Abstract:
A lens module ( 20 ) is adapted for use in a digital camera. A lens module includes a lens barrel ( 21 ), a plurality of lenses including a first lens ( 22 ) and a second lens ( 23 ) and an aligning mechanism. The two lenses received in the lens barrel. The aligning mechanism an aligning mechanism configured to align respective optical axes of the first and second lenses with each othe. The aligning mechanism is disposed between the two lenses.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to lens modules, and, more particularly, to a lens module for a digital camera.  
       DESCRIPTION OF RELATED ART  
       [0002]     Currently, digital camera modules are in widespread use in a variety of portable electronic devices. Most portable electronic devices are becoming progressively more miniaturized over time, and digital camera modules are correspondingly becoming smaller and smaller. For example, digital camera modules are now widely available as a feature of a mobile phone. Nevertheless, in spite of the small size of a contemporary digital camera module, consumers still demand excellent imaging. The quality of the image provided is mainly dependent upon the optical elements of the digital camera module.  
         [0003]     Referring to  FIG. 4 , a contemporary lens module  10  for a digital camera generally includes a lens barrel  11 , a plurality of lenses  12 ,  13 , a plurality of spacers  14 ,  15 , and an IR-cut filter  16 . The lens barrel  11  is a hollow cylinder for receiving the lenses  12 ,  13 , the spacers  14 ,  15 , and the IR-cut filter  16  therein. The spacers  14 ,  15  are annular shaped. In assembly, the lenses  12 ,  13  and the spacers  14 ,  15  are arranged in the lens barrel  11  in an alternating fashion. The lenses  12 ,  13  are adhered to the inside of the lens barrel  11 . Each spacer has a thickness that defines a desired distance between the lenses  12 ,  13 . The IR-cut filer  16  is disposed at the bottom of the lens barrel. The optical axes of the lenses  12 ,  13  are aligned by means of a round tolerance of the inner wall of the lens barrel  11  and configuration of the spacers  14 ,  15 .  
         [0004]     However, because different plastics have about a 0.5 percent to 0.6 percent contraction factor during the injection molding process, precisely matching the inner diameter of the lens barrel  11  to provide the greatest effect for optical axes alignment is difficult. Further, the round tolerance of the lens barrel  11  may not meet a desired requirement or the axis of the lens barrel  11  may not be able to be aligned with the optical axis of the lenses  12 ,  13 . Although spacers  14 ,  15  are adopted, they do not overcome the above-mentioned deficiencies. Furthermore, though alignment may be obtained initially this can be lost over time due to the imprecise assembly. That is, the optical axes of the plurality of lenses  12 ,  13  may become misaligned.  
         [0005]     What is needed, therefore, is a lens module for a digital camera, which satisfies the needs for convenient assembly and accurate, long lasting alignment of optical axes of lenses.  
       SUMMARY OF INVENTION  
       [0006]     A lens module is adapted for use in a digital camera. The lens module includes a lens barrel, two lenses and an aligning mechanism. The two lenses received in the lens barrel. The aligning mechanism is adapted to align optical axes of the two lenses, and is disposed between the two lenses.  
         [0007]     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 DRAWINGS  
       [0008]     Many aspects of the lens module can be better understood with reference to the following drawings. The components in the drawings are not necessarily 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.  
         [0009]      FIG. 1  is a schematic view of a lens module for a digital camera, in accordance with a first preferred embodiment, the lens module including lenses;  
         [0010]      FIG. 2  is a schematic view of the lenses of  FIG. 1 ;  
         [0011]      FIG. 3  is a schematic view of a lens module for a digital camera, in accordance with a second preferred embodiment; and  
         [0012]      FIG. 4  is a schematic view of a conventional lens module for a digital camera. 
     
    
     DETAILED DESCRIPTION  
       [0013]     Referring now to the drawings,  FIG. 1  shows a lens module  20  for a digital camera, according to a first preferred embodiment. The lens module  20  is adapted for use in digital cameras used in portable electronic devices such as a mobile phones or Personal Digital Assistants (PDAs), but the compact nature thereof could prove useful in compact digital camera units or digital camcorders, as well. The lens module  20  includes a lens barrel  21 , a first lens  22 , a second lens  23 , a spacer  24  functioning as an aligning mechanism, and an IR-cut filter  25 . The first lens  22 , the spacer  24 , the second lens  23 , and the IR-cut filter  25  are received in the lens barrel  21  in that order.  
         [0014]     The lens barrel  21  is a hollow cylinder with an open end  212  and a half-closed (i.e., partially-closed) end  214 . The lens barrel  21  defines a cone-shaped hole  216  in the center of the half-closed end  214  so that light beams can be transmitted therethrough.  
         [0015]     The first lens  22  and the second lens  23  are both used to focus the incident light. The first lens  22  and the second lens  23  are circular. The outer diameters of the first lens  22  and the second lens  23  correspond to the inner diameter of the lens barrel  21 .  
