Patent Publication Number: US-11378771-B2

Title: Optical element driving mechanism

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of application Ser. No. 15/935,512, filed Mar. 26, 2018, which claims the benefit of U.S. Provisional Application No. 62/478,193, filed Mar. 29, 2017, and claims priority of China Patent Application No. 201810185975.4, filed Mar. 7, 2018, the entirety of which are incorporated by reference herein. 
    
    
     BACKGROUND 
     Technical Field 
     The disclosure relates to an optical element driving mechanism, and in particular to an optical element driving mechanism in which the elastic element and the sensing assembly at least partially overlap when observed in the optical axis direction. 
     Description of the Related Art 
     The volume requirements on electronic products are becoming increasingly stricter. If the overall volume needs to be reduced, the interior space has to be utilized more effectively. In addition, when electronic products collide with one another, inner electronic elements can often become damaged due to the collision with other components. Therefore, the performance of these electronic products suffers. 
     BRIEF SUMMARY 
     For solving the aforementioned problems, some embodiments of the disclosure provide a driving mechanism configured to drive an optical element. The driving mechanism includes a holding unit, a base unit, an elastic element, a driving assembly, and a sensing assembly. The holding unit is configured to hold the optical element. The base unit is located below the holding unit. The elastic element connects the holding unit to the base unit. The driving assembly is configured to drive the optical element to move relative to the base unit. The sensing assembly is disposed between the holding unit and the base unit, and the sensing assembly is configured to detect the position of the holding unit relative to the base unit. When observed in an optical axis direction of the optical element, the elastic element and the sensing assembly at least partially overlap. 
     In an embodiment, the sensing assembly further includes a magnetic field sensing element disposed on the base unit, and a sensing magnet disposed on the holding unit. In an embodiment, the sensing magnet is a multipolar magnet. In an embodiment, the driving mechanism further includes a housing, which is a magnetic permeable material, having an opening and an extending portion. The holding unit is disposed in the opening, and the extending portion extends from an inner edge of the opening towards the base unit. In an embodiment, the housing has a rectangular structure, and the extending portion and the sensing assembly are located at different corners of the rectangular structure. In an embodiment, the housing further includes two extending portions, which are respectively located at two opposite corners of the rectangular structure. 
     Some embodiments of the disclosure provide a driving mechanism configured to drive an optical element. The driving mechanism includes a frame, a holding unit, a driving assembly, and a circuit unit. The frame includes a stopping portion protruding from an inner surface of the frame, wherein there is a first distance between the stopping portion and an optical axis of the optical element. The holding unit is movably disposed in the frame, and is configured to hold the optical element. The driving assembly is configured to drive the optical element to move relative to the frame. The circuit unit is disposed on the frame, wherein there is a second distance between the circuit unit and the optical axis of the optical element, and the first distance is shorter than the second distance. 
     In an embodiment, the circuit unit includes a circuit board and an integrated circuit element, the integrated circuit element is disposed on the circuit board, wherein the integrated circuit element abuts an abutting surface of the stopping portion. In an embodiment, the abutting surface is perpendicular to the optical axis direction. In an embodiment, the stopping portion has a C-shaped structure. In an embodiment, the circuit unit includes a circuit board and an integrated circuit element, and the integrated circuit element is disposed on the circuit board, wherein the frame further includes two limiting portions. The circuit board is disposed between the limiting portions for limiting the circuit board at a given position. In an embodiment, the circuit unit includes the circuit board and the integrated circuit element, and the integrated circuit element is disposed on the circuit board, wherein the stopping portion and the limiting portions form a recess, and the circuit board is disposed in the recess. In an embodiment, the driving mechanism further includes a wire, wherein the holding unit includes a wire pillar. The wire is electrically connected to the driving assembly, and winds around the wire pillar, wherein the wire pillar and the driving assembly respectively correspond to different sides of the holding unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a schematic perspective view illustrating a driving mechanism in accordance with an embodiment of the present disclosure. 
         FIG. 2  is an exploded view illustrating the driving mechanism in  FIG. 1 . 
         FIG. 3A  is a cross-sectional view illustrating the driving mechanism along line A-A′ in  FIG. 1 . 
         FIG. 3B  is a cross-sectional view illustrating the driving mechanism along line B-B′ in  FIG. 1 . 
         FIG. 4  is a top view illustrating the driving mechanism in accordance with an embodiment of the present disclosure. 
         FIG. 5  is a schematic view illustrating a magnetic field sensing element and a sensing magnet in accordance with an embodiment of the present disclosure after assembly. 
