Abstract:
A camera module having a housing accommodating a lens module; a lens driver, comprising a magnet mounted in the housing, configured to induce a driving force along an optical axis direction and in a direction perpendicular to the optical axis direction; and a yoke portion offset from the magnet along the optical axis direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims the benefit under 35 USC 119(a) of Korean Patent Application No. 10-2014-0180727 filed on Dec. 15, 2014, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to a camera module. 
         [0004]    2. Description of Related Art 
         [0005]    Highly functional, ultra-small camera modules have recently been provided in mobile communications terminals such as tablet PCs, laptop computers, and the like, as well as cellular phones such as smartphones. 
         [0006]    Camera modules have advanced from fixed focus camera modules to auto-focusing camera modules having auto-focus (AF) actuators. As mobile communication terminals continue to be miniaturized, incidence of image distortions, caused by a hand-shake during image capturing, increases. Optical image stabilization (OIS) actuators have been used to stabilize camera modules in the case of hand-shake. When a magnet is used in the AF actuator and the OIS actuator, a magnetic field formed by the magnet may be influenced by external magnetism generated around the camera module. 
         [0007]    Therefore, since the magnetic field of the magnet may be influenced by external magnetism during driving for auto-focusing or OIS, a problem in which the camera module malfunctions or is not driven in an exact location may occur. 
       SUMMARY 
       [0008]    This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
         [0009]    In one general aspect, a camera module is capable of reducing an influence of external magnetism and improving driving reliability in auto-focusing and optical image stabilization (OIS). The camera module includes a lens driver including a magnet generating a driving force in an optical axis direction and in a direction perpendicular to the optical axis direction; and a yoke portion spaced apart from the magnet in the optical axis direction. A magnetic field of the magnet is formed in a relatively small space, thereby reducing an influence of external magnetism. 
         [0010]    In another general aspect, a camera module having a housing accommodating a lens module; a lens driver, comprising a magnet mounted in the housing, configured to induce a driving force along an optical axis direction and in a direction perpendicular to the optical axis direction; and a yoke portion offset from the magnet along the optical axis direction. 
         [0011]    A method of reducing external magnetic interference in a lens module comprising: disposing lens module within a housing; disposing a first coil within the lens module; disposing a second coil on an inner surface of a case; disposing a magnet between the first coil and the second coil, wherein the magnet generates a magnetic field; and disposing a yoke offset from the magnet along an optical axis, wherein the yoke comprises a magnetic material that limits the size of the magnetic field of the magnet. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a perspective view of a camera module; 
           [0013]      FIG. 2  is an exploded perspective view of a camera module; 
           [0014]      FIG. 3  is an exploded perspective view of a camera module; 
           [0015]      FIG. 4  is a schematic perspective view of the arrangement of a lens driver and a yoke portion; and 
           [0016]      FIG. 5  is a cross-sectional view of line A-A′ of  FIG. 4 . 
       
    
    
       [0017]    Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience. 
       DETAILED DESCRIPTION 
       [0018]    The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be apparent to one of ordinary skill in the art. The sequences of operations described herein are merely examples, and are not limited to those set forth herein, but may be changed as will be apparent to one of ordinary skill in the art, with the exception of operations necessarily occurring in a certain order. Also, descriptions of functions and constructions that are well known to one of ordinary skill in the art may be omitted for increased clarity and conciseness. 
         [0019]    The features described herein may be embodied in different forms, and are not to be construed as being limited to the examples described herein. Rather, the examples described herein have been provided so that this disclosure will be thorough and complete, and will convey the full scope of the disclosure to one of ordinary skill in the art. 
         [0020]    Words describing relative spatial relationships, such as “below”, “beneath”, “under”, “lower”, “bottom”, “above”, “over”, “upper”, “top”, “left”, and “right”, may be used to conveniently describe spatial relationships of one device or elements with other devices or elements. Such words are to be interpreted as encompassing a device oriented as illustrated in the drawings, and in other orientations in use or operation. For example, an example in which a device includes a second element disposed above a first element based on the orientation of the device illustrated in the drawings also encompasses the device when the device is flipped upside down in use or operation, Regarding directions, an optical axis direction (Z axis direction) seen in  FIGS. 1-5  means upward and downward directions in relation to a lens barrel  211 . 
         [0021]    Referring to  FIGS. 1 through 3 , a camera module includes a lens module  210 , a housing  230  accommodating the lens module  210 , a lens driver  400  driving the lens module  210  and the housing  230 , a frame  300  spaced apart from the housing  230  in an optical axis direction (Z direction), and a case  100  coupled to the frame  300 . The lens module  210  includes a lens barrel  211  and a bobbin  213  in which the lens barrel  211  is mounted. The lens barrel  211  has a hollow cylindrical shape such that a plurality of lenses imaging a subject may be accommodated therein. The plurality of lenses are provided in the lens barrel  211  on an optical axis. 