         [0016]     The first lens  22  has an outer peripheral surface  221 , a top mounting surface  223 , and a bottom mounting surface  224 . The first lens  22  has a meniscus central portion, which defines two opposite top and bottom aspheric surfaces (not shown) respectively. The bottom aspheric surface of the first lens  22  is concave. The first lens  22  has an annular groove  225  defined in the bottom mounting surface  224 , by a groove peripheral surface  226  and a groove bottom surface  227 .  
         [0017]     The second lens  23  has an outer peripheral surface  231 , a top mounting surface  233  and a bottom mounting surface  234 . The second lens  23  has a central portion, which defines two opposite top and bottom aspheric surfaces (not shown) respectively. The top and bottom aspheric surfaces protrude outwardly. The second lens  23  has an annular groove  235  defined in the top mounting surface  233 , by a groove peripheral surface  236  and a groove bottom surface  237 . The optical axis of the annular groove  225  of the first lens  22  and the annular groove  235  of the second lens  23  are aligned with the optical axis of the first lens  22  and the second lens  23 . An outer diameter of the annular groove  225  of the first lens  22  is same as that of the annular groove  235  of the second lens  23 .  
         [0018]     The spacer  24  is annular shaped , and received in the lens barrel  21 . The spacer  24  is disposed between the first lens  22  and the second lens  23 . An outer diameter of the spacer  24  is same as or slightly greater than an outer diameter of the annular grooves  225 ,  235 , and an inner diameter of the spacer  24  is equal to or slightly smaller than an inner diameter of the annular grooves  225 ,  235 . One surface of the spacer  24  resists the bottom surface  227  of the annular groove  225  of the first lens  22 , an opposite surface of the spacer  24  resists the bottom surface  237  of the annular groove  235  of the second lens  23 .  
         [0019]     The IR-cut filter  25  can prevent incident infrared light rays from reaching an image pick-up sensor in the digital camera. The IR-cut filter  25  is received in the bottom of the lens barrel  21 .  
         [0020]     Referring now to  FIG. 2 , in assembling the lens module  20 , the first lens  22  is inserted into the lens barrel  21  via the open end  212  of the lens barrel  21 . The outer peripheral surface  221  tightly engages with an inner peripheral surface  218  of the lens barrel  21 . Then, the spacer  24  is received into the lens barrel  21  via the open end  212  of the lens barrel  21 , and inserted into the annular groove  225  of the first lens  22 . An outer peripheral surface of the spacer  24  tightly engages with the inner peripheral surface  226  of the first lens  22 , and supports the first lens  22 . The second lens  23  is placed in the lens barrel  21  fitting against and receiving the spacer  23  into the annular groove  235  of the second lens  23 . The outer peripheral surface of the spacer  24  also tightly engages with the inner peripheral surface  236  of the second lens  23 . Lastly, the IR-cut filter  25  is received in the lens barrel  21 , and an outer peripheral surface of the IR-cut filter  25  tightly engages with the inner peripheral surface  218  of the lens barrel  21 .  
         [0021]     Referring to  FIG. 3 , a lens module  30  according to a second preferred embodiment of the present invention is shown. The lens module  30  includes a lens barrel  31 , a first lens  32 , a second lens  33 , a spacer  34 , and an IR-cut filter  35 . In this embodiment, the lens barrel  31 , and the IR-cut filter  35  are same as the lens barrel  21  and the IR-cut filter  25  in the first embodiment. The first lens  32  has a first annular protrusion  322  in a bottom mounting surface  321  thereof. The second lens  33  has a second annular protrusion  332  in a top mounting surface  331  facing the bottom mounting surface  321  of the first lens  32 . The spacer  34  has two annular grooves  342 ,  344  respectively defined in two surfaces thereof, corresponding to the annular protrusions  322 ,  332 . In assembly, the annular protrusions  322 ,  332  of the first lens  32 , and the second lens  33  are respectively inserted into the annular grooves  342 ,  344  of the spacer  34  to achieve the alignment of the optical axes of the first lens  32  and the second lens  33 .  
         [0022]     Additionally, an AR-Coating (anti-reflective coating) can be provided on at least one of the aspheric surfaces of the first lens  222 . The AR-Coating is typically a thin film that includes alternately stacked layers of silicon dioxide (SiO2) and tantalum pentoxide (Ta2O5). Therefore, the light transmittance ratio of the first lens  22  is increased, and the reflectivity of the first lens  22  is decreased. Furthermore, the IR-cut filter  25  can be omitted, and an IR-Cut coating can be provided on at least one of the aspheric surfaces of the second lens  23 . The spacer  24  can be other orientation means.  
         [0023]     In alternative embodiments, the number of the lens in the lens barrel can be three or more. Also, the number of the spacer  23  can be two or more dependent on the number of the lens.  
         [0024]     Compared with other lens modules, the spacer  24  does not directly contact with the lens barrel  21 . Thus, the round tolerance of the lens barrel  21  has nothing with the spacer  24 . Therefore, the optical axes of the first lens  22  and the second lens  23  are reliably aligned to a greater accuracy since a spacer  24  is adopted to determine not only the alignment of optical axes of the lenses  22 ,  23 , but also orientation of the first lens  22  and the second lens  23 . Accordingly, an image quality of the digital camera with the lens module is increased.  
         [0025]     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.