Abstract:
An image blur correction device includes a base, a seat disposed on the base, an image detecting unit disposed on the seat, at least one coil, and at least one magnet. The coil is disposed on the seat or the base, has a first length in a first direction and a second length in a second direction, and has a hollow portion. The first direction is perpendicular to the second direction. The magnet is disposed on the seat or the base and opposite to the coil, and has a third length in the first direction corresponding to the first length and a fourth length in the second direction corresponding to the second length. The coil moves relative to the magnet and has a maximum moving distance so that the seat moves relative to the base. A width of the hollow portion equals to or exceeds twice the maximum moving distance.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of Taiwan Patent Application No. 97120578, filed on Jun. 3, 2008, the entirety of which is incorporated by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an image blur correction device, and in particular relates to an image blur correction device with a movable optical element to prevent a blur. 
         [0004]    2. Description of the Related Art 
         [0005]    Referring to  FIG. 1 , U.S. Pat. No. 5,266,988 discloses an image shake suppressing device for a camera. The image shake suppressing device is mounted in a lens. When the camera is used, an angular velocity meter measures the angular velocity of the shaking camera and provides the measured data to a circuit which calculates the data for a driving part to move the lens in a direction of a vertical optical axis, thereby compensating or suppressing blurring due to vibration of the camera. 
         [0006]    Because the lens, however, is moved along a vertical optical axis, the ambient light and MTF value thereof are reduced. Thus, the compensation method has limited compensation effect and may reduce image quality. 
         [0007]    Referring to  FIGS. 2A and 2B , Japan patent No. 3551174 discloses a moving mechanism. The moving mechanism is applicable to any lens and employs piezoelectric elements to drive an image detecting unit, such as a CCD, in a vertical direction, such that blur can be compensated or suppressed. 
         [0008]    The piezoelectric elements must be driven by voltage to move the CCD. As the CCD, is heavier than a single lens, a large piezoelectric element is needed to avoid deterioration of the image quality. Thus, the volume of the camera is increased. 
         [0009]    U.S. Pat. No. 6,327,433 discloses an assembly of a coil and two magnets, moving a compensation lens to compensate for hand shake. Poles of the two magnets are disposed face to face to from a closed magnetic circuit and the coil is disposed between the two magnets. During operation, the coil can be moved by a force generated from a magnetic flux of the magnet circuit and the current passing through the coil. In this patent, however, the movement of the coil is not limited. Thus, during movement of the coil, a part of the coil may not face the magnet, so that magnetic flux passing through the coil is reduced, and the movement of the coil and the compensation lens can not be accurately controlled. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    An image blur correction device of the invention provides a predetermined relationship between a width of a coil, a width of a magnet, and a maximum moving distance. When the coil is moved relative to the magnet, a magnetic flux passing though the coil is held at a maximum level to accurately control the motion of the image detecting device for minimizing or preventing a blur. 
         [0011]    An embodiment of an image blur correction device of the invention comprises a base, a seat, an image detecting unit, at least one coil, and at least one magnet. The seat is disposed on the base. The image detecting unit is disposed on the seat. The coil is disposed on the seat or the base, has a first length in a first direction and a second length in a second direction, and has a hollow portion, wherein the first direction is perpendicular to the second direction. The magnet is disposed on the seat or the base and opposite to the coil, and has a third length in the first direction corresponding to the first length and a fourth length in the second direction corresponding to the second length, wherein the coil moves relative to the magnet and has a maximum moving distance so that the seat moves relative to the base. A width of the hollow portion is equal to or greater than twice the maximum moving distance. 
         [0012]    In the foregoing embodiment of the invention, the first length is smaller than the third length and a difference between the first length and the third length is greater than or equal to the maximum moving distance. 
         [0013]    In the foregoing embodiment of the invention, the second length is smaller than the fourth length and a difference between the second length and the fourth length is greater than or equal to the maximum moving distance. 
