Patent Publication Number: US-2022214155-A1

Title: Lens positioning device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Chinese application no. 202110007299.3, filed on Jan. 5, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a positioning device, and more particularly to a lens positioning device. 
     Description of Related Art 
     There is a lens device that uses a shape memory alloy to drive the lens to move, so as to achieve focus (AF) or hand vibration compensation (OIS). The principle of such lens device utilizes the thermal shrinkage and cold expansion characteristics of the shape memory alloy. After current passes through the alloy wire, the alloy wire is tightened due to the rise in temperature to pull the lens carrier. Moreover, when the alloy wire shrinks due to heat, its cross section and length change, and the resistance also changes accordingly. Therefore, the change in length can be inferred through the change in resistance to determine whether the lens carrier has been moved to the desired position. 
     However, because the resistance change and the length change of the shape memory alloy wire are not completely linearly related, especially when the length change increases or the operating temperature rises, there will be errors when the length of the alloy wire is inferred through the change of resistance, leading to inaccurate displacement accuracy. In addition, in detection of the resistance, if there are other losses, such as the resistance in the driving chip or the welding resistance between the actuator and the substrate, the overall resistance will vary, which will also cause errors in the calculation of the length of alloy wire. 
     SUMMARY 
     The disclosure provides a lens positioning device that can quickly and accurately position the lens. 
     A lens positioning device of the disclosure includes a lens carrier, a housing, three pairs of memory alloy wires and three displacement detecting units. The lens carrier is provided with a lens. The housing has an accommodating space for accommodating the lens carrier, and the lens protrudes from the opening of the housing. The three pairs of memory alloy wires are used to control the displacement of the lens carrier in three directions, respectively. The three directions are orthogonal to one another. Each of the displacement detecting units includes a magnetic element and a magnetic field sensing element. The magnetic element is arranged on the lens carrier. The magnetic field sensing element is arranged on the housing and corresponding to the magnetic element to sense change of the magnetic field of the magnetic element along each of the three directions when the lens carrier moves. One magnetic element of any one of the three displacement detecting units is arranged at a position that can induce the corresponding magnetic field sensing element and does not interfere with the magnetic field sensing elements of the other two of the three displacement detecting units. 
     In an embodiment of the disclosure, the lens positioning device further includes a control unit. The control unit is electrically connected to the three pairs of memory alloy wires and the three displacement detecting units. The control unit controls the displacement of the lens carrier in three directions by controlling the current of the three pairs of memory alloy wires, and the control unit is not provided with the control element used to calculate the resistance of three pairs of memory alloy wires. 
     In an embodiment of the disclosure, the three directions include a first direction, a second direction, and a third direction. The three pairs of memory alloy wires include a first pair of memory alloy wires, a second pair of memory alloy wires, and a third pair of memory alloy wires. The first pair of memory alloy wires, the second pair of memory alloy wires, and the third pair of memory alloy wires are used to control the displacement of the lens carrier in the first direction, the second direction, and the third direction, respectively. 
     In an embodiment of the disclosure, the lens carrier includes a first movable structure and a second movable structure. The housing includes a first fixing end and a second fixing end. The first movable structure and the second movable structure are arranged along a first diagonal direction of the lens carrier on the plane where the first direction and the second direction are located. The first fixing end and the second fixing end are arranged along a second diagonal direction of the lens carrier on the plane where the first direction and the second direction are located. 
     In an embodiment of the disclosure, two memory alloy wires of the first pair of memory alloy wires are respectively arranged on two opposite outer sides of the lens carrier in the second direction. Both ends of one memory alloy wire of the first pair of memory alloy wires are respectively connected to the first fixing end and the second movable structure, and both ends of the other memory alloy wire of the first pair of memory alloy wires are respectively connected to the second fixing end and the first movable structure to control the displacement of the both ends of the lens carrier in the first direction. 
     In an embodiment of the disclosure, two memory alloy wires of the second pair of memory alloy wires are respectively arranged on two opposite outer sides of the lens carrier in the first direction. Both ends of one memory alloy wire of the second pair of memory alloy wires are respectively connected to the first fixing end and the first movable structure, and both ends of the other memory alloy wire of the second pair of memory alloy wires are respectively connected to the second fixing end and the second movable structure to control the displacement of the both ends of the lens carrier in the second direction. 
     In an embodiment of the disclosure, the lens carrier includes a first hook structure and a second hook structure, and the first hook structure and the second hook structure are disposed on the lateral surface of the lens carrier along a third direction. The housing further includes a first pair of fixing ends and a second pair of fixing ends. The first pair of fixing ends and the second pair of fixing ends are respectively disposed on both sides of the housing in the third direction. Both ends of one memory alloy wire of the third pair of memory alloy wires are respectively connected with the ends of the first pair of fixing ends. One memory alloy wire of the third pair of memory alloy wires controls the displacement of one end of the lens carrier in the third direction in the manner of returning back to one side of the third direction after winding the first hook structure. Both ends of the other memory alloy wire of the third pair of memory alloy wires are respectively connected to the ends of the second pair of fixing ends. The other memory alloy wire of the third pair of memory alloy wires controls the displacement of the other end of the lens carrier in the third direction in the manner of returning back to the other side of the third direction after winding the second hook structure. 
