JPH0980288A - Lens barrel - Google Patents

Abstract

(57) Abstract: The rattling of the cam mechanism that has conventionally occurred when the lens group holding barrel is driven by a part of the cam mechanism that moves in the optical axis direction while rotating around the optical axis. Provided is a lens barrel in which eccentricity between a lens group held by a lens group holding barrel and a lens group held by another lens group holding barrel is suppressed. A cam mechanism (cam pin 1) for moving a second lens group holding barrel (12) inside a third lens group holding barrel (8).
8 and a cam ring 6), a coil spring 13 for removing a rattling of the cam mechanism by applying a force in the optical axis direction to the second lens group holding barrel 12, and a second force applied in the optical axis direction.
An auxiliary cylinder 9 that is rotatably fitted in the lens group holding cylinder 12 and moves in the optical axis direction while rotating inside the third lens group holding cylinder 8 by the cam mechanism, and a second lens group holding cylinder 12 And a ball 11 that reduces frictional resistance generated between the auxiliary cylinder 9 and the auxiliary cylinder 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens barrel used for a camera or the like, and more particularly to a zoom lens barrel.

[0002]

2. Description of the Related Art Conventionally, a cam mechanism for moving a lens group holding barrel inside a housing barrel, and an elastic member for removing a rattling of the cam mechanism by applying a force in the optical axis direction to the lens group holding barrel. A lens barrel including (for example, a coil spring) is known.

In the lens barrel, the slight movement of the lens group holding barrel has a great influence on the optical system. Therefore, if the operation error of the cam mechanism is reduced as described above, more accurate photographing can be performed. Like The cam mechanism generally includes a cam pin provided in the lens group holding barrel, a cam barrel for driving the cam pin, and a guide groove for guiding the cam pin driven by the cam barrel in the optical axis direction. Thus, for example, the above-mentioned cam cylinder is adapted to rotate during the zooming operation. In detail, the above-mentioned cam pin is inserted into a cam groove formed in the cam barrel, and its tip end is fitted into the above-mentioned guide groove.

When the cam barrel rotates during the zooming operation, the cam pin drives the cam barrel, and the lens group holding barrel moves together with the cam pin in the optical axis direction.
At this time, since a force in the optical axis direction due to the coil spring is applied to the lens group holding cylinder, the cam pin provided on the lens group holding cylinder is always pressed against the side wall of the cam groove. To move. In this way, if the cam pin can be moved in the cam groove without backlash, the movement locus of the lens group holding cylinder can always be made constant.

[0005]

Recently, an inner focus type zoom lens barrel has been proposed. The inner focus type zoom lens barrel has a plurality of lens group holding barrels that move straight in the direction of the optical axis during zooming, and one of the multiple lens group holding barrels described above moves around the optical axis during focusing. It is configured to move in the optical axis direction while rotating.

However, in the conventional inner focus type zoom lens barrel, since the one lens group holding barrel makes a rotational movement during the focusing operation, the lens group holding barrel is simply made of a coil spring as described above. It was not possible to press it, and the cam mechanism was not removed.

The movement of the one lens group holding barrel in the optical axis direction while rotating around the optical axis means that the lens group held in the lens group holding barrel is subjected to rotational movement. This means that, in this case, the lens group is likely to be decentered with respect to the lens group held by another lens group holding barrel. Mutual eccentricity between the lens groups causes fluctuations in optical performance depending on the shooting distance, for example, optical performance is good at infinity but deteriorates at close distance.

In view of these problems, the object of the present invention has heretofore been encountered when the lens group holding barrel is driven by a part of a cam mechanism that rotates in the optical axis direction while rotating around the optical axis. Another object of the present invention is to provide a lens barrel in which the rattling of the above-mentioned cam mechanism is removed.

A further object of the present invention is to provide a lens barrel in which decentering between lens groups is suppressed.

[0010]

According to one aspect of the present invention for achieving the above object, a cam mechanism for moving a lens group holding barrel inside a housing barrel, and an optical system for the lens group holding barrel. In a lens barrel including an elastic member that removes rattling of the cam mechanism by applying a force in the axial direction, the lens barrel is rotatably fitted to the lens group holding barrel to which the force in the optical axis direction is applied, and , Is arranged between the auxiliary barrel that moves in the optical axis direction while rotating inside the housing barrel by the cam mechanism, and the lens group holding barrel and the auxiliary barrel, and reduces frictional resistance generated between them. There is provided a lens barrel having a friction reducing member.