         [0014]    In the foregoing embodiment of the invention, the magnet comprises an N pole and an S pole, disposed in the first direction. 
         [0015]    The foregoing embodiment of the invention further comprises a Hall element disposed on either the base or the seat and adjacent to the coil, wherein a magnetic force is generated between the coil and the magnet by providing a voltage to the coil, moving the seat in the first direction. 
         [0016]    The foregoing embodiment of the invention further comprises a guide member by which the seat is joined to the base, and movable relative to the base in the first direction. The guide member comprises a plurality of holding portions and a pair of shafts. The holding portions are disposed on the base and the seat, respectively. The parallel shafts are held by the holding portions, whereby the seat is joined to the base, and movably along the shaft. 
         [0017]    In the foregoing embodiment of the invention, when the image detecting module is still, two halves of the Hall element are located on the N pole and the S pole of the magnet, respectively. 
         [0018]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0020]      FIG. 1  depicts an image shake suppressing device disclosed in U.S. Pat. No. 5,266,988; 
           [0021]      FIGS. 2A and 2B  depict a moving mechanism disclosed in Japan Patent No. 3551174; 
           [0022]      FIG. 3  is a perspective view of an embodiment of an image detecting module of the invention; 
           [0023]      FIG. 4  is a rear view of a base of the image detecting module; 
           [0024]      FIG. 5  is a perspective view of a seat with a movable plate of the embodiment of the invention; 
           [0025]      FIG. 6  is a rear view of a seat with a movable plate of the embodiment of the invention; 
           [0026]      FIG. 7A  is an assembly drawing of a first coil and a first magnet and depicts the first coil moving in a positive Y direction; 
           [0027]      FIG. 7B  is an assembly drawing of a first coil and a first magnet and depicts the centerlines of the first coil and the first magnet; 
           [0028]      FIG. 7C  is an assembly drawing of a first coil and a first magnet and depicts the first coil moving in a negative Y direction; 
           [0029]      FIGS. 8A ,  8 B, and  8 C are side views of  FIGS. 7A ,  7 B, and  7 C. 
           [0030]      FIGS. 9A ,  9 B, and  9 C are top views of  FIGS. 7A ,  7 B, and  7 C. 
           [0031]      FIG. 10  is a schematic view of a camera having the image detecting module of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    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. 
         [0033]    In the following description, the orientations, such as first direction X, second direction Y, or third direction Z, are based on the coordinates in each figure, and the first direction X, second direction Y, and the third direction Z are orthogonal to each other. 
         [0034]    Referring to  FIG. 3 , an image detecting module of an embodiment of the invention is applicable in cameras for suppressing and compensating a blur arising from hand shake. The image detecting module comprises a base  20  with a hollow portion  29 , a seat  30  disposed in the hollow portion  29 , a movable plate  40  detachable disposed in the seat  30 , and an image detecting unit  50  (such as a CCD) disposed on the movable plate  40 . The sensing surface of the image detecting unit  50  faces opposite to the third direction Z. 
         [0035]    Referring to  FIG. 4 , the base  20  comprises a pair of first magnets  21  and  22 , a pair of second magnets  23  and  24  and a pair of parallel first shafts  25  and  26 . The first magnets  21  and  22  are disposed in parallel on two sides of the hollow portion  29 . The N pole and S pole of the first magnet  21  are extended in the first direction X, and the N pole and S pole of the first magnet  22  are also extended in the first direction X. The second magnets  23  and  24  are disposed in parallel on two sides of the hollow portions  29 . The N pole and the S pole of the second magnet  23  are extended in the second direction Y, and the N pole and the S pole of the other second magnet  24  are also extended in the second direction Y. In addition, N poles of the first magnet  21  and  22  face the hollow portion  29 , and the S poles of the second magnet  23  and  24  face the hollow portion  29 . 
