JPH09211326A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the simple-constitution zoom lens of a wide angle having a specified viewing angle and specified variable power ratio and being suitable for a video camera by moving a first to a third lens groups at a variable power time and arranging a brightness diaphragm on an optical axis among the first to the third lens groups to be fixed. SOLUTION: The first group is constituted of a negative lens whose concave surface is faced to an image side, a positive lens whose convex surface is faced to the image side and the negative lens whose concave surface is faced to an object side in turn from the object side. The second group is constituted of one positive lens. The third group is constituted of four lenses of the positive lens, the negative lens, the positive lens and the positive lens in turn from the object side. Besides, the diaphragm is arranged to be fixed on the image side of the second group. At the variable power time, the first group is moved so as to be positioned on the image side at a telephoto end in comparison with at a wide angle end. Then, the second group is fixed and the third group is monotonously moved to the object side from the image side extending over the telephoto end from the wide angle end. Besides, the brightness diaphragm is arranged to be fixed on the optical axis among the first to the third groups.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, especially a wide-angle zoom lens suitable for a video camera.

[0002]

2. Description of the Related Art In recent years, as a zoom lens system for a consumer video camera having a high zoom ratio, positive, negative, positive, and positive four-group structures are arranged in order from the object side. The mainstream method is to correct the image position variation due to zooming and focus in the positive fourth lens group.
This type of zoom lens is advantageous for achieving a high zoom ratio, but has a complicated lens frame structure and is disadvantageous for widening the angle of view.

Further, as a conventional example of a zoom lens having a simple structure, the zoom ratio is as low as 2 to 3 times, as disclosed in Japanese Patent Laid-Open No. 63-2.
92106, JP-A-3-288113 and JP-A-3-288113.
As the zoom lens disclosed in each publication of JP-A-203709, a negative, positive, and positive three-group configuration is known. The negative, positive, and positive three-group structure as in these conventional examples is not suitable for high zooming, but it is advantageous for widening the angle and the lens frame structure can be easily made compared to the four-group structure. Have the advantages of.

[0004]

Among the conventional examples of the above-mentioned three-group construction, the zoom lens disclosed in Japanese Patent Laid-Open No. Sho 63-292106 has a wide field angle (2ω) of about 70 °, but is bright. Since the aperture stop and the flare stop move in the optical axis direction during zooming, the lens frame structure becomes complicated although the number of lens groups is as small as three. In addition, JP-A-3-28
The zoom lens described in Japanese Patent No. 8113 has a narrow angle of view (2ω) of 46 °, and is disclosed in JP-A-3-203709.
The zoom lens described in No. 44 has an angle of view (2ω) of 44
° and narrow.

The present invention is suitable for a video camera having a negative, positive, and positive three-group structure, an angle of view (2ω) of about 65 °, and a zoom ratio of about 2 to 3 and a simple lens frame structure. To provide a wide-angle zoom lens.

[0006]

A zoom lens according to the present invention has, for example, a configuration as shown in FIG. 1, and comprises, in order from the object side, a first lens unit having a negative refractive power and a first lens unit having a positive refractive power. It consists of the second group and the third group having a positive refractive power, and during zooming, the first group moves so that it is located closer to the image side at the telephoto end than at the wide-angle end, and the second group is fixed, It is characterized in that the third lens unit moves monotonously from the image side to the object side from the wide-angle end to the telephoto end, and the aperture stop is fixedly arranged on the optical axis between the first lens unit and the third lens unit.

In order to achieve a wide angle in a zoom lens having a three-group configuration, the first group, the third group, and
The placement of the aperture stop is important. In the present invention, the diameter of the lens is reduced by arranging the aperture stop substantially at the center of the first group and the third group so that the off-axis ray height passing through the first group and the third group is kept low. And, it becomes possible to correct off-axis aberrations, and as a result, it becomes possible to realize a wide angle of view. With this configuration, when zooming, the first group is moved so that it is located closer to the image side at the telephoto end than at the wide-angle end, and the third group is moved from the wide-angle end to the telephoto end. By moving monotonously to the object side in the opposite direction to the first group, the space between the first group and the third group is effectively used while the aperture stop is fixed near the second group for zooming. You can do it.
Further, by fixing the aperture stop during zooming together with the second lens group, the lens frame structure can be simplified. The second lens group has the function of reducing the divergence angle of the divergent light beam from the first lens group to suppress the height of the light beam incident on the third lens group and the function of adjusting the back focus of the entire system. In this way, by suppressing the height of the light ray incident on the third lens unit, it is advantageous for downsizing the third lens unit and correcting aberrations. Further, it is possible to secure an appropriate back focus according to the thickness of an optical member such as an optical filter arranged between the lens system and the image pickup device.

As described above, the zoom lens of the present invention is
With the configuration as described above, a wide angle of view and a simple configuration can be achieved.

Further, in order to reduce the cost of the lens system, it is preferable to minimize the number of lenses forming each group.

The first group is composed of, in order from the object side, a negative lens having a concave surface facing the image side, a positive lens having a convex surface facing the image side, and a negative lens having a concave surface facing the object side. Is desirable.

In widening the angle of view of a lens system, correction of distortion and lateral chromatic aberration is particularly important. First, regarding the correction of distortion, it is preferable to divide the negative refracting power into two to reduce the occurrence of distortion. In addition, the insufficient correction amount of the distortion aberration can be corrected by using one positive lens. With respect to the disposition of the positive lens, it is advantageous to correct the chromatic aberration of magnification by arranging the first group with good symmetry, and by disposing between the two negative lenses, the first group is arranged to have negative, positive, It is desirable that the arrangement has good negative symmetry. In addition, if the negative lens closest to the object side is concave on the image side, the positive lens is convex on the image side, and the negative lens on the image side is concave on the object side, distortion and chromatic aberration of magnification will occur. More preferable for correction.

