JP2000347090A - Zoom lens barrel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens barrel where eccentricity caused by a clearance is reduced and to obtain lens barrel structure where eccentricity and backlash caused by the change of a diameter due to temperature change are reduced even in the case of using material having a different thermal expansion coefficient. SOLUTION: Three arms 4a provided in a two-group mirror chamber 4 and grooves 2b provided in a cam barrel 2 having a cam groove 2c for zooming and corresponding to three arms 4 are coupled in a state where they can move in an optical axis direction, and a two-group moving frame 3 having projections 3c and 3d for moving and rotating the chamber 4 is provided on the outside diameter side of the chamber 4 in which a rail cam 4b is provided. Furthermore, a fixed barrel 1 having a correction cam 1c for moving and rotating the frame 3 is arranged on the outside diameter side of the frame 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens barrel for a camera, and more particularly to a zoom and focus operating mechanism of a camera zoom lens employing an inner focus system.

[0002]

2. Description of the Related Art For focusing in a conventional zoom lens, a front lens feeding system has been often used. However, for the purpose of improving the zoom ratio and shortening the shortest photographing distance, the inner focus type and the rear focus type have been used for many lenses.

[0003] In addition, in recent years, in order to reduce the size of a lens to be moved at the time of focusing and to reduce the amount of movement of the lens with the autofocusing of a camera, an inner focus type and a rear focus type have recently been proposed.

A lens of this type is disclosed in Japanese Patent Application Laid-Open No. 3-14 / 1991.
There is a method disclosed in Japanese Patent No. 4411. With this method, a compact high-magnification zoom lens can be obtained with a relatively simple configuration, and in recent years, it has become one of the mainstream high-magnification inner-focus zoom lenses ranging from wide-angle to telephoto. The applicant has also proposed a focusing method in Japanese Patent Application Laid-Open No. 7-5362 that suppresses focus fluctuation without using a complicated mechanism.

A mechanism corresponding to these is that the mirror chamber is held outside a mirror chamber incorporating a lens that moves in both focus and zoom, a moving frame having a cam to be moved, and a moving frame further outside the mirror chamber. Members such as a fixed barrel, a cam barrel, and a focus lever that are linked to the moving frame / mirror chamber are linked to each other.

Here, a general example of a recently manufactured zoom lens barrel using an inner focus is shown in FIGS.
It is shown in FIG. This is a view showing a zoom lens barrel to which a focusing method of a zoom lens disclosed in Japanese Patent Application Laid-Open No. 7-5362 by the present applicant is applied, FIG. 4 is a sectional view of the lens barrel, and FIG. It is an exploded perspective view of a part.

In FIGS. 4 and 5, reference numeral 101 denotes a fixed barrel of a lens barrel. The cam barrel 102 is fitted to the outer diameter of the barrel so as to be able to rotate and extend when the zoom ring 117 is manually zoomed. In the inner diameter, the second group moving frame 103, the third group mirror room 118, and the fourth group mirror room 119 are provided with each roller, roller shaft and fixed cylinder 101, cam cylinder 1
02 are mounted so as to be movable in the optical axis direction by the respective cam grooves. A thrust ring 105 is fitted to the outer diameter of the cam cylinder 102 so as to be able to move straight in the optical axis direction during zooming. At the left end of the thrust ring 105, a first group mirror chamber 113 and an external ring 121 are screwed.

A cover ring 120, which is an external member and is fitted with a zoom ring 117 and a scale ring 115 in a rotatable state, is screwed to the right end of the fixed cylinder 101. At the right end of the cover ring 120, a rear cylinder 122, an electrical board 114, and an auto-focus gear unit 133 are screwed.
A bayonet 123 for attaching / detaching the camera is screwed to the right end face of 22.

A focus lever 106 is fastened to the right end face of the scale ring 115 with a screw, and is linked to a focus roller 107 fastened to the second group moving frame 103 with a screw 108. The focus roller 107 is fixed to the fixed cylinder 101.
Are movably fitted in the two-group movement correction cam groove 101a provided in the second group. When the scale ring 115 is rotated by these interlocks, the second group moving frame 103 rotates and moves along the correction cam groove 101a of the fixed barrel 101.

For this reason, the cam cylinder 102 has an opening 102a for escaping the focus roller 107, and the thrust ring 105 has an opening 105a for escaping the focus roller 107.

A roller 112 is fastened to the second group mirror chamber 104 in the radial direction by a screw 111, and the roller 112 is inserted into the second group movable frame 103 in a state of being slidable with the cam groove 103 a. The second group mirror chamber 104 is rotated at the time of zooming on the left side of the second group mirror chamber 104 so that the cam groove 103a is formed.
And an interlocking lever 109 for moving in the optical axis direction by the action of the roller 112 is fastened by a screw 110, and the cam cylinder 1
02 is fitted in the vertical groove 102b.

