JPH07294814A - Zoom lens having flare cutting diaphragm - Google Patents

Abstract

PURPOSE:To remove the flare component of a maximal off-axis light ray in a zoom lens having positive, negative, positive and positive refractive powers in order from the object side and a large zooming ratio and being suitable for a television camera. CONSTITUTION:The zoom lens with flare cutting diaphragm comprises at least, in order from the object side, a first lens group F of positive refractive power, a second lens group V of negative refractive power, a fixed flare cutting diaphragm A of variable diameter and a third lens group C of positive refractive power and performs zooming operation by moving the second lens group V and the third lens group C. This zoom lens is provided with a control means for controlling the diameter of the flare cutting diaphragm A so as to cut off the flare component of the lower light ray of a maximal off-axis light ray without affecting the on-axis light beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens having a zoom ratio of about 40.times. And a high-magnification zoom lens having a flare diaphragm suitable for TV cameras and the like. A flare diaphragm (variable diameter diaphragm) that shields part of the light is placed in the lens system, and the diaphragm diameter is controlled appropriately according to the magnification change to obtain good optical performance over the entire magnification range. The present invention relates to a zoom lens having a flare diaphragm.

[0002]

2. Description of the Related Art Conventionally, as a zoom lens having a high zoom ratio, a first lens group (front lens) having a positive refracting power and a focus adjustment in order from the object side has a negative refracting power and has a zooming action. A second group (variator) that moves in the optical axis direction for this reason, and a third group that has positive refractive power and moves in the optical axis direction for zooming and image plane compensation.
There are four lens groups, a group (compensator) and a fourth group having a positive refracting power and having a fixed and image forming action, and at the time of zooming from the wide-angle end to the telephoto end, the variator and the compensator are provided. Have proposed various so-called four-group type zoom lenses which are set to have an imaging magnification of -1 at the same time.

When zooming from the wide-angle end to the telephoto end, this 4-group type zoom lens forms a large amount of coma flare in off-axis rays from a zoom position slightly on the telephoto side to an intermediate zoom position from the wide-angle end. There is a property that performance is reduced.

FIG. 14 is a schematic view showing each optical element and optical path state at the wide-angle side zoom position with the aperture open, in which a large amount of coma flare is likely to occur in the above-mentioned four-group type zoom lens.

In the figure, ray tracing is performed on the on-axis F number ray, the intermediate image height on the screen, and the off-axis ray reaching the maximum image height on the screen. In the spaces of the second group and the third group, the solid line is the on-axis F-number ray, the dotted line is the off-axis ray at the intermediate image height of the screen, and the alternate long and short dash line is the off-axis ray at the maximum image height on the image.

Now, letting the center of the off-axis ray be the principal ray and the ray below it to be the lower ray, the principal ray is on the diaphragm surface B that determines the F number from the optical axis of the lens,
It passes considerably below, and in the first group and the compensator (third group), the lower ray passes through a position having a high height from the optical axis. Therefore, it receives a strong positive refracting power and is flipped up, resulting in a large amount of coma flare.

Zoom lenses having means for removing off-axis rays have been proposed in, for example, Japanese Patent Publication Nos. 51-21794 and 56-52291.

In Japanese Patent Publication No. 51-21794, a variable-diameter diaphragm fixed to a lens barrel is set between a variator and a compensator, and the size of the diameter is changed in accordance with zooming, so that an intermediate screen is displayed. Limits image-level rays.

In Japanese Examined Patent Publication No. 56-52291, a diameter-invariant moving diaphragm is provided between the variator and the compensator, and the diaphragm is moved in association with the variator, so that the lower ray in the middle part of the screen is zoomed. A zoom lens that limits a part of the above is proposed.

[0010]

Generally, in order to suppress the variation of aberrations due to zooming, especially the variation of coma flare, it is necessary to effectively remove only the flare component without affecting the axial light flux.

