Abstract:
A camera module according to an exemplary embodiment of the present disclosure includes a housing forming an exterior appearance of the camera module, a PCB (Printed Circuit Board) mounted with an image sensor where one end of which is fixed to the housing and the other end is exposed to an outside to be connected to other parts, a lens holder including at least one or more pieces of lenses and so arranged as to be spaced apart from the image sensor at a predetermined distance, and at least two actuators mounted at areas other than an image sensor-mounted area of the PCB, wherein a position of the image sensor is controlled in response to strains of the actuators.

Description:
[0001]    Pursuant to 35 U.S.C. §119 (a), this application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2012-0028565, filed on Mar. 21, 2012, the contents of which are hereby incorporated by reference in their entirety. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    1. Field of Endeavor 
         [0003]    The teachings in accordance with exemplary and non-limiting embodiments of this disclosure relate generally to a camera module. 
         [0004]    2. Background 
         [0005]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0006]    Recently, small-sized camera modules are highly demanded in a variety of multimedia fields, such as tablet computers, camera phones, PDAs (Personal Digital Assistants), smart phones, and toys, and image input devices, such as monitoring cameras and information terminals of video tape recorders. Particularly, trends are to develop miniaturized camera modules for smart phones in response to increased demands by consumers preferring a small-sized design. 
         [0007]    The camera module is manufactured using an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), where light of an object is concentrated through a lens to the image sensor, and an optical signal is converted into an electrical signal for display on a display unit such as an LCD display device. 
         [0008]    The camera module includes a plurality of lenses, and adjusts an optical focal length by changing a relative distance while being mounted with a driving source to move respective lenses. A VCM (Voice Coil Motor) is commonly used to implement an autofocus function, but the VCM suffers from disadvantages in that it is voluminous and limited in accurate control and miniaturization of camera module. 
       SUMMARY OF THE DISCLOSURE 
       [0009]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0010]    Exemplary embodiments of the present disclosure are provided to solve the aforementioned technical problems, configured to improve a structure of the camera module for implementing an auto focusing function by moving an image sensor relatively lighter than a lens, and to enable a miniaturization over a conventional camera module. 
         [0011]    Exemplary embodiments of the present disclosure are also provided to compensate a user handshake by lifting and tilting controls of an image sensor. 
         [0012]    It should be emphasized, however, that the present disclosure is not limited to particular disclosures, as explained above. It should be understood that other technical subjects not mentioned herein may be appreciated by those skilled in the art. 
         [0013]    In one general aspect of the present disclosure, there is provided a camera module, a camera module comprising: a PCB (Printed Circuit Board) having an image sensor mounted thereon a housing which is fixed to the PCB; a lens holder including at least one or more pieces of lenses and so arranged as to be spaced apart from the image sensor at a predetermined distance; and at least two actuators disposed at areas other than an image sensor-mounted area of the PCB, wherein a position of the image sensor is controlled according to the actuators. 
         [0014]    Preferably, but not necessarily, the actuators may be provided in piezoelectric actuators. 
         [0015]    Preferably, but not necessarily, the PCB may be formed with a flexible material. 
         [0016]    Preferably, but not necessarily, the image sensor may be controlled in at least one movement of lifting and tilting movements in response to strains of the piezoelectric actuators to enable at least one or more controls of an auto focusing and a handshake compensation control. 
         [0017]    Preferably, but not necessarily, the actuators may be symmetrically arranged about the image sensor. 
         [0018]    Preferably, but not necessarily, the piezoelectric actuator may include a first piezoelectric actuator and a second piezoelectric actuator, each actuator having same size and directivity. 
         [0019]    Preferably, but not necessarily, the actuators may be installed at an opposite side of an image sensor-mounted side of the PCB. 
         [0020]    Preferably, but not necessarily, the camera module may further comprise a pair of elastic support members that pass a center of the image sensor, where one end of the pair of elastic support members is fixed to the housing and the other end is connected to the PCB on an imaginary extension line of a direction perpendicular to a center line of the actuator. 
         [0021]    Preferably, but not necessarily, the camera module may further comprise a reinforcement member interposed between the PCB and the image sensor. 
         [0022]    Preferably, but not necessarily, the camera module may further comprise a reinforcement member a position corresponding to an opposite side of the image sensor-mounted surface of the PCB. 
         [0023]    Preferably, but not necessarily, the reinforcement member may be provided with a plate material configured to maintain a predetermined flatness. 
         [0024]    Preferably, but not necessarily, the PCB may be supported by the housing and at least two or more areas to maintain a tight state by adding a tension of more than a predetermined size. 
         [0025]    Preferably, but not necessarily, the lens holder may be fixed to a position of the housing. 
         [0026]    Preferably, but not necessarily, the image sensor and the piezoelectric actuators may be supplied with a power through the PCB. 
         [0027]    Preferably, but not necessarily, the first and second piezoelectric actuators may be so mounted as to be strained with same directivity, in a case a power of same size and same polarity is supplied. 
