JP2002169091A - Zoom lens and photographing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that it is difficult to reduce a change in image magnification due to wobbling while securing the moderate sensitivity of a wobbling group with reference to back focus, as for a zoom lens with a automatic focusing function. SOLUTION: As for the zoom lens constituted of a 1st lens group I, a 2nd lens group II which is moved at varying the power, a 3rd lens group III for correcting the shit of an image forming position at varying the power and a 4th lens group IV for forming an image, in this order from an object side, and provided with a diaphragm SP positioned closer to the object side than the 4th lens group, the 4th lens group is constituted by arranging the wobbling group L42 which is driven in the optical axis direction at a fine amplitude so as to detect the best image forming position, and an adjusting group L43 which is fixed at the time of varying the power and at the time of detecting the best image forming position and which includes a movable part for a flange back adjustment or macro-photographing, in this order from the object side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens suitable for a television camera, a video camera, and the like, and more particularly, to wobbling a part of a relay lens group for forming an image, which is arranged on an image side of an aperture. The present invention relates to a zoom lens having a movable group for adjusting the focal length back or performing macro shooting, which is suitable for an autofocus method for searching for a focal point.

[0002]

2. Description of the Related Art In recent years, zoom lenses of television cameras have
With diversification of photographers and photographing conditions, it is required to improve operability and its simplicity and mobility. In response, demand for zoom lenses having an autofocus function has been increasing.

In general, in the case of a television camera or the like, operability and
Because of the need to ensure mobility, it is not appropriate to use an external measurement type autofocus using infrared light or the like that requires a distance measurement system to be provided separately from the imaging system.

Therefore, in a video camera or the like, a method of performing autofocus using a video signal is generally used. As an autofocus method in a video camera or the like, a method in which a part of a lens system or an imaging element is driven (wobbled) with a small amplitude in an optical axis direction to obtain a direction determination signal for autofocus (a so-called hill-climbing method). Is effective in improving the accuracy and speed of autofocus.

Here, FIG. 14 shows an optical configuration of a zoom lens having a hill-climbing type autofocus function.

In this figure, I is a first lens group movable in the optical axis direction for focusing, II is a second lens group movable in the optical axis direction during zooming, and III is an image formed during zooming. A third lens group for correcting the movement of the position, IV is a fourth lens group for imaging, Wo is a wobbling lens group, and IG is an imaging plane.

In the hill-climbing system, the strength and gradient of the video signal are detected by intentionally changing the image forming position by wobbling a part of the optical system in the optical axis direction, and the direction of the best focus is detected. In this method, focusing is performed by moving a focusing group in a direction in which focus is achieved.

For this reason, it is necessary for the optical system to be wobbled to have an appropriate sensitivity to the back focus.

On the other hand, the method of wobbling an image pickup device such as a CCD is advantageous in that a signal can be obtained irrespective of the position sensitivity of the movable lens group, but the structure is complicated in that extra driving means is required. Which is disadvantageous in terms of cost.

On the other hand, when searching for a focal point by wobbling a part of an optical system for forming an image on the image side of the stop,
Since the operation is performed by moving a relatively small and light lens group, a small driving force is required. Since the operation is performed by a group fixed to zoom, the structure is simple and the cost is advantageous.

However, when a part of the optical system is wobbled in this way, the imaging magnification changes, the imaging position of off-axis light moves, and the image quality deteriorates.

For this reason, Japanese Patent No. 2744336 discloses that
As a compact zoom lens with a small change in imaging magnification, a zoom lens that performs wobbling and focusing using a lens group closest to the image is disclosed.

[0013]

As described above, when a part of an optical system for forming an image on the image side of a stop is generally wobbled in a zoom lens, quick focusing, reduction in size and weight, and reduction in cost are realized. However, there is a drawback that the imaging magnification changes with wobbling and the image quality deteriorates. In addition, in order to obtain a direction discrimination signal for autofocus, it is necessary for the wobbling group to have appropriate position sensitivity to back focus.

That is, it is necessary to achieve both the appropriate sensitivity of the wobbling group to the back focus and the small change in the imaging magnification due to the wobbling.

In an interchangeable lens such as a television camera, a part of a lens system different from a normal focusing lens group is moved to enable a macro photographing mechanism that enables extremely close-up photographing, and a reference for mounting a lens mount. A flange back adjustment mechanism that adjusts the distance from the surface (flange) to the imaging surface by moving a part of the lens system is required.

