JPH06214160A - Zoom lens - Google Patents

Abstract

PURPOSE:To provide a zoom lens with extremely highly variable power equal to about 12 magnification or more and which has comparatively simple constitu tion capable of being compact. CONSTITUTION:The zoom lens is constituted of a front group which has a first lens group having positive refracting power and a second lens group having negative refracting power, and a rear group which has positive refracting power in that order from an object side; and in the case of performing variable power, the performance consists of a first variable power area moving the first lens group having the positive refracting power and the second lens group having the negative refracting power in the front group, a second variable power area fixing the first lens group and moving the second lens group, and a third variable power area moving at least one part of the first lens group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and more particularly to a zoom lens having a high zoom ratio, which is suitable for a video camera or the like.

[0002]

2. Description of the Related Art In recent years, various video camera lenses have been actively developed with the spread of home-use integrated video cameras. 10 for these zoom lesbians
There are some known relatively high variable powers, such as double. Among these, a compact type is composed of four lens groups having positive, negative, positive, and positive refractive powers in order from the object side, and the second lens group and the fourth lens group move during zooming. Are known. This type is characterized in that the fourth lens unit has the focusing function, and the number of moving units including focusing becomes two, which is very advantageous for compactness.

[0003]

However, in such a type, since there are only two moving groups, it has been difficult to further increase the zoom ratio. Especially in the case of about 12 times or more, the aberration varies greatly due to zooming, and it becomes impossible to completely correct the performance change. In addition, there has been a problem that the amount of movement of the lens is increased and the total length of the lens is increased if an attempt is made to reduce the performance change due to zooming.

As described above, the zoom lenses known so far have not always been sufficiently satisfactory in response to recent demands for compactness and high zoom ratio.

The present invention has been made to solve the above problems. That is, it is an object of the present invention to provide a zoom lens having a relatively high zoom ratio of about 12 times or more and a relatively simple structure that can be made compact.

[0006]

The above object is to provide a first lens group having a positive refractive power and a front lens group having a second lens group having a negative refractive power and a positive refractive power in order from the object side. A first lens unit which is composed of a rear lens unit, and which moves a first lens unit having a positive refractive power and a second lens unit having a negative refractive power of the front lens unit during zooming.
And a second variable power range for moving the second lens group while fixing the first lens group, and a third variable power range for moving at least part of the first lens group. It is achieved by a zoom lens.

[0007]

The basic structure of the present invention is, in order from the object side,
First lens group having positive refractive power, second lens group having negative refractive power
It consists of a front group having a lens group and a rear group having a positive refractive power. The first variable power range is performed by moving the first lens group having a positive refractive power and the second lens group having a negative refractive power of the front lens group during zooming. This is advantageous in reducing the diameter of the front lens as compared with the case where only the second lens group is moved when the magnification is changed near the wide end. That is, when trying to achieve a high zoom ratio with the first lens group fixed and arranged in advance, it is necessary to increase the diameter of the front lens so that the chief ray cannot be blocked between the wide and middle positions. This is because the first lens group is fixed and the distance between the second lens group and the first lens group increases as the second lens group moves due to zooming. However, if the first lens group is moved as in the present invention, the first lens group can be arranged so as to have a small distance from the second lens group, and the front lens diameter can be reduced. The second variable power range is for fixing the first lens group and moving the second lens group. In this zooming range, zooming is performed mainly by moving the second lens group. The third variable power range is characterized in that at least a part of the first lens group is moved. This is effective in reducing the amount of zooming movement of the second lens unit on the tele side in the second zooming range and reducing the burden of performance change correction due to zooming. This makes it possible to obtain a longer focal length on the telephoto side with a simple structure.

In the present invention, it is desirable that the following conditions be satisfied.

7 <(Z · F _W ) / | F ₂ | <15 where F _{W is} the wide end focal length of the first variable range F ₂ : The focal length of the second lens group Z is the first variable range Magnification ratio from the wide end of to the tele end of the third magnification range: If the upper limit of these conditions is exceeded, the performance change due to magnification will be large and performance correction will be difficult, and if the lower limit is exceeded,
The overall length becomes long, which is disadvantageous to compactness.

[0010]

EXAMPLES The present invention will be specifically described below with reference to examples.

