Abstract:
A multi-stage lens driving device comprises a lens holder, a lens mounted on the lens holder, a carriage carrying the lens holder in a movable manner, at least one magnet coupled to the lens holder, at least one coil disposed on the carriage and corresponding to the magnet, and at least one yoke disposed at a predefined position of the carriage. Through the magnetic field produced by the magnet and the current action in the coil, the force generated thereof can push the lens holder to move toward a desired position, thereby achieving the effect of focusing or zooming. In addition, through the attraction between the yoke and the magnet on the lens holder, the lens holder may be secured to the predefined position. That is, the lens is firmly secured even when the coil current is shut off, thereby achieving the goal of saving power consumption.

Description:
BACKGROUND OF INVENTION 
   1. Field of the Invention 
   The present invention relates to a multi-stage lens driving device, more particularly a miniature lens driving device that uses electromagnetic driving apparatus as power source to drive a miniature lens to engage in multi-stage position switch. 
   2. Description of the Prior Art 
   As shown in  FIG. 1 , a standard camera  1  comprises a lens set  11  and a sensor  12 . The lens set  11  forms an image on sensor  12  by refracting the light rays from an object. If the distance between lens set  11  and sensor  12  is fixed (i.e. a fixed lens), the lens can only show clearly objects at its hyperfocal distance of 2-3 meters away. For the camera to shoot objects clearly at varying distances (for example at a close distance), a lens driving device is required to move the lens set, thereby adjusting the distance between lens set and sensor and achieving focusing. 
   When the lens set offers the zoom function, the multiple lenses in the lens set must be displaced in coordination with the change of zoom power. Thus the lens module is typically designed with a driving apparatus to displace the lenses. 
   The focusing or zooming mechanism for a conventional multi-stage camera lens moves the lens “manually”, which can be inconvenient at times. The present invention improves the aforesaid drawback by changing the lens driving method from manual to electromagnetic, and at the same time, reduce the size of lens driving device and simplify the design of lens module, hence lowering production costs and improving the assembly process. Such miniature lens driving device will be suitable for the camera module in cellular phone, notebook computer and PDA. 
   U.S. Pat. Nos. 5,150,260, 6,392,827, 5,220,461 and 5,471,100 have disclosed several techniques for driving lens, which however do not bear identical nor similar technical features as the ones disclosed in the present invention. 
   SUMMARY OF INVENTION 
   The primary object of the present invention is to provide a miniature multi-stage lens driving device, which offers the advantages of smaller size, simpler mechanism and less power consumption and drives lens (lens unit) electromagnetically to achieve the effect of multi-stage focusing or zooming, thereby improving the function of miniature camera module. 
   Another object of the present invention is to provide a multi-stage lens driving device, which is able to secure the lens holder to a specific position by the attraction between the magnetic conductors (yokes) disposed on carriage and base and the magnetic element (permanent magnet) disposed on lens holder. As such, the lens is firmly secured even with the coil current shut off to save power consumption. 
   To achieve the aforesaid objects, a preferred embodiment of the multi-stage lens driving device according to the invention comprises a lens holder, a lens mounted on the lens holder, a carriage carrying the lens holder by means of mutual displacement, at least a magnet connected to the lens holder, at least a coil provided on the carriage and corresponding to the magnet, and at least two yokes disposed respectively at a predetermined location on the anterior and posterior sides of lens holder. Through the magnetic field produced by the magnet and the electric current action in the coil, the force generated thereof can push the lens holder to bring the lens to a desired position, thereby achieving the effect of focusing or zooming. In addition, through the attraction between the yokes at the anterior and posterior ends of lens holder and the magnet on the lens holder, the lens holder may be secured to a specific position. That is, the lens is firmly secured with the coil current shut off, thereby achieving the goal of saving power consumption. 
   In one preferred embodiment of the present invention, two cone-shape inclined planes are formed at the anterior and posterior periphery of holder along axial direction. In addition, two beveled surfaces are disposed respectively on the carriage and corresponding respectively to the two cone-shape inclined planes. When the holder is driven to move along axial direction, the beveled surfaces disposed on carriage can prop against the cone-shape inclined planes on holder to achieve the positioning effect. Furthermore, the support of the cone-shape inclined planes on holder and the beveled surfaces on carriage for each other allows the center line of lens to overlap the axial direction so lens will not shift. 
   In one preferred embodiment of the present invention, the magnet is produced by polarizing a lodestone such that the upper and lower portions of the lodestone on the same side have opposite polarity, and as such, the upper and lower portions of magnet on the side facing the carriage have opposite polarity. 
