JPH06300972A - Zoom lens with wide field angle - Google Patents

Abstract

PURPOSE:To obtain a wide-angle zoom lens whose lens system is reduced in size on the whole by providing three lens groups in total and properly setting the lens constitution of the respective lens groups. CONSTITUTION:This zoom lens has three lens groups which are a 1st group L1 with negative refracting power, a 2nd group L2 with positive refracting power, and a 3rd group L3 with negative refracting power in order from the object side and the power is varied by varying the intervals between the respective lens groups; and a condition is satisfied, where f1 is the focal length of the 1st group L1, fwW and fT are the focal lengths of the whole system at the wide-angle end and telephoto end, and Y is the diagonal length of an effective picture plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide-angle zoom lens suitable for a 35 mm film photographic camera, a video camera, an SV camera, and the like. It has a lens group, and by appropriately setting the lens configuration of these three lens groups, a zoom ratio of 1.5, an F number of 3.6 to 4.6, and a shooting angle of view, which is aimed at downsizing the entire lens system. The present invention relates to a zoom lens having a wide angle of view of about 92 ° to 72 °.

[0002]

2. Description of the Related Art Since a so-called negative lead type zoom lens in which a lens unit having a negative refracting power precedes has been comparatively easy to make a wide angle of view, it is often used in a zoom lens having a photographing angle of view of 70 ° or more. It is used.

For example, Japanese Laid-Open Patent Publication No. 59-16248 has two lens groups, a first lens group having a negative refractive power and a second lens group having a positive refractive power, and the zooming is performed by changing the distance between the two lens groups. The so-called short zoom lens is proposed.

Further, in Japanese Patent Laid-Open No. 64-72114, the first group of negative refracting power and the second group of positive refracting power are sequentially arranged from the object side.
It proposes a three-group zoom lens having a wide field angle, which has three groups, that is, a group and a third group having a negative refractive power, and each lens group is moved for zooming.

[0005]

Generally, a negative lead type zoom lens is relatively easy to have a wide angle of view. Therefore, it is expected to be used as a lens system for recent panoramic photography.

However, in order to achieve a wide field angle of 90 ° or more and obtain good optical performance over the entire screen, it is necessary to appropriately set the refractive power arrangement and lens configuration of each lens group. If the refractive power arrangement or lens configuration of each lens group is improper, the variation of aberrations due to zooming will increase even if the number of lenses is increased, making it difficult to obtain high optical performance over the entire zoom range. come.

According to the present invention, in a three-group zoom lens having three lens groups as a whole preceded by a lens group having a negative refractive power, the total lens length is shortened by appropriately setting the lens configuration of each lens group. While shooting angle of view 92 °
It is an object of the present invention to provide a wide-angle zoom lens having a wide angle of view of about 72 ° and high optical performance over the entire zoom range.

[0008]

A wide-angle zoom lens according to the present invention comprises, in order from the object side, a first group having a negative refractive power, a second group having a positive refractive power, and a third group having a negative refractive power. Each of the three lens groups is used for zooming by changing the distance between the lens groups, the focal length of the first group is f ₁ , the focal lengths of the entire system at the wide-angle end and the telephoto end are f _W and f _T , respectively. When the diagonal length of the effective screen is Y

[0009]

[Equation 2] It is characterized by satisfying the following condition.

[0010]

1 to 6 are lens cross-sectional views of Numerical Examples 1 to 6 to be described later of the present invention. 7 to 9 are aberration diagrams at the wide-angle end, the middle, and the telephoto end of Numerical Embodiment 1 of the present invention, and FIG.
To FIG. 12 are aberration diagrams of the numerical example 2 of the present invention at the wide-angle end, the middle, and the telephoto end, and FIGS. 13 to 15 are aberration diagrams of the wide-angle end, the intermediate, and the telephoto end of the numerical example 3 of the present invention. To FIG. 18 are aberration diagrams at the wide-angle end, the middle, and the telephoto end of Numerical Embodiment 4 of the present invention, and FIGS. 19 to 21 are the wide-angle end, the middle, and Numerical Embodiment 5 of the present invention.
22 to 24 are aberration diagrams at the wide-angle end, the middle, and the telephoto end in Numerical Example 6 of the present invention.