         [0028]    Preferably, but not necessarily, the first and second piezoelectric actuators may ascend or descend the image sensor, in a case the first and second piezoelectric actuators are strained to a same direction, and tilt the image sensor, and in a case the first and second piezoelectric actuators are strained to an opposite direction. 
         [0029]    Preferably, but not necessarily, deflection of the image sensor may be adjusted in response to size of voltage applied to the first and second piezoelectric actuators. 
         [0030]    The camera module according to exemplary embodiments of the present disclosure has an advantageous effect in that size of the camera module can be miniaturized by lifting and tilting a relatively light image sensor to implement an auto focusing function. 
         [0031]    Another advantageous effect is that tilting of the image sensor can be controlled to compensate dispersion of focus at a remote isolated portion of the image sensor, in a case the camera module according the exemplary embodiments of the present disclosure is applied to a camera module using a conventional VCM as an auto focusing unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    In order to explain the principle of the present disclosure, some accompanying drawings related to its preferred embodiments are below reported for the purpose of illustration, exemplification and description, although they are not intended to be exhaustive. The drawing figures depict one or more exemplary embodiments in accord with the present concepts, by way of example only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements. 
           [0033]    Thus, a wide variety of potential practical and useful embodiments will be more readily understood through the following detailed description of certain exemplary embodiments, with reference to the accompanying exemplary drawings in which: 
           [0034]      FIG. 1  is a schematic cross-sectional view illustrating a lateral surface of a camera module according to an exemplary embodiment of the present disclosure; 
           [0035]      FIG. 2  is a schematic view illustrating a bottom of the camera module of  FIG. 1  according to a first exemplary embodiment of the present disclosure; 
           [0036]      FIG. 3  is a schematic view illustrating a bottom of the camera module of  FIG. 1  according to a second exemplary embodiment of the present disclosure; 
           [0037]      FIG. 4  is a schematic view illustrating an operation of auto focusing function of an image sensor according to an exemplary embodiment of the present disclosure; 
           [0038]      FIG. 5  is a schematic view illustrating an operation of handshake compensation function of an image sensor according to an exemplary embodiment of the present disclosure; 
           [0039]      FIG. 6  is a schematic view illustrating a coupled relationship of an image sensor, a reinforcement member and piezoelectric actuators on a PCB of a camera module according to a third exemplary embodiment of the present disclosure; and 
           [0040]      FIG. 7  is a schematic view illustrating a coupled relationship of an image sensor, a reinforcement member and piezoelectric actuators on a PCB of a camera module according to a fourth exemplary embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    Now, the camera module according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0042]      FIG. 1  is a schematic cross-sectional view illustrating a lateral surface of a camera module according to an exemplary embodiment of the present disclosure,  FIG. 2  is a schematic view illustrating a bottom of the camera module of  FIG. 1  according to a first exemplary embodiment of the present disclosure,  FIG. 3  is a schematic view illustrating a bottom of the camera module of  FIG. 1  according to a second exemplary embodiment of the present disclosure,  FIG. 4  is a schematic view illustrating an operation of auto focusing function of an image sensor according to an exemplary embodiment of the present disclosure,  FIG. 5  is a schematic view illustrating an operation of handshake compensation function of an image sensor according to an exemplary embodiment of the present disclosure,  FIG. 6  is a schematic view illustrating a coupled relationship of an image sensor, a reinforcement member and piezoelectric actuators on a PCB of a camera module according to a third exemplary embodiment of the present disclosure, and 
         [0043]      FIG. 7  is a schematic view illustrating a coupled relationship of an image sensor, a reinforcement member and piezoelectric actuators on a PCB of a camera module according to a fourth exemplary embodiment of the present disclosure. 
         [0044]    Referring to  FIG. 1 , the camera module according to an exemplary embodiment of the present disclosure includes a PCB  10 , a lens holder  20 , a piezoelectric actuator  30 , where these constituent parts are preferably installed inside a housing  1 . 
         [0045]    The housing  1  forms an external appearance of the camera module in a box shape, and is preferably formed therein with a space unit of a predetermined size to accommodate the constituent parts. The housing  1  is also provided with an opening (not shown) configured to open an optical path formed between the lens holder  20  and the image sensor  11 . 
         [0046]    The PCB  10  is preferably provided with a flexible material. According to an exemplary embodiment of the present disclosure, the PCB  10  is preferably provided in an F-PCB (Flexible PCB) and integrally equipped with an electronic circuit pattern and a plurality of terminals. The PCB  10  is preferably mounted at an upper surface thereof with the image sensor  11 , where the image sensor  11  may be directly mounted to the upper surface of the PCB  11  by way of soldering or wire bonding. 
         [0047]    The lens holder  20  may be mounted with at least one or more pieces of lenses  21 , and is preferably fixed in position to the housing  1 . 
         [0048]    At least a pair of piezoelectric actuators  30  is mounted at the PCB  10 . The pair of piezoelectric actuators  30  moves the PCB  10  to allow the image sensor  11  to lift and/or tilt relative to the lens  21 . The piezoelectric actuator  30  may be formed with first and second piezoelectric actuators  30   a ,  30   b , and according to a first exemplary embodiment of the present disclosure illustrated in  FIGS. 1 and 2 , each of the first and second piezoelectric actuators  30   a ,  30   b  is provided in a same size and mounted to the PCB  10  to avoid being interfered with the image sensor  11 . 