[0011]

DETAILED DESCRIPTION OF THE INVENTION A zoom lens barrel as an embodiment of the present invention will be described below with reference to FIG.

The fixed barrel 1 is provided with a mount portion 1a. The fixed cylinder 1 is mounted on a camera body (not shown) via a mount 1a. Outer cylinder part 1b of fixed cylinder 1
An aperture ring 2, a zooming operation ring (zoom ring) 3, and a focusing operation ring (focus ring) 4 are fitted around the outer circumference of the lens so as to be rotatable by a predetermined angle.

A cam cylinder (cam ring) 6 having a shape as shown in the figure is slidably fitted to the fixed cylinder 1. The cam ring 6 has an inner cylinder portion 6d, an outer cylinder portion 6f, a shape folded back to the outside of the inner cylinder portion 6d, and is an intermediate cylinder located between the inner cylinder portion 6d and the outer cylinder portion 6f. And a part 6e. An interlocking ring 5 is fitted between the intermediate tubular portion 6e and the inner tubular portion 1c of the fixed barrel 1. An interlocking pin 20 is implanted in the interlocking ring 5. The center portion of the interlocking pin 20 passes through the intermediate cylinder portion 6e and the outer cylinder portion 6f of the cam ring 6, respectively. Specifically, in order to allow the central portion of the interlocking pin 20 to move only in the rotational direction with respect to the cam ring 6, escape grooves are formed in the intermediate tubular portion 6e and the outer tubular portion 6f, respectively. The central portion of the interlocking pin 20 is arranged in the clearance groove. The tip of the interlocking pin 20 is engaged with a key member 21 fixed to the inner periphery of the focus ring 4. The key member 21 is a guide member for guiding the tip end portion of the interlocking pin 20 in the optical axis direction.

A cam ring 6 is provided on the inner cylinder portion 1c of the fixed cylinder 1.
A cam groove 1d is formed for moving the optical disc in the optical axis direction while rotating the optical disc around the optical axis. In the cam groove 1d, a cam pin 15 which is planted in the inner cylinder portion 6d of the cam ring 6 is slidably fitted. In the present zoom lens barrel, the cam ring 6 is moved in the optical axis direction while being rotated about the optical axis, so that zooming correction is performed for each lens group described later.

The zoom ring 3 is formed with a guide groove 3a parallel to the optical axis. The cam ring 6 is provided in the guide groove 3a.
The distal end portion of the interlocking pin 14 planted in the outer cylindrical portion 6f is slidably fitted. The central portion of the interlocking pin 14 is inserted with a clearance in a clearance groove 1g formed in the outer cylinder portion 1b of the fixed cylinder 1.

The first lens group G1 is held by the first lens group holding barrel 10. The sliding portion 10a of the first lens group holding barrel 10 includes an outer tubular portion 6f of the cam ring 6 and an intermediate tubular portion 6e.
It is located between and. A cam pin 17 is planted in the sliding portion 10a. The cam pin 17 is the cam ring 6
It is slidably fitted in a guide groove 6a formed in the outer cylindrical portion 6f parallel to the optical axis.

Further, the sliding portion 10a is formed with a cam groove 10b for moving the first lens group holding barrel 10 in the optical axis direction while rotating the first lens group holding barrel 10 around the optical axis. Cam groove 10
The cam pin 1 which is planted in the third lens group holding cylinder 8 is shown in b.
6 are slidably fitted. Third lens group G3
Are held by the third lens group holding cylinder 8.

