Abstract:
A camera module ( 10 ), includes a lens holder ( 12 ) having an aperture ( 1202 ), at least one lens module ( 11 ) threadedly installed in the lens holder, and a motor ( 13 ) mounted on the lens holder. The motor includes a rotor ( 132 ) and an endless belt ( 14 ), wherein the endless belt extends through the aperture and surrounds the lens module, and the rotor. The motor is configured for driving the lens module to move relative to the lens holder.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to camera modules, and particularly to a camera module with an auto focus mechanism. 
         [0003]    2. Description of Related Art 
         [0004]    In recent years, camera modules for taking photos have been incorporated in mobile terminals, such as mobile phones and lap-top computers. Most mobile terminals devices are, progressively becoming more miniaturized over time, and digital camera modules are, correspondingly, becoming smaller and smaller. Nevertheless, in spite of the small size of a contemporary digital camera module, consumer still demands advantageous properties of the camera module, such as auto focus function. 
         [0005]    A camera module generally includes at least one lens module and an image sensor module in alignment with the at least one lens module. The at least one lens module typically includes a lens barrel and lenses assembled in the lens barrel. Recently, camera modules have employed auto focus mechanisms, such as step motors for driving the lenses by screws to move relative to the image sensor module, thereby achieving the auto focus function. However, the total length required for such camera module is so large that the size reduction requirement of the camera module is not easy to be satisfied. 
         [0006]    What is needed, therefore, is a camera module which has a simple and small sized auto focus mechanism. 
       SUMMARY 
       [0007]    In a present embodiment, a camera module, includes a lens holder having an aperture, at least one lens module threadedly installed in the lens holder, and a motor mounted on the lens holder. The motor includes a rotor and an endless belt, wherein the endless belt extends through the aperture and surrounds the lens module, and the rotor. The motor is configured for driving the lens module to move relative to the lens holder. 
         [0008]    Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Many aspects of the lens module can be better understood with reference to the following drawings. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present lens module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0010]      FIG. 1  is a perspective view of a camera module according to a first embodiment of the present invention. 
           [0011]      FIG. 2  is a cross-sectional view taken along line II-II of  FIG. 1 . 
           [0012]      FIG. 3  is a schematic, cross-sectional view of a camera module according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    Embodiments of the present lens module will now be described in detail below and with reference to the drawings. 
         [0014]    Referring to  FIGS. 1 and 2 , an exemplary camera module  10  according to a first embodiment includes a first lens module  11 , an image sensor module  12  for detecting light from the first lens module  11 , a first motor  13 , and a first endless belt  14 . 
         [0015]    The first lens module  11  includes a first lens barrel  110  and at least one first lens  112 . In the illustrated embodiment, the first lens module  11  includes a first lens  112 . It is to be understood that lenses of any number and type could be used in the first lens barrel  110 . The first lens barrel  110  is substantially a hollow cylinder. The first lens barrel  110  has outer threads  1102  on an outer wall thereof. The first lens  112  is engagingly received in the first lens barrel  110 . The first lens  112  has an optical axis OO′. 
         [0016]    The image sensor module  12  includes a lens holder  120  and an image sensor  122 . The lens holder  120  has inner threads  1200  at an inner wall thereof, thus facilitating engagement with the outer threads  1102  of the first lens barrel  110 . The image sensor  122  is received in the bottom portion of the lens holder  120  facing the first lens  112 . The image sensor  122  is selected from a charge coupled device (CCD) and a complementary metal oxide semiconductor transistor (CMOS). 
         [0017]    The first motor  13  is attached to the lens holder  120 . In the present embodiment, the first motor  13  is a step motor. The first motor  13  includes a first body  130  and a first rotor  132  attached to the first body  130 . The first rotor  132  can rotate relative to the first body  130 . In the present embodiment, the first body  130  and the first rotor  132  are substantially cylinders. It is to be understood that, the shape of the first body  130  and first rotor  132  also can be any types, such as cubic or prismoid. The first rotor  132  has at least one first rotor slot  1320  defined in the outer cylinder surface of the first rotor  132 . The rotating axis L of the first rotor  132  is parallel to the optical axis OO′ of the first lens module  11 . 