In the lens sectional views of FIGS. 1 to 6,
(A) shows the wide-angle end, (B) shows the middle, and (C) shows the telephoto end. In the figure, L1 is a first group having a negative refractive power, L2 is a second group having a positive refractive power, L3 is a third group having a negative refractive power, SP is an aperture stop, and FP is an image plane.

In this embodiment, during zooming from the wide-angle end to the telephoto end, the air gap between the first group and the second group decreases, and the air gap between the second group and the third group decreases. The first group is moved so as to have a convex locus on the image plane side, and both the second group and the third group are linearly or non-linearly moved to the object side as indicated by arrows.

By configuring each lens group so as to satisfy the above-mentioned conditional expressions (1) and (2) at this time, the photographing angle of view 90 while shortening the total lens length and ensuring a predetermined zoom ratio is obtained. The angle of view is widened by about °.

Focusing is performed by moving the first group.

Next, the technical meaning of the conditional expressions (1) and (2) will be described.

Conditional expression (1) relates to the ratio of the focal length of the first lens group to the intermediate focal length (intermediate zoom position) in the focal length range of the entire system, and mainly changes while making the overall lens length shorter. This is for ensuring good optical performance over the double range.

If the lower limit of conditional expression (1) is exceeded and the negative refracting power of the first lens unit becomes too strong, the tele ratio on the telephoto side will increase, and the overall lens length on the telephoto side will increase and zooming will occur. Along with this, the variation in aberration becomes large.

If the negative refracting power of the first lens unit becomes too weak beyond the upper limit, aberration correction will be facilitated, but the amount of movement of the first lens unit for ensuring a predetermined zoom ratio will increase. This is not good because the total lens length becomes longer.

Conditional expression (2) is for the image size,
That is, with respect to the ratio of the intermediate focal length (intermediate zoom position) in the focal length range of the entire system to the shooting angle of view, it is mainly for ensuring a predetermined zoom ratio and widening the angle of view. .

When the lower limit of conditional expression (2) is exceeded and the focal length on the telephoto side becomes too short, it becomes difficult to secure a predetermined zoom ratio. If the focal length on the telephoto side becomes too long beyond the upper limit, the distance between the first group and the second group on the wide angle side becomes wide, and the diameter of the front lens increases when widening the angle of view. It's not good because it comes.

In the present invention, the photographing field angle at the wide-angle end is 90 °.
In order to obtain good optical performance over the entire zoom range, the focal lengths of the second lens unit and the third lens unit should be f ₂ and f, respectively.
_{When 3} is set, 0.4 <| f ₁ | / Y <0.7 (3) 0.2 <| f ₂ / f ₃ | <0.8 (4) It is better to satisfy the conditions.

Conditional expression (3) relates to the ratio of the focal length of the first lens unit to the image size, and is mainly for ensuring the predetermined zoom ratio while shortening the overall lens length.

If the negative refracting power of the first lens unit becomes too strong beyond the lower limit of conditional expression (3), the total lens length on the telephoto side becomes long. When the upper limit is exceeded and the negative refractive power of the first lens unit becomes too weak, it becomes difficult to secure a predetermined zoom ratio while widening the angle of view.

Conditional expression (4) relates to the ratio of the focal lengths of the second lens unit and the third lens unit, and is mainly for ensuring a predetermined back focus and variable magnification ratio.

When the lower limit of conditional expression (4) is exceeded and the negative refractive power of the third lens unit becomes too weak, the telephoto type lens collapses,
It becomes difficult to secure a predetermined zoom ratio while shortening the total lens length. On the other hand, if the negative refractive power of the third lens unit exceeds the upper limit and becomes too strong, the back focus at the wide angle end becomes short and the rear lens diameter increases, which is not preferable.

In the present invention, in order to maintain a good balance of the optical performance of the entire screen, it is preferable to dispose a stop in the second lens unit and to provide at least one lens surface closer to the object than the stop with an aspherical surface. .

