Patent Publication Number: US-2007097531-A1

Title: Optical devices

Description:
CROSS REFERENCE TO RELATED APPILCATIONS  
      This application is a Continuation-In-Part of pending U.S. patent application Ser. No. 11/266,832, filed Nov. 3, 2005 and entitled “Optical devices”. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates to optical devices, and in particular to optical devices reducing power consumption.  
      2. Description of the Related Art  
      In some cameras, focusing of lenses is driven by voice coil motors. The voice coil motors provide faster driving and more precise positioning.  
      The Biot-Savart law, applied in operation of the voice coil motors, indicates that a conducting wire with a length L is subject to a force F when energized by an electric current I and located in a magnetic field with a magnetic flux B. The direction of the magnetic field is perpendicular to that of the electric current I. The magnitude of the force F equals IL×B, and the direction thereof is perpendicular to those of the electric current and magnetic field.  
      Referring to  FIG. 1 , a conventional lens module  1  comprises a fixed magnet  11 , a movable coil  12 , a lens housing (or lens)  13 , a resilient arm  14 , and a housing  15 . The fixed magnet  11  is disposed in the movable coil  12 . A central magnetizing axis of the fixed magnet  11  is aligned with a central axis of the movable coil  12 , as indicated by line A of  FIG. 1 . The lens housing  13  is connected to the movable coil  12 . The resilient arm  14  is connected between the housing  15  and the movable coil  12 , supporting the movable coil  12  and lens housing  13 . When the movable coil  12  is energized by application of a current, a magnetic force is generated by interaction between a magnetic field provided by the fixed magnet  11  and the current, moving the movable coil  12  along the central axis (line A) thereof. The lens housing  13  connected to the movable coil  12  is thus moved, and focusing or zooming operation can be performed.  
      Nevertheless, the lens module  1  has a few drawbacks. When the movable coil  12  and lens housing  13  move to a certain position, the resilient arm  14  is elastically deformed, thereby providing resilience. To maintain the lens housing  13  in the certain position, the movable coil  12  must be continuously energized by application of a holding current, generating a magnetic force to overcome the resilience. Accordingly, power consumption of the lens module  1  is considerable.  
      Further, during operation of the lens module  1 , movement of the movable coil  12  is restricted. Namely, the movable coil  12  cannot move in a specific position. Specifically, when a central elevation axis of the movable coil  12  coincides with that of the fixed magnet  11 , as indicated by line B of  FIG. 1 , no magnetic force is generated therebetween. Thus, the movable coil  12  and lens housing  13  cannot be held in the specific position, in which the central elevation axes of the movable coil  12  and fixed magnet  11  coincide. Accordingly, universal focusing and zooming of the lens module  1  are adversely affected.  
      Additionally, the larger the moving distance of the movable coil  12  (the larger the zoom range of a lens), the larger the length of the fixed magnet  11 , increasing the size of the lens module  1 .  
      Hence, there is a need for an optical device with reduced size and power consumption and increased zoom distance.  
     BRIEF SUMMARY OF THE INVENTION  
      A detailed description is given in the following embodiments with reference to the accompanying drawings.  
      An exemplary embodiment of the invention provides an optical device comprising a base, a guide bar, a coil, a first fixed magnetic member, a second fixed magnetic member, and a lens housing. The guide bar is connected to the base and has a first central axis in an optical axis direction of the optical device. The coil slides on the guide bar and has a second central axis in the optical axis direction and a first central elevation axis. The second central axis is perpendicular to the first central elevation axis. The first fixed magnetic member is connected to the base and disposed in the coil. The first fixed magnetic member has a first central magnetizing axis and a second central elevation axis. The first central magnetizing axis is perpendicular to the second central elevation axis and aligned with the second central axis of the coil. The second central elevation axis is separated from the first central elevation axis. The second fixed magnetic member is disposed in the coil and separated from the first fixed magnetic member by a predetermined distance and has a second central magnetizing axis and a third central elevation axis. The first and second fixed magnetic members oppose each other with the same magnetic pole. The second central magnetizing axis is perpendicular to the third central elevation axis and aligned with the second central axis of the coil. The third central elevation axis is separated from the first central elevation axis. The first central elevation axis is between the second and third central elevation axes. The lens housing is connected to the coil. When the coil is energized by application of a current, a magnetic force is generated by interaction between the current and magnetic fields provided by the first and second fixed magnetic members, moving the coil and lens housing along the first central axis of the guide bar.  
      The optical device further comprises a position sensing member connected to the coil to detect movement of the coil.  
      The position sensing member comprises a Hall sensor, a reluctance sensor, or a photo interrupter.  
