JPH06130281A - Zoom lens barrel - Google Patents

Abstract

PURPOSE:To prevent the error or the fluctuation of zooming caused by engaging clearance between a cam groove and a cam pin by driving a lever by actuating a cam at the point of the lever where force is applied, driving a lens frame at the point of application of the lever and pressing the lever to be unidirectionally turned by an elastic member. CONSTITUTION:The cam pin 26a planted at a position separated from the fulcrum shaft 28 of the lever 26 is engaged with the front-group cam groove 30a of a cam disk 30 so as to freely slide. The cam pin 27a planted at a position separated from the fulcrum shaft 29 of a lever supporting point 27 is engaged with the rear-group cam groove 30b so as to freely slide. Then, the levers 26 and 27 are coupled by a tension spring 32 being the elastic member at the positions which are slightly separated from the respective shafts 28 and 29. By the spring 32, the lever 26 is pressed to be turned counterclockwise and the lever 27 is pressed to be turned clockwise. Then, the pin 26a is engaged with the groove 30a and the pin 27a is engaged with the groove 30b on one side surfaces of the grooves 30a and 30b.

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 used for a camera or the like, and more particularly to a zoom lens barrel having a lens group that moves in the optical axis direction.

[0002]

2. Description of the Related Art A zoom lens barrel is generally of a so-called mechanical compensation type in which a plurality of lens groups are respectively moved in the optical axis direction to change the focal length and the angle of view for zooming. As a method of moving the lens in the optical axis direction, a lens frame holding a plurality of lens groups is supported slidably in the optical axis direction, and the lens frame is formed into a cylindrical cam barrel that rotates around the optical axis. Generally, a method of moving a plurality of types of cam grooves provided is used.

However, as a method of moving the zoom lens, instead of a cam barrel that rotates around the optical axis, a cam disk that rotates around an axis perpendicular to the optical axis and a reciprocating motion in a direction perpendicular to the optical axis. There is also a method of using a cam flat plate or a cam barrel that rotates around an axis parallel to the optical axis.

In any of the zoom lens barrels described above, the lens frame is moved in the optical axis direction by the engagement of the cam groove provided in the cam barrel or the cam plate with the cam pin provided in the lens frame. The engagement requires a certain degree of clearance so that smooth sliding is performed, and the clearance causes an error or variation in the position of the zoom lens in the optical axis direction. In order to prevent this, a measure is adopted in which the lens frame is biased in the optical axis direction so that the cam pin contacts only one side wall of the cam groove. If the cam member is a resin molded product, such a measure may be provided on one side surface of the cam groove because the die for forming the cam groove may be easily removed, and the cam groove may be formed only on the other side surface. It is especially needed because it will be used as a cam.

FIG. 3 shows an example of biasing the lens frame in the optical axis direction in a two-group zoom lens often used in still cameras. In this example, a compression coil spring 3 is interposed between the lens frame 1 that holds the front lens group G1 and the lens frame 2 that holds the rear lens group G2 so that the lens frame 1 and the lens frame 2 are directed to the left and right, respectively. The cam pin 4 that is biased in the optical axis direction and is therefore implanted in the lens frame 1 is provided with the cam groove 5a for the front lens group of the cam barrel 5 that rotates around the optical axis.
The cam pin 6 that is moved in the optical axis direction by the left side surface of the lens and is planted in the lens frame 2 has a cam groove 5b for the rear lens group of the cam barrel 5.
Is moved in the optical axis direction by the right side surface of. Reference numeral 7 is a fixed barrel, and 7a and 7b are guide grooves provided in the fixed barrel 7 for guiding the lens frame 1 and the lens frame 2 in the optical axis direction, respectively.

FIG. 4 shows an example of biasing of a lens frame often used in a video camera in the optical axis direction. In this example, the lens frame 10 of the variable power lens group G3 guided in the optical axis direction by the guide bars 8 and 9 supported by the fixed barrel 7 in parallel with the optical axis.
Is urged to the left by a compression coil spring 11 interposed between the lens frame 10 and the fixed barrel 7 while being inserted into the guide bar 8. Therefore, the cam pin (not shown) implanted in the lens frame 10 is moved in the optical axis direction by the left side surface of the cam groove of the cam member (not shown).

[0007]

In the conventional method for urging the lens frame in the optical axis direction in the zoom lens barrel as described above, the position of the zoom lens in the optical axis direction changes between the long focus and the short focus. Therefore, the spring biasing force changes, and therefore the zooming driving force changes. It is common knowledge that the ratio of the natural length and the operating length of the coil spring is 3 or less. It is restricted to be smaller than that, and in particular, in the example of FIG. 4, the amount of zooming movement is restricted.
In the above example, there is a risk of interfering with the optical path.To prevent this, if the coil diameter is increased, a guide is provided, or a conical coil spring is used, the zoom lens barrel will become large and the cost will increase. Since the points of action of the spring and the cam on the lens frame are displaced in the direction perpendicular to the optical axis, the spring and the cam give a couple to the lens frame to tilt the lens frame. In the example of FIG. Clockwise, lens frame 2
Is tilted counterclockwise, and in the example of FIG. 4, the lens frame
Although the point of action of the cam on 10 is not shown, if it is outside the guide bar 8, for example, the lens frame 10 will be tilted clockwise, and the lens tilt and movement in the optical axis direction will not be disturbed. There is a problem that it is easy to occur.

