Patent Publication Number: US-2022229266-A1

Title: Lens autofocus actuating device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of U.S. patent application Ser. No. 16/830,500, filed on Mar. 26, 2020, which claims priority under 35 U.S.C. § 119(a) on Taiwan Patent Application No. 108114645 filed on Apr. 26, 2019, the entirety of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a lens actuating device, in particular, it relates to a lens autofocus actuating device that cooperates with a shape-memory alloy (SMA). 
     Description of the Related Art 
     The autofocus actuating device of the mobile phone camera module is one of the integral standard configurations of current smartphone. The smartphone needs to move the lens module to complete autofocus during shooting. 
     The design of an autofocus actuator involves a plurality of different technologies, including equipment such as a voice coil motor (VCM), a piezoelectric motor, and shape-memory alloy wire. Among these, the voice coil motor is the most widely used at present, and it has the advantages of low cost, high yield, and mature technology. It also has shortcomings, including a slow focusing speed, high power consumption, and susceptibility to magnetic interference. A plurality of new technologies have been put forward and discussed. Compared with autofocus actuators that use a voice coil motor, those using a shape-memory alloy wire have the advantages of lower costs and a larger actuation force. However, due to the nonlinear deformation curve and input current, as well as hysteresis, it is difficult to control position using the shape-memory alloy wire. 
     A shape-memory alloy wire can deform to change its length when heated by an electric current, and it can extend back to its original length when the electric current is switched off. Therefore, the focusing position of the lens module can be controlled by regulating the electric current running through the shape-memory alloy wire. 
     In the process of moving the lens module, however, controlling its dynamic tilt will affect the overall focusing effect and optical performance. Therefore, how to provide a lens autofocus actuating device that can control the dynamic tilt of the lens more accurately is an important subject at present. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the foregoing, one of the objects of the present invention is to provide a lens autofocus actuating device, which can regulate the dynamic tilt of the lens in the process of focusing and then accurately execute the focus control. 
     To achieve the above, the present invention is to provide a lens autofocus actuating device, which includes a base, a guide rail unit, a lens carrier, an actuating member, a plurality of balls, a shell and two resilient members. The guide rail unit is disposed on an upper surface of the base and has a fixing ring and a plurality of position-limiting members. The position-limiting members are disposed vertically on the fixing ring. The lens carrier is disposed above the base and located between the position-limiting members, wherein the outer side surface has a plurality of protrusions and cavities, and the disposing space consists of one of the cavities and the corresponding position-limiting members. The actuating member is disposed on the upper surface of the base and has two electrode terminal pairs and two shape-memory alloy wires disposed opposite each other. Each shape-memory alloy wire is in contact with a corresponding protrusion of the lens carrier, and the two ends of each shape-memory alloy wire are respectively connected to the electrodes of each group of electrode terminal pairs. The shape-memory alloy wires are driven by an electric current to produce thermal deformation and then actuate the lens carrier to move relative to the base. Each group of balls is positioned in the corresponding disposing space and in contact with the surface of the position-limiting members and the cavities. The shell is connected to the base to cover at least the guide rail unit, the lens carrier, and the actuating member. The two (or another even number) resilient members are disposed opposite each other, between the upper surface of the lens carrier and the shell. The resilient members provide a returning force to move the lens carrier in the direction of the base after the shape-memory alloy wires cool down. 
     In one embodiment of the present invention, the position-limiting members are uniformly disposed on the fixing ring with an included angle of 120 degrees between them. 
     In one embodiment of the present invention, each position-limiting member is L-shaped, and the notch of the L-shape faces the outer side surface of the lens carrier. 
     In summary, the lens autofocus actuating device of the present invention is to move the lens carrier relative to the base along the optical axis by using the guide rail unit and two groups of shape-memory alloy wires. In addition, the lens autofocus actuating device can limit the tilt angle of the lens carrier while it is moving by using the position-limiting members of the guide rail unit that are uniformly disposed on the fixing ring together with each group of balls, so as to realize a more accurate autofocusing of the lens. 
     The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to appreciate the features of the claimed invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The parts in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of at least one embodiment. In the drawings, like reference numerals designate corresponding parts throughout the various diagrams, and all the diagrams are schematic. 
         FIG. 1  is a schematic diagram illustrating the appearance of a lens autofocus actuating device according to a first embodiment of the present invention. 
         FIG. 2  is an exploded diagram showing the members of the lens autofocus actuating device according to the first embodiment of the present invention. 
         FIG. 3  is a top view diagram showing the lens autofocus actuating device according to the first embodiment of the present invention. 
         FIG. 4  is a side view diagram showing the lens autofocus actuating device according to the first embodiment of the present invention. 
         FIG. 5  is a top view diagram showing a lens autofocus actuating device according to a second embodiment of the present invention. 
         FIG. 6  is a top view diagram showing a lens autofocus actuating device according to a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made to the drawings to describe various inventive embodiments of the present disclosure in detail, wherein like numerals refer to like elements throughout. 