In the above structure, when performing a focusing operation, first, the photographer manually rotates the scale ring 115 by an appropriate amount. As a result, the focus lever 106 screwed to the scale ring 115 is moved along the correction cam groove 101a of the fixed cylinder 101 with the focus roller 107 and the second group moving frame 103 screwed to the focus roller 107 screwed around the optical axis. It moves in the optical axis direction while rotating.

At this time, the second group mirror room 104 is
09 and the vertical groove 102b of the cam cylinder 102 cannot be rotated, so that it moves straight in the optical axis direction by the action of the roller 112 and the cam groove 103a provided in the second group moving frame 103. Focusing becomes possible by these actions. 2
Groups other than the group do not operate during focusing.

At the time of autofocusing, the photographer presses a shutter button of a camera (not shown), whereby the motor of the camera rotates the gear unit 133 for autofocus, and this rotates the scale ring 115 by an appropriate amount by gearing. Subsequent operations are the same as those in the manual focus.

Next, when performing a zoom operation, first, the photographer manually rotates the zoom ring 117 by an appropriate amount. As a result, the cam cylinder 102 moves in the optical axis direction while rotating by the projection 102e of the cam cylinder 102 interlocked with the zoom ring 117. By this rotation, the vertical groove 102b of the cam cylinder 102 and the interlocking lever 109 are connected, and the second group mirror room 10 is connected.
4 rotates. As a result, the second group mirror chamber 104 moves in the optical axis direction while rotating by the action of the cam groove 103a and the roller 112 provided in the second group moving frame 103. The first group mirror room 113 of the other group, the third group mirror room 118, and the fourth group mirror room 119 include the vertical grooves 101b and 101c of the fixed tube 101 and the cam tube 102.
The cam grooves 102c and 102d, the cam groove 105b and the vertical groove 105c of the thrust ring 105, and the respective rollers move linearly in the optical axis direction.

[0016]

However, in these inner focus structures, only the two groups used for focusing are required to be fixed to the fixed cylinder and the cam cylinder which are the zoom operating members.
There is a problem that eccentricity tends to occur with respect to other lenses due to the inclusion of a group moving frame.

In the reference example shown in FIGS.
Since the screw is fastened to the thrust ring 105 directly fitted to the screw 02, there is little eccentricity due to the clearance. Also,
The thrust ring 105 itself has a sufficient fitting width with the cam cylinder 102, so that problems such as torsion are unlikely to occur.
The fourth group is hardly eccentric because it is linked directly by the rollers fastened to each moving frame. However, the second group has a second-group moving frame 103 between the second-group mirror room 104 and the fixed barrel 101, and the portion that guarantees the positional accuracy of the second-group mirror chamber 104 is the fixed barrel 101 like the third and fourth groups. Is not determined by the vertical groove of the cam cylinder 102 and the cam groove of the cam cylinder 102,
03 is prevented by the cam groove 103a and the roller 112, and the eccentricity is prevented by the accuracy and width of the fitting diameter of the second group mirror chamber 104 and the second group moving frame 103. Moreover, the second group mirror room 104
And the fitting diameter of the second group moving frame 103 is a portion that rotates and slides during focusing. Therefore, in order to prevent a load on the motor, the gear unit, and the like during autofocusing, it is necessary to set the sliding surface to rotate lightly, and a certain amount of play is inevitable. Especially the second group mirror room 10
4. If plastic is selected as the material of the moving frame 103 for the second and third groups, it is necessary to partially set the diameter of both sliding portions to correct concentricity and roundness, and the sliding surfaces are no longer in full contact. In addition, play is more likely to occur.

The second group mirror room 104, the second group moving frame 10
3. If the fixed cylinder 101 is made of a material having a different coefficient of thermal expansion, a change in diameter due to a change in temperature must be added to the clearance, and eccentricity and play are easily generated. This eccentricity and play degrade the optical performance of the lens, and further cause image blurring and image skipping in the focus / zoom operation.

These problems limit the setting of the diameter and material of the mirror chamber and the moving frame, and have been a major obstacle to improving accuracy and reducing cost.

[0020]

In order to solve the above problems, in the present invention, in an inner focus zoom lens, the position accuracy of two groups moving both in zoom and focus is determined by a cam, a protrusion, and three vertical positions. By holding at two places of the groove and the arm, eccentricity is hard to occur, and even if many inexpensive and high-productivity plastic parts are used, even if members having different thermal expansions are used, it is hardly affected by temperature shrinkage.
A group cam structure can be obtained.

