Patent Publication Number: US-9417425-B2

Title: Micro-electromechanical system (MEMS) carrier

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a micro-electromechanical system carrier, especially to a micro-electromechanical system carrier having a movable carrier element movable by an electromagnetic Lorentz force F. 
     2. Description of the Related Art 
     Nowadays, most of 3-C products, like cell-phone, note-book or tablet PC, are normally being equipped with a micro-digital camera lens. 
     For getting more product attractions to consumers, the camera lens with auto-focusing or optical-variable function has become an important requirement. However, all the camera lens with auto-focusing needs lens needs nearly 10 micro-meter space to move, it is quite difficult to install a step motor and gear system in a 3-C product, such as cell-phone, tablet PC as well as note-book. 
     In this regard, for minimizing the driving mechanism for lens focusing, traditional voice coil motor (VCM) structure may be a good solution. The voice coil motor can generate a magnetic force to co-act with an outside magnetic element to move a lens. 
     Although, some existing commercialized auto-focusing lens module with micro-electromechanical system being adopted, the VCM structure, however such kinds of commercial available auto-focusing lens modules are quite complex and heavy, bulky in size, therefore it still need to take further efforts to microminiaturize and simplify it. 
     SUMMARY OF THE INVENTION 
     In order to microminiaturize the auto-focusing lens module instead of traditional VCM structure, the present invention provides a micro-electromechanical system carrier which may include at least a frame, a movable carrier element located within the frame movable along a path, a conductive coil formed on the movable carrier element, and two return springs for connecting the movable carrier element inside the frame. By this structure, the return springs provide a return force to the carrier element. 
     In one embodiment, the conductive coil may be embedded in or formed on the surface of the movable carrier element. The two permanent magnets with opposite magnetic field may be mounted near the moving path of the movable carrier element to provide two opposite magnetic field perpendicular to the movable carrier element. 
     In physics, when a particle of charge q moves with a velocity v in an electric field E and a magnetic field B, then the particle of charge q will experience a Lorentz force F=q [E+(v×B)]. When a current is supplied to the conductive coil, the current shall flow in a counter-clockwise direction, and then the conductive coil will co-act with the permanent magnets and generate an electromagnetic Lorentz force. The electromagnetic Lorentz force shall drive the movable carrier element to move along a path in a direction against the force of the two return springs. When the current is stopped, the electromagnetic Lorentz force shall then be disappeared, and the two return springs provide a steady support and push the movable carrier element return to an original position. 
     In this embodiment, the distance and direction of the moving of the movable carrier element can be adjusted by changing the current flow in the conductive coil. By this way, the micro-electromechanical system carrier according to the present invention can use to carry a lens of a micro-camera module for focus-adjustment. The current flow may be conducted by a conductive layer of the frame and two return springs, and then form a circuit with the conductive coil. 
     In some other embodiment, a micro-electromechanical system carrier according to the present invention is capable of moving X- and Y-axis directions, which includes a first frame, a second frame, two first return springs, a movable carrier element, two second return springs, a first conductive coil, a second conductive coil. 
     In this embodiment, the second frame is formed within the first frame, and a first conductive coil is formed on the second frame. The two first return springs are connected between the first frame and the second frame and aligned with each other in the Y-axis direction. The movable carrier element is formed inside the second frame, and the second conductive coil is embedded in or formed on the surface of the movable carrier element. The two second return springs are connected between the movable carrier element and the second frame in X-axis direction, so as to provide a restoring force to the movable carrier element in X-axis direction. In this embodiment, the X-axis direction is perpendicular to the Y-axis direction, and the movable carrier element can move on a two dimensional plane by controlling the current flow in the first conductive coil and the second conductive coil. 
     As being described in the aforementioned embodiments, the first conductive coil may be embedded in or formed on either surface of the second frame. Similarly, the second conductive coil may also be embedded in or formed on the surface of the movable carrier element. In other embodiment, the first conductive coil is embedded in or formed on both surfaces of the second frame, and the second conductive coil is embedded in or formed on both surfaces of the movable carrier element. In another embodiment, the second conductive coil is formed around the movable carrier element. 
     In this embodiment, two magnetic fields are created in opposite directions by two pair of permanent magnets. When the current flows in the second conductive coil in clockwise direction, shall co-act with the magnetic field to generate an electromagnetic Lorentz force to move the movable carrier element in X-axis direction; and while the current being stopped, two second return springs shall provide sufficient support and move the movable carrier element back to its original position. 
     Due to the direction of the magnetic field being opposite to the magnetic field co-acting with the second conductive coil, while the current I has entered to flow in the first conductive coil in clockwise direction, the first conductive coil shall co-act with said magnetic field to generate an electromagnetic Lorentz force to move the second frame in Y-axis direction. As the movable carrier element is flexibly connected to the second frame, said electromagnetic Lorentz force would carry the second frame as well as the movable carrier element to move in Y-axis direction; and while the current being stopped, the two first return springs shall provide sufficient support and push the second frame to move back to the original position thereof in Y-axis direction. 