Here, if the macro photography and the flange back adjustment mechanism are also performed in a part of the optical system for forming an image on the image side of the aperture, operability can be ensured and the size and weight can be reduced. A necessary condition is that the adjustment group also has an appropriate position sensitivity to the back focus.

However, the above-mentioned Japanese Patent No. 2744336 describes
The lens performs wobbling and focusing using the lens group closest to the image, and the lens group fixed between the focusing group and the image plane when zooming or when the best imaging position is detected, especially the flange back. It is unsuitable for providing a movable lens group for adjustment or macro photography.

It is also conceivable that the wobbling group and the movable group for performing flange back adjustment and the like are also used. However, a wobbling drive mechanism and a drive mechanism for performing flange back adjustment and the like for the lens group that is also used are considered. In addition, there arises a problem that the drive mechanism becomes complicated and operability such as flange back adjustment deteriorates.

Therefore, according to the present invention, the wobbling group and the adjustment group such as flange back are separately provided in the optical system on the image side of the stop, so that the wobbling group has an appropriate position sensitivity to the back focus. It is another object of the present invention to provide a zoom lens having a small change in the imaging magnification during wobbling and a short overall lens length.

[0020]

In order to achieve the above object, according to the present invention, in order from an object side, a first lens group,
A fourth lens group configured to correct movement of an imaging position during zooming, a second lens group that moves during zooming, and a fourth lens group that forms an image. In a zoom lens having an aperture closer to the object side than the lens group, a fourth lens group is sequentially moved from the object side to a wobbling group driven by a minute amplitude in the optical axis direction to detect a best image forming position. And an adjustment group that is fixed at the time of detection of the best imaging position and includes a movable portion for flange-back adjustment or macro photography.

That is, by separately providing a wobbling group and an adjustment group for flange back and the like as a fourth lens group for image formation on the object side of the stop, a wobbling drive mechanism and a drive mechanism for flange back adjustment and the like are provided. To improve the operability of flange back adjustment, etc., to give the wobbling group an appropriate position sensitivity to the back focus, and to reduce the change in the imaging magnification during wobbling. It realizes a zoom lens that is easy to achieve both.

Preferably, in the above-mentioned invention, in the fourth lens group, the following conditional expression is satisfied when the half width of the back focus change amplitude when the wobbling group is amplitude-driven in the optical axis direction is defined as the depth of focus. What should I do?

[0023]

(Equation 4)

Thus, the position sensitivity of the wobbling group and the adjustment group to an appropriate back focus can be ensured, and the back focus required as a product can be ensured. By reducing the size to a level at which there is no practical problem, it becomes possible to maintain good optical performance with a simple configuration while preventing image degradation during wobbling.

Preferably, in the fourth lens group,
It is preferable to satisfy the following conditional expressions.

[0026]

(Equation 5)

Thus, it is possible to maintain good optical performance with a simple configuration while guaranteeing an appropriate position sensitivity of the wobbling group to the back focus.

Further, the above-mentioned adjustment group is defined as a group a on the object side,
The b group on the image side is composed of two groups, and the b group is a movable group for flange back adjustment and macro photography.
It is preferable to satisfy the following conditional expressions.

[0029]

(Equation 6)

Thus, it is possible to maintain good optical performance with a simple configuration while guaranteeing an appropriate position sensitivity of the adjustment group to the back focus.

By specifying the optical constants of each lens group as in conditional expressions (1) to (4), it is possible to reduce the size of the entire lens system while adjusting flange back or performing macro photography. While securing the movable group, having good optical performance over the entire zoom range and all object distances,
It becomes possible to obtain a zoom lens in which the change in the imaging magnification during wobbling is small.

Note that the adjustment group may be integrally movable for flange back adjustment or macro photography.

Further, a fixed group may be arranged on the object side of the wobbling group in the adjustment group so that the size of the wobbling group can be suppressed or aberration can be corrected well.

[0034]

1 to 6 show an optical configuration of a zoom lens having an autofocus function according to an embodiment of the present invention. Note that the zoom lens according to the present embodiment is interchangeably mounted on a television camera or a video camera (photographing device), and constitutes a photographing system as shown in FIG.

