PATENT DOCUMENT

Publication Number: US-8711495-B2
Application Number: US-201213632965-A
Country: US
Kind Code: B2

Title: MEMS autofocus actuator

Abstract:
A micro-electro-mechanical systems (MEMS) autofocus actuator having a support member for supporting a lens element, the support member including a stationary portion and a movable portion, the movable portion attached to the stationary portion by a movable support beam. An electrostatic drive member is attached to the stationary portion and the movable portion to drive movement of the movable portion with respect to the stationary portion. A lens holder is suspended within the support member by a resilient arm member attached to the movable portion and a deflection beam attached to the stationary portion so that in a non-actuated state, the lens element is in a first focal position that is substantially out-of-plane with respect to the stationary portion, and in an actuated state, the lens element is in a second focal position, the second focal position being different from the first focal position.

Claims:
What is claimed is: 
     
       1. A micro-electro-mechanical systems (MEMS) autofocus actuator comprising:
 a support member for supporting a lens element, the support member having a stationary portion and a movable portion, the movable portion attached to the stationary portion by a movable support beam; 
 an electrostatic drive member having a first portion attached to the stationary portion and a second portion attached to the movable portion to drive movement of the movable portion with respect to the stationary portion; and 
 a lens holder suspended within the support member, the lens holder suspended by a resilient arm member attached to the movable portion and a deflection beam attached to the stationary portion, wherein the deflection beam is dimensioned to deflect when a lens element is inserted within the lens holder so that in a non-actuated state, the lens element is in a first focal position that is substantially out-of-plane with respect to the stationary portion, and in an actuated state, the lens element is in a second focal position, the second focal position being different from the first focal position. 
 
     
     
       2. The autofocus actuator of  claim 1  wherein the electrostatic drive member is one of a plurality of comb drives radially spaced around the lens holder. 
     
     
       3. The autofocus actuator of  claim 1  wherein the first focal position is a position for focus at infinity and the second focal position is a position for closer focus. 
     
     
       4. The autofocus actuator of  claim 1  wherein the second position is substantially in-plane with respect to the stationary portion. 
     
     
       5. The autofocus actuator of  claim 1  wherein the lens holder comprises a ring member dimensioned to encircle the lens element and a radial support member extending into the ring member from the deflection beam to radially suspend the lens element within the ring member. 
     
     
       6. The autofocus actuator of  claim 4  wherein the resilient arm member comprises a spring member that expands in response to in-plane movement of the ring member when the lens element is inserted into the ring member to prevent in-plane movement of the electrostatic drive member. 
     
     
       7. The autofocus actuator of  claim 1  wherein the lens holder, the resilient arm and the deflection beam are integrally formed as a single unit with the support member from a silicon wafer. 
     
     
       8. The autofocus actuator of  claim 1  wherein the deflection beam is one of a plurality of deflection beams radially spaced around the lens holder and wherein each of the plurality of deflection beams is dimensioned to deflect when a lens element is inserted within the lens holder. 
     
     
       9. The autofocus actuator of  claim 1  wherein the movable support beam is a first movable support beam, the autofocus actuator further comprising a second movable support beam, the second movable support beam attached to the movable portion at an end opposite the first movable support member so that the second portion of the electrostatic drive member is movably suspended in front of the first portion. 
     
     
       10. The autofocus actuator of  claim 1  further comprising:
 a stationary alignment beam extending from the stationary portion and positioned between the movable support beam and the deflection beam to minimize in-plane movement of the lens holder. 
 
     
     
       11. The autofocus actuator of  claim 1  wherein the autofocus actuator is incorporated into a camera module of a mobile communications device. 
     
     
       12. The autofocus actuator of  claim 1  wherein the lens element is a single lens of a lens stack. 
     
     
       13. A micro-electro-mechanical systems (MEMS) autofocus actuator comprising:
 an electrostatic drive member having a stationary drive portion and a movable drive portion, the movable drive portion capable of moving with respect to the stationary drive portion, the stationary drive portion mounted to a substantially planar support member such that the stationary drive portion is within a plane of the planar support member and the movable drive portion is capable of moving in a direction normal to the plane; 
 a lens holder dimensioned to receive a lens element, the lens holder mounted to the movable drive portion such that movement of the movable drive portion drives movement of the lens holder in a direction parallel to an optical axis of the lens element; and 
 a plurality of deflection beams extending from the planar support member to the lens holder, the plurality of deflection beams dimensioned to frictionally suspend the lens element within the lens holder, wherein the plurality of deflection beams are biased in an out-of-plane position when the lens element is inserted within the lens holder. 
 
     
     
       14. The autofocus actuator of  claim 13  wherein the electrostatic drive member is one of a plurality of comb drives radially spaced around the lens holder. 
     
     
       15. The autofocus actuator of  claim 13  wherein the electrostatic drive member is configured to move the lens element in a direction parallel to the optical axis when a voltage is applied to the electrostatic drive member. 
     
     
       16. The autofocus actuator of  claim 13  wherein when the deflection beams are biased in the out-of-plane position, the lens element within the lens holder is in a first focal position. 
     
     
       17. The autofocus actuator of  claim 16  wherein the lens element is capable of moving to a second focal position when a voltage is applied to the electrostatic drive member, the second focal position different than the first focal position. 
     