In the present invention, the second group and the third group may be moved non-linearly to fix the first group during zooming. Focusing may be performed by the second group or the third group.

In the zoom lens according to the present invention, the lens construction of the first lens group in Numerical Embodiments 1, 3, 4, and 6 is a meniscus negative lens having a convex surface facing the object side, a negative lens, and a convex surface facing the object side. It consists of three meniscus-shaped positive lenses. Numerical Examples 2 and 5
In this case, it is composed of two lenses, 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.

In Numerical Example 2, the lens surface on the image side of the positive lens is an aspherical surface.

The lens configuration of the second lens group is numerical examples 1, 2,
In Nos. 3, 5 and 6, a positive lens having a convex surface on both lens surfaces with a strong refracting surface facing the image side, a cemented lens of a positive lens and a negative lens, a cemented lens of a positive lens and a negative lens, and a positive lens It consists of 6 lenses.

In Numerical Embodiment 4, a positive lens, a cemented lens of a positive lens and a negative lens, a negative lens and a positive lens are used.
It consists of two lenses.

In Numerical Embodiments 1 to 6, the lens structure of the third lens group is composed of two lenses, a positive lens and a negative lens having a strong negative refraction surface facing the object side.

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

Table 1 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples.

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

[0036]

[Equation 3] It is expressed by (Numerical Example 1) F = 21.3 to 29.5 FNO = 1: 3.6 to 4.6 2ω = 91.2 ° to 72.4 ° R 1 = 69.48 D 1 = 1.30 N 1 = 1.83400 ν 1 = 37.2 R 2 = 14.49 D 2 = 4.45 R 3 = -1660.67 D 3 = 1.20 N 2 = 1.58313 ν 2 = 59.4 R 4 = 33.96 D 4 = 1.72 R 5 = 19.42 D 5 = 2.50 N 3 = 1.80518 ν 3 = 25.4 R 6 = 42.54 D 6 = Variable R 7 = 56.58 D 7 = 2.20 N 4 = 1.60738 ν 4 = 56.8 R 8 = -33.38 D 8 = 1.24 R 9 = (Aperture) D 9 = 0.46 R10 = 17.88 D10 = 4.60 N 5 = 1.63930 ν 5 = 44.9 R11 =- 13.01 D11 = 2.10 N 6 = 1.80610 ν 6 = 41.0 R12 = 53.04 D12 = 0.25 R13 = 26.08 D13 = 3.30 N 7 = 1.69680 ν 7 = 55.5 R14 = -22.28 D14 = 1.00 N 8 = 1.80518 ν 8 = 25.4 R15 = 16.65 D15 = 1.15 R16 = 215.06 D16 = 2.10 N 9 = 1.66680 ν 9 = 33.0 R17 = -16.91 D17 = Variable R18 = -41.97 D18 = 2.20 N10 = 1.69895 ν10 = 30.1 R19 = -24.59 D19 = 3.59 R20 = -13.08 D20 = 1.00 N11 = 1.71300 ν11 = 53.8 R21 = -35.54

[0037]

[Table 1] R 4: Aspheric surface A = 0, D = 2.49 × 10 ⁻⁹ B = −2.38 × 10 ⁻⁶ , E = −9.68 × 10 ⁻¹² C = −1.83 × 10 ⁻⁷ (Numerical example 2) F = 21.4 ~ 29.6 FNO = 1: 3.6 ~ 4.6 2 ω = 91.2 ° ~ 72.4 ° R 1 = 136.29 D 1 = 1.64 N 1 = 1.80400 ν 1 = 46.6 R 2 = 12.62 D 2 = 5.95 R 3 = 18.86 D 3 = 3.28 N 2 = 1.78472 ν 2 = 25.7 R 4 = 29.62 D 4 = Variable R 5 = 88.19 D 5 = 2.90 N 3 = 1.58313 ν 3 = 59.4 R 6 = -24.77 D 6 = 0.25 R 7 = 18.49 D 7 = 5.04 N 4 = 1.63930 ν 4 = 44.9 R 8 = -13.46 D 8 = 1.89 N 5 = 1.80610 ν 5 = 41.0 R 9 = 36.27 D 9 = 1.39 R10 = 20.69 (aperture) D10 = 1.13 R11 = 20.80 D11 = 3.32 N 6 = 1.62299 ν 6 = 58.2 R12 = -19.82 D12 = 1.26 N 7 = 1.80518 ν 7 = 25.4 R13 = 19.92 D13 = 1.01 R14 = 111.24 D14 = 2.90 N 8 = 1.64769 ν 8 = 33.8 R15 = -17.72 D15 = variable R16 = 130.36 D16 = 3.15 N 9 = 1.80518 ν 9 = 25.4 R17 = -55.73 D17 = 4.05 R18 = -13.96 D18 = 1.51 N10 = 1.77250 ν10 = 49.6 R19 = -81.13