         [0018]    In the present embodiment, at least one first annular groove  1104  is defined in the outer wall of the first lens barrel  110 . A first aperture  1202  is defined in the sidewall of the lens holder  120 . The first annular groove  1104 , the first aperture  1202 , and the first rotor slot  1320  are substantially coplanar with each other. Part of the first endless belt  14  is fitted around the first lens barrel  110  and embedded in the first annular groove  1104 , and another part of the first endless belt  14  passes through the first aperture  1202  of the lens holder  120  and is fitted around the first rotor  132  and embedded in the first rotor slot  1320 . 
         [0019]    In operation, when a change of the focal length of the first lens module  11  is desired, a voltage may be applied to the first motor  13 . The first rotor  132  is driven by the first motor  13  to rotate. Due to the friction force between the first endless belt  14  and the first rotor  132 , the first endless belt  14  is rotated with the first rotor  132 . Due to the friction force between the first endless belt  14  and the first annular groove  1104  in the first lens barrel  110 , the first lens barrel  110  is rotated with the first endless belt  14 . The lens barrel  11  can be rotated in or out of the lens holder  120 , such that the first lens  112  moves relative to the image sensor device  122 . Thereby, the internal spacing between the first lens  112  and the image sensor  122  is changed, and the focal length of the camera module  10  is adjusted. The adjusting range of the focal length of the camera module  10  may be configured to be proportional to the number of the turns of the first rotor  132 . That is, the focal length of the camera module  10  can be adjusted continuously. 
         [0020]    It is to be understood that, the camera module  10  can includes more lens modules to provide better optical performance. 
         [0021]    Referring to  FIG. 3 , an exemplary camera module  10   a  according to a second embodiment includes a first lens module  11 , an image sensor module  12  for detecting light from the first lens module  11 , a first motor  13 , and a first endless belt  14 . The difference with the camera module  10  in the first embodiment is that the camera module  10   a  further includes a second lens module  11   a,  a second motor  13   a,  and a second endless belt  14   a.    
         [0022]    The second lens module  11   a  includes a second lens barrel  110   a,  a second lens  112   a  received in the second lens barrel  110   a.  The first lens barrel  110  and the second lens barrel  110   a  are optically aligned with each other and engagingly received in the lens holder  120  by threads  1102 ,  1102   a  at the outer wall thereof. In the present embodiment, the second lens barrel  110   a  is disposed between the first lens barrel  110  and the image sensor  122 . It is to be understood that, the first lens barrel  110  can also be disposed between the second lens barrel  110   a  and the image sensor  122 . 
         [0023]    The second motor  13   a  is attached to the lens holder  120  and spaced from the first motor  13 . The second motor  13   a  includes a second body  130   a  and a second rotor  132   a  attached to the second body  130   a.  In the present embodiment, the second body  130   a  and the second rotor  132   a  are substantially cylinders. The second rotor  132   a  has at least one second rotor slot  1320   a  defined in the outer cylinder surface of the second rotor  132   a.  The rotating axis M of the second rotor  132   a  is parallel to the optical axis OO′ of the second lens module  11   a.    
         [0024]    In the present embodiment, at least one second annular groove  1104   a  is defined in the outer wall of the second lens barrel  110   a.  A second aperture  1202   a  is defined in the sidewall of the lens holder  120 . The second annular groove  1104   a,  the second aperture  1202   a,  and the second rotor slot  1320   a  are substantially coplanar with each other. Part of the second endless belt  14   a  is fitted around the first endless belt  14   a  passes through the second aperture  1202   a  of the lens holder  120   a  and is fitted around the second rotor  132   a  and embedded in the second rotor slot  1320   a.    
         [0025]    In operation, the internal spacing between the first lens  112 , the second lens  112   a,  and the image sensor device  122  can be adjusted by the first motor  13  and the second motor  13   a.  The adjusting range of the focal length of the camera module  10   a  may be configured to be proportional to the number of the turns of the first rotor  132  and the second rotor  132   a.  Thereby, the camera module  10   a  can achieved auto focusing or auto zooming functions. A height of each of the first motor  13  and the second motor  13   a,  can be designed according to the total length required for the lens modules. 
         [0026]    It is understood that the above-described embodiments are intended to illustrate rather than limit the invention. Variations may be made to the embodiments and methods without departing from the spirit of the invention. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.