         [0049]    Preferably, the actuators may be installed at an opposite side of an image sensor-mounted side of the PCB  10 . Furthermore, the first and second piezoelectric actuators  30   a ,  30   b  are spaced apart from the image sensor  11  at a same distance. Operation of the piezoelectric actuators  30  will be described in detail later. 
         [0050]    Meantime, according to a second exemplary embodiment of the present disclosure, the PCB  10  may be elastically suspended from the housing  1  by an elastic support member  40 . In this case, as illustrated in  FIG. 3 , the elastic support member  40  passes a center of the image sensor  11  and preferably arranged on an extension line perpendicular to an imaginary line passing a center of the piezoelectric actuator  30 . 
         [0051]    In a case the elastic support member  40  is installed as described above, the elastic support member  40  can support a horizontal position of the PCB  10  and can provide a restoring force to lifting and/or pivoting, tilting operations of the image sensor  11 . 
         [0052]      FIGS. 4 and 5  are schematic views illustrating movement of the image sensor  11  in response to the movement of the piezoelectric actuator  30  according to first and second exemplary embodiments of the present disclosure. 
         [0053]    Referring to  FIG. 4 , the PCB  10  mounted with the image sensor  11  may be fixed to at least two portions of the housing  1  in a tight state. Meanwhile, due to the fact that the PCB  10  is formed with a flexible material, portions other than a portion mounted with the image sensor  11  may be bent if the piezoelectric actuator  30  is strained (transformed or deformed). 
         [0054]    Furthermore, in a case the first and second piezoelectric actuators  30   a ,  30   b  are provided with a power of same size and polarity, the first and second piezoelectric actuators  30   a ,  30   b  may be strained (transformed or deformed) to have a same directivity. For example, in a case the first and second piezoelectric actuators  30   a ,  30   b  are convexly deflected to an upper side as shown in  FIG. 4 , the image sensor  11  may be lifted to an arrow direction relative to a reference position as shown in  FIG. 4 , because both ends of the PCB  10  are fixed by the housing  1 , where a lifting height can be adjusted in response to a changing size of voltage applied to the first and second piezoelectric actuators  30   a ,  30   b.    
         [0055]    In a case the image sensor  11  is directly lifted as described above, a focal length of the lens  21  can be changed to realize the auto focusing function. 
         [0056]    Furthermore, as illustrated in  FIG. 5 , in a case the first and second piezoelectric actuators  30   a ,  30   b  are respectively provided with a power of different size and polarity, the first and second piezoelectric actuators  30   a ,  30   b  may be deformed to mutually different directions. For example, as illustrated in  FIG. 5 , although the first piezoelectric actuator  30   a  is convexly deformed to an upper side, the second piezoelectric actuator  30   b  may be concavely transformed to the bottom side, whereby the image sensor  11  may be tilted to an arrow direction as shown in  FIG. 5 . 
         [0057]    Hence, it is possible to finely adjust a focus at a remote cornered area deviated from a center of the image sensor  11  through motion control of the image sensor  11 , and it is also possible to controllably shift and tilt the image sensor  11  for user handshake compensation. 
         [0058]    As mentioned above, although the PCB  10  is formed with a flexible material, the PCB  10  must maintain as tightened state as possible when installed inside the housing  1  to constantly maintain a flatness of the image sensor  11 . In order to further strongly maintain the flatness of the image sensor  11 , the camera module according to third and fourth exemplary embodiments of the present disclosure may further include a reinforcement member  12  between the image sensor  11  and the PCB  10 , or at a surface opposite to the PCB  10  mounted with the image sensor  11 . 
         [0059]    That is, as illustrated in  FIGS. 6 and 7 , the reinforcement member  12  may be provided with a plate member having a same corresponding size as that of the image sensor  11  and a predetermined strength. In consideration of lightness of the product, the reinforcement member  12  may be vacant at a center portion thereof and configured to support only an edge of the image sensor  11 . 
         [0060]    In a case the reinforcement member  12  is provided as mentioned above, a portion, where the image sensor  11  is mounted, can always maintain a flatness even if the PCB  10  is a bit twisted, and therefore it is possible for an image captured by the image sensor  11  to maintain a predetermined shape. 
         [0061]    Meanwhile, albeit not illustrated, it is possible to add a configuration same as the piezoelectric actuator  30  instead of the elastic support member  40 . In this case, a finer and/or more elaborate lifting and tilting control of the image sensor may be implemented. 
         [0062]    Although the abovementioned exemplary embodiments have explained and described a structure in which the lens holder  20  is fixed to the housing  1 , the present disclosure is not limited thereto, such that, albeit not illustrated, a conventional camera module using a VCM as an auto focusing unit may be applied with the configuration according to the exemplary embodiments of the present disclosure, whereby an OIS (Optical Image Stabilization) function can be realized using a simpler structure than that of a conventional handshake compensation module. 
         [0063]    Although the present disclosure has been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure.