Abstract:
A digital camera module ( 100 ) includes a lens barrel ( 20 ), a lens holder ( 22 ), an image pick-up module ( 26 ), and a protective member. The lens barrel defines a central hollow, and has at least one lens ( 202 ) received therein. The lens holder defines a central hollow. The lens barrel is movably received in the lens holder along an axis of the lens holder. The image pick-up module is arranged to receive light from the lenses. The protective member is configured for preventing dust and/or particle contamination associated with a relative movement of the lens barrel and the lens holder falling onto the image pick-up module.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to digital camera modules and, more particularly, to a digital camera module which improves image quality. 
     2. Discussion of the Related Art 
     Generally, digital cameras are image recording media capable of photographing a plurality of still images without using film. Such a digital camera typically uses an image pickup device, which is a kind of semiconductor device, such as a charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS). In the digital camera, an object image formed on the image pickup device through a lens is converted into an electrical signal by the image pickup device, and the electrical signal is stored as a digital signal in a mobile phone or PDA in which the digital camera is mounted. 
     A digital camera module, as shown in  FIG. 3 , a lens barrel  10 , a lens holder  12 , and an image pick-up module  14 . The lens barrel  10  has an external thread  102 , and the lens holder  12  has an internal thread  122 . The lens barrel  10  is received in the lens holder  12  via the thread engagement between the external thread  102  and the internal thread  122 . The image pick-up module  14  includes a base plate  142  and an image pick-up chip  144 . The lens holder  12  is fixed on the base plate  142 . During auto focusing, a distance between the lens barrel  10  and the image pick-up chip  144  is slightly adjusted to make the digital camera module focus by means of adjusting the thread engagement of the internal thread  122  of the lens holder  12  and the external thread  102  of the lens barrel  10 . Lastly, the lens holder  12  is secured on the base plate  142  via adhesive. 
     However, dust and/or particle pollution/contamination associated with friction between the lens barrel  10  and the lens holder  12  may fall onto the image pick-up chip  144 , thus affecting image quality of the digital camera module. 
     What is needed, therefore, is a digital camera module which overcomes the above-described problem. 
     SUMMARY OF THE INVENTION 
     A digital camera module comprises a lens barrel, a lens holder, an image pick-up module, and a protective member. The lens barrel is hollow, and has at least one lens received therein. The lens holder is hollow. The lens barrel is movably received in the lens holder along an axis of the lens holder. The image pick-up module is arranged to receive a light from the lenses. The protective member is configured for preventing dust and/or particles associated by friction between the lens barrel and the lens holder falling onto the image pick-up module. 
     Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the digital camera module 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 digital camera module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a schematic view of a digital camera module, in accordance with a first exemplary embodiment. 
         FIG. 2  is a schematic view of a digital camera module, in accordance with a second exemplary embodiment. 
         FIG. 3  is an schematic view of a typical digital camera module. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings,  FIG. 1  shows a digital camera module  100  according to a first preferred embodiment. The digital camera module  100  is adapted for use in a portable electronic device (not shown), such as a mobile phone or a Personal Digital Assistance (PDA), but the compact nature thereof could prove useful in compact digital camera units or digital camcorders. The digital camera module  100  includes a lens barrel  20 , a lens holder  22 , a ring member  24  as a protective member, and an image pick-up module  26 . 
     The lens barrel  20  is a hollow cylinder in shape, with two open ends so that light can be transmitted therethrough. The lens barrel  20  has a plurality of lenses  202  (only one shown) received therein. The lens barrel  20  has an external thread  204  defined in an outer periphery thereof. 
     The lens holder  22  is a hollow cylinder with two open ends allowing light to be transmitted therethrough. The lens holder  22  has a raised lip  222  projecting from middle portion of an inner periphery thereof. The lens holder  22  has an internal thread  224  defined in an inner periphery thereof, corresponding to the external thread  204  of the lens barrel  20 . 
     The ring member  24  is annular in shape, and supported by the raised lip  222  of the lens holder  22 . 
     The image pick-up module  26  includes a base plate  27 , an adhesive means  28 , an image pick-up chip  29 , and a plurality of bonding wires  30 . The base plate  27  is made of a material such as a plastic, a ceramic or a fibrous composite. The base plate  27  has a plurality of top pads  271  on a top surface, a plurality of bottom pads  272  on a bottom surface thereof. The bottom pads  272  are positioned corresponding to and electrically connecting with the respective top pads  271 . The base plate  27  is used for electrically connecting the image pick-up chip  29  to other printed circuit boards. 
