Abstract:
Provided are a lens driving unit that generates a precise linear motion in a spatially limited structure by using a bending vibration piezoelectric motor having a new structure, and a camera module comprising the lens driving unit. The lens driving unit includes: a lens carrier supporting a lens and comprising a guide axis exposed at least partially to the outside and extending in a direction substantially perpendicular to the lens; and a piezoelectric driving unit having a center portion contacting the guide axis according to a bending motion of a piezoelectric element and moving the lens carrier in a direction in which the guide axis extends.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2008-0101128, filed on Oct. 15, 2008, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lens driving unit and a camera module comprising the same, and more particularly, to a lens driving unit that generates a precise linear motion in a spatially limited structure by using a bending vibration piezoelectric motor so as to perform an auto-focusing (AF) function or a zooming function, and a camera module comprising the lens driving unit. 
     2. Description of the Related Art 
     Recently portable electronic devices have increasingly employed a camera module having an auto-focusing (AF) function or a zooming function. Cellular phones employ small and thin camera modules since the thicker the camera modules are, the thicker the cellular phones are. 
     A lens barrel supporting a lens is moved along a guide unit in order to perform the AF function or the zooming function. A stepping motor or a piezoelectric motor may be used as a driving unit for moving the lens barrel along the guide unit. The stepping motor is driven by a step waveform changed from an input pulse, is controlled and operated by an electronic circuit by using direct current power, and shows a fast response to a location control in a short distance. 
     However, the stepping motor needs a lot of components due to the sizes of a reduction gear, a connecting area, and itself, which may result in increasing the size of an operation module. Also, the increase in the number of components may increase manufacturing cost. 
     SUMMARY OF THE INVENTION 
     In an embodiment, the present invention provides a lens driving unit that generates a precise linear motion in a spatially limited structure by using a bending vibration piezoelectric motor having a new structure, and a camera module comprising the lens driving unit. The structure disclosed in the various embodiments of the present invention thereby also provides a means for supporting a lens and moving the lens along an axis substantially perpendicular to the face of the lens with a bending motion. 
     According to an aspect of the present invention, there is provided a lens driving unit comprising: a lens carrier supporting a lens and comprising a guide axis exposed at least partially to the outside and extending in a direction substantially perpendicular to the lens; and a piezoelectric driving unit having a center portion contacting the guide axis according to a bending motion of a piezoelectric element and moving the lens carrier in a direction in which the guide axis extends. 
     The piezoelectric driving unit may comprise: a first and second piezoelectric elements extending in a direction substantially perpendicular to the guide axis; an elastic element disposed between the first and second piezoelectric elements and extending in the direction substantially perpendicular to the guide axis; and a contacting unit disposed in a center portion of the elastic element and contacting the guide axis. The first and second piezoelectric elements substantially may have the same length, and wherein the elastic element is longer than the first piezoelectric element. 
     The lens driving unit may further comprise a driving unit holder supporting both ends of the elastic element. During a bending motion of the elastic element, a part of the elastic element supported by the driving unit holder slidably may contact a part of the driving unit holder supporting the elastic element. In addition, the lens driving unit may comprise at least one side spring formed on the driving unit holder so as to elastically maintain contact of the contacting unit to the guide axis. Alternatively or in addition, the lens driving unit may comprise a lower spring formed on the first piezoelectric element or the second piezoelectric element so as to provide a restoring force with regard to the bending motion of the piezoelectric element. 
     In various embodiments the lens driving unit includes also a ball bearing spaced apart from the guide axis on an exterior surface of the lens carrier and guiding the lens carrier in the direction in which the guide axis extends and a ball groove spaced apart from the guide axis on the exterior surface of the lens carrier and guiding the ball bearing in the direction in which the guide axis extends. The ball groove may be symmetrical to the guide axis about the lens carrier. There may be a plurality of ball bearings and a plurality of ball grooves in some embodiments of the invention. 