Further, it is preferable that the second lens unit is composed of only one positive lens. The role of the second lens group in correcting the aberration is one in order to satisfactorily correct these aberrations of the entire lens system by balancing spherical aberration and axial chromatic aberration that are overcorrected in the first lens group and the third lens group. It is possible to configure with a positive lens.

It is desirable that the third lens group be composed of, in order from the object side, three lenses of a positive lens, a negative lens and a positive lens or four lenses of a positive lens, a negative lens, a positive lens and a positive lens. Since the third lens unit has a variable power function and an image forming function, it is desirable that the third lens unit be of a triplet type composed of at least a positive lens, a negative lens and a positive lens, and the positive lens on the image side is divided into two. A four-lens structure including a positive lens, a negative lens, a positive lens, and a positive lens is advantageous in correcting off-axis aberrations.

In order to further reduce the size of the lens system and correct aberrations better, the following conditions (1), (2),
It is desirable to satisfy (3).

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3) 0.5 <z ₁ / z ₃ <4 , F ₁ , f ₂ , and f ₃ are the first group, the second group, and the third group, respectively.
The focal lengths of the group, z ₁ and z _3, are absolute values of the displacement amounts at the wide-angle end and the telephoto end of the first group and the third group, respectively.

The condition (1) relates to miniaturization of the lens and defines the ratio of the refractive powers of the first and third groups. In the zoom lens according to the present invention, it is preferable that the first lens unit has a sufficient refractive power in order to efficiently perform zooming. When the lower limit of −1.5 is not exceeded in condition (1), the refractive power of the first lens group becomes weak, the total length of the lens system increases, and the lens diameter of the first lens group also increases. Further, in the condition (1), when the upper limit of -0.4 is exceeded, the negative distortion aberration increases.

The condition (2) is a condition defined for ensuring an appropriate back focus, and defines the ratio of the refractive powers of the second lens unit and the third lens unit. In the condition (2), if the lower limit of 1.6 is exceeded, it is disadvantageous in securing the back focus and the arrangement of the optical filter is limited. If the upper limit of 9 to condition (2) is exceeded, it is advantageous to secure the back focus, but this is not preferable because the total length of the lens system increases.

The condition (3) relates to widening of the angle of view and zooming efficiency, and defines the movement of the first and third groups. If the upper limit of 4 of the condition (3) is exceeded, it is advantageous for widening the angle of view, but it is disadvantageous for ensuring the zoom ratio. On the other hand, if the lower limit of 0.5 is exceeded, it is advantageous to secure the zoom ratio, but is disadvantageous to widening the angle.

In the zoom lens of the present invention described above, it is more preferable to set the lower limit to 1.8 or the upper limit to 7 or the lower limit and the upper limits to 1.8 and 7, respectively, under the condition (2). That is, it is desirable that one of the following conditions is satisfied instead of the condition (2).

(2-1) 1.8 <f ₂ / f ₃ <9 (2-2) 1.6 <f ₂ / f ₃ <7 (2-3) 1.8 <f ₂ / f ₃ < 7 It is more desirable to set the lower limit of condition (2) to 2 or the upper limit to 5, or the lower limit and the upper limit to 2 and 5, respectively. That is, it is desirable to satisfy the following conditions.

(2-4) 2 <f ₂ / f ₃ <9 (2-5) 1.6 <f ₂ / f ₃ <5 (2-6) 2 <f ₂ / f ₃ <5 Further conditions ( Instead of 2), the following conditions may be satisfied.

(2-7) 2 <f ₂ / f ₃ <7 (2-8) 1.8 <f ₂ / f ₃ <5 Also, in condition (3), the lower limit is set to 0.8, or Set the upper limit to 3.5 or the lower limit to 0.8,
It is more preferable to set it to 0.35.

(3-1) 0.8 <z ₁ / z ₃ <4 (3-2) 0.5 <z ₁ / z ₃ <3.5 (3-3) 0.8 <z ₁ / z ₃ <3.5 Further, in the condition (3), the lower limit is set to 1.2, the upper limit is set to 3, or the lower limit and the upper limit are set to 1.
It is more desirable to set it to 2 or 3.

(3-4) 1.2 <z ₁ / z ₃ <4 (3-5) 0.5 <z ₁ / z ₃ <3 (3-6) 1.2 <z ₁ / z ₃ < 3 Further, the following condition may be satisfied instead of the condition (3).

(3-7) 1.2 <z ₁ / z ₃ <3.5 (3-8) 0.8 <z ₁ / z ₃ <3 In the zoom lens of the present invention, the condition (2), (3)
In both cases, a lens system satisfying the above conditions may be used instead of these conditions. That is, instead of the condition (2), any of the conditions (2-1) to (2-8) and at the same time, instead of the condition (3), the conditions (3-1) to (3-8).
A lens system having a configuration that satisfies

Use of an aspherical surface in the zoom lens of the present invention is advantageous for aberration correction and size reduction of the lens system. When the aspherical surface is introduced into the lens surface in the first group, it is preferable that the negative refractive power becomes weaker or the positive refractive power becomes stronger as the distance from the optical axis increases. When an aspherical surface is used for the surface in the second lens unit or the third lens unit, it is desirable that the positive refractive power becomes weaker or the negative refractive power becomes stronger as the distance from the optical axis increases.

Regarding focusing, in the case of a lens system used for a particularly small image pickup device having a wide angle of view such as the zoom lens of the present invention, normal photographing is possible without a deep depth of field and focusing. is there. However, when shooting at a closer distance, it is necessary to perform focusing.