In these figures, in order from the object side, I
Is the first lens group for focusing, II is the second lens group that can be moved during zooming, III is the third lens group for correcting the movement of the imaging position during zooming, and IV is for imaging. The fourth lens group, GB is a glass block such as a color separation prism,
SP is an aperture.

The first lens group I and the fourth lens group IV are fixed during zooming. The fourth lens group IV includes, in order from the object, a fixed L41 group and a wobbling group L41.
The zoom lens includes a 42 group and an L43 group (adjustment group) including a group that is fixed at the time of zooming and detection of the best imaging position and is movable for flange-back adjustment or macro shooting. .

In the zoom lens shown in FIGS. 1 to 4 and 6, the L43 group includes an object-side L43a group and an image-side L43b group.
The group is a fixed group, and the L43b group is a movable group for flange back adjustment or macro photography.

In the zoom lens shown in FIG.
The whole of the three groups is an integrally movable group (L43b group) for flange back adjustment or macro photography.

In this zoom lens, the L42 group is wobbled in the optical axis direction to obtain a direction discrimination signal for autofocus on the image forming plane. Then, based on the obtained signal, the focus group is driven to be in the best focus state.

In order to obtain a direction discrimination signal for autofocus on the image forming plane, it is necessary to appropriately shift the back focus by wobbling, and the wobbling amount is set so that the back focus is shifted by the depth of focus. Is common.

For example, in a general 2/3 type camera (image size: φ11) for broadcasting, the permissible circle of confusion is about 0.021 mm, and when the F-number is F / 2.0, the depth of focus is about 0.04 mm. These values differ depending on the image size (1/2 type, 1/3 type).

Next, the significance of the above conditional expression will be described. First, the conditional expression (1) shows a condition regarding the power of the L42 group and the L43 group. By satisfying the conditional expression (1), it is possible to maintain good optical performance with a simple configuration while ensuring appropriate position sensitivity of the L42 group and the L43 group to the flange back.

That is, when the power of the L42 group becomes unnecessarily smaller than the power of the L43 group and exceeds the upper limit of the absolute value of the conditional expression (1), the position sensitivity of the L42 group to the back focus decreases. In addition, a large driving distance is required for obtaining a direction discrimination signal for autofocus.

If the power of the lens group L43 becomes unnecessarily large with respect to the power of the lens group L42 and exceeds the upper limit of the absolute value of the conditional expression (1), the back focus required as a product can be easily obtained. It is difficult to maintain good optical performance with the configuration.

In the present embodiment and the following embodiments, the case of having the L41 group is shown.
One group is not necessary. However, by providing the L41 group, there is an advantage that the enlargement of the L42 group can be prevented and various aberrations can be satisfactorily corrected.

Next, the relationship between the paraxial refractive power arrangement and the change in image height due to wobbling (that is, the imaging magnification) will be described with reference to FIG. FIG. 7 is a schematic diagram illustrating an optical action in a lens group for image formation arranged on the image side of the stop. Here, the image height change amount Δy of the aperture center ray on the image plane when one lens group is wobbled will be considered.

The stop center chief ray passing through the stop SP is L
The lens reaches the imaging plane IG via the 41st lens group, the L42 lens group, and the L43 lens group.

Here, the height of incidence on the L41 group is h ₁ (L4
When there is no first group, h ₁ = 0), the emission angle is α ₄₂ , and L
42 groups the power phi _42, the L43 group power phi _43, L4
E ₁ a principal point interval between the first group (if L41 group is not present position of the diaphragm SP) and L42 group, e _2, principal point and the image plane of the group L43 a principal point interval between the L42 group and L43 groups The distance from the IG is s _k , the image height is y, and the wobbling displacement of the L42 group is Δ
x, when the image height change amount during wobbling is Δy, the image height change rate Δy / fw (fw is the focal length at the wide angle end of the entire system)
Generally

[0049]

(Equation 7)

Has the following relationship. Here, δ represents a difference between a distance a from the principal point position of the L42 group to the virtual image of the stop and a distance b from the principal point position of the L42 group to the virtual image of the image forming position.