     In several embodiments, the piezoelectric driving unit moves the lens carrier according to a repetitive bending motion of the piezoelectric element. 
     In order to detect the position of the lens carrier with respect to a module base, some embodiments of the present invention include an extension wing extending from the exterior surface of the lens carrier; and a reflective plate formed on the bottom surface of the extension wing and detecting the movement of the lens carrier with a sensor formed separate from the reflective plate. 
     According to another aspect of the present invention, there is provided a camera module comprising: a lens carrier supporting a lens and comprising a guide axis exposed at least partially to the outside and extending in a direction substantially perpendicular to the lens; a piezoelectric driving unit having a center portion contacting the guide axis according to a bending motion of a piezoelectric element and moving the lens carrier in a direction in which the guide axis extends; and a module base supporting the lens carrier to allow the lens carrier to move in at least one direction. 
     The camera module may further comprise a cover coupled to the module base and covering the lens carrier and the piezoelectric driving unit; a circuit substrate coupled to an opposite surface of the module base to which the cover is coupled; and an image picking element formed on a surface of the circuit substrate to which the module base is coupled. 
     The camera module may further comprise an extension wing extending from the exterior surface of the lens carrier; a reflective plate formed on the bottom surface of the extension wing; and a sensor formed in a location of the module base corresponding to the reflective plate and detecting the movement of the lens carrier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a perspective view of a lens driving unit according to an embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of the lens driving unit shown in  FIG. 1 , according to an embodiment of the present invention; 
         FIG. 3  is a perspective view of a piezoelectric driving unit of the lens driving unit shown in  FIG. 1 , according to an embodiment of the present invention; 
         FIG. 4  is a diagram of the piezoelectric driving unit supported by a driving unit holder in the lens driving unit shown in  FIG. 1 , according to an embodiment of the present invention; 
         FIG. 5  is a diagram of the driving unit holder that supports the piezoelectric driving unit in the lens driving unit shown in  FIG. 1 , according to an embodiment of the present invention; 
         FIG. 6  is a diagram for explaining a driving principle of the piezoelectric driving unit shown in  FIG. 3 , according to an embodiment of the present invention; 
         FIG. 7  is a diagram for explaining a principle for moving a lens carrier by using the piezoelectric driving unit in the lens driving unit shown in  FIG. 1 , according to an embodiment of the present invention; 
         FIG. 8  is a driving waveform diagram of the piezoelectric driving unit used to move the lens carrier in the lens driving unit  100  shown in  FIG. 1 , according to an embodiment of the present invention; 
         FIG. 9  is a perspective view of a camera module comprising the lens driving unit shown in  FIG. 1 , according to an embodiment of the present invention; 
         FIG. 10  is an exploded perspective view of the camera module comprising the lens driving unit shown in  FIG. 1 , according to an embodiment of the present invention; and 
         FIG. 11  is a diagram of a location where the piezoelectric driving unit is formed in a cover of the camera module shown in  FIG. 9 , according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the present invention will be described in detail by explaining exemplary embodiments of the invention with reference to the attached drawings. 
       FIG. 1  is a perspective view of a lens driving unit  100  according to an embodiment of the present invention.  FIG. 2  is an exploded perspective view of the lens driving unit  100  shown in  FIG. 1 , according to an embodiment of the present invention.  FIG. 3  is a perspective view of a piezoelectric driving unit  120  of the lens driving unit  100  shown in  FIG. 1 , according to an embodiment of the present invention. 
     Referring to  FIGS. 1 through 3 , the lens driving unit  100  may comprise a lens carrier  110  and the piezoelectric driving unit  120 . 
     The lens carrier  110  for supporting a lens  111  inside thereof may comprise a guide axis  112 . The guide axis  112  may be at least partially exposed to the outside and extend in a direction substantially perpendicular to the lens  111 . 
     The guide axis  112  may be integrally attached to or disposed in the lens carrier  110  so that the guide axis  112  can extend in a length direction of the lens carrier  110  on the exterior surface of the lens carrier  110 . 
