Patent Publication Number: US-2007097532-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. 11/338,337, filed Jan. 23, 2006 and entitled “Optical devices”, which is a Continuation-In-Part of pending prior 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 having lenses capable of rapid focusing movement and precise positioning.  
      2. Description of the Related Art  
      In some conventional cameras, the focusing movement of lenses is driven by stepping motors. The lenses driven by the stepping motors are easily controlled and do not require additional electricity to maintain the position thereof. The stepping motors, however, provide poor positioning precision and slow driving speed. In addition, stepping motors are quite large in size. This reduces their applicability and increases the size of cameras in which they are implemented.  
      To overcome the aforementioned problems, the focusing movement of lenses in other conventional cameras is driven by voice coil motors, as disclosed in U.S. Pat. No. 5,939,804. The voice coil motors provide faster driving speed, better positioning precision, and a reduced size.  
      Generally, the Biot-Savart law is applied in operation of the voice coil motors. The Biot-Savart law indicates that a conducting wire with a length L is subject to a force F when energized with 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. A conventional voice coil motor or optical equipment applying the Biot-Savart law is disclosed in U.S. Pat. No. 5,939,804.  
      Moreover, in U.S. Pat. No. 4,678,951 and U.S. Pat. No. 5,939,804, voice coil motors or optical devices apply the Biot-Savart law and comprise a linear guiding structure. Voice coil motors or optical devices, as disclosed in U.S. Pat. No. 6,560,047, apply the Biot-Savart law and comprise a pre-compressed resilient mechanism (i.e. a suspension mechanism). Additionally, in a lens driving device disclosed in U.S. Pat. No. 6,856,469, a magnet (movable member) and a coil (fixed member) of a voice coil motor are disposed in a circumferential direction. The coil surrounds the magnet and the magnet moves upward and downward inside the coil.  
      Accordingly, the conventional cameras or optical devices applying the voice coil motors have the following drawbacks. The farther the lenses move, the higher the voltage required by the voice coil motors. When the lenses move to a target focus position, additional electricity (or electric current) is required by the voice coil motors to maintain the lenses at the target focus position. Thus, the conventional cameras or optical devices applying the voice coil motors consume a great deal of electricity, adversely affecting portability and applicability thereof.  
      Moreover, referring to  FIG. 14 , 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. 14 . 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. 14 , 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 a linearly guided optical device having a lens capable of rapid focusing movement and precise positioning with reduced power consumption.  
     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, at least one guide bar, a coil, a lens housing, and a magnetic member. The guide bar is connected to the base. The coil is disposed in the base. A central axis of the coil in the optical axis direction of the optical device is parallel to a central axis of the guide bar in the optical axis direction. The lens housing slidably fits on the guide bar. A central axis of the lens housing in the optical axis direction is also parallel to that of the guide bar in the optical axis direction. The lens housing slides along the central axis of the guide bar. The magnetic member is connected to the lens housing opposite the coil, providing a first magnetic field. When the coil is energized to generate a second magnetic field, the lens housing slides on the guide bar by attraction or repulsion of the first and second magnetic fields.  
      The optical device further comprises a magnetic-permeable member disposed in the coil to enhance attraction or repulsion between the magnetic member and the coil.  
      The optical device further comprises a magnetic field sensing member disposed on the base opposite the magnetic member to detect movement of the magnetic member.  
      The optical device further comprises a positioning member disposed on the base opposite the magnetic member. The positioning member attracts the magnetic member to bring the lens housing into abutment with the guide bar.  
      The positioning member comprises metal or a magnet.  
      The positioning member comprises a coil capable of being energized to generate a magnetic field to react with the magnetic member.  
      The optical device further comprises a lens and an image-sensing member. The lens is disposed in the lens housing. The image-sensing member is disposed in the base opposite the lens. 
    
    
     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 partial cross section of the optical device of a first embodiment of the invention;  
       FIG. 2  is a schematic partial cross section of the optical device of a second embodiment of the invention;  
       FIG. 3  is a schematic partial cross section of the optical device of a third embodiment of the invention;  
       FIG. 4  is a schematic partial cross section of the optical device of a fourth embodiment of the invention;  
       FIG. 5  is a schematic partial cross section of the optical device of a fifth embodiment of the invention;  
       FIG. 6  is a schematic partial cross section of the optical device of a sixth embodiment of the invention;  
       FIG. 7  is a schematic partial cross section of the optical device of a seventh embodiment of the invention;  
       FIG. 8  is a schematic partial cross section of the optical device of an eighth embodiment of the invention;  
       FIG. 9  is a schematic partial cross section of the optical device of a ninth embodiment of the invention;  
       FIG. 10  is a schematic partial cross section of the optical device of a tenth embodiment of the invention;  
       FIG. 11  is a schematic partial cross section of the optical device of an eleventh embodiment of the invention;  
       FIG. 12  is a schematic partial cross section of the optical device of a twelfth embodiment of the invention;  
       FIG. 13  is a schematic partial cross section of the optical device of a thirteenth embodiment of the invention; and  
       FIG. 14  is a schematic cross section of a conventional lens module. 
    
    
     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. 1 , the optical device  100  comprises a base  110 , two guide bars  120 , a coil  130 , a lens housing  140 , a magnetic member  150 , a magnetic-permeable member  160 , a magnetic field sensing member  170 , a positioning member  180 , a lens  190 , and an image-sensing member  195 .  
      As shown in  FIG. 1 , the guide bars  120  are connected to the base  110 , and the coil  130  is disposed in the base  110 . Specifically, a central axis A of the coil  130  in the optical axis direction of the optical device is parallel to a central axis B of each guide bar  120  in the optical axis direction. Moreover, the magnetic-permeable member  160  is disposed in the coil  130 . In this embodiment, the magnetic-permeable member  160  is a yoke.  
