KR101234952B1 - Lens driving mechanism for digital camera - Google Patents

Abstract

The present invention provides a digital camera comprising: a support having a vertical through hole formed at one side of an upper and a lower surface thereof, a guide shaft coupled to a vertical through hole of the support, and a piezoelectric element transmitting a driving force to the guide shaft through a bearing ball; A driving part mounted on the support and including a preload spring elastically fixing the piezoelectric element; And a lens group coupled to the driving unit, the lens group including a plurality of lenses.

Description

Lens driving device for digital camera {LENS DRIVING MECHANISM FOR DIGITAL CAMERA}

The present invention relates to a lens driving apparatus for a digital camera, and more particularly, to a lens driving apparatus for a digital camera that enables autofocus or optical zoom by moving a lens group or a lens of a digital camera using a piezoelectric element.

The global digital still camera (DSC) market is estimated at about 140 million units (as of 2009) due to the increase in demand of existing users as well as existing experts. Recently, new demand (women) is expanding in DSC, and as new functions such as video are added, repurchase and additional purchase are being made. In addition, related companies are expanding their low-priced models to secure a wide range of purchasers from beginners to experts. Reflecting such market conditions, researches on compact and convenient hybrid digital cameras, including the functions of the existing Digital Still Camera (DSC), are being actively conducted, starting with the Olympus PEN series.

Driving mechanisms for implementing functions such as auto focus, optical zoom, shutter, and image stabilization (OIS) of digital cameras include stepping motors, VCMs, and piezoelectric ultrasonic motors. A typical double stepping motor is used. However, due to the disadvantages of high power consumption, size, and noise, it is disadvantageous for long time use, compact size, and video shooting. On the contrary, the piezoelectric ultrasonic motor converts simple vibrations such as contraction and expansion generated when electricity is applied to the piezoelectric ceramics into circular (or linear) motions by friction between the stator and the mover (or the rotor). Compared to the electromagnetic drive motor, it has the advantages of high energy density, fast response speed, high position precision and off power holding function, as well as low noise during operation and no influence of electromagnetic waves.

Accordingly, the present invention was devised to solve the above-mentioned disadvantages and problems in the conventional lens driving apparatus, by moving a lens group or a lens (hereinafter referred to as 'lens group') of a digital camera by using a piezoelectric element. It is a device that enables auto focus or optical zoom. In particular, it is an object of the present invention to reduce the size of the lens driving unit by being suitable for the driving device of the digital camera, and to provide effects such as precision driving and driving noise reduction at low voltage.

The object of the present invention is a lens driving device for a digital camera, in a digital camera, a support having a vertical through hole formed on one side of the upper and lower surfaces, a guide shaft coupled to the vertical through hole of the support, and the guide shaft. A driving part including a piezoelectric element for transmitting a driving force through a bearing ball, and a preload spring mounted on the support to elastically fix the piezoelectric element; And a lens group coupled to the driving unit and including a plurality of lenses. A lens driving apparatus for a digital camera is provided.

In addition, the support may move vertically along the guide axis.

In addition, an insertion groove into which the piezoelectric element and the bearing ball may be inserted may be formed at one side of the support.

In addition, the support may be coupled to the lens group by screwing, bonding or axial connection.

In addition, a position sensor may be included on one side of the support.

In addition, the piezoelectric element may include a piezoelectric body, a friction member, and an electrode part.

In addition, the preload spring may be composed of a leaf spring to provide an elastic force to the piezoelectric element.

In addition, the preload spring may be provided with upper and lower locking jaws for coupling to the support.

In addition, the guide shaft may be in contact with the friction member of the piezoelectric element and the bearing ball.

In addition, the lens group may form a support on both sides of the lens group.

The lens driving device for a digital camera of the present invention is an apparatus that enables auto focus or optical zoom by moving a lens group of a digital camera by using a piezoelectric element. In particular, the driving device of the digital camera using the piezoelectric element is to reduce the size of the lens driving unit, and to provide effects such as precision driving and driving noise reduction at low voltage. More specifically, in the situation where the requirements for digital cameras are becoming smaller and slimmer, the use of piezoelectric elements can reduce the size of the digital cameras significantly, rather than using a small stamping motor.

1 is a perspective view illustrating a conventional digital camera lens driving apparatus.
2 is a perspective view illustrating the piezoelectric element.
3 to 5 are perspective views illustrating a lens driving apparatus for a digital camera according to an embodiment of the present invention.

Embodiments of the present invention will be described in detail with reference to the drawings of a lens driving apparatus for a digital camera. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention.

Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the size and thickness of an apparatus may be exaggerated for convenience. Like numbers refer to like elements throughout.

The digital camera of the present invention detects an image using an electronic sensor without a film, and stores the image information in a digital image file format such as JPEG, TIFF, Raw format, GIF, or a digital video file format such as MPEG, DV, MJPEG, or the like. A camera is referred to as a "digital video camera" for which the main purpose of motion picture shooting is referred to as a "digital still camera". Digital cameras are usually referred to as "digital still cameras." However, the present invention is not limited to the type of digital camera.

The basic photographing principle of the digital camera of the present invention is that the light received through the lens touches an image sensor (eg, a CCD image sensor or a CMOS image sensor) that serves as a film of a general film camera.

The image sensor detects photons and converts them into electrical signals (charge = electric charge), and the detected light is converted into digital information such as brightness, color, and coordinates according to intensity and position. The converted information is passed to an image processing engine, which reconstructs it into a digital image. The obtained image is converted into an image file format (eg, raw, jpg) and stored in a storage device such as a flash memory.

In addition, as shown in FIG. 1, the stepping motor 130 and the DC motor 140 are variously used to implement the optical zoom 100, the shutter 110, and the auto focus 120 of the basic digital camera. However, because the power consumption of the stepping motor 130 is about 500mW per piece, it is difficult to use the digital camera for a long time due to the high power consumption, and because it uses a gear for driving, it is not only a problem such as noise and reaction speed, but also stepping Using multiple motors has made it difficult to achieve miniaturization of digital cameras.

The present invention relates to implementing an optical zoom and an auto focus function by driving a lens group or a lens of a digital camera by friction of mechanical vibration generated in the piezoelectric element 220. The piezoelectric actuator method provided can reduce the size of the lens driving unit 200 compared to the existing stepping motor 130, and has advantages such as precision driving and driving noise reduction at low voltage.

As shown, the lens driving unit 200 according to the embodiment of the present invention is largely the support 210, the guide shaft 240 coupled to one side to the support 210, the piezoelectric element in contact with the guide shaft 240 ( 210 and the bearing ball 250, the support 210 and the piezoelectric element 210 is fixed to the pre-loading spring 230, the lens driving unit 200 and the lens group 300 is coupled to one side.

The support 200 has a vertical through hole 211 formed on one side of the upper and lower surfaces so that the guide shaft 240 penetrates, and the guide shaft 240 and the guide shaft inserted into the vertical through hole 211. The support 210 moves up and down along the guide shaft 240 by the piezoelectric element 220 in contact with the 240, and the guide shaft 240 is fixed to one side of the digital camera. The shaft 240 may be formed of a material of Tunsten Carbide (WC), but is not limited thereto.

In addition, the support 210 has an insertion groove 213 is formed to be inserted into the piezoelectric element 220, the insertion groove 213 includes the vertical through hole 211, the piezoelectric element The bearing groove 250 that helps the support 210 to move up and down along the guide shaft 240 is provided on the insertion groove 213 surface of the friction member 222 side to which the 220 is coupled. Bearing ball grooves 212 that can be coupled are formed, and the bearing ball grooves 212 are formed on one side of the insertion groove 213, but the number of bearing ball grooves 212 and the bearing ball 250 is limited Not.

The bearing ball 250 is mainly composed of a ball bearing to reduce the friction force by rolling in the bearing ball groove 212 on one side of the insertion groove 213, the support 210 by the piezoelectric element 220 guide shaft It is possible to smoothly follow Shanghai along 240.

An outer side of the insertion groove 213 is formed with a coupling groove 214 to which the preload spring 230 can be coupled, and a sensor groove into which the position sensor 260 can be inserted at one side of the support 210. 215 is formed.

In addition, the support 210 is to form a coupling protrusion 216 toward the lens group 300, the support 210 for coupling with the lens group 300 to be described later, the coupling protrusion 216 The lens group 300 is coupled to the lens group 300, and the coupling method may include various methods such as bonding, screw coupling, or shaft coupling, but is not particularly limited to the coupling method.

In addition, the support 210 and the lens group 300 has a structure that can be separated according to the situation, it is possible to obtain ease of assembly, in the integrated structure of the support 210 and the lens group 300 By easily replacing when the support 210 is defective, it is possible to reuse the expensive lens group 300.

The piezoelectric element 220 includes a piezoelectric member 221, a friction member 222, and an electrode part (not shown).

