JPH0192708A - Zoom mechanism for zoom lens - Google Patents

Abstract

PURPOSE:To obtain a miniature and inexpensive zoom mechanism for a zoom lens by executing both zooming and focusing by using one piece of driving source. CONSTITUTION:First and the second driving mechanisms 11 are constituted so that driving force is given by a common driving source 10, and the driving source 10 is connected to the first driving mechanism 9, connected to the second driving mechanism 16 at the time of zooming, and switched so that the connection is released at the time of focusing operation. Accordingly, before the focusing operation, a focusing lens group I and other lens group II than the focusing lens group execute a movement of zooming by the first and second driving mechanism 11, and when the zooming is ended, the focusing lens group I executes a focusing operation by the first driving mechanism 9. In such a way, both zooming and focusing can be executed by using the same driving source 10. Therefore, a zoom mechanism which is small in size and low in cost is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a zoom mechanism of a zoom lens, and more specifically, to zooming by moving each of a plurality of lens groups including a focusing lens group in the optical axis direction. This invention relates to a zoom mechanism of a zoom lens.

[Prior Art] A lens shutter camera with a zoom lens includes a zoom drive mechanism that drives each lens group during zooming, and a focus drive mechanism that drives a focusing lens group during focusing.

[Problems to be Solved by the Invention] However, in the prior art, with regard to driving the focusing lens group, each of the driving mechanisms for zooming and focusing is configured to overlap. Therefore, if an autofocus configuration is used with electric zoom, the drive sources (motors) will be duplicated, making the camera larger, increasing the number of parts, and increasing costs.

In view of these problems, the present invention makes it possible to perform both zooming and focusing using one driving source,
The purpose of the present invention is to provide a zoom mechanism for a zoom lens that is small and inexpensive.

[Means and effects for solving the problem] The zoom mechanism of the zoom lens of the present invention is such that zooming is performed by moving each of a plurality of lens groups including a focusing lens group in the optical axis direction, The first drive mechanism drives the focusing lens group in the optical axis direction, and the second drive mechanism drives the lens groups other than the focusing lens group in the optical axis direction. 1st
．． The second drive mechanism is configured to be given driving force by a common drive source, and the drive source is connected to the first drive mechanism, and the second drive mechanism is connected during zooming and focuses. During operation, the 17 connection is switched to be released. Therefore, before the focusing operation, the first. The focusing lens group and the lens groups other than the focusing lens group perform zooming movement by the second drive mechanism, and when the zooming is completed, the focusing lens group performs a focusing operation by the first drive mechanism.

[Embodiment] FIGS. 1 and 2 show the structure of a first embodiment in which the present invention is applied to a camera with a two-group zoom lens.

FIG. 3(A) shows the movement of the lens group in an example of a conventional two-group zoom lens, and FIG. 3(B) shows the movement of the lens group in this embodiment.

In FIG. 1, a front frame 1 that holds the front group I, which is a focusing lens group, and a rear frame 2 that holds the rear group support shafts 4, 5
is supported so as to be movable in the optical axis direction, and is prevented from rotating. The front frame 1 is screwed into a front screw shaft 6 that is rotatably supported parallel to the support shaft 4, and the rear frame 2 is screwed to a rear screw shaft 6 that is rotatably supported parallel to the support shaft 4. 7
By the rotation of the screw shafts 6 and 7, the front frame 1. is screwed into the front frame 1. The rear frame 2 is adapted to be sent in the optical axis direction. The front gear 8 integrated with the front threaded shaft 6 is connected to the front gear 8 via the gear 9.
It is connected to a sun gear 12 of a differential gear mechanism 11 fixed to the drive shaft of the motor 10.

The differential gear mechanism 11 includes an internal gear 13 that is rotatable relative to the sun gear 12, as shown in detail in FIG.
, a plurality of planetary gears 14 that mesh with the internal gear 13 and the sun gear 12, and a carrier 15 that rotatably supports the planetary gears 14. Teeth are formed on the outer periphery of the carrier 15, and a rear gear 16 integral with the rear threaded shaft 7 meshes with the teeth.

One four part 13a is formed at a predetermined location of the internal gear 13, and a convex part 17 of the locking member 17 is formed in the concave part 13a.
a can face each other.

