JPH06300967A - Zoom lens - Google Patents

Abstract

PURPOSE:To provide an inner focus type zoom lens which is suitable for a small-sized video camera and a still video camera and has extremely high optical performance from an infinite distance point to a short distance point. CONSTITUTION:The inner focus type zoom lens which has a high power variation ratio consists of a 1st lens group G1 which has positive refracting power, a 2nd lens group G2 which moves for power varying operation and has negative refracting power, a 3rd lens group G3 which is fixed at the time of fixation and has positive refracting power, and a 4th lens group G4 which corrects a shift in image position owing to the power variation and has positive refracting power; and the 2nd lens group G2 consists of a negative 1st group and a negative 2nd group, which serves as a focusing group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high zoom ratio inner focus type zoom lens suitable for video cameras and still video cameras.

[0002]

2. Description of the Related Art In a camera using a solid-state image pickup device, a zoom lens having an extremely large zoom ratio is generally used as a photographing lens, and since the imager is relatively small, it is bright and A high performance optical system is required.

As an optical system satisfying such requirements,
In order from the object side, the first lens group having a positive refractive power, the second lens group having a variable power and a negative refractive power, and the negative lens group having a function of keeping the image surface constant during zooming. The third lens group having a refractive power of 4 and the fourth lens group having a positive refractive power having an image forming action.
A four-group zoom lens including a lens group is known.
In this lens system, it is necessary to secure an interval in which the third lens group moves, and the fourth lens group connects this luminous flux with the front group that makes the divergent luminous flux emitted from the third lens group substantially parallel. Since it is composed of the rear group to be imaged, the overall length is long and it is difficult to achieve the miniaturization required for video cameras in recent years. When the first lens group is further extended to the object side for focusing, the number of movable groups becomes three, which complicates the mechanism and requires a large driving force to extend the first lens group having a large lens outer diameter. There is a problem that the power is large.

Therefore, recently, in order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power having a zooming effect, and the positive lens having a positive refractive power when zooming. A fixed third lens group and a fourth lens group having a positive refracting power and having a function of correcting a change in image plane position due to zooming, are provided. By focusing the fourth lens group toward the object side, focusing is performed. The mainstream is the 4-group zoom lens.

As a conventional example of a four-group zoom lens of the type described above, Japanese Patent Laid-Open Nos. 62-178917 and 62-1987 are known.
Lens systems described in Japanese Patent Laid-Open No. 215225 and Japanese Patent Laid-Open No. 63-123009 are known.

[0006]

Generally, in the focusing system of a lens system, it is an important requirement that the driving mechanism be simple and that the lens system be made compact. In a camera using a solid-state image pickup element, the pitch width of the pixels has become small particularly due to the recent increase in the number of pixels of the solid-state image pickup element, and thus a lens system having an extremely high resolution is required. Moreover, in these cameras, it is necessary to maintain high optical performance from an object point at infinity to an object point at a short distance, and it is extremely important to adopt a focusing method that causes little deterioration in optical performance in addition to the problem of the drive mechanism. .

From the above points, the above-mentioned conventional zoom lens adopts the inner focus method mainly for making the lens system compact and for reducing the load on the driving mechanism, and from an object point at infinity. It cannot be said that sufficiently high optical performance is maintained up to a short-distance object point. That is,
In these conventional examples, when focusing is performed using the fourth lens group, the fourth lens group has an image forming action as well as a function of correcting a change in the image plane due to zooming. Field curvature especially at the telephoto end,
Astigmatism varies greatly, and it is difficult to maintain high optical performance when focusing on a short-distance object point.

The object of the present invention is suitable for small-sized video cameras and still video cameras, and by selecting and configuring the focusing lens group appropriately, from an object point at infinity to an object point at a short distance. An object of the present invention is to provide an inner-focus type zoom lens having a high zoom ratio and extremely high optical performance.

[0009]

The zoom lens according to the present invention comprises, in order from the object side, a first lens group G having a positive refractive power.
₁ , a second lens group G ₂ having a negative refractive power that moves along the optical axis and mainly performs a zooming action, and a third lens group G ₃ having a positive refractive power that is fixed during zooming. And a fourth lens group G ₄ having a positive refracting power and having a function of correcting a change in image plane position due to zooming, and the second lens group G ₂ is
The lens system is composed of a first group G ₂₁ having a negative refracting power and a second group G ₂₂ having a negative refracting power which is a focusing group in order from the object side.