The piezoelectric element 220 generates an elliptic trajectory on the outer surface of the piezoelectric ceramics by applying an electrical signal to the piezoelectric element 210 which simultaneously generates two vibration modes (length vibration and bending vibration) at a specific frequency. When the piezoelectric element 210 (Piezoelectric Ceramic) vibrating in this manner is pressed onto the guide shaft 240 by the preload spring 230, the lens group is driven in the vertical direction by friction.

As shown in FIG. 3, the preload spring 230 is fixed to the support 210 to press the preload spring 230 toward the piezoelectric element 220 to maintain contact with the guide shaft 240. It is a preload spring 230 to provide a constant strength of the elastic force.

The preload spring 230 is provided as a plate spring that provides an elastic force toward the piezoelectric element 220. When the preload spring 230 is employed in the form of at least one leaf spring, an image of the preload spring 230 is applied. The lower locking jaws 231 and 232 are fixed to the left and right sides of the support 210, and the elastic surface 233 connecting between the upper and lower locking jaws 231 and 232 is opposite to the friction member 222. In contact with the outer surface of the corresponding piezoelectric element 220 is provided to elastically support the piezoelectric element 220 toward the guide shaft 240. Here, it is preferable that the left and right locking jaws 231 and 232 of the preload spring 230 are bent inwardly so as to be caught and fixed to the left and right sides of the support 210. It is preferable to protrude an embossed portion (not shown) in point contact with the outer surface of the element 130. In addition, the preload spring 230 is illustrated and described as being provided in the form of a leaf spring, but is not limited thereto.

The lens group 300 may be configured as a lens stack (not shown) in which a plurality of lenses are stacked. The incident light passing through the lens group may be incident by adjusting a focus with an image sensor (not shown).

In addition, the lens group 300 and the support 210 are moved up and down along the guide shaft 240 by the force of the piezoelectric element 220 applied to the guide shaft 240.

The support 310 may be formed on both sides of the lens group such that the tilt and warp do not occur when the lens group 300 moves up and down by the support 210.

The foregoing detailed description is illustrative of the present invention. In addition, the foregoing description merely shows and describes preferred embodiments of the present invention, and the present invention can be used in various other combinations, modifications, and environments. That is, it is possible to make changes or modifications within the scope of the concept of the invention disclosed in this specification, the disclosure and the equivalents of the disclosure and / or the scope of the art or knowledge of the present invention. The foregoing embodiments are intended to illustrate the best state in carrying out the present invention, and to utilize other inventions such as the present invention in other conditions known in the art, as well as in specific applications and uses of the invention. Various changes are possible. Accordingly, the detailed description of the invention is not intended to limit the invention to the disclosed embodiments. Also, the appended claims should be construed as including other embodiments.

100: optical zoom
110: Shutter
120: auto focus
130: stepping motor
140: DC motor
200: lens driving unit
210: support
220: piezoelectric element
230: preload spring
240: guide shaft
250: bearing ball
260: position sensor
300: lens group
310: Support

Claims (10)

In a digital camera,
A support having a vertical through hole formed at one side of each of the upper and lower surfaces thereof;
A guide shaft coupled to the vertical through hole of the support;
Piezoelectric element for transmitting the driving force through the bearing ball to the guide shaft;
A driving part mounted to the support and including a preload spring elastically fixing the piezoelectric element; And
And a lens group coupled to the driving unit and including a plurality of lenses.
A position sensor is installed at one side of the support, and the position sensor is configured to move up and down together as the support moves up and down along the guide shaft.
An insertion groove is formed in the support to allow the piezoelectric element to be inserted, and an inner surface of the insertion groove is formed with a bearing ball groove to which a bearing ball to help the support move up and down along the guide shaft is coupled. Lens drive device for digital camera.
The method of claim 1,
The support is a lens driving device for a digital camera to move vertically along the guide axis
delete The method of claim 1,
And the support is coupled to the lens group by screwing, bonding or axial connection.
delete The method of claim 1,
The piezoelectric element includes a piezoelectric body, a friction member, and an electrode unit.
The method of claim 1,
The preload spring is a lens driving device for a digital camera composed of a leaf spring for providing an elastic force to the piezoelectric element.
The method of claim 1,
The preload spring is a lens driving device for a digital camera having upper and lower locking jaw for coupling to the support.
The method of claim 1,
And the guide shaft is in contact with the friction member of the piezoelectric element and the bearing ball.
The method of claim 1,
The lens group is a lens driving device for a digital camera to form a support on both sides of the lens group.

Images