Further, the fixed cylinder, the second group moving frame, and the second group mirror chamber are made of plastic, and the correction cam of the fixed cylinder is moved to the convex cam, and the rail cam of the second group moving frame is moved to the outer diameter of the second group mirror chamber to be a convex cam. By providing two projections for sandwiching the respective cams on the second group moving frame, rollers, roller mounting screws and the like can be omitted, and a two-group cam structure with a small number of parts can be obtained.

Further, as shown in the conventional example, the apertures 102a and 105a shown in FIG. 5 show that the interlocking movement of the second group moving frame during focusing is performed by a focus lever passing through a radial gap between the fixed cylinder and the cam cylinder. There is no need to open such a large opening in the cam cylinder and the thrust ring, and the accuracy and strength of the parts can be greatly improved.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a zoom lens barrel according to the present invention, a moving frame for holding and moving a lens which moves in both focus and zoom is provided on an inner diameter of a fixed barrel, and a moving frame is provided on the inner diameter of the moving frame. The mirror chamber of the lens is incorporated, and furthermore, a plurality of arms are provided in the mirror chamber, and the arm and the vertical groove of the cam cylinder fitted to the outer diameter of the fixed cylinder are interlocked to reduce the center accuracy of the mirror chamber. It can be obtained directly from the cam barrel by the fitting accuracy of the arm section of the mirror chamber and the vertical groove of the cam barrel. It is possible to obtain a structure that does not easily cause backlash.

Thus, for example, the mirror chamber, the moving frame, and the fixed cylinder are made of plastic, and the sliding diameter of each of them is partially corrected. In addition, even when the mirror chamber is made of plastic and the moving frame is made of metal, it is possible to provide a margin without causing eccentricity and play in the diameter clearance between the mirror chamber and the moving frame. It is possible to obtain a lens barrel that can maintain the focus and zoom operation even if it becomes large due to thermal expansion.

Further, the member for moving the moving frame to the scale ring is passed between the fixed cylinder and the cam cylinder, and the lever is moved from the rear end side of the fixed cylinder to provide a large opening in the cam cylinder and the thrust ring. Disappears,
The accuracy, strength, and productivity of the cam cylinder and thrust ring can be greatly increased.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a zoom lens barrel according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a zoom lens barrel according to the present invention, and FIG. 2 is an exploded perspective view of the zoom lens barrel.

In FIGS. 1 and 2, reference numeral 1 denotes a fixed barrel of the lens barrel. The cam barrel 2 is fitted on the outer diameter of the barrel so that the cam barrel 2 can be rotated and extended when the zoom ring 17 is manually zoomed. The second-group moving frame 3, the third-group mirror chamber 18, and the fourth-group mirror chamber 19 are incorporated in the inner diameter so as to be movable in the optical axis direction by the rollers, the roller shaft and the cam grooves of the fixed cylinder 1 and the cam cylinder 2. ing. Cam cylinder 2
The thrust ring 5 is fitted to the outer diameter of the lens so that it can move straight in the optical axis direction during zooming. Thrust ring 5
The first group mirror room 10 and the appearance ring 21 are screwed to the left end of the lens.

At the right end of the fixed cylinder 1, a cover ring 20, which is an external member, into which the zoom ring 17 and the scale ring 15 are rotatably fitted, is fastened with screws. The right end of the cover ring 20 is screwed with a rear barrel 14, an electrical board 12, and an autofocus gear unit 13, and the right end face of the rear barrel 14 is screwed with a bayonet 11 for attaching and detaching a camera. ing.

A focus lever 6 is fastened to the right end surface of the scale ring 15 with a screw, and a focus lever 7 fastened to the second group moving frame 3 with a screw 8 is connected thereto. To tell. At this time, the fixed cylinder 1 is provided with a relief 1a and a slit 1b for the focus lever 7. A correction cam 1c for moving the second group moving frame 3 at the time of focusing is formed in the inner diameter of the fixed cylinder 1 in a convex shape.
It is connected to the seed projections 3a, 3b.

Two types of projections 3c and 3d are also formed on the inner diameter of the second group moving frame 3, and are connected to a convex rail cam 4b provided on the outer diameter of the second group mirror chamber 4. In the second group mirror chamber 3, three arms 4a are formed so as to be separated by 120 degrees, and are connected to the three vertical grooves 2b of the cam barrel 2 so as to be slidable in the thrust direction.

In the above structure, when performing a focusing operation, first, the photographer manually rotates the scale ring 15 by an appropriate amount. As a result, the focus lever 6 screwed to the scale ring 15 becomes the focus lever 7,
The focus lever 7 moves the second group moving frame 3 to which the screw is fastened in the optical axis direction while rotating along the correction cam 1c of the fixed barrel 1 around the optical axis.

