KR20090081855A - Lens Displacement Mechanism Using Shape Memory Alloy - Google Patents

Abstract

A lens displacement mechanism using a shape memory alloy (SMA) applied to a lens module of autofocus is disclosed. This lens displacement mechanism includes at least one SMA wire. The two opposing ends of the SMA wire are fixed and the longitudinal intermediate point of the intermediate moving part between the two opposite ends is on a corresponding hook disposed on the outer edge of the lens such that the intermediate moving part is tightened between the two opposite ends. It is fixed to tighten. When the SMA wire is heated, the intermediate moving portion contracts to pull the hook of the lens, thereby moving and sliding the lens along the optical axis to achieve auto focus control. The lens displacement mechanism is simple in structure and reflow process. Therefore, the lens displacement mechanism is suitable for use in portable cameras, mobile phones or PDAs which are compact and need to be easily mass produced by SMT.

Description

Lens displacement mechanism using shape memory alloy {LENS DISPLACEMENT MECHANISM USING SHAPED MEMORY ALLOY}

The present invention relates to a lens displacement mechanism using a shape memory alloy (SMA), in particular such a mechanism is applied to a lens module of autofocus and lens displacement using an SMA to control the forward / rear movement of the lens for the zoom function. It's about the mechanism.

Portable electronic devices, such as digital cameras, mobile phones with camera functions, or notebooks currently available, are generally arranged with compact cameras with an autofocus function (AF), so-called internally focused lens modules. The lens module with auto focus is basically composed of a housing, a lens and a lens displacement mechanism. The lens consists of a lens holder and a lens group. The lens holder and lens group are mounted in the housing. The lens displacement mechanism is used to move or slide the lens away from the object or along the optical axis by screw rotation for auto focus control. Conventional lens displacement mechanisms consist of piezoelectric motors formed by piezoelectric materials. However, typical piezoelectric materials could not withstand the high temperatures of the reflow process. Once a special piezoelectric material is used that can withstand high temperatures, the cost is very expensive. The other component, ie the voice coil motor (VCM), uses a magnetic force and comprises an elastic part. However, under the high temperature of the reflow process, the voice coil motor can be damaged or the magnetic force is reduced. Therefore, the reflow process is not used while assembling the piezoelectric motor or the voice coil motor. Therefore, this makes mass production difficult. Furthermore, an SMA device formed of a shape memory alloy is used. The lens can be moved by the principle of heat shrink and cold expansion. The amount of shrinkage and expansion of the SMA device is about 5% much more effective than that of ordinary materials. Furthermore, SMA devices can withstand the high temperatures of the reflow process so that the reflow process can be applied when assembling an autofocus lens module. Therefore, the SMA device is practical and the assembly efficiency is improved.

US Patents US5,185,621, US5,279,123, US5,459,544, US6,307,678, US6,449,434, US2002 / 0136548, US2007 / 0058070, US2007 / 0047938; WO2005 / 001540; Japanese Patent JP64-000938, JP09-127398, JP62-067738, JP03-196781, JP2006-329111, JP2005-275270, JP2005-195998, JP2005-156892, JP2004-184775, JP2004-129950, JP2004-069986, JP2004-038058, JP2000-056208; Reference is made to Taiwanese patents TWM242178, TW200710464 and the like, which are all prior art for SMA devices in a lens displacement mechanism. Although they all use SMA devices as the driving source of lens displacement, the disclosed techniques and driving methods are different. However, most of these are complex in design and large in volume, and do not meet the requirements of the compact design of the lens module. Referring to US Pat. No. 6,449,434, SMA wire is used. The two ends of the SMA wire are fixed and the intermediate moving part hooked on the pivot actuator. A protruding pin is arranged on the outer edge of the actuator to lock into the slot on the outer edge of the lens holder as a stress point. The heat shrink and cold expansion of the SMA wire allows the actuator to be pivoted at an angle. At the same time, the protruding pin is also pivoted to pivot the lens holder at an angle. Thus, by another factor, the lens holder is moved for the focusing function. It is found that the driving force comes from the SMA wire and these prior arts still require some other interlocking device such as an actuator, trigger or other leverage having a similar function to drive the lens holder. This interlocking device is disposed between the SMA wire and the lens holder so that the contracting force of the SMA is converted into a driving force for moving the lens holder through the interlocking device. Therefore, the movement and structure of the lens displacement mechanism is too complicated, which not only induces a negative effect on the design requirements and low cost of the compact lens module, but also has the disadvantage of mass production by Surface-Mount Technology (SMT). Therefore, there is still an improvement.

