JPH0763992A - Zoom lens and image pickup device using the same - Google Patents

Abstract

PURPOSE:To provide high optical performance and also to lessen the decrease of a zoom ratio in the case of focusing to an object in a short distance by performing focusing in a state where a lens group including a front lens group is moved in a different ratio in accordance with a zooming position on an optical axis. CONSTITUTION:This device is provided with plural lens groups including a variable power lens group L2 moved on the optical axis in order to perform variable power, and a correcting lens group L3 correcting image surface fluctuation accompanying the variable power; and the focusing is performed by moving at least two lens groups including the front lens group L1 among the plural lens groups in the different ratio in accordance with the zooming position on the optical axis. Since the magnification of the front lens group L1 is always fixed irrespective of the zooming position, the zoom ratio is prevented from being decreased in the zoom lens performing front lens focusing. The front lens group L1 largely affects aberration fluctuation on a telephotographic side, and the front lens group L1 is used as the focusing lens group, so that the aberration caused by the focusing lens group other than the front lens group L1 can be reduced.

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 an image pickup apparatus using the same, and uses a rear focus method suitable for, for example, an image input apparatus, still camera, video camera, TV camera, etc. The following aberration correction is performed.

[0002]

2. Description of the Related Art Conventionally, in a zoom lens as an image pickup means, it is necessary that the aberration correction state be good over the entire zoom range and the entire imageable object distance, and the entire lens system. Is desired to be small and lightweight.

As a focusing (focusing) method in a zoom lens, a method of moving all or part of the frontmost lens group (front lens) in the optical axis direction according to a change in object distance (front lens focusing method) There is.

Generally, when focusing is performed according to the variation of the object distance, the aberration varies. In this case, in order to reduce the fluctuation of aberration during focusing, it is necessary to correct the aberration of the focus lens group as the front lens alone.

However, in this case, there are problems that the number of lenses of the front lens increases and the lens structure becomes complicated. Further, in many conventional zoom lenses, when only the front lens is projected to focus on an object at a short distance, the effective diameter of the front lens is set to be large in advance in consideration of vignetting of light rays.

Therefore, when the simple front lens focus system is adopted, there are many problems that the front lens becomes large in size and heavy in weight.

As one means for solving these problems, a so-called rear focus type zoom lens in which a lens group other than the front lens is moved to perform focusing is known.

Generally, in a rear focus type zoom lens, the effective diameter of the front lens is smaller than that of a zoom lens in which the front lens is moved to perform focusing, which facilitates downsizing of the entire lens system and close-up photography, particularly Since close-up photography is facilitated, and because the relatively small and lightweight lens group is moved, the driving force of the lens group is small and quick focusing is possible.

However, in the conventional zoom lens system having a small number of moving groups, the power of each group is large and the degree of freedom of group movement is small. Therefore, in the inner focusing method and the rear focusing method, zooming and focusing are performed. Aberration variation easily occurs due to.

As a method of coping with such variation in aberration, the focusing lens group itself is composed of a plurality of focusing movement groups,
When performing a focusing operation, that is, focusing, a method of correcting the above-mentioned aberration variation is performed by changing the interval between these focusing movement groups. As an example of this method, the method described in JP-A-61-97618 can be mentioned.

Focusing by changing the distance between the focus moving groups is effective in correcting the aberration variation due to focusing, but in the conventionally known method,
The ratio of the moving distance between the respective focus moving groups is constant with respect to the zoom point, which is preferable in terms of the mechanism for performing the focusing operation, but is not necessarily sufficient in terms of correction of aberration variation.

To solve this problem, Japanese Patent Laid-Open No. 1-27
In Japanese Patent No. 1717, there are three or more zoom lens groups that move integrally with respect to zooming, and one or more zoom lens groups other than the foremost one are used as focusing lens groups. There is disclosed a method for performing focusing in accordance with zooming in a zoom lens having a focusing movement group in which the working lens group moves at different movement amounts during the focusing operation.

