JPH04349412A - Zoom lens using screwing - Google Patents

Abstract

PURPOSE:To eliminate the jumping of a ball in a screwing mechanism and to accurately drive a lens. CONSTITUTION:In a mechanism which is constituted of a guiding bar 9 having a surface where spiral grooves are formed and a moving frame which is provided with a small hole and fitted in the guiding bar so that the ball is allowed to intervene between the small hole and a groove, and where the moving frame holding a ball frame, etc., is moved along the guide bar 9 by rotating the bar 9, the ball 15 positioned in the small hole of the moving frame is pressed to the groove of the bar 9 by an elastic member and the change of the elasticity of the elastic member equal to or above a specified amount is restrained in order to prevent the floating of the ball 15 from the bar 9.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens that uses a ball feed screw to drive the lens.

0002

2. Description of the Related Art When changing the zoom of a zoom lens, a plurality of lenses are driven in the direction of the optical axis of the lens. The driving method is to drive the lens groups into cam grooves formed in a cylindrical cam ring. The lens group is driven by engaging the lens frame and rotating the cam ring.

However, for example, in a two-component zoom lens, when changing the zoom, the amount of movement of the second lens group is generally large, and as a result, the length of the cam groove in the direction of the optical axis of the lens becomes long, making the design difficult. It becomes difficult. Therefore, a lens drive system using a feed screw as shown in FIG. 1 is used.

[0004] A ball feed screw (hereinafter referred to as a guide bar) 101 having a spiral groove 101a formed on its surface, a movable frame 102 fitted with the guide bar 101 and held so as not to rotate in the circumferential direction, and this movable frame. A ball 103 interposed between the hole formed in 102 and the groove 101a, and an L that presses this ball 103 into the groove 101a of the guide bar 101.
The movable frame 102, which holds the lens frame and the like, moves in the axial direction by rotating the guide bar. Y is a set screw for fixing the leaf spring 104 to the moving frame 102.

[0005]

[Problems to be Solved by the Invention] In this case, when an impact is applied to the lens or the like in the optical axis direction, the ball 103 is pushed downward in the figure against the bias of the leaf spring 104, and the ball 103
By floating up, it jumps over the adjacent groove 101a,
There is a problem in that if the moving frame itself moves in the optical axis direction, accurate zooming cannot be performed. The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a zoom lens using a screw feed that eliminates the ball jumping and allows the lens to be driven accurately.

[0006]

Means for Solving the Problems The present invention provides a guide bar having a spiral groove on its surface, a small hole, and a ball interposed between the small hole and the groove. A zoom lens consisting of a moving frame that fits into a bar, and using a screw feeding mechanism that moves the moving frame holding the lens frame etc. along the guide bar by rotation of the guide bar, and the small hole in the moving frame. The present invention is characterized in that an elastic member is provided to press the ball located at the guide bar into the groove of the guide bar, and a restraining means is provided to prevent the elastic member from being elastically deformed by more than a predetermined amount due to the ball lifting from the guide bar. .

[0007]

[Operation] According to the above structure, when an impact force is applied to the lens, etc. in the optical axis direction, and lateral stress is applied between the guide bar and the moving frame, the ball located in the groove of the guide bar is , receives a reaction force in the direction of jumping out of the groove. As a result, the ball tends to lift off from the guide bar, but this lifting is effectively suppressed by the elastic member whose elastic deformation is suppressed by the restraining means. As a deterrent measure,
A possible method is to lock one of the elastic members with a claw or the like, but preferred embodiments and modifications thereof will be described in detail in the following examples.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a sectional view showing an embodiment of a zoom lens using screw feed according to the present invention. It is a two-component zoom consisting of a first lens group Q1 consisting of L1 and L2 and a second lens group Q2 consisting of L3 to L5, and the aperture mechanism is also configured to move independently, as shown in Figure 3. It is assumed that the optical axis is driven individually in the optical axis direction as shown in FIG.

A fixed tube 2 is fixed to a mount 1 for attachment to a camera body (not shown), and an outer tube 3 is further secured with screws. The lens frame 4 of the first lens group Q1 is rotatably supported by the first moving frame 5 via a helicoid 4A formed therein. Two or three guide pins 6 are implanted in the first moving frame 5. The cam ring 7 is fixedly rotatable in the axial direction with respect to the fixed cylinder 2 by bayonet connection, and the guide pin 6 is located at the intersection of the cam groove of the cam ring 7 and the straight groove provided in the fixed cylinder 2. .

The focus ring 8 fits into a part of the fixed barrel 2, and its gear is connected to a focus motor (not shown), and is rotated by rotation from the motor. There is a notch 8A in a part of the circumference on the front side of this focus ring 8, and the claw part 4B of the lens frame 4 is housed here, and both are free in the axial direction but rotate together in the circumferential direction. do. Fixed tube 2
There are axial notches 2A and 2B in a part of the circumference, in which guide bars 9 and 10 are located parallel to the optical axis. These guide bars have holes 2C and 2D at the tip of the fixed cylinder 2,
Both ends are held in holes in a base plate 11 screwed to the fixed cylinder 2. Both guide bars 9 and 10 are each threaded with a certain lead and have gears 12 and 13 at their rear ends.