In a four-group zoom lens consisting of four lens groups of positive, negative, positive, and positive, the fourth lens group has a refractive power distribution such that the first lens group to the third lens group are almost afocal. A lens system is generally used to form an image by a group. That is, in this four-group zoom lens, the axial light flux that is incident on the fourth lens group is substantially parallel to the optical axis, and particularly if focusing is performed by moving the fourth lens group or a part of the lens components thereof. The fluctuation of spherical aberration can be kept small. However, as described above, the fourth lens group has a strong refracting power because it has an image-forming action, and therefore, in order to obtain high optical performance, high-order spherical aberration is so large that it cannot be ignored. become. Also, the first
In order to prevent the diameter of the lens group from becoming large, the diaphragm is usually fixed on the object side of the third lens group or in the third lens group, or is arranged between the second lens group and the third lens group. Then, it is moved along with the change in magnification. Therefore, the fourth
In the lens group, the off-axis ray height becomes high, the off-axis aberrations, especially the curvature of field largely fluctuate, the image planes do not match at the center and the periphery of the screen, and the image is deteriorated. Therefore, it is not preferable to perform focusing by extending the lens component of the fourth lens unit or a part thereof.

On the other hand, in the four-group zoom lens, since the incident convergent light flux is emitted as a divergent light flux in the second lens group, there is a position in the second lens group where the axial light flux is parallel to the optical axis. This second lens group is divided into a first group G ₂₁ having a negative refracting power and a second group G ₂₂ having a negative refracting power,
From the lens group to the first group G ₂₁ of this second lens group, the configuration is close to afocal, and the second group G of the second lens group G
_{Even if 22} is moved and focusing is performed, the fluctuation of spherical aberration can be kept small. For this reason, in the present invention, the second lens group is the first group G ₂₁ and the second group G ₂₁ .
_The zoom lens is composed of ₂₂ and a four-group zoom lens having the above-mentioned configuration.

Further, in the present invention, the second lens group G _{2 for} zooming comes closest to the first lens group G ₁ at the wide-angle end and monotonically moves to the image side to zoom to the telephoto side. , Since it is closest to the third lens group G ₃ side at the telephoto end, the off-axis ray height in the second lens group G ₂₂ of the second lens group G ₂ is kept low at the telephoto end where the amount of lens movement during focusing is large. This makes it possible to maintain extremely high optical performance from an object point at infinity to an object point at a close range.

In the zoom lens of the present invention having the above-mentioned structure, the second lens group G ₂ can be maintained while maintaining higher optical performance.
In order to make it possible to perform focusing by the second group G ₂₂ of No. 2, it is desirable that the following condition (1) is satisfied. However, f ₂₂ is the focal length of the second lens group G ₂₂ (focusing group) of the second lens group G ₂ , and f _W and f _T are the focal lengths of the entire system at the wide-angle end and the telephoto end, respectively.

This condition (1) defines the refracting power of the second lens group G ₂₂ of the second lens group G ₂ , and if the lower limit of 0.50 of the condition (1) is exceeded, the amount of movement during focusing will be large. Since it is small, it is advantageous for downsizing of the lens system, but the aberration variation during focusing is large, and it becomes difficult to correct the variation of the field curvature particularly at the telephoto end. If the upper limit of 1.5 is exceeded, the amount of movement of the lens during focusing becomes large, and the first lens group G ₂₁ of the second lens group G ₂ and the second lens group G 2
It is necessary to increase the distance between the groups G ₂₂ and the lens system becomes large. Wherein in order to reduce the amount of movement of the second group G ₂₂ is, the refractive power of the first lens group G ₁ and second first group G ₂₁ of the lens group G ₂ must be in a large, thereby telephoto At the edge, coma changes during focusing, correction becomes difficult, and image quality deteriorates.

Further, in order to secure a sufficient spacing for focusing, it is desirable to satisfy the following condition (2).

(2) 0.3 <D / f _W <2.0 where D is the air space separating the first group G ₂₁ and the second group G ₂₂ with respect to the object point at infinity. .

If the lower limit of 0.3 of the condition (2) is exceeded, the lens may collide during focusing at the telephoto end, making it difficult to shorten the shortest shooting distance. On the contrary, by increasing the refracting power of the second lens group G ₂₂ , the moving distance during focusing is shortened, and if the lower limit of the condition (2) is exceeded, the refracting power of the second lens group G ₂₂ will be too strong. Aberration fluctuations are large, and field curvature especially at a telephoto end for a short-distance object point deteriorates. If the upper limit of 2.0 to condition (2) is exceeded, the size of the lens system will increase.

In order to achieve higher optical performance in the zoom lens of the present invention, the following condition (3),
It is desirable to satisfy (4).

(3) 0.5 <| f ₂₁ / f ₂₂ | <2.0 This is the combined focal length of the first lens group G ₁ and the first lens group G ₂₁ of the second lens group at that time.

If the lower limit of 0.50 of condition (3) is exceeded, the second
The refractive power of the group G ₂₂ is too small or the refractive power of the first group G ₂₁ is too large. In the former case, the movement amount during focusing is large and it is necessary to set a large distance between the first group G ₂₁ and the second group G _22. Occurs, and the lens system becomes large. In the latter case, the coma aberration varies greatly during focusing at the telephoto end, which makes correction difficult. If the upper limit of 2.00 to condition (3) is exceeded, the refractive power of the first lens group G ₂₁ will become weaker or the refractive power of the second lens group G ₂₂ will become stronger. In the former case, the first lens group G ₁ to In order to keep the first lens group G ₂₁ of the two lens groups substantially afocal, it is necessary to weaken the refractive power of the first lens group G ₁ and the lens system becomes large. Further, in the latter case, it is extremely difficult to keep the fluctuation of the field curvature small during focusing, which is not preferable.