By the way, the aforementioned Japanese Patent Publication No. 51-21794.
Japanese Patent Laid-Open Publication No. 2002-242242 discloses that light rays having the maximum image height on the screen are not limited and only light rays having an intermediate image height is limited. However,
In a zoom lens used for a TV camera or the like, it is possible to limit only the light rays at the intermediate image height of the screen to a very small zoom area near the wide-angle end. Further, as described above, the publication does not care about the influence of coma flare caused by the lower rays of the maximum image height by the first and third groups.
Further, in the embodiment shown in the publication, since the diaphragm diameter is controlled by a mechanical plate cam, when the diaphragm is narrowed down by the diaphragm for determining the opening diameter, or when a converter or an extender is attached. It was difficult to control the aperture diameter freely. Further, in a high-magnification zoom lens for TV cameras, the amount of movement of the variator and compensator increases, so that the length of the plate cam also increases and the entire zoom lens becomes heavy in weight.

Further, in the zoom lens proposed in Japanese Patent Publication No. 56-52291, a part of the lower ray is limited over the entire zoom range by the diameter-invariant moving diaphragm as described above, so that the aberration is reduced. There is a problem in that even a well-corrected useful light beam may be limited in some cases. In addition, since a mechanical mechanism for moving the diaphragm is required, there is a problem that the mechanism becomes complicated and the weight becomes heavy.

It is an object of the present invention to eliminate coma flare at the maximum image height due to the influence of the first and third lens units having a positive refractive power component for a zoom lens having a considerably high zoom ratio.

To this end, according to the present invention, in order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, the fixed and variable flare cut diaphragm, and the third lens having a positive refractive power are arranged in this order. In a zoom lens having at least a lens group and having a flare cut diaphragm for performing zooming by moving the second lens group and the third lens group, a maximum off-axis ray of light does not affect an axial light flux. It is characterized by comprising control means for controlling the diameter of the flare cut diaphragm so as to cut the flare component of the lower ray.

Furthermore, it is an object of the present invention to find a zoom range in which the flare cut component can be reduced most desirably, and to control the aperture diameter at least within this range.

It is another object of the present invention to provide a zoom lens having a very high zoom ratio and excellent aberration correction.

Another object of the present invention is to provide a diaphragm drive system which is small and has good response.

[0018]

1 is a sectional view of a zoom lens according to the present invention and its optical path. 12 and 1
FIG. 3 is a diagram showing a part of a lens cross section and an optical path at a predetermined zoom position.

In the figure, F is a first lens group (front lens group) having a positive refractive power, which moves in the optical axis direction when focusing on a subject and is fixed during zooming. V is a second group (variator) having a negative refracting power, which moves in the optical axis direction during zooming due to the zooming effect. C is a third group (compensator) having a positive refractive power, which moves in the optical axis direction during zooming for the purpose of zooming and image plane compensation. The arrow marks the zoom locus from the wide-angle side to the telephoto side. R is a fourth lens group (relay lens) having a positive refracting power and acts as an image forming element. P is a 3P prism as a color separation optical system, and is shown as an optical block.

Here, B is an aperture diameter determining diaphragm that determines the F number of the zoom lens, and A is a variable-diameter flare cut diaphragm according to the present invention, which has at least the maximum image height in a predetermined zoom range. Part of the light (lower side) is cut.

First, the optical function of the zoom lens of the present invention will be described. In this embodiment, a zoom lens of a four-group type having four lens groups as shown in FIG.
When zooming from the wide-angle end to the telephoto side to give a high zoom ratio, the image forming magnifications of the second and third lens units are simultaneously -1.
It is moved so that it passes twice. In the zoom range from the wide-angle end to the telephoto end, the on-axis F-number light beam is not blocked, and the middle zoom range on the wide-angle side in particular

[0022]

[Outside 3] In the zoom range (1), only the portion where the aberration of the lower ray increases is shielded by the variable-diameter flare diaphragm in accordance with the zooming operation.

Next, a detailed description will be given with reference to FIGS.

FIG. 12 shows the zoom position on the wide-angle side with the aperture B open, and between the variator V and the compensator C, the lower ray 15b of the off-axis ray having the maximum image height is on-axis F.
Since it passes through the outside of the number ray 15a, only the lower ray of the off-axis ray is blocked. In the figure, the shaded portion is the portion where the lower ray is cut. In particular

[0025]

[Outside 4] In the zoom range, since the ray behaves as shown in FIG. 12, only the off-axis ray is effectively blocked.

On the other hand, FIG. 13 shows the zoom position at the start of the F drop. Since the lower ray 15b of the off-axis ray having the maximum image height passes through the inside of the axial F-number ray 15a, the off-axis ray is You cannot block light.