         [0022]    The number of lenses stacked in the lens barrel  211  may vary according to a design of the lens module  210 . The plurality of lenses have optical characteristics such as the same or different refractive indices, or any combination thereof. 
         [0023]    The lens barrel  211  is coupled to the bobbin  213 . For example, the lens barrel  211  is fixed by being inserted into a hollow portion of the bobbin  213 . The bobbin  213  is accommodated in the housing  230  along with the lens barrel  211  and is driven along the optical axis direction (Z direction) for auto-focusing the camera module  210 . The housing  230  may be driven in directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction) for optical image stabilization (OIS) while accommodating the lens module  210  therein. In this regard, the lens module  210  and the housing  230  function as a driver  200  driven for auto-focusing and OIS. 
         [0024]    The frame  300  is spaced apart from the driver  200  in the optical axis direction (Z direction). A window is formed in the frame  300  such that light may be transmitted therethrough. 
         [0025]    A first substrate  600  in which an image sensor  610  is mounted is coupled to a lower portion of the frame  300 . The case  100  is coupled to the frame  300  to enclose the housing  230  and may function to block electromagnetic waves generated while the camera module is driven. That is, when the camera module is driven, electromagnetic waves are generated, and when electromagnetic waves are emitted externally, electromagnetic waves influence other electronic components, causing communication problems or malfunctions. The case  100  is formed of a metal material so that the case  100  may be grounded to a ground pad included in the first substrate  600 , and thus electromagnetic waves are blocked. When the case  100  is provided as a plastic molding, an inner surface of the case  100  is coated with conductive paint, and thus, electromagnetic waves are blocked. Conductive epoxy may be used as the conductive paint, but the conductive paint is not limited thereto and various conductive materials may be used. A conductive film or a conductive tape may be attached to the inner surface of the case  100 . 
         [0026]    A lens driver  400  is provided in the camera module to drive the lens module  210  in the optical axis direction (Z direction) or drive the housing  230  in the X direction and Y direction perpendicular to the optical axis direction (Z direction). The lens driver  400  includes a first coil  410 , a magnet  430 , and a second coil  450 . The first coil  410  is provided on an outer surface of the bobbin  213 , and the magnet  430  is mounted in the housing  230 , facing the first coil  410  for auto-focusing. The housing  230  is provided to have open sides such that the magnet  430  and the first coil  410  face each other. 
         [0027]    For example, the housing  230  includes a first housing  231  and a second housing  233  coupled to each other in the optical axis direction (Z direction). Each of the first housing  231  and the second housing  233  includes a rectangular support plate having a hollow, cylindrical member extending in the optical axis direction (Z direction) and formed in each corner of the support plate. Therefore, the magnet  430  is mounted in open sides of the housing  230  so that the magnet  430  faces the first coil  410  in the directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction). 
         [0028]    The magnet  430  forms a uniform magnetic field. If power is supplied to the first coil  410 , driving force is generated by an electromagnetic field between the magnet  430  and the first coil  410 . The lens module  210  may be moved by the driving force in the housing  230  in the optical axis direction (Z direction). The lens module  210  is moved by the operation described above and thus auto-focusing or a zooming function may be performed. 
         [0029]    The housing  230  includes one or more elastic, or flexible members  510  and  530  elastically supporting the bobbin  213 . For example, the first elastic member  510  is disposed in the first housing  231  to elastically support the bobbin  213 , and the second elastic member  530  is disposed below the second housing  233  to elastically support the bobbin  213 . 
         [0030]    Optical image stabilization (OIS) is used to stabilize blurring of an image or shaking of a moving image due to a factor such as user hand-shake when the image and the moving image are captured. For example, when hand-shake occurs, a relative displacement is provided to the housing  230  in the directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction), and thus hand-shake is nullified. 
         [0031]    The second coil  450  is disposed to face the magnet  430 . For example, the second coil  450  is mounted in a second substrate  700  attached to the inner surface of the case  100 , such that the second coil  450  faces the magnet  430  in the directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction). 
         [0032]    A Hall sensor (not shown) is mounted in the second substrate  700  in a location adjacent to the second coil  450  to sense a location of the magnet  430 . The magnet  430  forms a uniform magnetic field. When power is supplied to the second coil  450 , a driving force is generated by the electromagnetic influence between the magnet  430  and the second coil  450 . The housing  230  is moved by the driving force in the directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction). 
         [0033]    The lens module  210  is disposed in the housing  230 , and thus the lens module  210  may be driven through the driving of the housing  230  in the directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction). The housing  230  is moved by the operation described above, and thus an OIS function may be performed. 