       FIG. 1  is an appearance diagram of a lens autofocus actuating device  10  of the first embodiment in the present invention.  FIG. 2  is an exploded diagram of the members of the lens autofocus actuating device  10 .  FIG. 3  is a top view diagram of the lens autofocus actuating device  10 .  FIG. 4  is a side view diagram of the lens autofocus actuating device  10 . 
     Please refer to both  FIG. 1  and  FIG. 2 , the lens autofocus actuating device  10  includes a base  11 , a guide rail unit  12 , a lens carrier  13 , an actuating member  14 , three groups of ball  15   a ,  15   b  and  15   c , a shell  16 , two resilient members  17   a  and  17   b , a circuit board  18  and a magnetic member  19 . 
     The base  11  has a slightly flat, rectangular shape, and has a central through hole  111  in the center. An upper surface  112  of the base  11  is provided with a support plate  113  and three groups of positioning members  114   a .  114   b  and  114   c . The support plate  113  has a first surface  1131  and a second surface  1132 , and is disposed vertically on one side of the rectangular base  11 . The positioning members  114   a ,  114   b  and  114   c  are uniformly disposed on the upper surface  112  around the central through hole  111 . Each group of positioning members has two adjacent protrusions P 01  and P 02 . 
     The circuit board  18  has a first surface  181  and a second surface  182 , and is disposed vertically on the upper surface  112  along one side of the base  11 . In this embodiment, the circuit board  18  is a flexible printed circuit board (FPC), the first surface  181  of which is in contact with the first surface  1131  of the support plate  113 . The first surface  181  of the circuit board  18  is affixed to the support plate  113 . In addition, the first surface  181  of the circuit board  18  is also provided with a Hall sensing member  183 , which is exposed on the second surface  1132  of the support plate  113 . With this configuration, space can be used more effectively to reduce the overall size, within a limited scope. In other embodiments, a circuit board with rigid supports can also be used, so that the support plate on the base can be omitted. Furthermore, the circuit board  18  can also be provided with a current driving chip or a control chip. 
     The guide rail unit  12  includes a fixing ring  121  and three position-limiting members  122   a ,  122   b  and  122   c . The fixing ring  121  is disposed on the upper surface  112  of the base  11  corresponding to the central through hole  111 , which is substantially located within the circle formed by three groups of positioning members  114   a ,  114   b  and  114   c . The three position-limiting members  122   a ,  122   b  and  122   c  are disposed vertically on the fixing ring  121 , and are uniformly disposed on the fixing ring  121 . Please also refer to  FIG. 3 , in which the included angles A 01 , A 02  and A 03  between the three position-limiting members  122   a ,  122   b  and  122   c  on the fixing ring  121  are about 120 degrees. 
     In other embodiments, the number of position-limiting members is not limited to three, and can be increased when the lens autofocus actuating device is enlarged or the material strength of the members is lower, and they can be uniformly disposed around the central through hole. For example, when there are four position-limiting members, the included angles between the members on the fixing ring  121  are each about 90 degrees. 
     It should be understood that the fixing ring  121  and the position-limiting members  122   a ,  122   b  and  122   c  can be made of metal, plastic steel, or plastic. In addition, each of the position-limiting members  122   a ,  122   b  and  122   c  is L-shaped, and each can be disposed on the fixing ring  121  by use of a welding joint, glue or another adhesive, high-temperature welding, or laser welding. In this embodiment, the L-shaped structures of the position-limiting members are pressed against the protrusions P 01  and P 02  of the positioning members, so as to fix the position of the position-limiting members. 
     The lens carrier  13  is disposed on the base  11 , and is substantially located within the circle formed by the position-limiting members  122   a ,  122   b  and  122   c . The outer side of the lens carrier  13  has two protrusions  131   a  and  131   b  as well as four cavities  132   a ,  132   b ,  132   c  and  132   d . The lens carrier  13  is used to connect the lens module (not shown in the figure), which can move along the optical axis in the space between the base  11  and the shell  16  after installation, so as to drive the lens module to move. 
     In this embodiment, the L-shaped position-limiting members  122   a ,  122   b  and  122   c  are respectively disposed with their notches toward the outer side of the lens carrier  13 . For details, the notch of position-limiting member  122   a  corresponds to cavity  132   a , the notch of position-limiting member  122   b  corresponds to cavity  132   b , and the notch of position-limiting member  122   c  corresponds to cavity  132   c , and a disposing space is formed between the each corresponding position-limiting member and cavity. 
     The actuating member  14  is disposed on the upper surface  112  of the base  11 , and includes two groups of electrode terminal pairs  141   a  and  141   b  as well as two groups of shape-memory alloy wires  142   a  and  142   b . The electrode terminal pair  141   a  has a first electrode E 1  and a second electrode E 2 , and the electrode terminal pair  141   b  has a third electrode E 3  and a fourth electrode E 4 . The two ends of shape-memory alloy wire  142   a  are respectively connected to the first electrode E 1  and the second electrode E 2  (please refer to  FIG. 4 ), and the two ends of shape-memory alloy wire  142   b  are respectively connected to the third electrode E 3  and the fourth electrode E 4 . The actuating member  14  can be actuated by the driving or controlling of a current drive chip or a control chip on the circuit board  18 . 