      The optical device further comprises a magnetic member and a metal plate. The metal plate is connected to the position sensing member. The magnetic member is connected to the base and opposes the metal plate. The coil is fixed to the guide bar by attraction between the magnetic member and the metal plate.  
      The optical device further comprises a magnetic-permeable member disposed between the first and second fixed magnetic members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention 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 cross section of a conventional lens module;  
       FIG. 2  is a schematic cross section of an optical device of a first embodiment of the invention; and  
       FIG. 3  is a schematic cross section of an optical device of a second embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.  
     First Embodiment  
      Referring to  FIG. 2 , the optical device  100  employs a solenoid principle and comprises a base  105 , a guide bar  110 , a coil  120 , a fixed magnetic member  130 , a lens housing  140 , a position sensing member  150 , a magnetic member  160 , and a metal plate  170 .  
      As shown in  FIG. 2 , the guide bar  110  is connected to the base  105  and has a first central axis  110   a  in an optical axis direction of the optical device  100 . Namely, the first central axis  110   a  is parallel to the optical axis direction of the optical device  100 .  
      The coil  120  slides on the guide bar  110  and has a second central axis  120   a  in the optical axis direction and a first central elevation axis  120   b . Specifically, the second central axis  120   a  is perpendicular to the first central elevation axis  120   b.    
      The fixed magnetic member  130  is connected to the base  105  and disposed in the coil  120 . The fixed magnetic member  130  has a central magnetizing axis  130   a  and a second central elevation axis  130   b . Specifically, the central magnetizing axis  130   a  is perpendicular to the second central elevation axis  130   b  and aligned with the second central axis  120   a  of the coil  120 . More specifically, the second central elevation axis  130   b  is separated from the first central elevation axis  120   b . Namely, no matter how the coil  120  moves, the first central elevation axis  120   b  thereof is separated from the second central elevation axis  130   b  of the fixed magnetic member  130 . Moreover, the fixed magnetic member  130  may be a magnet, with two opposite polarities (N and S polarities) varying along the central magnetizing axis  130   a.    
      The lens housing  140  is connected to the coil  120  and carries a lens (not shown). Specifically, connection between the lens housing  140  and the coil  120  is not limited to the configuration shown in  FIG. 2 .  
      The position sensing member  150  is connected to the coil  120 , detecting the moving position or movement thereof. The position sensing member  150  may be a Hall sensor, a reluctance sensor, or a photo interrupter. The magnetic member  160  is connected to the base  105 . The metal plate  170  is selectively connected to the position sensing member  150 . The position sensing member  150  is disposed between the metal plate  170  and the magnetic member  160 . The magnetic member  160  opposes the metal plate  170  and may be a magnet.  
      Being a Hall sensor, the position sensing member  150  can be selectively disposed in the coil  120  and oppose the fixed magnetic member  130 , detecting changes in magnetic flux density and/or polarity of the magnetic field produced by the fixed magnetic member  130  and/or magnetic member  160 . The moving position of the coil  120  can thus be obtained.  
      The following description is directed to operation of the optical device  100 .  
      When the coil  120  is energized by application of a current, a magnetic force is generated by interaction between the current and the magnetic field provided by the fixed magnetic member  130 , moving the coil  120  and lens housing  140  along the first central axis  110   a  of the guide bar  110 . The lens carried by the lens housing  140  can thus perform focus and zoom operations. Additionally, by detection of the position sensing member  150 , the coil  120  does not move to an ineffective position, in which the first central elevation axis  120   b  thereof coincides with the second central elevation axis  130   b  of the fixed magnetic member  130 .  
      In another aspect, when moving to a specific position (the lens in the lens housing  140  reaches a focus position), the coil  120  and lens housing  140  are fixed to the guide bar  110  by attraction between the magnetic member  160  and the metal plate  170 . At this point, no holding current is required to fix the coil  120  and lens housing  140 , thus reducing power consumption of the optical device  100 .  
     Second Embodiment  
      Referring to  FIG. 3 , the optical device  200  also employs the solenoid principle and comprises a base  205 , a guide bar  210 , a coil  220 , a first fixed magnetic member  230 , a second fixed magnetic member  240 , a magnetic-permeable member  245 , a lens housing  250 , a position sensing member  260 , a magnetic member  270 , and a metal plate  280 .  
      As shown in  FIG. 3 , the guide bar  210  is connected to the base  205  and has a first central axis  210   a  in an optical axis direction of the optical device  200 . Namely, the first central axis  210   a  is parallel to the optical axis direction of the optical device  200 .  
      The coil  220  slides on the guide bar  210  and has a second central axis  220   a  in the optical axis direction and a first central elevation axis  220   b . Specifically, the second central axis  220   a  is perpendicular to the first central elevation axis  220   b.    
