Abstract:
A lens barrel includes an inner metal barrel, and an outer plastic barrel. The inner metal barrel has a number of concentric annular steps formed in an inner surface thereof. The outer plastic barrel encloses the inner metal barrel therein. The inner metal barrel is integrated with the outer plastic barrel using an insert molding process.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The invention relates to lens barrels of lens modules and, particularly to a lens barrel defining steps in the inner surface thereof and a method for manufacturing the same. 
         [0003]    2. Description of the Related Art 
         [0004]    In general, a lens module includes a lens barrel and a number of lenses. The lenses are received within the lens barrel. The lens barrel is typically made of plastic materials via injection molding to meet requirements of industry production, e.g., low cost and/or high output. The lens barrel commonly defines a number of steps in the inner surface thereof. These steps are for receiving the lenses and are strictly coaxial with the lens barrel to ensure the lenses received thereby are rigorously coaxial with the lens barrel. One of the challenges of manufacturing such a lens barrel is that due to the thermal properties of plastic materials, the lens barrel contracts and may deform when cooled during the injection molding process. As a result, the coaxality between the lens barrel and the lenses suffers. 
         [0005]    Therefore, it is desirable to provide a lens barrel defining steps in the inner surface thereof and a method for manufacturing the same, which can overcome the above mentioned problem. 
       SUMMARY 
       [0006]    In an exemplary embodiment, a barrel includes an inner metal barrel, and an outer plastic barrel. The inner metal barrel has a number of concentric annular steps formed in an inner surface thereof. The outer plastic barrel encloses the inner metal barrel therein. The inner metal barrel is integrated with the outer plastic barrel using an insert molding process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is schematic, cross-sectional view of a lens barrel, according to an exemplary embodiment. 
           [0008]      FIG. 2  is a flow chart of a method for manufacturing a lens barrel, according to another embodiment. 
           [0009]      FIG. 3  is a schematic, cross-sectional view showing how the method of  FIG. 2  is carries out. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0010]    Embodiments of the present lens barrel and method for manufacturing the same will now be described in detail with references to the accompanying drawings. 
         [0011]    Referring to  FIG. 1 , a lens barrel  10 , according to an exemplary embodiment, includes an inner metal barrel  12  and an outer plastic barrel  14 . The inner metal barrel  12  is tubular in shape and defines three substantially concentric steps  122  in the inner surface  124  thereof, and is wrapped by the outer plastic barrel  14 . The steps  122  are substantially coaxial with the inner metal barrel  12 . Thereby, the inner metal barrel  12  and the steps  122  define an optical axis  102  of the lens barrel  10 . 
         [0012]    The inner metal barrel  12  is roughly tubular in shape, and can be made from any of the following materials: copper, aluminum, iron, nickel, titanium, steel, carbon steel, stainless steel, and any alloy of copper, aluminum, iron, nickel, titanium. In this embodiment, the inner metal barrel  12  is made from copper alloy. 
         [0013]    The steps  122  can be formed by precision machining. In this embodiment, the steps  122  are formed by coaxial machining with computer numerical control (CNC) machine. Coaxiality between the inner metal barrel  12  and the steps  122  can be controlled by the CNC machine. As a result, the coaxality between the lens barrel  10  and the steps  122  is set to be smaller than 5 microns. However, coaxiality between the lens barrel and the steps of plastic lens barrel made by injection molding is approximately 5 to 15 microns. In addition, coaxalities of lens barrels of plastic lens barrel made by plastic injection molding mostly depend on manufacture conditions, such as temperature and/or pressure, and therefore may be greatly different from each other. In all, coaxality between the lens barrel  10  and the steps  122  is more readily controlled and more stable as compared with conventional plastic lens barrels that are made by plastic injection molding. Therefore, coaxality between the lens barrel  10  and lenses (not shown) received thereby is assured. 
         [0014]    It should be understood that, the number of the steps  122  is not limited by this embodiment. 
         [0015]    The outer plastic barrel  14  can be formed with the inner metal barrel  12  using a variety of methods such as insert molding. 
         [0016]    Optionally, the outer surface  126  of the inner metal barrel  12  can be applied with various surface treatments to increase roughness thereof. Thereby, the outer plastic barrel  14  can grasp the inner metal barrel  12  more tightly, avoiding separation therebetween. The outer surface  142  of the outer plastic barrel  14  may be threaded. Thereby, the lens barrel  10  can be coupled to lens holder (not shown) via threads. 
         [0017]    Referring to  FIG. 2 , a method for manufacturing the lens barrel  10 , according to another embodiment, includes the following operations  22 ˜ 28 . 
         [0018]    Operation  22 : providing a metal tube  32 . 
         [0019]    Operation  24 : treating the outer surface  126  of the metal tube  32  to increase roughness thereof. 
         [0020]    Operation  26 : wrapping the metal tube  32  with plastic, thereby forming the outer plastic barrel  14  which wraps the metal tube  32 . This can be achieved by insert molding. The outer plastic barrel  14  may include a threaded section  144  on the outer surface  142  thereof. 
         [0021]    Operation  28 : defining three substantially concentric steps  122  in the inner surface  124  to form the inner metal barrel  12 . The steps  122  are substantially coaxial with the inner metal barrel  12 . This can be achieved by coaxial machining with CNC machine. Thereby, the lens barrel  10  is obtained. 
         [0022]    It will be understood that the above particular embodiments and methods are shown and described by way of illustration only. The principles and the features of the present invention may be employed in various and numerous embodiments thereof without departing from the scope of the invention as claimed. The above-described embodiments illustrate the scope of the invention but do not restrict the scope of the invention.