The locking member 17 is connected to the electromagnetic plunger 18. Further, at the tip of the locking member 17, the carrier 1
A carrier locking portion 17b that protrudes sharply is formed on the back side of the carrier 5. When the electromagnetic plunger 18 is in a non-energized state, the locking member 17 is biased by the spring 19 in the direction of the arrow a so that the convex portion 1.7a engages with the concave portion 13a to prevent the internal gear 13 from rotating. I have to. In this state, the carrier locking portion 17b is spaced apart from the carrier 15, so rotation of the carrier 15 is not hindered. When the electromagnetic plunger 18 is energized, the locking member 17 moves in the direction of arrow A against the biasing force of the spring 19, and the convex portion 17a is pulled out of the concave portion 13a, allowing the internal gear 13 to rotate freely. become. In this state, the carrier locking portion 17b locks the teeth of the carrier 15 and prevents the carrier 15 from rotating.

As shown in Figure Ts2, the amount of rotation of the gear 8 is read by a front frame position reader 20, and the position of the rear frame 2 is read by a focal length reader 21.

The output of these readers 20 and 21 and the shooting distance setting device 22
The control circuit 23 controls the motor 10 and the electromagnetic plunger 18 based on the output.

Next, the operation of the first embodiment configured as described above will be explained.

First, when a zooming signal is input by a zooming switch (not shown), the control circuit 23 drives the motor 10. Initially, the electromagnetic plunger 18 is in a de-energized state and the locking member 17 is biased in the direction of the arrow a, so that the internal gear 13 is locked by the locking member 17 as described above. The carrier 15 is rotatable.

Therefore, when the sun gear 12 is rotated by the drive of the motor 10, the planet gear 14 revolves around the sun gear 12, and the carrier 15 rotates. The rotation of the carrier 15 is transmitted to the rear screw shaft 7 via the rear gear 16. Further, the rotation of the sun gear 12 is transmitted to the front threaded shaft 6 via the gear 9 and the front gear 8. That is, at this time, the differential gear mechanism 11
This causes the front screw shaft 6 and the rear screw shaft 7 to rotate simultaneously. Then, front frame 1 (front group I) and rear frame 2 (rear group ■)
move linearly from wide-angle (W) to telephoto (T) at different speeds, as shown in FIG. 3(B).

Incidentally, in the case of a conventional two-group zoom lens, as shown in Figure 3 (
As shown in A), if the rear group ■' is linearly moved from wide to tele by one driving source, then the front group I' is controlled non-linearly by another driving source. ing.

When zooming is completed and a release signal is input next, the control circuit 23 turns on the electromagnetic plunger 18. Then, the locking member 17 moves in the direction of the arrow, and the carrier 15
is locked, and the internal gear 13 becomes freely rotatable. When the motor 10 rotates in this state, the rear frame 2 remains stopped.
Only the front frame 1 moves for focusing. At this time, the front frame position reader 20. The motor 10 is controlled by the output of the control circuit 23 based on the outputs of the focal length reader 21 and the photographing distance setting device 22, and the movement of the front frame 1 is controlled. When the front frame 1 has moved to the predetermined position, the motor 10
stops. In this state, the front group I is in focus on the subject at a predetermined focal length between the infinite (oo) position shown by the two-dot chain line in Figure 3 (B) and the close position shown by the one-dot chain line. .

For comparison, in the conventional two-group zoom lens shown in FIG. Focusing will be moved between the oo) position and the closest position shown by the dashed line.

After focusing, exposure is performed. After the exposure is completed, the motor 10 is reversed by the output of the control circuit 23, and the electromagnetic plunger 18 is de-energized. By reversing the motor 10, the front frame 1 moves in the opposite direction to the above. Then, when the front frame 1 returns to the position before focusing, the convex portion 17a of the locking member 17 and the concave portion 13a of the internal gear 13 match, and the rotation of the internal gear 13 is locked by the locking member 17. At the same time, the carrier 15 becomes rotatable. Therefore, after this, the front frame 1 and the rear frame 2 are again in a state where they can move in a linear relationship, and zooming becomes possible. Here, if the rotation angle of the internal gear 13 required to focus the front frame 1 from flash to close range is less than one rotation, and if the recess 13a of the internal gear 13 is provided at one location, the internal gear 13 Even if the power supply to the electromagnetic plunger 18 is cut off at the time when the electromagnetic plunger 18 moves, no problem will occur in the operation. In addition, if the amount of movement of the front frame 1 during focusing is large and the internal gear 13 rotates multiple times, a means for detecting the rotation speed of the internal gear 13 is provided, and when the front frame 1 is reversed and returned. In addition, the power to the electromagnetic plunger 18 may be cut off when the remaining amount of reverse rotation of the internal gear 13 becomes one rotation or less.