In the zoom lens of the present invention, the first group, the second group
Focusing can be performed by moving either the lens group or the third lens group, or by moving the entire lens system. Alternatively, focusing may be performed by moving the image sensor.

When the first lens group, the third lens group, or the entire lens system is moved to perform focusing on a short-distance object, it is moved to the object side. When focusing is performed by the second lens unit or the image pickup element, the focusing is performed by moving the near object to the image side.

In the focusing described above, when the focusing is performed by the first lens group, the variation of aberration is small and it is suitable for focusing at a closer distance. Further, when focusing is performed by the second lens unit, the zoom lens of the present invention is fixed during zooming and moves only during focusing, so that the movement of the second lens unit can be easily controlled. Third
When focusing is performed by a group, since the second group is originally movable, it is not necessary to increase the number of movable groups for focusing, and the configuration of the lens frame is simple.

Further, when focusing is performed on the entire lens system, or when focusing is performed by moving the image pickup element, it is suitable for focusing to a closer distance with less aberration variation, as in the case of the first group.

In the zoom lens of the present invention, a lens group for appropriately maintaining the angle of the principal ray incident on the image pickup element may be arranged on the image side of the third group.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the zoom lens of the present invention will be described based on the following examples.

Embodiments 1 to 7 of the zoom lens according to the present invention are constructed as shown in FIGS. 1 to 7, respectively, and have the following data. Example 1 f = 5.30 to 7.50 to 10.60, F / 2.80 to F / 2.95 to F / 3.38 2ω = 65.6 ° to 47.6 ° to 34.0 ° r ₁ = 27.5309 d ₁ = 1.0000 n ₁ = 1.77250 ν ₁ = 49.60 r ₂ = 9.8801 d ₂ = 3.3637 r ₃ = -25.9123 d ₃ = 1.8000 n ₂ = 1.84666 v ₂ = 23.78 r ₄ = -14.2547 d ₄ = 1.8347 r ₅ = -13.6706 d ₅ = 0.8000 n ₃ = 1.77250 v ₃ = 49.60 r _{6 = 164.1235 d 6 = D 1} ( _{variable) r 7 = 13.2813 d 7 =} 1.5000 n 4 = 1.51633 ν 4 = 64.15 r 8 = 852.8073 d 8 = 1.0000 r 9 = ∞ ( stop) d ₉ = D ₂ (variable) _{r 10 = 7.9437 d 10 = 4.5053} n 5 = 1.77250 ν 5 = 49.60 r 11 = -220.5945 d 11 = 1.2823 r 12 = -9.0138 d 12 = 0.7647 n 6 = 1.80518 ν 6 = 25.43 r 13 = 9.0897 d 13 = 0.5000 _{r 14 = -114.2945 d 14 = 2.0000} n 7 = 1.71300 ν 7 = 53.84 r 15 = -9.4098 d 15 = 0.1500 r 16 = 11.7232 d 16 = 1.9850 n 8 = 1.77250 ν 8 = 49.60 r 17 = -100.0855 d 17 = D ₃ (variable) r ₁₈ = _{d 18 = 2.1000 n 9 = 1.51633} ν 9 = 64.15 r 19 = ∞ d 19 = 4.2200 n 10 = 1.54771 ν 10 = 62.84 r 20 = ∞ d 20 = 0.5000 r 21 = ∞ d 21 = 0.8000 n 11 = 1.51633 ν 11 = 64.15 r ₂₂ = ∞ Change in interval during zooming and focusing (1) Focus on infinity W (∞) S (∞) T (∞) D ₁ 12.07834 4.79461 0.78844 D ₂ 6.76786 4.40801 1.60463 D ₃ 0.58747 2.94733 5.75070 (2 ) Focus on 200mm object distance by the 1st group W (200) S (200) T (200) D ₁ 12.65043 5.36671 1.36053 D ₂ 6.76786 4.40801 1.60463 D ₃ 0.58747 2.94733 5.75070 (3) Focus on the object distance 200mm by the 2nd group W (200) S (200) T (200) D ₁ 12.65050 5.41065 1.48236 d ₈ 0.42784 0.38396 0.30608 D ₂ 6.76786 4.40801 1.60463 D ₃ 0.58747 2.94733 5.75070 (4) Focus on 200mm object distance by the 3rd group W (200) S (200 ) T (200) D ₁ 12.07834 4.79461 0.78844 D ₂ 6. 63394 4.12494 0.91003 D ₃ 0.72140 3.23040 6.44530 (5) Focus on 200mm object distance W (200) S (200) T (200) D ₁ 12.07834 4.79461 0.78844 D ₂ 6.76786 4.40801 1.60463 D ₃ 0.72139 3.21868 6.30300 f ₁ / f _{3 = -0.876, f 2 / f 3} = 2.067, z 1 / z 3 = 2.187