However, when the aperture B is narrowed down, F
When the number becomes large, or when the focal length is converted in the entire zoom range by a converter or built-in extender, etc., the heights of the on-axis ray and the off-axis ray change between the variator V and the compensator C. , When the lower ray of the off-axis ray passes outside the on-axis F-number ray,
Light can be blocked by the diaphragm A.

In particular, in this embodiment, when the aperture diameter of the flare diaphragm A is D and the axial F number light flux diameter on the surface of the aperture A is Da, the axial F number light beam is shielded at an arbitrary zoom position. In order not to do so, the condition is that D ≧ Da (1) is satisfied.

Especially, the aberration of the lower ray increases.

[0030]

[Outside 5] In the zoom range, the diameter determined by the off-axis maximum image height ray on the diaphragm A surface is Dm, and the diaphragm diameter D is Dm> D (2) while satisfying the above condition (1). To improve the performance by effectively shielding the coma flare component of off-axis rays.

As described above, since the flare component of the off-axis ray can be effectively shielded, high performance is achieved, and further, the effect of removing the flare component is positively utilized, and the variator and compensator are used. It is possible to increase the refracting power of the sweater, shorten the length of the zoom section consisting of the variator and compensator, and at the same time shorten the distance between the diaphragm B and the front lens, so that the diameter of the front lens can be reduced. The zoom lens system can be made smaller and lighter.

Next, this embodiment will be described by giving specific numerical values.

In the numerical embodiments described later, the flare cut diaphragm A is driven by electrical control, and mainly the flare component of the off-axis light rays when the diaphragm B for aperture determination is open is removed. Table 1 shows the parameters at each zoom position at this time.

In this embodiment, the focal length f = 256.6 m
Since the F drop starts at the zoom position of m, the on-axis F number luminous flux diameter gradually increases from Da = 28.0 mm at the wide-angle end to Da = 46.0 mm at the F drop start point.
At the telephoto end, Da is reduced to 35.6 mm due to F drop.

FIG. 15 shows the change in the diameter of the flare cut diaphragm A at each zoom position in this embodiment. The horizontal axis represents the focal length and the vertical axis represents the diameter on the flare cut diaphragm A surface. In the figure, the solid line is the flare cut diaphragm diameter (D), the dotted line is the F number luminous flux diameter (Da), and the dashed line is the maximum off-axis ray. Diameter of (D
m) is represented. By operating the flare cut diaphragm A in the shaded area surrounded by the dotted line and the alternate long and short dash line in the zoom range of f = 130 mm from the wide-angle end, it is possible to block only off-axis rays. In the present embodiment, the aberration of off-axis rays is particularly worse, f = 19.49 mm to f = 69.
The peripheral light amount ratio of the off-axis maximum image height is almost 50 over 78 mm.
The diameter (D) of the flare cut diaphragm A is operated so that the ratio becomes%, and at this time, when f = 19.49 mm, D = 3.
D = 32.2 mm at 1.5 mm and f = 69.78 mm
I am trying. At the wide-angle end, D = 31.5 mm, and at the F-drop start point f = 256.6 mm, the F-number luminous flux diameter (D
D = 46.0 mm equivalent to a), D> Da = at the telephoto end
There is no limit if it is 35.6 mm, but D = 4
The distance D is controlled to be 7.0 mm so that D monotonously increases from the wide-angle end to the telephoto end, whereby the electrical and mechanical diaphragm followability is improved and flare is effectively removed.

Next, a case of performing a series of processes of the control method of the aperture diameter of the aperture A will be described with reference to FIG.

In the figure, the variator V and the compensator C are supported by supporting members 18 and 19, respectively. The support members 18 and 19 are supported by the linear cam 16 and the curved cam 17, and the rotation of the curved cam 17 causes the variator V and the compensator C to move on the optical axis to perform zooming. A zoom position detecting member 22 such as a potentiometer or an encoder is provided on the curved cam 17.
Are connected, and the zoom position signal z obtained from the zoom position detection member 22 is sent to the control circuit 23.

The control circuit 23 controls the diaphragm drive member 24 such as a motor and an IG meter based on the zoom position signal z.
The rotation direction and the rotation amount are sent to the drive signal θ.