         FIG. 6A  is a partial top view illustrating relative positions between a driving coil, an upper leaf spring, a lower leaf spring, a magnetic field sensing element, and a sensing magnet in accordance with an embodiment of the present disclosure after assembly. 
         FIG. 6B  is a side view illustrating relative positions between the driving coil, the upper leaf spring, the lower leaf spring, the magnetic field sensing element, and the sensing magnet shown in  FIG. 6A  after assembly. 
         FIG. 7  is a perspective view illustrating relative positions between the housing, the base unit, and the sensing magnet in accordance with an embodiment of the present disclosure. 
         FIG. 8A  is a side view illustrating the frame and the circuit unit in accordance with another embodiment of the present disclosure. 
         FIG. 8B  is a top view illustrating the frame and the circuit unit shown in  FIG. 8A . 
         FIG. 8C  is a partial cross-sectional view illustrating the frame, the circuit unit shown in  FIG. 8B  and the housing after assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The driving mechanisms of some embodiments of the present disclosure are described in the following description. However, it should be appreciated that the following detailed description of some embodiments of the disclosure provides various concepts of the present disclosure which may be performed in specific backgrounds that can vary widely. The specific embodiments disclosed are provided merely to clearly describe the usage of the present disclosure by some specific methods without limiting the scope of the present disclosure. 
     Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It should be appreciated that, in each case, the term, which is defined in a commonly used dictionary, should be interpreted as having a meaning that conforms to the relative skills of the present disclosure and the background or the context of the present disclosure, and should not be interpreted in an idealized or overly formal manner unless so defined in the present disclosure. 
     Referring to  FIGS. 1 to 3B , wherein  FIG. 1  is a schematic perspective view illustrating a driving mechanism  1  in accordance with an embodiment of the present disclosure,  FIG. 2  is an exploded view illustrating the driving mechanism  1  in  FIG. 1 ,  FIG. 3A  is a cross-sectional view illustrating the driving mechanism  1  along line A-A′ in  FIG. 1 , and  FIG. 3B  is a cross-sectional view illustrating the driving mechanism  1  along line B-B′ in  FIG. 1 . It should be noted that, in this embodiment, the driving mechanism  1  may be, for example, a voice coil motor (VCM), which may be disposed in the electronic devices with camera function for driving an optical lens, and can perform an auto-focusing (AF) function. 
     It is shown in  FIG. 2  that the driving mechanism  1  has a substantial rectangular structure, which mainly includes a housing  10 , a base unit  20 , a holding unit  30 , a plurality of driving coils  40 , a frame  50 , a plurality of magnetic elements  60 , an upper leaf spring  70 , a lower leaf spring  72 , a circuit board  80 , and at least one sensing magnet  90 . It should be noted that the term “elastic element” may include the upper leaf spring  70  and/or the lower leaf spring  72  hereinafter. 
     The housing  10  has a hollow structure, which includes a top wall  10 A, four sidewalls  10 B, and an opening  12 . The center of the opening  12  corresponds to an optical axis O of an optical element OE (See  FIGS. 3A and 3B ). An opening  22  is formed on the base unit  20 , and the opening  22  corresponds to an image-sensing element (not shown) disposed outside the optical element driving mechanism  1 . The housing  10  is connected to the base unit  20 . Therefore, the optical element OE (such as an optical lens) disposed in the driving mechanism  1  can perform a focusing function with the image-sensing element in the direction of the optical axis O. It should be noted that the term “the direction of the optical axis O”, which may also be referred to as “the optical axis O direction”, means the direction that is along the optical axis O or parallel to the optical axis O in the following description. 
     The base unit  20  includes a body  201  and a connecting member  202 . For example, the body  201  is a plastic material, and the connecting member  202  is a metallic material. In this embodiment, the connecting member  202  is electrically connected to a driving unit (not shown) disposed outside the driving mechanism  1  through the circuit board  80  (See  FIG. 3B ), and the connecting member  202  is configured to perform an auto-focusing (AF) function. In addition, the body  201 , which is a plastic material, covers an outside of the connecting member  202  by insert molding. 
     The holding unit  30  holds the optical element OE. The holding unit  30  has a hollow structure, and a through hole  32  is formed therein, wherein the optical element OE (See  FIGS. 3A and 3B ) is secured in the through hole  32 . The frame  50  has an opening  52 , and the frame  50  includes a recess  50 A, wherein the circuit board  80  may be fixed in the recess  50 A. In this embodiment, the circuit board  80  is electrically connected to the driving unit (not shown) disposed outside the driving mechanism  1 . The circuit board  80  is electrically connected to the driving coils  40  through the connecting member  202 , and the circuit board  80  transmits the electrical signals sent from the driving unit to the driving coils  40  to perform an auto-focusing (AF) function. 