The present invention has been made to solve the above-mentioned problems, and prevents zooming errors and fluctuations due to the engagement clearance between the cam groove and the cam pin, and furthermore,
The change of the zooming driving force can be reduced and the zooming movement amount can be increased, and there is no fear that the coil spring will interfere with the optical path.
An object of the present invention is to provide a zoom lens barrel in which a spring and a cam do not apply a couple to the lens frame.

[0009]

SUMMARY OF THE INVENTION According to the present invention, in a zoom lens barrel having a lens group that varies in the optical axis direction, a lens frame holding the lens group is slidably supported in the optical axis direction. , Providing a swingable lever in a plane parallel to the optical axis corresponding to the lens frame, and providing a cam member in which a cam forming surface corresponding to the lever moves parallel to the swing surface of the lever, The cam of the cam member is engaged with a position apart from the swing center of the lever, the position apart from the swing center of the lever is engaged with the lens frame, and A zoom lens barrel is characterized in that an elastic member for imparting a one-way rotational bias to the lever is connected to a position apart from each other by a small amount, and the object is achieved by this configuration.

[0010]

That is, in the zoom lens barrel of the present invention, a lever is used to move the lens frame in the optical axis direction without being directly driven by a cam, and the cam is acted on the force point of the lever to drive the lever. The lens frame is driven in the direction of the optical axis by the action point of the lever, and the elastic member connected to the lever at a position slightly apart from the fulcrum applies a unidirectional turning bias to the lever.
The problem of zooming position error and fluctuation due to the engagement clearance between the cam and the lever is eliminated, the change in the operating length of the elastic member is small and the change in the zooming driving force is small, and the amount of displacement in the optical axis direction given by the cam at the lever ratio is small. The amount of zooming movement can be changed to increase the amount of zooming movement, the elastic member does not interfere with the optical path, the cam and the elastic member do not give a couple to the lens frame, Therefore, the lens is less likely to be tilted, and the movement of the lens frame in the optical axis direction can be performed lightly.

[0011]

EXAMPLES The present invention will be described below with reference to examples of the two-group zoom lens type shown in FIGS.

1 and 2 are schematic configuration diagrams of the zoom lens barrel of the present invention at the time of long focus and short focus. In the figure, 20 is a main body exterior, 21 and 22 are guide bars fixed to the main body exterior 20 parallel to the optical axis, 23 is a lens frame holding the front group lens G1, 24 is an inner annular portion, and the lens frame 23 and helicoid It is a front group zoom frame which is screwed by a screw and is slidably engaged with the guide bars 21 and 22 by the arm portion extending from the inner annular portion to the outside to be guided in the optical axis direction. G1 can focus on the shooting distance by moving the lens frame 23 back and forth in the optical axis direction with respect to the front group zoom frame 24 with a helicoid screw. In FIG. 2, the screwing of the lens frame 23 and the front zoom frame 24 by the helicoid screw is omitted.

A guide bar 25 holds the rear lens group G2.
Lens frames 26 and 27 slidably engaged with 21 and 22 and guided in the optical axis direction are oscillated in a plane parallel to the optical axis about fulcrum shafts 28 and 29 supported by the main body exterior 20, respectively. The movable lever 30 is a cam forming surface on which the front group cam groove 30a and the rear group cam groove 30b are formed, moves in parallel to the swinging surfaces of the levers 26 and 27, that is, in the example shown in the drawing, rotates at right angles to the swinging surface. A cam disc supported by the main body exterior 20 so as to be rotatable about an axis, 31 is a pinion connected to a forward / reverse rotation motor (not shown), and meshes with the outer peripheral gear 30c of the cam disc 30 to form the cam disc 30. Rotate zooming.

A lever 26 is provided in the front group cam groove 30a of the cam disk 30.
The cam pin 26a, which is planted at a position distant from the fulcrum shaft 28, is slidably engaged, and the fulcrum shaft of the lever 27 is fitted in the rear group cam groove 30b.
A cam pin 27a planted at a position away from 29 is slidably engaged. Therefore, when the cam disk 30 is driven by the pinion 31 and pivots for zooming, the levers 26 and 27 move to the fulcrum shaft.
Performs zooming swing around 28 and 29.