     The piezoelectric driving unit  120  may move the guide axis  112  in a direction in which the guide axis  112  extends since a center portion of the piezoelectric driving unit  120  contacts the guide axis  112 , according to the bending motions of first and second piezoelectric elements  121  and  122 . 
     Therefore, since the piezoelectric driving unit  120  partially contacts the guide axis  112  and the first and second piezoelectric elements  121  and  122  repeatedly perform a bending motion, the piezoelectric driving unit  120  may move the lens carrier  110  in an axial direction of the lens  111  according to repetitive friction and sliding motions between a part of the piezoelectric driving unit  120  and the guide axis  112 . 
     In the present embodiment, a bimorph type piezoelectric actuator may be used as the piezoelectric driving unit  120 . In this regard, the piezoelectric driving unit  120  may comprise two sheets of lead zirconate titanate and one sheet of a metal elastic body disposed between the two sheets of lead zirconate titanate. The first and second piezoelectric elements  121  and  122  perform the bending motion according to contraction and expansion of the two sheets of lead zirconate titanate. The piezoelectric driving unit  120  may move the lens carrier  110  according to a linear motion and an inertia motion followed by the bending motion. 
     In this regard, the piezoelectric driving unit  120  may comprise the first and second piezoelectric elements  121  and  122 , an elastic element  123 , and a contacting unit  124 . 
     The first and second piezoelectric elements  121  and  122  may extend in a direction substantially perpendicular to the guide axis  112 . The contacting unit  124  is disposed in the center portion of the elastic element  123  and may contact the guide axis  112 . 
     The elastic element  123  may be disposed between the first and second piezoelectric elements  121  and  122 , and may extend in the direction substantially perpendicular to the guide axis  112 . In the present embodiment, the first piezoelectric element  121  may be disposed on the upper surface of the elastic element  123 , and the second piezoelectric element  122  may be disposed on the lower surface of the elastic element  123 . 
     The first and second piezoelectric elements  121  and  122  substantially may have the same length. The elastic element  123  may be disposed between the first and second piezoelectric elements  121  and  122 , may extend longer than the first piezoelectric element  121  or the second piezoelectric element  122 . 
     The first and second piezoelectric elements  121  and  122  and the elastic element  123  substantially may have the same width. The piezoelectric driving unit  120  may be formed as a bimorph type thin belt and be disposed between the inner surface of a module base  200  shown in  FIG. 10  and the exterior surface of the lens carrier  110  having a cylindrical shape. In more detail, since the bimorph type piezoelectric actuator is used as the piezoelectric driving unit  120  of the lens carrier  110 , the piezoelectric driving unit  120  may be disposed between the exterior surface of the lens carrier  110  and the inner surface of the module base  200  with respect to the lens carrier  110  disposed in the module base  200 . 
     Therefore, the lens driving unit  100  may comprise the piezoelectric driving unit  120  of the lens carrier  110  in a limited space between the exterior surface of the lens carrier  110  and the inner surface of the module base  200 , thereby utilizing space in the lens driving unit  100  efficiently. 
     The lens driving unit  100  may further comprise a driving unit holder  130  for supporting both ends of the elastic element  123 . The driving unit holder  130  may be mounted on the module base  200  that supports the lens driving unit  100 , support the lens carrier  100  with the piezoelectric driving unit  120 , and allow the lens driving unit  100  to be moved with respect to the module base  200 . 
     In more detail, both ends of the piezoelectric driving unit  120  are supported by the driving unit holder  130 , and the first and second piezoelectric elements  121  and  122  are expanded or contracted by an application of power. The piezoelectric driving unit  120  performs the bending motion and thus the center portion thereof performs a straight motion upward or downward along the guide axis  112 . 
     The contacting unit  124  is disposed in the center portion of the elastic element  123  and contacts the guide axis  112 . Therefore, the bending motion of the piezoelectric driving unit  120  results in the straight motion of the contacting unit  124 , so that the guide axis  112  contacting the contacting unit  124  is moved. 