Second moving frame 1 holding second lens group Q2
4 is fitted with the guide bar 9 at its fitting hole 14A, and fitted into the protrusion 2E (Fig. 4) of the fixed tube 2 at its groove 14B (Fig. 4) in the optical axis direction. . In addition, the second moving frame 14
In this case, the groove 9 of the guide bar 9 is shown in detail in FIG.
A steel ball 15 is fitted into the hole formed in A and the second moving frame 14 without play, and the ball 15 is pressed in the direction of the groove 9A of the guide bar 9 by an L-shaped leaf spring 16. However, the difference from Fig. 1 is that this leaf spring 1
The other end of the plate spring 6 is locked by a protrusion X formed on the second moving frame 14, so that even if a downward force is applied to the ball 15 in the figure, the leaf spring 16 is not bent more than necessary.

The movable frame 17 for the diaphragm mechanism is fitted into the guide bar 10, but the fitting method is different from that of the second movable frame 14.
Since it is the same as , its explanation will be omitted. 18 is fixed cylinder 2
19 is a back adjustment washer. The first moving frame 5, the second moving frame 14, and the aperture moving frame 17 are shown in FIG.
As shown in FIG. 3, gears are interlocked from a zoom motor 20, and the rotation angle of the cam ring 7, the shape of the cam, the shape of the cam, and the distance between each gear are adjusted in order to move each group as shown in FIG. 3 by the rotation of the motor. The reduction ratio of the guide bars 9 and 10 and the leads of the screws of the guide bars 9 and 10 are determined as appropriate.

In the above configuration, first, during focusing, rotation is transmitted from the focus motor (not shown) to the gear of the focus ring 8 via the deceleration system, and this rotates the gear of the first lens frame 4.
It is transmitted to Since the first lens frame 4 is helicoidally coupled to the first movable frame 5, the first lens group Q1 is extended or retracted according to the lead of the helicoid.

During zooming, the lens frame 4 does not rotate and only moves in the axial direction, so no movement is transmitted to the focus ring 8. Zooming is performed by driving the zoom motor 20. This becomes the rotation of the gear 21 via the reduction system, where it is divided into a first group and a second group. The gear 21A meshes with the gear of the cam ring 7, and when the cam ring 7 rotates, the guide pin 6 located at the intersection of the cam on the cam ring 7 and the linear groove of the fixed cylinder 2
By moving back and forth, the first group moving frame 5 is given a desired movement.

On the other hand, when the guide bar 9 rotates due to the engagement between the gear 21C and the gear 12, the second moving frame 14 moves back and forth according to the lead of the groove. Similarly, the rotation is transmitted to the gear 13, and the aperture moving frame 17 also moves back and forth with respect to the second moving frame 14 at a different speed. Now, if the positions of the moving frames are determined relative to each other in the wide-angle state shown in FIG. 2, each moving frame will move while maintaining the relationship shown in FIG. 3 as the motor 20 rotates, thereby functioning as a zoom lens.

As can be seen from the mechanism shown in FIG.
Although the axial position of the moving frame 14 is determined, if a strong impact is applied to the lens group in the optical axis direction, the ball 15 will be pushed downward in the figure against the leaf spring 16, and the ball 15 will be pushed downward in the figure. It moves over the thread of the guide bar 9 (in this case, the part without the groove 9A) and moves to another groove 9A, and as a result,
It may happen that the second moving frame 14 deviates from the normal axial direction. As mentioned earlier, with this lens, the ball 1
5, the distance between the first lens group Q1 and the second lens group Q2 becomes incorrect and they no longer function as a zoom lens.

Therefore, in the present invention, as shown in FIG. 5, even if a force is applied to the ball 15 in the downward direction in the figure, the leaf spring 1
6 is locked at one end by a locking piece X formed on the second moving frame 14 to prevent it from bending downward.

Modifications of the configuration of FIG. 5 are shown in FIGS. 6 to 8. In FIG. 6, the leaf spring 16 is the same as that in FIG. Even if 15 were to be pushed downward, the protrusion Z
Since the ball 15 is engaged with the groove 9A, the ball 15 is prevented from jumping over the thread.

In FIG. 7, a second ball 15' is provided in place of the protrusion Z in FIG. 6, and the same effect as in FIG. 6 is aimed at. In FIG. 8, the leaf spring 15 is held down by the head Y' of the screw Y in order to prevent the leaf spring 15 from bending downward.

By the way, in this configuration, the movable frames are interlocked with each other by gears, and it is necessary to determine the relative positions of the movable frames at a reference position, for example at the wide end, during assembly. Assume that the first moving frame 5 is moved to the wide (wide-angle) end by turning the cam ring 7 until it hits a zoom stopper (not shown). At this time, after the blocks of the second moving frame 14 and the guide bar 9 are attached to the fixed cylinder 2, the first moving frame 1
Since the relationship between the second movable frame 14 and the second movable frame 14 is not accurate, it is necessary to make adjustments after the second movable frame 14 is attached. Therefore, Figure 9
, as shown in FIG. 10, in the gear 21, the gear 21C
is rotatable with respect to the axis of the gear 21, and after rotating the guide bar 9 with the cam ring 7 in contact with the stopper and adjusting the position of the second moving frame 14, the gear 21C is moved to the gear 2.
Screw it to the gear 21B that is integrated with 1.