Example 2 f = 5.30 to 8.81 to 14.00, F / 2.80 to F / 3.12 to F / 3.98 2ω = 65.4 ° to 40.6 ° to 25.6 ° r ₁ = 26.2466 d ₁ = 1.0000 n ₁ = 1.77250 ν ₁ = 49.60 r ₂ = 11.4355 d ₂ = 3.4105 r ₃ = -42.8638 d ₃ = 2.2000 n ₂ = 1.84666 ν ₂ = 23.78 r ₄ = -18.1946 d ₄ = 2.1602 r ₅ = -15.5545 d ₅ = 0.8000 n ₃ = 1.77250 ν ₃ = 49.60 r ₆ = 61.8681 d ₆ = D ₁ (variable) r ₇ = 15.1195 d ₇ = 1.5000 n ₄ = 1.51633 ν ₄ = 64.15 r ₈ = 98.3415 d ₈ = 1.0000 r ₉ = ∞ (aperture) d ₉ = D _{2 (variable) r 10 = 7.4815 d 10 =} 4.3945 n 5 = 1.77250 ν 5 = 49.60 r 11 = -187.2925 d 11 = 1.1445 r 12 = -10.2899 d 12 = 0.9134 n 6 = 1.80518 ν 6 = 25.43 r 13 = 7.7794 d ₁₃ = 0.5000 r ₁₄ = 49.9858 d ₁₄ = 2.0876 n ₇ = 1.78800 ν ₇ = 47.38 r ₁₅ = -11.5386 d ₁₅ = 0.1500 r ₁₆ = 10.5848 d ₁₆ = 2.0207 n ₈ = 1.80440 ν ₈ = 39.58 r ₁₇ = 28.7489 d ₁₇ = D ₃ (Variable ) R ₁₈ = ∞ d ₁₈ = 2.1000 n ₉ = 1.51633 ν ₉ = 64.15 r ₁₉ = ∞ d ₁₉ = 4.2200 n ₁₀ = 1.54771 ν ₁₀ = 62.84 r ₂₀ = ∞ d ₂₀ = 0.5000 r ₂₁ = ∞ d ₂₁ = 0.8000 n ₁₁ = 1.51633 ν ₁₁ = 64.15 r ₂₂ = ∞ Change in interval during zooming and focusing (1) Focus on infinity W (∞) S (∞) T (∞) D ₁ 16.15166 4.99976 0.57138 D ₂ 8.36365 5.14522 1.14141 D ₃ 0.59308 3.81151 7.81532 (2) Focus on 200mm object distance by the 1st group W (200) S (200) T (200) D ₁ 16.90469 5.75279 1.32442 D ₂ 8.36365 5.14522 1.14141 D ₃ 0.59308 3.81151 7.81532 (3) Object by the 2nd group Focus on a distance of 200mm W (200) S (200) T (200) D ₁ 16.90994 5.90087 1.62162 D ₂ 7.60536 4.24410 0.09117 D ₃ 0.59308 3.81151 7.81532 (4) Focus on a 400mm object distance by the 3rd group W (400) S (400) ) T (400) D ₁ 16.15166 4.99976 1.57138 D ₂ 8.29532 4.93640 0 .31633 D ₃ 0.66141 4.02033 8.64039 (5) Focus on the object distance of 200mm as a whole W (200) S (200) T (200) D ₁ 16.15166 4.99976 0.57138 D ₂ 8.36365 5.14522 1.14141 D ₃ 0.72574 4.18565 8.79395 f ₁ / f ₃ = _{-0.978, f 2 / f 3 =} 2.633, z 1 / z 3 = 2.157

Example 3 f = 5.30-9.40-15.90, F / 2.80-F / 3.14-F / 4.22 2ω = 65.4 ° -38.0 ° -22.6 ° r ₁ = 20.8050 d ₁ = 1.0000 n ₁ = 1.77250 ν ₁ = 49.60 r ₂ = 11.7467 d ₂ = 4.3798 r ₃ = -44.6045 d ₃ = 2.4000 n ₂ = 1.84666 ν ₂ = 23.78 r ₄ = -20.4655 d ₄ = 2.3741 r ₅ = -16.9197 d ₅ = 0.7804 n ₃ = 1.72916 ν ₃ = 54.68 r ₆ = 34.9059 d ₆ = D ₁ (variable) r ₇ = 15.1770 d ₇ = 1.5000 n ₄ = 1.51633 ν ₄ = 64.15 r ₈ = 76.0260 d ₈ = 1.0000 r ₉ = ∞ (aperture) d ₉ = D _{2 (variable) r 10 = 7.1143 d 10 =} 4.3052 n 5 = 1.77250 ν 5 = 49.60 r 11 = -421.0050 d 11 = 1.0210 r 12 = -10.8207 d 12 = 0.8865 n 6 = 1.80518 ν 6 = 25.43 r 13 = 7.1000 d _{13 = 0.5000 r 14 = 28.4383 d} 14 = 2.1010 n 7 = 1.79952 ν 7 = 42.24 r 15 = -14.4062 d 15 = 0.1500 r 16 = 11.9577 d 16 = 1.5000 n 8 = 1.80440 ν 8 = 39.58 r 17 = 34.7468 d 17 = D ₃ (Variable ) R ₁₈ = ∞ d ₁₈ = 2.1000 n ₉ = 1.51633 ν ₉ = 64.15 r ₁₉ = ∞ d ₁₉ = 4.2200 n ₁₀ = 1.54771 ν ₁₀ = 62.84 r ₂₀ = ∞ d ₂₀ = 0.5000 r ₂₁ = ∞ d ₂₁ = 0.8000 n ₁₁ = 1.51633 ν ₁₁ = 64.15 r ₂₂ = ∞ Change in interval during zooming and focusing (1) Focus on infinity W (∞) S (∞) T (∞) D ₁ 19.42093 5.70565 0.87370 D ₂ 10.50209 6.65718 1.65743 D ₃ 1.06217 4.90709 9.90683 (2) Focus on object distance 200mm by the first group W (200) S (200) T (200) D ₁ 20.23594 6.52067 1.68872 D ₂ 10.50209 6.65718 1.65743 D ₃ 1.06217 4.90709 9.90683 (3) Object by the second group Focus on a distance of 200mm W (200) S (200) T (200) D ₁ 20.23720 6.68872 2.03081 D ₂ 9.68582 5.67410 0.50032 D ₃ 1.06217 4.90709 9.90683 (4) Focus on a 400mm object distance by the third group W (400) S (400) ) T (400) D ₁ 19.42093 5.70565 0.87370 D ₂ 10.43420 6.4183 9 0.33492 D ₃ 1.13006 5.14587 11.22934 (5) Focus on the object distance of 200mm as a whole W (200) S (200) T (200) D ₁ 19.42093 5.70565 0.87370 D ₂ 10.50209 6.65718 1.65743 D ₃ 1.19346 5.32971 11.17041 f ₁ / f ₃ = _{-0.962, f 2 / f 3 =} 2.623, z 1 / z 3 = 2.097