     In this regard, the lens driving unit  100  may comprise two side springs  141  and a lower spring  142  so that the lens carrier  110  can be elastically supported by the piezoelectric driving unit  120 . 
     The side springs  141  may be disposed on the driving unit holder  130  so that the contacting unit  124  maintains contact with the guide axis  112 . The side springs  141  may be disposed between the inner surface of the module base  200  and the driving unit holder  130  so that the exterior surface of the lens carrier  110  can be elastically supported by the piezoelectric driving unit  120 . 
     The driving unit holder  130  may comprise two first members  131 , which are projection units that can be inserted into the side springs  141 , in a location where the side springs  141  are disposed. 
     The lower spring  142  may be disposed on the first piezoelectric element  121  or the second piezoelectric element  122  so as to provide a restoring force with regard to the bending motion of the piezoelectric driving unit  120 . In the present embodiment, the lower spring  142  may be disposed under the second piezoelectric element  122 . The driving unit holder  130  may further comprise a second member  132 , which is a projection unit that is inserted into the lower spring  142 , in a location where the lower spring  142  is disposed. The second member  132  is formed to be projected from the surface where the second piezoelectric element  122  is disposed. 
     The lower spring  142  may be disposed between the driving unit holder  130  and the second piezoelectric element  122  and provides the restoring force upward when the piezoelectric driving unit  120  performs a downward bending motion. When the piezoelectric driving unit  120  performs an upward bending motion, the lower spring  142  is extended and provides the restoring force downward. 
     Also, the lens driving unit  100  may further comprise ball bearings  151  that are spaced apart from the guide axis  112  on the exterior surface of the lens carrier  110  and guide the lens carrier  110  in the direction in which the guide axis  112  extends. In more detail, when the lens carrier  110  moves in an axial direction of the lens  111 , the lens carrier  110  may be guided by the ball bearings  151  that are spaced apart from the guide axis  112  in the lens driving unit  100 . 
     The ball bearings  151  may move along two or more axes so as to stably support the lens carrier  110  in the module base  200  and more stably maintain a horizontal level of the lens  111 . The ball bearings  151  may be spaced apart from each other with respect to an axis. 
     The lens driving unit  100  may comprise a plurality of ball bearing grooves  113  that are spaced apart from the guide axis  112  on the exterior surface of the lens carrier  110  and extend in the direction in which the guide axis  112  extends so as to guide the ball bearings  151 . 
     In more detail, when the lens carrier  110  moves with respect to the module base  200 , the lens carrier  110  may point-contact with the module base  200  via the ball bearings  151  that roll along the ball bearing grooves  113 . The plurality of ball bearing grooves  113  are spaced apart from the guide axis  112  and extend in the direction in which the guide axis  112  extends so that the lens carrier  110  in the module base  200  is stably supported and the horizontal level of the lens  111  is more stably maintained. 
     If a single ball bearing groove  113  is formed so that the lens carrier  110  in the module base  200  is stably supported and the horizontal level of the lens  111  is more stably maintained, the single ball bearing groove  113  may be formed opposite to the guide axis  112  so as to be symmetrical with the guide axis  112  about the lens carrier  110 . The plurality of ball bearing grooves  113  may be symmetrical to each other about the guide axis  112 . The ball bearing grooves  113  may have V-shaped cross-sections so as to efficiently support the ball bearings  151 . 
     The ball bearings  151  may be rotatably fixed to the inner surface of the module base  200 . In this regard, a plurality of ball guides  152  may be disposed between the module base  200  and the lens carrier  110 , and be used for the ball bearings  151  to rotate on the inner surface of the module base  200 . 
     The ball guides  152  may be formed with insertion holes into which the ball bearings  151  may be inserted such that part of the surface of the ball bearings  151  faces toward the lens carrier  110 . The ball guides  152  may be disposed in a location where the ball bearing grooves  113  are formed. Thus, the number of ball guides  152  may be the same as the number of ball bearing grooves  113 . 