      The lens housing  140  slidably fits on the guide bars  120 . A central axis A of the lens housing  140  in the optical axis direction is parallel to the central axis B of each guide bar  120  in the optical axis direction. The lens housing  140  can thus slide along the central axes of the guide bars  120 . Moreover, the lens  190  is disposed in the lens housing  140 .  
      The magnetic member  150  is connected to the lens housing  140  opposite the coil  130 . Specifically, a central axis A of the magnetic member  150  in the optical axis direction is aligned with that of the coil  130 , and the magnetic member  150  is disposed above the coil  130 . The magnetic member  150  provides a first magnetic field. The direction of the first magnetic field is substantially parallel to the central axis of each guide bar  120  or the lens housing  140 . The magnetic member  150  may be a magnet.  
      The magnetic field sensing member  170  is disposed on the base  110  opposite the magnetic member  150 . The magnetic field sensing member  170  detects movement of the magnetic member  150 . For example, the magnetic field sensing member  170  may be a Hall sensor connected to a controller (not shown) for measuring magnetic field strength and polarity. The movement and position of the magnetic member  150  can be obtained by detecting changes in magnetic flux density and/or polarity of the magnetic field produced by magnetic member  150  with the Hall sensor.  
      The positioning member  180  is disposed on the base  110  opposite the magnetic member  150 . The positioning member  180  may be metal (such as an iron plate) or a magnet.  
      The image-sensing member  195  is disposed in the base  110  opposite the lens  190 . The image-sensing member  195  may be a CCD or a CMOS.  
      The following description is directed to operation of the optical device  100  or focusing movement of the lens  190 .  
      As shown in  FIG. 1 , the magnetic member  150  connected to the lens housing  140  provides the first magnetic field having a direction substantially parallel to the central axis of each guide bar  120  or the lens housing  140 . When the coil  130  is energized, a second magnetic field having a direction parallel to the central axis of each guide bars  120  or the lens housing  140 , is generated in the center of the coil  130 . When the directions of the first and second magnetic fields are the same, the magnetic member  150  and coil  130  attract each other. Conversely, when the directions of the first and second magnetic fields are opposite, the magnetic member  150  and coil  130  repulse each other. Accordingly, the lens housing  140  can slide on the guide bars  120  by attraction and repulsion of the first and second magnetic fields, thereby adjusting the focus position of the lens  190  (i.e. the distance between the lens  190  and the image-sensing member  195 ). The direction of the second magnetic field is determined by the direction of the electric current applied in the coil  130 , and the strength of the second magnetic field is determined according to the magnitude of the electric current applied in the coil  130 . Moreover, the magnetic-permeable member  160  can effectively guide magnetic lines provided by the first magnetic field into the coil  130 , thereby enhancing attraction or repulsion between the magnetic member  150  and the coil  130 .  
      The magnetic field sensing member  170  (Hall sensor) detects the changes in magnetic flux density and/or polarity of the magnetic field produced by magnetic member  150  and transforms the detected changes in magnetic flux density into a signal. The signal is transmitted to the controller connected to the magnetic field sensing member  170  (Hall sensor) and the position and speed of the magnetic member  150  are thus obtained. The controller can adjust the magnitude of the electric current applied in the coil  130  according to the signal, changing the moving speed of the lens housing  140  or lens  190 . The focusing speed of the lens  190  is thus adjusted.  
      Moreover, the guide bars  120  can prevent displacement of the lens housing  140  by rotation torque resulting from deviation of magnetic force, thereby ensuring straight movement of the lens housing  140 . Nevertheless, when the lens housing  140  is fitted on the guide bars  120 , minor tolerance of assembly exists there between. By attraction between the magnetic member  150  and the positioning member  180 , the lens housing  140  can tightly abut one of the guide bars  120  and slide thereon. Accordingly, inclination of the lens housing  140  can thus be prevented. Namely, the lens housing  140  can slide on the guide bars  120  without deviation by attraction between the magnetic member  150  and the positioning member  180 .  
     Second Embodiment  
      Elements corresponding to those in the first embodiment share the same reference numerals.  
      Referring to  FIG. 2 , the difference between the second and the first embodiment is that the optical device  100 ′ of this embodiment does not comprise a magnetic-permeable member. Nevertheless, the lens housing  140  can still slide on the guide bars  120  by attraction or repulsion of the first and second magnetic fields, thereby adjusting the focus position of the lens  190  (i.e. the distance between the lens  190  and the image-sensing member  195 ).  
      The structure, disposition, and function of other elements of the optical device  100 ′ are the same as those of the optical device  100 , and explanation thereof is omitted.  
     Third Embodiment  
      Referring to  FIG. 3 , the optical device  300  comprises a base  310 , two guide bars  320 , two coils  330 , a lens housing  340 , two magnetic members  350 , a magnetic field sensing member  370 , a positioning member  380 , a lens  390 , and an image-sensing member  395 .  
      As shown in  FIG. 3 , the guide bars  320  are connected to the base  310 . The lens housing  340  slidably fits on the guide bars  320 . A central axis A of the lens housing  340  in the optical axis direction of the optical device is parallel to a central axis B of each guide bar  320 . The lens housing  340  can thus slide along the central axes of the guide bars  320 . Moreover, the lens  390  is disposed in the lens housing  340 .  
      The coils  330  are disposed in the base  310  and respectively fit on the guide bars  320 . Specifically, a central axis B of each coil  330  in the optical axis direction of the optical device is aligned with the central axis B of each guide bar  320  in the optical axis direction.  