       FIG. 3A  is a cross-sectional view illustrating the driving mechanism  1  along line A-A′ in  FIG. 1 . As shown in  FIGS. 2 and 3A , the holding unit  30  is movably connected to the housing  10  and the base unit  20 . To be more specific, the holding unit  30  may be connected to the frame  50  through the upper leaf spring  70 , the holding unit  30  may also be connected to the base unit  20  through the lower leaf spring  72 , and the upper leaf spring  70  and the lower leaf spring  72  are metallic materials. Therefore, the holding unit  30  is movably suspended between the frame  50  and the base unit  20 . 
     Two magnetic elements  60  and two corresponding driving coils  40 , which are disposed outside the holding unit  30 , may constitute a driving assembly EM. When a current is applied to the driving coils  40  through the connecting member  202  and the circuit board  80  (See  FIG. 3B ), an electromagnetic driving force may be generated by the driving coils  40  and the magnetic elements  60  to drive the holding unit  30  and the optical element OE to move along Z-axis direction (the optical axis O direction) relative to the base unit  20 . Therefore, the auto-focusing (AF) function is performed. 
       FIG. 3B  is a cross-sectional view illustrating the driving mechanism  1  along line B-B′ in  FIG. 1 . As shown in  FIG. 3B , the circuit board  80  may transmit the electrical signal to the two driving coils  40  (See  FIG. 3A ), which is disposed outside the holding unit  30 , through the connecting member  202 , the lower leaf spring  72 , and a wire  31 . Therefore, the movement of the holding unit  30  in Z-axis direction is controlled. 
     In addition, a magnetic field sensing element  82  may also be disposed on and electrically connected to the circuit board  80 . The magnetic field sensing element  82  is, for example, a Hall effect sensor, a magnetoresistive (MR) sensor, such as a giant magnetoresistive (GMR) sensor or a tunnel magnetoresistive (TMR) sensor, or a fluxgate. The magnetic field sensing element  82  and the sensing magnet  90  constitute a sensing assembly. By detecting the sensing magnet  90 , which is disposed on the holding unit  30 , the displacement of the holding unit  30  in the Z-axis direction (the optical axis O direction) relative to the base unit  20  may be obtained. The circuit board  80  and the driving assembly EM are disposed on different sides of the driving mechanism  1 . That way, electromagnetic interference may be avoided, and the interior space of the driving mechanism  1  may be fully utilized. 
     Referring to  FIG. 4 ,  FIG. 4  is a top view illustrating the driving mechanism  1  in accordance with an embodiment of the present disclosure. For clarity of illustrating inner configuration of the driving mechanism  1 , the housing  10 , the frame  50 , and the upper leaf spring  70  are not shown in  FIG. 4 . As shown in  FIG. 4 , the driving assembly EM (including the magnetic elements  60  and the driving coils  40 ) is disposed on two opposite sides of the holding unit  30  (such as the left and right sides of the holding unit  30  in  FIG. 4 ), and the driving assembly EM is not disposed on the other sides of the holding unit  30  (such as the upper and lower sides of the holding unit  30  in  FIG. 4 ). Therefore, the size of the driving mechanism  1  may be reduced on the sides where no driving assembly EM is disposed, and the miniaturization effect is achieved. 
     In addition, the holding unit  30  includes wire pillars  311  for winding the wires  31 , which are electrically connected to the driving coils  40  (the driving assembly EM) around the wire pillars  311 . It should be noted that the wire pillars  311  and the driving assembly EM are disposed on different sides of the holding unit  30 . For example, the wire pillars  311  are disposed on the upper and lower sides of the holding unit  30  in  FIG. 4  to evade the driving assembly EM. That way, the required space in the driving mechanism  1  may be further saved. 
     Still referring to  FIG. 4 , in this embodiment, not only the magnetic field sensing element  82 , but the integrated circuit (IC) element  84  and a capacitor  86  are also disposed on the circuit board  80 . The circuit board  80 , the integrated circuit element  84 , and the capacitor  86  may constitute a circuit unit CU, which is configured to perform an auto-focusing function. The sensing magnet  90  is disposed in a corresponding cavity  910  on the holding unit  30 , and the sensing magnet  90  may be fixed in the cavity  910  through an adhesive. It should be noted that besides the sensing magnet  90  corresponding to the magnetic field sensing element  82 , another sensing magnet  90 ′ is also disposed on the opposite place to the sensing magnet  90  on the holding unit  30 . The sensing magnet  90 ′ is disposed in a corresponding cavity  910 ′ so that the driving mechanism  1  may reach a balance on weight. 