     By controlling the intensity and direction of the current in first conductive coil and second conductive coil, the movable carrier element may be precisely positioned in an X-Y plane. By this way, the micro-electromechanical system carrier according to the present invention can be incorporated in a two-axis autofocus miniature camera module. 
     The movable carrier element of this embodiment can be adopted to carry an image sensor, such as a CMOS image sensor, and moved in an X-Y plane so as to achieve an optical image stabilization function. By incorporating the micro-electromechanical system carrier of the present invention in an autofocus miniature camera module, the designer can improve the product with further minimized, noiseless, anti-vibration, and low power consumption. 
     The advantages of the present invention include a capability of driving the movable carrier element by controlling the intensity and direction of the current flow in the first conductive coil and second conductive coil, by this way to generate one or more electromagnetic Lorentz forces in one or more directions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention, are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a schematic elevated view of an embodiment of micro-electromechanical system carrier according to the present invention; 
         FIG. 2  is a schematic side view of the micro-electromechanical system carrier of  FIG. 1 ; 
         FIG. 3  is a schematic elevated view illustrating the operation of the micro-electromechanical system carrier of  FIG. 1 ; 
         FIG. 4  is a schematic elevated view of a second embodiment of the micro-electromechanical system carrier according to the present invention; 
         FIG. 5  is a schematic side view of the micro-electromechanical system carrier of  FIG. 4 ; 
         FIG. 6  is a schematic side view of a third embodiment of the micro-electromechanical system carrier according to the present invention; 
         FIG. 7  is a schematic elevated view of a fourth embodiment of micro-electromechanical system carrier according to the present invention; 
         FIG. 8  is a schematic elevated view illustrating the operation of the micro-electromechanical system carrier of  FIG. 7 ; and 
         FIG. 9  is a schematic elevated view illustrating the micro-electromechanical system carrier incorporated in a miniature camera module. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 to 3 , an embodiment of a micro-electromechanical system (MEMS) carrier according to the present invention is formed on a silicon substrate  100  by a micro-machining and bulk micro-machining process. The micro-electromechanical system carrier provides a frame  110 , a movable carrier element  120  formed within the frame  110  and movable along a path within the frame  110 , a conductive coil  200  formed on the movable carrier element  120 , and the two return springs  130  being formed for connecting the movable carrier element  120  inside the frame  110 . By this structure, the return springs  130  can provide a return force to the carrier element  120 . 
     In one embodiment, the silicon substrate  100  may adopt a thicker Silicon On Insulator (SOI) substrate with low internal stress. The frame  110 , the movable carrier element  120 , the conductive coil  200  and the two return springs  130  being formed by a typical surface micro-machining and bulk micro-machining process on the silicon substrate  100 . For instance, the aforementioned Surface Micro-machining may include a thin film deposition, micro-imaging technique, just like the process used to apply in semiconductor industry, so as to form a mechanical structure of thin film stacking. 
     After the Surface Micro-machining and Bulk Micro-machining process being finished, the silicon substrate  100  shall be removed from the micro-electromechanical system. By this step, the micro-structure of the micro-electromechanical system is then become a 3-dimensional structure and get more aspect ratio to form the frame  110 , the movable carrier element  120 , the two return springs  130  and the conductive coil  200 . 
     In one embodiment, the conductive coil  200  may be embedded in or formed on the surface of the movable carrier element  120  as best shown in  FIGS. 4 and 5 . Two permanent magnets  500  with opposite magnetic field may be mounted near the moving path of the movable carrier element  120  that provide two opposite magnetic field (indicated as ⊙ and ⊕) perpendicular to the movable carrier element  120 . 
     As shown in  FIG. 3 , when a current I has been supplied to the conductive coil  200 , the current I shall flow in a counter-clockwise direction, and then co-act with the permanent magnets  500  that will generate an electromagnetic Lorentz force F. The electromagnetic Lorentz force F shall drive the movable carrier element  120  to move along a path in a direction against the force of the two return springs  130 . When the current I is distinguished, the electromagnetic Lorentz force F shall then be disappeared, and the two return springs  130  provide a steady support and push the movable carrier element  120  to return to an original position. 
     In this embodiment, the distance and direction of the moving of the movable carrier element  120  can be adjusted by changing the flow of the current I in the conductive coil  200 . By this way, the micro-electromechanical system (MEMS) carrier according to the present invention can use to carry a lens of a micro-camera module for focus-adjustment. The current flow may conduct by a conductive layer of the frame  110  and two return springs  130 , and then formed a circuit with the conductive coil  200 . 
     Referring to  FIG. 3 , the conductive coil  200  may be embedded in or formed on either surface of the movable carrier element  120 . Referring to  FIGS. 4 and 5 , the conductive coil  200  may be embedded in or formed on both surfaces of the movable carrier element  120 , and provides a connecting portion  210  for providing an electrical connection therebetween. When the current I is supplied to the conductive coil  200 , the conductive coil will co-act with the permanent magnets  500  to generate an electromagnetic Lorentz force F thereby driving the movable carrier element  120  to move in a distance against the force of the two return springs  130 . 