Similarly, the position of the aperture mechanism is similar to that of the guide bar 10.
The gear 13 is made rotatable in the same way, and is fixed with screws after adjustment. In this lens, since the image point movement adjustment is performed by changing the distance between the first lens group Q1 and the second lens group Q2, this adjustment is also used for the above adjustment. For example, temporarily tighten the screws at the wide end, measure the back, and then measure the back (
Measure the lens back at the telephoto end, and adjust the amount of adjustment required at the second
After adjusting the amount of movement of the lens group Q2 by loosening the screw and rotating the guide bar 9, fix the screw again. Incidentally, the entire back adjustment is performed using an adjustment washer 19 provided between the mount 1 and the fixed cylinder 2.

FIG. 11 shows the present lens barrel turned to the telephoto side. As can be seen from this, the lens frame 4 and the aperture block 17 are extremely close to each other on the telephoto side. On the other hand, the first
The lens L2 of the lens group Q1 uses an aspherical lens, and in terms of lens performance, it is desirable to be able to remove the assembled lens L2 and rotate or replace it. An example of a lens holder 22 suitable for this purpose is shown in FIG.

A plurality of holes 22A are provided along the periphery of the lens holder 22, and the holes 22A consist of a wide hole 22B and a narrow hole 22C in the radial direction. On the other hand, on the side of the lens frame 4 to which the lens holder 22 is directed, a protruding piece 4C having a shape substantially equal to the hole 22C is formed. FIG. 13 shows the lens holder 22 being applied to the lens frame 4 so that the protruding piece 4C is positioned in the hole 22B, and FIG. 14 shows the lens holder 22 of FIG. 13 being rotated clockwise. The lens holder 22 is shown fixed to the lens frame 4 by rotating the protruding piece 4C to press fit it into the hole 22C, and then spreading out the head of the protruding piece 4C by hot caulking. According to this structure, the lens holder 22 can be easily removed by rotating the lens holder 22 in a counterclockwise direction, and the lens holder 4 side only needs to have a protruding piece 4C. Therefore, molding of the ball frame 4 itself becomes easy.

[0024]

As explained above, the present invention suppresses the elastic deformation caused by the reaction of the ball to the elastic member that presses the ball into the groove of the guide bar, so that the ball can be pushed away from the guide bar. This effectively suppresses the lifting of the ball, and therefore, even when an impact force is applied to the lens or the like in the optical axis direction, the problem of the ball jumping over the groove can be eliminated, and the lens can be driven accurately.

[Brief explanation of drawings]

[Figure 1] Cross-sectional view showing a conventional screw feeding mechanism

[Figure 2]
A sectional view of a zoom lens to which the screw feeding mechanism of the present invention is applied

[Figure 3] Diagram showing the movement of the lens group when zooming in the zoom lens in Figure 2

[Figure 4] Diagram of the zoom lens in Figure 2 viewed from the front

[Fig. 5] A sectional view showing an example of the screw feeding mechanism used in the zoom lens shown in Fig. 2.

[Fig. 6] A sectional view showing another embodiment of the screw feeding mechanism shown in Fig. 5.

[Fig. 7] A sectional view showing another embodiment of the screw feeding mechanism in Fig. 5.

[FIG. 8] A sectional view showing another embodiment of the screw feeding mechanism in FIG. 5.

[Figure 9] Diagram showing details of the guide bar drive part

[Figure 1
0] Plan view showing the gear in Figure 9

[Figure 11]
A cross-sectional view showing the state when the zoom lens in Figure 2 is set to the telephoto side.

[Fig. 12] A plan view showing the lens holder in Fig. 11.

[Figure 13] Diagram showing an example of how to use the lens holder in Figure 12

[
Figure 14: Diagram showing an example of how to use the lens holder in Figure 12

[Explanation of symbols]

1 Mount 2 Fixed tube 3 Outer cylinder 4 Ball frame 5 First moving frame 6 Guide pin 7 Cam ring 8 Focus ring 9 Guide bar 10 Guide bar 11 Base plate 12 Gear 13 Gear 14 Second movement frame 15 Ball 16 Leaf spring 17 Aperture movement frame 19 Back adjustment washer 20 Zoom motor 21 Gear 22 Lens holder

Claims (1)

[Claims] 1. A guide bar having a spiral groove on its surface; and a moving frame having a small hole and fitting the guide bar with a ball interposed between the small hole and the groove. This is a zoom lens that uses a screw feed mechanism that moves a movable frame that holds the lens frame etc. along the guide bar by rotating the guide bar, and the ball located in the small hole of the movable frame is moved A zoom lens using screw feed, characterized in that an elastic member is provided to press the groove, and a restraining means is provided to prevent the elastic member from being elastically deformed by a predetermined amount or more due to the lifting of the ball from the guide bar.