The condition (4) is from the first lens group G ₁ to the second lens group G ₁ .
This is a condition for keeping the first lens group G ₂₁ to afocal. That is, the second lens group G ₂ moves for zooming, and for all focal lengths from the wide-angle end to the telephoto end, the first lens group G ₁ to the first lens group G ₂₁ of the second lens group G _21.
Cannot be strictly afocal. Therefore, in all conditions from the wide-angle end to the telephoto end,
In order to keep aberration fluctuations small during focusing, it is desirable to use a power arrangement close to afocal at the intermediate focal length, and the upper limit of condition (4) is 0.200.
When it exceeds, the aberration variation during focusing at the wide-angle end or the telephoto end becomes large.

[0023]

【Example】

Next, examples of the zoom lens of the present invention will be shown. Example 1 f = 9.072 ~25.555~71.985, F-number = 2.0 2ω = 49.42 ° ~18.34 ° ~6.44 ° r 1 = 129.3098 d 1 = 2.0000 n 1 = 1.83350 ν 1 = 21.00 r 2 = 75.4170 d 2 = 5.5147 n ₂ = 1.56907 ν ₂ ＝ 71.30 r ₃ ＝ 13256.1736 d ₃ ＝ 0.1000 r ₄ ＝ 56.2897 d ₄ ＝ 4.7842 n ₃ ＝ 1.43875 ν ₃ ＝ 94.97 r ₅ ＝ 191.8272 d ₅ ＝ 0.1000 r ₆ ＝ 35.7104 d ₆ ＝ 4.1662 n ₄ ＝ 1.43875 ν ₄ = 94.97 r ₇ ＝ 71.4223 d ₇ ＝ D ₁ (variable) r ₈ ＝ 50.0568 d ₈ ＝ 1.0000 n ₅ ＝ 1.69350 ν ₅ ＝ 53.23 r ₉ ＝ 14.8940 d ₉ ＝ 7.9097 r ₁₀ ＝ -89.3547 d ₁₀ ＝ 1.0000 _{n 6 = 1.61800 ν 6 = 63.38} r 11 = 27.1357 d 11 = 0.1000 r 12 = 20.4460 d 12 = 5.6166 n 7 = 1.84666 ν 7 = 23.78 r 13 = 104.2962 d 13 = 11.4113 r 14 = -19.6270 d 14 = 1.0000 n ₈ = 1.61800 ν ₈ = 63.38 r ₁₅ = 130.8148 d ₁₅ = D ₂ (variable) r ₁₆ = ∞ (aperture) d ₁₆ = 1.2000 r ₁₇ = -359.4837 d ₁₇ = 2.4901 n ₉ = 1.9680 ν ₉ = 5 6.49 r ₁₈ = -24.0590 d ₁₈ = 0.1000 r ₁₉ = 18.8897 d ₁₉ = 3.4201 n ₁₀ = 1.72916 ν ₁₀ = 54.68 r ₂₀ = 25.9306 d ₂₀ = 2.0069 r ₂₁ = -19.5418 d ₂₁ = 1.0000 n ₁₁ = 1.79850 ν ₁₁ = 22.60 r ₂₂ = -47.5334 d ₂₂ = D ₃ (variable) r ₂₃ = 48.3505 d ₂₃ = 2.8540 n ₁₂ = 1.61800 ν ₁₂ = 63.38 r ₂₄ = -26.3345 d ₂₄ = 0.1000 r ₂₅ = 24.7722 d ₂₅ = 7.4117 n ₁₃ = 1.61800 ν ₁₃ = 63.38 r ₂₆ = 27034.9871 d ₂₆ = 1.0310 r ₂₇ = -25.9760 d ₂₇ = 5.5065 n ₁₄ = 1.84666 ν ₁₄ = 23.78 r ₂₈ ＝ -105.5026 f 9.072 25.555 71.985 D ₁ 1.4000 19.6457 32.0743D ₂ 32.6407 14.3 ₃ 12.3962 8.0824 7.3732