The lens shown in FIG. 1 which is Embodiment 1 is arranged in order from the object side, and the front group is a first lens group consisting of a cemented lens of a negative lens and a positive lens and a positive meniscus lens, a negative meniscus lens, and a negative lens. The second lens group includes a biconcave lens and a positive lens. The rear group is a positive lens, a lens having a weak refractive power with a convex surface having an aspherical surface facing the image side,
It is composed of a lens having a weak refractive power with a convex surface having an aspherical surface facing the object side, and a cemented lens of a negative lens and a positive lens. Further, an image pickup element is provided in the rear portion of the rear group, and this image pickup element is moved to correct the image forming position.

The movement of the first embodiment due to zooming is as shown in FIG. In FIG. 1, the first lens group and the second lens group of the front group move to perform magnification change in the first magnification range in order from the wide side. In addition, in this embodiment, the first lens group and the second lens group have the same amount of movement, which makes it possible to make the lens movement speeds of the two groups the same during zooming in the first zoom range. It is not necessary to control the two groups independently, and the controllability can be improved. In the second variable power range, the second lens group and the fourth lens group move to perform variable power. In the third variable power range, the cemented lens of the negative lens and the positive lens in the first lens group is moved to perform the variable power, or the entire first lens group, that is, the negative lens and the positive lens. The cemented lens and the positive meniscus lens are moved to change the magnification. When the cemented lens of the negative lens and the positive lens in the first lens group is moved to change the magnification, there is an advantage that the driving force is smaller than the total movement of the first lens group. In addition, the entire movement of the first lens group
A large driving force is required for moving the lenses, but the lens movement amount is smaller than that for moving only the front two lenses, which is advantageous for downsizing the lens.

The lens shown in FIG. 2, which is Embodiment 2, is arranged in order from the object side. The front lens group is a first lens group composed of a cemented lens of a negative lens and a positive lens and a positive meniscus lens, a negative meniscus lens, and a negative lens. The second lens group includes a biconcave lens and a positive lens. The rear lens group is a positive lens, a lens having a convex surface having an aspherical surface and having a weak refractive power in the opposite direction to the object side, a lens having a convex surface having an aspherical surface and having a weak refractive power, and a negative lens and a positive lens being attached. It is composed of a compound lens. Further, an image pickup element is provided in the rear portion of the rear group, and this image pickup element is moved to correct the image forming position.

The movement of the second embodiment due to zooming is as shown in FIG. In FIG. 2, the first lens group and the second lens group of the front group move to perform zooming in the first zooming range in order from the wide side. Further, in this embodiment, the first lens group has a smaller movement amount than the second lens group.
This is effective in reducing the amount of movement of the first lens group during zooming in the first zoom range and shortening the overall lens length. In the second variable power range, the second lens group and the fourth lens group move to perform variable power. In the third variable power range, the first lens group is moved to perform variable power.

The lens shown in FIG. 3, which is Embodiment 3, is arranged in order from the object side. The front lens group is a first lens group consisting of a cemented lens of a negative lens and a positive lens and a positive meniscus lens, a negative meniscus lens, and a negative lens. The second lens group includes a biconcave lens and a positive lens. The rear lens group is a positive lens, the third lens group is composed of a lens having a convex surface having an aspherical surface in the opposite direction to the object side and having a weak refracting power, a lens having a convex surface having an aspherical surface is in a weak refractive power, and a negative lens. It is composed of a fourth lens group consisting of a cemented lens of a lens and a positive lens, and is fixed during zooming. Further, an image pickup element is provided in the rear portion of the rear group, and this image pickup element is moved to correct the image forming position.

The movement of the third embodiment due to zooming is as shown in FIG. In FIG. 3, the first lens group and the second lens group of the front group move to perform zooming in the first zooming range in order from the wide side. Second in the second zoom range
Zooming is performed by moving the lens group, and the fourth lens group is fixed. In the third zoom range, the first
Zooming is performed by moving the lens group. In the present embodiment, the rear group is fixed during zooming, and it is not necessary to have a mechanism for movement, and the mechanism can be simplified.

The lens shown in FIG. 4, which is the fourth embodiment, is arranged in order from the object side. The front lens group is a first lens group composed of a cemented lens of a negative lens and a positive lens and a positive meniscus lens, a negative meniscus lens, and a negative lens. It is composed of a second lens group including a biconcave lens and a positive lens, and has a positive refracting power as a whole. The rear group includes a positive lens, a lens having a weak refractive power with a convex surface having an aspherical surface facing away from the object side, a lens having a weak refractive power having a convex surface having an aspherical surface facing the object side, a negative lens and a positive lens. It consists of a cemented lens. Further, an image pickup element is provided in the rear portion of the rear group, and this image pickup element is moved to correct the image forming position.