         [0036]    Referring to  FIGS. 5 and 6 , the seat  30  has two wing portions  31   a  and  31   b , with a pair of first coils  32   a  and  32   b  and a first Hall element  44   a  disposed thereon. Specifically, the first coil  32   a  is disposed on the wing portion  31   a , the first Hall element  44   a  is also disposed on the wing portion  31   a  and adjacent to the first coil  32   a , and the other first coil  32   b  is disposed on the wing portion  31   b . The first coils  32   a  and  32   b  are substantially rectangular and their longitudinal sides are parallel. The movable plate  40  also has two wing portions  41   a  and  41   b . A pair of second coils  42   a  and  42   b  and a second Hall element  44   b  are disposed on the wing portions  41   a  and  41   b . Specifically, the second coil  42   a  is disposed on the wing portion  41   a , the second Hall element  44   b  is disposed on the wing portion  41   a  and adjacent to the second coil  42   a , and the other second coil  42   b  is also disposed on the wing portion  41   b . The second coils  42   a  and  42   b  are also substantially rectangular, and their longitudinal sides are parallel. A pair of first holding portions  35   a  and  35   b  is disposed on the seat  30  adjacent to the wing portion  41   a . The first holding portions  35   a  and  35   b  have holes  351   a  and  351   b , respectively. Also, a pair of first holding portions  35   c  and  35   d  is disposed on the seat  30  adjacent to another wing portion  41   b . The first holding portion  35   c  and  35   d  has holes  351   c  and  351   d.    
         [0037]    A pair of first shafts  25  and  26  is disposed in parallel. The shorter first shaft  25  is disposed on the side of the magnets  21  and  24 , while the longer first shaft  26  is disposed on the side of the magnet  23  away from the hollow portion  29 . In this embodiment, the longer first shaft  26  extends through the holes  351   c  and  351   d  and is held by the first holding portions  35   c  and  35   d  and is fixed to the holding portions  25   b  and  25   c . The shorter first shaft  25  extends through holes  351   a  and  351   b  and is fixed by the holding portion  25   a . The first shafts  25 ,  26  and the holding portions  25   a ,  25   b ,  25   c ,  35   a ,  35   b ,  35   c , and  35   d  constitute a first guide element  60  through which the seat  30  can be moved in the second direction Y. 
         [0038]    Referring to  FIGS. 5 and 6 , the seat  30  has a hollow portion  39 . The image detecting unit  50  is disposed in the hollow portion  30  on the movable plate  40 . The movable plate  40  has a circuit board  45  to which the image detecting unit  50  is electrically connected. A rectangular frame  46  is fixed to the circuit board  45  and surrounds the image detecting unit  50 . A pair of parallel frame walls  461  and  462  of the rectangular frame  46  have second holding portions  463   a ,  463   b ,  463   c  and  463   d , respectively. The second holding portions  463   a ,  463   b ,  463   c  and  463   d  have holes  4631   a ,  4631   b ,  4631   c  and  4631   d , respectively. A pair of second shafts  47  and  48  is parallel to the first direction X. One of the second shafts  47  extends through the holding portion  36   a  and  36   b  on the seat  30  and is inserted into holes  4631   a  and  4631   b  and fixed to the seat  30 . The other second shaft  48  extends through the holding portions  36   c  and  36   d  and holes  4631   c  and  4631   d , whereby the movable plate  40  is joined to the seat  30 . The second shafts  47 ,  48  and the holding portions  36   a ,  36   b ,  36   c ,  36   d ,  463   a ,  463   b ,  463   c , and  463   d  constitute a second guide element  70  through which a movable plate  40  can be moved in the first direction X. 
         [0039]      FIGS. 7A ,  7 B, and  7 C depict the first coil  32   a  and the first magnet  21 , wherein the assembly of the first coil  32   b  and the first magnet  22 , the assembly of the second coil  42   a  and the second magnet  23 , and the assembly of the second coil  42   b  and the second magnet  24  are similar to that of the first coil  32   a  and the first magnet  21 . Thus, only the assembly of the first coil  32   a  and the first magnet  21  is described. 