Example 2 f = 9.037 to 25.504 to 71.976, F number = 2.0 2ω = 49.59 ° to 18.40 ° to 6.44 ° r ₁ = 112.9725 d ₁ = 2.0000 n ₁ = 1.83350 ν ₁ = 21.00 r ₂ = 69.3081 d ₂ = 5.0143 n ₂ = 1.56907 ν ₂ ＝ 71.30 r ₃ ＝ 1611.3510 d ₃ ＝ 0.1000 r ₄ ＝ 53.5093 d ₄ ＝ 4.3866 n ₃ ＝ 1.43875 ν ₃ ＝ 94.97 r ₅ ＝ 170.9122 d ₅ ＝ 0.1000 r ₆ ＝ 34.9391 d ₆ ＝ 3.8929 n ₄ = 1.43875 ν ₄ ＝ 94.97 r ₇ ＝ 65.2733 d ₇ ＝ D ₁ (variable) r ₈ ＝ 37.5527 d ₈ = 1.0000 n ₅ = 1.69350 ν ₅ ＝ 53.23 r ₉ = 13.9494 d ₉ ＝ 8.3951 r ₁₀ ＝ -70.5726 d ₁₀ = 1.0000 n ₆ = 1.61800 ν ₆ = 63.38 r ₁₁ = 27.4083 d ₁₁ = 0.1000 r ₁₂ = 19.9663 d ₁₂ = 3.4440 n ₇ = 1.84666 ν ₇ = 23.78 r ₁₃ = 94.4573 d ₁₃ = 11.3766 r ₁₄ = -20.0338 d _{14 = 1.0000 n 8 = 1.61800 ν 8} = 63.38 r 15 = 108.4270 d 15 = D 2 ( variable) r ₁₆ = ∞ _{(stop) d 16 = 1.0000 r 17 =} 316.3012 d 17 = 2.4717 n 9 = 1. 69680 v ₉ = 56.49 r ₁₈ = -24.7688 d ₁₈ = 0.1000 r ₁₉ = 17.6369 d ₁₉ = 1.7506 n ₁₀ = 1.72916 v ₁₀ = 54.68 r ₂₀ = 24.0242 d ₂₀ = 2.3278 r ₂₁ = -20.0035 d ₂₁ = 1.0000 n ₁₁ = 1.79850 ν ₁₁ = 22.60 r ₂₂ = -55.7041 d ₂₂ = D ₃ (variable) r ₂₃ = 48.6302 d ₂₃ = 2.8709 n ₁₂ = 1.61800 ν ₁₂ = 63.38 r ₂₄ = -25.4144 d ₂₄ = 0.1000 r ₂₅ = 24.6944 d ₂₅ = 6.2275 n ₁₃ = 1.61800 ν ₁₃ = 63.38 r ₂₆ = 218.4995 d ₂₆ = 1.4061 r ₂₇ = -24.6851 d ₂₇ = 1.8868 n ₁₄ = 1.84666 ν ₁₄ = 23.78 r ₂₈ = -76.8225 f 9.037 25.504 71.976 D ₁ 1.4000 19.3914 31.8214 D ₂ 32.3729 14.3814 1.9525 D ₃ 11.9577 7.8398 7.5484

Example 3 f = 9.138 to 25.640 to 71.945, F number = 2.0 2ω = 49.67 ° to 18.21 ° to 6.43 ° r ₁ = 89.0480 d ₁ = 2.0000 n ₁ = 1.83350 ν ₁ = 21.00 r ₂ = 58.2230 d ₂ ＝ 4.6996 n ₂ = 1.56907 ν ₂ ＝ 71.30 r ₃ ＝ 591.5769 d ₃ ＝ 0.1000 r ₄ ＝ 42.6939 d ₄ ＝ 4.5357 n ₃ ＝ 1.43875 ν ₃ ＝ 94.97 r ₅ ＝ 148.7546 d ₅ ＝ 0.1000 r ₆ ＝ 38.7877 d ₆ ＝ 3.8000 n ₄ = 1.43875 ν ₄ = 94.97 r ₇ = 64.8361 d ₇ = D ₁ (variable) r ₈ = 50.7062 d ₈ = 1.0000 n ₅ = 1.6000 ν ₅ = 57.33 r ₉ = 12.5835 d ₉ = 5.3756 r ₁₀ = 552.1288 d ₁₀ = 1.0000 n ₆ = 1.61800 ν ₆ ＝ 63.38 r ₁₁ ＝ 22.6455 d ₁₁ ＝ 0.4012 r ₁₂ = 16.1845 d ₁₂ ＝ 2.7621 n ₇ ＝ 1.84666 ν ₇ ＝ 23.78 r ₁₃ ＝ 43.3818 d ₁₃ ＝ 9.7468 r ₁₄ ＝ -18.7408 d ₁₄ ＝ 1.0000 n ₈ = 1.61800 ν ₈ = 63.38 r ₁₅ = 83.2316 d ₁₅ = D ₂ (variable) r ₁₆ = ∞ (aperture) d ₁₆ = 1.0000 r ₁₇ = -315.1456 d ₁₇ = 1.8286 n ₉ = 1.729 16 v ₉ = 54.68 r ₁₈ = -27.9059 d ₁₈ = 0.1000 r ₁₉ = 35.8537 d ₁₉ = 1.6647 n ₁₀ = 1.729 16 v ₁₀ = 54.68 r ₂₀ = -247.3353 d ₂₀ = 1.0000 r ₂₁ = -27.8570 d ₂₁ = 1.0000 n ₁₁ = 1.64769 ν ₁₁ ＝ 31.23 r ₂₂ ＝ 337.4035 d ₂₂ ＝ D ₃ (variable) r ₂₃ ＝ 151.4663 d ₂₃ = 1.0000 n ₁₂ ＝ 1.69895 ν ₁₂ ＝ 30.12 r ₂₄ = 18.7566 d ₂₄ ＝ 0.2781 r ₂₅ ＝ 19.4641 d ₂₅ ＝ 5.4081 n ₁₃ = 1.61800 ν ₁₃ = 63.38 r ₂₆ = -30.5119 d ₂₆ = 0.1000 r ₂₇ = 25.4942 d ₂₇ = 4.9085 n ₁₄ = 1.56907 ν ₁₄ = 71.30 r ₂₈ = 285.7212 f 9.138 25.640 71.945 D ₁ 1.4000 18.5749 30.0681 _{1 2} 3663 1.4000 D ₃ 13.2536 8.5489 8.1272

