JPH0289012A - Lens barrel for zoom lens - Google Patents

Abstract

PURPOSE:To compactly constitute a lens barrel by providing a driving cam for driving to move forward and backward a second lens group supporting frame in the optical axis direction relatively against a first lens group supporting frame so that each lens group can be interlocked and moved, while controlling an interval between each lens group at the time of zooming. CONSTITUTION:By rotating a driving ring 22, a first lens group supporting frame 3 is driven to move forward and backward in the optical axis direction, a first lens group 1 is transferred out or transferred in, and simultaneously, a driving cam fitted and attached to the first lens group supporting frame 3 is driven to rotate by a motion of the driving ring 22. As a result, by interlocking with the movement of the frame 3, a second lens group supporting frame 4 moves forward and backward relatively in the optical axis direction against the frame 3. Accordingly, while zooming is executed, an interval between first and second lens groups 1, 2 is determined by only a rotation angle of a driving cam cylinder 10. Also, a guide pin 13 provided projectingly on the frame 4 is always pressed against the driving cam by an energizing means 14. In such a way, the interval between the lens groups is controlled with high accuracy without being varied.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a zoom lens barrel in an optical machine such as a camera, and particularly relates to an improvement in a mechanism for zooming by moving a plurality of lens groups in conjunction with each other. It is something.

[Prior Art] To perform zooming, it is necessary to move a plurality of lens groups in the optical axis direction in conjunction with each other by different amounts.

Therefore, conventionally, as shown in FIG.
A first support frame 52 that supports the lens group 51 and a second support frame 54 that supports the second lens group 53 are respectively disposed so as to be movable only in the optical axis direction, and each support frame 52.5
4 with guide pins 57 and 58 protruding, and one drive ring 59.
The guide pins 57 and 58 were engaged with two cam grooves so and st formed in the cam grooves so and st. And the drive ring 59
By rotating the first and second lens groups 51.
53 is moved in the optical axis direction together with each of the support frames 52 and 54 by different amounts.

[Issues to be Solved by the Invention] In recent years, zoom lenses used in cameras and the like are required to have contradictory performances such as increasing the zoom ratio and making the device more compact. As a result, the optical system has become highly sensitive, and a slight deviation in the distance between the lens groups causes a large deviation in the focus position.

Therefore, in a zoom lens barrel, it is necessary to control the position of each lens group with much higher precision than before.

However, in the conventional zoom lens barrel as described above, there are clearances between the two cam grooves 60 and 61 and the guide pins 57 and 58, and the clearance is equal to the distance between the two lens groups 51 and 53. Therefore, there is a drawback that the distance between the lens groups 51 and 53 changes each time a zooming operation is performed, and the focal plane shifts.

Also, cam grooves 60.6 for driving each lens group 51.53.
1 were all formed in one driving ring 59, so the total length of the driving ring 59 was determined by the amount of movement of each lens group, and as the zoom ratio became higher, the amount of movement of the lens groups increased. It has been extremely difficult to make a zoom lens barrel compact.

This invention eliminates such drawbacks of the conventional technology, allows each lens group to move in conjunction with each other while controlling the distance between each lens group with high precision during zooming, and also makes the lens barrel compact. It is an object of the present invention to provide a zoom lens barrel that can be configured.

[Means for Solving the Problems] In order to achieve the above object, the zoom lens barrel of the present invention is a zoom lens barrel that performs zooming by moving a plurality of lens groups in conjunction with each other by different amounts in the optical axis direction. In the tube,
a first lens group support frame that supports a first lens group; and a second lens group support frame that supports a second lens group and is supported by the first lens group support frame so as to be movable relative to the optical axis direction. a lens group support frame, a drive ring that is rotatably provided around the optical axis and drives the first lens group support frame forward and backward in the optical axis direction, and a drive ring that is rotatable around the optical axis and drives the first lens group support frame. a drive cam fitted on the group support frame and rotationally driven by the drive ring to drive the second lens group support frame forward and backward in the optical axis direction relative to the first lens group support frame; It is characterized by having been established.

