Abstract:
There is provided an apparatus for driving auto focusing including: a motion sensor outputting motion data on motion of a camera module; a processor generating a control signal for controlling a focus of a subject based on the motion data; and an optical driving module moving a lens in a predetermined direction based on the control signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2014-0113775, filed on Aug. 29, 2014, entitled “Apparatus for Driving Auto Focusing and Controlling Method Thereof” which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND 
       [0002]    The present disclosure relates to an apparatus for driving auto focusing and a controlling method thereof. 
         [0003]    A photographing device such as a digital camera, a camcorder, a camera phone, or the like, includes a lens and an image sensor in which an image of a subject transmitted through the lens is photographed and adjusts a distance between the lens and the image sensor by changing a position of the lens. 
         [0004]    Therefore, auto focusing (AF) is a function of adjusting a focus of the image of the subject photographed in the image sensor, changing the position of the lens to calculate a focusing degree of the image of the subject at each position, and automatically adjusting the position of the lens so as to have an optimal focus. 
         [0005]    In addition, as an auto focusing method, first, there is a contrast detection method of measuring a contrast of a specific portion of the image using the image sensor while continuously moving the lens, and determining that the lens is focused when the contrast becomes maximum. 
         [0006]    In addition, as the auto focusing method, second, there is a phase-difference detection method of determining a driving direction and a driving amount of the lens based on phase-difference data generated at the time of separating incident light into two parts to thereby be incident on two different sensors, respectively. 
       RELATED ART DOCUMENT 
     Patent Document 
       [0007]    (Patent Document 1) KR 2009-0104769 
       SUMMARY 
       [0008]    An aspect of the present disclosure may provide an apparatus for driving auto focusing capable of detecting a driving direction and a movement amount of a lens based on output data of a motion sensor corresponding to motion of a subject, in order to solve problems caused by performing an auto focusing method according to the related art. 
         [0009]    In an apparatus for driving auto focusing and a controlling method thereof according to exemplary embodiments of the present disclosure, an accurate movement amount and movement direction of a lens may be detected using acceleration data corresponding to motion of a camera module, such that an accurate and rapid auto focusing operation may be performed as compared to an auto focusing method according to the related art. 
         [0010]    According to an aspect of the present disclosure, an apparatus for driving auto focusing may include: a motion sensor outputting motion data on motion of a camera module; a processor generating a control signal for controlling a focus of a subject based on the motion data; and an optical driving module moving a lens in a predetermined direction based on the control signal. 
         [0011]    Further, the processor may calculate a phase-difference variable C between images formed on an image sensor depending on motion of the camera module based on acceleration data from which static acceleration data are removed, and detect a defocus amount (movement amount) of the lens corresponding to the phase-difference variable C. 
         [0012]    In addition, the processor may generate a control signal corresponding to the defocus amount and movement direction of the lens to transmit the control signal to an optical driver. The optical driver may generate a driving current depending on the control signal to apply the driving current to an actuator, and the actuator may move the lens in an optical axis direction depending on the driving current to re-set a focus of the subject depending on motion of the camera module. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]    The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0014]      FIG. 1  is a block diagram of an apparatus for driving auto focusing according to an exemplary embodiment of the present disclosure; 
           [0015]      FIG. 2A  is a diagram illustrating a state in which a focus of a subject is adjusted for a lens, and  FIG. 2B  is a diagram illustrating a state in which the focus of the subject is moved depending on motion of the subject; 
           [0016]      FIG. 3  is a diagram schematically illustrating an auto focusing method according to an exemplary embodiment of the present disclosure; and 
           [0017]      FIG. 4  is a flow chart illustrating a controlling method of an apparatus for driving auto focusing according to an exemplary embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The objects, features and advantages of the present disclosure will be more clearly understood from the following detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted. Further, in the following description, the terms “first,” “second,” “one side,” “the other side” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. Further, in the description of the present disclosure, when it is determined that the detailed description of the related art would obscure the gist of the present disclosure, the description thereof will be omitted. 
         [0019]    Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
         [0020]      FIG. 1  is a block diagram of an apparatus for driving auto focusing according to an exemplary embodiment of the present disclosure. The apparatus for driving auto focusing according to an exemplary embodiment of the present disclosure includes a motion sensor sensing a velocity change of motion of a subject, or the like, a processor generating a control signal for controlling a focus of the subject based on output data of the motion sensor, and an optical driving module driving the lens based on the control signal. 
         [0021]    The motion sensor  100  may be provided the inside or outside a camera module  130 , sense a velocity change for motion of the camera module  130 , and output data on the velocity change. 
         [0022]    That is, the motion sensor  100  may include an angular velocity sensor  102  sensing a rotational component (angle) change of the camera module  130  and an acceleration sensor  101  sensing a linear component (velocity) change by motion of the camera module  130  in a vertical or horizontal direction. 