As described above, the in-focus point search by wobbling requires an appropriate position sensitivity to the back focus. From conditional expressions (1) and (3), the sensitivity of the back focus Delta] s _k is generally

[0052]

(Equation 8)

Assume that

[0054] and the sensitivity Δs _k of the back focus L42
The relationship with the group displacement amount Δx is generally

[0055]

(Equation 9)

Therefore, the image height change rate Δy / when the L42 group having an appropriate back focus sensitivity is displaced.
fw is generally

[0057]

(Equation 10)

The relationship can be expressed as follows.

Here, the resolution of human vision with a visual acuity of 1.0 is said to be about 1 minute. For example, when a human looks at a 30-inch (horizontal screen size of about 50 cm) television screen from a position 2.5 m away, the horizontal viewing angle is about 680 minutes. Therefore, about 1 minute resolution is 0.1% on the screen.
Equivalent to 5%.

When the aperture is stopped down, the depth of focus becomes deeper than when the aperture is opened, and the amount of wobbling required for detecting the best focus position is also increased, so that the image height change rate is also increased. Therefore, the most frequently used F-number area is open to F /
Since the image height change rate at F / 5.6 is allowed to be up to 0.15% since the image height change rate is about 5.6, about 1/3 of that at the full aperture (F / 1.85) is about 0.06%. Become. Therefore, the upper limit of the conditional expression (2) is set so that the image height change rate when the aperture is fully opened (F / 1.85) is within 0.06% (0.15% when F / 5.6). Were determined.

However, when considering a system that frequently uses an F-number of F / 5.6 or more, or when a brighter open F-number is used.
When a number is set, the image height change rate at the time of opening the aperture needs to be suppressed to less than 0.06%.

The upper limit of the allowable image height change rate, which is represented by the conditional expression (2), varies depending on the concept of determining the wobbling amount with respect to the depth of focus, the assumed screen size, and the like. ) Falls within 0.06% or less, as shown in Table 7 below.

Conditional expression (3) relates to the power at the wide-angle end of the L42 lens group and the entire system, and is a condition for ensuring an appropriate position sensitivity to back focus and maintaining good optical performance. It is shown.

When the power of the L42 group becomes smaller than the power at the wide-angle end of the entire system and falls below the lower limit of the conditional expression (3), the position sensitivity to the back focus decreases, and the direction for autofocusing decreases. In order to obtain a discrimination signal, the amount of movement of the wobbling group must be increased, and the distance between the movable parts must be wide, which is contrary to miniaturization.

When the power of the lens group L42 is increased and exceeds the upper limit of the conditional expression (3), the position sensitivity to the back focus is increased, and the lens group L42 is mechanically moved with respect to a fixed back focus displacement. It is difficult to control the amount of displacement. In addition, it is difficult to maintain good optical performance with a simple configuration.

Conditional expression (4) indicates that the L43 group is changed to L4 on the object side.
By limiting the power of each lens unit by dividing the lens unit into two groups, a 3a group and an L43b group on the image side, the L43b group on the image side can be adjusted for flange back with appropriate position sensitivity to back focus or macro. This is for setting as a movable lens group for photographing.

If the power of the L43a group becomes larger than necessary with respect to the power of the L43b group, or if the power of the L43b group becomes smaller than necessary with respect to the power of the L43a group, the upper limit of conditional expression (4) is reduced. Beyond this, there are disadvantages in that the lens configuration for maintaining good optical performance is complicated, the position sensitivity of the L43 group to the back focus is reduced, and the distance between the movable parts is required to be large.

As described above, when the optical constants of each lens group satisfy the conditional expressions (1) to (4), it is possible to perform flange back adjustment or macro photography while making the entire zoom lens system compact. The movable L43 group is secured separately from the L42 group, which is a wobbling group, so that good optical performance can be achieved over the entire zoom range and all object distances, and a small change in the imaging magnification during wobbling. The lens has been realized.

Tables 1 to 6 show numerical examples of the zoom lens shown in FIGS. FIGS. 8 to 13 show various aberration diagrams at the wide-angle end (A) and the telephoto end (B) in the above numerical examples.

The numerical examples 1 and 8 shown in Table 1 are shown in the zoom lens of FIG. 1, and the numerical examples 2 and 9 shown in Table 2 are shown in the zoom lens of FIG. Numerical Example 3 of FIG. 3 and various aberration diagrams of FIG. 10 correspond to the zoom lens of FIG. 3, Numerical Example 4 of Table 4 and various aberration diagrams of FIG. 11 correspond to the zoom lens of FIG. 4, and Numerical Example 5 of Table 5 And FIG.
5 correspond to the zoom lens of FIG. 5, and the various aberration diagrams of Numerical Example 6 in Table 6 and FIG. 13 correspond to the zoom lens of FIG. 6, respectively.

[0071]

[Table 1] (Numerical Example 1)

[0072]

[Table 2] (Numerical example 2)

[0073]

[Table 3] (Numerical example 3)

[0074]

[Table 4] (Numerical example 4)

[0075]

[Table 5] (Numerical example 5)

[0076]

[Table 6] (Numerical example 6)

As can be seen from the numerical examples described above, according to the present embodiment, the auto-focus function having a large aperture ratio with an F-number of approximately F / 2.0, a magnification ratio of 10 times or more, and a high magnification ratio is provided. Zoom lens having the above.

Next, each of the above numerical examples and conditional expressions (1) to (5)
Table 7 summarizes the relationship with (4).

Here, in Numerical Examples 1 and 2, φ ₄₂ is positive,
Phi ₄₂ In numerical examples 3-6 is negative. In Numerical Example 5, the L43 group can be integrally moved for flange back adjustment or macro photography. Further, in Numerical Example 6, both the L43a group and the L43b group have positive power.

[0080]

[Table 7]

As described above, according to the present embodiment, the stop S
As a fourth lens group for imaging on the object side of P, a wobbling group L42 and an L43 group which is an adjustment group for flange back and the like are separately provided, so that the wobbling drive mechanism and the flange back adjustment are performed. Simplifies the drive mechanism, etc., improves operability such as flange back adjustment, and provides the L42 group with appropriate position sensitivity to the back focus, and minimizes changes in imaging magnification during wobbling. It is possible to realize a zoom lens that is easily compatible with the zoom lens.

Next, an embodiment of a photographing system (television camera system) using the zoom lenses of Numerical Examples 1 to 6 as a photographing optical system will be described with reference to FIG.

In FIG. 15, reference numeral 106 denotes a photographing system main body including a lens; 101, a photographing optical system constituted by zoom lenses of Numerical Examples 1 to 6; 102, a glass block corresponding to a filter or a color separation prism;
Denotes an image pickup device such as a CCD for receiving a subject image formed by the photographing optical system 101, and 104 and 105 denote CPUs for controlling a photographing device and a lens.

As described above, by applying the zoom lenses of Numerical Examples 1 to 6 to a photographing system such as a television camera, simplification of a driving mechanism such as a wobbling driving mechanism and a flange back adjustment, and operability such as a flange back adjustment. It is possible to realize an imaging system that can easily achieve both improvement of the wobbling group and appropriate position sensitivity to the back focus and maintenance of good optical performance.

[0085]

As described above, according to the present invention,
As a fourth lens group for imaging on the object side of the stop,
Since the wobbling group and the adjustment group for flange back adjustment or macro shooting are separately provided, the drive mechanism such as the wobbling drive mechanism and the flange back adjustment can be simplified and the operability such as the flange back adjustment can be improved. It can be. Further, it is possible to realize a zoom lens in which it is easy to make the wobbling group have an appropriate position sensitivity to the back focus and to reduce a change in the imaging magnification at the time of wobbling.

In particular, in the fourth lens group, when the half width of the amplitude of the back focus change when the wobbling group is amplitude-driven in the optical axis direction is defined as the depth of focus, the conditional expressions (1) and (2) are satisfied. If it is satisfied, the position sensitivity of the wobbling group and the adjustment group to the appropriate back focus can be guaranteed, and the back focus required for the product can be secured, and the change in the imaging magnification due to wobbling Is reduced to a level at which there is no problem in practical use, and good optical performance can be maintained with a simple configuration while preventing image deterioration during wobbling.

If the fourth lens unit satisfies the conditional expression (3), good optical performance can be obtained with a simple structure while ensuring the appropriate position sensitivity of the wobbling unit to the back focus. Can be maintained.

Further, the adjustment group is defined as a group a on the object side,
The b group on the image side is composed of two groups, and the b group is a movable group for flange back adjustment and macro photography.
By satisfying conditional expression (4), it is possible to maintain good optical performance with a simple configuration while ensuring appropriate position sensitivity of the adjustment group to the back focus. Good optical performance can be maintained.

