JP3876978B2 - Zoom lens device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens device, and more particularly to a zoom lens device that performs zooming by moving a variable power lens group and a focus correction lens group back and forth along a photographing optical axis.
[0002]
[Prior art]
Conventionally, a zoom lens apparatus for an ENG (electric news gathering) camera has been mainly used for zooming by two moving lenses, ie, a variable power lens group and a focus correction lens group. In some cases, the zoom performance is improved by three moving lens groups in which an aberration correction lens group is provided between the lens group and the focus correction lens group (see JP-A-10-142471).
[0003]
A lens barrel of such a zoom lens apparatus is provided with a cam barrel that can rotate freely. The cam barrel is engaged with each cam roller of the variable power lens group, the focus correction lens group, and the aberration correction lens group. Three cam grooves are formed. The cam roller is engaged with a rectilinear groove of a fixed cylinder disposed outside the cam cylinder through the cam groove. Therefore, when the cam barrel is rotated, the variable power lens group, the focus correction lens group, and the aberration correction lens group move back and forth in the optical axis direction by the rectilinear guide action by the cam groove and the rectilinear groove.
[0004]
FIG. 11 shows a state in which the variable power lens group 1, the aberration correction lens group 2, and the focus correction lens group 3 are positioned in front of the photographing optical axis P and the lens groups 1 to 3 are closest to each other. ing. Cam rollers 7, 8, 9 protrude from the holding frame 4 of the variable power lens group 1, the holding frame 5 of the aberration correction lens group 2, and the holding frame 6 of the focus correction lens group 3.
[0005]
FIG. 12 is a development view of the holding frame 4 of the variable power lens group 1, and three cam rollers 7 (only two are shown in FIG. 12) protrude from the holding frame 4 at equal intervals. Further, as shown in the figure, the holding frame 4 of the variable magnification lens group 1 has relief grooves 4A and 4B formed at three equal intervals (only two are shown in FIG. 12). The relief groove 4A is a relief groove of a cam roller mounting portion 5A formed on the holding frame 5 of the aberration correction lens group 2, and the relief groove 4B is a cam roller attachment portion 6A formed on the holding frame 6 of the focus correction lens group 3. This is the escape groove.
[0006]
In this way, the conventional zoom lens device forms relief grooves 4A and 4B in the holding frame 4 of the variable magnification lens group 1, and makes the movement strokes of the aberration correction lens group 2 and the focus correction lens group 3 longer. The zoom performance (aberration correction performance, focus correction performance) is improved.
[0007]
[Problems to be solved by the invention]
However, in the conventional zoom lens device, the escape grooves 4A and 4B are formed in the holding frame 4 of the variable magnification lens group 1, and therefore the cam roller attachment portion 5A and the cam roller attachment portion 6A are positioned in these relief grooves 4A and 4B. However, when the cam roller mounting portion 5A and the cam roller mounting portion 6A are separated from the escape grooves 4A and 4B, harmful rays (stray light) enter the camera side from the grooves 4A and 4B, and a ghost is generated. There was a drawback that there was. In particular, a ghost was generated by harmful rays from the escape groove 4B close to the subject side.
[0008]
The present invention has been made in view of such circumstances, and is a zoom lens device in which a relief groove for improving zoom performance is formed in a lens holding frame, and prevents the incidence of harmful rays from the relief groove. An object of the present invention is to provide a zoom lens device that can perform the above-described operation.
[0009]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention according to claim 1 is engaged with the cam groove of the cam cylinder via the cam follower by rotating the cam cylinder rotatably provided on the lens barrel. In the zoom lens apparatus that performs zooming by moving the plurality of lens holding frames that are moved along the photographing optical axis, the lens holding frame includes at least a first holding frame that holds the first moving lens and a second moving lens. A second holding frame is formed, and the first holding frame is formed with a relief groove for escaping a cam follower mounting portion formed in the second holding frame, and the relief of the first holding frame is formed. A light shielding member having a groove for allowing a part of the second holding frame to escape is attached to the outer peripheral portion of the groove.