An auxiliary cylinder 9 is slidably fitted to the inner circumference of the third lens group holding cylinder 8. The auxiliary cylinder 9 is formed with an inward flange 9a. The second lens group G2 includes
It is held by the second lens group holding barrel 12. An outer peripheral groove 12 a having a shape conforming to the outer shape of the auxiliary cylinder 9 is formed in the second lens group holding cylinder 12. The auxiliary cylinder 9 has the outer peripheral groove 1
It is attached to the second lens group holding cylinder 12 so as to be combined with 2a. That is, the third lens group holding barrel 8 functions as a housing barrel that houses the second lens group holding barrel 12 together with the auxiliary barrel 9. A part of the second lens group holding barrel 12 is slidably fitted in a guide groove 8a formed in the third lens group holding barrel 8 and parallel to the optical axis. A friction reducing member is arranged between the second lens group holding cylinder 12 and the auxiliary cylinder 9. The friction reducing member is arranged between the second lens group holding barrel 12 and the auxiliary barrel 9 so that the second lens group holding barrel 12 and the auxiliary barrel 9 are separated from each other in the optical axis direction. When the auxiliary cylinder 9 and the auxiliary cylinder 9 are in direct contact with each other in the optical axis direction, a frictional resistance lower than the frictional resistance generated between them is generated. In this embodiment, a V groove around the optical axis is formed in each of the flange 9a and the second lens group holding cylinder 12, and a plurality of rolling members (for example, plastic or metal) as friction reducing members are formed therein. Ball 11) is rotatably fitted. Of course, the friction reducing member is not limited to these rolling members. An elastic member (here, a coil spring) 13 is arranged between the second lens group holding barrel 12 and the third lens group holding barrel 8. One end of the coil spring 13 is received by the second lens group holding cylinder 12, and the other end is attached to a cylindrical portion formed on the third lens group holding cylinder 8. The coil spring 13 widens the distance between the second lens group holding barrel 12 and the third lens group holding barrel 8, that is, the second lens group holding barrel 12 receives a force toward the auxiliary barrel 9 side. In addition, these holding cylinders are urged. Even if force is applied to the second lens group holding barrel 12, the second lens group holding barrel 12 is pressed against the auxiliary barrel 9 via the plurality of balls 11 and therefore rotates together with the auxiliary barrel 9. There is nothing to do. That is, when the auxiliary barrel 9 moves in the optical axis direction while rotating, the second lens group holding barrel 12
Moves in the optical axis direction together with the auxiliary cylinder 9 without rotating around the optical axis. By doing so, the second lens group G2
Then, relative rotation with respect to the lens groups held by the other lens group holding cylinders is eliminated, and eccentricity between the lens groups is suppressed. That is, it is possible to perform accurate shooting. In addition, depending on the rolling condition of the ball 11, the second
It is considered that a strong rotational force is temporarily applied to the lens group holding barrel 12, but there is no particular problem because a part of the second lens group holding barrel 12 is guided along the guide groove 8a.

A fourth lens group holding cylinder 7 is slidably fitted to the inner circumference of the inner cylinder portion 6d of the cam ring 6. The fourth lens group G4 is held by a fourth lens group holding cylinder 7. The above-mentioned third lens group holding tube 8 is slidably fitted on the inner periphery of the fourth lens group holding tube 7. On the outer periphery of the third lens group holding cylinder 8, a convex portion 8c extending parallel to the optical axis is provided. A guide groove 7c parallel to the optical axis is formed on the inner circumference of the fourth lens group holding cylinder 7, and the convex portion 8c is
The guide groove 7c is slidably engaged. The fourth
A cam pin 22 is embedded in the lens group holding cylinder 7. The cam pin 22 is slidably fitted in a cam groove 6g formed in the cam ring 6.

A cam pin 19 is attached to the third lens group holding barrel 8.
Has been planted. The tip of the cam pin 19 is fixed to the fixed cylinder 1
Is slidably fitted in a guide groove 1f formed in the inner cylindrical portion 1c and parallel to the optical axis. The center portion of the cam pin 19 is slidably fitted in the cam groove 6c formed in the cam ring 6. An escape groove 7a is formed in the fourth lens group holding cylinder 7 so that the fourth lens group holding cylinder 7 does not restrict the movement of the cam pin 19. Cam pin 1
9 is inserted in the clearance groove 7a with a gap.

A cam pin 18 is planted in the auxiliary cylinder 9. The tip of the cam pin 18 is slidably fitted in a guide groove 5 a formed in the interlocking ring 5 and parallel to the optical axis. The center of the cam pin 18 has a cam ring 6
It is slidably fitted in the cam groove 6b formed in the. The cam groove 6b is provided with the cam pin 18 when the cam ring 6 is stationary (in a focusing operation described later).
It functions as a cam groove for moving in the optical axis direction while rotating around the optical axis. The inner cylinder portion 1c of the fixed cylinder 1
An escape groove 1e is formed in the inner cylindrical portion 1c so as not to restrain the movement of the cam pin 18. Similarly, an escape groove 8b is formed in the third lens group holding barrel 8 so that the third lens group holding barrel 8 does not restrain the movement of the cam pin 18,
An escape groove 7b is formed in the fourth lens group holding barrel 7 so that the lens group holding barrel 7 does not restrain the movement of the cam pin 18. The cam pins 18 are inserted into these clearance grooves with a gap.