     Referring to  FIG. 5 ,  FIG. 5  is a schematic view illustrating the magnetic field sensing element  82  and the sensing magnet  90  in accordance with an embodiment of the present disclosure after assembly. In this embodiment, there are no other elements disposed between the magnetic field sensing element  82  and the sensing magnet  90 . Therefore, the magnetic field sensing element  82  may detect the displacement of the sensing magnet  90  located on the holding unit  30  in Z-axis direction (the optical axis O direction) without any interference. The detection accuracy is enhanced. The sensing magnet  90  is a multipolar magnet, which includes at least two magnetic domains  901  and  903 . The magnetic domains  901  and  903  respectively have an N-pole and an S-pole. Moreover, the sensing magnet  90  further includes a magnetic neutral zone  902 , which is located between the magnetic domains  901  and  903 . 
     As shown in  FIG. 5 , the S-pole of the magnetic domain  901  faces the magnetic field sensing element  82 , and the N-pole faces the through hole  32  (See  FIG. 4 ) of the holding unit  30 . The N-pole of the other magnetic domain  903  faces the magnetic field sensing element  82 , and the S-pole faces the through hole  32  of the holding unit  30 . It should be noted that, in some other embodiments, the polar directions of the magnetic domains  901  and  903  may be opposite to the aforementioned polar directions. The lines of magnetic field may be closer by designing the sensing magnet  90  as a multipolar magnet with multiple magnetic domains. In a case without increasing the volume of the sensing magnet  90 , the detection accuracy may be further enhanced. That way, the size of the sensing magnet  90  may also be reduced so that the energy consumption of the driving mechanism  1  is also reduced, and the miniaturization effect can be achieved. 
     Referring to  FIGS. 6A and 6B ,  FIG. 6A  is a partial top view illustrating relative positions between the driving coil  40 , the upper leaf spring  70 , the lower leaf spring  72 , the magnetic field sensing element  82 , and the sensing magnet  90  in accordance with an embodiment of the present disclosure after assembly, and  FIG. 6B  is a partial side view illustrating relative positions between the driving coil  40 , the upper leaf spring  70 , the lower leaf spring  72 , the magnetic field sensing element  82 , and the sensing magnet  90  shown in  FIG. 6A  after assembly. As shown in  FIGS. 6A and 6B , when observed in the optical axis O direction (Z-axis direction), the magnetic field sensing element  82  and the sensing magnet  90  (the sensing assembly) are disposed between the upper leaf spring  70  and the lower leaf spring  72 , and the sensing assembly, the upper leaf spring  70  and the lower leaf spring  72  (the elastic element) at least partially overlap. In this embodiment, the magnetic field sensing element  82  and the sensing magnet  90  do not exceed the edges of the upper leaf spring  70  and the lower leaf spring  72  in a horizontal direction (XY-plane). Therefore, the required space of the driving mechanism  1  in the horizontal direction (XY-plane) may be further saved so that the miniaturization of the driving mechanism is achieved. 
     Referring to  FIG. 7 ,  FIG. 7  is a perspective view illustrating relative positions between the housing  10 , the base unit  20 , and the sensing magnet  90  in accordance with an embodiment of the present disclosure after assembly. In this embodiment, the housing  10  is a magnetic permeable material with a rectangular structure, wherein the holding unit  30  is disposed in the opening  12  of the housing  10 , and the housing  10  includes two extending portions  11  extending from the inner edge of the opening  12  towards the base unit  20  (−Z-axis direction). In addition, the two extending portions  11  are located at two opposite corners of the rectangular structure, and the extending portions  11  are located at the corners of the rectangular structure, which is different from that of the rectangular structure where the sensing magnet  90  and the corresponding magnetic field sensing element  82  (i.e. the sensing assembly) (See  FIGS. 6A and 6B ) are located. That is, the extending portions  11  and the sensing magnet  90  are disposed at different corners of the housing  10 . The magnetic permeable housing  10  and its extending portion  11  may be avoided affecting the sensing magnet  90 . Therefore, the operation of the driving mechanism is avoided being affected, and the driving mechanism  1  may reach a balance on weight. 