The movement of the fourth embodiment due to zooming is as shown in FIG. In FIG. 4, the first lens group and the second lens group of the front group move to perform zooming in the first zooming range in order from the wide side. The second variable power region is a first region in which zooming is performed by moving the second lens unit, and a second region in which zooming is performed by moving the second lens unit and the fourth lens unit. have. In the third variable power range, the first lens group is moved to perform variable power.

Further, as shown in FIG. 5, Examples 1 to 4
In, it is possible to shift the focal length at the wide end to the wide side by removing part or all of the first lens group. It is also possible to add a variable power range between the wide end before the separation and the wide end after the separation by moving the second lens group in this state to change the magnification. For focusing, it is effective to use an image sensor or a lens group that moves during zooming to reduce the number of moving groups and simplify the configuration.

In the examples, a low-pass filter, an infrared cut filter, and a cover glass corresponding to a face plate are provided between the final lens surface and the image plane. Each symbol in the table is NO: Lens surface number R: Curvature radius of each refracting surface D: Refractive surface interval N: Refractive index of glass material of lens ν: Abbe number of glass material of lens F: Focal length of entire lens system L : Lens number FNO: F number Z: Zoom ratio (wavelength is d line = 587.56 nm).

Further, the definition of the aspherical surface coefficient in the embodiments is as follows.

[0022]

[Equation 1]

Where X is the origin of the aspherical vertex, coordinates from the object side to the image side along the optical axis, h is the origin of the aspherical vertex, and c is the coordinate perpendicular to the optical axis. Represents the axial curvature.

Example 1 NOR D N ν 1 53.725 0.80 1.84666 23.8 L1 first lens group (withdrawal) front group 2 25.448 3.90 1.69680 55.5 L1 first lens group (withdrawal) front group 3-846.342 A L2 first lens group (Leaving) Front group 4 22.518 2.60 1.69680 55.5 L3 First lens group (Leaving) Front group 5 62.154 BL3 First lens group (Leaving) Front group 6 78.016 0.60 1.77250 49.6 Second lens group Front group 7 6.819 2.55 Second lens Group Front group 8-13.823 0.60 1.77250 49.6 Second lens group Front group 9 13.823 1.10 Second lens group Front group 10 16.330 1.65 1.84666 23.8 Second lens group Front group 11-95.135 C Second lens group Front group 12 14.126 2.70 1.51633 64.1 Third lens group Rear group 13 −46.559 0.95 Third lens group Rear group 14 −16.000 1.40 1.49200 57.0 Third lens group Rear group 15 −16.000 D 3rd lens group Rear group 16 20.280 1.40 1.49200 57.0 Fourth lens group Rear group 17 17.435 0.55 4th lens group Rear group 18 32.223 0.70 1.84666 23.8 4th lens group Rear group 19 9.690 4.05 1.69680 5 5.5 4th lens group Rear group 20 −20.111 E 4th lens group Rear group 21 INF 5.53 1.51633 64.1 Cover glass 22 INF Cover glass

[0025]

[Table 1]

Focal length of each lens group F ₁ first lens group 32.77 F ₂ second lens group −6.704 F ₃ third lens group 21.57 F ₄ fourth lens group 24.74 L1 and L2 move Z = 12.7 (including separation of the first lens group) (Z · F _W ) / | F ₂ | = 10.26 (Z = 17.7) ・ The first lens group as a whole moves in the third zoom range Z = 14.2 (including disengagement of the first lens group) (Z · F _W ) / | F ₂ | = 11.48 (Z = 19.7) Example 2 NOR D N ν 1 52.731 0.80 1.84666 23.8 L1 1st lens group (L1, L2 leaving) Front group 2 25.580 4.10 1.69680 55.5 L1 1st lens group (L1, L2 leaving) Front group 3 4474.327 0.50 L2 1st lens group (L1, L2 leaving) Front group 4 21.878 2.70 1.69680 55.5 L3 1st lens group ( L1, L2 leaving) Front group 5 57.203 A L3 First lens group (L1, L2 leaving) Front group 6 49.299 0.60 1.77250 49.6 Second lens group Front group 7 6.780 2.75 Second lens group Front group 8 −12.761 0.60 1.77250 49.6 Second group 2 Ren Front group 9 12.761 1.10 Second lens group Front group 10 16.116 1.65 1.84666 23.8 Second lens group Front group 11 −84.878 B Second lens group Front group 12 15.789 2.80 1.51633 64.1 Third lens group Rear group 13 −30.910 0.70 Third group Lens group Rear group 14 −16.000 1.40 1.49200 57.0 3rd lens group Rear group 15 −16.000 C 3rd lens group Rear group 16 18.876 1.40 1.49200 57.0 4th lens group Rear group 17 17.435 0.55 4th lens group Rear group 18 39.140 0.70 1.84666 23.8 4th lens group Rear group 19 10.258 4.05 1.69680 55.5 4th lens group Rear group 20 −19.708 D 4th lens group Rear group 21 INF 5.53 1.51633 64.1 Cover glass 22 INF Cover glass

