Abstract:
An LED module comprises an LED having a first optical axis and a lens fixed over the LED for refracting light emitted from the LED. The lens comprises an emission surface having a second optical axis and an incidence surface having a third optical axis. The second optical axis of the emission surface offsets from the first optical axis of the LED in a first direction for increasing a light intensity at a side of the first optical axis in the first direction. The first, second and third optical axes are in a line along the first direction. The third optical axis offsets from the first optical axis of the LED at a side opposite to that of the second optical axis.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to an LED module, and more particularly to an LED module for lighting. 
     2. Description of Related Art 
     LED street lamp, a solid-state lighting, utilizes LEDs as a source of illumination, providing advantages such as resistance to shock and nearly limitless lifetime under specific conditions. Thus, LED lamps present a cost-effective yet high quality replacement for incandescent and fluorescent lamps. 
     A typical LED street lamp includes a housing and a plurality of LEDs mounted in the housing. When the LED street lamp is mounted at a side of a road, light generated by the LEDs must be adjusted to illuminate a middle of the road thereby providing a sufficient illumination for cars which are running on the road. In order to solve the problem, a plurality of inclined supporting frames are mounted in the housing of the LED street lamp for supporting the LEDs so that the light generated by the LEDs illuminates the middle of the road. However, the inclined supporting frames are larger in size and weight, which results in the inconvenience of assembly. 
     What is need therefore is an LED module having a design which can overcome the above limitations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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 several views. 
         FIG. 1  is an isometric, assembled view of an LED module in accordance with an embodiment of the present disclosure. 
         FIG. 2  is an inverted view of the LED module of  FIG. 1 , with an LED thereof being removed away. 
         FIG. 3  is a cross-sectional view of the LED module of  FIG. 1 , taken along line III-III thereof. 
         FIG. 4  is a cross-sectional view of the LED module of  FIG. 1 , taken along line IV-IV thereof. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 to 3  illustrate an LED module in accordance with an embodiment of the present disclosure. The LED module comprises an LED  10  and a lens  20  covering the LED  10 . 
     The LED  10  comprises a rectangular plate-shaped substrate  12  having a cavity (not labeled) defined in a top thereof, a LED chip  14  received in the cavity and an encapsulant  16  filled in the cavity and sealing the LED chip  14 . Light emitted from the LED chip  14  is reflected upwardly by a surface of the substrate  12  defining the cavity, thereby improving the light emitting efficiency of the LED  10 . The LED  10  has a vertical optical axis (marked as an optical axis I in  FIG. 3 ) and a peak light intensity about the optical axis. 
     The lens  20  is rectangular in shape and integrally made of a transparent material with good optical performance, such as PMMA (poly (methyl methacrylate)) or PC (polycarbonate). A two dimensional coordinate (see  FIG. 1 ) is established to have an axis X (from front to rear) corresponding to a length direction of the lens  20  and an axis Y (from left to right) corresponding to a width direction of the lens  20  and perpendicular to the axis X, both of which cooperatively define a plane perpendicular to the optical axis I of the LED  10 . The lens  20  has the length larger than the width thereof. The lens  20  has an optical axis II parallel to and spaced from the optical axis I of the LED  10 . The optical axis II of the lens  20  vertically extends through an origin of the X-Y coordinate. The optical axis I vertically extends through the axis Y, is located at a left side of the axis X and spaces from the optical axis II of the lens  20  a distance. In other words, the optical axis II is in the right of the optical axis I of the LED  10  (see  FIG. 3 ). The lens  20  is symmetrical to the axis Y (see  FIG. 4 ). 
     The lens  20  comprises a base  24  and a light conducting portion  22  protruding upwards from a top of the base  24 . The base  24  has a circumferential surface (not labeled) perpendicular to the plane cooperatively formed by the axes X and Y. The circumferential surface is formed by two rectangular surfaces  240  at two opposite sides of the base  24  and two arc surfaces  242  at two opposite ends of the base  24 . The light conducting portion  22  has a top surface taken as an emission surface formed by a major surface  220  and two ellipsoid minor surfaces  222  slantwise at two opposite sides of the major surface  220 . The optical axis II of the lens  20  vertically extends through a center of the major surface  220 . The major surface  220  continuously extends from one of the arc surfaces  242  towards another arc surface  242  and connects the arc surfaces  242  together. The major surface  220  is progressively narrower upwardly from two opposite ends thereof to the center thereof; that is, a width of the major surface  220  decreases from two ends toward the center thereof. The ellipsoid minor surfaces  222  connect the rectangular surfaces  240  with the major surface  220  and widths of the ellipsoid minor surfaces  222  gradually decreases along an upward direction. 