According to the first embodiment, since the focusing and zooming mechanisms are used together and a dedicated focusing mechanism is omitted, it is possible to provide a compact and low-cost zoom lens camera. Furthermore, since the accuracy is compensated by the mechanism, there is no need for a high-precision encoder or complicated control.

Next, a second embodiment of the present invention shown in FIG. 5 will be described.

The configuration of the second embodiment is exactly the same as the first embodiment with respect to the front group I, and differs only with respect to the drive of the rear group (2).

That is, the cam bin 2a on the rear frame 2A holding the rear group ■
is fitted into the cam groove 31a of the cam ring 31. Cam ring 3
A gear portion 31b is formed at the rear end of the outer periphery of the differential gear mechanism 11, and the teeth of the carrier 15 of the differential gear mechanism 11 mesh with the gear portion 31b.

The operation of this embodiment is almost the same as that of the first embodiment. However, when the cam ring 31 rotates at a constant speed due to the rotation of the carrier 15 of the differential gear mechanism 11, the cam pin 2a of the rear frame 2A is guided by the cam groove 31a of the cam ring 31, and as shown in FIG. ■Moves nonlinearly in the optical axis direction from wide to tele. At this time, the front group I moves linearly as in the previous embodiment. After this, only the front frame 1 moves to perform focusing, but in a zoom lens in which the rear group (■) moves nonlinearly, the amount of movement of the front group I for focusing is constant regardless of the focal length. The focal length reader 21 (see FIG. 2) used in the first embodiment is not required.

In this manner, in the second embodiment, lens control is made easier than in the first embodiment by using the cam ring 31.

Above 1st. In the second embodiment, the rotation of the internal gear 13 of the differential gear mechanism 11 is locked and unlocked by the operation of the electromagnetic plunger 18. The rotation of the internal gear 13 may be locked and unlocked in conjunction with the operation of a button. Next, an example of a specific configuration of this portion will be described with reference to FIG. 7.

In FIG. 7, a release button 41 is attached to a camera body 43 via a coiled release spring 42 so as to be movable up and down, and the lower end of the release button 41 is in contact with one arm of a connecting lever 44 within the body 43. . The other arm of the connecting lever 44 is connected to a locking member 47 by a pin 44a. The locking member 47, which is guided through the elongated hole 46 by the immovable guide pin 45, is moved in the direction of arrow a by the spring 19 like the locking member 17 during normal operation when the release button 41 is not pressed. The convex portion 47a of the engaging member 47 fits into the concave portion 13a of the internal gear 13, and locks the rotation of the internal gear 13. At this time, the carrier locking portion 47b is retracted from the teeth of the carrier 15. Therefore, during zooming when the release button 41 is not pressed,
The sun gear 12 and carrier 15 rotate, and the front frame 1 and rear frame 2 move in the optical axis direction. After zooming, when the release button 41 is pressed down, the connecting lever 44 rotates in the counterclockwise direction shown in the figure, so the locking member 47 moves in the direction of the arrow A, and the protrusion 47a separates from the recess 13a. At the same time, the carrier 15 is locked by the carrier locking portion 47b.

Therefore, in this state, the rear frame 2 (or 2A) is stopped, and only the front frame 1 moves in the optical axis direction for focusing due to the rotation of the carrier 15. After that, when exposure is performed and the release button 41 returns to its original position, if the motor 10 is reversely rotated, the locking member 47 will release the spring 19 when the internal gear 13 returns to the position before focusing. moves in the direction of the arrow and locks the internal gear 13 again.
The carrier 15 becomes rotatable.

By omitting the electromagnetic plunger 18 in this manner, the zoom lens can be made smaller, the cost can be reduced, and the control can be simplified.

Next, an example in which the present invention is applied to a three-group zoom lens will be described. FIG. 8 shows a schematic configuration of the zoom lens of this embodiment. FIG. 9(A) shows the movement of the lens group in an example of a conventional three-group zoom lens, and FIG. 9(B) shows the movement of the lens group in this embodiment.

In FIG. 8, a first frame 51 holding the first group I, which is a focusing lens group, is connected to the front screw shaft 6, and a second frame 52 holding the second group ■ is connected to the first frame 52 by the rear screw shaft 7. As in the embodiment, each of the elements is configured to be movable in the optical axis direction.