Example 4 f = 9.042 to 25.512 to 71.982, F number = 2.0 2ω = 49.88 ° to 18.33 ° to 6.43 ° r ₁ = 90.7404 d ₁ = 2.0000 n ₁ = 1.83350 ν ₁ = 21.00 r ₂ = 60.2218 d ₂ = 4.5180 n ₂ = 1.56907 ν ₂ ＝ 71.30 r ₃ ＝ 445.7069 d ₃ ＝ 0.1000 r ₄ ＝ 47.2419 d ₄ ＝ 3.9379 n ₃ ＝ 1.43875 ν ₃ ＝ 94.97 r ₅ ＝ 137.5940 d ₅ ＝ 0.1000 r ₆ ＝ 36.4518 d ₆ ＝ 3.8000 n ₄ = 1.43875 ν ₄ ＝ 94.97 r ₇ ＝ 67.1732 d ₇ ＝ D ₁ (variable) r ₈ ＝ 35.9651 d ₈ ＝ 1.0000 n ₅ ＝ 1.67000 ν ₅ ＝ 57.33 r ₉ = 13.2039 d ₉ ＝ 6.3289 r ₁₀ ＝ 19449.9779 d ₁₀ = 1.0000 n ₆ = 1.61800 ν ₆ = 63.38 r ₁₁ = 19.3089 d ₁₁ = 0.9021 r ₁₂ = 16.3430 d ₁₂ ＝ 2.7362 n ₇ = 1.84666 ν ₇ ＝ 23.78 r ₁₃ ＝ 41.8143 d ₁₃ ＝ 9.7972 r ₁₄ ＝ -17.8633 d ₁₄ ＝ 1.0000 n ₈ = 1.61800 ν ₈ = 63.38 r ₁₅ = 124.8346 d ₁₅ = D ₂ (variable) r ₁₆ = ∞ (aperture) d ₁₆ = 1.0000 r ₁₇ = -53.2949 d ₁₇ = 2.0000 n ₉ = 1.7 2916 ν ₉ = 54.68 r ₁₈ = -23.1217 d ₁₈ = 0.1000 r ₁₉ = 42.5166 d ₁₉ = 2.0000 n ₁₀ = 1.72916 ν ₁₀ = 54.68 r ₂₀ = -98.2303 d ₂₀ = 1.0000 r ₂₁ = -22.9346 d ₂₁ = 1.0000 n ₁₁ = 1.64769 v ₁₁ = 31.23 r ₂₂ = -91.7349 d ₂₂ = D ₃ (variable) r ₂₃ = 361.3810 d ₂₃ = 1.0000 n ₁₂ = 1.69895 v ₁₂ = 30.12 r ₂₄ = 21.0078 d ₂₄ = 4.6905 n ₁₃ = 1.61800 v ₁₃ = _{63.38 r 25 = -30.4227 d 25 =} 0.1000 r 26 = 28.6887 d 26 = 4.8304 n 14 = 1.56907 ν 14 = 71.30 r 27 = -1296.2567 f 9.042 25.512 71.982 D 1 1.4000 19.2073 31.0777 D 2 31.0774 13.2701 1.4000 D 3 12.9928 8.1260 6.8860