     
       18. The autofocus actuator of  claim 13  further comprising:
 an in-plane stationary member dimensioned to minimize lateral movement of the lens element. 
 
     
     
       19. An autofocus actuator comprising:
 a plurality of drive members mounted within an opening of a substantially planar support member, each of the drive members having a stationary drive portion and a movable drive portion, the movable drive portion capable of moving with respect to the stationary drive portion, and wherein the stationary drive portion is within a plane of the planar support member and the movable drive portion is capable of moving in a direction normal to the plane; 
 a plurality of deflection beams positioned between the plurality of drive members and extending radially inward of the plurality of drive members to form an annular opening within the support member, the annular opening dimensioned to receive a lens element; and 
 a lens mounting member having a lens support member dimensioned to encircle a lens element positioned within the annular opening and a plurality of resilient arm members radially spaced around the lens support member and attached to a respective movable drive portion, and wherein the plurality of deflection beams and the movable drive portion are biased in an out-of-plane position when the lens element is inserted within the annular opening. 
 
     
     
       20. The actuator of  claim 19  wherein the lens element is in a first position when the movable drive portion is in the out-of-plane position, and when a voltage is applied to the plurality of drive members, the movable drive portion moves the lens element to a second different position. 
     
     
       21. The actuator of  claim 19  wherein each of the plurality of deflection beams have alternatively curved regions disposed along their length to help minimize in-plane bending along the beams.

Description:
FIELD 
     An embodiment of the invention is directed to a micro-electro-mechanical system (MEMS) autofocus actuator for a camera module that may be integrated within an electronic device such as a smartphone. Other embodiments are also described and claimed. 
     BACKGROUND 
     Miniature cameras are becoming increasing common in mobile electronic devices such as smartphones. There is a constant drive to improve performance of such cameras, whilst ideally maintaining the same envelope. One feature augmentation that is now standard in such miniature cameras is autofocus. The incumbent actuator technology for such cameras is the voice coil motor (VCM). Many other technologies have been proposed over the last few years, with varying strengths and weaknesses and differing degrees of commercial success. The VCM technology has the key advantage of being simple, and therefore being straightforward to design. Whilst there are several disadvantages of VCM, such as high power, and low relative force, their use persists. One technology that has showed promise over the last few years is silicon micro-electro-mechanical systems (MEMS). 
     The MEMS technology is based around the philosophy of the electrostatic comb drive. The magnitude of actuation movement achievable with such a small-scale silicon device is less than that required to move the whole lens in such miniature cameras. The MEMS technology allows focusing of the camera between the notional infinity object distance and 10 cm focal distance, which is the typical specification for most devices. In addition, the cost of the MEMS actuator is almost entirely proportional to the surface area of silicon per device since MEMS devices are manufactured at the wafer level. As such, current MEMS devices mount a single lens element from the multi-element lens stack typically found in such miniature camera lenses. By choosing a lens element with high optical power, and hence a small relative focal length, the actuation movement is reduced. Since a single lens element is mounted in the actuator, the size of the silicon actuator can also be minimized. 
     As compared with VCM, the MEMS technology benefits from requiring very little power, a factor that is increasingly important in mobile devices. In addition, owing to the small size and stiff silicon structure, the mechanical resonance is much higher, delivering much faster response speed and focusing time, and also better stability for different camera orientations. There are two key factors, however, that have prevented the MEMS technology from being a practical commercial success. The first is that the actuator has thus far failed to survive the very difficult impact and drop testing that mobile devices require. In addition, moving a single lens element increases the complexity of the lens assembly and means that the actuator assembly and lens assembly are no longer separated, but integrated. This presents manufacturing problems. 
     SUMMARY 
     An embodiment of the invention is an autofocus actuator for a camera module that may be integrated within a miniature camera. The actuator may include one or more electrostatic drive members, such as a comb drive, attached to a silicon MEMS structure. The silicon MEMS structure may be fabricated to include a stationary portion and a movable portion that is moved by one or more of the drive members with respect to the stationary portion. A lens holder may be attached to the movable portion of the MEMS structure such that movement of the drive member moves a lens positioned within the lens holder in a direction parallel to its optical axis. To drive movement, the two halves of the drive member (fixed and moving portions) are displaced relative to one another orthogonally to the plane of the MEMS structure (i.e. parallel to the optical axis of the lens). Displacement is achieved when the lens is inserted into the MEMS structure. 
     Representatively, the MEMS structure may include a plurality of deflection beams that extend from an outer portion of the MEMS structure radially inward to a lens holder. The deflection beams may be arranged in a planar configuration (e.g., within the plane of the MEMS structure) and with some degree of rotational symmetry about the lens holder. The act of inserting the lens within the lens holder applies an outward force on the deflection beams. In-plane loading of the beams in this manner, causes the beams to snap out of the MEMS structure plane. This in turn displaces a moving portion of the drive member from its fixed portion in a direction parallel to the optical axis. The actuator is considered to be in a non-actuated or steady-state configuration when the deflection beams are deflected so that the two halves of the drive member are displaced relative to each other along the optical axis. Application of a voltage to the drive member will draw the drive member movable portion toward the fixed portion, which in turn causes movement of the associated lens member in a direction parallel to the optical axis to a desired focal position. 
     The MEMS structure may further include stationary beams and/or resilient members between the movable and/or stationary portions in order to prevent in-plane or lateral movement of the drive member portions and the lens holder. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  is a side cross-sectional view of one embodiment of an autofocus actuator positioned within a mounting case. 
         FIG. 2A  is a side cross-sectional view of one embodiment of an autofocus actuator in a non-actuated state. 
         FIG. 2B  is a side cross-sectional view of one embodiment of an autofocus actuator in an actuated state. 
         FIG. 2C  is a side cross-sectional view of one embodiment of an autofocus actuator in the non-actuated state. 
         FIG. 3  is a top plan view of one embodiment of an autofocus actuator. 
         FIG. 4A  is an exploded top plan view of the arrangement of the stationary components illustrated in  FIG. 3 . 
         FIG. 4B  is an exploded top plan view of the arrangement of the movable components illustrated in  FIG. 3 . 
         FIG. 4C  is an exploded top plan view of the arrangement of the deflection beams illustrated in  FIG. 3 . 
         FIG. 5  is a perspective view of the autofocus actuator of  FIG. 1 . 
         FIG. 6  is a perspective view of one embodiment of an implementation of an autofocus actuator within a mobile device. 
     