[0013]

However, in the method disclosed in Japanese Patent Application Laid-Open No. 1-271717,
The focusing lens group is a zoom lens group other than the frontmost lens group,
The zoom ratio when focusing on a near object point is significantly larger than the zoom ratio when focusing on an object point at infinity because the moving ratio of the focus moving group is determined only by correcting aberration fluctuations. There is a problem that it tends to decrease.

For example, in the lens of the embodiment disclosed in Japanese Patent Laid-Open No. 1-271717, the zoom ratio for the object point at infinity is 3.64, whereas the zoom ratio for the shortest shooting distance of 1.2 m is 3.24. A reduction in zoom ratio of about 11% is seen. When the zoom ratio is reduced to this extent, it is often undesirable in terms of performance.

In the present invention, focusing is performed by using at least two or more lens blocks (the whole or a part of the lens group) including the frontmost lens group in the lens system, and contributes to the focus according to the zoom position. By changing the lens block to move or the moving ratio of lens blocks to each other, deterioration of aberration due to focusing due to change of object distance at all zoom positions is minimized, and high optical performance is achieved over the entire object distance. An object of the present invention is to provide a zoom lens and an image pickup apparatus using the zoom lens in which the zoom ratio does not decrease when focusing on a distance object.

[0016]

A zoom lens according to the present invention comprises a plurality of lens groups including a zoom lens group that moves on the optical axis for zooming and a correction lens group that corrects image plane fluctuations associated with zooming. Of the plurality of lens groups, at least two lens groups including the frontmost lens group are moved at different ratios according to the zoom position on the optical axis for focusing.

Since the magnification of the forefront lens group with respect to an object at the same distance from the forefront lens group is always constant irrespective of the zoom position, the zoom ratio does not decrease in the zoom lens for focusing the front lens.

Therefore, in the focusing method of the present invention, the effect of reducing the reduction in zoom ratio is obtained by using the frontmost lens group as one of the focusing blocks.

Further, in the rear focus system, the amount of movement for focusing is generally large on the telephoto side, so that aberrations due to focusing on the telephoto side vary greatly.

On the telephoto side, since the height of the axial ray passing through the frontmost lens group is high, the influence on the aberration variation of the frontmost lens group is large, and by using the frontmost lens group as the focusing lens group, There is also an effect that the aberration caused by the focusing lens group other than the lens group can be effectively reduced.

Further, with reference to the state of focusing on an object point at infinity, the movement amounts of the frontmost lens groups at the wide-angle end and the telephoto end when focused on an object point at a finite distance are X _1W and X _1T , respectively. In this case, it is desirable that | X _1T |> | X _1W |

The following points can be given as meanings when the above equation (1) is followed.

A. Although the vignetting of a light beam on an object at a close range, which has been a problem in front-lens focusing, becomes severe on the wide-angle side, satisfying the above formula (1) helps prevent the front-lens diameter from increasing.

B. Since the amount of movement of the focusing lens group other than the front lens is generally much larger on the telephoto side than on the wide angle side, the amount of movement of the front lens at the telephoto end was increased to make the amount of movement of the focusing lens group other than the front lens wide-angle end. The difference at the telephoto end can be reduced, which is useful for downsizing, prevention of reduction in zoom ratio when focusing on an object at a close range, and reduction of aberration variation due to focusing.

Further, the image pickup apparatus using the zoom lens of the present invention comprises a distance detecting means for detecting object distance information, a storing means for storing data necessary for focusing corresponding to the zoom position, and an optical axis for zooming at least. A variable power lens group that moves upward and a plurality of lens groups including a correction lens that corrects an image plane variation due to variable power are provided, and control is performed using distance information from the distance detection means and data from the storage means. By means
It is characterized in that at least two lens groups of the plurality of lens groups are moved at different ratios according to the zoom position on the optical axis for focusing.

[0026]

Embodiment 1 FIG. 1 is a schematic view of a main part of Embodiment 1 of a zoom lens and an image pickup apparatus using the same according to the present invention, and FIG. 2 is a lens cross section of a zoom lens of FIG. It is a figure.