         [0034]    A suspension wire  800  for supporting the driving of the housing  230  in the directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction) is provided. The suspension wire  800  has one end fixed to the first substrate  600 , and the other end fixed to the first elastic member  510  of the housing  230 . Thus, the suspension wire  800  regulates a space between the housing  230  and the frame  300  along the optical axis direction (Z direction). 
         [0035]    Four suspension wires  800 , disposed in respective corners of the frame  300 , support driving of the housing  230  when hand-shake is stabilized. 
         [0036]    The suspension wire  800  also supplies power to the first coil  410 . One end of the suspension wire  800  is fixed to the first substrate  600 , the other end thereof is fixed to the first elastic member  510 , and the first elastic member  510  is connected to a lead wire of the first coil  410 , and thus the first coil  410  may be supplied with power through the suspension wire  800 . 
         [0037]    A yoke portion  330  is mounted in an accommodation groove  310  in the frame  300 . The yoke portion  330  is mounted in the accommodation groove  310  so that the yoke portion  330  is spaced apart from the magnet  430  in the optical axis direction (Z direction). 
         [0038]    As shown in  FIG. 5 , the yoke portion  330  is disposed on a path of a closed circuit formed by a magnetic force line of the magnet  430 . In this regard, a space in which the magnetic field is present around the magnet  430  is relatively reduced by the yoke portion  330 . For example, the path of the closed circuit of the magnetic force line starting at an N pole of the magnet  430  and returning to an S pole may be reduced by the yoke portion  330 . 
         [0039]    Without the yoke portion  330 , the magnetic field of the magnet  430  is formed in a relatively large space. However, when the yoke portion  330  is provided, the magnetic field of the magnet  430  passes through the yoke portion  330 , and thus the magnetic field of the magnet  430  acts in a relatively small space. In other words, the magnetic force line starts at the N pole of the magnet  430  and returns to the S pole through the yoke portion  330 , and thus the path of the closed circuit formed by the magnetic force line is reduced. 
         [0040]    When the camera module according to an exemplary embodiment in the present disclosure is mounted in a portable electronic device such as a smartphone, the magnetic field of the magnet  430  provided in the camera module may be influenced by another magnetic material mounted in the portable electronic device. Therefore, during a driving process for OIS, the magnetic field of the magnet  430  is affected by an external magnetism, and thus the housing  230  may malfunction or may not be driven at an exact location. 
         [0041]    The camera module provides the yoke portion  330  to face the magnet  430  in the optical axis direction (Z direction) to allow the magnetic field of the magnet  430  to be formed in a relatively small space, thereby reducing an influence of external magnetism when driving for OIS. The yoke  430  provides a magnetic pulling power between the magnet  430  and the yoke portion  330  in the optical axis direction (Z direction). For example, the yoke portion  330  mounted in the frame  300  comprises a magnetic or metallic substance, and thus the magnetic interactions may occur between the magnet  430  and the yoke portion  330 . The yoke portion  330  is fixed to the frame  300  through the coupling groove  310 , and thus the magnet  430  may be pulled in a direction toward the yoke portion  330  by the magnetic pulling power. 
         [0042]    Accordingly, the housing  230  in which the magnet  430  is mounted may be pulled in a direction toward the frame  300  in which the yoke portion  330  is mounted. Thus, even in the case that an external shock, such as a hand shake, is generated, the space between the frame  300  and the housing  230  is maintained, and thus the camera module reliability is increased. 
         [0043]    The arrangement of the lens driver  400  and the yoke portion will be described with reference to  FIGS. 4 and 5 . 
         [0044]    As described above, the lens driver  400  includes the first coil  410 , the magnet  430 , and the second coil  450 . The first coil  410  is wound on an outer surface of the bobbin  213  in one direction. The magnet  430  is mounted in the housing  230  to face the first coil  410  in the directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction). 
         [0045]    The second coil  450  is provided in a toroidal shape having a hollow center and is mounted in the second substrate  700  provided in an inner surface of the case  100  such that the second coil  450  faces the magnet  430  in the directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction). 
         [0046]    Thus, as shown in  FIG. 4 , the magnet  430  is disposed between the first coil  410  and the second coil  450  and includes a first surface  431  facing the first coil  410  and a second surface  433  facing the second coil  450 . 
         [0047]    The magnet  430  is used in both driving for auto-focusing and driving for OIS. For example, a magnet for auto-focusing and a magnet for OIS are not separately provided to the lens driver  400 , but the magnet  430  is used in both auto-focusing and OIS, thereby reducing the size of a small camera module. That is, the lens driver  400  may implement both auto-focusing and OIS functions, and thus the number of components for implementing auto-focusing and OIS functions may be reduced, thereby making the camera module smaller. 