[0038]

[Table 2] R 4: Aspheric surface A = 0, D = -2.33 × 10 ^-10 B = -9.67 × 10 ^-6 , E = 2.92 × 10 ^-14 C = -6.17 × 10 ^-8 (Numerical example 3) F = 21.4 ~ 29.5 FNO = 1: 3.6 ~ 4.6 2 ω = 90.6 ° ~ 72.4 ° R 1 = 359.46 D 1 = 1.39 N 1 = 1.83400 ν 1 = 37.2 R 2 = 14.53 D 2 = 3.25 R 3 = 48.81 D 3 = 1.26 N 2 = 1.69680 ν 2 = 55.5 R 4 = 20.87 D 4 = 1.89 R 5 = 19.17 D 5 = 3.78 N 3 = 1.80518 ν 3 = 25.4 R 6 = 63.71 D 6 = variable R 7 = 50.13 D 7 = 3.40 N 4 = 1.51633 ν 4 = 64.2 R 8 = -24.69 D 8 = 0.25 R 9 = 15.73 D 9 = 4.16 N 5 = 1.58313 ν 5 = 59.4 R10 = -18.99 D10 = 1.13 N 6 = 1.80610 ν 6 = 41.0 R11 = 70.65 D11 = 1.89 R12 = (Aperture) D12 = 1.26 R13 = 29.68 D13 = 2.27 N 7 = 1.51633 ν 7 = 64.2 R14 = -27.29 D14 = 1.26 N 8 = 1.80518 ν 8 = 25.4 R15 = 22.30 D15 = 1.01 R16 = 75.19 D16 = 3.15 N 9 = 1.66680 ν 9 = 33.0 R17 = -18.70 D17 = variable R18 = 262.09 D18 = 2.52 N10 = 1.64769 ν10 = 33.8 R19 = -39.83 D19 = 3.87 R20 = -10.44 D20 = 1.51 N11 = 1.71300 ν11 = 53.8 R21 = -59.56

[0039]

[Table 3] R 9: Aspheric surface A = 0, D = 9.07 × 10 ⁻¹⁰ B = −3.64 × 10 ⁻⁶ , E = 0 C = −3.08 × 10 ⁻⁷ (Numerical example 4) F = 21.4 to 29.5 FNO = 1 : 3.6 to 4.6 2 ω = 90.6 ° to 72.4 ° R 1 = 462.84 D 1 = 1.39 N 1 = 1.83400 ν 1 = 37.2 R 2 = 16.56 D 2 = 3.36 R 3 = 46.27 D 3 = 1.26 N 2 = 1.69680 ν 2 = 55.5 R 4 = 20.33 D 4 = 1.88 R 5 = 20.44 D 5 = 4.03 N 3 = 1.80518 ν 3 = 25.4 R 6 = 76.19 D 6 = Variable R 7 = -2143.42 D 7 = 3.78 N 4 = 1.51633 ν 4 = 64.2 R 8 = -27.09 D 8 = 0.25 R 9 = 18.30 D 9 = 5.29 N 5 = 1.58313 ν 5 = 59.4 R10 = -22.63 D10 = 1.13 N 6 = 1.80518 ν 6 = 25.4 R11 = -91.98 D11 = 2.02 R12 = ( Aperture) D12 = 2.90 R13 = 88.01 D13 = 1.26 N 7 = 1.80518 ν 7 = 25.4 R14 = 19.53 D14 = 1.01 R15 = 84.29 D15 = 2.90 N 8 = 1.63930 ν 8 = 44.9 R16 = -20.06 D16 = variable R17 = -47.55 D17 = 2.52 N 9 = 1.64769 ν 9 = 33.8 R18 = -22.68 D18 = 3.39 R19 = -12.03 D19 = 1.51 N10 = 1.71300 ν10 = 53.8 R20 = -51.94