Example 4 f = 5.30-7.50-10.60, F / 2.00-F / 2.08-F / 2.342 2ω = 66.6 ° -48.0 ° -34.2 ° r ₁ = 23.2236 d ₁ = 0.9755 n ₁ = 1.72916 ν ₁ = 54.68 r ₂ = 10.445 d ₂ = 3.7221 r ₃ = -21.5553 d ₃ = 1.8000 n ₂ = 1.84666 ν ₂ = 23.78 r ₄ = 14.3880 d ₄ = 2.2041 r ₅ = 12.2815 d ₅ ＝ 0.7804 n ₃ = 1.72916 ν ₃ = 54.68 r ₆ = -540.9631 d ₆ = D ₁ (variable) r ₇ = 17.2353 (aspherical surface) d ₇ = 1.5000 n ₄ = 1.51633 ν ₄ = 64.15 r ₈ = -72.9255 d ₈ = 1.0000 r ₉ = ∞ (aperture) ) d ₉ = D _{2 (variable) r 10 = 9.1212 d 10 =} 4.4650 n 5 = 1.77250 ν 5 = 49.60 r 11 = -145.5056 d 11 = 1.2299 r 12 = -12.3306 d 12 = 1.4032 n 6 = 1.80518 ν 6 = 25.43 r ₁₃ = 9.5406 d ₁₃ = 0.7000 r ₁₄ = 64.5503 d ₁₄ = 2.0000 n ₇ = 1.71300 ν ₇ = 53.84 r ₁₅ = -11.9863 d ₁₅ = 0.1500 r ₁₆ = 11.3326 d ₁₆ = 1.9850 n ₈ = 1.77250 ν ₈ = 49.60 r ₁₇ = 1436.3387 d _{1 7} = D ₃ (variable) r ₁₈ = ∞ d ₁₈ = 2.1000 n ₉ = 1.51633 ν ₉ = 64.15 r ₁₉ = ∞ d ₁₉ = 4.2200 n ₁₀ = 1.54771 ν ₁₀ = 62.84 r ₂₀ = ∞ d ₂₀ = 0.5000 r ₂₁ = ∞ d ₂₁ = 0.8000 n ₁₁ = 1.51633 ν ₁₁ ＝ 64.15 r ₂₂ ＝ ∞ aspherical surface coefficient A ₄ = -1.8095 × 10 ^-5 , A ₆ = -1.8987 × 10 ^-6 , A ₈ = 0 Interval during zooming focusing Change (1) Focus on infinity W (∞) S (∞) T (∞) D ₁ 13.21651 5.02630 0.37129 D ₂ 6.28697 4.11904 1.50848 D ₃ 0.47009 2.63802 5.24858 (2) Focus on 200 mm object distance W ( 200) S (200) T (200) D ₁ 13.90855 5.71835 1.06334 D ₂ 6.28697 4.11904 1.50848 D ₃ 0.47009 2.63802 5.24858 f ₁ / f ₃ = -0.980, f ₂ / f ₃ = 2.177, z ₁ / z ₃ = 2.688

Example 5 f = 5.30-9.40-15.90, F / 2.80-F / 3.15-F / 15.90 2ω = 65.2 ° -38.0 ° -22.6 ° r ₁ = 61.8634 d ₁ = 1.0190 n ₁ = 1.80610 ν ₁ = 40.95 r ₂ = 1.2743 d ₂ = 4.3482 r ₃ = -52.9723 d ₃ = 2.3461 n ₂ = 1.80518 ν ₂ = 25.43 r ₄ -15.3545 d ₄ = 2.0572 r ₅ = -16.9002 d ₅ = 0.7804 n ₃ = 1.72916 ν ₃ = 54.68 r ₆ = 72.6645 d ₆ = D ₁ (variable) r ₇ = 12.8743 d ₇ = 1.5862 n ₄ = 1.60342 ν ₄ = 38.01 r ₈ = 18.4263 d ₈ = 1.0000 r ₉ = ∞ (aperture) d ₉ = D ₂ (variable) r ₁₀ = 6.8508 _{(aspherical) d 10 = 3.8710 n 5 =} 1.67790 ν 5 = 55.33 r 11 = -39.4987 d 11 = 0.9132 r 12 = -14.1333 d 12 = 0.8000 n 6 = 1.80518 ν 6 = 25.43 r ₁₃ = 7.3195 d ₁₃ = 0.6000 r ₁₄ = 25.7582 d ₁₄ = 2.1087 n ₇ = 1.80610 ν ₇ = 40.95 r ₁₅ = 14.9625 d ₁₅ = 0.1500 r ₁₆ = 17.0965 d ₁₆ = 1.5351 n ₈ = 1.84666 ν ₈ = 23.78 r ₁₇ = 30.0061 d ₁₇ = D ₃ (variable) r ₁₈ = ∞ d ₁₈ = 2.1000 n ₉ = 1.51633 ν ₉ = 64.15 r ₁₉ = ∞ d ₁₉ = 4.2200 n ₁₀ = 1.54771 ν ₁₀ = 62.84 r ₂₀ = ∞ d ₂₀ = 0.5000 r ₂₁ = ∞ d ₂₁ = 0.8000 n ₁₁ = 1.51633 ν ₁₁ = 64.15 r ₂₂ = ∞ Aspherical coefficient A ₄ = -1.2853 × 10 ^-4 , A ₆ = -1.2027 × 10 ^-6 , A ₈ = 0 Change in spacing during zooming and focusing (1) Focus on infinity W (∞) S (∞) T (∞) D ₁ 16.67641 4.43634 1.10509 D ₂ 12.06841 7.83274 1.69794 D ₃ 1.14690 5.38256 11.24737 (2) Focus on 200mm object distance by the first group W (200) S (200) T (200) D ₁ 17.42330 5.18323 1.85198 D ₂ 12.06841 7.83274 1.96794 D ₃ 1.14690 5.38256 11.24737 f ₁ / f ₃ = -0.904, f ₂ / f ₃ = 4.559, z ₁ / z ₃ = 1.542

