Abstract:
A side illumination lens for a LED is disclosed. One of the embodiments includes a bottom cavity, an incident surface, four total internal reflective surfaces, and a side refractive surface. Light beam emitted by the LED enters the lens through the incident surface. A first portion of the light beam is reflected by the total internal reflection surfaces to the refractive surface and emits out of the lens. The second portion of light beam enters the lens and exits from the refractive surface. A second one of the embodiments is to roughen the side refractive surface for diffusing the exit light beams so that a broader area can be illuminated softly.

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a lens, especially for modifying light beam of a LED configured on a bottom recess of the lens. 
     2. Description of Related Art 
       FIG. 1  is a prior art. 
     U.S. Pat. No. 7,254,309 discloses a lens for a LED, the light emitted from the LED chip  40  enters the lens  20  through the incident surface  22 . A portion of the light is reflected by the reflective surface  23  to the second refractive surface  32  in an internal total reflection manner, and then the light is refracted by the second refractive surface  32  and emits out of the second refractive surface  32  of the lens  20  along a lateral direction of the lens  20 , such as a first optical path P 1  of the lens  20 . The other portion of the light enters the lens  20  through the incident surface  22  and then directly emits out of the lens  20  to toward the lateral directions of the lens  20  respectively to be refracted by the first refractive surface  31  along a second optical path P 2  and the third refractive surface  33  along a third optical path P 3 . The first optical path P 1 , the second optical path P 2  and the third optical path P 3  are in a direction substantially normal to the central optic axis C of the lens  20 . Hence the light emitted from the LED chip  40  is directed towards a lateral direction of the lens  20 . 
     After the light emitted from the LED chip  40  enters the lens  20 , the intensity distribution of energy of the emitted light can be divided in a zone  1 , a zone  2  and a zone  3 . The zone  1  is located between the central optic axis C and the connection line of the first cross point c 1  to the second cross point c 2 . The zone  2  is located between the connection line of the first cross point c 1  to the fourth cross point c 4  and the zone  1  (the third cross point c 3  is located on the connection line of the first cross point c 1  to the fourth cross point c 4 ). The zone  3  is located between the zone  2  and the bottom surface  21 . The energy distribution is strongest in the zone  1 , then sub-strong in the zone  2 , and weakest in the zone  3 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a prior art. 
         FIGS. 2-3  are a first lens according to the present invention. 
         FIGS. 4-5  are a second lens according to the present invention. 
         FIGS. 6-7  are a third lens according to the present invention. 
         FIGS. 8-9  are a fourth lens according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Total internal Reflection (TIR) is an optical phenomenon that occurs when a light beam strikes a medium boundary at an angle larger than the Critical Angle with respect to the normal to the surface. If the Refractive Index is lower on the other side of the boundary no light can pass through, so effectively all of the light is reflected. The critical angle is the Angle of Incidence above which the total internal reflection occurs. 
     When a light beam crosses a boundary between materials with different refractive indices, the light beam will be partially refracted at the boundary surface according to the Snell&#39;s Law, and partially reflected. The Snell&#39;s law gives the relationship between angles of incidence and refraction for a wave impinging on an interface between two media with different indices n 1 , n 2  of refraction:
 
 n   1  sin Θ 1   =n   2  sin Θ 2  
 
where Θ 1  and Θ 2  are the angles from the normal of the incident and refracted waves, respectively.
 