    
    
     DETAILED DESCRIPTION 
     In this section we shall explain several preferred embodiments of this invention with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1  is a cross-sectional view of one embodiment of an autofocus actuator. Autofocus actuator  100  may be used to drive movement of a lens element within a camera, for example a miniature camera, integrated within an electronic device. In one embodiment, the electronic device may be a mobile device including, but not limited to, a mobile phone such as a smart phone, a tablet computer, a laptop computer or the like. Autofocus actuator  100  may include a support or base member  102  for supporting each of the components of the autofocus actuator. In one embodiment, support member  102  may be a MEMS autofocus actuator formed from a substantially planar silicon wafer. Representatively, the silicon wafer may undergo various etching and deposition processes to produce each of the associated components that will be described in more detail below. In this aspect, the autofocus actuator  100 , including its stationary and movable components, may be one integrally formed structure that is formed as a single unit thus reducing manufacturing time and costs. The silicon wafer may also be fabricated so that support member  102  includes metallic electrode layers to route electrical connections between various contact points along or within support member  102 . 
     Support member  102  may have any size and dimensions suitable for supporting the autofocus actuator components within a camera, particularly a miniature camera mounted within a mobile device. It is further to be understood that the size of support member  102  may be scaled to accommodate a desired application. In one embodiment, support member  102  may be mounted within the desired device, for example a miniature camera, by mounting front case  109  and/or back case  111  surrounding support member  102  within the camera module. It is recognized, however, that front case  109  and/or back case  111  may be optional, and omitted in some embodiments, in which case, support member  102  may be directly mounted within the camera module. 
     Lens element  103  may be suspended within support member  102  between deflection beam  118  and a resilient arm  116  attached to electrostatic actuator  106 . Deflection beam  118 , resilient arm  116  and electrostatic actuator  106  may movably mount lens element  103  with respect to support member  102  such that it can move in a direction parallel to its optical axis  115 . In other words, lens element  103  moves in a direction normal to the plane of support member  102 . 
     In one embodiment, lens element  103  is a single lens element of a lens stack that is mounted within a camera. Representatively, as illustrated in  FIG. 1 , lens element  103  is mounted within autofocus actuator  100 . Lens stack  105 , which includes lens elements  105 A,  105 B and  105 C, and image sensor  107  are mounted behind lens element  103 . The object of interest  119  is positioned in front of lens element  103 . According to this arrangement, when lens element  103  is in the resting position, it is at a focal position of maximum focus distance, i.e., a position for focus at infinity. Thus, adjusting lens element  103  in a direction of arrow  117  moves lens element  103  closer to the object of interest and decreases the focus distance so that the associated camera can focus on objects, which are outside of the focus distance when lens element  103  is in the resting state. This second focal position can be any focal position other than the focal position for focus at infinity. Representatively, when power is applied to actuator  100 , lens element  103  moves in a direction of arrow  117  to any number of focal positions within the range of movement. The range of movement is preferably any range which ensures that deflection beam  118  remains in a deflected or biased position. For example, the range of movement may be between the resting focal position illustrated in  FIG. 1  (see also  FIG. 2A ) and the plane of support member  102 . 
     Movement of lens element  103  may be driven by electrostatic actuator  106 . In one embodiment, electrostatic actuator  106  may be a comb drive having a stationary drive portion  108  and a movable drive portion  110 . Stationary drive portion  108  and movable drive portion  110  may include fingers, as will be described in more detail in reference to, for example  FIG. 3 , which interlock with one another to drive movement of stationary drive portion  108  with respect to movable drive portion  110 . Representatively, in one embodiment, stationary drive portion  108  is mounted to support member  102  while movable drive portion  110  is suspended in front of stationary drive portion  108  such that the application of a voltage moves movable drive portion  110  in a direction of arrow  117  while stationary drive portion remains stationary. 
     To move movable drive portion  110  in the desired direction when a voltage is applied, movable drive portion  110  must be displaced with respect to stationary drive portion  108  in the resting or non-actuated state as illustrated by  FIG. 1  such that application of pulls movable drive portion  110  toward stationary drive portion  108 . Displacement of movable drive portion  110  with respect to stationary drive portion  108  is achieved by deflection beam  118 . In particular, in one embodiment, deflection beam  118  is an elongated structure that extends radially inward from support member  102  to lens element  103 . Deflection beam  118  may frictionally engage with the edge of lens element  103  such that when lens element  103  is loaded into support member  102  in a downward direction (i.e., toward lens stack  105 ), lens element  103  applies an outward force to deflection beam  118 . In one embodiment, the force moves deflection beam  118  radially outwards. Since this force is in turn applied along a length of deflection beam  118 , the beam becomes unstable and buckles. This creates a bi-stable configuration in which the beam snaps out of plane, notionally in either direction. The direction of deflection may be controlled by the direction of insertion of the lens element. In this case, the deflection beam  118  buckles in a downward direction, which in turn displaces movable drive portion  110  below stationary drive portion  108 . Movable drive portion  110 , and in turn lens element  103 , will remain in this position until a voltage sufficient to overcome the downward force of deflection beam  118  and pull movable drive portion  110  toward stationary drive portion  108  is applied. 