[0010]
According to the first aspect of the present invention, since the light shielding member in which the groove for escaping only the cam follower of the second holding frame is attached to the outer peripheral portion of the clearance groove of the first holding frame, the camera is removed from the clearance groove. The amount of harmful light incident on the side can be greatly reduced.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a zoom lens device according to the present invention will be described in detail with reference to the accompanying drawings.
[0015]
FIG. 1 and FIG. 2 are side views including a partially broken view of an ENG camera zoom lens apparatus to which the present invention is applied. A lens barrel 10 of this zoom lens apparatus includes a focus ring 12, a zoom ring 14, and an iris. A ring 16 is rotatably provided. Further, in the lens barrel 10, from the left side in FIG. 1, a focus lens group (not shown), a variable power lens group (corresponding to a first moving lens) 18, an aberration correction lens group (corresponding to a third moving lens). 20, a focus correction lens group (corresponding to a second moving lens) 22, an iris and a relay lens (not shown) are provided in this order.
[0016]
The focus lens group is supported by a focus lens barrel 24 formed integrally with the focus ring 12, and the focus lens barrel 24 is supported by the lens barrel body 11 so as to be movable in the front-rear direction by a helicoid screw mechanism. Therefore, when the focus lens barrel 24 is rotated via the focus ring 12, the focus lens group moves in the front-rear direction, and focus adjustment is performed.
[0017]
The variable magnification lens group 18 is supported by a lens holding frame 26 as shown in FIGS. Three cam rollers (corresponding to cam followers: two are shown in FIG. 3) 28 project from the outer periphery of the lens holding frame 26, and these cam rollers 28 engage with the cam grooves 32 of the zoom cam barrel 30 in FIG. Combined. Further, the upper end portion of the cam roller 28 protrudes from the cam groove 32 and is engaged with the rectilinear groove 36 of the fixed cylinder 34.
[0018]
The aberration correction lens group 20 is supported by the lens holding frame 38 as shown in FIGS. Three substantially rectangular cam roller attachment portions (corresponding to cam follower attachment portions) 39 are formed at equal intervals (two locations shown in FIG. 3) on the outer peripheral portion of the lens holding frame 38, and these cam roller attachment portions 39. Each has a cam roller 40 protruding therefrom. These cam rollers 40 are engaged with the cam grooves 42 of the zoom cam barrel 30 of FIG. Further, the upper end of the cam roller 40 protrudes from the cam groove 42 and is engaged with the rectilinear groove 36 of the fixed cylinder 34.
[0019]
The focus correction lens group 22 is supported by the lens holding frame 44 as shown in FIGS. Three substantially rectangular cam roller attachment portions (corresponding to cam follower attachment portions) 45 are formed at equal intervals on the outer peripheral portion of the lens holding frame 44, and cam rollers 46 are respectively attached to these cam roller attachment portions 45. Projected. These cam rollers 46 are engaged with the cam grooves 48 of the zoom cam barrel 30 of FIG. Further, the upper end of the cam roller 46 protrudes from the cam groove 48 and is engaged with the rectilinear groove 36 of the fixed cylinder 34.
[0020]
On the other hand, the zoom cam cylinder 30 is disposed in the lens barrel 10 so as to be rotatable about the photographing optical axis. The fixed cylinder 34 is fixed to the lens barrel main body 11 via a pin 50. The zoom cam cylinder 30 is connected to the zoom ring 14 via a pin 52. Therefore, when the zoom ring 14 is rotated, the zoom cam cylinder 30 is rotated integrally with the zoom ring 14.
[0021]
When the zoom cam barrel 30 is rotated, the variable power lens group 18 is moved back and forth along the photographic optical axis by the rectilinear guide action by the cam groove 32 and the rectilinear groove 36 with which the cam roller 28 is engaged. The correction lens group 20 is also moved back and forth along the photographic optical axis by the rectilinear guide action by the cam groove 42 and the rectilinear groove 36 with which the cam roller 40 is engaged, and the focus correction lens group 22 is also engaged with the cam roller 46. It is moved back and forth along the photographic optical axis by the rectilinear guide action by the cam groove 48 and the rectilinear groove 36. With this operation, zooming is performed.