Example 5 f = 9.027 to 25.493 to 71.995, F number = 2.0 2ω = 50.00 ° to 18.37 ° to 6.44 ° r ₁ = 115.2569 d ₁ = 2.0000 n ₁ = 1.83350 ν ₁ = 21.00 r ₂ = 68.9119 d ₂ ＝ 4.4695 n ₂ = 1.56907 ν ₂ ＝ 71.30 r ₃ ＝ 2185.3288 d ₃ ＝ 0.1000 r ₄ ＝ 55.7488 d ₄ ＝ 3.7294 n ₃ ＝ 1.43875 ν ₃ ＝ 94.97 r ₅ ＝ 179.8474 d ₅ ＝ 0.1000 r ₆ ＝ 33.1898 d ₆ ＝ 3.8929 n ₄ = 1.43875 ν ₄ = 94.97 r ₇ = 67.9799 d ₇ = D ₁ (variable) r ₈ = 45.6227 d ₈ = 1.0000 n ₅ = 1.69350 ν ₅ = 53.23 r ₉ = 13.4945 d ₉ = 6.2844 r ₁₀ = -69.5464 d _{10 = 1.0000 n 6 = 1.61800 ν} 6 = 63.38 r 11 = 21.8303 d 11 = 0.3703 r 12 = 19.0816 d 12 = 2.8281 n 7 = 1.84666 ν 7 = 23.78 r 13 = 146.3291 d 13 = 9.8274 r 14 = -19.7588 d 14 = 1.0000 n ₈ = 1.61800 ν ₈ = 63.38 r ₁₅ = 361.9637 d ₁₅ = D ₂ (variable) r ₁₆ = ∞ (aperture) d ₁₆ = 1.0000 r ₁₇ = -101.7839 d ₁₇ = 2.4042 n ₉ = 1 .69680 v ₉ = 56.49 r ₁₈ = -26.7962 d ₁₈ = 0.1000 r ₁₉ = 25.9697 d ₁₉ = 1.7529 n ₁₀ = 1.729 16 v ₁₀ = 54.68 r ₂₀ = 426.1334 d ₂₀ = 2.1578 r ₂₁ = -29.3911 d ₂₁ = 1.0000 n ₁₁ = 1.79850 ν ₁₁ = 22.60 r ₂₂ ＝ 976.6142 d ₂₂ ＝ D ₃ (variable) r ₂₃ ＝ 56.8863 d ₂₃ ＝ 2.8709 n ₁₂ ＝ 1.61800 ν ₁₂ ＝ 63.38 r ₂₄ ＝ -33.2523 d ₂₄ ＝ 3.9820 r ₂₅ ＝ 24.3917 d ₂₅ ＝ _{6.1453 n 13 = 1.61800 ν 13 =} 63.38 r 26 = 973.9783 d 26 = 2.7207 r 27 = -29.7796 d 27 = 2.8201 n 14 = 1.84666 ν 14 = 23.78 r 28 = -102.2677 f 9.027 25.493 71.995 D 1 1.4000 19.5100 32.0413 D 2 32.5980 14.4880 1.9525 D ₃ 12.2278 7.7070 7.3444

Example 6 f = 9.020 to 25.484 to 71.996, F number = 2.0 2ω = 50.08 ° to 18.42 ° to 6.44 ° r ₁ = 101.1167 d ₁ = 2.0000 n ₁ = 1.83350 ν ₁ = 21.00 r ₂ = 63.9633 d ₂ = 5.0143 n ₂ = 1.56907 ν ₂ ＝ 71.30 r ₃ ＝ 2997.7695 d ₃ ＝ 0.1000 r ₄ ＝ 58.7927 d ₄ ＝ 4.3866 n ₃ ＝ 1.43875 ν ₃ ＝ 94.97 r ₅ ＝ 147.1268 d ₅ ＝ 0.1000 r ₆ ＝ 32.5292 d ₆ ＝ 3.8929 n ₄ = 1.43875 ν ₄ ＝ 94.97 r ₇ ＝ 61.8594 d ₇ ＝ D ₁ (variable) r ₈ ＝ 35.3078 d ₈ = 1.0000 n ₅ ＝ 1.69350 ν ₅ ＝ 53.23 r ₉ ＝ 13.0380 d ₉ ＝ 6.4911 r ₁₀ ＝ -67.1482 d _{10 = 1.0000 n 6 = 1.61800 ν} 6 = 63.38 r 11 = 26.9447 d 11 = 0.1000 r 12 = 18.5428 d 12 = 3.4001 n 7 = 1.84666 ν 7 = 23.78 r 13 = 91.9580 d 13 = 9.4209 r 14 = -18.7123 d 14 = 1.0000 n ₈ = 1.61800 ν ₈ = 63.38 r ₁₅ = 85.2849 d ₁₅ = D ₂ (variable) r ₁₆ = ∞ (aperture) d ₁₆ = 1.0000 r ₁₇ = -55.6473 d ₁₇ = 2.2465 n ₉ = 1.69 680 v ₉ = 56.49 r ₁₈ = -22.5779 d ₁₈ = 0.1000 r ₁₉ = 25.4533 d ₁₉ = 2.2732 n ₁₀ = 1.72916 v ₁₀ = 54.68 r ₂₀ = 121.9160 d ₂₀ = 1.2245 r ₂₁ = -23.7885 d ₂₁ = 1.0000 n ₁₁ = 1.79850 ν ₁₁ = 22.60 r ₂₂ = -70.7375 d ₂₂ = D ₃ (variable) r ₂₃ = 76.9 120 d ₂₃ = 2.8709 n ₁₂ = 1.61800 ν ₁₂ = 63.38 r ₂₄ = -24.9755 d ₂₄ = 0.0968 r ₂₅ = 28.4478 d ₂₅ = 4.3604 n ₁₃ = 1.61800 ν ₁₃ = 63.38 r ₂₆ = -737.7441 d ₂₆ = 0.8230 r ₂₇ = -31.2560 d ₂₇ = 2.5428 n ₁₄ = 1.84666 ν ₁₄ = 23.78 r ₂₈ = -91.1493 f 9.020 25.484 71.996 D ₁ 1.4000 19.4050 31.6888 ₂ 32.2401 14.2350 1.9525 D ₃ 12.8168 8.2100 6.9745 However, r ₁ , r ₂ , ... Are the radius of curvature of each lens surface, d
₁ , d ₂ , ... Is the thickness of each lens and the lens interval, n
₁ , n ₂ , ... Is the refractive index of each lens, ν ₁ , ν ₂ ,.
Is the Abbe number of each lens.