The drive member 24 is faithfully rotated and driven based on the drive signal θ, and is connected to the diaphragm mechanism 20 by a gear, a belt and the like.

The diaphragm mechanism 20 constituting the flare cut diaphragm A has a structure in which the diaphragm is opened and closed by the rotation of the rotary ring, and the diaphragm diameter is changed by the rotation of the diaphragm drive member 24.

Further, in the diaphragm control method shown in FIG.
The zoom position detecting member is connected to the supporting member 18 of the variator V or the supporting member 19 of the compensator C for detecting the position on the optical axis.
6, the zoom position signal z is sent to the control circuit 23. The subsequent processing is the same as in FIG. At this time, the movement of the variator and the compensator can be similarly applied by using an electronic cam system or the like which can be driven independently without using a mechanical member.

As described above, in this embodiment, since the aperture diameter is electrically controlled, the weight can be further reduced,
Since the change rate of the aperture diameter with respect to the zoom position can be easily and optimally converted by changing the control circuit, it becomes possible to more accurately shield the flare component of the off-axis ray.

Next, a case of performing a series of processes of another control method of the aperture diameter of the aperture A will be described with reference to FIG.

In the figure, the zoom mechanism is the same as that of the embodiment shown in FIG. 2, and a zoom position detecting member 22 such as a potentiometer and an encoder is connected to the curved cam 17, and the zoom position detecting member is connected. The zoom position signal z obtained from 22 is sent to the arithmetic circuit 27.

The arithmetic circuit 27 determines the quantity φ'for the aperture diameter.
Is calculated based on a constant relational expression φ ′ = f (z) using the zoom position signal z as a parameter, and is sent to the control circuit 23 as an aperture diameter signal φ.

The control circuit 23 controls the diaphragm drive member 24 such as a motor and an IG meter based on the diaphragm diameter signal φ.
The rotation direction and the rotation amount are transmitted as the drive signal θ.

The diaphragm drive member 24 is faithfully rotated based on the drive signal θ, and is connected to the diaphragm mechanism 20 by a gear, a belt or the like.

The diaphragm mechanism 20 constituting the flare cut diaphragm A has a structure in which the diaphragm is opened and closed by rotation.
The aperture diameter is changed by the rotation of the aperture drive member 24.

The same processing can be performed even if the zoom position detecting member is connected to the supporting member 18 of the variator V or the supporting member 19 of the compensator C as shown in FIG. The compensator can also be moved in the same manner by using an electronic cam system or the like that can be driven independently without using a mechanical member.

As described above, in this embodiment, since the aperture diameter is electrically controlled, the weight can be further reduced,
Since the rate of change of the aperture diameter with respect to the zoom position can be easily and optimally converted by changing the relational expression of the arithmetic circuit, the flare component of the off-axis ray can be blocked more accurately.

Next, a case of performing a series of processes of another control method of the aperture diameter of the aperture A will be described with reference to FIG.

In FIG. 6, the zoom mechanism is the same as that of the embodiment shown in FIG. 2, and a zoom position detecting member 22 such as a potentiometer and an encoder is connected to the curved cam 17 and the zoom position detecting member is connected. The zoom position signal z obtained from 22 is sent to the arithmetic circuit 27.

On the other hand, in the storage circuit 28 including a ROM and a RAM, the relationship between the amount φ ′ relating to the diaphragm diameter and the zoom position information z ′ is stored in association with each other.

Based on the zoom position signal z, the arithmetic circuit 27 compares and refers to the zoom position information in the storage circuit 28 to determine the amount related to the aperture diameter, and sends it to the control circuit 23 as the aperture diameter signal φ.

Based on the diaphragm diameter signal φ, the control circuit 23 controls the diaphragm driving member 24 such as a motor and an IG meter to
The rotation direction and the rotation amount are transmitted as the drive signal θ.

The diaphragm driving member 24 is faithfully rotated based on the driving signal θ and is connected to the diaphragm mechanism 20 by a gear, a belt or the like.

The diaphragm mechanism 20 constituting the flare cut diaphragm A has a structure in which the diaphragm is opened and closed by rotation.
The aperture diameter is changed by the rotation of the aperture drive member 24.

The same processing can be carried out even if the zoom position detecting member is connected to the supporting member 18 of the variator V or the supporting member 19 of the compensator C as shown in FIG. The compensator can also be moved in the same manner by using an electronic cam system or the like that can be driven independently without using a mechanical member.

As described above, in this embodiment, since the aperture diameter is electrically controlled, the weight can be further reduced,
Since the rate of change of the aperture diameter with respect to the zoom position can be easily and optimally converted by rewriting the information in the storage circuit, the flare component of the off-axis ray can be shielded more accurately.

Next, a case of performing a series of processes of the method of controlling the aperture diameter of the aperture A will be described with reference to FIG.

In the figure, the zoom mechanism is the same as that of the embodiment shown in FIG. 2, and a zoom position detecting member 22 such as a potentiometer and an encoder is connected to the curved cam 17 and the zoom position detecting member is connected. The zoom position signal z obtained from 22 is sent to the arithmetic circuit 27.

A diaphragm mechanism 2 which constitutes the diaphragm B for determining the aperture diameter.
1 has a structure in which the diaphragm is opened and closed by rotation.

The F number detecting member 29 may be a potentiometer, an encoder or the like connected to the diaphragm mechanism 21, or an auto iris signal (not shown) from the camera side, or for driving the diaphragm mechanism 21. Drive signal (not shown), that is, the F number signal F is sent to the arithmetic circuit 27.

The focal length conversion detecting member 30 determines whether or not a device such as a converter or a built-in extender (IE) that converts the focal length of the entire zoom range is used, and sends it to the arithmetic circuit 27 as a focal length conversion signal IE. is doing.

On the other hand, in the storage circuit 28 including ROM and RAM, the amount φ ′ related to the aperture diameter is associated with the zoom position information z ′, the F number information F ′, and the focal length conversion information IE ′. Remembered

In the arithmetic circuit 27, based on the output signals z, F and IE from the above three detecting members, the respective three pieces of information z ′, F ′ and IE ′ of the memory circuit 28 are compared and referred to, and thus the aperture diameter is reduced. Is calculated and sent to the control circuit 23 as a diaphragm diameter signal φ.

The control circuit 23 controls the diaphragm drive member 24 such as a motor and an IG meter based on the diaphragm diameter signal φ.
The rotation direction and the rotation amount are transmitted as the drive signal θ.

The diaphragm driving member 24 is faithfully rotated and driven based on the driving signal θ, and is connected to the diaphragm mechanism 20 by a gear, a belt or the like.

The diaphragm mechanism 20 constituting the flare cut diaphragm A has a structure in which the diaphragm is opened and closed by rotation.
The aperture diameter is changed by the rotation of the aperture drive member 24.

The same processing can be performed even if the zoom position detecting member is connected to the supporting member 18 of the variator V or the supporting member 19 of the compensator C as shown in FIG. The compensator can also be moved in the same manner by using an electronic cam system or the like that can be driven independently without using a mechanical member.

As described above, in this embodiment, since the aperture diameter is electrically controlled, it is possible to further reduce the weight,
Further, the zoom position, the F number, and the rate of change of the aperture diameter with or without the focal length conversion can be easily and optimally converted by rewriting the information in the memory circuit, so that the flare component of the off-axis ray is more effective. It is possible to block light.

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 of the i-th lens. It is the refractive index and Abbe number for the d-line of glass.

R1-r8 are front lens groups F having positive refracting power
Thus, it moves in the optical axis direction when focusing on a subject, and is fixed during zooming. r9-r15 are variators V having a negative refracting power, which move in the optical axis direction during zooming in order to perform a zooming action. r16 is a flare cut diaphragm A having a variable diameter, and r17-r26 are compensators C having positive refracting power, which move in the optical axis direction during zooming for zooming and image plane compensation. r27 is a diaphragm B that determines the F number of the zoom lens, and r28-r43 are relay lenses R having a positive refracting power, which form an image. r44-r45 are dummy glasses P such as prisms.

Table 1 shows the relationship between the F number, the focal length f, the variable distance, and the parameters of the present invention in the numerical examples.

Further, FIGS. 7 (f = 10.0 mm) and 8 (f = 1) are aberration diagrams for the e-line of the zoom lens of the numerical example.
9.49 mm), FIG. 9 (f = 69.78 mm), FIG.
(F = 256.6 mm), FIG. 11 (f = 440.0 m)
m).