     Referring to  FIG. 6 , the conductive coil  200  can also be formed around the movable carrier element  120 , and the permanent magnets  500  are disposed aligned with the moving path of the movable carrier element  120 . When the current I is supplied to the conductive coil  200 , will co-acting with the permanent magnets  500  to generate an electromagnetic Lorentz force F thereby driving the movable carrier element  120  to move in a distance against the force of the two return springs  130 , and the two return springs  130  provide a steady support and push the movable carrier element  120  to return to an original position after the current I being stopped. 
     Referring to  FIG. 7 , another micro-electromechanical system (MEMS) carrier according to the present embodiment is capable of moving in X- and Y-axis directions, including a first frame  310 , a second frame  320 , two first return springs  330 , a movable carrier element  340 , two second return springs  350 , a first conductive coil  410 , and a second conductive coil  420 . 
     In this embodiment, the second frame  320  is formed within the first frame  310 , and a first conductive coil  410  is formed on the second frame  320 . The two first return springs  330  are connected between the first frame  310  and the second frame  320  being aligned with each other in the Y-axis direction. The movable carrier element  340  is formed inside the second frame  320 , and the second conductive coil  420  is embedded in or formed on the surface of the movable carrier element  340 . The two second return springs  350  are connected between the movable carrier element  340  and the second frame  320  in X-axis direction, so as to provide a restoring force to the movable carrier element  340  in X-axis direction. In this embodiment, the X-axis direction is perpendicular to the Y-axis direction, and the movable carrier element  340  can move on a two dimensional plane by controlling the current I flow in the first conductive coil  410  and the second conductive coil  420 . 
     As being described in the aforementioned embodiments, the first conductive coil  410  may be embedded in or formed on either surface of the second frame  320 . Similarly, the second conductive coil  420  may also be embedded in or formed on the surface of the movable carrier element  340 . In other embodiment, the first conductive coil  410  is embedded in or formed on both surfaces of the second frame  320 , and the second conductive coil  420  is embedded in or formed on both surfaces of the movable carrier element  340 . In another embodiment, the second conductive coil  420  is formed around the movable carrier element  340 . 
     As shown in  FIG. 8 , two magnetic fields being created in opposite directions by two pair of permanent magnets  510 . By this arrangement, when the current I flows in the second conductive coil  420  in clockwise direction, the conductive coil shall co-act with the magnetic field to generate an electromagnetic Lorentz force F to move the movable carrier element  340  in X-axis direction; and while the current I being stopped, two second return springs  350  shall provide sufficient support and move the movable carrier element  340  back to its original position. 
     Due to the direction of the magnetic field being opposite to the magnetic field co-acting with the second conductive coil  420  (both magnetic field directions being indicated as ⊙ and ⊕ as shown in  FIG. 8 ), while the current I has flowed in the first conductive coil  410  in clockwise direction, the first conductive coil  410  shall co-act with said magnetic field to generate an electromagnetic Lorentz force F to move the second frame  320  in Y-axis direction. As the movable carrier element  340  being flexibly connected to the second frame  320 , said electromagnetic Lorentz force F would carry the second frame  320  as well as the movable carrier element  340  to move in Y-axis direction; and while the current I being stopped, the two first return springs  330  shall provide sufficient support and push the second frame  320  to move back to the original position thereof in Y-axis direction. 
     By controlling the intensity and direction of the current I in first conductive coil  410  and second conductive coil  420 , the movable carrier element  340  may be precisely positioned in an X-Y plane. By this way, the micro-electromechanical system carrier according to the present invention can be incorporated into a two-axis autofocus miniature camera module. 
     Referring to  FIG. 9 , the movable carrier element  340  can be adopted to carry an image sensor  600 , such as a CMOS image sensor, moving in an X-Y plane so as to achieve an optical image stabilization function. By incorporating the micro-electromechanical system carrier of the present invention in an autofocus miniature camera module, the designer can improve the product with further minimize, noiseless, anti-vibration, and low power consumption. 
     The advantages of the present invention include a capability of driving the movable carrier element  340  by controlling the intensity and direction of the current I flow in the first conductive coil  410  and second conductive coil  420 , by this way to generate one or more electromagnetic Lorentz forces F in one or more directions. 
     Existing micro-electromechanical system technology being achieved an extremely high precision manufacturing less than one micron, it is far beyond traditional machining process can provide. Micro-electromechanical system element has the advantage of microminiaturization, lightweight, high-precision and getting fast dynamic response. Compare to the like carrier structure such as Voice Coil Motor (VCM), the micro-electromechanical system carrier of the present invention can achieve more better microminiaturization, good system integration, high optical axis precision and more suitable for mass production for miniature camera module manufacturing process. 
     While particular embodiments of the invention have been described, those skilled in the art will recognize that many modifications are possible that will achieve the same goals by substantially the same system, device or method, and where those systems, devices or methods still fall within the true spirit and scope of the invention disclosed.