JPH01164909A - Lens barrel for zoom lens of camera - Google Patents

Abstract

PURPOSE:To control the interval between lens groups with high accuracy by constituting the title lens barrel so that a second driving means is operated by a motion of a first lens group supporting frame, a second lens group supporting frame is driven and zooming is executed. CONSTITUTION:An interval between the first and second lens groups 1, 2 is determined by a cam groove 11 which has been formed in a cam cylindrical body 10 operated by advance and retreat of the first lens group supporting frame 3. Thus a second lens group 2 moves forward by a distance which has added a moving extent of the second lens group supporting frame 4 to a moving extent of the first lens group supporting frame 3. Accordingly, the second lens group supporting frame 4 is operated by a motion of the first lens group supporting frame 3, and an interval between a first lens group 1 and the second lens group 2 is determined, therefore, an interval error of the first and second lens groups becomes very small. In such a way, even in case of a zoom lens whose zoom ratio is large, satisfactory focus accuracy is always obtained stably.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a zoom lens barrel for a camera, and in particular,
This invention relates to an improvement in a mechanism for performing zooming by moving a lens group.

[Prior Art] To perform zooming, it is necessary to separately move two lens groups in the optical axis direction. Therefore, conventionally, as shown in FIG. 14, for example, a first support frame 52 that supports a first lens group 51 and a second support frame 54 that supports a second lens group 53 are connected to guide rods. 55, 56 and are arranged to move only in the optical axis direction, guide pins 57, 58 are provided protruding from each support frame 52 and 54, and two cam grooves 60 are formed in the drive ring 59. .61 is engaged with the guide pin, and by rotating the drive ring 59, the first and second lens groups 51 and 53 are moved independently in the optical axis direction.

[Problems to be Solved by the Invention] However, in the zoom lens barrel of the conventional camera as described above, the two lens groups were driven separately by the drive ring, so the two cam grooves 60, 61 and Guide pin 57.58
Due to the clearance that exists between the two lens groups, the distance between the two lens groups 51 and 53 varies from time to time, resulting in fluctuations in the focal plane.Moreover, the device is large and the lens barrel cannot be made compact. There was a drawback that it could not be summarized as follows. Especially when the zoom ratio of the lens increases,
Fluctuation errors in the spacing between each lens group will sensitively affect the focus position, resulting in an unacceptable drop in focus accuracy, and the amount of movement of each lens group will increase, making the lens barrel larger. However, the drawbacks mentioned above cannot be ignored.

The present invention eliminates such drawbacks of the conventional zoom lens, makes it possible to move each lens group while controlling the distance between each lens group with high precision during zooming, and allows the lens barrel to be configured compactly. The purpose of the present invention is to provide a zoom lens barrel for a camera.

[Means for Solving the Problems] In order to solve the above-mentioned problems, a zoom lens barrel for a camera according to the present invention includes a first lens group with a small movement amount and a second lens group with a large movement amount. In a zoom lens barrel of a camera having two movable lens groups, each of which is moved in the optical axis direction to perform zooming, the first lens group supports the first lens group. a support frame, a second lens group support frame provided within the first support frame to support the second lens group, and a second lens group support frame for driving the first lens group support frame forward and backward in the optical axis direction. The second lens group support frame is actuated by the movement of the first lens group support frame and the first lens group support frame to move the second lens group support frame forward and backward in the optical axis direction relative to the first lens group support frame. A second driving means is provided.

[Operation] The first lens group support frame is driven forward and backward in the optical axis direction by the first driving means, and the first lens group is extended or retracted. The movement of the first lens group support frame activates the second driving means to drive the second lens group support frame, and the second lens group support frame is moved relative to the first lens group support frame. move relatively forward and backward in the optical axis direction. Zooming is thus performed, during which the spacing between the first and second lens groups is determined solely by the operation of the second drive means.

[Example] An example of the present invention will be described based on FIGS. 1 to 13.

Figures 1 and 2 show the lens barrel with the focal length shortest due to zooming, and Figure 3 is a front cross-sectional view that shows the combined positional relationship of the cam grooves and guide pins. be. Note that FIG. 1 shows a composite of the A-0 cross section and the B-0 cross section in FIG. 3. FIG. 2 shows a C-O cross section in FIG. 3. Also, Figures 4 and 5 show 4! ! FIG. 2 is a developed view showing the positional relationship between a plurality of cam grooves and guide pins formed within the premises.

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 1 is fixed within a helicoid ring 6 that is screwed into the autofocus unit 5. The first lens group l is driven by the autofocus unit 5 in the optical axis direction for focusing. That is, in this embodiment, the autofocus unit 5 rotates the operating pin 5a toward the optical axis by a predetermined amount depending on the photographing distance, and the first lens group 1 is rotated and extended by the engagement piece 6a that engages with it. In this way, the first lens group 1 is supported by the first lens group support frame 3 via the autofocus unit 5 and the helicoid ring 6. It may be directly supported by the frame 3.

7 is a cover fixed to the first lens group support frame 3 with screws, and 8 is a barrier device that moves to the front of the first lens group 1 to protect the lens surface when the camera is used.