         [0023]    Here, 1) the angular velocity sensor  102  may be a gyro sensor capable of sensing angle changes in x-axis, y-axis, and z axis directions in order to compensate vertical and horizontal hand vibration of the camera module  130  caused by hand vibration of a user, and 2) the acceleration sensor  101  may sense the velocity changes of the camera module  130  by the user in the x-axis, y-axis, and z axis directions, wherein the velocity changes correspond to the linear component for motion of the camera module  130 . 
         [0024]    A lens  131  may form an image of light flux from the subject on an image sensor  132  and include a zoom lens, a focus lens, or a compensation lens. In addition, the image sensor  132  may be a charge coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) optically treating light from the subject to detect an image of the subject and converting an optical signal of incident light into an electrical analog signal. 
         [0025]    The processor  110  generates the control signal for controlling the focus of the subject based on the output data of the motion sensor  100  to transmit the control signal to the optical driving module  120 . Here, the processor  110  includes a sensor data compensator  111  and a controller  112 . 
         [0026]    In addition, the processor  110  removes static acceleration data included in output data of the acceleration sensor  101  using output data of the angular velocity sensor  102  depending on motion of the camera module  130 . 
         [0027]    Further, the processor  110  calculates a phase-difference variable C between images formed on the image sensor  132  depending on the motion of the subject based on the output data of the acceleration sensor from which the static acceleration data are removed, and detects a defocus amount (movement amount) of the lens corresponding to the phase-difference variable C. 
         [0028]    The sensor data compensator  111  removes the static acceleration data included in the output data of the acceleration sensor  101  using the output data of the angular velocity sensor  102  depending on motion of the camera module  130 . 
         [0029]    That is, the acceleration data output from the acceleration sensor  101  includes the static acceleration data and dynamic acceleration data. The static acceleration data are data on rotation for a small tilt of the camera module  130 , or the like, gravity acceleration, or the like, and in the case in which the static acceleration data are not compensated (removed), wrong focusing may be performed during an auto focusing process for motion of the camera module  130 . 
         [0030]    Therefore, the sensor data compensator  111  calculates the rotational component of the camera module  130  from angular velocity data depending on motion of the camera module  130  and performs a compensation step of removing the static acceleration data from the acceleration data using the rotational component. 
         [0031]    In addition, the controller  112  calculates the phase-difference variable C between images of the subject formed on the image sensor depending on motion of the subject based on the output data of the sensor data compensator  111  and generates a control signal for the defocus amount (movement amount) of the lens  131  corresponding to the phase-difference variable C and a movement direction of the lens  131 . 
         [0032]    The optical driving module  120  includes an actuator  122  moving the lens  131  in an optical axis direction and an optical driver  121  applying a driving current depending on the control signal transmitted from the processor  110  to the actuator  122 . 
         [0033]    The optical driver  121  generates a driving voltage of the actuator  122  for moving the lens  131  depending on the control signal input from the processor  110  and a control signal (driving current). 
         [0034]    Further, the optical driver  121  controls the driving of the actuator  122  through a switching operation corresponding to the control signal to control a moving range of the lens  131 . Here, the optical driver  121  may be embedded in the processor  110  as a motor driver IC, and the actuator  122  includes a voice coil motor (VCM) or piezoelectric device. 
         [0035]    The processor  110 , the sensor data compensator  111 , and the controller  112  as described above may include algorisms for performing the above-mentioned functions and be implemented by firmware, software, or hardware (for example, a semiconductor chip or application-specific integrated circuit). 
         [0036]    Hereinafter, the apparatus for driving auto focusing and a controlling method thereof according to the present disclosure will be described with reference to  FIGS. 2 to 4 . 
         [0037]      FIG. 2A  is a diagram illustrating a state in which a focus of the subject is adjusted for the lens, and  FIG. 2B  is a diagram illustrating a state in which the focus of the subject is moved depending on motion of the subject.  FIG. 3  is a diagram schematically illustrating an auto focusing method according to an exemplary embodiment of the present disclosure, and  FIG. 4  is a flow chart illustrating a controlling method of an apparatus for driving auto focusing according to an exemplary embodiment of the present disclosure. 
         [0038]    As illustrated in  FIG. 2A , when light passing through the lens  131  is concentrated on an image photograping surface of the image sensor  132  while being collected on one point, the image of the subject becomes vivid. In this case, the subject is in a state in which the focus thereof is adjusted for the lens  131 . 
         [0039]    For example, based on one point a 1  configuring the subject, an interval between one point a 1  and the lens is a, and the light incident from the one point a 1  on the lens  131  is concentrated on the image photograping surface of the image sensor  132  spaced apart from the lens  131  by b. 
         [0040]    However, as illustrated in  FIG. 2   b , in the case in which one point a 1  of the subject is moved to another point a 2  depending on motion of the camera module  130 , the interval between one point a 1  and the lens  131  is changed (a→a′), such that a point on which light incident from another point a 2  transmits through the lens  131  to thereby be collected is changed from b into b′. 
