Abstract:
A camera module includes a lens holder, a lens held by the lens holder, an image sensor, a guiding device, and a driving motor. The lens holder includes guiding rods which impose a movement track on the guiding device so as to hold the image sensor very steadily and precisely for focusing purposes, in moving towards or away from the lens.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to camera modules and, particularly, to a camera module having a movable image sensor for focusing. 
         [0003]    2. Description of Related Art 
         [0004]    Camera modules include a lens and an image sensor aligned with the lens. Current cameras focus by driving the image sensor to move in relation to the lens. However, the image sensor may move out of alignment when being driven to move by a current driving system and degrade preview image quality, thus adversely affecting the focusing. 
         [0005]    Therefore, it is desirable to provide a camera module, which can overcome the above-mentioned problems. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. 
           [0007]      FIG. 1  is an isometric schematic view of a camera module, according to an embodiment. 
           [0008]      FIG. 2  is an exploded view of the camera module of  FIG. 1 . 
           [0009]      FIG. 3  is a cross-sectional view of the camera module of  FIG. 1 . 
           [0010]      FIG. 4  is a cut-away view of the camera module of  FIG. 1 . 
           [0011]      FIG. 5  is a partial, enlarged view of the camera module of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIGS. 1-3 , a camera module  10 , according to an embodiment, includes a lens  122 , an image sensor  124 , a printed circuit board  126 , a filter assembly  128 , a lens holder  14 , a guiding device  16 , and an activating device  18 . 
         [0013]    The image sensor  124  is positioned on and electrically connected to the printed circuit board  126 . The filter assembly  128  includes a filter  1282  and is fixed to the printed circuit board  126  such that the filter  1282  covers the image sensor  124 . In other embodiments, the filter assembly can be omitted. 
         [0014]    The lens holder  14  includes a upper plate  141  and defines a through hole  142  running through a center of the upper plate  141 . The upper plate  141  has an inner surface  143 . The lens holder  14  includes a number of reinforced short sockets  146  and a number of reinforced long sockets  147  extending upward from the inner surface  143  and surrounding the through hole  142 . The lens holder  14  also includes a number of guiding rods  144  and a number of fixing devices  148 . Each guiding rod  144  is inserted into one of the short sockets  146 . Each fixing device  148  includes a fixing portion  1481 , a first screw  1482 , and a fixing cap  1484 . The first screw  1482  is screwed through the fixing portion  1481  into one of the long sockets  147  to fix the fixing portion  1481  on the long socket  147 . The fixing cap  1484  is integrally formed with the fixing portion  1481  and caps one of the guiding rods  144 . Thus, the guiding rods  144  are fixed to the lens holder  14 . 
         [0015]    The lens  122  is held by the lens holder  14  by inserting the lens  122  into the through hole  142 . An optical axis of the lens  122  is substantially perpendicular to the inner surface  141 . 
         [0016]    The guiding device  16  includes a base  162  and a number of guiding tubes  1620 . The guiding tubes  1620  are fixed to an outer periphery of the base  162  and are slidable on the guiding rods  144 . As such, the base  162  can slide substantially along the guiding rods  144 . A sidewall of each guiding tube  1620  has cutouts of material to reduce a contact surface between the guiding tube  1620  and the guiding rod  144 , reducing friction therebetween. 
         [0017]    In this embodiment, numbers of the guiding rods  144 , the short sockets  146 , the long sockets  147 , the fixing devices  148 , and the guiding tubes  1620  are two but can be changed to more than two in other embodiments. 
         [0018]    In other embodiments, the guiding rods  144  can be arranged to be perpendicular to the inner surface  143  by methods other than the method of this embodiment. For example, the guiding rods  144  can extend up from the inner surface  143  directly. 
         [0019]    The base  162  includes a first surface  1621  and a second surface  1622  opposite the first surface  1621 . The first surface  1621  faces and is substantially parallel to the inner surface  143 . 