In the aberration diagram, the left side from the shaded portion t is a portion shielded from light, f = 19.49 mm, 69.78.
It can be seen that the effect of removing the flare component of the lowermost ray is great near mm.

[0077]

[Outside 4]

[0078]

[Table 1]

[0079]

As described above, it is possible to eliminate the flare at the maximum image height by providing the diaphragm whose diameter changes at a specific position. Moreover, by changing the aperture diameter within a specific zoom range, it becomes easy to obtain good optical performance. Further, by providing the arithmetic circuit and the storage circuit, the response is excellent, the mechanical parts are reduced, and the size can be reduced.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view of a zoom lens according to the present invention,
FIG. 3 is a diagram showing an optical path.

FIG. 2 is a diagram showing control of a flare stop according to the present invention.

FIG. 3 is a diagram showing control of a flare stop according to the present invention.

FIG. 4 is a diagram showing control of a flare stop according to the present invention.

FIG. 5 is a diagram showing control of a flare stop according to the present invention.

FIG. 6 is a diagram showing control of a flare stop according to the present invention.

FIG. 7 is a diagram of various types of aberration at the wide-angle end according to a numerical example of the present invention.

FIG. 8 is an intermediate diagram of the numerical example of the present invention (focal length 19.4).
9 mm) various aberration diagrams.

FIG. 9 is an intermediate diagram of the numerical example of the present invention (focal length 69.7).
8 mm) various aberration diagrams.

FIG. 10 is a diagram of various types of aberration at the F drop start point in the numerical example of the present invention.

FIG. 11 is a diagram of various types of aberration at the telephoto end according to a numerical example of the present invention.

FIG. 12 is a lens cross-sectional view on the wide-angle side for showing an optical effect of the present invention.

FIG. 13 is a lens cross-sectional view of an F drop start point for showing an optical effect of the present invention.

FIG. 14 is a lens cross-sectional view of a general zoom lens.

FIG. 15: Flare cut diaphragm A at each zoom position
Change diagram of diameter.

[Explanation of symbols]

F 1st group V 2nd group C 3rd group R 4th group IE Focal length conversion lens such as converter and built-in extender P Prism block A Flare cut diaphragm B Aperture diameter determination diaphragm (F number determination diaphragm)

Claims (7)

[Claims] 1. A first lens group having a positive refracting power, a second lens group having a negative refracting power, a fixed and variable diameter flare cut diaphragm, and a third lens group having a positive refracting power in order from the object side. In a zoom lens having a flare cut diaphragm that performs zooming by moving the second lens group and the third lens group, the flare component of the lower ray of the maximum off-axis ray is cut without affecting the axial ray bundle. A zoom lens having a flare cut diaphragm, comprising: a control unit for controlling the diameter of the flare cut diaphragm. 2. The control means at least when the zoom ratio is z. The zoom lens having the flare cut diaphragm according to claim 1, wherein the diameter of the diaphragm is controlled so as to cut the lower ray in the range. 3. The zoom lens having a flare cut diaphragm according to claim 1, wherein the second lens group and the third lens group have imaging magnifications of -1 at the same time from the wide-angle end to the telephoto end. 4. A zoom lens having a flare cut diaphragm according to claim 1, further comprising a diaphragm behind the third lens group for determining an F number. 5. The zoom lens having a flare cut diaphragm according to claim 1, wherein the control means controls the flare cut diaphragm diameter by a detection signal of the zoom position detecting means. 6. A zoom position detection means, a storage means for storing information corresponding to a diaphragm diameter of the flare cut diaphragm corresponding to each zoom position, and the zoom position detection means and the storage information of the storage means. The zoom lens having a flare cut diaphragm according to claim 1, wherein the control means controls the flare cut diaphragm diameter. 7. The flare cut aperture diameter is D, the light flux diameter determined by the axial F number ray on the flare cut aperture surface is Da, and the off-axis maximum image height ray is determined on the flare cut aperture surface. When the diameter is Dm,
Satisfying D ≧ Da in the entire zoom range, [External 2] 2. The zoom lens having a flare cut diaphragm according to claim 1, wherein the control means controls the diaphragm so that Dm> D is satisfied in the entire zoom region (z: zoom ratio).