As in the second embodiment, the third frame 53 holding the third group (3) has a cam pin 53a fitted into a cam groove 54a of a cam ring 54, and a gear portion 54b formed on the outer periphery of the cam ring 54.
is engaged with Gear 55. This gear 55 meshes with the carrier 15 of the differential gear mechanism 11 via the rear gear 16. Note that the first frame 51 to the third frame 53 are supported movably in the optical axis direction by a support member (not shown). The other configurations are the same as those of the first and second embodiments.

In this example, as in each of the above examples, first,
Since the sun gear 12 and carrier 15 of the differential gear mechanism 11 rotate, the front screw shaft 6 and the rear screw shaft 7 rotate, and the first frame 51 and the second frame 52 move in the optical axis direction. At this time, the gear 55 meshing with the carrier 15 via the rear gear 16 also rotates and the cam ring 54 rotates, so the third frame 53 also moves in the optical axis direction. Since the motor 10 rotates at a constant speed, the first frame 51 (first group ■) and second frame 52 (second group ■) move linearly from wide to tele, as shown in FIG. 9(B). However, since the third frame 53 (third group 3) rotates along the cam groove 54a, it moves nonlinearly in the optical axis direction. After this zooming, as in the first embodiment, only the first group I, which is the focusing lens group, has its own position information.

The camera moves in the optical axis direction based on the focal length information and photographing distance information, and focuses between the position shown by the two-dot chain line in FIG. 9(B) and the closest position shown by the one-dot chain line in FIG. 9(B).

In the conventional three-group zoom lens, as shown in FIG. 9(A), only the second group ■' moves linearly, and the first group I' moves linearly.
The third group I' moves non-linearly to perform zooming, and then the first group I' performs focusing.

It goes without saying that the present invention can also be applied to zoom lenses with three or more groups.

[Effects of the Invention] As described above, according to the present invention, zooming and focusing can be performed using the same drive source, and the drive mechanism for zooming is stopped during focusing. Therefore, it is possible to provide a highly accurate zoom mechanism that is small, inexpensive, and does not require complicated control.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a zoom mechanism showing a first embodiment in which the present invention is applied to a two-group zoom lens, FIG. 2 is a schematic configuration diagram of the two-group zoom lens, and FIGS. B) is a diagram showing the movement of the lens groups in an example of a conventional two-group zoom lens and the movement of the lens groups in the two-group zoom lens shown in FIG. 2 is an enlarged sectional view of the differential gear mechanism and switching means in FIG. 2, FIG. 5 is a schematic configuration diagram of a zoom mechanism showing a second embodiment in which the present invention is applied to a two-group zoom lens, and FIG. A diagram showing the movement of the lens groups in the two-group zoom lens shown in FIG. 5, and FIG. FIG. 8 is a configuration diagram showing another embodiment of the switching means for switching the differential gear mechanism in the zoom mechanism of the second embodiment. FIG. Schematic configuration diagram, Figure 9 (A) and (
B) is a diagram showing the movement of the lens groups in an example of a conventional three-group zoom lens and the movement of the lens groups in the three-group zoom lens shown in FIG. 8, respectively. 1...Front frame (focusing lens group) 2.2A.
... Rear frame (lens groups other than the focusing lens group) 6...
......Front threaded shaft (first drive mechanism) 7...
... Rear screw shaft (second drive mechanism) 8 ...
...Front gear (first drive mechanism) 9...
Gear (first drive mechanism) 10... Motor (drive source) 11... Differential gear mechanism (first and second drive mechanism) 16... Rear gear (Second drive mechanism) 17.4
7... Locking member (switching means) 18...
Electromagnetic plan, Ja (switching/means) 31.54...
- Cam ring (second drive mechanism) 41... Release button (switching means) 44... Connection lever (switching means) 51... First frame (focusing lens Group) 52...
...Second frame (lens groups other than the focusing lens group) 53...
...Third frame (lens groups other than the focusing lens group) 55-
・・・・・・Gear (second drive mechanism)■・・・・・・・・・
・・Front group, 1st group (focusing lens group) ■・・・・・・・・・
・Rear group, 2nd group (lens groups other than the focusing lens group)

Claims (1)

[Claims] In a zoom mechanism for a zoom lens that performs zooming by moving a plurality of lens groups including a focusing lens group in the optical axis direction, a first lens that drives the focusing lens group in the optical axis direction. a drive mechanism; a second drive mechanism that drives lens groups other than the focusing lens group in the optical axis direction; a drive source that provides driving force to the first and second drive mechanisms; and the first drive mechanism. A connecting mechanism that connects the mechanism and the drive source; and a switching means that connects the second drive mechanism and the drive source during zooming and releases the connection during focusing operation. The zoom mechanism of a zoom lens.