Next, the operation of the present zoom lens barrel will be described.

First, the zooming operation will be described.

When the zoom ring 3 rotates, the interlocking pin 1
The cam ring 6 rotates via 4. At this time, the cam ring 6 has the cam pin 15 fitted in the cam groove 1d.
Moves in the direction of the optical axis while rotating around the optical axis.

When the cam ring 6 rotates and moves in the optical axis direction, the tip of the cam pin 19 moves along the guide groove 1f. That is, the third lens group G3 held by the third lens group holding barrel 8 moves in the optical axis direction without rotating with respect to the fixed barrel 1. The amount of movement of the third lens group G3 in the optical axis direction with respect to the fixed barrel 1 is equal to the amount of movement of the cam ring 6 itself in the optical axis direction, and the amount of light of the third lens group holding barrel 8 defined by the cam groove 6c of the cam ring 6. This is the amount of movement in the axial direction.

When the cam ring 6 moves in the optical axis direction while rotating, the cam pin 22 of the fourth lens group holding cylinder 7
Although the driving force from the cam ring 6 is applied to the third lens group holding barrel 8, the convex portion 8c of the third lens group holding barrel 8 is guided to the guide groove 7 of the fourth lens group holding barrel 7.
Since it is fitted in c, the fourth lens group holding cylinder 7
It moves in the optical axis direction without rotating with respect to the third lens group holding cylinder 8. That is, the fourth lens group G4 held by the fourth lens group holding cylinder 7 moves in the optical axis direction without rotating with respect to the fixed cylinder 1, similarly to the third lens group G3. The amount of movement of the fourth lens group G4 in the optical axis direction with respect to the fixed barrel 1 is equal to the amount of movement of the cam ring 6 itself in the optical axis direction and the light of the fourth lens group holding barrel 7 defined by the cam groove 6g of the cam ring 6. This is the amount of movement in the axial direction.

When the cam ring 6 moves in the optical axis direction while rotating, the driving force from the cam ring 6 acts on the cam pin 18 of the auxiliary cylinder 9, but the tip of the cam pin 18 is
Since it is fitted in the guide groove 5a, the auxiliary cylinder 9 moves in the optical axis direction without rotating with respect to the interlocking ring 5. The interlocking ring 5 is always stationary during the zooming operation. Since the lens group holding barrel 12 is pressed against the auxiliary barrel 9 via the ball 11 by the coil spring 13, it moves in the optical axis direction while being integrated with the auxiliary barrel 9. The amount of movement of the second lens group G2 with respect to the fixed barrel 1 in the optical axis direction is the same as the amount of movement of the cam ring 6 itself in the optical axis direction. This is the amount of movement in the axial direction.

When the cam ring 6 moves in the optical axis direction while rotating, the cam ring 6 moves with respect to the cam pin 17.
Although a force in the rotation direction is applied from the cam pin 17, the cam pin 17 is fitted in the guide groove 6a, and the cam pin 16 of the third lens group holding barrel 8 is fitted in the cam groove 10b.
The lens group holding barrel 10 moves in the optical axis direction while rotating with respect to the third lens group holding barrel 8. The third lens group holding barrel 8 is moved in the optical axis direction as described above.

That is, the moving amount of the first lens group G1 with respect to the fixed barrel 1 in the optical axis direction is the same as the moving amount of the third lens group holding barrel 8 and the cam groove 10b of the first lens group holding barrel 10.
The amount of movement of the first lens group holding cylinder 10 in the optical axis direction, which is defined by the following equation, is added.

Next, the focusing operation will be described.

When the focus ring 4 rotates, the interlocking ring 5 rotates via the key member 21 and the cam pin 20. When the interlocking ring 5 rotates, the cam pin 18 moves along the cam groove 6b of the cam cylinder 6. The cam barrel 6 is always stationary unless the zoom ring 3 rotates. That is, the auxiliary cylinder 9 moves in the optical axis direction while rotating around the optical axis along the cam groove 6b. Further, the second lens group holding cylinder 12 receives a leftward force from the coil spring 13 in the figure, but since the plurality of balls 11 are interposed between the second lens group holding cylinder 12 and the auxiliary cylinder 9, When moving in the optical axis direction while rotating around the optical axis as described above, the auxiliary tube 9 moves in the optical axis direction together with the auxiliary tube 9 while rotating the auxiliary tube 9 relative to itself (the second lens group holding tube 12). To do. Further, since the force from the coil spring 13 is indirectly applied to the auxiliary cylinder 9, the cam pin 18 moves in the cam groove 6b while being pressed against the side wall of the cam groove 6b. If the cam pin 18 moves in the cam groove 6b without rattling, the movement locus of the second lens group G2 can be made constant.