A linear groove 9 in the axial direction is bored in the peripheral surface of the rear half of the first lens group support frame 3, and a cam cylinder 10 is rotatably fitted to the optical axis opening on the inner peripheral side thereof. ing. As shown in FIG. 4, the cam groove 11 formed in the cam cylinder body 10 has a straight groove 11a bent at an acute angle and extending in the axial direction at one end, and a straight groove 11a extending in the axial direction at the other end 11b. It is formed in a dogleg shape with an obtuse angle.

In FIG. 1, reference numeral 12 denotes a presser plate fixed to the rear end surface of the first lens group support frame 3 so that the cam barrel 10 does not move in the axial direction.

A second lens group support frame 4 is loosely fitted on the inner circumferential side of the cam cylinder lO, and a guide pin 13 protruding from the second lens group support frame 4 is inserted into the linear groove 9 and the cam groove. 11. Note that three sets of these linear grooves 9, cam grooves 11, and guide pins 13 are provided at 120 degree intervals on the circumference.

Further, as the guide pin 13, a rotatable guide roller or the like may be used.

between the first and second lens group support frames 3 and 4.

A coil spring 14 is interposed so as to always bias the second lens group support frame 4 rearward. Reference numeral 15 denotes a rod inserted into the coil spring 14 so as to guide the expansion and contraction movement of the coil spring 14, and its head 15a is pressed and fixed to the first lens group support frame 3 by the coil spring 14. There is. In addition, the second lens group support frame 4
An escape hole 16 is bored in the coil spring 14 to prevent the rod 15 from colliding with it when the coil spring 14 is compressed.

A fixed frame 17 is fixed to the camera body, and has a cam groove 18 and a straight groove 19 in the axial direction. A guide pin 20 protruding from the cam cylinder body 10 is engaged with the cam groove 18 . This cam groove 18 is
As shown in FIG. 4, it has a straight portion 18a along the axial direction near the rear end. 3a, the guide pin 20 is the first
This is a relief part cut out so as not to interfere with the lens group support frame 3.

A spacer 3 is provided on the outer surface of the rear end of the first lens group support frame 3.
b are fixed at 120 degree intervals, and guide pins 21 are protruded therefrom. Therefore, this guide pin 21 is integrated with the first lens group support frame 3 via the spacer 3b. The spacer 3b is loosely fitted to the inner peripheral surface of the fixed frame 17, and a drive ring 22 is rotatably fitted to the outer periphery of the fixed frame 17 around the optical axis. and spacer 3
The guide pin 21 protruding from b is connected to the straight groove 19 of the fixed frame.
and is engaged with the cam groove 23 of the drive ring 22. The cam groove 23 has a circumferential groove 23a at its rear end, as shown in FIG.

In addition, a tooth portion 22 fixed to the outer periphery of the drive ring 22 with screws is provided.
A pinion 24 is engaged with a, and this pinion 2
4 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. 26 is a cover of the lens barrel.

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

When the pinion 24 is driven by a drive motor (not shown) from the shortest focal length state shown in FIGS. 1 and 2, the drive ring 22 rotates around the optical axis. Then, the guide pin 21 protruding from the spacer 3b moves to the drive ring 22.
It moves forward while being guided by a cam groove 23 formed in the.

The developed view in FIG. 6 shows this state. As a result, the first lens group support frame 3 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 cam barrel 10 is moved to the 20 shown in FIG.
As shown in a, it moves forward and is guided by the cam groove 18 of the fixed frame 17 and rotates around the optical axis. Then, the cam cylinder body 10 rotates around the optical axis, so that the guide pin 13 protruding from the second lens group support frame 4 resists the biasing force of the coil spring 14, as shown in FIG. to move forward. As a result, as shown in the seventh rgJ, the second lens group support frame 4 moves forward, and the second lens group 2 approaches the first lens group l. That is, the first and second
The distance between the lens groups 1 and 2 is the same as that of the first lens group support frame 3.
It is determined by the cam groove 11 formed in the cam cylinder body 10, which is activated by the movement of the cam cylinder. In this way, the second lens group 2 moves forward by a distance equal to the sum of the amount of movement of the first lens group support frame 3 and the amount of movement of the second lens group support frame 4.

The state shown in Fig. 7 is the state where the focal length is the longest, and if the rotation of the pinion 24 is stopped on the way to this state, each lens group 1.2 will stop at that position and reach an intermediate focus. 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. In the present invention, in this way, the second lens group support frame 4 is actuated by the movement of the first lens group support frame 3, and the first and second lens groups 1
．． Since the distance between the two lens groups is determined, the occurrence of a distance error is much smaller than in the conventional mechanism in which the first and second lens groups are each operated independently.

In this embodiment, a second lens group support frame 4 is further provided.
is always urged rearward by the coil spring 14, so the guide pin 13 is always pressed against the rear surface side of the cam groove 11. Therefore, the cam groove 11 and the guide pin 13
There is no backlash due to clearance between the first and second
The distance between the lens groups 1 and 2 is controlled with extremely high precision without any variation. Furthermore, since the second lens group support frame 4 and the cam barrel 20 for driving it are housed within the first lens group support frame 3, the lens barrel can be made compact.