The first embodiment has the configuration shown in FIG. 1 and includes a first lens group G ₁ having a positive refractive power, which is fixed during zooming.
During zooming, the second lens group G ₂ having a negative refractive power that moves along the optical axis and has a zoom function, the third lens group G ₃ that has a fixed positive refractive power during zooming, and the zooming It is composed of a fourth lens group G ₄ which has a function of reciprocating at this time and correcting the position of the image plane which fluctuates during zooming. The second lens group G ₂ is composed of a first group G ₂₁ and a second group G ₂₂ , and the second group G ₂₂ is extended toward the object side for focusing.

The first lens group G ₁ includes, in order from the object side, a cemented lens in which a negative meniscus lens having a convex surface facing the object side and a positive lens are cemented together, and a positive meniscus lens having a convex surface facing the object side. The two have a function of narrowing the light beam to the on-axis object point and a function of guiding the light beam emitted from the off-axis object point to the second lens group G ₂ . Normally, the first lens group consists of three lenses, a cemented lens and a positive meniscus lens. However, in order to improve optical performance in a lens system having a large zoom ratio and a large axial light flux at the telephoto end, Further, it is effective to dispose a positive meniscus lens and gently refract the light beam. In this embodiment, by constructing the first lens group G ₁ in this way, the amount of aberration generated in this lens group is kept small, and the positive refractive power of the first lens group G ₁ causes the second lens group G 1. The ray height after ₂ becomes low, so that aberration correction is relatively easy even if the ray height changes due to large zooming.

The second lens group comprises, in order from the object side, a negative meniscus lens having a positive convex surface facing the object side, and a negative lens having a surface having a negative refractive power stronger on the image side than the object side and the object side. The first group G ₂₁ consisting of three lenses of positive meniscus lens with the convex surface facing the lens, and the negative refractive power on the object side is stronger than that on the image side arranged at a distance from the first group G _21. The second lens group G _{22 is} composed of a negative lens having a surface of, and is a lens group that performs zooming by moving from the object side to the image side during zooming from the wide-angle end to the telephoto end. . This second lens group G ₂ is provided with a strong negative meniscus lens having a convex surface directed toward the object side, in particular, in the first group G ₂₁ , so that spherical aberration that occurs in the first lens group G ₁ and fluctuates due to zooming, Coma and astigmatism are canceled by the meniscus lens of the first group G ₂₁ in any zooming state. Further, since the second lens group G ₂₂ moves for focusing, the second lens group G ₂₂ is arranged at a proper distance from the first lens group G ₂₁ and has an appropriate refracting power so that the second lens group G ₂₂ can move in a focusing amount. It is made to be appropriate and the fluctuation of aberration is reduced.

The third lens group G ₃ includes 2 lenses in order from the object side.
It is composed of three lenses, a positive lens and a negative lens having a surface of negative refracting power that is stronger on the object side than on the image side.
The lens group G ₁ to the third lens group G _{3 are set} to be substantially afocal and are fixed during zooming.

Like the third lens group G ₃ , the fourth lens group G ₄ has two positive lenses in order from the object side, and a negative refractive power on the object side surface is stronger than that on the image side. It is composed of three lenses, a lens and a lens, and has the function of correcting the fluctuation of the image plane position at the time of zooming and forming an image of the light flux emitted from the third lens group G ₃ .

The aberration conditions for the object point at infinity in the first embodiment are as shown in FIGS. 7, 8 and 9, and the aberration conditions for the object point of 1 m are as shown in FIGS. 10, 11 and 12.

Embodiments 2 to 6 have the configurations shown in FIGS. 2 to 6. Of these examples, examples 2, 5 and 6
Has the same configuration as that of the first embodiment. In Example 3, the fourth lens group G ₄ is composed of, in order from the object side, a negative meniscus lens having a concave surface facing the image side, a biconvex lens, and a positive meniscus lens having a convex surface facing the object side. Example 1
Is different from Further, in Example 4, the fourth lens group G ₄
However, it differs from the first embodiment in that, in order from the object side, a negative meniscus lens having a concave surface facing the image side, a cemented lens of a biconvex lens, and a positive lens are included.

Aberrations in the zooming states at the object point at infinity and the object point at 1 m in Examples 2 to 6 are shown in FIGS. 13 to 42.

[0037]

According to the present invention, an inner focus type zoom lens having a high zoom ratio and having extremely high optical performance from an object point at infinity to an object point at a short distance, which is suitable for a video camera and a still video camera, is realized. it can.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a lens configuration at a wide-angle end according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a lens configuration at a wide-angle end according to Example 3 of the present invention.