     Based on the above, the lens positioning device of the disclosure can calculate the displacement of the lens carrier in three different directions through the arrangement of the magnetic elements and magnetic field sensing elements of the three displacement detecting units. In addition, since the data obtained by the above detection method will not be interfered by the deformation of the memory alloy wire or external resistance or temperature or other factors, the obtained values will be more accurate. Moreover, the method is adaptable for situations that require a greater amount of displacement, and has a faster response speed and can perform detection quickly. Furthermore, there is no need for the lens positioning device to be provided with the control element for calculating the resistance of the three pairs of memory alloy wires, the product cost can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a bottom view of a lens positioning device according to an embodiment of the disclosure. 
         FIG. 2  is a schematic view of the lens positioning device of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a bottom view of a lens positioning device according to an embodiment of the disclosure.  FIG. 2  is a schematic view of the lens positioning device of  FIG. 1 . Please refer to  FIG. 1  and  FIG. 2 . A lens LE positioning device  100  of the embodiment includes a lens carrier  110 , a housing  120 , three pairs of memory alloy wires  130 , three displacement detecting units  140   x,    140   y  and  140   z,  and a control unit (not shown). The lens carrier  110  is provided with a lens LE. The housing  120  has an accommodating space CA for accommodating the lens carrier  110 , and the lens LE protrudes from the opening of the housing  120 . The three pairs of memory alloy wires  130  are used to control the displacement of the lens carrier  110  in three directions, respectively. More specifically, the three directions include a first direction D 1 , a second direction D 2 , and a third direction D 3 , which are orthogonal to one other. The three pairs of memory alloy wires  130  include a first pair of memory alloy wires  131 , a second pair of memory alloy wires  132 , and a third pair of memory alloy wires  133 . The first pair of memory alloy wires  131 , the second pair of memory alloy wires  132 , and the third pair of memory alloy wires  133  are used to control the displacement of the lens carrier  110  in the first direction D 1 , the second direction D 2 , and the third direction D 3 , respectively. 
     Further, the control unit is electrically connected to the three pairs of memory alloy wires  130  and the three displacement detecting units  140   x,    140   y,  and  140   z.  The control unit controls the current of the three pairs of memory alloy wires  130  and utilizes the thermal shrinkage and cold expansion characteristics of the shape memory alloy. When the control unit controls the current to pass through the alloy wire, the alloy wire is tightened due to the rise in temperature. In this way, the control unit can control the displacement of the lens carrier  110  in three directions. 
     For example, as shown in  FIG. 1 , the lens carrier  110  includes a first movable structure  111  and a second movable structure  112 . The housing  120  includes a first fixing end  121  and a second fixing end  122 . The first movable structure  111  and the second movable structure  112  are arranged along a first diagonal direction of the lens carrier  110  on the plane where the first direction D 1  and the second direction D 2  are located, and the first fixing end  121  and the second fixing end  122  are arranged along a second diagonal direction of the lens carrier  110  on the plane where the first direction D 1  and the second direction D 2  are located. 
     Moreover, as shown in  FIG. 1 , two memory alloy wires  131   a  and  131   b  of the first pair of memory alloy wires  131  are respectively arranged on two opposite outer sides of the lens carrier  110  in the second direction D 2 . Both ends of one memory alloy wire  131   b  of the first pair of memory alloy wires  131  are respectively connected to the first fixing end  121  and the second movable structure  112 , and both ends of the other memory alloy wire  131   a  of the first pair of memory alloy wires  131  are respectively connected to the second fixing end  122  and the first movable structure  111 . In this way, when the control unit controls the current to pass through the first pair of memory alloy wires  131 , the rise of temperature makes the first pair of memory alloy wires  131  to be tightened, so that the control unit can control displacement of both ends of the lens carrier  110  in the first direction D 1 . 
     Similarly, as shown in  FIG. 1 , two memory alloy wires  132   a  and  132   b  of the second pair of memory alloy wires  132  are respectively arranged on two opposite outer sides of the lens carrier  110  in the first direction D 1 . Both ends of one memory alloy wire  132   a  of the second pair of memory alloy wires  132  are respectively connected to the first fixing end  121  and the first movable structure  111 , and both ends of the other memory alloy wire  132   b  of the second pair of memory alloy wires  132  are respectively connected to the second fixing end  122  and the second movable structure  112 . In this way, when the control unit controls the current to pass through the second pair of memory alloy wires  132 , the rise of temperature makes the second pair of memory alloy wires  132  to be tightened, so that the control unit can control displacement of both ends of the lens carrier  110  in the second direction D 2 . 
