Lens driving device

Abstract

A lens driving device includes a lens barrel having a lens holder and an extension part extended from the lens holder. The device also includes a piezoelectric vibrator with a piezoelectric body flexed and bent in response to power application with a friction member in contact with the extension part, thereby providing driving power for transporting the lens barrel. The device further includes a preload member having a free end in resilient contact with a rear end of the piezoelectric body to compress the piezoelectric vibrator against the extension part and a guiding part for guiding the transport of the lens barrel in the optical axis direction. This allows a simplified and miniaturized structure, a large transport range with low input power to achieve excellent resolution of positioning, minimal loss of driving power, simplified mechanism for guiding the transport of the lens, and accurate and stable transport of the lens.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a sectional view illustrating a conventional lens driving device using a cam;

FIG. 2 is a sectional view illustrating a conventional lens driving device using a screw;

FIG. 3 a is an overall plan view illustrating a conventional lens driving device using a piezoelectric element and FIG. 3b is a partially exploded perspective view illustrating the same;

FIG. 4 is a perspective view illustrating a lens driving device according to the present invention;

FIG. 5 is an exploded perspective view illustrating the lens driving device according to the present invention;

FIG. 6 is a side view illustrating the lens driving device according to the present invention;

FIG. 7 is a plan view illustrating the lens driving device according to the present invention;

FIG. 8 is a detailed view illustrating the connection between a piezoelectric vibrator, an extension part and a guiding part provided in the lens driving device according to the present invention;

FIG. 9 illustrates a bearing member provided in the lens driving device according to the present invention, in which (a) is a perspective view and (b) is a sectional view;

FIG. 10 is a sectional view illustrating the contact status between a second guiding pillar and a second guide groove provided in the lens driving device according to the present invention;

FIG. 11 illustrates the piezoelectric vibrator provided in the lens driving device according to the present invention, in which (a) illustrates a piezoelectric body in a flexural mode in a longitudinal direction, (b) illustrates the piezoelectric body in a bending mode in a thickness direction and(c) illustrates the piezoelectric body in a mixed state of the bending and flexural modes; and

FIG. 12( a) and (b) are conceptual views illustrating internal and external electrodes and vibration modes of the piezoelectric vibrator adopted in the lens driving device according to the present invention.

Claims

1. A lens driving device comprising: a lens barrel comprising a lens holder for holding at least one lens therein and an extension part extended from the lens holder;a piezoelectric vibrator comprising a piezoelectric body for being flexed and bent in response to power application and a friction member disposed at a leading end thereof to be in contact with the extension part, the piezoelectric vibrator providing driving power necessary for driving the lens barrel;a preload member having a free end thereof in resilient contact with a rear end of the piezoelectric body to maintain a compressed contact status between the extension part of the lens barrel and the friction member of the piezoelectric vibrator, the preload member providing resilient force that compresses the piezoelectric vibrator against the extension part; anda guiding part for guiding the movement of the lens barrel in the optical axis direction.

2. The lens driving device according to claim 1, wherein the piezoelectric vibrator comprises a piezoelectric ultrasonic motor having a plurality of piezoelectric layers stacked in a bending direction to produce at least two vibration modes through internal and external electrode structures.

3. The lens driving device according to claim 1, wherein the lens barrel further comprises a friction member provided on the vertical surface of the extension part, the friction member disposed perpendicular with the friction member of the piezoelectric vibrator to form a contact therebetween.

4. The lens driving device according to claim 3, wherein the friction member is disposed in a groove depressed in the vertical surface of the extension part.

5. The lens driving device according to claim 3, wherein the friction member of the extension part has a height that is 1.5 times a transfer distance of the lens barrel.

6. The lens driving device according to claim 1, wherein the preload member comprises a plate spring having a free end in resilient contact with a rear end of the piezoelectric vibrator while having a fixed end fixed to a base where the piezoelectric vibrator is disposed and a protrusion protruding from a surface of the free end thereof so as to be in point contact with the rear end of the piezoelectric vibrator.

7. The lens driving device according to claim 1, wherein the preload member has a length longer than that of the piezoelectric vibrator.

8. The lens driving device according to claim 1, wherein the guiding part comprises a first guide rod having a predetermined length disposed vertically in a first guide groove formed in a potion of the extension part to be movable on a bearing member and a second guide rod having a predetermined length disposed vertically in a second guide groove formed in another portion of the extension part.

9. The lens driving device according to claim 8, wherein the bearing member comprises upper and lower ball pairs in point contacts with outer surfaces of the first guide groove and outer surfaces of the first guide rod and a retainer having a plurality of upper and lower ball grooves in which the upper and lower balls are rotatably disposed.

10. The lens driving device according to claim 9, wherein the upper and lower balls and the first guide rod are disposed at positions corresponding to respective vertexes of a triangle.

11. The lens driving device according to claim 8, wherein the first guide rod has a center flush with the point of contact between the friction member of the piezoelectric vibrator and the friction member of the extension part.

12. The lens driving device according to claim 8, wherein the point of contact between the friction member of the piezoelectric vibrator and the friction member of the extension part is flush with the point of contact between the free end of the preload member and the piezoelectric vibrator.

13. The lens driving device according to claim 8, wherein the second guide rod is disposed in the second guide groove having a rectangular section such that the second guide rod is in point contact with an inner projection protruding from an inner surface of the second guide groove.

14. The lens driving device according to claim 1, further comprising a base on which the lens barrel is mounted, wherein the base comprises a vertical rib for fixing the piezoelectric body of the piezoelectric vibrator, a fixing groove in which the fixed end of the preload member is fixed and a fixing hole in which a lower end of the guiding part is fixed.

15. The lens driving device according to claim 14, wherein the vertical rib comprises a resilient fixing member extending vertically from a lower surface thereof which is in contact with a lower end of the piezoelectric body to have a resilient contact with opposed outer surfaces of the piezoelectric body.

16. The lens driving device according to claim 14, wherein the vertical rib has a fixing plate disposed in contact with an upper surface of the piezoelectric body so as to prevent upward disengagement and play of the piezoelectric vibrator.

17. The lens driving device according to claim 14, wherein the fixing groove is provided between a pair of fixing ribs provided in a corner of the base to form a gap in which the fixed end of the preload member is fixedly inserted.

18. The lens driving device according to claim 1, further comprising an indicator provided at a surface of the lens barrel and a location sensor for sensing a location of the indicator upon vertical movement thereof.