[0022]
The holding frame 26 of the variable magnification lens group 18 has relief grooves 26A and 26B as shown in FIGS. The relief groove 26A is a groove for escaping the cam roller attachment portion 39 of the lens holding frame 38 of the aberration correction lens group 20, and the relief groove 26B is a groove for escaping the cam roller attachment portion 45 of the lens holding frame 44 of the focus correction lens group 22. There are sizes corresponding to the cam roller mounting portions 39 and 45, respectively.
[0023]
Incidentally, in the zoom lens apparatus of the embodiment, the light shielding ring (corresponding to the light shielding member) 60 shown in FIG. 6 is fixed to the outer peripheral portion of the lens holding frame 26 of the variable magnification lens group 18 as shown in FIGS. Yes. The light shielding ring 60 has three grooves 62 corresponding to the cam roller 46 for allowing only the cam roller 46 of the focus correction lens group 22 to escape. Further, the light shielding ring 60 has a width in which the upper right edge 60A in FIG. 5 abuts against the cam roller 28 of the lens holding frame 26, so that approximately half of the escape groove 26A and the entire escape groove 26B (the light shielding ring 60). Except for the portion where the grooves 62 overlap).
[0024]
Therefore, according to the zoom lens device provided with such a light shielding ring 60, harmful light incident on the camera side from the escape grooves 26A and 26B is shielded by the light shielding ring 60, so that the amount of incident harmful light is greatly reduced. be able to. Further, since the groove 62 for allowing only the cam roller 46 of the focus correction lens group 22 to escape is formed in the light shielding ring 60, the movement of the focus correction lens group 22 is not hindered. The same performance as the lens device can be maintained.
[0025]
7 to 10 show a relief groove light shielding structure according to the second embodiment, and the same or similar members as the light shielding structure according to the first embodiment shown in FIGS. Are denoted by the same reference numerals, and description thereof is omitted.
[0026]
In the light shielding structure of the second embodiment, a light shielding ring 70 is slidably provided on the outer periphery of the lens holding frame 26 of the variable magnification lens group 18. A guide groove 72 parallel to the photographing optical axis is formed in the light shielding ring 70, and a guide pin 74 protruding from the outer periphery of the lens holding frame 26 is engaged with the guide groove 72. As a result, the light shielding ring 70 is moved back and forth in the direction of the photographing optical axis by the linear guide action by the guide groove 72 and the guide pin 74.
[0027]
The light shielding ring 70 is biased toward the lens holding frame 44 of the focus correction lens group 22 by a spring 76 (corresponding to a biasing means). As shown in FIGS. 7 and 8, the spring 76 is disposed between the presser ring 78 fixed to the subject side on the outer periphery of the lens holding frame 26 and the bent end portion 71 of the light shielding ring 70, and the biasing force thereof. Therefore, the light shielding ring 70 is urged in the above direction. Further, as shown in FIG. 8, the tip bent portion 71 of the light shielding ring 70 is brought into contact with the stepped portion 27 of the lens holding frame 26 by the urging force of the spring 76, so that the lens holding frame 44 of the light shielding ring 70 is directed to. The amount of movement is restricted. At this position, approximately half of the escape groove 26A of the lens holding frame 26 and the entire escape groove 26B are closed by the light shielding ring 70 (see FIG. 9). Further, a rubber ring 80 as a buffer member is attached to the peripheral portion of the light shielding ring 70 on the focus correction lens group 22 side, and the impact when the cam roller 46 of the focus correction lens group 22 contacts is absorbed.
[0028]
According to the light shielding structure configured in this way, when the cam roller mounting portion 45 on the focus correction lens group 22 side is retracted from the escape groove 26B as shown in FIG. 9, the escape grooves 26A and 26B are formed by the light shielding ring 70 as described above. The harmful rays do not enter the camera side.