     It is important that deflection beam  118  remain in some degree of the buckled configuration during operation. To maintain the buckled configuration, the range of movement of lens element  103  may be limited using any suitable limiting structure or system. For example, in one embodiment, front case  109  having retaining arms  113 A,  113 B is positioned along the front face of support member  102 . Retaining arms  113 A,  113 B are positioned above resilient arm  116  and deflection beam  118  and extend down into the plane of support member. Retaining arms  113 A,  113 B are dimensioned to contact and stop deflection beam  118  and resilient arm  116  from passing above the support member plane as movable drive portion  110  drives lens element  103  in a direction of arrow  117 . This in turn, limits the movement of lens element  103  to just below the plane of support member  102 . A back case  111  may further be attached to a bottom face of support member  102  such that actuator  100  is enclosed within front case  109  and back case  111 . 
     It is contemplated that any other suitable structure or system may be implemented to limit the range of movement of lens element  103  so that deflection beam  118  remains in a deflected state which is below the plane of support member  102 . For example, a single retaining arm that limits movement of movable drive portion  110  may be used. Alternatively, the voltage applied to actuator  100  may be controlled so as not to raise deflection beam  118  beyond the desired deflected position. 
     Although  FIG. 1  illustrates lens  103  in a focal position for focus at infinity in the resting or non-actuated state, it is further contemplated that actuation of autofocus actuator  100  may be required to position lens element  103  in the focus at infinity focal position. Representatively, the deflection beam  118  may be deflected in an opposite direction to that shown in  FIG. 1 . Thus, in the resting or non-actuated state, deflection beam  118  may be deflected in a direction toward the object of interest  119 . To move lens element  103  away from the object of interest  119 , i.e., toward the focal position for focus at infinity illustrated in  FIG. 1 , actuator must be actuated by applying a voltage. 
       FIGS. 2A-2C  illustrate the autofocus actuator of  FIG. 1  during operation. In  FIG. 2A , autofocus actuator  100  is in the resting or non-actuated state. Deflection beam  118  is therefore in the buckled or deflected configuration and pulls lens element  103  out-of-plane. This in turn, causes movable drive portion  110  to become displaced in a direction parallel to optical axis  115  such that it is below stationary drive portion  108 . Lens element  103  remains in this position until a voltage or power is supplied to electrostatic actuator  106 . 
     Once a voltage is applied, attractive electrostatic forces are created between movable drive portion  110  and stationary drive portion  108  causing them to be drawn together. It is noted that a voltage, which creates electrostatic forces greater than the downward deflection forces applied by deflection beam  118 , should be used. The voltage may be an alternating current (AC) or direct current (DC). Since stationary drive portion  108  is fixedly attached to support member  102 , movable drive portion  110  is drawn in an upward direction along arrow  202  toward support member  102 . This, in turn, moves lens element  103  upward toward the plane of support member  102  as illustrated in  FIG. 2B . Movement of lens element  103  in the direction of arrow  202  can be controlled by controlling the driving voltage. Representatively, metallic electrode layers formed in support member  102  may form metallic traces, which route electrical connections between electrostatic actuator  106  and a power source (e.g., a battery). A driving voltage may be transmitted from the power source to actuator  106  to actuate actuator  100 . Actuator  100  is considered to be in an actuated state when the driving voltage is applied. 
     Once the voltage is removed, movable drive portion  110  is no longer attracted to stationary drive portion  108 . The biasing downward force of deflection beam  118  therefore pulls movable drive portion  110  in a downward direction of arrow  204  and, in turn, lens element  103  back to the resting or non-actuated position as illustrated in  FIG. 2C . 
     With the above-discussed general operation of autofocus actuator  100  in mind, specific details of each of the above-described actuating components and their operation will now be described in reference to  FIG. 3  to  FIG. 5 .  FIG. 3  is a top plan view of one embodiment of an autofocus actuator such as that generally described in reference to  FIG. 1 . Representatively,  FIG. 1  may be understood as generally illustrating a cross-sectional side view of autofocus actuator  100  of  FIG. 3  along line A-A′. It is noted that autofocus actuator  100  is substantially symmetrical about any of lines A-A′, B-B′ or C-C′ illustrated in  FIG. 3  therefore a similar configuration and operation as described in reference to  FIG. 1  applies to any of the other components illustrated along lines B-B′ and C-C′ of  FIG. 3 . 
     As previously discussed, autofocus actuator  100  may be used to drive movement of a lens element within a camera, for example a miniature camera, integrated within an electronic device. Autofocus actuator  100  may include a support or base member  102  for supporting each of the components of the autofocus actuator. In one embodiment, support member  102  may be a micro-electro mechanical systems (MEMS) autofocus actuator formed from a substantially planar silicon wafer. The silicon wafer may also be fabricated so that support member  102  includes metallic electrode layers to route electrical connections between various contact points along or within support member  102 . 