      The magnetic members  350  are connected to the lens housing  340  and slidably fit on the guide bars  320 , respectively. Specifically, the magnetic members  350  are respectively disposed opposite the coils  330 . A central axis B of each magnetic member  350  in the optical axis direction is aligned with that of each corresponding coil  330 , and the magnetic members  350  are disposed above the coils  330 . Each magnetic member  350  provides a first magnetic field. The direction of the first magnetic field is substantially parallel to the central axis of each guide bar  320  or the lens housing  340 . The magnetic members  350  may be magnets.  
      The magnetic field sensing member  370  is disposed on the base  310  opposite one of the magnetic members  350 . The magnetic field sensing member  370  detects movement of the magnetic members  350 . The magnetic field sensing member  370  may be a Hall sensor connected to a controller (not shown) for measuring magnetic field strength and polarity. The movement and position of the magnetic members  350  can be obtained by detecting changes in magnetic flux density and/or polarity of the magnetic fields produced by magnetic members  350  with the Hall sensor.  
      The positioning member  380  is disposed the base  310  opposite one of the magnetic members  350 . The positioning member  380  may be metal (such as an iron plate) or a magnet.  
      The image-sensing member  395  is disposed in the base  310  opposite the lens  390 . The image-sensing member  395  may be a CCD or a CMOS.  
      The following description is directed to operation of the optical device  300  or focusing movement of the lens  390 .  
      As shown in  FIG. 3 , each magnetic member  350  connected to the lens housing  340  provides the first magnetic field having a direction substantially parallel to the central axis of each guide bar  320  or the lens housing  340 . When the coils  330  are simultaneously energized, a second magnetic field having a direction parallel to the central axis of each guide bar  320  or the lens housing  340  is generated in the center of each coil  330 . When the directions of the first and second magnetic fields are the same, the magnetic members  350  and coils  330  attract each other. Conversely, when the directions of the first and second magnetic fields are opposite, the magnetic members  350  and coils  330  repulse each other. Accordingly, the lens housing  340  can slide on the guide bars  320  by attraction and repulsion of the first and second magnetic fields, thereby adjusting focus position of the lens  390  (i.e. the distance between the lens  390  and the image-sensing member  395 ). The direction of the second magnetic field is determined by the direction of the electric current applied in each coil  330 , and the strength of the second magnetic field is determined according to the magnitude of the electric current applied in each coil  330 . In this embodiment, the directions of the electric currents applied in the coils  330  must be the same.  
      Moreover, the guide bars  320  may comprise a magnetic-permeable material, such that magnetic lines provided by the first magnetic field can be effectively guided into the coils  330  or magnetic lines provided by the second magnetic field effectively guided into the magnetic members  350 . Accordingly, attraction or repulsion between the magnetic members  350  and the coils  330  is enhanced.  
      The magnetic field sensing member  370  (Hall sensor) detects the changes in magnetic flux density and/or polarity of the magnetic fields produced by magnetic members  350  and transforms the detected changes into a signal. The signal is transmitted to the controller connected to the magnetic field sensing member  370  (Hall sensor) and the position and speed of the magnetic members  350  are thus obtained. The controller can adjust the magnitude of the electric currents applied in the coils  330  according to the signal, changing the moving speed of the lens housing  340  or lens  390 . The focusing speed of the lens  390  is thus adjusted.  
      The guide bars  320  can prevent displacement of the lens housing  340  by rotation torque resulting from deviation of magnetic force, thereby ensuring straight movement of the lens housing  340 . When the lens housing  340  is fitted on the guide bars  320 , a minor tolerance of assembly exists there between. By attraction between one of the magnetic members  350  and the positioning member  380 , the lens housing  340  can tightly abut one of the guide bars  320  and slide thereon. Accordingly, inclination of the lens housing  340  can thus be prevented. Namely, the lens housing  340  can slide on the guide bars  320  without deviation by attraction between one of the magnetic members  350  and the positioning member  380 .  
     Fourth Embodiment  
      Referring to  FIG. 4 , the optical device  400  comprises a base  410 , two guide bars  420 , a lens housing  430 , a coil  440 , a first magnetic member  450 , a second magnetic member  455 , a third magnetic member  456 , a magnetic-permeable member  460 , a magnetic field sensing member  470 , a positioning member  480 , a lens  490 , and an image-sensing member  495 .  
      As shown in  FIG. 4 , the guide bars  420  are connected to the base  410 , and the lens housing  430  slidably fits on the guide bars  420 . A central axis A of the lens housing  430  in the optical axis direction of the optical device is parallel to a central axis B of each guide bar  420  in the optical axis direction. The lens housing  430  can thus slide along the central axes of the guide bars  420 . Moreover, the lens  490  is disposed in the lens housing  430 .  
      The coil  440  is disposed on the lens housing  430 . A central axis A of the coil  440  in the optical axis direction is parallel to the central axis B of each guide bar  420 .  
      The first magnetic member  450  is disposed in the base  410  opposite the coil  440  and comprises a through hole  451 . Specifically, a central axis A of the first magnetic member  450  in the optical axis direction is aligned with that of the coil  440 , and the first magnetic member  450  is disposed under the coil  440 . The first magnetic member  450  provides a first magnetic field. The direction of the first magnetic field is substantially parallel to the central axis of each guide bar  420  or the lens housing  430 . The first magnetic member  450  may be a magnet.  
      The second magnetic member  455  and third magnetic member  456  are connected to the lens housing  430 .  
      The magnetic-permeable member  460  is disposed on the lens housing  430  and in the coil  440 . The magnetic-permeable member  460  may be a yoke.  