   In one preferred embodiment of the present invention, the coils are flat coils further comprising a substrate made of dielectric material and a metal coil printed thereon. The substrate is a rectangular sheet and the metal coil is spirally wound on a surface of substrate in the shape of a rectangular vortex. 
   In another preferred embodiment of the present invention, the coil comprises at least two inductive coils wound respectively around the outer periphery of carriage and corresponding respectively to the upper and lower portions of magnet. At the same time, the currents applied to the two inductive coils are in opposite direction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For further understanding the objects, the characteristics, and the functions of the structures of the present invention, a detailed description matched with corresponding drawings are presented as follows. 
       FIG. 1  is a diagram showing the focusing principle of conventional lens. 
       FIG. 2  is an external view of the assembled multi-stage lens driving device according to a first embodiment of the invention. 
       FIG. 3  is an exploded front side view of the multi-stage lens driving device according to the first embodiment of the invention. 
       FIG. 4  is an exploded back side view of the multi-stage lens driving device according to the first embodiment of the invention. 
       FIG. 5  is a diagram showing a preferred embodiment of the magnet in the multi-stage lens driving device according to the invention. 
       FIG. 6  is a diagram showing the first preferred embodiment of the coil in the multi-stage lens driving device according to the invention. 
       FIG. 7  is a diagram showing the relative positions of yoke, coil and magnet in the multi-stage lens driving device according to the first embodiment of the invention. 
       FIG. 8  is a diagram of the relative positions shown in  FIG. 7  from a side view. 
       FIG. 9  is the A-A sectional view of the multi-stage lens driving device shown in  FIG. 2  with the lens at the first position. 
       FIG. 10  is the A-A sectional view of the multi-stage lens driving device shown in  FIG. 2  with the lens at a second position. 
       FIG. 11  is diagram showing the second preferred embodiment of the coil in the multi-stage lens driving device according to the invention. 
       FIG. 12  is diagram showing a third preferred embodiment of the coil in the multi-stage lens driving device according to the invention. 
       FIG. 13  is diagram showing the third preferred embodiment of the magnet in the multi-stage lens driving device according to the invention. 
       FIG. 14  is an external view of the assembled multi-stage lens driving device according to a fourth embodiment of the invention. 
       FIG. 15  is an exploded front side view of the multi-stage lens driving device according to the fourth embodiment of the invention. 
       FIG. 16  is a diagram showing the relative positions of yoke and magnet in the multi-stage lens driving device according to the fourth embodiment of the invention. 
       FIG. 17  is a diagram of the relative positions shown in  FIG. 16  from a side view. 
       FIG. 18  is the B-B sectional view of the multi-stage lens driving device shown in  FIG. 14  with the lens at a first position. 
       FIG. 19  is the B-B sectional view of the multi-stage lens driving device shown in  FIG. 14  with the lens at a second position. 
       FIG. 20  is the B-B sectional view of the multi-stage lens driving device shown in  FIG. 14  with the lens at a third position. 
       FIG. 21  is an exploded front side view of the multi-stage lens driving device according to the fifth embodiment of the invention. 
   

   DETAILED DESCRIPTION 
     FIGS. 2˜10  disclose a first preferred embodiment of the multi-stage lens driving device according to the invention.  FIG. 2  is an external view of the assembled multi-stage lens driving device according to a first embodiment of the invention.  FIG. 3  is an exploded front side view of the multi-stage lens driving device according to a first embodiment of the invention.  FIG. 4  is an exploded back side view of the multi-stage lens driving device according to a first embodiment of the invention.  FIG. 5  is a diagram showing a preferred embodiment of the magnet in the multi-stage lens driving device according to the invention.  FIG. 6  is a diagram showing a first preferred embodiment of the coil in the multi-stage lens driving device according to the invention.  FIG. 7  is a diagram showing the relative positions of yoke, coil and magnet in the multi-stage lens driving device according to the invention from an anterior view.  FIG. 8  is a diagram of the relative positions shown in  FIG. 7  from a side view.  FIG. 9  is the A-A sectional view of the multi-stage lens driving device shown in  FIG. 2  with the lens at a first position.  FIG. 10  is the A-A sectional view of the multi-stage lens driving device shown in  FIG. 2  with the lens at a second position. 
   As shown in  FIGS. 2˜4 , the multi-stage lens driving device according to a first preferred embodiment of the invention comprises: a lens  90 , a lens holder  20 , a carriage  30 , a base  40 , an electromagnetic driving mechanism, and a positioning mechanism. 