     However, if the angle of incidence is greater (i.e. the ray is closer to being parallel to the boundary) than the critical angle—the angle of incidence at which light is refracted such that it travels along the boundary, where the Θ 2  equals 90 degree, then the light will stop crossing the boundary altogether and instead totally reflect back internally. 
       FIGS. 2-3  are a first lens according to the present invention. 
       FIG. 2  shows a section view of the first lens  501 . Lens  501  has four total internal reflection surfaces. A first total internal reflection surface  511  is configured in a first angle A 1  with respect to a longitudinal axis C of the lens  501 . A second total internal reflection surface  512  is neighbored to the first total internal reflection surface  511  and configured in a second angle A 2  larger than the first angle A 1  with respect to the longitudinal axis C of the lens  501 . A third total internal reflection surface  513  is neighbored to the second total internal reflection surface  512  and configured in a third angle A 3  larger than the second angle A 2  with respect to the longitudinal axis C of the lens  501 . A fourth total internal reflection surface  514  is neighbored to the third total internal reflection surface  513  and configured in a fourth angle A 4  larger than the third angle A 3  with respect to the longitudinal axis C of the lens  501 . 
     Further,  FIG. 2  shows that an exiting surface  515  is a flat surface, neighbored to the fourth total internal reflection surface  514 . 
     A bottom recess  520  is configured on the bottom of the lens  501 . A LED  40  is configured in the recess  520 . A top incident surface  521  is configured on a top of the recess  520 , and a side incident surface  522  encloses the recess  520 . A first portion of the light beams L 51 , L 52 , L 53  of the LED  40  enters the top incident surface  521  and then reflected by one of the total internal reflection surface  511 ,  512 ,  513 ,  514  and exits from the exiting surface  515 . A second portion of the light beams L 54  of the LED  40  enters the side incident surface  522  to be refracted and then exits from the exiting surface  515 .  FIG. 2  shows that the top incident surface  521  is made a convex surface against the recess  520  in this embodiment. 
       FIG. 3  shows a section view of an illumination intensity profile of the lens of  FIG. 2 . The illumination intensity profile  501 D is mainly projected to the right top and left top of the lens  501  in the section view, however the illumination intensity profile  501 D is of a bowl-shaped profile in a three dimensional configuration. 
       FIGS. 4-5  are a second lens according to the present invention. 
       FIG. 4  shows a section view of the second lens according to the present invention. The key feature of this embodiment is that the exiting surface  515 R is roughened to a certain status so that each and all exiting light beam is firstly diffused and then emitted softly and broadly.  FIG. 4  shows diffused beam intensity profile LS 51 , LS 52  existed from a spot S 51 , S 52 . The LS 51  shows a light intensity distribution of the light beam exits from the spot S 51 . The LS 52  shows a light intensity distribution of the light beam exits from the spot S 52 . The light intensity distribution LS 51 , LS 52  is softer as compared with the light intensity of L 51 , L 52  of  FIG. 2  respectively. The light intensity L 51 , L 52  in  FIG. 2  is a single light beam or a very narrow bunch of light beam. 
       FIG. 5  shows a section view of an illumination intensity profile of the lens of  FIG. 4 . The light beam is projected softly, evenly, and broadly to the right side and left side of the lens  502  in the section view, however the illumination intensity profile  502 D is of a donut-shaped profile in a three dimensional configuration. 
       FIGS. 6-7  are a third lens according to the present invention. 
       FIG. 6  shows a section view of the third lens. As compared to the one shown in  FIG. 3  the key feature of  FIG. 6  is that the exiting surface is a bent surface  515 A,  515 B. The lens  503  has four total internal reflection surfaces  511 ˜ 514  similar to the one shown in  FIG. 2 . 
       FIG. 6  shows a section view of the lens  503 . Lens  503  has a first total internal reflection surface  511 , configured in a first angle A 1  with respect to a longitudinal axis C of the lens  503 . A second total internal reflection surface  512  is neighbored to the first total internal reflection surface  511  and configured in a second angle A 2  larger than the first angle A 1  with respect to the longitudinal axis C of the lens  503 . A third total internal reflection surface  513  is neighbored to the second total internal reflection surface  512  and configured in a third angle A 3  larger than the second angle A 2  with respect to the longitudinal axis C of the lens  503 . A fourth total internal reflection surface  514  is neighbored to the third total internal reflection surface  513  and configured in a fourth angle A 4  larger than the third angle A 3  with respect to the longitudinal axis C of the lens  503 . 
     A first exiting surface  515 A is neighbored to the fourth total internal reflection surface  514  and configured in a fifth angle A 5  larger than the fourth angle A 4  with respect to the longitudinal axis C of the lens  503 . A second exiting surface  515 B is neighbored to the first exiting surface  515 A and configured in a sixth angle A 6  larger than the fifth angle A 5  with respect to the longitudinal axis C of the lens  503 . 
     A bottom recess  520  is configured on the bottom of the lens  503 , a LED  40  is configured in the recess  520 . A top incident surface  521  is configured on a top of the recess  520 , and a side incident surface  522  encloses the recess  520 . A first portion of the light beams L 51 , L 52  of the LED  40  enters the top incident surface  521  and then reflected by one of the total internal reflection surface  511 ,  512 ,  513 ,  514  and exits from the exiting surface  515 A. A second portion of the light beams L 54 , L 55  of the LED  40  enters the side incident surface  522  to be refracted and then exits from the exiting surface  515 B. The top incident surface  521  is made a convex surface in this embodiment. 
       FIG. 7  shows a section view of an illumination intensity profile of the lens of  FIG. 6 . The illumination intensity profile  503 D is mainly projected to the right top and left top of the lens  503  in the section view, however the illumination intensity profile  503 D is with a relative stronger light intensity on top portion and a relative lower light intensity on bottom portion. 
       FIGS. 8-9  are a fourth lens according to the present invention. 
       FIG. 8  shows a section view of the fourth lens according to the present invention. The key feature of this embodiment is that the exiting surface  515 AR,  515 BR is roughened so that each and all exiting light beam is firstly diffused and then emitted softly and broadly.  FIG. 8  shows diffused beam is exited from spots S 511 , S 522  as an example. The LS 511  shows a light intensity distribution of the light beam exits from the spot S 511 . The LS 512  shows a light intensity distribution of the light beam exits from the spot S 512 . The light intensity distribution LS 511 , LS 512  is softer as compared with the light intensity of L 51 , L 52  of  FIG. 6  respectively. The light intensity L 51 , L 52  in  FIG. 6  is a single light beam or a very narrow bunch of light beam. 
       FIG. 9  shows a section view of an illumination intensity profile of the lens of  FIG. 8 . The light beam is projected softly, evenly, and broadly to the right side and left side of the lens  504  in the section view, however the illumination intensity profile  504 D is of a donut-shaped profile in a three dimensional configuration. 
     While several embodiments have been described by way of example, it will be apparent to those skilled in the art that various modifications may be configured without departing from the spirit of the present invention. Such modifications are all within the scope of the present invention, as defined by the appended claims.