Further, a guide pin may be protruded from the second lens group support frame, and biasing means may be provided to constantly press the guide pin against the drive cam, so that the two lens groups are connected to the lens barrel. The first lens group may be further moved in the retracting direction from the state where the combined focal length is shortest by retracting the first lens group so that it can be housed in the lens barrel.

[Operation 1] By rotating the drive ring, the first lens group support frame is driven forward and backward in the optical axis direction, and the first lens group is extended or retracted. At the same time, the drive cam fitted to the first lens group support frame is rotationally driven by the movement of the drive ring.

As a result, in conjunction with the movement of the first lens group support frame, the second lens group support frame moves relative to the first lens group support frame in the optical axis direction. Zooming is performed in this way, during which the distance between the first and second lens groups is
It is determined only by the rotation angle of the drive cam cylinder. Also,
Since the guide pin protruding from the second lens group support frame is constantly pressed against the drive cam by the biasing means, the distance between the lens groups does not vary and is controlled with high precision.

[Example] Examples will be described with reference to the drawings.

Figures 1 and 2 show a zoom lens barrel with the focal length shortest due to zooming, and Figure 3 is a front cross-section showing the combined positional relationship of the cam grooves and guide pins. It is a diagram. In each of the drawings, different cross-sectional views are combined into one drawing for ease of explanation.

In the figure, 1 is a first lens group with a small amount of movement, and 2 is a second lens group with a large amount of movement. These lens group 1
．． Although each lens 2 is schematically shown as one lens in the figure, each lens can be composed of a plurality of lenses.

3 is a first lens group support frame that supports the first lens group, and 4 is a second lens group support frame that supports the second lens group. An autofocus unit 5 is fixed to the first lens group support frame 3, and the first lens group l is disposed within a helicoid ring 6 that is threadedly engaged with the autofocus unit 5.
is fixed. The first lens group 1 is driven in the optical axis direction by an autofocus unit 5 for one focus. That is, in this embodiment, the autofocus unit 5 rotates the operating pin 5a around a predetermined foremost axis in accordance with the shooting distance, and the first lens group 1 is rotated by the engaging piece 6a that engages with it. is thus the first
The lens group l is supported by the first lens group support frame 3 via the autofocus unit 5 and the helicoid ring 6, but the first lens group 1 is directly supported by the support frame 3. It's okay.

7 is a cover fixed to the first lens group support frame 3 with screws; 8 is a barrier device that moves to the front of the first lens group l to protect the lens surface when the camera is used.

A three-wooden rod 15 is fixedly installed in the rear half of the first lens group support frame 3 in parallel with the optical axis.

The second lens group support frame 4 engages with the rod 15 through the engagement hole 4a and is supported slidably in the optical axis direction. That is, the second lens group support frame 4 is supported by the first lens group support frame 3 so as to be relatively movable in the optical axis direction.

Inside the first lens group support frame 3, there is a drive cam barrel l that moves the second lens group support frame 4 relative to the first lens group support frame 3 in the optical axis direction.

is fitted so as to be rotatable around the optical axis. In this embodiment, the drive cam barrel 10 is rotated by 90 degrees.
The lens group support frame 3 is cut out. 3a is the notch portion. Reference numeral 11 denotes a cam surface of the drive cam cylinder 10, and a developed view thereof is shown in FIG.

A guide pin 13 is provided protruding from the outer surface of the second lens group support frame 4 . Then, a coil spring serving as a biasing means 14 surrounds the rod 15 so that the guide pin 13 is always pressed against the drive cam surface 11, and the first lens group support frame 3 and the second lens group support frame 4 are connected to each other. It is compressed and interposed between. Further, the tip of the guide pin 13 is engaged in a straight groove 9 formed in the first lens group support frame 3 parallel to the optical axis. Three sets of straight grooves 9 and guide pins 13 are provided on the circumference. Reference numeral 12 denotes a presser plate fixed to the rear end of the first lens group support frame 3 to prevent the second drive cam 10 from moving in the axial direction.