   The lens  90  is defined with an axial direction  91 , along which the lens gathers light. In the first preferred embodiment of the invention, the lens  90  can be a lens module composed of monofocal lenses without zoom function or a lens  90  in a zoom lens unit. 
   The lens holder  20  has a hollow annular structure having an outer ring surface  21 . The outer edge contour  22  of the axial projection  91  of holder  20  exhibits a polygonal structure. The holder  20  has an axial through-hole  23 . Corresponding threads  240 ,  92  are disposed between the through-hole  23  and lens  90  to engage, hold and secure lens  90  in the through-hole  23  of holder  20 . 
   The holder  20  can become disposed inside the carriage  30  by means of relative movement that enables the holder  20  to carry out linear displacement inside the carriage  30  along axial direction  91 . In the first preferred embodiment, the carriage  30  has a hollow structure and a polygonal inner edge contour  31  of its axial projection  91  corresponds exactly to the polygonal outer edge contour  22  of holder  20 . When holder  20  is held inside the carriage  30 , the matching of their inner and outer polygonal contours  31 ,  22  form essentially a linear guiding mechanism that allows the holder  20  to engage in linear movement therein without turning. 
   The electromagnetic driving mechanism is linked to the holder  20  to drive the holder  20  to engage in anterior-posterior linear movement along axial direction  91  in the carriage  30 . In the first preferred embodiment, the electromagnetic driving mechanism comprises: at least a coil  41 ,  42 ,  43 ,  44  and at least a magnet  45 ,  46 ,  47 ,  48 . In this embodiment, the numbers of both coil and magnets are four, but other numbers are acceptable. The magnets  45 ,  46 ,  47 ,  48  are spaced in roughly equal distance apart and mounted on the outer ring surface  21  of holder  20 . The coils  41 ,  42 ,  43 ,  44  are furnished on the carriage  30  and correspond (without direct contact) respectively to the positions of magnets  45 ,  46 ,  47 ,  48 . By applying current of predefined direction to coils  41 ,  42 ,  43 ,  44 , predetermined interacting force is produced between the coils and magnets  45 ,  46 ,  47 ,  48  which can push the holder  20  to move. 
   As shown in  FIG. 5 , the magnets  45 ,  46 ,  47 ,  48  are permanent magnets. In the example of magnet  45 , it is produced by polarizing a lodestone such that the upper and lower portions  451 ,  452  of the lodestone on the same side have the opposite polarity. For example, the upper portion  451  on the side surface of magnet  45  facing the carriage  30  is N pole, while its lower portion  452  is S pole. In contrast, the upper portion  451  on the side surface of magnet  45  adjoining the outer ring surface  21  of holder  20  is S pole, while its lower portion  452  is N pole. 
   In another embodiment, two permanent magnets  451 ,  452  are stacked together to form a magnet set where both magnets have two opposing poles. In the magnets  451 ,  452 , one pole (e.g. S pole of magnet  451  and N pole of magnet  452 ) is on the side adjoining outer ring surface  21 , while the other pole (e.g. N pole of magnet  451  and S pole of magnet  452 ) is situated on the side facing the carriage  30 . The poles of stacked magnets  451 ,  452  on the side facing the carriage  30  (e.g. N pole of magnet  451  and S pole of magnet  452 ) are opposite to each other. 
   As shown in  FIG. 6 , the coils  41 ,  42 ,  43 ,  44  in the first preferred embodiment are all flat coils. In the example of coil  41 , it further comprises: a substrate  411  made of dielectric material and a metal coil  412  printed on the substrate. The substrate  411  is a rectangular sheet made of dielectric material. Its size roughly corresponds to magnet  45  with opposing poles at upper and lower portions  451 ,  452 . The metal coil  412  is spirally wound on a surface of substrate  411  in the shape of a rectangular vortex. When a current (direct current) of predefined direction is applied to flat coil  41 , the current direction at upper half of coil  41  is exactly opposite to that at lower half of coil  41 . Such arrangement coordinates with the property of magnet  45  having opposite polarity at its upper and lower portions  451 ,  452 . As the upper and lower halves of flat coil  41  provides same-direction thrust to upper and lower portions  451 ,  452  of magnet  45 , they provide essentially nearly two times the thrust force, thereby greatly enhancing the driving performance. 