     The image pick-up chip  29  is adhered to the top surface of the base plate  27  via the adhesive means  28 . A top side of the image pick-up chip  29  is arranged with a photosensitive area  291  and a plurality of chip pads  292  around the photosensitive area  291 . 
     The bonding wires  30  are made of a conductive material such as gold or aluminum alloy. One end of each bonding wire  30  is connected/joined with a respective chip pad  292  of the image pick-up chip  29 , and the other end of the bonding wires  30  is connected/joined with a respective top pad  271  of the base plate  27 . 
     In assembling the digital camera module  100 , the ring member  24  is received in the lens holder  22  via an open end of the lens holder  22 , and supported by the raised lip  222 . Then, the lens barrel  20  is placed in the lens holder  22 , with the external thread  204  of the lens barrel  20  engaging with the internal thread  224  of the lens holder  22 . Then, the lens holder  22  is fixed on the image pick-up module  24 , with the image pick-up chip  29  received in the lens holder  22  and the lens holder secured on the base plate  27 . During auto focusing, a distance between the lens barrel  20  and the image pick-up chip  29  can be adjusted to focus the digital camera module  100  by adjusting the thread engagement of the external thread  204  of the lens barrel  20  and the internal thread  224  of the lens holder  22 . 
     In the first embodiment, since the ring member  24  is disposed between the lens barrel  20  and the lens holder  22 , dust and/or particle pollution/contamination associated with friction between the lens barrel  20  and the lens holder  22  can be effectively prevented from entering the image pick-up module  26 . In addition, the ring member  24  may be tightly sandwiched between the lens barrel  20  and the lens holder  22 . 
     Referring to  FIG. 2 , another digital camera module  200  according to a second preferred embodiment is provided. The digital camera module  200  includes a lens barrel  40 , a lens holder  42 , a ring member  44  as a protective member, and an image pick-up module  46 . The image pick-up module  46  is similar to the image pick-up module  26  of the first embodiment, and include a base plate  47 , and an image pick-up chip  49  disposed on the base plate  47 . 
     The lens barrel  40  is a hollow cylinder in shape with two open ends so that light can be transmitted therethrough. The lens barrel  40  includes a first cylinder portion  402 , and a second cylinder portion  404  integrally formed with the first cylinder portion  402 . An inner diameter of the first cylinder portion  402  is smaller than that of the second cylinder portion  404 . The first cylinder portion  402  has a plurality of lenses  406  (only one shown) received therein. The second portion  404  has an internal thread  408  defined in an inner periphery thereof. 
     The lens holder  42  is a hollow cylinder with two open ends so that light can be transmitted therethrough. The lens holder  42  has a projecting stage  422  projecting from outer periphery thereof adjacent a bottom thereof. The lens holder  42  has an external thread  424  defined in an outer periphery thereof, corresponding to the internal thread  408  of the lens barrel  40 . 
     The ring member  44  is ring-shaped, and disposed on a top surface  426  of the lens holder  42 . The ring member  24  is tightly sandwiched between the lens barrel  40  and the top surface  426  of the lens holder  42 . 
     In assembling the digital camera module  200 , the protective member  44  is disposed on the top surface  426  of the lens holder  42 . The lens barrel  40  is placed around the lens holder  42 , with the internal thread  408  engaging with the external thread  424  of the lens holder  42 . Then, the lens holder  42  is fixed on the image pick-up module  46 , with the image pick-up chip  49  of the image pick-up module  46  received in the lens holder  42  and the lens holder secured on the base plate  47 . During auto focusing, a distance between the lens barrel  40  and the image pick-up chip  49  is adjusted to focus the digital camera module  200  by adjusting the thread engagement of the external thread  408  of the lens barrel  40  and the internal thread  424  of the lens holder  42 . 
     In the second embodiment, since a protective member  40  is disposed between the lens barrel  40  and the top surface of the lens holder  42 , dust and/or particle pollution/contamination in associated with friction between the lens barrel  40  and the lens holder  42  can be effectively prevented entering the image pick-up module  46 . In addition, the thread engagement between the lens barrel  40  and the lens holder  42  disposed on an outer periphery of the lens holder  42  on the image pick-up chip  49  can also prevent particle or dust from falling onto the image pick-up chip  49 , thus improving image quality of the digital camera module. 
     In alternative embodiment, the protective member may be a circular washer, or other member of other shape having a hole in a center thereof such that a light from the lenses can be transmitted through the protective member to the image pick-up module. An outer diameter of the protective member may be equal to an inner diameter of the lens holder. The protective member may be integrally formed with the lens holder. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.