     On the other hand, as shown in  FIG. 2 , the lens carrier  110  further includes a first hook structure  113  and a second hook structure  114 . The first hook structure  113  and the second hook structure  114  are disposed on the lateral surface of the lens carrier  110  along a third direction D 3 . The housing  120  further includes a first pair of fixing ends  123   a  and  123   b  and a second pair of fixing ends  124   a  and  124   b.  The first pair of fixing ends  123   a  and  123   b  and the second pair of fixing ends  124   a  and  124   b  are respectively disposed on both sides of the housing  120  in the third direction D 3 . Both ends of one memory alloy wire  133   a  of the third pair of memory alloy wires  133  are respectively connected with the ends of the first pair of fixing ends  123   a  and  123   b.  One memory alloy wire  133   a  of the third pair of memory alloy wires  133  is arranged in the manner of returning back to one side of the third direction D 3  after winding the first hook structure  113 . On the other hand, both ends of the other memory alloy wire  133   b  of the third pair of memory alloy wires  133  are respectively connected to the ends of the second pair of fixing ends  124   a  and  124   b.  The other memory alloy wire  133   b  of the third pair of memory alloy wires  133  is arranged in the manner of returning back to the other side of the third direction D 3  after winding the second hook structure  114 . 
     In this way, when the control unit controls the current to pass through one memory alloy wire  133   a  of the third pair of memory alloy wires  133 , the rise of temperature makes one memory alloy wire  133   a  of the third pair of memory alloy wires  133  to be tightened, so that the control unit can control displacement of one end of the lens carrier  110  in the third direction D 3 . On the other hand, when the control unit controls the current to pass through the other memory alloy wire  133   b  of the third pair of memory alloy wires  133 , the rise of temperature makes the other memory alloy wire  133   b  of the third pair of memory alloy wires  133  to be tightened, so that the control unit can control displacement of the other end of the lens carrier  110  in the third direction D 3 . 
     Furthermore, as shown in  FIG. 1  and  FIG. 2 , each of the displacement detecting units  140   x,    140   y,  and  140   z  includes a magnetic element  141  and a magnetic field sensing element  142 . The magnetic element  141  is disposed on the lens carrier  110 . The magnetic field sensing element  142  is disposed on the housing  120  and corresponding to the magnetic element  141  to sense change of the magnetic field of the magnetic element  141  along each of the three directions when the lens carrier  110  moves. Moreover, in this embodiment, the magnetic element  141  of any one of the three displacement detecting units  140   x,    140   y,  and  140   z  is arranged at a position that can induce the corresponding magnetic field sensing element  142  and does not interfere with the magnetic field sensing elements  142  of the other two of the three displacement detecting units  140   x,    140   y,  and  140   z.  For example, in this embodiment, the magnetic field sensing element  142  is a Hall sensor, but the disclosure is not limited thereto. In other embodiments, the magnetic field sensing element  142  may also be a giant magnetoresistive sensor (GMR), a tunnel magnetoresistive sensor (TMR), and other elements capable of detecting changes in a magnetic field. 
     In this way, when the lens carrier  110  moves, each magnetic element  141  also moves. 
     Under the circumstances, the magnetic field received by its corresponding magnetic field sensing element  142  will change. Through sensing the change of magnetic field, the magnetic field sensing element  142  can calculate the displacement of the lens carrier  110  in three different directions. In this way, since the lens carrier  110  is positioned by each displacement detecting unit  140   x,    140   y,  and  140   z  by sensing the change in magnetic field, it is no longer necessary to take into consideration the influence of external resistance or temperature changes on the calculation of displacement, and there is no need to take into account the problem of inaccurate calculation of resistance when there is a considerable amount of deformation of the memory alloy wire. The method is adaptable for the situation where a greater amount of displacement is required. In addition, because the lens carrier  110  is positioned by each displacement detecting unit  140   x,    140   y,  and  140   z  by sensing the change in magnetic field, a faster response speed can be achieved, and the displacement of the lens carrier  110  can be acquired within the shortest time. Moreover, in this way, there is no need for the control unit to be provided with the control element for calculating the resistance of the three pairs of memory alloy wires  130 , the product cost can be reduced. 
     In summary, the lens positioning device of the disclosure can calculate the displacement of the lens carrier in three different directions through the arrangement of the magnetic elements and magnetic field sensing elements of the three displacement detecting units. In addition, since the data obtained by the above detection method will not be interfered by the deformation of the memory alloy wire or external resistance or temperature or other factors, the obtained values will be more accurate. Moreover, the method is adaptable for situations that require a greater amount of displacement, and has a faster response speed and can perform detection quickly. Furthermore, there is no need for the lens positioning device to be provided with the control element for calculating the resistance of the three pairs of memory alloy wires, the product cost can be reduced.