   The positioning mechanism is mounted on carriage  30  and base  50  to guide the holder  20  to either a first position (anterior position) or a second position (posterior position) when it displaces in axial direction  91 . As shown in  FIGS. 3 &amp; 4 , the positioning mechanism in the first preferred embodiment of the invention comprises: at least two magnetic conductors  61 ,  62  respectively near to two cone-shape inclined planes  24 ,  25  at the anterior and posterior periphery of holder  20  in axial direction, and two beveled surfaces  32 ,  51  corresponding respectively to the two cone-shape inclined planes  24 ,  25 . 
   Referring to  FIGS. 7 &amp; 8  together with  3  &amp;  4 , the two magnetic conductors  61 ,  62  are flat ring structures made of yoke. One of the magnetic conductors  61  (yoke) is mounted on the inner periphery at the anterior side of carriage  30  facing the holder  20  such that the magnetic conductor  61  (yoke) is essentially situated at the anterior end of holder  20  (the first position) along axial direction  91 . The other magnetic conductor  62  (yoke) is mounted on the inner periphery of base  50  facing the holder  20 , i.e. the posterior end of holder  20  along axial direction  91  (the second position). As shown in  FIG. 9  together with  FIG. 8 , when holder  20  is driven by the electromagnetic driving mechanism (including magnets  45 ˜ 48  and coils  41 ˜ 44 ) to move to a place near the magnetic conductor  61  at anterior end, the magnets  45 ˜ 48  disposed on the holder  20  will be attracted and positioned at the first position where magnetic conductor  61  at anterior end of holder  20  is located. As shown in  FIG. 10  together with  FIG. 8 , when current of opposite direction is applied to coils  41 ˜ 44 , the holder  20  is driven by inverse thrust force and moves to a place near the magnetic conductor  62  at the posterior end. As magnets  45 ˜ 48  are attracted by magnetic conductor  62 , the holder  20  is positioned at the second position at posterior end. As such, multi-stage switching of lens position is achieved. In addition, through the attraction between magnetic conductors  61 ,  62  and magnets  45 ˜ 48 , the lens  90  is firmly secured to its place even with the current applied to coils  41 ˜ 44  shut off, thereby saving the power consumption. 
   As shown in  FIGS. 9 &amp; 10  and together with  FIGS. 3 &amp; 4 , with two cone-shape inclined planes  24 ,  25  provided at the anterior and posterior periphery of holder  20  along axial direction  91  and two beveled surfaces  32 ,  51  disposed respectively on carriage  30  and base  50 , and corresponding respectively to the two cone-shape inclined planes  24 ,  25 , when holder  20  is driven to move along axial direction  91  to first position or second position, the beveled surfaces  32 ,  51  disposed on carriage  30  and base  50  can prop against the cone-shape inclined planes  24 ,  25  on holder  20  to achieve the positioning effect. In addition, the support of the cone-shape inclined planes  24 ,  25  on holder  20  and the beveled surfaces  32 ,  51  for each other allows the center line of lens  90  to overlap the axial direction  91  so lens  90  will not shift. 
   Referring to  FIG. 11  which shows a second preferred embodiment of the coil in the multi-stage lens driving device according to the invention, the coil comprises at least two inductive coils  71 ,  72  which are wound respectively around the outer periphery of carriage  30   a  and correspond to the upper and lower portions  451 ,  452  of magnet  45 . At the same time, the currents applied to inductive coils  71 ,  72  are in opposite direction (the same effect may be achieved by winding the inductive coils  71 ,  72  in opposite direction). As such, it coordinates with the property of magnet  45 ˜ 48  having opposite polarity at its upper and lower portions  451 ,  452 . As the inductive coils  71 ,  72  provide same-direction thrust to upper and lower portions  451 ,  452  of magnet  45 ˜ 48 , they provide essentially nearly two times the thrust force, thereby greatly enhancing the driving performance. 
     FIG. 12  and  FIG. 13  show respectively the diagram of a third preferred embodiment of the coil and the magnet in the multi-stage lens driving device according to the invention. As shown, the coil is composed of only one inductive coil  71   b  which is wound around the outer periphery of carriage  30   b  in a predetermined direction. The magnet  45   b  is a monopole lodestone with a polarity (S pole in  FIG. 13 ) on the side surface facing the carriage  30   b  and opposite to the polarity (N pole in  FIG. 13 ) on the side surface adjoining the outer ring surface (not numbered in the figure) of holder  20 . Such arrangement still achieves the effect of driving the holder and causing it to displace. 
     FIG. 14  and  FIG. 15  show respectively an assembled external view and an exploded front side view of the multi-stage lens driving device according to the fourth embodiment of the invention. Because most components of the fourth embodiment shown in  FIG. 14  and  FIG. 15  are substantially the same or similar with the ones shown in  FIG. 2 , therefore, same or similar components will not be described in the following description. 