In the figure, L1 is a front lens group, which has a focus function of moving along the optical axis for focusing in accordance with a change in the object distance. L2 is a variable power lens group for variable power, L3 is a correction lens group for correcting the image plane variation due to variable power, and L4 is a relay lens group that performs an image forming action. The relay lens group L4 has two lens groups, a relay front group RF that moves on the optical axis during focusing and a fixed relay rear group RR. G is a glass block such as a color separation optical system and a filter.

When varying the magnification from the wide-angle end to the telephoto end, the variable-magnification lens unit L2 and the correction lens unit L3 are moved on the optical axis as indicated by the arrow.

At the time of focusing, the front lens group L1 and the relay front group RF are used as a focus block and are moved on the optical axis while changing the moving ratio of these lens groups according to changes in the object distance and zoom position. I am going.

Next, the focus operation in FIG. 1 will be described. FIG. 1 shows an example of so-called autofocus (automatic focusing operation).

In the figure, A (A1 to A4) is drive means for moving each lens group on the optical axis, and B (B1 to B4) is position detection means for detecting the position of each lens group on the optical axis.

Reference numeral 1 is a distance detecting means for detecting object distance information by a known method. Reference numeral 2 denotes a storage unit that stores the amount of movement of the correction unit according to the input of the magnification change, the focusing block to be selected at the zoom position from the zoom position information and the object distance information, and the information of the moving ratio thereof. .

Reference numeral 3 is a control means, which takes in information from the distance detection means 1 and the position detection means B and calls data from the storage means 2, and uses the information to drive each lens group A. Control the drive of.

In this embodiment, at the time of zooming (magnification), the control means 3 calculates the amount of movement of the correction lens group L3 from the position information from the position detection means B2 of the variable magnification lens group L2 and the data in the storage means 2. , Driving means A for the correction lens group L3
3 drive control is performed. At the time of focusing, the control unit 3 uses the position information from the position detection unit B2 of the variable power lens unit L2 to obtain data from the storage unit 2 for each lens unit L.
1. Select a focusing block from RF.

Then, the moving ratio between the focusing blocks is read, and drive control of the drive means (A1, A4) of each lens group L1, RF is performed based on the object position information from the distance detection means 1. This is the focus.

In the present embodiment, the distance detecting means 1 may be replaced with a focus detecting means, and focus control may be performed according to the focus information from the focus detecting means.

Next, in Numerical Embodiment 1 of FIG. 2, the moving ratio of the front lens group L1 and the relay front group RF at each zoom position when focusing on a finite object and the position of the focusing block when the object distance is infinity. The front lens group L1 at each zoom position when focusing on an object at a distance of 1 m from the first surface of the lens,
Table 1 shows the amount of movement of the relay front group RF. The sign of the amount of movement is positive when the lens block moves toward the image side and negative when the lens block moves toward the object side.

[0038]

[Table 1] Next, in FIGS. 3, 4 and 5, the shortest focal length (hereinafter referred to as “wide”, referred to as W = f = 9.35 mm) of the zoom lens of Numerical Embodiment 1 with respect to the object point at infinity, and the intermediate focal length ( Hereinafter referred to as “middle” and referred to as M. f = 59.1
mm) and the longest focal length (hereinafter referred to as "tele" and referred to as T, f = 118.1 mm).

Further, FIGS. 6, 7 and 8 show aberration diagrams at wide, middle and tele at an object distance of 1 m when focusing according to the present invention (from the first lens surface, the same applies hereinafter). As shown in FIGS. 6 to 8, it can be seen that the aberration at each zoom position is kept good by changing the moving ratio of the two focus groups according to the zoom position.

For reference, FIGS. 9, 10 and 11 show wide-angle, middle-angle and telescopic aberration diagrams when focusing is performed with only the front lens at an object distance of 1 m.

As shown in FIG. 11, when focusing is performed with only the front lens, the aberration becomes more serious as it goes to the tele side.