[0040]

[Table 4] R 9: Aspheric surface A = 0, D = 7.04 × 10 ^-10 B = -1.82 × 10 ^-5 , E = 0 C = -2.14 × 10 ^-7 (Numerical example 5) F = 21.4 to 29.5 FNO = 1 : 3.6 to 4.6 2 ω = 90.6 ° to 72.4 ° R 1 = 181.65 D 1 = 1.64 N 1 = 1.80400 ν 1 = 46.6 R 2 = 13.07 D 2 = 5.82 R 3 = 16.81 D 3 = 3.28 N 2 = 1.80518 ν 2 = 25.4 R 4 = 23.28 D 4 = Variable R 5 = 63.88 D 5 = 3.15 N 3 = 1.58313 ν 3 = 59.4 R 6 = -23.56 D 6 = 0.25 R 7 = 18.49 D 7 = 5.04 N 4 = 1.63930 ν 4 = 44.9 R 8 = -12.55 D 8 = 1.89 N 5 = 1.80610 ν 5 = 41.0 R 9 = 28.91 D 9 = 1.39 R10 = 20.69 (Aperture) D10 = 1.13 R11 = 21.37 D11 = 3.32 N 6 = 1.69680 ν 6 = 55.5 R12 = -26.39 D12 = 1.26 N 7 = 1.80518 ν 7 = 25.4 R13 = 18.26 D13 = 1.01 R14 = 227.69 D14 = 2.77 N 8 = 1.66680 ν 8 = 33.0 R15 = -17.94 D15 = Variable R16 = 126.60 D16 = 3.15 N 9 = 1.68893 ν 9 = 31.1 R17 = -47.91 D17 = 3.49 R18 = -17.61 D18 = 1.51 N10 = 1.71300 ν10 = 53.8 R19 = -449.15

[0041]

[Table 5] R 5: Aspheric surface A = 0, D = −9.73 × 10 ⁻¹⁰ B = −1.1 × 10 ⁻⁶ , E = 0 C = 1.24 × 10 ⁻⁷ (Numerical example 6) F = 24.9 to 34.0 FNO = 1 : 3.6 to 4.6 2 ω = 82.0 ° to 72.4 ° R 1 = 71.73 D 1 = 1.24 N 1 = 1.83400 ν 1 = 37.2 R 2 = 14.23 D 2 = 3.76 R 3 = -199.96 D 3 = 1.02 N 2 = 1.58313 ν 2 = 59.4 R 4 = 48.96 D 4 = 1.76 R 5 = 19.67 D 5 = 2.84 N 3 = 1.80518 ν 3 = 25.4 R 6 = 40.89 D 6 = Variable R 7 = 52.66 D 7 = 1.90 N 4 = 1.60738 ν 4 = 56.8 R 8 = -36.42 D 8 = 1.24 R 9 = (Aperture) D 9 = 0.46 R10 = 17.66 D10 = 4.58 N 5 = 1.63930 ν 5 = 44.9 R11 = -12.85 D11 = 2.10 N 6 = 1.80610 ν 6 = 41.0 R12 = 52.95 D12 = 0.16 R13 = 25.98 D13 = 3.27 N 7 = 1.69680 ν 7 = 55.5 R14 = -29.01 D14 = 0.85 N 8 = 1.80518 ν 8 = 25.4 R15 = 16.70 D15 = 1.15 R16 = 407.90 D16 = 1.90 N 9 = 1.66680 ν 9 = 33.0 R17 = -17.39 D17 = variable R18 = (flare diaphragm) D18 = variable R19 = -33.35 D19 = 1.91 N10 = 1.69895 ν10 = 30.1 R20 = -22.48 D20 = 3.14 R21 = -12.96 D21 = 0.92 N11 = 1.71300 ν11 = 53.8 R22 = -30.45