      The magnetic field sensing member  470  and positioning member  480  are disposed on the base  410  and opposite the second magnetic member  455  and third magnetic member  456 , respectively.  
      The image-sensing member  495  is disposed in the base  410  and under the first magnetic member  450 . Specifically, the image-sensing member  495  is disposed opposite the lens  490  below the through hole  451  of the first magnetic member  450 . The image-sensing member  495  may be a CCD or a CMOS.  
      The following description is directed to operation of the optical device  400  or focusing movement of the lens  490 .  
      As shown in  FIG. 4 , the first magnetic member  450  disposed in the base  410  provides the first magnetic field having a direction substantially parallel to the central axis of each guide bar  420  or the lens housing  430 . When the coil  440  is energized, a second magnetic field having a direction parallel to the central axis of each guide bar  420  or the lens housing  430  is generated in the center of the coil  440 . When the directions of the first and second magnetic fields are the same, the first magnetic member  450  and coil  440  attract each other. Conversely, when the directions of the first and second magnetic fields are opposite, the first magnetic member  450  and coil  440  repulse each other. Accordingly, the lens housing  430  can slide on the guide bars  420  by attraction and repulsion of the first and second magnetic fields, thereby adjusting focus position of the lens  490  (i.e. the distance between the lens  490  and the image-sensing member  495 ). The direction of the second magnetic field is determined by the direction of the electric current applied in the coil  440 , and the strength of the second magnetic field is determined according to the magnitude of the electric current applied in the coil  440 . The magnetic-permeable member  460  can effectively guide magnetic lines provided by the first magnetic field into the coil  440 , thereby enhancing attraction or repulsion between the first magnetic member  450  and the coil  440 .  
      Similarly, the movement of the lens housing  430  can be detected by interaction between the second magnetic member  455  and magnetic field sensing member  470 , and the positioning member  480  attracts the third magnetic member  456  to bring the lens housing  430  into abutment with the guide bars  420 .  
     Fifth Embodiment  
      Elements corresponding to those in the fourth embodiment share the same reference numerals.  
      Referring to  FIG. 5 , the difference between the fifth and the fourth embodiment is that the optical device  400 ′ of this embodiment does not comprise a magnetic-permeable member. Nevertheless, the lens housing  430  can still slide on the guide bars  420  by attraction or repulsion of the first and second magnetic fields, thereby adjusting the focus position of the lens  490  (i.e. the distance between the lens  490  and the image-sensing member  495 ).  
      The structure, disposition, and function of other elements of the optical device  400 ′ are the same as those of the optical device  400 , and explanation thereof is omitted.  
     Sixth Embodiment  
      Referring to  FIG. 6 , the optical device  600  comprises a base  610 , two guide bars  620 , a lens housing  630 , two coils  640 , two first magnetic members  650 , a second magnetic member  655 , a third magnetic member  656 , a magnetic field sensing member  670 , a positioning member  680 , a lens  690 , and an image-sensing member  695 .  
      As shown in  FIG. 6 , the guide bars  620  are connected to the base  610 , and the lens housing  630  slidably fits on the guide bars  620 . A central axis A of the lens housing  630  in the optical axis direction of the optical device is parallel to a central axis B of each guide bar  620  in the optical axis direction. The lens housing  630  can thus slide along the central axes of the guide bars  620 . Moreover, the lens  690  is disposed in the lens housing  630 .  
      The coils  640  are disposed on the lens housing  630  and respectively fit on the guide bars  620 . Specifically, a central axis B of each coil  640  in the optical axis direction is aligned with the central axis B of each guide bar  620 .  
      The first magnetic members  650  are disposed in the base  610  and slidably fit on the guide bars  620 , respectively. Specifically, a central axis B of each first magnetic member  650  in the optical axis direction is aligned with that of each corresponding coil  640 , and the first magnetic members  650  are disposed under the coils  640 . Each first magnetic member  650  provides a first magnetic field. The direction of the first magnetic field is substantially parallel to the central axis of each guide bar  620 . The first magnetic members  650  may be magnets.  
      The second magnetic member  655  and third magnetic member  656  are connected to the lens housing  630 .  
      The magnetic field sensing member  670  and positioning member  680  are disposed on the base  610  and opposite the second magnetic member  655  and third magnetic member  656 , respectively.  
      The image-sensing member  695  is disposed in the base  610  and under the first magnetic members  650 . Specifically, the image-sensing member  695  is disposed opposite the lens  690  below a through hole  611  of the base  610 . The image-sensing member  695  may be a CCD or a CMOS.  
      Moreover, the guide bars  620  may optionally comprise a magnetic-permeable material.  
      The following description is directed to operation of the optical device  600  or focusing movement of the lens  690 .  
      As shown in  FIG. 6 , each first magnetic member  650  disposed in the base  610  provides the first magnetic field having a direction substantially parallel to the central axis of each guide bar  620 . When the coils  640  are simultaneously energized, a second magnetic field having a direction parallel to the central axis of each guide bar  620  is generated in the center of each coil  640 . When the directions of the first and second magnetic fields are the same, the first magnetic members  650  and coils  640  attract each other. Conversely, when the directions of the first and second magnetic fields are opposite, the first magnetic members  650  and coils  640  repulse each other. Accordingly, the lens housing  630  can slide on the guide bars  620  by attraction and repulsion of the first and second magnetic fields, thereby adjusting focus position of the lens  690  (i.e. the distance between the lens  690  and the image-sensing member  695 ). The direction of the second magnetic field is determined by the direction of the electric current applied in each coil  640 , and the strength of the second magnetic field is determined according to the magnitude of the electric current applied in each coil  640 . Moreover, when the guide bars  620  comprise the magnetic-permeable material, magnetic lines provided by the first magnetic field can be more effectively guided into the coils  640 . Attraction or repulsion between the first magnetic members  650  and the coils  640  is thus enhanced.  