The levers 26 and 27 are connected by a tension spring 32, which is an elastic member, at positions slightly separated from the fulcrum shafts 28 and 29, respectively. As a result, in the illustrated example, the lever 26 is biased to rotate counterclockwise, and the lever 27 is biased to rotate clockwise, thereby engaging the cam pin 26a with the cam groove 30a and the cam pin 27a with the cam groove. Since the engagement of 30b is engaged with one side surface of the cam groove, there is no problem of error or fluctuation of the zooming position due to the engagement clearance between the cam pin and the cam groove. Further, even if the levers 26 and 27 swing for zooming, the change in the operating length of the tension spring 32 is small, so that the change in the zooming driving force is also small. It should be noted that depending on whether the connecting position of the tension spring 32 is on the cam pins 26a, 27a side of the fulcrum shafts 28, 29 or on the opposite side, the rotational urging force applied to the levers 26, 27 can be set clockwise or counterclockwise. Needless to say.

Action pins 26b and 27b are planted at positions away from the fulcrum shafts 28 and 29 of the levers 26 and 27, respectively.
The action pins 26b and 27b are slidably engaged with slide grooves 24a and 25a provided on the front group zoom frame 24 and the lens frame 25 at right angles to the optical axes. Therefore, when the levers 26 and 27 swing for zooming as described above, the front group zoom frame 24 and the lens frame 25, which are guided in the optical axis direction, are moved in the optical axis direction. This action pin 26b, 27b and slide groove
Unlike the engagement between the cam pin and the cam groove, the engagement between 24a and 25a can easily reduce the engagement clearance because the slide groove is a linear groove, and thus the error and fluctuation in zooming movement can be reduced. Further, since the action pins 26b and 27b do not apply a couple to the front group zoom frame 24 and the lens frame 25, there is no fear of tilting the front group lens G1 and the rear group lens G2, and the zooming movement is smooth and smooth. Done.

In the illustrated example, the action pins 26b and 27b are provided with the cam groove 30.
It is planted at a position where the amount of movement of the cam pins 26a, 27a by the a, 30b in the optical axis direction is maximized to be the amount of zoom movement of the front group zoom frame 24 and the lens frame 25.
If the planting positions of b and 27b are brought closer to the planting positions of the cam pins 26a and 27a, the amount of zooming movement will be closer to the amount of movement given by the cam groove, and the planting positions of the action pins 26b and 27b will be the same.
The zooming movement amount becomes smaller than the movement amount given by the cam groove on the fulcrum shaft 28, 29 side from the planting position of a, 27a. That is, the amount of movement of the cam in the optical axis direction can be enlarged or reduced at an arbitrary ratio to obtain the amount of zooming movement.

Of course, the present invention is not limited to the two-group zoom lens structure of the illustrated example, and it is also possible to use a cam cylinder whose rotation axis is parallel to the optical axis instead of the cam disk.
In that case, the movement of the cam forming surface parallel to the lever swinging surface is the rotation around the axis parallel to the optical axis of the cam cylinder outer peripheral surface. Further, the cam is not limited to the cam groove and may be a protrusion, or the cam member may be driven manually.

[0019]

According to the zoom lens barrel of the present invention, the zooming error is not varied or fluctuated due to the engagement clearance with the cam, the change of the zooming driving force is small, the zooming movement amount can be increased, and the spring is located in the optical path. There is a remarkable effect that the cam and the spring do not interfere with each other and the lens and the spring do not couple with each other, and the lens is not tilted or zoomed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a zoom lens barrel of the present invention at a long focal length.

FIG. 2 is a schematic configuration diagram of the zoom lens barrel of the present invention at a short focus.

FIG. 3 is a sectional view of a main part of a configuration of a conventional zoom lens barrel.

FIG. 4 is a partial cross-sectional view of a conventional zoom lens barrel.

[Explanation of symbols]

 1,2,10,23,25 Lens frame G1 Front group lens G2 Rear group lens 3,11 Compression coil spring 4,6,26a, 27a Cam pin 5 Cam barrel 5a, 5b, 30a, 30b Cam groove 7 Fixed barrel 7a, 7b Guide groove 8, 9, 21, 22 Guide bar G3 Variable magnification lens group 20 Main body exterior 24 Front group Zoom frame 24a, 25a Slide groove 26, 27 Lever 26b, 27b Action pin 28, 29 Support shaft 30 Cam disk 30a Front Group cam groove 30b Rear group cam groove 32 Tension spring

Claims (1)

[Claims] 1. A zoom lens barrel having a lens group that varies in the optical axis direction, wherein a lens frame holding the lens group is slidably supported in the optical axis direction, and an optical beam corresponding to the lens frame is supported. An oscillating lever in a plane parallel to the axis is provided, and a cam member corresponding to the lever is provided so that the cam forming surface moves parallel to the oscillating surface of the lever. The lever is engaged at a position away from the swing center, and the position away from the swing center of the lever is engaged with the lens frame, and the lever is moved to a position slightly away from the swing center of the lever. A zoom lens barrel characterized in that an elastic member for imparting a unidirectional rotation bias is connected.