Abstract:
A lens unit includes a lens and a reflector received in the lens. The lens includes a light incident face and a light emerging face opposite to the light incident face. The reflector is enclosed by the light incident face. The reflector has a diameter gradually increasing and then decreasing along an optical axis of the lens. The reflector reflects light emitted from the LED divergently to enter the lens. An LED module incorporating the lens unit is also disclosed.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure generally relates to lens units and LED (light emitting diode) modules, and more particularly to a lens unit having a reflector, and an LED module incorporating the lens unit. 
         [0003]    2. Description of Related Art 
         [0004]    Nowadays LEDs (light emitting diodes) are applied widely in various applications for illumination. The LED is a highly pointed light source. Thus, light directly emitted from the LED may form a small light spot. However, the small light spot can only illuminate a small area. In order to achieve a large illumination area, a large number of LEDs are required to be incorporated together, thereby resulting in a high cost. 
         [0005]    Therefore, a lens is used with the LED to modulate the light distribution of the LED. The lens can diverge the light emitted from the LED to thereby illuminate a large area. However, the light diverging capability of the lens is still insufficient. Particularly, the light transmitting along the optical axis of the lens cannot be effectively diverged by the lens, thereby resulting in an unfavorable light distribution. 
         [0006]    What is needed, therefore, is a lens unit and an LED module using the lens unit which can address the limitations described. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present embodiments 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 embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the various views. 
           [0008]      FIG. 1  is an isometric view of an LED module in accordance with an embodiment of the present disclosure. 
           [0009]      FIG. 2  is an inverted view of the LED module of  FIG. 1 , wherein an LED of the LED module is removed for clarity. 
           [0010]      FIG. 3  is a cross section of the LED module of  FIG. 1 . 
           [0011]      FIG. 4  shows a light distribution curve of the LED module of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIGS. 1-3 , an LED (light emitting diode) module  10  in accordance with an embodiment of the present disclosure is shown. The LED module  10  includes an LED  40 , a lens  20  covering the LED  40  and a reflector  30  movably connected to the lens  20 . 
         [0013]    The lens  20  may be made of transparent material such as epoxy, silicone, glass or the like. The lens  20  includes a bottom face  22 , a light incident face  24  formed in the bottom face  22 , a light emerging face  26  opposite to the bottom face  22  and a lateral face  28  connecting the bottom face  22  and the light emerging face  26 . The lens has an optical axis O extending through a center of the light incident face  24  and a center of the light emerging face  26 . 
         [0014]    The bottom face  22  is a flat and circular face. The light incident face  24  is defined in a central area of the bottom face  22  and encloses a cavity  200  to receive the LED  40 . The cavity  200  has a diameter gradually decreasing from the bottom face  22  towards the light emerging face  26 . The light incident face  24  is an elliptical face with a long axis perpendicular to the bottom face  22 , and a short axis parallel to and located within the bottom face  22 . 
         [0015]    The LED  40  is received in the cavity  200 . The LED  40  may be made of semiconductor material such as GaN, InGaN, AlInGaN or the like. The LED  40  can emit visible light when being powered. In this embodiment, the LED  40  is a white LED  40 . The light emitted from the LED  40  passes through the cavity  200  and enters the lens  20  via the light incident face  24 . 
         [0016]    The light emerging face  26  is located above the bottom face  22 . The light emerging face  26  includes a concave face  262  and a convex face  264  surrounding the concave face  262 . The concave face  262  is located at a central area of the light emerging face  26  and opposite to the light incident face  24 . The concave face  262  has a curvature less than that of the light incident face  24 . The convex face  264  connects the concave face  262  with the lateral face  28 . In this embodiment, a junction between the concave face  262  and the convex face  264  is smooth and curved, and a junction between the lateral face  28  and the convex face  264  is abrupt. The convex face  264  has a bottom lower than a top of the light incident face  24 . The light emerging face  26  can diverge the light from the light incident face  24  out of the lens  20 , thereby illuminating a large area. 
         [0017]    The lateral face  28  directly connects the convex face  264  with the bottom face  22 . The lateral face  28  is an annular face perpendicular to the bottom face  22 . The lateral face  28  may be further coated with a reflective layer for reflecting the light from the light incident face  24  towards the light emerging face  26 . 
         [0018]    Also referring to  FIG. 4 , a slot  202  is defined in the lens  20 . The slot  202  extends from the concave face  262  to the light incident face  24 . The slot  202  communicates with the cavity  200 . The slot  202  is aligned with the optical axis O of the lens  20  and perpendicular to the bottom face  22 . A wire  36  extends through the slot  202  to hang the reflector  30  within the cavity  200 . In this embodiment, the wire  36  is rigid so that the reflector  30  can be stably hung in the lens  20  without being swayed. Preferably, the wire  36  may be made of metal such as copper or aluminum. The reflector  30  is fixed on a bottom of the wire  36  to be hung between the light incident face  24  and the LED  40 . The reflector  30  has an ellipsoid-like shape. The reflector  30  includes a bottom end  32  and a top end  34  opposite to the bottom end  32 . The top end  34  protrudes towards the light emerging face  26 , and the bottom end  32  protrudes towards the LED  40 . The bottom end  32  has a curvature larger than that of the top end  34 . In other words, the bottom end  32  is sharper than the top end  34 . The reflector  30  has a diameter gradually increasing and then decreasing from the bottom end  32  towards the top end  34 . The top end  34  of the reflector  30  is attached to the bottom of the wire  36 . The reflector  30  can reflect the light from the LED  40  having a small light emerging angle (i.e., the light having a small angle deviated from the optical axis O of the lens  20 ) towards the lateral face  28 , thereby lowering an intensity of a center of a light beam produced from the LED module  10 . As represented by a light distribution curve  50  shown in  FIG. 4 , the intensity of the center of the light beam of the LED module  10  is reduced so that the light distribution of the LED module  10  is more uniform. A block  38  is formed on a top of the wire  36 . The block  38  has a width larger than a diameter of the slot  202  so that the block  38  will not be dropped into the slot  202 . The block  38  abuts against the concave face  262  to hang the reflector  30  in the cavity  200 . 
         [0019]    A height of the reflector  30  can be adjusted by coiling or releasing the wire  36  on or from the block  38 . Therefore, less or more light emitted from the LED  40  will be reflected by the reflector  30 , thereby changing the light distribution of the LED module  10 . Furthermore, the reflector  30  can be replaced by another reflector by separating the wire  36  from the block  38  to remove the reflector  30 , and then attaching another wire with the another reflector on the block  38 . Thus, the light distribution of the LED module  10  can be varied more favorably. 
         [0020]    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 disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.