Note that the guide pin 13 includes a rotatable guide roller and the like.

Protrusions 3b are formed at three locations on the outer surface of the rear end of the first lens group support frame 3, and guide pins 21 are protruded from each of the protrusions 3b. Further, the fixed frame 17 fixed to the camera body has three straight grooves 19 bored in parallel with the optical axis, and a drive ring 22 is fitted around the outer periphery of the fixed frame 17 so as to be rotatable around the optical axis. A guide pin 21 protruding from the first lens group support frame 3 engages with a linear groove 19 of the fixed frame and a first cam groove 23 formed in the drive ring 22.

A developed view of this first cam groove 23 is shown in FIG. 5, and when the drive ring 22 rotates, the guide pin 21 is guided by the first cam groove 23 and moves in the optical axis direction. The lens group 1 moves forward and backward in the optical axis direction. Note that at both ends of the first cam groove 23.

Circumferential groove portion 23 where the guide pin 21 does not move in the optical axis direction
a, 23b are formed.

A protrusion 10b is formed at the rear end of the drive cam cylinder 10, and a guide pin 20 is protruded from the protrusion 10b.

The tip of the guide pin 20 is engaged with a second cam groove 26 formed in the drive ring 22.

Furthermore, an escape groove 18 is bored in the fixed frame 17 at a portion through which the guide pin 20 passes. A developed view of the second cam groove 26 and relief groove 18 is shown in FIG. , a front portion 26b having a smaller slope than the first cam groove 23, and a rear portion 26c parallel to the first cam groove 23. And the first
The guide pin 20, which moves forward and backward in the optical axis direction together with the lens group support frame 3, is guided by the second cam groove 26 and rotates around the optical axis, thereby rotating the drive cam barrel lO around the optical axis. As a result, the second lens group support frame 4 is guided by the drive cam surface 11 shown in FIG.
moves relative to the first lens group support frame 3 in the optical axis direction.

FIG. 20 shows the relationship between the loci of the first and second cam grooves 23, 26 and the amount of rotation of the drive cam barrel lO (that is, the amount of rotation of the guide pin 20). Center trajectory 23s of the first cam groove and center trajectory 26s of the second cam groove
It rotates by the difference between The movement locus of the guide pin 20 rotating in this manner is indicated by 20s.

A pinion 24 meshes with a toothed portion 22a fixed to the outer periphery of the drive ring 22 with screws.
It is rotationally driven by a drive motor (not shown).

Of course, the drive ring 22 may be rotated manually using a manual operation ring or the like. This is a stopper that restricts rearward movement, and is provided to protrude from the fixed frame 17.

Next, the operation of the above embodiment will be explained.

In the shortest focal length state shown in FIGS. 1 and 2, each guide pin 13, 20, 21 is in the position shown in FIGS. 5 and 6, as described above.

Next, when the pinion 24 is driven by a drive motor (not shown), the drive ring 22 rotates around the optical axis.

Then, the guide pin 21 protruding from the first lens group support frame 3 is guided by the first cam groove 23 formed in the drive ring 22 and moves forward. The unfolded plane of FIG. 7 shows the state at that time. As a result, the lens group support frame 3 of Ml is extended forward, and together with this, the first lens group 1 is extended forward.

When the first lens group support frame 3 is extended forward, the guide pin 20 protruding from the drive cam barrel lO moves forward together with the first lens group support frame 3, and the second cam f! 11
26 to rotate around the optical axis. Then, the drive cam barrel 10 rotates around the optical axis, so that the guide pin 13 protruding from the second lens group support frame 4 moves into the coil spring 14.
resists the urging force of , and moves forward as shown in FIG. As a result, as shown in FIG. 9, the second lens group support frame 4 moves forward, and the second lens group 2 moves forward.
approaches lens group 1. In other words, the distance between the first and second lens groups 1.2 is determined by the shape of the cam surface 11 formed on the drive cam barrel lO that is operated by the movement of the first lens group support frame 3 back and forth. In this way the second
The lens group 2 moves forward by a distance equal to the amount of movement of the first lens group support frame 3 plus the amount of relative movement of the second lens group support frame 4 with respect to the first lens group support frame 3. .