The object distance of 1 m is shown in FIGS. 12, 13 and 14.
6A and 6B show aberration diagrams in wide, middle, and tele when focusing is performed only on the relay front group RF. Also in this case, as shown in FIG. 14, the aberration becomes worse toward the telephoto side.

Generally, in a zoom lens having a large zoom ratio, the zoom ratio is likely to decrease due to focusing on an object at a close range, but in the zoom lens of the first embodiment, the zoom ratio at the time of focusing an object at infinity is 1.
Despite being very large at 2.64, the zoom ratio when focusing on an object at a distance of 1 m is 11.75, which is about 7%.
Has remained low.

For reference, in Example 1, the zoom ratio when focusing on an object of 1 m with only the RF group is 8.30, and the reduction of the zoom ratio is about 34%.

From the above, it can be seen that the reduction of the zoom ratio is effectively suppressed in the first embodiment.

In general, when the front lens focusing system is adopted in the zoom lens of the type according to the present embodiment, vignetting of light rays when the front lens is extended in order to focus on an object at a close range particularly at the wide end. Considering the above, the diameter of the front lens is made large in advance.

On the other hand, Example 1 shown in Table 1 of the present invention
According to the focus system in (1), the front lens diameter is reduced because the front lens is not extended in a wide range.

Further, according to the focusing method in the first embodiment, since the moving amount of the front lens, which is the heaviest portion, is reduced, the focusing speed is increased and the power consumption is reduced. .

FIG. 15 is a schematic view of the essential portions of Embodiment 2 of the zoom lens and the image pickup apparatus using the same according to the present invention, and FIG. 16 is FIG.
9 is a lens cross-sectional view of Numerical Example 2 of the zoom lens of No. 5 described later.

In the figure, LL1 is the first group of negative refracting power, LL2
Is a second group having a positive refractive power, and LL3 is a third group having a positive refractive power. Zooming from the wide-angle end to the telephoto end is performed with the first lens unit LL1 and the second lens unit.
The distance from the group LL2 is reduced, and the second group LL2 and the third group LL
The first group LL1 and the second group LL so that the distance from
The second and third lens units LL3 are moved along the optical axis as shown in FIG.

In this embodiment, the first group LL1 and the third group LL3
Is selected as the focusing block, and the movement ratio of each lens unit is changed for each zoom position to reduce aberration fluctuations during focusing and obtain high optical performance over the entire object distance.

Control of the movable lens block by zooming and focusing is performed in the same manner as in the first embodiment.

The first example at each zoom position when focusing on a finite distance object in the numerical example 2 of FIG.
Based on the moving ratio of the group LL1 and the third group LL3, and the position of the focusing block when the object distance is infinity,
The first group LL1 and the third group LL3 at each zoom position when focusing on an object at a distance of 50 cm from the image plane
Table 2 shows the movement amount of the group LL3. Signs are positive when the lens block moves toward the image side and negative when the lens block moves toward the object side.

Further, the zoom lens of Embodiment 2 has a zoom ratio of 2.01 when focusing on an object at infinity and a zoom ratio of 2.01 when focusing on an object of 50 cm, which is the above focusing method. By using, a zoom lens without a reduction in zoom ratio due to focusing is achieved.

[0055]

[Table 2] Next, in FIGS. 17, 18 and 19, the zoom lens of Numerical Example 2 has a wide range (f = 24.
4mm), middle (f = 34.9mm), tele (f = 4)
The aberration figure in (9.0 mm) is shown.

20, FIG. 21, and FIG. 22 are shown when focusing is performed by changing the moving ratio of the first lens group LL1 and the third lens group LL3 for each zoom position in the second embodiment (from the image plane, the same applies hereinafter. ) Wide, middle, at an object distance of 50 cm
The aberration figure of tele is shown.

For reference, in FIG. 23, FIG. 24, and FIG. 25, the object distance 5 when only the third lens group LL3 is focused.
Aberration diagrams at wide, middle, and tele at 0 cm are shown.

As can be seen from FIGS. 20 to 25, by using the focusing method according to the present invention, it is possible to effectively prevent the occurrence of various aberrations when focusing on an object at a close range in the entire zoom range.