Example 6 f = 5.00 to 8.87 to 15.00, F / 2.80 to F / 3.15 to F / 4.48 2ω = 68.2 ° to 40.0 ° to 23.8 ° r ₁ = 48.6392 d ₁ = 1.0190 n ₁ = 1.80610 ν ₁ = 40.95 r ₂ = 10.0851 d ₂ = 4.3688 r ₃ = -99.3135 d ₃ = 2.3461 n ₂ = 1.80518 ν ₂ = 25.43 r ₄ = -17.0714 (aspherical surface) d ₄ = 1.8681 r ₅ = -21.4523 d ₅ = 0.7804 n ₃ = 1.72916 ν ₃ = 54.68 r ₆ ＝ 30.9086 d ₆ = D ₁ (variable) r ₇ = ∞ (aperture) d ₇ = 1.0000 r ₈ = 13.8366 d ₈ = 1.6000 n ₄ = 1.60342 ν ₄ = 38.01 r ₉ = 23.5407 d ₉ = D ₂ (variable) r ₁₀ = 7.0598 (aspherical surface) d ₁₀ = 3.8321 n ₅ = 1.67790 ν ₅ = 55.33 r ₁₁ = -34.8520 d ₁₁ = 0.8916 r ₁₂ = -14.0191 d ₁₂ = 0.8000 n ₆ = 1.80518 ν _{6 = 25.43 r 13 = 7.8208 d} 13 = 0.6000 r 14 = 36.7107 d 14 = 2.1087 n 7 = 1.80610 ν 7 = 40.95 r 15 = -12.8718 d 15 = 0.1500 r 16 = 23.1457 d 16 = 1.5351 n 8 = 1.84666 ν 8 = 23.78 r ₁₇ = 45.58 57 d ₁₇ = D ₃ (variable) r ₁₈ = ∞ d ₁₈ = 2.1000 n ₉ = 1.51633 ν ₉ = 64.15 r ₁₉ = ∞ d ₁₉ = 4.2200 n ₁₀ = 1.54771 ν ₁₀ = 62.84 r ₂₀ = ∞ d ₂₀ = 0.5000 r ₂₁ = ∞ d ₂₁ = 0.8000 n ₁₁ = 1.51633 ν ₁₁ = 64.15 r ₂₂ = ∞ Aspheric coefficient (4th surface) A ₄ = -1.6838 × 10 ^-5 , A ₆ = -1.1392 × 10 ^-8 , A ₈ = 0 (10th surface) A ₄ = -1.4671 × 10 ^-4 , A ₆ = -7.2438 × 10 ^-7 , A ₈ = 0 Change in interval during zooming and focusing (1) Focus on infinity W (∞) S (∞) T (∞) D ₁ 15.81215 4.28049 1.13735 D ₂ 12.27706 7.88072 1.98046 D ₃ 1.11985 5.51619 11.41645 (2) Focus on object distance 200mm by the first group W (200) S (200) T (200) D ₁ 16.40786 4.87619 _{1.73305 D 2 12.27706 7.88072 1.98046 D 3} 1.11985 5.51619 11.41645 f 1 / f 3 = -0.799, f 2 / f 3 = 3.707, z 1 / z 3 = 1.425

Example 7 f = 5.30-9.31-15.82, F / 2.80-F / 3.16-F / 4.42 2ω = 63.6 ° -38.0 ° -22.6 ° r ₁ = 31.9296 d ₁ = 1.0000 n ₁ = 1.77250 ν ₁ = 49.60 r ₂ = 8.9082 d ₂ = 4.4775 r ₃ = -40.8583 d ₃ = 2.3461 n ₂ = 1.80518 v ₂ = 25.43 r ₄ = -14.4493 d ₄ = 0.5357 r ₅ = -30.5624 d ₅ = 0.8000 n ₃ = 1.77250 v ₃ = 49.60 r ₆ = 26.6917 d ₆ = D ₁ (variable) r ₇ = ∞ (aperture) d ₇ = 1.0000 r ₈ = 11.398 598 d ₈ = 1.5131 n ₄ = 1.51633 ν ₄ = 64.15 r ₉ = 20.6578 d ₉ = D ₂ (variable) r ₁₀ = 6.3948 _{(aspherical) d 10 = 3.7886 n 5 =} 1.67790 ν 5 = 55.33 r 11 = -24.5806 d 11 = 0.6892 r 12 = -12.0505 d 12 = 0.7611 n 6 = 1.71736 ν 6 = 29.51 r ₁₃ = 6.1339 d ₁₃ = 0.8000 r ₁₄ = 23.3548 d ₁₄ = 2.0851 n ₇ = 1.78590 ν ₇ = 44.19 r ₁₅ = -13.4877 d ₁₅ = D ₃ (variable) r ₁₆ = ∞ d ₁₆ = 2.1000 n ₈ = 1.51633 ν ₈ = 64.15 r ₁₇ = ∞ d _{17 4.2200 n 9 = 1.54771 ν 9 =} 62.84 r 18 = ∞ d 18 = 0.5000 r 19 = ∞ d 19 = 0.8000 n 10 = 1.51633 ν 10 = 64.15 r 20 = ∞ aspherical coefficients A ₄ = -1.9940 × 10 ^-4, A ₆ = -1.3485 × 10 ^-6 , A ₈ = 0 Change in interval during zooming and focusing (1) Focus on infinity W (∞) S (∞) T (∞) D ₁ 16.39993 4.68566 1.09181 D ₂ 12.69294 8.26486 2.26210 D ₃ 1.29383 5.72192 11.72468 (2) Focus on 200mm object distance by the 1st group W (200) S (200) T (200) D ₁ 17.04737 5.33310 1.73925 D ₂ 12.69294 8.26486 2.26210 D ₃ 1.29383 5.72192 11.72468 f ₁ / f _{3 = -0.798, f 2 / f 3} = 3.140, these examples z ₁ / z ₃ = 1.468 are more becomes a negative first group and the second group of positive and positive in the third group, as described in the data Thus, the distances D ₁ , D ₂ and D ₃ change due to the magnification change.