     Meanwhile, a location of the lens carrier  110  with regard to the module base  200  is necessarily detected. In this regard, a reflective plate  115  is formed on the lens carrier  110 , and the module base  200  may comprise a sensor for recognizing a location of the reflective plate  115 . 
     The lens carrier  110  comprises an extension wing  114  that extends from the exterior surface of the lens carrier  110 , and the reflective plate  115  may be formed on the bottom surface of the extension wing  114 . The reflective plate  115  may be used to sense the movement of the lens carrier  110  with the sensor formed separate from the reflective plate  115 . The sensor may be formed in the module base  200 . The sensor may be a photo reflector  210  comprising a light emitting unit and a light receiving unit. 
     The light emitting unit of the photo reflector  210  formed in the module base  200  emits light, the reflective plate  115  reflects the light, and the light receiving unit receives the light so that the location of the reflective plate  115  with respect to the photo reflector  210  is recognized. Thus, the relative location of the lens carrier  110  with respect to the module base  200  may be recognized with the photo reflector  210 . 
     In particular, the reflective plate  115  is horizontally disposed on the extension wing  114 , and the photo reflector  210  may be horizontally disposed in a location corresponding to the reflective plate  115 , so that the location of the reflective plate  115  with respect to the photo reflector  210  is recognized according to the intensity of the light received by the light receiving unit of the photo reflector  210 . 
     In this regard, if the lens carrier  110  moves and thus the reflective plate  115  is away from the photo reflector  210 , the intensity of the light received by the light receiving unit of the photo reflector  210  is reduced, and if the reflective plate  115  is closer to the photo reflector  210 , the intensity of the light received by the light receiving unit is increased. 
     In the lens driving unit  100 , the lens carrier  110  is elastically supported by the side springs  141  and is guided by the ball bearings  151  and the ball bearing grooves  113 , so that the lens carrier  110  is stably supported in the module base  200  and the horizontal level of the lens  111  is more stably maintained. 
     In more detail, the guide axis  112  that is driven by the piezoelectric driving unit  120  and in the lens carrier  110  is symmetrical with the ball bearing grooves  113  and the lens carrier  110  is supported by the module base  200 , so that the lens carrier  110  is horizontal to an image picking element  500  formed on the bottom surface of the module base  200  during a linear transfer and at a stop. 
       FIG. 4  is a diagram of the piezoelectric driving unit  120  supported by the driving unit holder  130  in the lens driving unit  100  shown in  FIG. 1 , according to an embodiment of the present invention.  FIG. 5  is a diagram of the driving unit holder  130  that supports the piezoelectric driving unit  120  in the lens driving unit  100  shown in  FIG. 1 , according to an embodiment of the present invention. 
     Referring to  FIGS. 4 and 5 , the driving unit holder  130  may support both ends of the elastic element  123 . When the elastic element  123  performs a bending motion, a part of the elastic element  123  supported by the driving unit holder  130  may slidably contact a part of the driving unit holder  130  supporting the elastic element  123 . 
     In more detail, both ends of the elastic element  123  supported by the driving unit holder  130  are not fixed to the driving unit holder  130 , so that the elastic element  123  may more flexibly perform the bending motion. 
     In this regard, the contacting unit  124  may be included in the part of the driving unit holder  130  supporting the elastic element  123 . When the elastic element  123  performs the bending motion, the part of the elastic element  123  supported by the driving unit holder  130  may slidably contact the part of the driving unit holder  130  supporting the elastic element  123  through a line contact or a point contact by using the contacting unit  124 . 