[0042]

[Table 6] R 4: Aspheric surface A = 0, D = 2.15 × 10 ^-9 B = 1.76 × 10 ^-5 , E = -8.64 × 10 ^-12 C = -1.57 × 10 ^-7

[0043]

[Table 7]

[0044]

As described above, according to the present invention, in the three-group zoom lens having three lens groups as a whole preceded by the lens group having negative refractive power, the lens configuration of each lens group is appropriately set. As a result, it is possible to achieve a wide-angle zoom lens having a wide field angle of about 92 ° to 72 ° and a high optical performance over the entire zoom range while shortening the total lens length.

[Brief description of drawings]

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

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

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

FIG. 4 is a lens cross-sectional view of Numerical Example 4 of the present invention.

FIG. 5 is a lens cross-sectional view of Numerical Example 5 of the present invention.

FIG. 6 is a lens cross-sectional view of Numerical Example 6 of the present invention.

FIG. 7 is an aberration diagram at a wide-angle end according to Numerical Example 1 of the present invention.

FIG. 8 is an intermediate aberration diagram of Numerical example 1 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end according to Numerical Example 1 of the present invention.

FIG. 10 is an aberration diagram at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 11 is an intermediate aberration diagram of Numerical example 2 of the present invention.

FIG. 12 is an aberration diagram at a telephoto end according to Numerical Example 2 of the present invention.

FIG. 13 is an aberration diagram at the wide-angle end according to Numerical Example 3 of the present invention.

FIG. 14 is an intermediate aberration diagram of Numerical Example 3 of the present invention.

FIG. 15 is an aberration diagram at a telephoto end according to Numerical Example 3 of the present invention.

FIG. 16 is an aberration diagram at a wide-angle end according to Numerical Example 4 of the present invention.

FIG. 17 is an intermediate aberration diagram of Numerical Example 4 of the present invention.

FIG. 18 is an aberration diagram at a telephoto end according to Numerical Example 4 of the present invention.

FIG. 19 is an aberration diagram at a wide-angle end according to Numerical Example 5 of the present invention.

FIG. 20 is an intermediate aberration diagram of Numerical example 5 of the present invention.

FIG. 21 is an aberration diagram at a telephoto end according to Numerical Example 5 of the present invention.

FIG. 22 is an aberration diagram at a wide-angle end according to Numerical Example 6 of the present invention.

FIG. 23 is an intermediate aberration diagram of Numerical Example 6 of the present invention.

FIG. 24 is an aberration diagram at a telephoto end according to Numerical Example 6 of the present invention.

[Explanation of symbols]

 L1 1st group L2 2nd group L3 3rd group SP Aperture FP Image plane d d line g g line ΔS Sagittal image plane ΔM Meridional image plane FP Flare aperture

Claims (4)

[Claims] 1. A three-lens group having, in order from the object side, a negative refractive power first group, a positive refractive power second group, and a negative refractive power third group, and the distance between each lens group is changed. When the focal length of the first lens group is f ₁ , the focal lengths of the entire system at the wide-angle end and the telephoto end are f _W and f _T , respectively, and the diagonal length of the effective screen is Y, then Wide-angle zoom lens characterized by satisfying the following conditions. 2. When zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, and the distance between the second group and the third group decreases so as to decrease. The zoom lens having a wide angle of view according to claim 1, wherein both the third lens unit and the third lens unit are moved toward the object side. 3. The focal lengths of the second lens unit and the third lens unit are f
₂ and f ₃ , the condition 0.4 <| f ₁ | / Y <0.7 0.2 <| f ₂ / f ₃ | <0.8 is satisfied. Wide-angle zoom lens. 4. A wide-angle image display device according to claim 3, wherein a stop is arranged in the second lens group, and at least one lens surface closer to the object than the stop is provided with an aspherical surface. Angle zoom lens.