     Four electrodes E 1 , E 2 , E 3  and E 4  are respectively disposed at four corners of the rectangular base  11 , and two groups of shape-memory alloy wire  142   a  and  142   b  are disposed on opposite sides of the base  11 . In addition, the middle section of the shape-memory alloy wire  142   a  is connected to the lower edge of the protrusion  131   a  of the lens carrier  13  (as shown in  FIG. 4 ), and the middle section of the shape-memory alloy wire  142   b  is connected to the lower edge of the protrusion  131   b  of the lens carrier  13 , according to which, the shape-memory alloy wires  142   a  and  142   b  are approximately V-shaped in their initial state. The length of the shape-memory alloy wires  142   a  and  142   b  can be reduced by thermal deformation caused by an electric current, which can move the lens carrier upward relative to the base. When the electric current is switched off, the shape-memory alloy wires  142   a  and  142   b  will cool down and extend to their original length. Furthermore, the shrinkage of the shape-memory alloy wires  142   a  and  142   b  can be controlled by regulating the electric current, and then the position of the lens carrier  13  can also be controlled. Shape-memory alloy wires  142   a  and  142   b  that are heated by the resistance generated by an electric current is well known in the prior art, so the detailed description is omitted here. 
     In this embodiment, the first electrode E 1 , the second electrode E 2 , the third electrode E 3 , and the fourth electrode E 4  are composed of conductive metal plates. The second electrode E 2  and the fourth electrode E 4  are electrically connected to each other, and they may be composed of the same conductive metal plate and used for grounding. 
     Each group of balls  15   a ,  15   b  and  15   c  is disposed in the corresponding disposing space, which can be made of a material with a low friction coefficient, like metal (such as stainless steel) or precision ground ceramics. The balls are in contact with the surface of the position-limiting members  122   a ,  122   b  and  122   c  as well as the surface of the cavities  132   a ,  132   b  and  132   c , respectively. The balls  15   a ,  15   b  and  15   c  can be limited within the disposing space respectively by the position-limiting members  122   a ,  122   b ,  122   c  and the cavities  132   a ,  132   b  and  132   c  of the lens carrier  13 . When the lens carrier  13  is driven by the actuating member  14 , the balls  15   a ,  15   b  and  15   c  can roll relative to each other stably between the position-limiting members  122   a ,  122   b  and  122   c  and the cavities  132   a ,  132   b  and  132   c  of the lens carrier  13 . 
     The shell  16  is connected to the base  11  to form a disposing space, in which the above members are covered. To match with the base, the outer shape of the shell  16  is also slightly rectangular. The shell  16  is made of metal in this embodiment. 
     It is worth mentioning that the shell  16 , the fixing ring  121  and the lens carrier  13  respectively has through hole corresponding to the central through hole  111  of the base  11 , so that light can be transmitted to an image sensor through these through holes after the lens module is assembled. 
     Two resilient members  17   a  and  17   b  are disposed opposite each other, between the upper surface  112  of the lens carrier  13  and the shell  16 . The resilient members  17   a  and  17   b  provide a returning force to move the lens carrier  13  in the direction of the base  11  after the shape-memory alloy wires  142   a  and  142   b  cool down. It should be understood that if the resilient members  17   a  and  17   b  are compression springs, the two ends can be respectively connected and fixed to the lens carrier  13  and the shell  16  through the fixing members (not shown in the figure). Thus, when the lens carrier  13  is driven by the shape-memory alloy wires  142   a  and  142   b , the resilient members  17   a  and  17   b  will store elastic force due to deformation, which will be released and executed on the lens carrier when the driving of the shape-memory alloy wires  142   a  and  142   b  on the lens carrier  13  is discharged so that the lens carrier  13  will move in the direction of the base  11 . 
       FIG. 5  is a lens autofocus actuating device  10 A of the second embodiment. The difference from the lens autofocus actuating device  10  of the first embodiment is that the lens autofocus actuating device  10 A has four resilient members  17   c - 17   f  in addition to the resilient members  17   a - 17   b .  FIG. 6  is a lens autofocus actuating device  10 B of the third embodiment. The difference from the lens autofocus actuating device  10 A of the second embodiment is that the lens autofocus actuating device  10 B only has four resilient members  17   c - 17   f  located at even intervals. As mentioned above, an even number of resilient members may provide a more even returning force to the lens carrier  13 . In addition, a larger number of resilient members may result in a more stable movement of the lens carrier  13 . 
     In conclusion, the lens autofocus actuating device provided by the present invention is to form a dual-wire autofocus actuating member with two groups of shape-memory alloy wire, which can be independently controlled on the two sides of the lens module. In addition, three groups of ball in conjunction with the position-limiting members can be used to regulate the dynamic tilt when the lens carries drives the lens module to move up and down. Moreover, the lens autofocus actuating device can also be used as a closed-loop control of position feedback with the Hall sensing members and magnetic members, so as to realize more accurate autofocus. 
     Even though numerous characteristics and advantages of certain inventive embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only. Changes may be made in detail, especially in matters of arrangement of parts, within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.