At this time, the second group mirror chamber 4 cannot be rotated because the arm 4a is connected to the vertical groove 2b of the cam barrel 2, and the rail cam 4b provided on the outer diameter of the second group mirror chamber 4 and the second group moving frame 3 Move linearly in the optical axis direction by the action of the projections 3c and 3d provided on the inner diameter of. Focusing becomes possible by these actions. The other lens groups do not operate during focusing.

At the time of auto-focusing, the photographer presses a shutter button of a camera (not shown), whereby the motor of the camera rotates the gear unit 13 for auto-focusing, and this rotates the scale ring 15 by an appropriate amount by gearing. Subsequent operations are the same as described above.

Next, when performing a zoom operation, first, the photographer manually rotates the zoom ring 17 by an appropriate amount. As a result, the projection 2a of the cam barrel 2 interlocked with the zoom ring 17
As a result, the cam barrel 2 moves in the optical axis direction while rotating.
By this rotation, the second group mirror chamber 4 is rotated by the connection between the vertical groove 2b of the cam cylinder 2 and the arm 4a of the second group mirror chamber 4. As a result, the second group mirror chamber 4 rotates and moves in the optical axis direction by the action of the projections 3c and 3d provided on the inner diameter of the second group movable frame 3 and the rail cam 4b of the second group mirror chamber 4. Other group 1
The group mirror room 10, the third group mirror room 18, and the fourth group mirror room 19 include the vertical grooves 1d and 1e of the fixed barrel 1 and the cam grooves 2c, 2d and 2e of the cam barrel 2.
Due to the action of the vertical groove 5a of the thrust ring 5 and each roller, each of the rollers moves straight in the optical axis direction. Zooming becomes possible by these actions.

FIG. 3 is a sectional view of a zoom lens barrel according to another embodiment. In the figure, 201 is a fixed cylinder, 202 is 2
A group moving frame 203 is a focus lever. The fixed cylinder 2
01, no slit is provided, and the focus lever 203 passes through the left end face side of the fixed barrel 201 to move the second group moving frame 202
Are connected by screws 204. The configuration and operation of the other parts are the same as in the embodiment shown in FIG.

[0037]

As described above, in the zoom lens barrel according to the present invention, eccentricity and backlash are less likely to occur, and inexpensive and highly productive plastic parts can be used in many cases. It has become possible to obtain a two-group cam structure that is not easily affected by shrinkage.

Further, the interlocking movement of the second group moving frame 3 at the time of focusing is performed by a focus lever passing through a radial gap between the fixed cylinder 1 and the cam cylinder 2 so that a large opening is formed in the cam cylinder and the thrust ring. There was no need to open it, and the precision and strength of the parts could be greatly improved.

In this embodiment, the correction cam and the rail cam have convex shapes, but may have a concave shape or a through groove shape. It goes without saying that there is no problem even if the cam provided in the second group mirror room is moved to the second group moving frame side.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zoom lens barrel to which the present invention is applied.

FIG. 2 is an exploded perspective view of each part near the second group in FIG.

FIG. 3 is a sectional view of a zoom lens barrel according to another embodiment to which the present invention is applied.

FIG. 4 is a cross-sectional view of a general lens barrel of a zoom lens barrel using inner focus.

FIG. 5 is an exploded perspective view of each part near the second group in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed cylinder 2 Cam cylinder 3 2nd group moving frame 4 2nd group mirror room 5 thrust ring 7 Focus lever 10 1st group mirror room 11 Bayonet 14 Rear tube 15 Scale ring 17 Zoom ring 18 3rd group mirror room 19 4th group mirror room 20 Cover Ring 21 Exterior ring 101 Fixed cylinder 102 Cam cylinder 103 Second group moving frame 104 Second group mirror room 105 Thrust ring 106 Focus lever 109 Interlocking lever 115 Scale ring 117 Zoom ring 118 Third group mirror room 119 Fourth group mirror room 122 Rear tube 201 Fixed Cylinder 202 2nd group moving frame 203 Focus lever

Claims (2)

[Claims] 1. A zoom lens barrel having a plurality of lenses and a plurality of mirror chambers for holding the lenses, wherein a movement amount of the focus lens during focusing changes with a change in focal length due to zooming. A plurality of arms provided in a focus lens mirror chamber having a cam and a plurality of grooves corresponding to the plurality of arms provided in a cam barrel having a cam for zooming are movable in the optical axis direction. A moving frame having a cam interlock mechanism for moving and rotating the focus lens chamber is connected to the outside of the focus lens chamber, and the cam interlock moves and rotates the moving frame outside the moving frame. A zoom lens barrel comprising a fixed cylinder having a mechanism. 2. The zoom lens barrel according to claim 1, wherein the focus lever performs interlocking operation of the focus lens chamber through a radial gap between the fixed barrel and the cam barrel.