      Similarly, the movement of the lens housing  630  can be detected by interaction between the second magnetic member  655  and magnetic field sensing member  670 , and the positioning member  680  attracts the third magnetic member  656  to bring the lens housing  630  into abutment with the guide bars  620 .  
     Seventh Embodiment  
      Referring to  FIG. 7 , the optical device  700  comprises a base  710 , a lens housing  720 , a coil  730 , a magnetic member  750 , a magnetic field sensing member  770 , a positioning member  780 , a lens  790 , and an image-sensing member  795 .  
      As shown in  FIG. 7 , the base  710  comprises an inner wall  711 . The lens housing  720  is slidably disposed in the base  710  and abuts the inner wall  711  thereof. Namely, the lens housing  720  slidably abuts the inner wall  711  of the base  710 . Moreover, the lens  790  is disposed in the lens housing  720 .  
      The coil  730  is disposed in the base  710 . A central axis A of the coil  730  in the optical axis direction of the optical device is aligned with a central axis A of the lens housing  720  in the optical axis direction.  
      The magnetic member  750  is connected to the lens housing  720  opposite the coil  730 . Specifically, a central axis A of the magnetic member  750  in the optical axis direction is aligned with that of the coil  730 , and the magnetic member  750  is disposed above the coil  730 . The magnetic member  750  provides a first magnetic field. The direction of the first magnetic field is substantially parallel to the central axis of the lens housing  720 . The magnetic member  750  may be a magnet.  
      The magnetic field sensing member  770  is disposed in the base  710  opposite the magnetic member  750 . The magnetic field sensing member  770  detects movement of the magnetic member  750 . The magnetic field sensing member  770  may be a Hall sensor connected to a controller (not shown) for measuring magnetic field strength and polarity. The movement and position of the magnetic member  750  can be obtained by detecting changes in magnetic flux density and/or polarity of the magnetic field produced by magnetic member  750  with the Hall sensor.  
      The positioning member  780  is disposed in the base  710  opposite the magnetic member  750 . The positioning member  780  may be metal (such as an iron plate) or a magnet.  
      The image-sensing member  795  is disposed in the base  710  opposite the lens  790 . Specifically, the image-sensing member  795  is disposed opposite the lens  790  below a through hole  711  of the base  710 . The image-sensing member  795  may be a CCD or a CMOS.  
      The following description is directed to operation of the optical device  700  or focusing movement of the lens  790 .  
      As shown in  FIG. 7 , the magnetic member  750  connected to the lens housing  720  provides the first magnetic field having a direction substantially parallel to the central axis of A the lens housing  720 . When the coil  730  is energized, a second magnetic field having a direction parallel to the central axis A of the lens housing  720  is generated in the center of the coil  730 . When the directions of the first and second magnetic fields are the same, the magnetic member  750  and coil  730  attract each other. Conversely, when the directions of the first and second magnetic fields are opposite, the magnetic member  750  and coil  730  repulse each other. Accordingly, the lens housing  720  can slide in the base  710  by attraction and repulsion of the first and second magnetic fields, thereby adjusting focus position of the lens  790  (i.e. the distance between the lens  790  and the image-sensing member  795 ). The direction of the second magnetic field is determined by the direction of the electric current applied in the coil  730 , and the strength of the second magnetic field is determined according to the magnitude of the electric current applied in the coil  730 .  
      The magnetic field sensing member  770  (Hall sensor) detects the changes in magnetic flux density and polarity of the magnetic field produced by magnetic member  750  and transforms the detected changes into a signal. The signal is transmitted to the controller connected to the magnetic field sensing member  770  (Hall sensor) and the position and speed of the magnetic member  750  are thus obtained. The controller can adjust the magnitude of the electric current applied in the coil  730  according to the signal, changing the moving speed of the lens housing  720  or lens  790 . The focusing speed of the lens  790  is thus adjusted.  
      When the lens housing  720  is disposed in the base  710 , a minor tolerance of assembly exists between the lens housing  720  and the inner wall  711  of the base  710 . By attraction between the magnetic member  750  and the positioning member  780 , the lens housing  720  can tightly abut the inner wall  711  of the base  710  and slide thereon. Accordingly, inclination of the lens housing  720  can thus be prevented. Namely, the lens housing  720  can slide in the base  710  without deviation by attraction between the magnetic member  750  and the positioning member  780 .  
     Eighth Embodiment  
      Elements corresponding to those in the seventh embodiment share the same reference numerals.  
      Referring to  FIG. 8 , the difference between the eighth and the seventh embodiment is that the optical device  700 ′ of this embodiment further comprises a magnetic-permeable member  760  disposed in the coil  730 . The magnetic-permeable member  760  guides magnetic lines provided by the first magnetic field into the coil  730 , thereby enhancing attraction or repulsion between the magnetic member  750  and the coil  730 . The magnetic-permeable member  760  may be a yoke.  
      The structure, disposition, and function of other elements of the optical device  700 ′ are the same as those of the optical device  700 , and explanation thereof is omitted.  
     Ninth Embodiment  
      Referring to  FIG. 9 , the optical device  900  comprises a base  910 , a lens housing  920 , a coil  930 , a first magnetic member  950 , a second magnetic member  955 , a third magnetic member  956 , a magnetic field sensing member  970 , a positioning member  980 , a lens  990 , and an image-sensing member  995 .  