         [0040]      FIG. 7B  depicts the first coil  32   a  and the first magnet  21  with superimposed centerlines, and  FIGS. 7A and 7C  depict the first coil  31  moving in a positive Y direction and a negative Y direction, respectively. 
         [0041]      FIGS. 8A ,  8 B, and  8 C are side views of  FIGS. 7A ,  7 B, and  7 C.  FIGS. 9A ,  9 B, and  9 C are top views of  FIGS. 7A ,  7 B, and  7 C. 
         [0042]    The N pole and S pole of the first magnet  21  are adjoined. The first coil  32   a  has a hollow portion  312 , wherein a width of the hollow portion  312  is A. The first coil  32   a  has a first length B in the first direction X and a second length D in the second direction Y. The first magnet  21  has a third length C in the first direction X and a fourth length E in the second direction Y. 
         [0043]    Referring to  FIGS. 8A ,  8 B, and  8 C, “.” indicates the direction of the current out of the paper containing  FIG. 8A ,  8 B, or  8 C, and “x” indicates the direction of the current into the paper containing  FIG. 8A ,  8 B, or  8 C. When the first coil  32   a  is moved the maximum distance, the current passes in direction “.” through the part of the first coil  32   a , which is located in the magnetic field of the N pole of the first magnet  21  to generate an upward force, and the current passes in direction “x” through the part of the first coil  32   a , which is located in the magnetic field of the S pole of the first magnet  21  to generate an upward force, and thus the first coil  32   a  is moved upwardly. If F&gt;A/2, then the part of the first coil  32   a  having the current in direction “x” will enter the magnetic field of the N pole of the first magnet  21 , so that the first coil  32   a  generates a downward force to counteract the upward force f, thus affecting movement of the first coil  32   a . A downward moving status of the first coil  32  is similar to an upward moving status thereof. Thus, the maximum distance F of the first coil  32   a  of the invention is limited to be smaller than or equal to A/2, that is A≧2F. 
         [0044]    Referring to  9 A,  9 B, and  9 C, the second length D of the first coil  31  is smaller than the fourth length E of the first magnet  21 , and a difference between the second length D and the fourth length E is greater than or equal to a maximum moving distance F. 
         [0045]      FIG. 10  depicts a camera employing the image detecting unit of the invention. Referring to  FIGS. 3 and 10 , a camera  100  comprises a motion sensor  110 , such as an angular acceleration element or linear acceleration element. When the motion sensor  110  detects motion of the camera  100 , a PWM circuit  120  or a digital circuit provides a voltage signal to the first coils  32   a ,  32   b  and the second coils  42   a  and  42   b . The first coils  32   a ,  32   b  and the second coils  42   a ,  42   b  generate variable magnetic fields which interact with the first magnet  21 ,  22  and the second magnet  23 ,  24 , whereby the seat  30  moves in the second direction Y, the movable plate  40  moves in the first direction X, and the image detecting unit  50  moves in the first direction X and the second direction Y, correspondingly. Blurring is thereby minimized or prevented. 
         [0046]    When the camera  100  is still, the image detecting module is also still. At this time, two halves of the first Hall element  44   a  are located on the N pole and the S pole of the first magnet  21 , and two halves of the second Hall element  44   b  are located on the N pole and the S pole of the second magnet  23 . Thus, the first and second Hall elements  44   a  and  44   b  detect no magnetic field variation. When the camera  100  is shaken during operation, the first and second coils  42   a ,  42   b ,  43   a ,  43   b  interact with the first and second magnets  21 ,  22 ,  23  and  24  to move the seat  30  in the first direction X and the second direction Y. The Hall element  44   a  and  44   b  detects variation of the magnetic field to calculate the displacement and moving frequency of the seat  30 , whereby the voltage signal from the PWM circuit and the digital circuit is modified. 
         [0047]    While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. 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.