      The first fixed magnetic member  230  is connected to the base  205  and disposed in the coil  220 . The first fixed magnetic member  230  has a first central magnetizing axis  230   a  and a second central elevation axis  230   b . Specifically, the first central magnetizing axis  230   a  is perpendicular to the second central elevation axis  230   b  and aligned with the second central axis  220   a  of the coil  220 , and the second central elevation axis  230   b  is separated from the first central elevation axis  220   b  of the coil  220 .  
      The second fixed magnetic member  240  is connected to the magnetic-permeable member  245 , disposed in the coil  220  and separated from the first fixed magnetic member  230  by a predetermined distance D. Similarly, the second fixed magnetic member  240  has a second central magnetizing axis  240   a  and a third central elevation axis  240   b . The second central magnetizing axis  240   a  is perpendicular to the third central elevation axis  240   b  and aligned with the second central axis  220   a  of the coil  220 . The third central elevation axis  240   b  is separated from the first central elevation axis  220   b  of the coil  220 . Specifically, the first central elevation axis  220   b  is between the second central elevation axis  230   b  and the third central elevation axis  240   b . Namely, no matter how the coil  220  moves, the first central elevation axis  220   b  thereof is between the second central elevation axis  230   b  of the first fixed magnetic member  230  and the third central elevation axis  240   b  of the second fixed magnetic member  240 . Moreover, the first fixed magnetic member  230  and second fixed magnetic member  240  may be magnets, with two opposite polarities (N and S polarities) varying along the first central magnetizing axis  230   a  and second central magnetizing axis  240   a . Specifically, as shown in  FIG. 3 , the first fixed magnetic member  230  and second fixed magnetic member  240  oppose each other with the same magnetic pole,  
      The magnetic-permeable member  245  is disposed between the first fixed magnetic member  230  and the second fixed magnetic member  240 , reducing repulsion therebetween. Moreover, the magnetic-permeable member  245  can effectively guide magnetic lines from the first fixed magnetic member  230  and second fixed magnetic member  240  into the coil  220 .  
      The lens housing  250  is connected to the coil  220  and carries a lens (not shown). Similarly, connection between the lens housing  250  and the coil  220  is not limited to the configuration shown in  FIG. 3 .  
      The position sensing member  260  is connected to the coil  220 , detecting the moving position or movement thereof. The position sensing member  260  may be a Hall sensor, a reluctance sensor, or a photo interrupter. The magnetic member  270  is connected to the base  205 . The metal plate  280  is selectively connected to the position sensing member  260 . The position sensing member  260  is disposed between the metal plate  280  and the magnetic member  270 . The magnetic member  270  opposes the metal plate  280  and may be a magnet.  
      If a Hall sensor, the position sensing member  260  can be selectively disposed in the coil  220  and oppose the first fixed magnetic member  230  and/or the second fixed magnetic member  240 , detecting changes in magnetic flux density and/or polarity of the magnetic field produced by the first fixed magnetic member  230  and/or second fixed magnetic member  240  and/or magnetic member  270 . The moving position of the coil  220  can thus be obtained.  
      The following description is directed to operation of the optical device  200 .  
      When the coil  220  is energized by application of a current, a magnetic force is generated by interaction between the current and magnetic fields provided by the first fixed magnetic member  230  and second fixed magnetic member  240 , moving the coil  220  and lens housing  250  along the first central axis  210   a  of the guide bar  210 . The lens carried by the lens housing  250  can thus perform focus and zoom operations. Additionally, by detection of the position sensing member  260 , the coil  220  does not move to two ineffective positions, in which the first central elevation axis  220   b  thereof coincides with the second central elevation axis  230   b  of the first fixed magnetic member  230  and third central elevation axis  240   b  of the second fixed magnetic member  240 .  
      Similarly, when moving to a specific position (the lens in the lens housing  250  reaches a focus position), the coil  220  and lens housing  250  are fixed to the guide bar  210  by attraction between the magnetic member  270  and the metal plate  280 . At this point, no holding current is required to fix the coil  220  and lens housing  250 , thus reducing power consumption of the optical device  200 .  
      Moreover, the predetermined distance D between the first fixed magnetic member  230  and the second fixed magnetic member  240  can be adjusted. Specifically, when the predetermined distance D is relatively small, the coil  220  receives relatively high strength magnetic fields or magnetic flux density from the first fixed magnetic member  230  and second fixed magnetic member  240 , thus increasing moving power. When the predetermined distance D, however, is relatively large, the distance between the second central elevation axis  230   b  and the third central elevation axis  240   b  is relatively large, thus increasing the moving distance or range of the coil  220 .  
      While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.