       FIG. 6  is a diagram for explaining a driving principle of the piezoelectric driving unit  120  shown in  FIG. 3 , according to an embodiment of the present invention.  FIG. 7  is a diagram for explaining a principle for moving the lens carrier  110  by using the piezoelectric driving unit  120  in the lens driving unit  100  shown in  FIG. 1 , according to an embodiment of the present invention.  FIG. 8  is a driving waveform diagram of the piezoelectric driving unit  120  used to move the lens carrier  110  in the lens driving unit  100  shown in  FIG. 1 , according to an embodiment of the present invention. 
     Referring to  FIGS. 6 through 8 , the piezoelectric driving unit  120  may be formed as a bimorph driving unit comprising the first and second piezoelectric elements  121  and  122  that are ultra-thin piezoelectric elements having two major axes and the elastic element  123  having the same width as the first and second piezoelectric elements  121  and  122  and longer than the first and second piezoelectric elements  121  and  122  in an axial direction. The first and second piezoelectric elements  121  and  122  may maintain contact with the upper and lower surfaces of the elastic element  123 , respectively, in the form of a sandwich. 
     The first and second piezoelectric elements  121  and  122  may be formed of lead zirconate titanate (PZT) or formed in a multi-stack type. Alternatively, the first and second piezoelectric elements  121  and  122  may be formed of single-crystal lead magnesium niobate-lead titanate (PMN-PT). 
     The guide axis  112  may be attached to the lens carrier  110  in a direction of the thickness of the elastic element  123  disposed between the first and second piezoelectric elements  121  and  122 . 
     To perform efficient driving, the first and second piezoelectric elements  121  and  122  may be electrically connected in parallel to each other. The first and second piezoelectric elements  121  and  122  may maintain the same dielectric direction, voltages may be applied to electrodes of the first and second piezoelectric elements  121  and  122 , and the elastic element  123  formed of conductive metal may be ground connected. 
     If voltages are applied in parallel to the piezoelectric driving unit  120 , a piezoelectric material having the same dielectric direction as the voltage direction is contracted, and a piezoelectric material having an opposite dielectric direction to the voltage direction is expanded. In this regard, if both ends of the piezoelectric driving unit  120  are supported, the piezoelectric driving unit  120  may generate a bending deformation and a maximum displacement along a central axis of the piezoelectric driving unit  120 . If a direct current voltage having an optional waveform and having a different speed component from a resonance frequency is applied to the piezoelectric driving unit  120 , the piezoelectric driving unit  120  in the central axis is repeatedly bent in an axial direction of the guide axis  112 . 
     Referring to  FIG. 6 , the first piezoelectric element  121  is expanded, whereas the second piezoelectric element  122  is contracted. Thus, the piezoelectric driving unit  120  having both its ends supported generates the bending deformation in a direction  121   a  toward the first piezoelectric element  121 . 
     In this regard, the contacting unit  124  is repeatedly bent in the axial direction of the guide axis  112 , and repeatedly produces friction and slides on the guide axis  112 , so that linear motions of a group of lenses may be generated by inertia, according to an application of a waveform, by receiving force from the piezoelectric driving unit  120 . 
     Referring to  FIG. 7 , a driving direction  161  is determined by the piezoelectric driving unit  120 , and a motion direction  162  is a direction in which the lens carrier  110  is transferred by using the piezoelectric driving unit  120 . In this regard, a voltage having the driving waveform shown in  FIG. 8  may be applied to the piezoelectric driving unit  120 . 
     The driving waveform may be generated by each of the unit chopping waves that may each include a first step  171  and a second step  172 . The piezoelectric driving unit  120  may be driven according to the sum of the continuous unit chopping waves. The first step  171  is a linearly increasing ramp waveform. The second step  172  is a directly falling waveform. 
     The contacting unit  124  and the guide axis  112  generate a friction motion according to the driving of the first step  171  and thus the lens carrier  110  may be transferred in a direction. The contacting unit  124  and the guide axis  112  generate a sliding motion according to the driving of the second step  172 . Transfers are overlapped by each chopping wave so that the lens carrier  110  may be transferred as desired. 