   Referring to  FIG. 14  and  FIG. 15 , and together with  FIG. 16  and  FIG. 17 , the difference between this fourth embodiment and the aforementioned first embodiment is that, in addition to the magnetic conductors  61 ,  62  respectively disposed at the front and rear sides of the holder  20 , the lens driving device of this fourth embodiment further comprises a frame-typed magnetic conductor  63  located at the middle between the magnetic conductors  61 ,  62 . As shown in  FIGS. 15 to 17 , one of the magnetic conductors  61  (yoke) is mounted on the inner periphery at the anterior side of carriage  30   c  facing the holder  20  such that the magnetic conductor  61  (yoke) is essentially situated at the anterior side of holder  20  (the first position) along axial direction  91 . Another magnetic conductor  62  (yoke) is mounted on the inner periphery of base  50   c  facing the holder  20 , i.e. the posterior side of holder  20  along axial direction  91  (the second position). The newly added frame-typed magnetic conductor  63  is mounted between the positioning recesses  33 ,  53  respectively formed on the contact surfaces of carriage  30   c  and base  50   c . The frame-typed magnetic conductor  63  substantially surrounds (but doesn&#39;t contact) the magnets  45 ˜ 48  and is essentially situated at the middle of holder  20  (the third position) along axial direction  91 . 
   As shown in  FIG. 18  together with  FIG. 17 , when holder  20  is driven by the electromagnetic driving mechanism (including magnets  45 ˜ 48  and coils  71  and  72 ) to move to a place near the magnetic conductor  61  at anterior end, the magnets  45 ˜ 48  disposed on the holder  20  will be attracted and positioned at the first position where magnetic conductor  61  at anterior end of holder  20  is located. 
   As shown in  FIG. 19  together with  FIG. 17 , when current of opposite direction is applied to coils  71  and  72 , the holder  20  is driven by inverse thrust force and moves to a place near the magnetic conductor  62  at the posterior end. As magnets  45 ˜ 48  are attracted by magnetic conductor  62 , the holder  20  is positioned at the second position at posterior end. 
   As shown in  FIG. 20  together with  FIG. 17 , when directions of current applied to coils  71  and  72  are opposite to each other, the coil  71  will generate a force pushing the holder  20  backward (downward), while the other coil  72  will generate another force to push the holder  20  forward (upward). As a result, the magnets  45 ˜ 48  will be attracted by frame-typed magnetic conductor  63  located at the middle between the other two magnetic conductors  61  and  62 , so as to increase an additional switching position. As such, “three-stage” switching of lens position is achieved. In addition, through the attraction between magnetic conductors  61 ,  62  and  63  and magnets  45 ˜ 48 , the lens  90  is firmly secured to its place even with the current applied to coils  71  and  72  shut off, thereby saving the power consumption. 
     FIG. 21  shows an exploded front side view of the multi-stage lens driving device according to the fifth embodiment of the invention. Because most components of the fifth embodiment shown in  FIG. 21  are substantially the same with the ones shown in  FIG. 15 , therefore, same or similar components will not be described in the following description. 
   Referring to  FIG. 21 , the difference between this fifth embodiment and the aforementioned fourth embodiment is that, there is only one magnetic conductor  63  furnished, while the other two magnetic conductors are omitted in this fifth embodiment. The magnetic conductor  63  (yoke) is still mounted between the positioning recesses  33 ,  53  respectively formed on the contact surfaces of carriage  30   c  and base  50   c , and thus can still provides “three-stage” switching of lens position. However, when the current applied to coils  71  and  72  shut off, the holder will be attracted by the magnetic conductor  63  and be moved to the middle position along the axial direction  91 . 
   The fifth embodiment shown in  FIG. 21  discloses a multi-stage lens driving device of the present invention that is furnished with “single” magnetic conductor  63 . However, it is notable that, such “single” magnetic. conductor can also be located at either the anterior side of holder  20  (same location as the magnetic conductor  61 ) or the posterior side of holder  20  (same location as the magnetic conductor  62 ). 
   It should be noted that the above described embodiments are not to be construed as limiting the applicable scope of the invention, but instead the protective scope of the invention should be defined by the technical spirit of the appended claims along with their full scope of equivalents. In other words, equivalents and modifications made based on the appended claims still accords with the intention of the invention and dose not depart from the spirit and scope of the invention. Thus, all should be regarded as further implementions of the invention.