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 pinion 24 from the long focus state shown in FIG. 7 in the extending direction. Then, the drive ring 22 further rotates toward the optical axis, and the guide pin 21, which is integral with the first lens group support frame 3, moves further toward the distal end as shown in FIG. As a result, the first lens group support frame 3 is further extended forward, and the guide pin 20 protruding from the cam barrel 10 also moves forward as shown at 20b in FIG. 4, and as a result, the optical axis opening is moved forward. Rotate to . Therefore, the cam cylinder body 10 rotates toward the optical axis, and the guide pin 13 protruding from the second lens group support frame 4 as shown in FIG. As a result, the second lens group support frame 4 moves in a direction away from the first lens group 1. In this way, while the entire lens system is extended forward, the interval between the first and second lens groups is widened, and macro photography can be performed with a small amount of extension of the entire lens system.

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. 11, the guide pin 21 moves to the rear end of the cam groove 23, and the first lens group support frame 3 is retracted. At this time, the guide pin 20 protruding from the cam cylinder 10 enters the straight portion 18a at the rear end of the cam groove 18, as shown at 20c in FIG. 4, so the guide pin 20 does not rotate. , Therefore, the cam cylinder body 10 also does not rotate.

The second lens group support frame 4 also tries to move rearward together with the first lens group support frame 3, but the rearward movement of the second lens group support frame 4 is restricted by the stopper 25. On the other hand, the guide pin 13 protruding from the second lens group support frame 4 enters the axial straight portion 11a of the cam groove 11 formed in the cam cylinder IO, as shown in FIG. Therefore, only the cam cylinder body 10 can move rearward while the guide pin 13 remains in the same position. A state in which this storage operation is completed is shown in FIG. 13, where the coil spring 14 is compressed and the end of the rod 15 enters the escape hole 16. In this way, the position of the second lens group 2, which is closer to the camera body, remains unchanged, while the first lens group 1, which is closer to the front end, is moved.
By retracting the lens further than the shortest focal length, it is possible to reduce the size of the lens barrel when stored, making it easier to carry.

The cam groove 23 formed in the drive ring 22 of this embodiment is further formed with a circumferential groove 23a, which operates an opening/closing mechanism (not shown) of the barrier device 8 when stored. The drive ring 22 is provided to obtain an operating force, and the drive ring 22 continues to rotate within the circumferential groove 23a even after the lens system is completely stored.

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).

[Effect of the invention] According to the zoom lens barrel of a camera according to the present invention.

During the zooming operation, the distance between the first lens group and the second lens group is determined only by the second driving means, so the fluctuation error in the distance between the lens groups is extremely small. Even in a zoom lens with a large zoom ratio in which fluctuation errors sensitively affect the focus position, the present invention has an excellent effect in that stable and good focus accuracy can always be obtained.

[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, FIG. 2 is a side cross-sectional view of the embodiment at a different cross-section, and FIG. 3 is a front cross-sectional view of the embodiment. , FIGS. 4 to 6 are developed views showing the positional relationship between cam grooves and guide pins, FIG. 7 is a side sectional view of the embodiment with the lens group extended, and FIGS. 8 to 12. 13 is a developed view showing the positional relationship between cam grooves and guide pins, FIG. 13 is a side sectional view of the embodiment in a stored state, and FIG. 14 is a side sectional view of a conventional zoom lens barrel. 1... First lens group, 2... Second lens group, 3
...First lens group support frame, 4...Second lens group support frame, 9...Straight groove, 10...Cam cylinder body, 11.
...Cam groove, 12...Press plate, 13...Guide pin, 14...Coil spring, 17...Fixing frame, 18...
・Cam groove, 19... straight groove, 20... guide pin,
21... Guide pin, 22... Drive ring, 23...
Cam groove, 24...pinion. Agent Patent Attorney Kazuhiko Mitsui Figure 1 Figure 2 Figure 8 Figure 10 Figure 9 Figure 13

Claims (3)

[Claims] (1) It has two movable lens groups, a first lens group with a small amount of movement and a second lens group with a large amount of movement, and zooming is performed by moving each of these lens groups in the optical axis direction. In the zoom lens barrel of the camera, the first
a first lens group support frame that supports the lens group; a second lens group support frame that is provided within the first support frame and supports the second lens group; and the first lens group. a first driving means for driving the support frame forward and backward in the optical axis direction;
and a second driving means operated by the movement of the lens group support frame to drive the second lens group support frame forward and backward in the optical axis direction relative to the first lens group support frame. A camera zoom lens barrel characterized by: (2) The second driving means includes a cam groove that rotates as the first lens group support frame advances and retreats, and a guide that protrudes from the second lens group support frame and engages with the cam groove. 2. A zoom lens barrel for a camera according to claim 1, comprising a pin and biasing means for constantly biasing said second lens group support frame in the optical axis direction. (3) From the state in which the two lens groups are retracted so that their combined focal length is the shortest, the first lens group can be further moved in the retracting direction and stored. A zoom lens barrel for a camera according to item 2.