[0027]

[Table 2]

Focal length of each lens group F ₁ First lens group 33.53 F ₂ Second lens group −6.56 F ₃ Third lens group 20.92 F ₄ Fourth lens group 25.45 Z = 13.3 (L1 and L2 of the first lens group) (Including disengagement) (Z · F _W ) / | F ₂ | = 10.18 (Z = 15.4) Example 3 NOR D N ν 1 55.600 0.80 1.84666 23.8 L1 1st lens group (L1, L2 disengagement) Front group 2 28.225 4.00 1.69680 55.5 L1 1st lens group (L1, L2 leaving) front group 3 511.946 0.50 L2 1st lens group (L1, L2 leaving) front group 4 28.949 2.60 1.71300 53.9 L3 1st lens group (L1, L2 leaving) front group 5 91.403 A L3 1st lens group (L1, L2 detached) front group 6 30.991 0.60 1.77250 49.6 2nd lens group front group 7 9.209 3.50 2nd lens group front group 8 −15.229 0.60 1.77250 49.6 2nd lens group front group 9 10.970 1.00 2nd lens group front group 10 13.462 1.75 1.84666 23.8 2nd lens group front group 11 68.684 B 2nd lens group front group 12 11.989 2.70 1.62299 58.2 3rd lens group rear group 13 55.176 1.00 Third lens group Rear group 14 −26.053 1.40 1.49200 57.0 Third lens group Rear group 15 −22.822 1.95 Third lens group Rear group 16 22.801 1.40 1.49200 57.0 Fourth lens group Rear group 17 26.197 0.60 Fourth lens group Rear group 18 44.545 0.70 1.84666 23.8 4th lens group Rear group 19 12.192 3.60 1.62299 58.2 4th lens group Rear group 20 −15.535 2.42 4th lens group Rear group 21 INF 5.53 1.51633 64.1 Cover glass 22 INF cover glass

[0029]

[Table 3]

Focal length of each lens group F ₁ First lens group 39.58 F ₂ Second lens group −7.44 F ₃ Third lens group 23.00 F ₄ Fourth lens group 23.53 Z = 13.4 (L1 and L2 of the first lens group) (Including disengagement) (Z · F _W ) / | F ₂ | = 9.15 (Z = 15.5) Example 4 NOR D N ν 1 52.731 0.80 1.84666 23.8 L1 1st lens group (L1, L2 disengagement) Front group 2 25.580 4.10 1.69680 55.5 L1 1st lens group (L1, L2 leaving) front group 3 4474.327 0.50 L2 1st lens group (L1, L2 leaving) front group 4 21.878 2.70 1.69680 55.5 L3 1st lens group (L1, L2 leaving) front group 5 57.203 A L3 First lens group (L1, L2 detached) Front group 6 49.299 0.60 1.77250 49.6 Second lens group Front group 7 6.780 2.75 Second lens group Front group 8 −12.761 0.60 1.77250 49.6 Second lens group Front group 9 12.761 1.10 2nd lens group front group 10 16.116 1.65 1.84666 23.8 2nd lens group front group 11 −84.878 B 2nd lens group front group 12 15.789 2.80 1.51633 64.1 3rd lens group rear group 13 −30.910 0.70 3rd lens group Rear group 14 −16.000 1.40 1.49200 57.0 3rd lens group Rear group 15 −16.000 C 3rd lens group Rear group 16 18.876 1.40 1.49200 57.0 4th lens group Rear group 17 17.435 0.55 4th lens group Rear group 18 39.140 0.70 1.84666 23.8 4th lens group Rear group 19 10.258 4.05 1.69680 55.5 4th lens group Rear group 20 −19.708 D 4th lens group Rear group 21 INF 5.53 1.51633 64.1 Cover glass 22 INF Cover glass

[0031]

[Table 4]

Focal length of each lens group F ₁ First lens group 33.53 F ₂ Second lens group −6.56 F ₃ Third lens group 20.92 F ₄ Fourth lens group 25.45 Z = 13.3 (L1 and L2 of the first lens group) (Including disengagement) (Z · F _W ) / | F ₂ | = 10.18 (Z = 15.4)

[0033]

According to the present invention, as can be seen from each of the embodiments and the drawings, the zooming ratio is as high as about 15 to 20 times including the zooming when the first lens group is disengaged, and the structure is simple. A compact zoom lens with good performance has been provided.