Therefore, the basic object of the present invention is to provide a lens displacement mechanism applied to a lens module of the auto focus function. At least one shape memory alloy (SMA) wire is arranged symmetrically or equidistantly around the lens. The two opposing ends of the SMA wire are fixed and the longitudinal midpoint of the intermediate moving part between the two opposite ends is a corresponding hook disposed on the outer edge of the lens holder such that the intermediate moving part is tightened with respect to the two opposite ends ( bent to tighten on the hook). When the SMA wire is heated with the inflow of control current, the intermediate moving portion contracts to pull the hook and thereby drive the lens to move or slide along the optical axis. Thus, the auto focus function is achieved.

It is another object of the present invention to provide a lens displacement mechanism using a shape memory alloy further comprising a recovery spring element disposed on the lens. When the control current is interrupted, the SMA wire cools and expands back to its original length. The recovery spring element then drives the lens back to its original position and provides the lens with the retraction force in the opposite direction to the traction force of the retracted SMA wire so that autofocus is achieved.

It is yet another object of the present invention to provide a lens displacement mechanism using a shape memory alloy comprising corresponding guide rails and guide slots arranged between the lens and the edge of the housing to reliably move and slide the lens within the housing. It is.

The present invention provides a lens of an autofocus function comprising a housing, a lens having at least one lens group and a lens holder, and a lens displacement mechanism arranged along the optical axis and moving and sliding toward and vice versa toward the object side for the autofocus function. A lens displacement mechanism using a shape memory alloy applied to a module, comprising: at least one shape memory alloy (SMA) wire; The SMA wire is controlled by a control current to slide and move the lens; The SMA wire has an intermediate moving portion between these two opposite ends with two opposite ends and two opposite ends fixed, the longitudinal intermediate point of the intermediate moving portion being intermediate moving between the two opposite ends. Bent on a corresponding hook arranged on the outer edge of the lens to tighten the portion; When the SMA wire is heated by the inflow of control current, the intermediate moving portion provides a lens displacement mechanism, which is contracted to pull the hook of the lens to move and slide the lens on the optical axis for the auto focus function. .

The present invention can provide a lens displacement mechanism having the advantages of simple movement and structure, compact design, low cost, and mass production.

The lens displacement mechanism using the shape memory alloy of the present invention is applied to the lens module of the auto focus function. The shape or structure of the lens or the housing of the lens module is not limited here. For example, the lens may comprise a lens group having a single lens or a plurality of lenses. A single lens or group of lenses can be set in the fixing member and then assembled through the lens holder to form the lens. In addition, there is no restriction on the lens holder as long as the lens holder can be fitted with a cover, an inner space, a housing, or other parts of the lens module. There is no limit to the number of molded memory alloy (SMA) wires and the number of lenses driven thereby. There are many driving methods for driving a lens by SMA wire, driving a lens by a plurality of SMA wire sets, or driving a plurality of lenses by a plurality of SMA wire sets.

1 to 3, the lens displacement mechanism 1 of the present invention is applied to the lens module 2 of the auto focus function. The lens module 2 of the auto focus function includes at least one housing 20 for mounting the lens 21 moving along the optical axis X. There is no restriction on the structure and assembling method of the lens 21 here. In general, the lens 21 is composed of a lens group 22 and a lens group 22 having a single lens or a plurality of lenses (for example two lenses).

In the lens displacement mechanism 1, the lens 21 is driven to slide and move by at least one SMA wire 10 with the characteristics of temperature change as well as cold expansion after thermal contraction and conduction. When the SMA wire 10 exhibits martensite / austenite deformation characteristics, when the SMA wire 10 is heated by the introduction of a control current, it exhibits a heat shrinkage behavior between the austenite start temperature and the austenite end temperature, and the SMA wire When (10) is cooled by the current interruption, it exhibits cold expansion behavior between the martensite start temperature and the martensite end temperature.

The SMA wire 10 comprises two opposing ends 11 and an intermediate moving portion 12 located between these two opposing ends 11. The two opposing ends 11 are fixed somewhere, such as a frame 24 surrounding the housing 20 of the lens module 2 of auto focus. There is no limitation on the method of fixing the opposite end 11 to the frame 24. This fastening method can be fixed by clips, adhesives or welding and can be done easily. The longitudinal intermediate point 13 of the intermediate moving portion 12 is bent to tighten on the corresponding hook 25. This hook 25 is arranged on the outer edge of the fixing member of the lens group 22 or on the outer edge of the lens holder 23 such that the intermediate moving part 12 is tightened between two opposing ends 11. . According to the above structure, when the SMA wire 10 is heated by the inflow of the control current, the intermediate moving portion 12 of the SMA wire 10 is contracted and pulls the hook 25, which causes the lens 21 to have an optical axis X. Is driven to slide and move along. Thus, the auto focus function is achieved.

In the present invention, the number of SMA wires 10 and the method of arranging each SMA wire 10 around the lens 21 are not limited. The number of SMA wires 10 may be one (1), two (2) or four (4) in various embodiments.

First embodiment

1 to 3, one SMA wire 10 is used in this embodiment. When the zoom function is operated from tele to wide, the lens 21 is moved away from the image side and closer to the object side. While the zoom function is operating, the lens 21 moves under the control of the focus button (not shown in the figure). When the user presses the focus button, the lens displacement mechanism 1 obtains a control current passing from the electrodes 31 and 32. After the control current passes through the SMA wire 10, Joule heat is generated due to the resistance of the SMA wire 10. Thus, the SMA wire 10 is heated to shrink. Due to the linear relationship between the length, temperature and control current of the SMA wire 10, the displacement of the lens 21 can be controlled in accordance with the contraction of the SMA wire 10. Thus, the distance between the lens 21 and the image forming surface is changed, thereby achieving the auto focus function. In this embodiment, the SMA wire 10 is made of a nickel-titanium alloy having a diameter of 0.002 ". The distance change and control current between the lens 21 and the image forming surface are shown in Table 1.

Table 1

Distance of the object (mm) 70 100 600 1000 Infinity

Lens shift (mm) 0.243 0.167 0.023 0.011 0

Control Current (mA) 50 35 20 15 0

There is no limitation on the power supply structure and / or electrical connection of the lens displacement mechanism 1 of the present invention.

The lens displacement mechanism 1 further comprises a recovery spring element 30, such as a clip or spring, disposed on the lens 21. When the control current decreases, the SMA wire 10 is inflated again with the recovery spring element 30 providing a recovery force in the opposite direction to the pulling force of the cooled and retracted SMA wire 10. This means that the direction of the restoring force is opposite to the displacement direction of the lens 21 which is pulled by the contraction of the intermediate moving part 12 so that the lens 21 is returned to the parallel position again. The type of recovery spring element 30 can be a compression spring or an extension spring, with no limitation on the number or placement position. For example, the compression spring may be provided on the object side at the top of the lens 21 and the lens 21 to provide the lens 21 with the force of the compression spring opposite to the traction of the retracted SMA wire 10. Arranged between the covers (not shown in the figure). Or an extension spring is provided at the bottom of the lens 21 to provide the lens 21 with the force of the extension spring in the direction opposite to the pulling force of the retracted SMA wire 10 to move the lens 21 back to its original position. Are arranged.

Furthermore, a set of guide rail devices 26 is disposed between the lens 21 and the housing 20. The guide rail device 26 includes a guide slot 261 and its corresponding guide rail 262, which allow the lens 21 to stably move and slide in the housing 20 by the guide rail device 26. It is arranged between the housing 27 and the frame 27 adjacent to or connected to the lens 21. The position and the number of the guide rail devices 26 are not limited.

Second embodiment

4 to 6, this embodiment includes two SMA wires 10. The two SMA wires 10 are arranged symmetrically or equidistantly around the lens 21. The driving method and function of each SMA wire 10 are the same as those of the first embodiment. The recovery spring element 30 is disposed in the lens 21 to provide a recovery force in the opposite direction to the pulling force of the retracted SMA wire 10 to return the lens 21 back to the equilibrium position.

Furthermore, the guide rail device 26 is arranged between the lens 21 and the housing 20. The guide rail device 26 is arranged on one side between the two SMA wires 10 such that the lens 21 is stably moved and slides in the housing 20 by the guide rail device 26.

Or two guide rail devices 26 are arranged between the lens 21 and the housing 20. The two guide rail devices 26 are arranged symmetrically according to the position of the two SMA wires 10. As shown in FIGS. 4-6, the two SMA wires 10 are arranged symmetrically, while the two guide rail devices 26 are arranged symmetrically (not shown in the figure). Two SMA wires 10 and two guide rail devices 26 may also be arranged adjacent to each other. For example, two SMA wires 10 are arranged on two adjacent sides of a rectangular frame, while two guide rail devices 26 are arranged on the other two adjacent sides. The purpose of the arrangement of the guide rail device 26 is to allow the lens 21 to stably move and slide in the housing 20. In general, the two SMA wires 10 of the second embodiment provide better traction than one SMA wire 10 of the first embodiment.

Third embodiment

7-9, this embodiment includes four SMA wires 10. Four SMA wires 10 are arranged symmetrically or equidistantly around the lens 21. For example, SMA wires 10 are each arranged on four sides of the lens 21. The driving method and function of each SMA wire 10 are the same as those of the second embodiment. Further, the recovery spring element 30 is disposed on the lens 21 to provide a recovery force in the opposite direction to the pulling force of the retracted SMA wire 10 to return the lens 21 back to the equilibrium position.

In this embodiment, four SMA wires 10 are respectively disposed on the four sides surrounding the lens 21 to provide an equal contraction and traction force to the lens 21. Thus, the lens 21 moves stably in the housing 20. Basically, it is not necessary to add the guide rail device 26 to this embodiment. Furthermore, an image quality feedback mechanism is added once to control and adjust the four SMA wires 10 to finely adjust the tilt of the lens 21 to improve image quality.

Compared with the prior art, the present invention provides the following advantages:

(1) The SMA wire 10 of the present invention is driven to move and slide the lens 1 directly without other interlocking devices such as an actuator and a trigger to simplify the structure and movement of the lens. Thus, compact lens modules and low cost requirements are met, which provides a positive effect on mass production.

(2) The present invention can withstand the high temperatures of the reflow process so that there is a higher possibility of mass production.

(3) The longitudinal intermediate point 13 of the intermediate moving part 12 of the SMA wire 10 according to the present invention is such that the SMA wire 10 forms a V-shaped structure and a longer range is obtained. It is bent to tighten on the corresponding hook 25 of 21. This means that by the same SMA wire 10 the same SMA wire 10 of the present invention provides a greater range of displacement for the lens 21. Furthermore, a feedback mechanism on the circuit is used to control the length-temperature-resistance of the SMA wire 10 to finely adjust the displacement of the lens 21. The focusing position of the lens is thus precisely controlled.

(4) If at least two SMA wires 10 are arranged symmetrically or equidistantly around the lens 21 as shown in the third embodiment, a suitable image quality feed back mechanism is inclined of the lens 21. It is used to individually control each SMA wire 10 to modify the tilt, yaw or pitch.

Those skilled in the art will be able to facilitate additional advantages and modifications. Thus, the invention is not limited in its broadest aspects to the specific details and representative devices shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

As described above, the present invention is applicable to the lens module of the auto focus function.

1 is a perspective view of one embodiment according to the present invention.

2 is a schematic view showing a top view of the embodiment of FIG.

3 is a schematic view showing a side view of the embodiment of FIG.

4 is a perspective view of another embodiment according to the present invention.

5 is a schematic view showing a top view of the embodiment of FIG. 4.

6 is a schematic view showing a side view of the embodiment of FIG. 4.

7 is a perspective view of another embodiment according to the present invention.

8 is a schematic view showing a top view of the embodiment of FIG.

9 is a schematic view showing a side view of the embodiment of FIG.

Claims (9)

Applied to an autofocus lens module comprising a housing, a lens having at least one lens group and a lens holder, and a lens displacement mechanism arranged along the optical axis and moving and sliding towards and / or away from the object side for autofocus function In the lens displacement mechanism using the shape memory alloy, A lens displacement mechanism having at least one shape memory alloy (SMA) wire; The SMA wire is controlled by a control current to slide and move the lens; The SMA wire has an intermediate moving portion between these two opposite ends with two opposite ends and two opposite ends fixed, the longitudinal intermediate point of the intermediate moving portion being intermediate moving between the two opposite ends. Bent on a corresponding hook arranged on the outer edge of the lens to tighten the portion; And when the SMA wire is heated by the introduction of a control current, the intermediate moving portion contracts to pull the hook of the lens to move and slide the lens on the optical axis for the auto focus function. The method of claim 1, wherein the at least one SMA wire is arranged symmetrically or equidistantly around the lens, with two opposite ends of each SMA wire having corresponding hooks with intermediate moving portions disposed on the outer edge of the lens. And the lens displacement mechanism is fixed in a state of being bent tightly on. 2. The recovery spring element of claim 1 wherein the recovery spring element is disposed on the lens such that when the control current is reduced, the SMA wire is cooled and inflated again, the recovery spring element being retracted to drive the lens back to its equilibrium position. A lens displacement mechanism, characterized by providing a lens with recovery force in the opposite direction of traction. 2. The lens displacement mechanism of claim 1 wherein the two opposing sides of the SMA wire are fixed on a frame at an outer edge of the housing of the lens module. 5. The lens displacement mechanism of claim 4, wherein the two opposing sides of the SMA wire are fixed by clips, adhesives, or welding. The lens displacement mechanism of claim 1, wherein a guide rail device is disposed between the lens and the housing. 7. The frame of claim 6, wherein the guide rail device comprises a guide slot and a guide rail, the guide slot and the guide rail being on a frame with the guide rail and the guide slot at the outer edge of the housing of the lens module and the outer edge of the lens. Lens displacement mechanism, characterized in that assembled to correspond to each other in a state arranged in each. 7. The lens displacement mechanism of claim 6, wherein at least one set of guide rail devices is disposed between the lens and the housing. 9. The apparatus of claim 8, wherein the two sets of guide rail devices are disposed on a lens displacement mechanism corresponding to two SMA wires with two SMA wires arranged on two adjacent sides surrounding the lens. Two sets of guide rail devices are disposed on opposite sides of two SMA wires.

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