Then, when the drive ring 22 is further rotated, each guide pin 13, 20 .
21 moves. That is, the guide pin 21 protruding from the first lens group support frame 3 moves to the frontmost position. On the other hand, the guide pin 20 protruding from the drive cam barrel 10 rotates a large amount (for example, about 70 degrees), so that the guide pin 13 protruding from the second lens group support frame 4 is at the highest point on the drive cam surface 11. come into position. As a result, the distance between the first and second lens groups 1.2 becomes the closest as shown in FIG. The state shown in Fig. 10 is the state where the focal length is the longest, and if the rotation of the binion 24 is stopped on the way to this state, each lens group 1°2 will stop at that position and return to the intermediate focal point. When the distance is obtained and the pinion 24 is reversed, the state returns to the state shown in FIG. 1 where the focal length is short.

The zoom lens barrel of this embodiment is also capable of so-called macro photography. When performing macro photography, a macro photography switch (not shown) is turned on, and a drive motor (not shown) rotates the binion 24 from the long focus state shown in FIG. 10 in the extending direction. Then,
The drive ring 22 further rotates around the optical axis, and the guide pin 21 integrated with the first lens group support frame 3 engages with the circumferential groove 23a of the first cam groove 23, as shown in FIG. match. Therefore, the guide pin 21 does not move in the optical axis direction, but the guide pin 20 protruding from the drive cam barrel lO rotates around the optical axis by the second cam groove 26.

As a result, as shown in FIG. 14, the drive cam surface lO
According to the change in , the guide pin 13 integrated with the second lens group support frame 4 moves back by an amount ΔM. In this way, the first lens group 1 does not move at all, and the distance between the first and second lens groups widens, making it possible to perform macro photography with zero extension of the lens system as a whole. This is very useful for making the tube more compact.

In the present invention, the distance between the first and second lens groups 1.2 is determined by the movement of the second lens group support frame 4 by the rotation of the drive cam barrel lO in this manner. Compared to the conventional mechanism in which the first and second lens groups are operated independently, the occurrence of spacing errors is much smaller.

Furthermore, in this embodiment, since the second lens group support frame 4 is always urged backward by the coil spring 14, the guide pin 13 is always pressed against the drive cam surface it. Therefore, no backlash due to clearance occurs between the drive cam surface 11 and the guide pin 13, and the first
The distance between the lens group 1.2 and the second lens group 1.2 is controlled with extremely high precision without any variation.

When storing the lens barrel, when the main switch (not shown) is turned off, the pinion 24 is rotated by a drive motor (not shown), and from the shortest focal length state shown in FIG.
The drive ring 22 further rotates in the retracting direction. As shown in FIG. 15, the guide pin 21 is
The first lens group support frame 3 is moved to the rear end of the cam groove 23 of 1 and retracted. In this part, the second cam groove 26 is formed parallel to the first cam groove 23, so the drive cam barrel 10 does not rotate. Therefore, the second lens group support frame 4 is connected to the first lens group support frame. However, the second lens group support frame 4 collides with the stopper 25 and is restricted from moving backward.

Therefore, as shown in FIGS. 16 and 17,
The coil spring serving as the biasing means 14 is compressed, and the second lens group 2 does not move from the position of the shortest focal length, and only the first lens group 1 is further recessed into the lens barrel and stored. be able to. This avoids interference with the mechanical parts of the body, and is very advantageous in preventing dust from adhering to a part of the film aperture.

In addition, when returning from the storage state to the use state shown in FIG. 1, the operation opposite to the above is performed by turning on a main switch (not shown).