         [0048]    Referring to  FIG. 5 , the first surface  431  and the second surface  433  of the magnet  430  have different poles. For example, the first surface  431  of the magnet  430  has an S pole, and the second surface  433  of the magnet  430  has an N pole. First, a direction of an electromagnetic force Fz by an interaction between the first coil  410  and the magnet  430  during auto-focusing driving will be described. 
         [0049]    A magnetic field B of the magnet  430  interacts with the first coil  410  in the X direction. In this regard, if power is supplied to the first coil  410 , current I flows in the Y direction, a direction (X direction) of the magnetic field B of the magnet  430  and a direction (Y direction) in which the current I flows in the first coil  410  are orthogonal to each other, and thus the electromagnetic force Fz acts in the Z direction through interaction between the first coil  410  and the magnet  430 . Therefore, the lens module  210  may be driven in the optical axis direction (Z direction) by the first coil  410  and the magnet  430 . 
         [0050]    Next, a direction of an electromagnetic force Fx by an interaction between the second coil  450  and the magnet  430  during OIS driving will be described. The magnetic field B of the magnet  430  interacts with the second coil  450  in the Z direction. In this regard, if power is supplied to the second coil  450 , the current I flows in the Y direction, a direction (Z direction) of the magnetic field B of the magnet  430  and a direction (Y direction) in which the current I flows in the second coil  450  are orthogonal to each other, and thus the electromagnetic force Fx by the interaction between the second coil  450  and the magnet  430  acts in the X direction. Therefore, the housing  230  may be driven in the directions (X direction and Y direction) perpendicular to the optical axis direction (Z direction) by the second coil  450  and the magnet  430 . 
         [0051]    Although the electromagnetic force Fx is described as acting in the X direction during OIS driving, for convenience of description, the electromagnetic force Fy acts similarly in the Y direction through an interaction between the magnet  430  another a coil  450  on another portion of the second substrate  700 , as shown in  FIGS. 2 and 4 . 
         [0052]    As shown in  FIGS. 2-4 , the yoke portion  330  is disposed to be spaced apart from the magnet  430  along the optical axis direction (Z direction). A magnetic force line, or magnetic flux, of the magnet  430  passes through the yoke portion  330 , and thus a closed circuit path formed by the magnetic force line of the magnet  430  is reduced. In other words, the distance in which the magnetic field extends, is reduced. 
         [0053]    Without the yoke portion  330  (an upper side of the Z direction in  FIG. 5 ), the magnetic field of the magnet  430  acts in a relatively large space, whereas when the yoke portion  330  is provided (a lower side of the Z direction in  FIG. 5 ), the magnetic field of the magnet  430  passes through the yoke portion  330 , and thus the magnetic field of the magnet  430  acts in a relatively small space. Therefore, an influence of external magnetism may be reduced during driving for OIS. 
         [0054]    A magnetic flux of the magnet  430  is focused on the first coil  410  and the second coil  450  by the yoke portion  330 , thereby smoothly driving auto-focusing and OIS. Although the yoke portion  330  is disposed in the lower side of the magnet  430  in the Z direction in  FIG. 5 , the yoke portion  330  may be disposed on the upper and lower sides of the magnet  430  in the Z direction. As set forth above, the camera module reduces an influence on external magnetism and improve driving reliability for auto-focusing and OIS. 
         [0055]    As a non-exhaustive example only, a mobile communication terminal as described herein may be a mobile device, such as a cellular phone, a smart phone, a wearable smart device (such as a ring, a watch, a pair of glasses, a bracelet, an ankle bracelet, a belt, a necklace, an earring, a headband, a helmet, or a device embedded in clothing), a portable personal computer (PC) (such as a laptop, a notebook, a subnotebook, a netbook, or an ultra-mobile PC (UMPC), a tablet PC (tablet), a phablet, a personal digital assistant (PDA), a digital camera, a portable game console, an MP3 player, a portable/personal multimedia player (PMP), a handheld e-book, a global positioning system (GPS) navigation device, or a sensor, or a stationary device, such as a desktop PC, a high-definition television (HDTV), a DVD player, a Blu-ray player, a set-top box, or a home appliance, or any other mobile or stationary device capable of wireless or network communication. In one example, a wearable device is a device that is designed to be mountable directly on the body of the user, such as a pair of glasses or a bracelet. In another example, a wearable device is any device that is mounted on the body of the user using an attaching device, such as a smart phone or a tablet attached to the arm of a user using an armband, or hung around the neck of the user using a lanyard. 
         [0056]    While this disclosure includes specific examples, it will be apparent to one of ordinary skill in the art that various changes in form and details may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered in a descriptive sense only, and not for purposes of limitation. Descriptions of features or aspects in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined in a different manner, and/or replaced or supplemented by other components or their equivalents. Therefore, the scope of the disclosure is defined not by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be construed as being included in the disclosure.