By specifying the optical constants of each lens group as in conditional expressions (1) to (4), it is possible to reduce the size of the entire lens system while adjusting flange back or performing macro photography. While securing the movable group, having good optical performance over the entire zoom range and all object distances,
A zoom lens with a small change in the imaging magnification during wobbling can be obtained.

If a fixed group is arranged on the object side of the wobbling group in the adjustment group, it is possible to suppress the size of the wobbling group from being increased and to correct aberrations well.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an optical configuration of a zoom lens according to an embodiment (Numerical Example 1) of the present invention.

FIG. 2 is a diagram illustrating an optical configuration of a zoom lens according to an embodiment (Numerical Example 2) of the present invention.

FIG. 3 is a diagram illustrating an optical configuration of a zoom lens according to an embodiment (Numerical Example 3) of the present invention.

FIG. 4 is a diagram illustrating an optical configuration of a zoom lens according to an embodiment (Numerical Example 4) of the present invention.

FIG. 5 is a diagram illustrating an optical configuration of a zoom lens according to an embodiment (Numerical Example 5) of the present invention.

FIG. 6 is a diagram illustrating an optical configuration of a zoom lens according to an embodiment (Numerical Example 6) of the present invention.

FIG. 7 is an explanatory diagram of an optical function of a fourth lens group for forming an image in the zoom lens.

FIG. 8 is a diagram illustrating various aberrations of the zoom lens according to Numerical Example 1;

FIG. 9 is a diagram illustrating various aberrations of the zoom lens according to Numerical Data Example 2;

FIG. 10 is a diagram illustrating various aberrations of the zoom lens according to Numerical Example 3;

FIG. 11 is a diagram illustrating various aberrations of the zoom lens of Numerical Data Example 4;

FIG. 12 is a diagram illustrating various aberrations of the zoom lens according to Numerical Example 5;

FIG. 13 is a diagram illustrating various aberrations of the zoom lens according to Numerical Example 6;

FIG. 14 is a diagram illustrating an optical configuration of a zoom lens having a so-called hill-climbing type autofocus function.

FIG. 15 is a schematic diagram of a photographing system using the zoom lenses of Numerical Examples 1 to 6 as a photographing optical system.

[Explanation of symbols]

 I First lens group II Second lens group III Third lens group IV Fourth lens group SP Aperture L41 Fixed group L42 Wobbling group L43 Adjusting group L43a Fixed group L43b Movable group IG Image plane

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H044 AC01 GA01 GA24 2H087 KA03 MA01 MA12 MA18 MA19 NA09 PA15 PA16 PB20 QA02 QA07 QA17 QA21 QA25 QA32 QA34 QA42 QA45 RA32 RA41 SA21 SA23 SA27 SA30 SA32 SA63 SB05 SB05

Claims (7)

[Claims] 1. A first lens group, a second lens group that moves at the time of zooming, a third lens group that corrects the movement of an image forming position at the time of zooming, and an image forming apparatus. And a fourth lens group for detecting the best image forming position in order from the object side. The fourth lens group has a stop closer to the object side than the fourth lens group. A wobbling group that is driven with a small amplitude in the optical axis direction, and an adjustment group that is fixed at the time of zooming and detects the best imaging position and includes a movable portion for flange back adjustment or macro shooting. A zoom lens comprising: 2. In the fourth lens group, when a half width of an amplitude of a back focus change when the wobbling group is amplitude-driven in an optical axis direction is defined as a depth of focus, the following conditional expression is satisfied. The zoom lens according to claim 1, wherein: (Equation 1) 3. The zoom lens according to claim 1, wherein the fourth lens group satisfies the following conditional expression. (Equation 2) 4. The adjusting group comprises two groups, a group on the object side and a b group on the image side. The b group is a movable group for flange back adjustment and macro photography, and the following conditional expression: 4. The zoom lens according to claim 1, wherein the following condition is satisfied. (Equation 3) 5. The zoom lens according to claim 1, wherein the adjustment group is integrally movable for flange-back adjustment or macro photography. 6. The zoom lens according to claim 1, wherein a fixed group is disposed on the object side of the wobbling group. 7. A photographing system comprising: the zoom lens according to claim 1; and a photographing device to which the zoom lens is interchangeably mounted.