FIG. 4 is a diagram showing a lens configuration at a wide-angle end according to Example 4 of the present invention.

FIG. 5 is a diagram showing a lens configuration at a wide-angle end according to Example 5 of the present invention.

FIG. 6 is a diagram showing a lens configuration at a wide-angle end according to Example 6 of the present invention.

FIG. 7 is an aberration curve diagram of Example 1 at the wide-angle end at an object point at infinity.

8 is an aberration curve diagram of an intermediate focal length at an object point at infinity according to Example 1. FIG.

9 is an aberration curve diagram of Example 1 at the telephoto end at an object point at infinity. FIG.

10 is an aberration curve diagram at the wide-angle end at an object point distance of 1 m in Example 1. FIG.

11 is an aberration curve diagram of an intermediate focal length at an object point distance of 1 m in Example 1. FIG.

FIG. 12 is an aberration curve diagram at the telephoto end at an object distance of 1 m in Example 1.

FIG. 13 is an aberration curve diagram of Example 2 at the wide-angle end at an object point at infinity.

FIG. 14 is an aberration curve diagram of the intermediate focal length at an object point at infinity according to the second embodiment.

FIG. 15 is an aberration curve diagram of Example 2 at the telephoto end at an object point at infinity.

FIG. 16 is an aberration curve diagram at the wide-angle end at an object point distance of 1 m in Example 2.

FIG. 17 is an aberration curve diagram for an intermediate focal length at an object point distance of 1 m in Example 2.

FIG. 18 is an aberration curve diagram at the telephoto end at an object point distance of 1 m in Example 2.

FIG. 19 is an aberration curve diagram of Example 3 at the wide-angle end at an object point at infinity.

20 is an aberration curve diagram of the intermediate focal length at an object point at infinity according to Example 3. FIG.

FIG. 21 is an aberration curve diagram of Example 3 at the telephoto end at an object point at infinity.

FIG. 22 is an aberration curve diagram at the wide-angle end at an object point distance of 1 m in Example 3;

FIG. 23 is an aberration curve diagram for an intermediate focal length at an object distance of 1 m in Example 3.

FIG. 24 is an aberration curve diagram at the telephoto end at an object point distance of 1 m in Example 3.

FIG. 25 is an aberration curve diagram of Example 4 at the wide-angle end at an object point at infinity.

26 is an aberration curve diagram for the intermediate focal length at an object point at infinity according to Example 4. FIG.

FIG. 27 is an aberration curve diagram for a telephoto end at an object point at infinity according to Example 4.

28 is an aberration curve diagram at the wide-angle end at an object point distance of 1 m in Example 4. FIG.

FIG. 29 is an aberration curve diagram of the intermediate focal length at an object point distance of 1 m in Example 4.

FIG. 30 is an aberration curve diagram at the telephoto end at an object point distance of 1 m in Example 4.

FIG. 31 is an aberration curve diagram of Example 5 at the wide-angle end at an object point at infinity.

FIG. 32 is an aberration curve diagram for an intermediate focal length at an object point at infinity according to Example 5.

FIG. 33 is an aberration curve diagram of Example 5 at the telephoto end at an object point at infinity.

34 is an aberration curve diagram at the wide-angle end at an object point distance of 1 m in Example 5. FIG.

FIG. 35 is an aberration curve diagram for an intermediate focal length at an object distance of 1 m in Example 5.

FIG. 36 is an aberration curve diagram at the telephoto end at an object distance of 1 m in Example 5.

FIG. 37 is an aberration curve diagram of Example 6 at the wide-angle end at an object point at infinity.

FIG. 38 is an aberration curve diagram for the intermediate focal length at an object point at infinity according to Example 6;

FIG. 39 is an aberration curve diagram for Example 6 at the telephoto end at an object point at infinity.

FIG. 40 is an aberration curve diagram at the wide-angle end at an object point distance of 1 m in Example 6.

FIG. 41 is an aberration curve diagram for an intermediate focal length at an object distance of 1 m in Example 6.

42 is an aberration curve diagram at the telephoto end for the object point distance of 1 m in Example 6. FIG.

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[Procedure amendment]

[Submission date] August 23, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

[0026]

Claims (2)

[Claims] 1. A first lens group having a positive refracting power in order from the object side, a second lens group having a negative refracting power which moves along an optical axis to mainly perform a zooming action, and a zooming factor. The third lens group having a positive refracting power which is fixed at the time of, and the fourth lens group having a positive refracting power which corrects the variation of the image plane position due to the zooming, and the second lens group from the object side. A zoom lens comprising, in order, a first group having negative refracting power and a second group having a negative refracting power, which is a focusing group. 2. The zoom lens according to claim 1, wherein the second lens unit of the second lens unit satisfies the following condition (1). Where f ₂₂ is the focal length of the second lens group of the second lens group, f _W ,
f _T is the focal length of the entire system at the wide-angle end and the telephoto end, respectively.