      As shown in  FIG. 9 , the base  910  comprises an inner wall  911 . The lens housing  920  is slidably disposed in the base  910  and abuts the inner wall  911  thereof Namely, the lens housing  920  slidably abuts the inner wall  911  of the base  910 . Moreover, the lens  990  is disposed in the lens housing  920 .  
      The coil  930  is disposed on the lens housing  920 . A central axis A of the coil  930  in the optical axis direction of the optical device is aligned with a central axis A of the lens housing  920  in the optical axis direction.  
      The first magnetic member  950  is disposed in the base  910  opposite the coil  930 . Additionally, the first magnetic member  950  comprises a through hole  951 . Specifically, a central axis A of the first magnetic member  950  in the optical axis direction is aligned with that of the coil  930 , and the first magnetic member  950  is disposed under the coil  930 . The first magnetic member  950  provides a first magnetic field. The direction of the first magnetic field is substantially parallel to the central axis of the lens housing  920 . The first magnetic member  950  may be a magnet.  
      The second magnetic member  955  and third magnetic member  956  are disposed in the lens housing  920 .  
      The magnetic field sensing member  970  and positioning member  980  are disposed in the base  910  and opposite the second magnetic member  955  and third magnetic member  956 , respectively.  
      The image-sensing member  995  is disposed in the base  910  and under the first magnetic member  950 . Specifically, the image-sensing member  995  is disposed opposite the lens  990  below the through hole  951  of the first magnetic member  950 . The image-sensing member  995  may be a CCD or a CMOS.  
      The following description is directed to operation of the optical device  900  or focusing movement of the lens  990 .  
      As shown in  FIG. 9 , the first magnetic member  950  disposed in the base  910  provides the first magnetic field having a direction substantially parallel to the central axis of the lens housing  920 . When the coil  930  is energized, a second magnetic field having a direction parallel to the central axis of the lens housing  920  is generated in the center of the coil  930 . When the directions of the first and second magnetic fields are the same, the first magnetic member  950  and coil  930  attract each other. Conversely, when the directions of the first and second magnetic fields are opposite, the first magnetic member  950  and coil  930  repulse each other. Accordingly, the lens housing  920  can slide in the base  910  by attraction and repulsion of the first and second magnetic fields, thereby adjusting focus position of the lens  990  (i.e. the distance between the lens  990  and the image-sensing member  995 ). The direction of the second magnetic field is determined by the direction of the electric current applied in the coil  930 , and the strength of the second magnetic field is determined according to the magnitude of the electric current applied in the coil  930 .  
      Similarly, the movement of the lens housing  920  can be detected by interaction between the second magnetic member  955  and magnetic field sensing member  970 , and the positioning member  980  attracts the third magnetic member  956  to bring the lens housing  920  into abutment with the base  910 .  
     Tenth Embodiment  
      Elements corresponding to those in the ninth embodiment share the same reference numerals.  
      Referring to  FIG. 10 , the difference between the tenth and the ninth embodiment is that the optical device  900 ′ of this embodiment further comprises a magnetic-permeable member  960  disposed in the coil  930 . The magnetic-permeable member  960  guides magnetic lines provided by the first magnetic field into the coil  930 , thereby enhancing attraction or repulsion between the first magnetic member  950  and the coil  930 . The magnetic-permeable member  960  may be a yoke.  
      The structure, disposition, and function of other elements of the optical device  900 ′ are the same as those of the optical device  900 , and explanation thereof is omitted.  
     Eleventh Embodiment  
      Referring to  FIG. 11 , the optical device  1100  employs a solenoid principle and comprises a base  1105 , a guide bar  110 , a coil  1120 , a fixed magnetic member  1130 , a lens housing  1140 , a position sensing member  1150 , a magnetic member  1160 , and a metal plate  1170 .  
      As shown in  FIG. 11 , the guide bar  1110  is connected to the base  1105  and has a first central axis  1110   a  in an optical axis direction of the optical device  1100 . Namely, the first central axis  1110   a  is parallel to the optical axis direction of the optical device  1100 .  
      The coil  1120  slides on the guide bar  1110  and has a second central axis  1120   a  in the optical axis direction and a first central elevation axis  1120   b . Specifically, the second central axis  1120   a  is perpendicular to the first central elevation axis  1120   b.    
      The fixed magnetic member  1130  is connected to the base  1105  and disposed in the coil  1120 . The fixed magnetic member  1130  has a central magnetizing axis  1130   a  and a second central elevation axis  1130   b . Specifically, the central magnetizing axis  1130   a  is perpendicular to the second central elevation axis  1130   b  and aligned with the second central axis  1120   a  of the coil  1120 . More specifically, the second central elevation axis  1130   b  is separated from the first central elevation axis  1120   b . Namely, no matter how the coil  1120  moves, the first central elevation axis  1120   b  thereof is separated from the second central elevation axis  1130   b  of the fixed magnetic member  1130 . Moreover, the fixed magnetic member  1130  may be a magnet, with two opposite polarities (N and S polarities) varying along the central magnetizing axis  1130   a.    
      The lens housing  1140  is connected to the coil  1120  and carries a lens (not shown). Specifically, connection between the lens housing  1140  and the coil  1120  is not limited to the configuration shown in  FIG. 11 .  
      The position sensing member  1150  is connected to the coil  1120 , detecting the moving position or movement thereof. The position sensing member  1150  may be a Hall sensor, a reluctance sensor, or a photo interrupter. The magnetic member  1160  is connected to the base  1105 . The metal plate  1170  is selectively connected to the position sensing member  1150 . The position sensing member  1150  is disposed between the metal plate  1170  and the magnetic member  1160 . The magnetic member  1160  opposes the metal plate  1170  and may be a magnet.  
      Being a Hall sensor, the position sensing member  1150  can be selectively disposed in the coil  1120  and oppose the fixed magnetic member  1130 , detecting changes in magnetic flux density and/or polarity of the magnetic field produced by the fixed magnetic member  1130  and/or magnetic member  1160 . The moving position of the coil  1120  can thus be obtained.  
      The following description is directed to operation of the optical device  1100 .  
      When the coil  1120  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  1130 , moving the coil  1120  and lens housing  1140  along the first central axis  1110   a  of the guide bar  1110 . The lens carried by the lens housing  1140  can thus focus and zoom. Additionally, by detection of the position sensing member  1150 , the coil  1120  does not move to an ineffective position, in which the first central elevation axis  1120   b  thereof coincides with the second central elevation axis  1130   b  of the fixed magnetic member  1130 .  
      In another aspect, when moving to a specific position (the lens in the lens housing  1140  reaches a focus position), the coil  1120  and lens housing  1140  are fixed to the guide bar  1110  by attraction between the magnetic member  1160  and the metal plate  1170 . At this point, no holding current is required to fix the coil  1120  and lens housing  1140 , thus reducing power consumption of the optical device  1100 .  
     Twelfth Embodiment  
      Referring to  FIG. 12 , the optical device  1200  also employs the solenoid principle and comprises a base  1205 , a guide bar  1210 , a coil  1220 , a first fixed magnetic member  1230 , a second fixed magnetic member  1240 , a magnetic-permeable member  1245 , a lens housing  1250 , a position sensing member  1260 , a magnetic member  1270 , and a metal plate  1280 .  
      As shown in  FIG. 12 , the guide bar  1210  is connected to the base  1205  and has a first central axis  1210   a  in an optical axis direction of the optical device  1200 . Namely, the first central axis  1210   a  is parallel to the optical axis direction of the optical device  1200 .  
      The coil  1220  slides on the guide bar  1210  and has a second central axis  1220   a  in the optical axis direction and a first central elevation axis  1220   b . Specifically, the second central axis  1220   a  is perpendicular to the first central elevation axis  1220   b.    
      The first fixed magnetic member  1230  is connected to the base  1205  and disposed in the coil  1220 . The first fixed magnetic member  1230  has a first central magnetizing axis  1230   a  and a second central elevation axis  1230   b . Specifically, the first central magnetizing axis  1230   a  is perpendicular to the second central elevation axis  1230   b  and aligned with the second central axis  1220   a  of the coil  1220 , and the second central elevation axis  1230   b  is separated from the first central elevation axis  1220   b  of the coil  1220 .  
      The second fixed magnetic member  1240  is connected to the magnetic-permeable member  1245 , disposed in the coil  1220  and separated from the first fixed magnetic member  1230  by a predetermined distance D. Similarly, the second fixed magnetic member  1240  has a second central magnetizing axis  1240   a  and a third central elevation axis  1240   b . The second central magnetizing axis  1240   a  is perpendicular to the third central elevation axis  1240   b  and aligned with the second central axis  1220   a  of the coil  1220 . The third central elevation axis  1240   b  is separated from the first central elevation axis  1220   b  of the coil  1220 . Specifically, the first central elevation axis  1220   b  is between the second central elevation axis  1230   b  and the third central elevation axis  1240   b . Namely, no matter how the coil  1220  moves, the first central elevation axis  1220   b  thereof is between the second central elevation axis  1230   b  of the first fixed magnetic member  1230  and the third central elevation axis  1240   b  of the second fixed magnetic member  1240 . Moreover, the first fixed magnetic member  1230  and second fixed magnetic member  1240  may be magnets, with two opposite polarities (N and S polarities) varying along the first central magnetizing axis  1230   a  and second central magnetizing axis  1240   a . Specifically, as shown in  FIG. 12 , the first fixed magnetic member  1230  and second fixed magnetic member  1240  oppose each other with the same magnetic pole.  
      The magnetic-permeable member  1245  is disposed between the first fixed magnetic member  1230  and the second fixed magnetic member  1240 , reducing repulsion there between. Moreover, the magnetic-permeable member  1245  can effectively guide magnetic lines from the first fixed magnetic member  1230  and second fixed magnetic member  1240  into the coil  1220 .  
      The lens housing  1250  is connected to the coil  1220  and carries a lens (not shown). Similarly, connection between the lens housing  1250  and the coil  1220  is not limited to the configuration shown in  FIG. 12 .  
      The position sensing member  1260  is connected to the coil  1220 , detecting the moving position or movement thereof. The position sensing member  1260  may be a Hall sensor, a reluctance sensor, or a photo interrupter. The magnetic member  1270  is connected to the base  1205 . The metal plate  1280  is selectively connected to the position sensing member  1260 . The position sensing member  1260  is disposed between the metal plate  1280  and the magnetic member  1270 . The magnetic member  1270  opposes the metal plate  1280  and may be a magnet.  
      If a Hall sensor, the position sensing member  1260  can be selectively disposed in the coil  1220  and oppose the first fixed magnetic member  1230  and/or the second fixed magnetic member  1240 , detecting changes in magnetic flux density and/or polarity of the magnetic field produced by the first fixed magnetic member  1230  and/or second fixed magnetic member  1240  and/or magnetic member  1270 . The moving position of the coil  1220  can thus be obtained.  
      The following description is directed to operation of the optical device  1200 .  
      When the coil  1220  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  1230  and second fixed magnetic member  1240 , moving the coil  1220  and lens housing  1250  along the first central axis  1210   a  of the guide bar  1210 . The lens carried by the lens housing  1250  can thus perform focus and zoom operations. Additionally, by detection of the position sensing member  1260 , the coil  1220  does not move to two ineffective positions, in which the first central elevation axis  1220   b  thereof coincides with the second central elevation axis  1230   b  of the first fixed magnetic member  1230  and third central elevation axis  1240   b  of the second fixed magnetic member  1240 .  
      Similarly, when moving to a specific position (the lens in the lens housing  1250  reaches a focus position), the coil  1220  and lens housing  1250  are fixed to the guide bar  1210  by attraction between the magnetic member  1270  and the metal plate  1280 . At this point, no holding current is required to fix the coil  1220  and lens housing  1250 , thus reducing power consumption of the optical device  1200 .  
      Moreover, the predetermined distance D between the first fixed magnetic member  1230  and the second fixed magnetic member  1240  can be adjusted. Specifically, when the predetermined distance D is relatively small, the coil  1220  receives relatively high strength magnetic fields or magnetic flux density from the first fixed magnetic member  1230  and second fixed magnetic member  1240 , thus increasing moving power. When the predetermined distance D, however, is relatively large, the distance between the second central elevation axis  1230   b  and the third central elevation axis  1240   b  is relatively large, thus increasing the moving distance or range of the coil  1220 .  
     Thirteenth Embodiment  
      Referring to  FIG. 13 , the optical device  1300  also employs the solenoid principle and comprises a base  1305 , a guide bar  1310 , a coil  1320 , a first magnetic member  1330 , a second magnetic member  1340 , a magnetic-permeable member  1345 , and a lens housing  1350 .  
      As shown in  FIG. 13 , the guide bar  1310  is connected to the base  1305  and has a first central axis  1310   a  in an optical axis direction of the optical device  1300 . Namely, the first central axis  1310   a  is parallel to the optical axis direction of the optical device  1300 .  
      The coil  1320  is disposed on the base  1305  has a second central axis  1320   a  in the optical axis direction and a first central elevation axis  1320   b . Specifically, the second central axis  1320   a  is perpendicular to the first central elevation axis  1320   b.    
      The lens housing  1350  slides on the guide bar  1310  and carries a lens (not shown).  
      The first magnetic member  1330  is connected to the lens housing  1350  and disposed in the coil  1320 . The first magnetic member  1330  has a first central magnetizing axis  1330   a  and a second central elevation axis  1330   b . Specifically, the first central magnetizing axis  1330   a  is perpendicular to the second central elevation axis  1330   b  and aligned with the second central axis  1320   a  of the coil  1320 , and the second central elevation axis  1330   b  is separated from the first central elevation axis  1320   b  of the coil  1320 .  
      The second magnetic member  1340  is connected to the magnetic-permeable member  1345 , disposed in the coil  1320  and separated from the first magnetic member  1330  by a predetermined distance D. The second magnetic member  1340  has a second central magnetizing axis  1340   a  and a third central elevation axis  1340   b . The second central magnetizing axis  1340   a  is perpendicular to the third central elevation axis  1340   b  and aligned with the second central axis  1320   a  of the coil  1320 . The third central elevation axis  1340   b  is separated from the first central elevation axis  1320   b  of the coil  1320 . Specifically, the first central elevation axis  1320   b  is between the second central elevation axis  1330   b  and the third central elevation axis  1340   b . Namely, no matter how the first magnetic member  1330  and second magnetic member  1340  move, the first central elevation axis  1320   b  of the coil  1320  is between the second central elevation axis  1330   b  of the first magnetic member  1330  and the third central elevation axis  1340   b  of the second magnetic member  1340 . Moreover, the first magnetic member  1330  and second magnetic member  1340  may be magnets, with two opposite polarities (N and S polarities) varying along the first central magnetizing axis  1330   a  and second central magnetizing axis  1340   a . Specifically, as shown in  FIG. 13 , the first magnetic member  1330  and second magnetic member  1340  oppose each other with the same magnetic pole.  
      The magnetic-permeable member  1345  is disposed between the first magnetic member  1330  and the second magnetic member  1340 , reducing repulsion there between. Moreover, the magnetic-permeable member  1345  can effectively guide magnetic lines from the first magnetic member  1330  and second magnetic member  1340  into the coil  1320 .  
      The following description is directed to operation of the optical device  1300 .  
      When the coil  1320  is energized by application of a current, a magnetic force is generated by interaction between the current and magnetic fields provided by the first magnetic member  1330  and second magnetic member  1340 , moving the first magnetic member  1330 , second magnetic member  1340 , lens housing  1350  along the first central axis  1310   a  of the guide bar  1310 . The lens carried by the lens housing  1350  can thus perform focus and zoom operations.  
      Moreover, the predetermined distance D between the first magnetic member  1330  and the second magnetic member  1340  can be adjusted. Specifically, when the predetermined distance D is relatively small, the coil  1320  receives relatively high strength magnetic fields or magnetic flux density from the first magnetic member  1330  and second magnetic member  1340 , thus increasing moving power of the first magnetic member  1330  and second magnetic member  1340 . When the predetermined distance D, however, is relatively large, the distance between the second central elevation axis  1330   b  and the third central elevation axis  1340   b  is relatively large, thus increasing the moving distance or range of the first magnetic member  1330  and second magnetic member  1340 .  
      In conclusion, as the disclosed optical device enables focusing movement of the lens by way of attraction or repulsion of two magnetic fields, the electricity required to maintain the lens in the target focus position is reduced. Thus, the disclosed optical device provides reduced power consumption. Moreover, the disclosed optical device enables the lens to achieve rapid focusing movement and precise positioning.  
      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.