The configurations of the first, second, and third groups and the arrangement positions of the diaphragms in each embodiment are as follows.

In each of Examples 1 to 5, the first lens group has, in order from the object side, a negative lens having a concave surface facing the image side, a positive lens having a convex surface facing the image side, and a concave surface facing the object side. The second group consists of one positive lens, the third group consists of four lenses in order from the object side: the positive lens, the negative lens, the positive lens and the positive lens, and the aperture is the second group. It is fixedly arranged on the image side of.

The sixth embodiment has the same construction as the first to fifth embodiments except that the diaphragm is fixedly arranged on the object side of the second lens unit.

The seventh embodiment differs from the other embodiments in that the third lens group is composed of three lenses, a positive lens, a negative lens and a positive lens, in order from the object side. The diaphragm is fixedly arranged on the object side of the second lens group, as in the sixth embodiment.

In the above embodiment, the surface r _{7 of} the fourth embodiment,
Surface r _{10 of} Example 5, surfaces r ₄ and r _{10 of} Example 6, Example 7
Each of the surfaces r ₁₀ is an aspherical surface represented by the following formula when the optical axis direction is the x axis and the direction perpendicular to the optical axis is the y axis.

However, r is the radius of curvature at the apex of the aspherical surface, K is the conic constant, and A ₄ , A ₆ , A ₈ , ... Are 4 respectively.
Next, sixth, eighth, ... Aspherical coefficients.

Further, the change in the interval at the time of zooming and focusing in each embodiment is as shown in the data.
(∞), S (∞), and T (∞) are the variable intervals at the wide-angle end, the intermediate focal length, and the telephoto end when focusing on infinity, and W (20
0), S (200), and T (200) are variable distances at the wide-angle end, intermediate focal length, and telephoto end when focusing on an object with an object distance of 200 mm, W (400), S (400), T (400) ) Is 4 each
The variable distances at the wide-angle end, the intermediate focal length, and the telephoto end when focusing on an object of 00 mm are shown.

In the data, Examples 1, 2, and 3 show the intervals when the first lens group, the second lens group, the third lens group, and the entire lens system are moved for focusing. At the time of focusing by the second lens unit in the first embodiment, the diaphragm is fixed, so that the distance d ₈ between the second lens unit and the diaphragm changes.
In each of the second and third embodiments, when the second lens group is moved toward the diaphragm for focusing by the second lens group, the second lens group hits the diaphragm so that the second lens group and the diaphragm are moved together. Focusing. Therefore, during focusing by the second lens unit, the distance d ₈ between the most image-side surface of the second lens unit and the diaphragm is unchanged, and the surface distance d ₉ (D ₂ ) between the diaphragm and the object side of the third lens unit is Change.

The data of Examples 4 to 7 are also shown in Examples 1, 2, and
As in the case of 3, any of the first group, the second group, the third group, and focusing by the entire lens system is possible.

In the aberration charts of the respective examples, the upper row shows the wide end,
The interruption is at the middle focal length, and the lower row is at the telephoto end.

The zoom lens of the present invention can achieve the objects not only in the claims but also in the following items.

(1) In the lens system according to claim 1, 2 or 3, the third lens group comprises three lenses, in order from the object side, a positive lens, a negative lens and a positive lens, or
A zoom lens consisting of four lenses: a positive lens, a negative lens, a positive lens, and a positive lens.