[0029]
Then, when the cam roller mounting portion 45 on the focus correction lens group 22 side moves toward the escape groove 26B by the zoom adjustment operation, first, the cam roller 46 comes into contact with the rubber ring 80 of the light shielding ring 70, and the impact here. Is absorbed. Thereafter, the light shielding ring 70 is pushed by the cam roller 46 and moves in a direction to open the escape grooves 26A and 26B against the urging force of the spring 76 (see FIG. 10).
[0030]
Therefore, in the light shielding structure of the second embodiment, the relief grooves 26A and 26B are closed by the light shielding ring 70 when not shown in FIG. 9, and the relief grooves 26A and 26B are opened only when necessary as shown in FIG. Compared with the conventional zoom lens device in which the escape groove is always open, harmful rays incident on the camera side from the escape grooves 26A and 26B can be cut. Further, when necessary, the relief grooves 26A and 26B are opened, so that the movement of the focus correction lens group 22 is not hindered, so that the zoom performance can be maintained at the same level as that of the conventional zoom lens device.
[0031]
In the embodiment, the example applied to the zoom lens device for the ENG camera has been described. However, the present invention is not limited to this, and the present invention may be applied to other types of zoom lens devices such as a zoom lens device for an EFP camera. good.
[0032]
【The invention's effect】
As described above, according to the zoom lens device of the present invention, the light shielding member in which the groove for escaping the cam follower of the second holding frame is attached to the outer peripheral portion of the clearance groove of the first holding frame. Therefore, the amount of harmful light incident on the camera side from the escape groove can be greatly reduced, and ghosting can be prevented.
[0033]
In addition, according to the present invention, the light shielding member biased toward the second holding frame by the biasing means is attached to the relief groove of the first holding frame, and the relief groove is opened only when necessary. Harmful rays incident on the camera side from the escape groove can be cut, and ghosting can be prevented.
[Brief description of the drawings]
FIG. 1 is a side view including a partially broken portion of a zoom lens device for an ENG camera to which the zoom lens device of the present invention is applied. FIG. 2 is an enlarged cross-sectional view of a main part of the zoom lens device shown in FIG. FIG. 4 is a perspective view showing a configuration of a moving lens group of the zoom lens apparatus shown in FIG. 1. FIG. 4 is an enlarged sectional view of a main part of the moving lens group of the zoom lens apparatus shown in FIG. FIG. 6 is a development view of the lens holding frame of the moving lens group of the zoom lens device. FIG. 6 is a development view of a light-shielding ring attached to the outer peripheral portion of the lens holding frame of the zoom lens. FIG. FIG. 8 is an enlarged cross-sectional view of a main part showing a light-shielding ring and a spring of the zoom lens device of FIG. 7. FIG. 9 is a diagram for explaining an operation of the light-shielding ring of the zoom lens device shown in FIG. [Fig. 10] The zoom level shown in FIG. Figure 11 is a developed view of the lens holding frame of a zoom lens device shown in enlarged fragmentary cross-sectional view [12] Figure 11 of a conventional zoom lens device described the operation of the light shielding ring's device [Description of symbols]
DESCRIPTION OF SYMBOLS 10 ... Lens barrel, 18 ... Variable magnification lens group, 20 ... Aberration correction lens group, 22 ... Focus correction lens group, 26, 38, 44 ... Lens holding frame, 26A, 26B ... Relief groove, 30 ... Zoom cam cylinder, 28 , 40, 46 ... cam rollers, 32, 42, 48 ... cam grooves, 39, 45 ... cam roller mounting portions, 60, 70 ... shading rings, 76 ... springs

Claims (1)

A plurality of lens holding frames engaged with cam grooves of the cam barrel via cam followers are moved along the photographing optical axis by rotating a cam cylinder rotatably provided on the lens barrel. In a zoom lens device that performs zooming with
The lens holding frame includes at least a first holding frame holding a first moving lens and a second holding frame holding a second moving lens,
In the first holding frame, a relief groove for escaping the cam follower mounting portion formed in the second holding frame is formed,
A zoom lens device, wherein a light-shielding member having a groove for allowing the cam follower of the second holding frame to escape is attached to an outer peripheral portion of the escape groove of the first holding frame.

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