     Support member  102  may have any size and dimensions suitable for supporting the autofocus actuator components within a camera, particularly a miniature camera mounted within a mobile device. Representatively, in one embodiment, support member  102  has a hexagon like shape with a width of from about 3 mm to about 6 mm and a thickness of from about 10 microns to about 14 microns, for example 12 microns. Other sizes and shapes, however, are contemplated, for example support member  102  may alternatively have a square, circular, triangular or rectangular shape depending upon the dimensions of the miniature camera. It is further to be understood that the size of support member  102  may be scaled to accommodate a desired application. 
     A lens holder  104  dimensioned to hold a lens element is movably mounted within an opening formed in the center of support member  102 . Lens holder  104  is movably mounted such that it can move in a direction parallel to an optical axis of the lens element positioned therein. In other words, lens holder  104  moves in a direction normal to the plane of support member  102 . In one embodiment, lens holder  104  includes a lens ring  140  dimensioned to encircle a lens element. 
     Lens ring  140  may be a substantially circular structure dimensioned to receive a similarly shaped lens element. Representatively, in one embodiment, lens ring  140  may be formed by two concentric rings connected together at one or more points around the ring. A recess may be formed around the annular inner surface of the inner ring such that the lens element can be press-fit within the lens ring  140 . 
     Lens ring  140  can be moved in a direction parallel to the optical axis of the lens element mounted therein to focus the lens element using one or more actuators, for example, electrostatic actuators  106 A,  106 B and  106 C. Although three electrostatic actuators  106 A,  106 B and  106 C are illustrated, it is contemplated that less than three or more than three actuators may be attached to lens ring  140 . In particular, any number of electrostatic actuators capable of being separately controlled and simultaneously moving a lens element in a direction parallel to an optical axis may be used. In addition, it is preferred that the electrostatic actuators be capable of compensating for any misalignment of the lens element, e.g., lens tilt. In this aspect, electrostatic actuators  106 A,  106 B and  106 C may be evenly spaced around lens ring  140  so that the planar orientation of lens ring  140  is maintained (i.e., does not tilt) as it moves along the optical axis. Alternatively, in other embodiments where tilting of the lens element within lens ring  140  is desirable, electrostatic actuators  106 A,  106 B and  106 C may be positioned such that actuation of one or more of the actuators can be used to tilt the lens element to a desired degree. Movement of electrostatic actuators  106 A,  106 B and  106 C may be controlled by applying a same voltage simultaneously to each of the actuators or separately applying the same or different voltage to each, depending upon the desired degree of movement. Representatively, during an autofocus operation in which an even movement of the lens element in a direction parallel to the optical axis is desired, a same voltage may be applied simultaneously to each of actuators  106 A,  106 B and  106 C. Where it is desired to tilt the lens element, different voltages may be applied to one or more of actuators  106 A,  106 B and  106 C, or a voltage may be applied to one and not to another. In this aspect, it is to be understood that one or more of actuators  106 A,  106 B and  106 C may be separately and independently controlled from another. 
     Electrostatic actuators  106 A,  106 B and  106 C may be any type of electrostatic actuator capable of driving movement of lens ring  140  along the optical axis of a lens element positioned therein. In one embodiment, electrostatic actuators  106 A,  106 B and  106 C are comb drives that include a stationary drive portion and a movable drive portion. More specifically, electrostatic actuator  106 A includes stationary drive portion  108 A and the movable drive portion  110 A. Stationary drive portion  108 A and movable drive portion  110 A are capable of moving relative to one another. Although the following discussion will focus on the operation of electrostatic actuator  106 A, it is to be recognized that electrostatic actuators  106 B and  106 C are substantially similar to electrostatic actuator  106 A. Therefore the operations of stationary drive portion  108 B and movable drive portion  110 E of electrostatic actuator  106 B and stationary drive portion  108 C and movable drive portion  110 C of electrostatic actuator  106 C, are substantially the same as that described in reference to actuator  106 A. 
     Representatively, in one embodiment, the stationary drive portion  108 A is fixedly mounted (e.g. bonded) to a stationary portion  112  of support member  102 . An opening may be formed within a center of stationary portion  112  for receiving stationary drive portion  108 A. Stationary drive portion  108 A may be mounted within the opening so that it is substantially within the plane of support member  102  and stationary portion  112 . 
     Movable drive portion  110 A may be mounted to a movable portion  114 A of support member  102  that extends in front of stationary drive portion  108 A. Movable portion  114 A is suspended in front of stationary drive portion  108 A by support beams  122 A and  124 A. Similarly, movable drive portion  110 E may be suspended in front of stationary drive portion  108 B by support beam  122 B and support beam  124 B. Movable drive portion  110 C may be suspended in front of stationary drive portion  108 C by support beam  122 C and support beam  124 C. Support beams  122 B,  124 B,  122 C and  124 C are substantially similar to support beams  122 A and  124 A therefore the description provided herein with respect to support beams  122 A and  124 A applies to support beams  122 B,  124 B,  122 C and  124 C. 
