Abstract:
A lens module used in a portable electronic device, including a barrel with two ends, and a first lens and a second lens received in the barrel. A third lens is positioned proximal to one end of the barrel, which has a fastening member and an engaging member, wherein the engaging member is accommodated with the fastening member to compactly couple the third lens with the end of the barrel. The third lens is fastened on the one end of the barrel to reduce the overall volume of the lens module.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present application is related to a lens module, and particularly to a lens module in a portable electronic device. 
         [0003]    2. Description of Related Art 
         [0004]    Digital cameras are widely applied to portable electronic devices, such as cell phones, notebooks and personal digital assistants (PDA). However, a lens module for a digital camera capable of producing high definition pictures may need at least three lenses. In the three lenses, the diameter of one of the lenses proximal to an image sensor is larger than the diameter of other two lenses to meet optical requirements. Therefore, the internal diameter of the barrel must be the diameter of the lens proximal to the image sensor, resulting in a large volume of the barrel, and accordingly, of the portable electronic device. Thus, a small lens module for a portable electronic device is required. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a cross-section of a first embodiment of a lens module for a portable electronic device. 
           [0006]      FIG. 2  is a top view of a third lens of a second embodiment of a lens module for a portable electronic device. 
           [0007]      FIG. 3  is a top view of a third lens of a third embodiment of a lens module for a portable electronic device. 
           [0008]      FIG. 4  is a top view of a third lens of a fourth embodiment of a lens module for a portable electronic device. 
           [0009]      FIG. 5  is a cross-section of a fifth embodiment of a lens module for a portable electronic device. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Please refer to  FIG. 1 , which shows an exemplary lens module  10  disclosed by the present disclosure. The lens module  10  comprises a barrel  20  having a male thread, a first lens  24  and a second lens  26  received in the barrel  20 , a third lens  30  at one end of the barrel  20 , a view stop  40  received in the barrel  20  and positioned between the second lens  26  and the third lens  30 , a holder  50  having a female thread engaged with the male thread of the barrel  20 , and an image sensor device  60  received in the holder  50 . 
         [0011]    The barrel  20  has a first end  202  and a second end  204  opposite to the first end  202 . The first end  202  has an aperture stop  206  to control the luminous flux of light injecting into the barrel  20 . 
         [0012]    An engaging member  208  is positioned on the periphery of the second end  204  of the barrel  20 . The third lens  30  has an optical member  302  and a non-optical member  304  surrounding the optical member  302 . A fastening member  306  positioned on the periphery of the non-optical member  304  engages the engaging member  208  of the barrel  20  to compactly couple the third lens  30  with the barrel  20 . The diameter of the third lens  30  is less than or equals the outer diameter of the barrel  20 , and exceeds the internal diameter of the barrel  20  to protect the third lens from damage when the holder  50  receives the barrel  20 . 
         [0013]    The engaging member  208  comprises annular rectangle-shaped protrusions, and the fastening member  306  comprises annular rectangle-shaped recesses. A contact surface between the engaging member  208  and the fastening member  306  is vertical. The third lens  30  can be formed as a dual aspheric surface plastic lens. An infrared filter film  31  is provided on one surface of the third lens opposite to the second lens  24  to prevent infrared light from injecting into the image sensor device  60  when a user takes a picture. 
         [0014]    When assembling the lens module  10 , the engaging member  208  of the barrel  20  and the fastening member  306  of the third lens  30  contact each other closely to fasten the barrel  20  and the third lens. For better stability, gel can be applied between the engaging member  208  and the fastening member  306 . The contact surface of the engaging member  208  and the fastening member  306  can also be provided as an inclined plane. Because the third lens  30  is fastened on an end surface of the second end  204  of the barrel  20  instead of being provided inside the barrel  20 , the volume of the barrel  20  is reduced. The third lens can be a spherical surface lens or an aspherical lens, in one example. 
         [0015]    The first lens  24  and the second lens  26  can be spherical, aspherical, or bi-aspherical surface plastic lenses, depending on the embodiment. The first lens  24  and the second lens  26  can be separate from each other, or contact each other and form an integral body. The number of lenses received here inside the barrel  20  in the embodiment are only illustrated as an example, and not a limitation to the present disclosure. 
         [0016]    The view stop  40  is annular and provided between the third lens  30  and the second lens  26 . The view stop  40  can limit light passing through the third lens  30  and into the image sensor device  60 , and prevents ghost images and light spots resulting from light scattering and light reflection. 
         [0017]      FIG. 2  is a top view of a third lens  30   a  of a second embodiment of a lens module for a portable electronic device. The third lens  30   a  comprises an optical member  302   a  and a non-optical member  304   a.  The third lens  30   a  differs from the third lens  30  in that the non-optical member  304   a  includes an annular recess  306   a  surrounding the optical member  302   a.  The second end of the barrel has an annular protrusion matching the annular recess  306   a  to compactly couple the barrel with the third lens  30   a.  Accordingly, the annular recess  306   a  can be a fastening member of the third lens  30   a.  It is understood that the non-optical member  304   a  can be an annular protrusion surrounding the optical member  302   a,  and the second end of the barrel has an annular recess matching the optical member  302   a  correspondingly. 
         [0018]      FIG. 3  is a top view of a third lens  30   b  of a third embodiment of a lens module for a portable electronic device. The third lens  30   b  comprises an optical member  302   b  and a non-optical member  304   b.  The third lens  30   b  differs from the third lens  30  in that the non-optical member  304   b  includes two curved recesses  306   b  surrounding the optical member  302   b,  spaced apart. The second end of the barrel has two curved protrusions matching the curve recess  306   b  to compactly couple the barrel with the third lens  30   b.  It is understood that the curve shape can be modified to a rectangle, a triangle, a pentagon, or other geometric shapes. In the illustrated embodiment, the curve recess  306   b  can be a fastening member of the third lens  30   b.  The curve recess  306   b  also can be a through hole. It is understood that the number of recesses in this embodiment are presented as an example only, and not as a limitation to the disclosure, and the second end of the barrel has protrusions in a quantity corresponding to the number of curved recesses, to match the optical member  302   b.    
         [0019]      FIG. 4  is a top view of a third lens of a fourth embodiment of a lens module  30   c  for a portable electronic device. The third lens  30   c  comprises an optical member  302   c  and a non-optical member  304   c.  The third lens  30   c  differs from the third lens  30  in that the non-optical member  304   c  includes three round recesses  306   c  surrounding the optical member  302   c,  spaced apart. The second end of the barrel has three round protrusions matching the round recesses  306   c  to compactly couple the barrel with the third lens  30   c.    
         [0020]      FIG. 5  is a cross-section of a fifth embodiment of a lens module  10 ′ for a portable electronic device. The lens module  10 ′ comprises a barrel  20 ′, a second end  204 ′ provided on the barrel  20 ′, and a third lens  30   d  provided on the second end  20 ′. The lens module  10 ′ differs from the lens module  10  in that the barrel  20   d  has no engaging member, and the third lens  30   d  has no fastening part. The third lens  30   d  is fixed to the second end  204 ′ of the barrel  20 ′ by an adhesive. 
         [0021]    While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.