         [0020]    The guiding device  16  includes a number of sleeves  1623 , a number of coil springs  1627 , and a number of second screws  1625 . The printed circuit board  126  is fixed above the base  1620  by threadedly inserting the second screws  1625  through the base  162 , the sleeves  1623 , and into the printed circuit board  126 . The image sensor  124  is at a side of the printed circuit board  126  opposite to the base  162  and faces the lens  122 . The coil springs  1627  sleeve on the sleeves  1623  and are compressed between the base  162  and the printed circuit board  126 . As such, by screwing the second screws  1626 , the printed circuit board  126  can be adjusted to be precisely parallel with the first surface  1621  such that the optical axis of the lens  122  is substantially perpendicular to the image sensor  124 . The image sensor  124  is movable in relation to the lens  122  when the guiding tubes  1620  slide on the guiding rod  144 . 
         [0021]    In other embodiments, the printed circuit board  126  can be fixed to the base  162  by methods other than the method of this embodiment. For example, the printed circuit board can be fixed to the base  162  directly. 
         [0022]    In this embodiment, the number of the sleeves  1623 , of the second screws  1626 , and of the coil springs  1627  are all three but can be changed in other embodiments. 
         [0023]    Also referring to  FIG. 4 , the guiding device  16  also includes an engagement block  1624  and a shaft  1626 . The engagement block  1624  is rotatably arranged on the second surface  1622  by the shaft  1626 . The shaft  1626  is substantially perpendicular to the second surface  1626 . The engagement block  1624  defines a groove  1624   b  extending along a direction that is substantially perpendicular to the second surface  1622  and teeth  1624   a  are formed on a sidewall of the groove  1624   b.  The activating device  18  includes a seat  181 , a motor  182 , and a threaded rod  184 . The seat  181  is fixed to the lens holder  14  by screws (not labeled). The motor  182  is seated on the seat  181  by screws (not labeled) and drives the threaded rod  184  to rotate. The threaded rod  184  is substantially perpendicular to the second surface  1622  and engages with the teeth  1624   a.  Thus, the engagement block  1624  can be driven along the threaded rod  184 . As a consequence, the base  162  along with the image sensor  124  move in a direction that is substantially parallel with the optical axis of the lens  122 , to focus the camera module  10 . 
         [0024]    The guiding device  16  further includes a torsion spring  1628 . The torsion spring  1628  has a central coil portion  1628   c  and two distal ends  1628   a,    1628   b.  The coil portion  1628   c  is sleeved on the shaft  1626  and the two distal ends  1628   a,    1628   b  abut against the base  162  and the engagement block  1624  to remove slack or play between the teeth  1624   a  and the threaded rod  184 . 
         [0025]    Referring to  FIG. 5 , the camera module  10  also includes a position sensor  19 . The position sensor  19  includes a photoelectric assembly  192  and a barrier plate  194 . The photoelectric assembly  192  includes a carrier block  1921  which is secured to the seat  181  and defines a slot  1922  which extends along a direction that is substantially perpendicular to the second surface  1622 . The photoelectric assembly  192  also includes a light emitter  1923  and a light receiver  1924  fixed to opposite sidewalls of the slot  1922 . The light receiver  1923  receives light emitted from the light emitter  1923 . The barrier plate  194  is fixed to the base  162 , extending along a direction that is substantially perpendicular to the second surface  1622  and positioned in the slot  1922 . As such, when the base  16  is driven to move towards the light emitter  1923  and the light receiver  1924  by the activating device  18 , the barrier plate  194  interposes itself between the light emitter  1923  and the light receiver  1924  thus reducing optical communication between the two. A position of the image sensor  124  when the carrier plate  194  starts to interpose itself between the light emitter  1923  and the light receiver  1924  is defined as an initial position. The position sensor  19  detects the initial position. 
         [0026]    It will be understood that the above particular embodiments are shown and described by way of illustration only. The principles and the features of the present disclosure may be employed in various and numerous embodiment thereof without departing from the scope of the disclosure as claimed. The above-described embodiments illustrate the possible scope of the disclosure but do not restrict the scope of the disclosure.