FIG. 26 is a schematic view of the essential portions of Embodiment 3 of the zoom lens and the image pickup apparatus using the same according to the present invention, and FIG.
FIG. 9 is a lens cross-sectional view of Numerical Example 3 to be described later of the zoom lens of No. 6 and a diagram showing how to move each group for zooming.

In the figure, LLL1 is the first group of positive refracting power, LL
L2 is a second group having a negative refractive power, and LLL3 is a third group having a positive refractive power.

Zooming from the wide-angle end to the telephoto end is performed by the second lens unit LLL.
2 is fixed, and the first group LLL1 and the third group LLL3 are moved toward the object side (leftward in the figure) on the optical axis as shown in FIG.

As described above, the zoom lens of the third embodiment has the same structure as the zoom lens of the embodiment disclosed in Japanese Patent Laid-Open No. 1-271717.

In the third embodiment, the third lens unit LLL3 is set to LLL3.
a, LLL3b, LLL3c divided into three blocks,
By selecting the first group LLL1 and the lens groups LLL3b and LLL3c as focusing blocks, and changing the moving ratio of each lens group for each zoom position, the aberration variation during focusing is reduced, and high optical performance is achieved over the entire object distance. In addition, the zoom ratio is prevented from decreasing. The control of the movable lens block by zooming and focusing is performed by the same method as in the first and second embodiments.

In Numerical Example 3 of FIG. 27, the lens in the first lens unit LLL1 and the third lens unit LLL3 at each zoom position when focusing on a finite object with reference to the position of the focusing block when the object distance is infinity. Table 3 shows the moving ratios of the blocks LLL3b and LLL3c, and the moving amount at each zoom position when focusing on an object at a distance of 1.2 m (from the image plane, the same applies below). Signs are positive when the lens block moves toward the image side and negative when the lens block moves toward the object side.

[0065]

[Table 3] Next, FIGS. 28, 29, and 30 show a wide range (f = 36.
0mm), middle (f = 68.7mm), tele (f = 1)
The aberration figure in 31.3 mm) is shown.

31, 32, and 33, the first group LLL1 and the lens block LLL in the third group according to the third embodiment.
The aberration figure in wide, middle, and tele in the object distance 1.2m when focusing is performed by changing the moving ratio of 3b and LLL3c for every zoom position is shown.

As shown in FIGS. 31 to 33, by using the focusing method according to the present invention, it is possible to effectively prevent the occurrence of various aberrations when focusing on an object at a close range in the entire zoom range.

Further, in the third embodiment, the zoom ratio when focusing on an object of 1.2 m is 3.87, whereas the zoom ratio when the object distance is infinity is 3.64, which is 3.87.
Although the zoom lens has the same configuration as the zoom lens of the embodiment disclosed in No. 271717, it is possible to prevent the zoom ratio from being lowered due to focusing.

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

Numerical Example 1 f = 9.345 fno = 1: 1.7 2ω = 61.0 ° R 1 = -2337.70 D 1 = 2.50 N 1 = 1.80518 ν 1 = 25.4 R 2 = 107.51 D 2 = 3.84 R 3 = 330.35 D 3 = 8.40 N 2 = 1.43387 ν 2 = 95.1 R 4 = -123.70 D 4 = 0.15 R 5 = 181.98 D 5 = 8.36 N 3 = 1.49700 ν 3 = 81.6 R 6 = -158.76 D 6 = 0.15 R 7 = 52.34 D 7 = 10.76 N 4 = 1.69680 ν 4 = 55.5 R 8 = 237.88 D 8 = Variable R 9 = 61.10 D 9 = 1.00 N 5 = 1.88 300 ν 5 = 40.8 R10 = 18.77 D10 = 3.80 R11 = -63.98 D11 = 0.80 N 6 = 1.80400 ν 6 = 46.6 R12 = 82.33 D12 = 3.76 R13 = -16.14 D13 = 0.80 N 7 = 1.77250 ν 7 = 49.6 R14 = 307.48 D14 = 3.20 N 8 = 1.92286 ν 8 = 21.3 R15 = -28.88 D15 = variable R16 = -26.20 D16 = 0.90 N 9 = 1.77250 ν 9 = 49.6 R17 = 29.28 D17 = 3.70 N10 = 1.80518 ν10 = 25.4 R18 = -786.13 D18 = variable R19 = ∞ (diaphragm) D19 = 2.24 R20 = -160.22 D20 = 3.88 N11 = 1.58144 ν11 = 40.8 R21 = -35.70 D21 = 0.15 R22 = 82.00 D22 = 10.11 N12 = 1.56732 ν12 = 42.8 R23 = -21.90 D23 = 1.20 N13 = 1.88300 ν13 = 40.8 R24 = -73.59 D24 = 14.87 R25 = 65.40 D25 = 9.55 N14 = 1.51112 ν14 = 60.5 R26 = -57.48 D26 = 0.15 R27 = -1739.44 D27 = 1.20 N15 = 1.88300 ν15 = 40.8 R28 = 37.25 D28 = 10.97 N16 = 1.50048 ν16 = 66.0 R29 = -64.96 D29 = 0.15 R30 = 10851.00 D30 = 1.20 N17 = 1.83400 ν17 = 37.2 R31 = 32.11 D31 = 9.89 N18 = 1.48749 ν18 = 70.2 R32 = -87.01 D32 = 0.15 R33 = 38.76 D33 = 9.25 N19 = 1.48749 ν19 = 70.2 R34 = -121.00 D34 = 2.24 R35 = ∞ D35 = 65.00 N20 = 1.51633 ν20 = 64.2 R36 = ∞

[0071]

[Table 4] (Numerical Example 2) f = 24.392 fno = 1: 2.7 2ω = 83.2 ° R 1 = 88.53 D 1 = 4.50 N 1 = 1.60311 ν 1 = 60.7 R 2 = 370.17 D 2 = 0.18 R 3 = 53.94 D 3 = 1.40 N 2 = 1.79500 ν 2 = 45.3 R 4 = 19.65 D 4 = 8.20 R 5 = 203.09 D 5 = 1.20 N 3 = 1.79500 ν 3 = 45.3 R 6 = 27.92 D 6 = 5.46 R 7 = 30.07 D 7 = 3.50 N 4 = 1.75550 ν 4 = 25.1 R 8 = 71.06 D 8 = Variable R 9 = 61.54 D 9 = 2.64 N 5 = 1.60311 ν 5 = 60.7 R10 = -101.67 D10 = 0.10 R11 = 22.82 D11 = 3.11 N 6 = 1.60311 ν 6 = 60.7 R12 = 58.31 D12 = 2.85 R13 = ∞ (aperture) D13 = 0.50 R14 = 30.59 D14 = 2.00 N 7 = 1.72000 ν 7 = 50.3 R15 = 59.93 D15 = 2.00 R16 = -52.46 D16 = 2.80 N 8 = 1.74000 ν 8 = 28.3 R17 = 21.30 D17 = 2.10 R18 = -817.73 D18 = 3.40 N 9 = 1.56732 ν 9 = 42.8 R19 = -21.19 D19 = Variable R20 = 48.17 D20 = 3.52 N10 = 1.60311 ν10 = 60.7 R21 = -74.15 D21 = 0.80 N11 = 1.64769 ν11 = 33.8 R22 = 179.87

[0072]