         [0041]    That is, as the subject becomes close to the lens  131 , a focal length for the subject is increased. In this case, the lens  131  moves toward the subject in order to adjust the focus of the subject to thereby become far away from the image photograping surface of the image sensor  132 . 
         [0042]    In this case, a circle of confusion formed by scattering of the light incident from another point a 2  is formed on the image photograping surface of the image sensor  132 , and a size δ of the circle of confusion is determined depending on an interval between the subject and the lens  131 . Here, δ means a phase-difference between images (interval between two images) formed on the image photograping surface of the image sensor  132  in a state in which the focus of the subject is adjusted and in a state in which the focus of the subject is not adjusted. 
         [0043]    Therefore, as illustrated in  FIG. 3 , in the apparatus  10  for driving auto focusing according to the exemplary embodiment of the present disclosure, in the case in which the subject is positioned at a S 1  position, light incident from one point of the subject transmits through the lens  131  to thereby be concentrated on the image photograping surface of the image sensor  132 . That is, the image of the subject is in a state in which a focus thereof is adjusted for the lens  131 . 
         [0044]    In this case, the processor  110  calculates a distance P between the subject and the lens  131  using a distance I between the lens  131  and the image sensor  132  and a natural focal distance F of the lens  131 . Here, I and F are preset values due to characteristics of the camera module  130 . 
         [0045]    In addition, when the position of the subject is changed into S 2  depending on motion of the camera module  130  by the user, the acceleration sensor  101  outputs acceleration data on the velocity change in a linear direction and angular velocity data on rotation, corresponding to motion of the camera module  130  (S 100 ). 
         [0046]    Then, the sensor data compensator  111  removes (compensates) the static acceleration data included in the acceleration data using the angular velocity data (S 110 ) to transmit the acceleration data from which the static acceleration data are removed to the controller  112 . 
         [0047]    In addition, the controller  112  calculates a phase-difference variable C between images of the subject formed on the image sensor  132  corresponding to motion of the camera module  130  using the acceleration data from which the static acceleration data are removed (S 120 ). 
         [0048]    That is, the controller  112  calculates the phase-difference variable C according to the following [Equation 1] and [Equation 2] using the acceleration data transmitted from the sensor data compensator  111 . 
         [0000]    
       
         
           
             
               
                 
                   
                     
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         [0049]    Here, P indicates the distance between the lens  131  and the subject, and I indicates the distance between the lens  131  and the image sensor  132 . F indicates the natural focal distance of the lens  131 , D indicates a distance between a point at which the subject is moved and the lens  131 , and A indicates a diameter of the lens. 
         [0050]    In more detail, the controller  112  detects a movement direction of the camera module  130  from the acceleration data transmitted from the sensor data compensator  111 . That is, the reason is that the acceleration data are vector values having a magnitude and a direction. 
         [0051]    In addition, a movement distance of the camera module  130  may be calculated through integration of the acceleration data, such that a change (P-D) in the distance between the subject and the camera module  130 . 
         [0052]    Further, the controller  112  calculates the phase-difference variable C according to [Equation 1] and [Equation 2] using the distance I between the lens  131  and the image sensor  132  detected in advance in a state in which the focus of the subject is adjusted before the camera module  130  moves, the distance P between the lens  131  and the subject, and the diameter A of the lens  131 , which is a natural property of the lens  131 . 
         [0053]    Thereafter, the controller  112  calculates a defocus amount (movement amount) of the lens required in order to adjust the focus of the subject changed depending on the motion of the camera module  130  using the phase-difference variable C (S 130 ) and generates a control signal for moving the lens  131  depending on the defocus amount. 
         [0054]    Here, the phase-difference variable C is 2δ, and the defocus amount of the lens  131  depending on the phase-difference δ, which is a pre-calculated value at the time of designing the lens  131 , may be stored in a memory (not illustrated), or the like. 
         [0055]    In addition, the controller  112  transmits the control signal to the optical driver  121  and the optical driver  121  generates a driving current corresponding to the control signal to apply the driving current to the actuator  122 . 
         [0056]    Therefore, the actuator  122  moves the lens  131  depending on the defocus amount and the movement direction corresponding to the control signal to re-adjust the focus of the subject (S 140 ). 
         [0057]    As described above, in the apparatus for driving auto focusing and the controlling method thereof according to the present disclosure, the accurate movement amount and movement direction of the lens may be detected using the acceleration data corresponding to motion of the camera module, such that an accurate and rapid auto focusing operation may be performed as compared to an auto focusing method according to the related art. 
         [0058]    Although the embodiments of the present disclosure have been disclosed for illustrative purposes, it will be appreciated that the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure. 
         [0059]    Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the disclosure, and the detailed scope of the disclosure will be disclosed by the accompanying claims.