     Support beams  122 A and  124 A extend from stationary portion  112  of support member  102  to opposing sides of movable portion  114 A. Movable drive portion  110 A is therefore positioned in front of stationary drive portion  108 A and is movable with respect to stationary drive portion  108 A. 
     Although in the illustrated embodiment, movable drive portion  110 A moves while stationary drive portion  108 A remains stationary, other configurations are contemplated. For example, relative movement between movable drive portion  110 A and stationary drive portion  108 A may include movement of stationary drive portion  108 A while movable drive portion  110 A remains fixed. 
     Movable drive portion  110 A is attached to lens ring  140  of lens holder  104  by resilient arm  116 A. Resilient arm member  116 A absorbs movement of lens ring  140  in a direction perpendicular to the optical axis (i.e., in-plane movement) in order to prevent in-plane misalignment of movable drive portion  110 A with respect to stationary drive portion  108 A. Movement of movable drive portion  110 A in a direction parallel to the optical axis moves lens ring  140  in a direction parallel to the optical axis of the lens element mounted within lens holder  104 . Movement of the lens element along the optical axis allows for focusing of the lens element at different positions. In order to drive movement of movable drive portion  110 A in a direction parallel to the optical axis, movable drive portion  110 A is displaced with respect to stationary drive portion  108 A along the optical axis. For example, stationary drive portion  108 A is at an in-plane position with respect to support member  102  and movable drive portion  110 A is out-of-plane. 
     Autofocus actuator  100  therefore also includes deflection beam  118 A attached to lens holder  104  to bias lens holder  104 , and in turn movable drive portion  110 A, in an out-of-plane position in the non-actuated state. In other words, in the non-actuated state, movable drive portion  110 A and stationary drive portion  108 A are displaced relative to each other along the optical axis. The term non-actuated state is meant to refer to a resting state of electrostatic actuator  106 A in which no power or voltage is being supplied. When a voltage is applied to electrostatic actuator  106 A, movable drive portion  110 A is drawn toward stationary drive portion  108 A. This in turn moves lens holder  104  along the optical axis. The voltage may be an alternating current (AC) or direct current (DC). 
     Deflection beam  118 A is an elongated structure that extends from stationary portion  112  of support member  102  to lens ring  140 . Additional deflection beams  118 B and  118 C may also extend from stationary portion  112  to lens ring  140 . Deflection beams  118 A,  118 B and  118 C may be evenly spaced around lens ring  140  such they provide a symmetrical force around lens ring  140 . Although three deflection beams  118 A,  118 B and  118 C are illustrated, any number of beams capable of symmetrically balancing a radial load and deflection out-of-plane are contemplated. For example, four or more deflection beams evenly spaced around lens ring  140  may be used. 
     Each of deflection beams  118 A,  118 B and  118 C may include support ends  120 A,  120 B and  120 C which extend radially inward within lens ring  140 . Support ends  120 A,  120 B and  120 C are dimensioned to frictionally engage and suspend a lens element positioned within lens ring  140 . In one embodiment, support ends  120 A,  120 B and  120 C may include a serrated surface to enhance the engagement between support ends  120 A,  120 B and  120 C and the associated lens. It is contemplated, however, that other engagement enhancing features or structures may be formed at support ends  120 A,  120 B and  120 C. For example, knobs or a gripping or adhesive type material may be formed at support ends  120 A,  120 B and  120 C. 
     Support ends  120 A,  120 B and  120 C may be dimensioned to define an annular space within lens ring  140  having a diameter slightly less than the diameter of the lens element. Thus, inserting the lens element within lens ring  140  applies an outward force to support ends  120 A,  120 B and  120 C. In one embodiment, the force moves the support ends  120 A,  120 B and  120 C radially outwards about 15 microns to about 25 microns, for example, about 20 microns. Since this force is in turn applied along a length of deflection beams  118 A,  118 B and  118 C, the beams become unstable and buckle. Since deflection beams  118 A,  118 B and  118 C are arranged in a planar configuration, which has some degree of rotational symmetry, and the beams are loaded in the plane of support member  102 , a bi-stable configuration is created in which the beams can snap out of plane, notionally in either direction. The direction of deflection may be controlled by the insertion of the lens element as will be described in more detail in reference to  FIG. 5 . 
     Representatively, once the lens element is assembled as illustrated in  FIG. 5 , the steady-state configuration of autofocus actuator  100  is with deflection beams  118 A,  118 B and  118 C deflected or biased so that the movable drive portion  110 A and the stationary drive portion  108 A are displaced relative to each other along the optical axis  115 . This approach greatly simplifies the structure and assembly process of autofocus actuator  100 . In so doing, it also allows the MEMS structure to be designed to isolate the MEMS functions more effectively, and allows beams  118 A,  118 B and  118 C to be designed to appropriately survive the drop test. 
     Each of the movable beams, namely deflection beams  118 A,  118 B and  118 C; and support beams  122 A,  122 B,  122 C,  124 A,  124 B,  124 C, may have a similar shape and dimensions. The shape and dimensions may be any shape and dimensions sufficient to allow the movable beams to flex, bend or deflect out-of-plane as previously discussed while still remaining substantially rigid to in-plane or lateral movements. In this aspect, each of deflection beams  118 A,  118 B and  118 C; and support beams  122 A,  122 B,  122 C,  124 A,  124 B,  124 C can have an in-plane shape which includes one or more (e.g., three), alternatively curved regions disposed along its length. The curvature helps to minimize in-plane or lateral bending along the beam while still allowing the beam to respond to any minimal in-plane forces elastically, as opposed to breaking or cracking. 
     It is further contemplated that since each of the movable beams are fabricated from a silicon wafer as previously discussed, they may have the same thickness as the wafer. Representatively, deflection beams  118 A,  118 B and  118 C; and support beams  122 A,  122 B,  122 C,  124 A,  124 B,  124 C may have a thickness of for example, from about 10 microns to about 14 microns, for example 12 microns. Still further, deflection beams  118 A,  118 B and  118 C; and support beams  122 A,  122 B,  122 C,  124 A,  124 B,  124 C may have a width of from about 50 to about 150 microns, for example, from about 75 microns to about 100 microns and a length of from about 0.5 mm to about 2 mm, for example, from about 0.75 to about 1.75, for example, 1.5 mm or 1.3 mm. Each of deflection beams  118 A,  118 B and  118 C; and support beams  122 A,  122 B,  122 C,  124 A,  124 B,  124 C may have the same shape and dimensions, or alternatively, one or more of these structures may have a different shape and/or dimensions from the other. 
     In the illustrated embodiment, deflection beams  118 A,  118 B and  118 C have a forked configuration with each of the fork legs having the above-described curvatures and dimensions. 
     It is further noted that although support beams  122 A,  122 B,  122 C,  124 A,  124 B and  124 C have similar dimensions to deflection beams  118 A,  118 B and  118 C, they are not loaded in-plane to any significant degree. Support beams  122 A,  122 B,  122 C,  124 A,  124 B and  124 C are also configured such that they do not substantially reduce the out-of-plane deflection of deflection beams  118 A,  118 B and  118 C (which are loaded in-plane). Also, the in-plane movement of deflection beams  118 A,  118 B and  118 C does not substantially affect in-plane movement of support beams  122 A,  122 B,  122 C,  124 A,  124 B and  124 C. Thus, undesirable in-plane movement of deflection beams  118 A,  118 B and  118 C will not cause misalignment of movable drive portions  110 A,  110 B and  110 C connected to their respective support beams. 
     Autofocus actuator  100  further includes in-plane beams  126 A and  128 A, which serve to minimize lateral or in-plane movement of the movable components (e.g., deflection beams  118 A,  118 B,  118 C, movable drive portions  110 A,  110 B,  110 C and support beams  122 A,  122 B,  122 C,  124 A,  124 B and  124 C). This aspect is particularly important since autofocus actuator  100  may be implemented within a mobile device, which must be operable even after being dropped on a hard surface. In particular, manufacturing specifications require that mobile devices withstand what is commonly referred to as a “drop test.” The drop test requires that the mobile device remain operable after being dropped multiple times from a specified distance above a concrete surface. Dropping of the device in this manner subjects the various components within the device to large impact forces. Minimizing the lateral or in-plane movement of the movable components of autofocus actuator  100  using in-plane beams  126 A and  128 A therefore helps to improve the impact resistance. In-plane beams  126 B,  126 C,  128 B and  128 C are substantially similar to in-plane beams  126 A and  128 A therefore the description of in-plane beams  126 A and  128 A applies to these beams as well. 
     In one embodiment, in-plane beams  126 A and  128 A may be stationary elongated structures that are positioned within a gap formed between support beams  122 A,  124 A and the nearest deflection beam (e.g., deflection beams  118 A or  118 B). In-plane beams  126 A and  128 A may be positioned within the plane of support member  102  and have a width slightly smaller than the gap between the movable components. Since in-plane beams  126 A and  128 A minimize lateral movement of support beams  122 A,  124 A they also minimize lateral movement of movable drive portion  110 A. In-plane or lateral movement of movable drive portion  110 A can cause misalignment between the movable drive portion  110 A and stationary drive portion  108 A. Such misalignment may prevent proper operation of electrostatic actuator  106 A. 
     In-plane beams  126 A,  126 B,  126 C,  128 A,  128 B and  128 C may have a similar size and shape along their length as deflection beams  118 A,  118 B and  118 C; and support beams  122 A,  122 B,  122 C,  124 A,  124 B,  124 C except that they may include an extension portion  150  dimensioned to be received within a receiving portion  152  of the associated movable portions  114 A,  114 B,  114 C of support member  102 . The complimentary configuration of extension portion  150  and receiving portion  152  helps to further limit the in-plane movement of the moving actuator components (e.g., movable drive portions  110 A,  110 E and  110 C). 
       FIGS. 4A-4C  provide an exploded top plan view of the arrangement of each of the components discussed in reference to  FIG. 3 . In particular,  FIG. 4A  illustrates the stationary components,  FIG. 4B  illustrates each of the movable components and  FIG. 4C  illustrates the deflection beams. From this view, it can be understood more clearly, which components move when movable drive portion  110 A moves and which components remain stationary. In particular, as can be seen from  FIG. 4B , movable drive portion  110 A is connected to movable portion  114 A, support beams  122 A,  124 A and lens ring  140 . In addition, as can be seem from  FIG. 4C , deflection beams  118 A are connected to lens ring  140 . Thus, movement of movable drive portion  110 A also drives movement of each of these components in the same direction. Meanwhile, as can be seem from  FIG. 4A , in-plane beams  126 A and  128 A are independent from the moveable components and attached to stationary portion  112 . Thus, in-plane beams  126 A and  128 A remain stationary when movable drive portion  110 A moves. 