       FIG. 9  is a perspective view of a camera module  10  comprising the lens driving unit  100  shown in  FIG. 1 , according to an embodiment of the present invention.  FIG. 10  is an exploded perspective view of the camera module  10  comprising the lens driving unit  100  shown in  FIG. 1 , according to an embodiment of the present invention.  FIG. 11  is a diagram of a location where the piezoelectric driving unit  120  is formed in the cover  300  of the camera module  10  shown in  FIG. 9 , according to an embodiment of the present invention. 
     Referring to  FIGS. 9 through 11 , the camera module  10  may comprise the lens driving unit  100 , the module base  200 , the cover  300 , a circuit substrate  400 , and the image picking element  500 . 
     The module base  200  may be disposed in the camera module  10  so as to move the lens carrier  110  in at least one direction. The cover  300  may be coupled to the module base  200 , and may store the lens carrier  110  and the piezoelectric driving unit  120 . 
     The circuit substrate  400  may be coupled to an opposite surface of the module base  200  to which the cover  300  is coupled. The image picking element  500  may be formed on a surface of the circuit substrate  400  to which the module base  200  is coupled. 
     The camera module  10  may further comprise an infrared rays preventing filter  600  that is directly attached to a surface of the image picking element  500  toward the lens  111  and prevents an infrared rays component from an incident light. 
     The reflective plate  115  is formed on the lens carrier  110 . The sensor for detecting the location of the reflective plate  115  may be formed on the module base  200 . In this regard, the lens carrier  110  may comprise the extension wing  114  that extends from the exterior surface of the lens carrier  110 , and the reflective plate  115  may be formed on the bottom surface of the extension wing  114 . 
     The module base  200  may comprise a sensor that is disposed in a location corresponding to the reflective plate  115  and detects the movement of the lens carrier  110 . The sensor may be the photo reflector  210  comprising a light emitting unit and a light receiving unit. 
     The light emitting unit of the photo reflector  210  formed in the module base  200  emits light, the reflective plate  115  reflects the light, and the light receiving unit receives the light so that the location of the reflective plate  115  with regard to the photo reflector  210  is recognized. Thus, the relative location of the lens carrier  110  with respect to the module base  200  may be recognized with the photo reflector  210 . 
     In particular, the reflective plate  115  is horizontally disposed, and the photo reflector  210  may be horizontally disposed in a location corresponding to the reflective plate  115 , so that the location of the reflective plate  115  with respect to the photo reflector  210  is recognized according to the intensity of the light received by the light receiving unit. 
     Also, the driving unit holder  130  may comprise the first members  131  and the second member  132 . The first member  131  is a projection unit disposed in a location where the side springs  141  are disposed and can be inserted into the side springs  141 . The second member  132  is a projection unit disposed in a location where the lower spring  142  is disposed and can be inserted into the lower spring  142 . 
     The module base  200  may comprise a first insertion groove  220 . The first insertion grooves  220  are insertion grooves where the side springs  141  are inserted. 
     If the side springs  141  are inserted into the first insertion grooves  220  the first members  131  for supporting the side springs  141  may be formed in the first inserting grooves  220 . 
     The camera module  10  uses a bimorph type piezoelectric actuator as the piezoelectric driving unit  120  of the lens carrier  110  so that the camera module  10  may be disposed between the exterior surface of the lens carrier  110  and the inner surface of the module base  200  with regard to the lens carrier  110  disposed in the module base  200 . 
     In more detail, the piezoelectric driving unit  120  of the lens carrier  110  may be disposed in a location shown by a dotted line in  FIG. 11  in a limited space between the exterior surface of the lens carrier  110  and the inner surface of the module base  200 , thereby utilizing space in the lens driving unit  100  efficiently. 
     The lens carrier  110  is elastically supported by the side springs  141  and is guided by the ball bearings  151  and the ball bearing grooves  113 , so that the lens carrier  110  is stably supported in the module base  200  and a horizontal level of the lens  111  is more stably maintained. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by one of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.