[Table 5] (Numerical Example 3) f = 36.03 fno = 1: 4 2ω = 62.0 ° R 1 = 159.16 D 1 = 1.80 N 1 = 1.80518 ν 1 = 25.4 R 2 = 54.76 D 2 = 7.20 N 2 = 1.58913 ν 2 = 61.2 R 3 = -143.14 D 3 = 0.20 R 4 = 41.58 D 4 = 4.20 N 3 = 1.62299 ν 3 = 58.2 R 5 = 145.13 D 5 = Variable R 6 = 689.41 D 6 = 1.30 N 4 = 1.80400 ν 4 = 46.6 R 7 = 17.42 D 7 = 5.30 R 8 = -63.26 D 8 = 1.50 N 5 = 1.80400 ν 5 = 46.6 R 9 = 152.88 D 9 = 0.10 R10 = 26.71 D10 = 4.52 N 6 = 1.76182 ν 6 = 26.5 R11 = -41.95 D11 = 0.73 R12 = -32.49 D12 = 1.30 N 7 = 1.80400 ν 7 = 46.6 R13 = 78.60 D13 = Variable R14 = ∞ (Aperture) D14 = 1.00 R15 = 35.81 D15 = 2.26 N 8 = 1.69680 ν 8 = 55.5 R16 = 384.77 D16 = 0.20 R17 = 17.43 D17 = 3.51 N 9 = 1.51633 ν 9 = 64.2 R18 = 108.32 D18 = 1.63 R19 = -33.96 D19 = 4.20 N10 = 1.75520 ν10 = 27.5 R20 = 59.14 D20 = 1.47 R21 = -25805.75 D21 = 4.27 N11 = 1.51823 ν11 = 59.0 R22 = -24.27 D22 = Variable R23 = 32.83 D23 = 4.74 N12 = 1.56732 ν12 = 42.8 R24 = -28.68 D24 = 3.10 R25 = -17.00 D25 = 1.50 N13 = 1.83400 ν13 = 37.2 R26 = -46.82 D26 = Variable R27 = -17.30 D27 = 1.65 N14 = 1.83400 ν14 = 37.2 R28 = -25.99

[0073]

[Table 6]

[0074]

As described above, according to the present invention, focusing is performed using at least two or more lens blocks (the whole lens group or a part thereof) of the lens system including the frontmost lens group. , By changing the lens block that contributes to focus depending on the zoom position or the moving ratio of the lens blocks to each other, the deterioration of aberration due to focusing due to the change of the object distance at any zoom position is minimized, and the overall object distance is reduced. Thus, it is possible to achieve a zoom lens having high optical performance over a wide range and having a small reduction in zoom ratio when focusing on a short-distance object, and an image pickup apparatus using the zoom lens.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a main part of a zoom lens of the present invention and an image pickup apparatus using the same according to a first embodiment.

FIG. 2 is a lens cross-sectional view of the zoom lens of FIG.

FIG. 3 is a wide aberration diagram of a numerical example 1 of the zoom lens of the present invention with respect to an object at infinity.

FIG. 4 is an aberration diagram of middle for an object at infinity according to Numerical Example 1 of the zoom lens of the present invention.

FIG. 5 is a telescopic aberration diagram for an object at infinity according to Numerical Example 1 of the zoom lens of the present invention.

FIG. 6 is a wide aberration diagram when the focusing according to the present invention is used for an object distance of 1 m in Numerical Example 1 of the zoom lens of the present invention.

FIG. 7 is an aberration diagram of the middle when the focusing according to the present invention is used for the object distance of 1 m in Numerical Example 1 of the zoom lens of the present invention.

FIG. 8 is a telescopic aberration diagram when the focusing according to the present invention is used for an object distance of 1 m in Numerical Example 1 of the zoom lens of the present invention.

FIG. 9 is a wide aberration diagram of the first embodiment of the zoom lens according to the present invention when the front lens is focused with an object distance of 1 m.

FIG. 10 is an aberration diagram of a middle lens of Numerical Example 1 of the zoom lens according to the present invention when the front lens is focused at an object distance of 1 m.

FIG. 11 is a telescopic aberration diagram of a front lens focus of an object distance of 1 m according to Numerical Example 1 of the zoom lens of the present invention.

FIG. 12 is a wide aberration diagram of the front lens group RF of the relay with an object distance of 1 m according to Numerical Example 1 of the zoom lens of the present invention.

FIG. 13 is an aberration diagram of a middle lens due to a relay front group RF with an object distance of 1 m in Numerical Example 1 of the zoom lens of the present invention.

FIG. 14 is a telescopic aberration diagram of a relay front unit RF with an object distance of 1 m according to Numerical Example 1 of the zoom lens of the present invention.