     The lens  20  defines a rectangular groove  260  in a bottom thereof. The groove  260  is close to a left side of the lens  20 . A positioning groove  262  is defined by the lens  20 , located over a middle portion of the groove  260  and communicating with the groove  260 . The positioning groove  262  has an area identical to that of the substrate  12  of the LED  10 , thereby receiving the substrate  12  in the positioning groove  262 . The groove  260  is used to avoid a bonding pad (not shown) of the LED  10  from interfering with the lens  20  when accommodating the LED  10  in the lens  20 . A receiving groove  264  is elliptical in shape, defined by the lens  20  and located over a middle portion of the positioning groove  262  and communicating with the positioning groove  262 . The receiving groove  264  has two opposite short sides thereof expanding outwardly towards left and right sides of the lens  20  and beyond the positioning groove  262 . The receiving groove  264  has a curved surface  2640  at a ceiling thereof. The curved surface  2640  has an optical axis III parallel to and spaced from the optical axis I of the LED  10 . The optical axis III vertically extends through the axis Y, and is located at a left side of the optical axis I of the LED  10  and spaces therefrom a distance (see  FIG. 3 ). The distance between the optical axes I and II is larger than that between the optical axes I and III so that most of the light emitted from the LED  10  is refracted rightwards out of the lens  20 . A middle portion of the receiving groove  264  is recessed upwards to form a spherical surface  266  having an optical axis (not labeled) coincidental to the optical axis III. The spherical surface  266  and the curved surface  2640  are taken as an incidence surface to refract the light emitted from the LED  10  out of the top surface of the light conducting portion  22  of the lens  20 . The spherical surface  266  refracts the light (see the beam a in  FIG. 3 ) about the optical axis I to emit out of the top surface of the lens  20 , in which the light beam has a quite large light intensity. 
     In the direction of the axis Y, most of the light emitted from the LED  10  is refracted out of the lens  20  and directed rightwards. With an increase of the angle between light beam and the optical axis I, the light intensity in the right side of the lens  20  firstly increases and then decreases from the optical axis I to positions A, C, E in sequence, wherein the peak light intensity occurs at position A, and the zero light intensity occurs at position E. With the increase of the angle between light beam and the optical axis I, the light intensity in the left side of the lens  20  keeps decreasing from the optical axis I to positions B, D, F, wherein the zero light intensity occurs at position F. 
     Also referring to  FIG. 4 , In the direction of the axis X, with the increase of the angle between light beam and the optical axis I, the light intensity firstly increases and then rapidly decreases from the optical axis I to the left and right sides of the lens  20 , wherein the peak light intensity occurs at positions G and H. When the angle increases to 90 degrees, none light beams emit out of the lens  20 . 
     When the LED module is utilized in a LED street lamp on a side of a road, the lens  20  of the LED module is arranged in such a manner that the axis X thereof is parallel to the longitudinal direction of the road and the axis Y thereof is parallel to the transversal direction of the road. The light emitted from the LED  10  is refracted by the lens  20  to form a substantially elongated illumination region on the road. An illumination area along the longitudinal direction of the road is larger than that along the transversal direction of the road. The illumination area formed by the LED module at the right side of the Y axis is larger than that at the left side, in which the right side is near a middle of the road; thus, along the transversal direction of the road, more light can be directed towards the middle of the road to thereby provide a sufficient illumination for the middle of the road. Therefore, it is not necessary to design an inclined supporting frame for directing the light of the LED  10  to the middle of the road, thereby reducing a design and assembly cost. It is convenient to assemble the lens  20  and the LED  10  together since the assembly thereof is quite simple and can be automated, while the automation is not feasible when the LED is mounted to an inclined supporting frame. 
     It is noted that a plurality of such LED modules can be integrated on a transparent frame to intensify luminous intensity of the light from the LED modules. In this embodiment, the optical axes I and II are parallel to and spaced from each other. In other embodiments, the optical axes I and II intersects with each other at an angle. 
     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.