     Referring to  FIGS. 8A-8C ,  FIG. 8A  is a side view illustrating the frame  50  and the circuit unit CU in accordance with another embodiment of the present disclosure,  FIG. 8B  is a top view illustrating the frame  50  and the circuit unit CU shown in  FIG. 8A , and  FIG. 8C  is a schematic cross-sectional view illustrating the frame  50 , the circuit unit CU shown in  FIG. 8B  and the housing  10  after assembly. In this embodiment, the circuit unit CU is disposed on the frame  50 . The frame  50  includes a stopping portion  502  and two limiting portions  504 . The stopping portion  502  protrudes from an inner surface  50 B (See  FIG. 8B ) of the frame  50 , and is configured to protect the electronic elements of the circuit unit CU (i.e. the electronic elements disposed on the circuit board  80 ). The circuit board  80  is disposed between the two limiting portions  504 , which is configured to limit the circuit board  80  at a given position. That is, the position of the circuit unit CU on the frame  50  is fixed. 
     In addition, the stopping portion  502  has a C-shaped structure (See  FIG. 8A ) around the integrated circuit element  84  located on the circuit board  80 . The stopping portion  502  has a first width W 1  (See  FIG. 8C ) in Y-axis direction, the integrated circuit element  84  has a second width W 2  in Y-axis direction, and the first width W 1  is greater than the second width W 2 . In other words, there is a first distance D 1  between the stopping portion  502  and the optical axis O of the optical element OE, and there is a second distance D 2  between the integrated circuit element  84  of the circuit unit CU and the optical axis O, therein the first distance D 1  is shorter than the second distance D 2 . That way, the stopping portion  502  may protect the integrated circuit element  84  and other electronic elements (such as the magnetic field sensing element  82 ) disposed on the circuit board  80 . Therefore, the electronic elements may not be damaged due to direct collision with other components in the optical element driving mechanism  1 . 
     The stopping portion  502 , the limiting portions  504 , and the housing  10  (See  FIG. 8C ) constitute a recess  50 A. The recess  50 A has a width WR between the stopping portion  502  and the inner surface of the housing  10 , wherein the width WR is substantially in a range of about 0.05 mm to about 0.2 mm, such as 0.1 mm. The circuit board  80  is disposed in the recess  50 A, and the circuit board  80  is limited in a given position in a horizontal direction (XY-plane) so that it is less possible for the circuit board  80  to be detached. In addition, the stopping portion  502  and the limiting portions  504  of the frame  50  may also serve as positioning targets for mounting the circuit board  80  on the frame  50 . Therefore, during assembly, the accuracy of positioning the circuit board  80  is enhanced, and the assembly difficulty is reduced. 
     Still referring to  FIG. 8C , the stopping portion  502  has an abutting surface  502 A, which is perpendicular to the optical axis O direction (Z-axis direction). The integrated circuit element  84  disposed on the circuit board  80  abuts the abutting surface  502 A of the stopping portion  502 , and the circuit board  80  is prevented from contacting the frame  50  in a vertical direction (Z-axis direction), leaving a gap between the circuit board  80  and the frame  50 . When the driving mechanism  1  is collided in a vertical direction, the circuit board  80  may be avoided from becoming damaged due to direct collision with the frame  50 . Furthermore, a chamfer  502 B may be disposed on an inner side of the stopping portion  502  so that the circuit unit CU may be mounted in the recess  50 A more easily. 
     As set forth above, the embodiments of the present disclosure provide an optical element driving mechanism in which an elastic element and a sensing assembly at least partially overlap when observed in an optical axis direction. That way, the interior space may be utilized more effectively to reduce the volume of the driving mechanism. In addition, the embodiments of the present disclosure also provide an optical element driving mechanism with a frame, which may protect a circuit board. Therefore, the circuit board may be less damaged due to collision with other components. 
     While the embodiments and the advantages of the present disclosure have been described above, it should be understood that those skilled in the art may make various changes, substitutions, and alterations to the present disclosure without departing from the spirit and scope of the present disclosure. In addition, the scope of the present disclosure is not limited to the processes, machines, manufacture, composition, devices, methods and steps in the specific embodiments described in the specification. Those skilled in the art may understand existing or developing processes, machines, manufacture, compositions, devices, methods and steps from some embodiments of the present disclosure. As long as those may perform substantially the same function in the aforementioned embodiments and obtain substantially the same result, they may be used in accordance with some embodiments of the present disclosure. Therefore, the scope of the present disclosure includes the aforementioned processes, machines, manufacture, composition, devices, methods, and steps. Furthermore, each of the appended claims constructs an individual embodiment, and the scope of the present disclosure also includes every combination of the appended claims and embodiments.