FIG. 15 is a schematic view of the essential portions of Embodiment 2 of the zoom lens of the present invention and an image pickup apparatus using the same.

16 is a lens cross-sectional view of the zoom lens of FIG.

FIG. 17 is a wide aberration diagram of the numerical example 2 of the zoom lens of the present invention with respect to an object at infinity.

FIG. 18 is an aberration diagram of middle for an object at infinity according to Numerical Example 2 of the zoom lens of the present invention.

FIG. 19 is a telescopic aberration diagram for an object at infinity according to Numerical Example 2 of the zoom lens of the present invention.

FIG. 20 is a wide aberration diagram when a focusing according to the present invention is used for an object distance of 50 cm in Numerical Example 2 of the zoom lens according to the present invention.

FIG. 21 is a middle aberration diagram when the focusing according to the present invention is used for an object distance of 50 cm in Numerical Example 2 of the zoom lens of the present invention.

FIG. 22 is a telescopic aberration diagram when a focusing according to the present invention is used for an object distance of 50 cm in Numerical Example 2 of the zoom lens according to the present invention.

FIG. 23 is a wide aberration diagram when focusing is performed by the third lens group with respect to an object distance of 50 cm in Numerical Example 2 of the zoom lens of the present invention.

FIG. 24 is an aberration diagram of a middle portion of the numerical value example 2 of the zoom lens of the present invention when the object distance is 50 cm and focusing is performed by the third group.

FIG. 25 is a telescopic aberration diagram when focusing is performed by the third group with respect to an object distance of 50 cm in Numerical Example 2 of the zoom lens of the present invention.

FIG. 26 is a schematic view of the essential parts of Embodiment 3 of the zoom lens of the present invention and an image pickup apparatus using the same.

27 is a lens cross-sectional view of the zoom lens in FIG.

FIG. 28 is a wide aberration diagram of the numerical example 3 of the zoom lens of the present invention with respect to an object at infinity.

FIG. 29 is an aberration diagram of middle for an infinitely distant object according to Numerical Example 3 of the zoom lens of the present invention.

FIG. 30 is a tele aberration diagram of a numerical example 3 of a zoom lens of the present invention, with respect to an object at infinity.

FIG. 31 is a wide aberration diagram when the focusing method according to the present invention is used for an object distance of 1.2 m in Numerical Example 3 of the zoom lens of the present invention.

FIG. 32 is a middle aberration diagram when a focusing method according to the present invention is used for an object distance of 1.2 m in Numerical Example 3 of the zoom lens of the present invention.

FIG. 33 is a telescopic aberration diagram when a focusing method according to the present invention is used for an object distance of 1.2 m in Numerical Example 3 of the zoom lens of the present invention.

[Explanation of symbols]

 L1 front lens group L2 variable power lens group L3 correction lens group L4 relay lens group RF relay front group RR relay rear group 1 distance detection means 2 storage means 2 control means

Claims (3)

[Claims] 1. A plurality of lens groups including a zoom lens group that moves on the optical axis for zooming and a correction lens group that corrects an image plane variation due to zooming, of the plurality of lens groups. A zoom lens characterized in that at least two lens groups including the foremost lens group are moved at different ratios according to the zoom position on the optical axis for focusing. 2. The amount of movement of the frontmost lens unit at the wide-angle end and the telephoto end when focused on an object point at a finite distance with reference to the state of focusing on an object point at infinity is X _1W and X _1T , respectively. The zoom lens according to claim 1, wherein: | X _1T |> | X _1W | 3. Distance detecting means for detecting object distance information,
Storage means for storing data required for focus corresponding to zoom position, and a plurality of lens groups including at least a zoom lens group that moves on the optical axis for zooming and a correction lens that corrects image plane variation due to zooming And using the distance information from the distance detection means and the data from the storage means, the control means changes at least two lens groups of the plurality of lens groups depending on the zoom position on the optical axis. An imaging device characterized in that it is moved at different ratios to perform focusing.