18 and 19 show the relationship between the amount of movement of the first and second lens groups of the embodiment described above, the rotation angle of the drive ring, and the focal length, and ΔZ in FIG. indicates the maximum amount of variation in the distance between the first and second lens groups.

[Effects of the Invention] According to the zoom lens barrel of the camera of the present invention, during a zooming operation, the distance between the first lens group and the second lens group is determined only by the rotation angle of the drive cam barrel. Therefore, the fluctuation error in the spacing between the lens groups is extremely small. Therefore, it is possible to always obtain stable and good focusing accuracy even with a zoom lens with a large zoom ratio, where the fluctuation error in the spacing has a sensitive effect on the focus position. can.

Furthermore, there is no need to form a strongly inclined cam groove in the drive ring according to the amount of movement of the second lens group.

The overall length of the drive ring can be shortened compared to conventional models, making it possible to make the lens barrel more compact.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view of an embodiment of the present invention, with the lower half omitted, and FIG. 2 is a side cross-sectional view of the embodiment in a different section. Fig. 3 is a front sectional view of the embodiment, Fig. 4 is an exploded perspective view, Figs. 5 and 6 are exploded views showing the positional relationship between cams and guide pins, and Figs. 7 and 8. The figure is a developed view showing the positional relationship between the cams and guide pins with the lens group extended halfway, Figure 9 is a side sectional view of the embodiment in that state, and Figure 10 is the lens group fully extended. FIG. 3 is a side sectional view of the embodiment in a closed state. Figures 11 and 12 are developed views showing the positional relationship between the cam grooves and guide pins in that state, and Figures 13 and 14 show the positional relationship between the cams and guide pins in the macro shooting state. 15 and 16 are developed views showing the positional relationship between cams and guide pins in the stored state, FIG. 17 is a side sectional view of the embodiment in that state, and FIGS. 18 and 19. The figure is a diagram showing the relationship between the amount of movement of the lens group and the rotation angle and focal length of the drive ring. Figure 20 is a diagram showing the relationship between the locus of the cam groove and the amount of rotation of the drive cam barrel. is a side sectional view of a conventional zoom lens barrel. l...first lens group, 2...second lens group, 3
...First lens group support frame, 4...Second lens group support frame, 9...Straight II groove, 10...Drive cam cylinder, 1
DESCRIPTION OF SYMBOLS 1... Cam surface, 12... Presser plate, 13... Guide pin, 14... Biasing means, 17... Fixed frame, 19...
... Straight groove, 20 ... Guide pin, 21 ... Guide pin, 22 ... Drive ring, 23 ... First cam groove, 2
4... Pinion, 26... Second cam groove. Agent Patent Attorney Kazuhiko Mitsui Figure 2 3a Figure 3 Figure 5 Figure 7 Figure 9 Figure 10 Figure 13 Figure 15 Figure 918 #Movement 1 Figure 19 S Dynamics Figure 21

Claims (3)

[Claims] (1) In a zoom lens barrel that performs zooming by moving multiple lens groups in the optical axis direction by different amounts, a first lens group support frame that supports the first lens group; a second lens group support frame that is relatively movably supported by the first lens group support frame and supports the second lens group; and a second lens group support frame that is rotatably provided around the optical axis and that supports the first lens group. a drive ring for driving the lens group support frame forward and backward in the optical axis direction; A zoom lens barrel comprising: a drive cam that drives a group support frame forward and backward in an optical axis direction relative to a first lens group support frame. (2) A zoom lens mirror according to claim 1, wherein a guide pin is provided protrudingly on the second lens group support frame, and a biasing means is provided for biasing the guide pin so as to constantly press the guide pin against the drive cam. Tube. (3) From the state where the two lens groups are retracted into the lens barrel and their combined focal length is the shortest, the first lens group can be further moved in the retracting direction and housed in the lens barrel. The zoom lens barrel according to claim 1 or 2.