscus lens L36 and a positive meniscus lens L37 having a convex surface facing the image plane side.

Upon zooming from the wide-angle end to the telephoto end, both the first lens group G1 and the third lens group G3 move toward the object, and the second lens group G2 is closer to the object at least at the telephoto end than at the wide-angle end. It moves like a drop, and the first lens group G1 and the second lens group
The air gap between the lens group G2 increases and the air gap between the second lens group G2 and the third lens group G3 decreases. In the second embodiment, the first lens group G1 is moved toward the object to perform focusing from a long distance to a short distance.

Table 2 below lists values of specifications of the second embodiment of the present invention. F in the specification table of the embodiment is the focal length,
F is the F number and 2ω is the angle of view. The leftmost number represents the order from the object side, r is the radius of curvature of the lens surface, d is the distance between the lens surfaces, and n and ν are the values of the refractive index and Abbe number for the d line (λ = 587.6 nm). .

[0027]

[Table 2] f = 70.60 to 202.44 F = 4.10 to 5.74 2ω = 35.1 to 11.9 ° (Variable spacing during zooming) f 70.5993 133.3080 202.4385 d 5 3.4404 26.9470 33.5720 d10 16.4234 8.0716 2.0628 Bf 41.5074 52.2703 70.0546 (Condition corresponding value) (1) f1 / fW = 1.452 (2) f2 / fW = -0.351 (3) f3 / fw = 0.436 (4) f3b / f3 = -3.89 (5) D / fw = 0.449 (6) β3b = 1.441 (7) n33-n32 = 0.27808 ( 8) n35−n34 = 0.28778 (9) ν32−ν33 = 18.1 (10) ν34−ν35 = 38.6 FIG. 6, FIG. 7, and FIG. 8 are aberrations at the wide-angle end of the second embodiment, respectively. The figure shows various aberration diagrams in the intermediate focal length state and various aberration diagrams in the telephoto end state. In each aberration diagram, H is the incident ray height, Y is the image height, A is the incident angle of the chief ray, and d is the d line (λ = 58
7.6 nm) and g indicate the g-line (λ = 435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane and the broken line indicates the meridional image plane.

From each aberration diagram, it is apparent that various aberrations are satisfactorily corrected and that this embodiment has excellent image forming performance.

[0029]

As described above, according to the present invention, a high-performance telephoto zoom lens having a small size and a high zoom ratio and suitable for a single-lens reflex camera can be achieved. In addition, by eccentrically driving any one of the first lens group, the second lens group, and the third lens group of the telephoto zoom lens of the present invention in the direction orthogonal to the optical axis, the vibration of the entire zoom lens is offset,
The image can be stabilized.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram of Example 1. FIG.

FIG. 2 is a diagram of various types of aberration at the wide-angle end of Example 1.

FIG. 3 is a diagram of various types of aberration at the intermediate focal length of Example 1.

FIG. 4 is a diagram of various types of aberration at the telephoto end according to the first exemplary embodiment.

FIG. 5 is a lens configuration diagram of Example 2.

FIG. 6 is a diagram of various types of aberration at the wide-angle end of Example 2;

FIG. 7 is a diagram of various types of aberration at the intermediate focal length of Example 2.

FIG. 8 is a diagram of various types of aberration at the telephoto end of the second embodiment.

[Explanation of sign]

 G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G3a ... 3a lens group G3b ... 3b lens group S ...

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[Submission date] June 15, 1994

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Claims (3)

[Claims] 1. A first lens element having a positive refractive power in order from the object side.
A lens unit, a second lens unit having a negative refracting power, and a third lens unit having a positive refracting power, and at least the first lens unit and the above-mentioned first lens unit upon zooming from the wide-angle end to the telephoto end. The third lens group moves toward the object, the air gap between the first lens group and the second lens group increases, the air gap between the second lens group and the third lens group decreases, and When the focal length of one lens unit is f1, the focal length of the second lens unit is f2, the focal length of the third lens unit is f3, and the focal length of the entire system at the wide-angle end is fW, 1.25≤ A telephoto zoom lens characterized by satisfying various conditions of f1 / fw <1.50 -0.37 <f2 / fw <-0.30 0.37 <f3 / fw <0.46. 2. The third lens group comprises, in order from the object side, a 3a lens group having a positive refractive power and a 3b lens group having a negative refractive power, and the focal length of the 3b lens group is f3b and the air gap between the 3a-th lens group and the 3b-th lens group is D, the conditions of -5≤f3b / f3≤-3 0.3≤D / fW≤0.6 are satisfied. The telephoto zoom lens according to claim 1, wherein 3. The third-a lens unit, in order from the object side,
It is composed of two biconvex positive lens components and a meniscus lens component with a concave surface facing the image plane side.
The lens group is composed of, in order from the object side, a negative meniscus lens having a concave surface facing the object side and a positive lens having a convex surface facing the image side, and the imaging magnification of the 3b-th lens group at the wide-angle end is β.
3. The telephoto zoom lens according to claim 2, wherein when 3b is satisfied, the condition of 1.2 ≦ β3b ≦ 1.7 is satisfied.