[Brief description of drawings]

FIG. 1 is a lens sectional view and a basic lens movement diagram of a first embodiment of a zoom lens according to the present invention.

FIG. 2 is a lens sectional view and a basic lens movement diagram of a second embodiment of the zoom lens according to the present invention.

FIG. 3 is a lens sectional view and a basic lens movement diagram of a third embodiment of the zoom lens according to the present invention.

FIG. 4 is a lens sectional view and a basic lens movement diagram of a fourth embodiment of the zoom lens according to the present invention.

FIG. 5 is a lens cross-sectional view of the zoom lens according to the present invention with the first lens group in a detached state.

FIG. 6 is a first example of the first embodiment of the zoom lens according to the present invention.
FIG. 6 is an aberration diagram when the entire lens group is detached.

FIG. 7 is a first example of the first embodiment of the zoom lens according to the present invention.
Aberration diagrams at the wide end in the zoom range.

FIG. 8 is a second example of the first embodiment of the zoom lens according to the present invention.
Aberration diagrams at the wide-angle end, middle end, and tele end in the zoom range, (a)
Is a wide end, (b) is a middle view, and (c) is an aberration diagram at a tele end.

FIG. 9 is a third embodiment of the zoom lens according to the present invention.
FIG. 9 is an aberration diagram at the telephoto end when L1 and L2 of the first lens unit move in the zoom range.

FIG. 10 is an aberration diagram at a telephoto end when the entire first lens unit moves in a third zoom range of Example 1 of the zoom lens according to the present invention.

FIG. 11 is an aberration diagram when L1 and L2 of the first lens unit of Example 2 of the zoom lens according to the present invention are separated.

FIG. 12 is an aberration diagram at a wide-angle end of the first zoom range of Example 2 of the zoom lens according to the present invention.

FIG. 13 is an aberration diagram at a wide-angle end, a middle end, and a tele end of a second zoom region of Embodiment 2 of the zoom lens according to the present invention.
(A) is an aberration diagram at the wide end, (b) is a middle view, and (c) is an aberration diagram at the tele end.

FIG. 14 is an aberration diagram at a telephoto end of a third zoom region of Example 2 of the zoom lens according to the present invention.

FIG. 15 is an aberration diagram when L1 and L2 of the first lens unit of Example 3 of the zoom lens according to the present invention are separated.

FIG. 16 is an aberration diagram at the wide-angle end of the first zoom range of Example 3 of the zoom lens according to the present invention.

FIG. 17 is an aberration diagram at a wide-angle end, a middle end, and a tele end of a second zoom region of Embodiment 3 of the zoom lens according to the present invention.
(A) is an aberration diagram at the wide end, (b) is a middle view, and (c) is an aberration diagram at the tele end.

FIG. 18 is an aberration diagram at a telephoto end in a third zoom region of Example 3 of the zoom lens according to the present invention.

FIG. 19 is an aberration diagram when L1 and L2 of the first lens unit of Example 4 of the zoom lens according to the present invention are separated.

FIG. 20 is an aberration diagram at a wide-angle end of the first zoom range of Example 4 of the zoom lens according to the present invention.

FIG. 21 is an aberration diagram of Example 4 of the zoom lens according to the present invention at the wide end of the first variable region of the second zoom region.

22A and 22B are aberration diagrams of Example 2 of the zoom lens according to the present invention in a second zoom region, second region, at the wide end, the middle end, and the tele end, where (a) is the wide end, (b) is the middle end, and C) is an aberration diagram at the telephoto end.

FIG. 23 is an aberration diagram at a telephoto end in a third zoom region of Example 4 of the zoom lens according to the present invention.

Claims (1)

[Claims] 1. A first lens element having a positive refractive power in order from the object side.
It consists of a front group having a lens group and a second lens group having a negative refracting power, and a rear group having a positive refracting power, and in zooming, the first lens group having a positive refracting power and the negative refracting power of the front group. Second with
A first variable power range for moving the lens group, a second variable power range for fixing the first lens group and moving the second lens group, first
A zoom lens having a third variable power range for moving at least a part of the lens group.