(2) In the lens system described in claim 1, 2 or 3 of the claims or in (1), the following conditions (1), (2) and (3) are satisfied. Zoom lens to do.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3) 0.5 <Z ₁ / Z ₃ <4 ( 3) A zoom lens satisfying the following conditions, which is the lens system described in claim 1, 2 or 3 or (1) above.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2-1) 1.8 <f ₂ / f ₃ <9 (3) 0.5 <Z ₁ / Z ₃ < 4 (4) A zoom lens which satisfies the following conditions in the lens system described in claim 1, 2 or 3 or (1) above.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2-2) 1.6 <f ₂ / f ₃ <7 (3) 0.5 <Z ₁ / Z ₃ < 4 (5) A zoom lens system according to claim 1, 2 or 3 of the claims or (1) above, which satisfies the following conditions.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2-3) 1.8 <f ₂ / f ₃ <7 (3) 0.5 <Z ₁ / Z ₃ < 4 (6) A zoom lens system according to claim 1, 2 or 3 of the claims or (1) above, which satisfies the following conditions.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2-4) 2 <f ₂ / f ₃ <9 (3) 0.5 <Z ₁ / Z ₃ <4 ( 7) A zoom lens satisfying the following conditions in the lens system described in claim 1, 2 or 3 or (1) above.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2-5) 1.6 <f ₂ / f ₃ <5 (3) 0.5 <Z ₁ / Z ₃ < 4 (8) A zoom lens satisfying the following conditions in the lens system according to claim 1, 2 or 3 or (1) above.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2-6) 2 <f ₂ / f ₃ <5 (3) 0.5 <Z ₁ / Z ₃ <4 ( 9) A zoom lens system according to claim 1, 2 or 3 of the claims or (1) above, which satisfies the following conditions.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2-7) 2 <f ₂ / f ₃ <7 (3) 0.5 <Z ₁ / Z ₃ <4 ( 10) A zoom lens system according to any one of claims 1, 2 or 3 or (1) above, which satisfies the following conditions.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2-8) 1.8 <f ₂ / f ₃ <5 (3) 0.5 <Z ₁ / Z ₃ < 4 (11) A lens system according to claim 1, 2 or 3 of the claims or (1) above, wherein the zoom lens satisfies the following conditions.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3-1) 0.8 <Z ₁ / Z ₃ < 4 (12) A lens system according to claim 1, 2 or 3 of the claims or (1) above, wherein the zoom lens satisfies the following conditions.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3-2) 0.5 <Z ₁ / Z ₃ < 3.5 (13) A zoom lens which satisfies the following conditions in the lens system described in claim 1, 2 or 3 or (1) above.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3-3) 0.8 <Z ₁ / Z ₃ < 3.5 (14) A lens system according to claim 1, 2 or 3 of the claims or (1) above, wherein the zoom lens satisfies the following conditions.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3-4) 1.2 <Z ₁ / Z ₃ < 4 (15) A zoom lens which satisfies the following conditions in the lens system described in claim 1, 2 or 3 or (1) above.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3-5) 0.5 <Z ₁ / Z ₃ < 3 (16) A zoom lens which satisfies the following conditions in the lens system described in claim 1, 2 or 3 or (1) above.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3-6) 1.2 <Z ₁ / Z ₃ < 3 (17) A lens system according to claim 1, 2 or 3 or (1) above, wherein the zoom lens satisfies the following conditions.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3-7) 1.2 <Z ₁ / Z ₃ < 3.5 (18) A zoom lens which satisfies the following conditions in the lens system according to claim 1, 2 or 3 or (1) above.

(1) −1.5 <f ₁ / f ₃ <−0.4 (2) 1.6 <f ₂ / f ₃ <9 (3-8) 0.8 <Z ₁ / Z ₃ < Three

[0071]

According to the present invention, a video having a three-group structure of negative, positive, and positive, an angle of view of about 65 °, a high magnification ratio of about 2 to 3, and a simple lens frame structure can be formed. It is possible to realize a wide-angle zoom lens suitable for a camera.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a sixth embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a seventh embodiment of the present invention.

8 is an aberration curve diagram when focusing on an object at infinity in Example 1. FIG.

FIG. 9 is an aberration curve diagram when a 200 mm object is focused by the first group in the first example.

FIG. 10 is an aberration curve diagram when an object of 200 mm is focused by the second group of the first embodiment.

FIG. 11 is an aberration curve diagram when a 200 mm object is focused by the third group in the first example.

FIG. 12 is an aberration curve diagram when an object of 200 mm is focused by the entire lens system of Example 1.

FIG. 13 is an aberration curve diagram of Example 2 when focusing on an object at infinity.

FIG. 14 is an aberration curve diagram when an object of 200 mm is focused by the first group of Example 2.

FIG. 15 is an aberration curve diagram when a 200 mm object is focused by the second lens group of the second embodiment.

FIG. 16 is an aberration curve diagram when an object of 400 mm is focused by the third lens group of the second embodiment.

FIG. 17 is an aberration curve diagram when an object of 200 mm is focused by the entire lens system of Example 2.

FIG. 18 is an aberration curve diagram of Example 3 when focusing on an object at infinity.

FIG. 19 is an aberration curve diagram when a 200 mm object is focused by the first group in Example 3.

FIG. 20 is an aberration curve diagram when a 200 mm object is focused by the second lens group of the third embodiment.

FIG. 21 is an aberration curve diagram when focusing on an object of 400 mm by the third group of the example 3.

FIG. 22 is an aberration curve diagram when an object of 200 mm is focused by the entire lens system of Example 3.

23 is an aberration curve diagram when focusing on an object at infinity according to Example 4. FIG.

FIG. 24 is an aberration curve diagram of Example 5 when focusing on an object at infinity.

FIG. 25 is an aberration curve diagram of Example 6 when focusing on an object at infinity.

26 is an aberration curve diagram when focusing on an object at infinity according to Example 7. FIG.

Claims (3)

[Claims] 1. A first lens having a negative refractive power in order from the object side.
It consists of a group, a second group having a positive refracting power, and a third group having a positive refracting power. When zooming, the first group is positioned closer to the image side at the telephoto end than at the wide-angle end. The second lens group is fixed, the third lens group moves from the image side to the object side from the wide-angle end to the telephoto end, and the aperture stop is fixed on the optical axis between the first lens group and the third lens group. Zoom lens. 2. The first group comprises, in order from the object side, a negative lens having a concave surface facing the image side, a positive lens having a convex surface facing the image side, and a negative lens having a concave surface facing the object side. Zoom lens. 3. The zoom lens according to claim 1, wherein the second lens group is composed of only one positive lens.