     As previously discussed, loading of a lens element within lens ring  140  applies an outward force to support ends  120 A,  120 B and  120 C causing deflection beams  118 A,  118 B and  118 C to buckle and assume an out-of-plane configuration. This out-of-plane configuration is illustrated in  FIG. 5 . In particular, as can be seen from  FIG. 5 , when lens element  103  is loaded into lens ring  140 , a force in a direction of arrows  304  is applied to support ends  120 A,  120 B and  120 C causing the associated deflection beams  118 A,  118 B and  118 C to buckle. The buckling of deflection beams  118 A,  118 B and  118 C draws the movable ends attached to lens ring  140  out-of-plane in a direction parallel to the direction in which lens element  103  is loaded into lens ring  140 . For example, in this embodiment, lens element  103  is loaded from above and pressed down into lens ring  140 . Deflection beams  118 A,  118 B and  118 C will therefore deflect and pull lens ring  140  to a position that is below the plane of support member  102 . This position can be considered the resting position of autofocus actuator  100  or position of the actuator in the non-actuated state. In other words, the position of autofocus actuator  100  when power is not being applied. 
     As can further be seen from this view, when deflection beam  118 A deflects, it also pulls movable drive portion  110 A down with respect to stationary drive portion  108 A. Thus, movable drive portion  110 A and stationary drive portion  108 A are displaced relative to each other along the optical axis in the non-actuated state. Deflection beams  118 B,  118 C and their associated drive portions  108 B,  110 E and  108 C,  110 C operate in a similar manner. 
     Since the in-plane beams, for example in-plane beams  126 A,  128 A and stationary portion  112  are independent from the movable components, these features remain in-plane with respect to support member  102 . 
     It is further noted that in some embodiments, the outward force, illustrated by arrow  304 , on lens ring  140  caused by loading of lens element  103  within lens ring, will cause other portions of lens ring  140  to be drawn inward. In particular, the portions of lens ring  140  attached to resilient arms  116 A,  116 B and  116 C may be pulled radially inward to allow the outward force in the direction of arrows  304 . Each of resilient arms  116 A,  116 B and  116 C may include spring members  130 A,  130 B and  130 C, respectively. Spring members  130 A,  130 B and  130 C help to maintain in-plane alignment of the electrostatic actuators  106 A,  106 B and  106 C in that they allow resilient arms  116 A,  116 B and  116 C, respectively, to expand in response to the radially inward force without pulling the movable drive portion away from the stationary drive portion. 
       FIG. 6  illustrates one implementation of the autofocus actuator described herein. Representatively, autofocus actuator  100  may be mounted within a miniature camera contained within a mobile device  600 . Here, the user is making a manual or touch selection on the touch screen viewfinder, which is previewing an object of interest  119 , at which the camera lens system  602 , having autofocus actuator  100  therein, is aimed. The selection may be in the form of a target graphic  604  such as a contour that may be drawn by the user on the touch screen  606 . Alternatively, the selection or target graphic  604  may be a fixed frame or a fixed solid area that moves with the user&#39;s finger across the touch screen  606 . The autofocus actuator  100  moves lens element  302  mounted therein so that the object of interest  119  is in focus. A flash element  610  may further be provided to illuminate the object of interest  119 . Once the user determines that the object of interest  119  is in focus, the user can capture the image by pressing virtual shutter button icon  608 . 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. For example, although the autofocus actuator is described as a MEMS device for use in a miniature camera, it is contemplated that the size and dimensions of the autofocus actuator can be scaled to accommodate any size camera or other device requiring movement of a lens or other component similar to that caused by autofocus actuator. Still further, although use of the actuator in a mobile device is disclosed, it is further contemplated that the actuator may be used to drive movement of a lens element within any kind of camera, e.g., still and/or video, integrated within any kind of electronic device or a camera that is not integrated into another device. Representative non-mobile devices may include a desktop computer, a television or the like. In addition, the actuator may be formed from a material other than a silicon wafer, or the different actuator components may be formed from different materials and assembled after formation to form the actuator. The description is thus to be regarded as illustrative instead of limiting.

Metadata:
Filing Date: 20121001
Publication Date: 20140429
Grant Date: 20140429
Priority Date: 20121001
Inventors: TOPLISS RICHARD J.
Assignee: APPLE INC
CPC Classifications: [{"code": "B81B2203/0136", "inventive": false, "first": false, "tree": "[]"}, {"code": "B81B2203/053", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B26/0841", "inventive": false, "first": false, "tree": "[]"}, {"code": "B81B2203/0172", "inventive": false, "first": false, "tree": "[]"}, {"code": "B81B3/0062", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B7/08", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B13/0075", "inventive": false, "first": false, "tree": "[]"}, {"code": "B81B2201/047", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B7/08", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B13/0075", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B26/0841", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 50384938