[0032]

According to the present invention, the rattling of the cam mechanism that has been conventionally generated when the lens group holding barrel is driven by a part of the cam mechanism that moves in the optical axis direction while rotating around the optical axis. You can get rid of it.

Further, according to the present invention, since the lens group holding barrel advances straight in the optical axis direction while smoothly rotating the auxiliary barrel on which the cam pin is provided, the lens barrel holding barrel holds the lens group holding barrel. The eccentricity between the lens group and the lens group held by the other lens group holding cylinder is suppressed, and the optical performance is improved.

[0034]

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a zoom lens barrel according to the present invention.

[Explanation of symbols]

1: fixed cylinder, 1a: mount part, 1b, 6f: outer cylinder part, 1c, 6d: inner cylinder part, 1d, 6b, 6c, 6
g, 10b: cam groove, 1e, 1g, 7a, 7b, 8
b: relief groove, 1f, 3a, 5a, 6a, 7c, 8a:
Guide groove, 2: Aperture ring, 3: Zoom ring,
4: focus ring, 5: interlocking ring, 6: cam ring, 6e: intermediate tube part, 7: fourth lens group holding tube,
8: 3rd lens group holding cylinder, 8c: convex part, 9: auxiliary cylinder, 9a: flange, 10: 1st lens group holding cylinder,
10a: sliding part, 11: ball, 12: second lens group holding cylinder, 12a: outer peripheral groove, 13: coil spring,
14, 20: interlocking pins, 15, 16, 17, 18,
19, 22: cam pin, 21: key member

Claims (6)

[Claims] 1. A cam mechanism for moving a lens group holding barrel inside a housing barrel, and an elastic member for applying a force in the optical axis direction to the lens group holding barrel to remove rattling of the cam mechanism. In the lens barrel described above, the lens group holding barrel to which a force in the optical axis direction is applied is rotatably fitted, and is moved in the optical axis direction while rotating inside the housing barrel by the cam mechanism. A lens barrel comprising: an auxiliary cylinder; and a friction reducing member that is disposed between the lens group holding cylinder and the auxiliary cylinder and that reduces frictional resistance generated between them. 2. The container according to claim 1, wherein the housing cylinder has a guide groove formed in the optical axis direction, and a part of the lens group holding cylinder is fitted in the guide groove. A lens barrel to be used. 3. The holding member for holding a new lens group different from the lens group, according to claim 1 or 2, wherein the elastic member includes the lens group holding cylinder and the holding portion. A lens barrel mounted between the lens group holding cylinder and the lens group holding cylinder in a direction away from the holding unit. 4. The cam mechanism according to claim 1, wherein the cam mechanism includes a cam barrel arranged outside the housing barrel and a cam pin provided on the auxiliary barrel, and the cam barrel includes: A cam groove is formed for moving the auxiliary cylinder in the optical axis direction while rotating the auxiliary cylinder inside the storage cylinder, and the cam pin is inserted into the clearance groove formed in the storage cylinder with a gap, and The lens barrel is characterized in that a tip portion thereof is fitted in the cam groove, and the escape groove has a shape that does not come into contact with the cam pin when the cam pin moves in the cam groove. 5. A focusing operation ring for performing a focusing operation, a scaling operation ring for performing a scaling operation, and a focusing operation ring according to claim 1, 2, 3 or 4. in case of,
When the cam pin is moved along the cam groove and the variable magnification operation ring is operated, the cam barrel is rotated and the cam pin that moves along with the rotation of the cam barrel is guided in the optical axis direction. And a mechanism for controlling the lens barrel. 6. The optical system according to claim 1, wherein the auxiliary cylinder and the lens group holding cylinder overlap each other when the auxiliary cylinder and the lens group holding cylinder are fitted to each other. Lens mirrors each having a guide groove formed around an axis, wherein the friction reducing member is a rolling member held by the guide groove of the auxiliary cylinder and the guide groove of the lens group holding cylinder. Cylinder.