Patent Publication Number: US-2009225552-A1

Title: Light source-modulating device having composite curved surfaces

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a light source-modulating device having composite curved surfaces and, more particularly, to a light source-modulating device used in lighting applications. 
     2. Description of Related Art 
     With continuous progress of light-emitting diode (LED) manufacturing techniques, radiation power and brightness of LEDs are gradually increased. Therefore, LEDs are having more and more applications, including, for example, general lighting or ambiance lighting. When LEDs are used for lighting purposes, light rays emitted therefrom have to be uniform and collimated, so that energy thereof is concentrated for practical use. 
       FIG. 1  is a cross-sectional view of a conventional LED lens structure  10  proposed in “Ultra Small Projector with High Efficiency Illumination System”, which was presented in the International Conference on Consumer Electronics (ICCE) held in January, 2006. This LED lens structure  10  comprises a spherical surface  11 , a first non-spherical surface  12 , a second non-spherical surface  13 , a third non-spherical surface  14  and an LED light source  15 . Light rays  16 ,  16 ′ and  16 ″ emitted from the LED light source  15  enter the LED lens structure  10  through the spherical surface  1   1 . The light ray  16  which forms a relatively large angle with a normal direction of the LED light source  15  is reflected by the third non-spherical surface  14  and then refracted outwards by the second non-spherical surface  13  so as to be nearly collimated. On the other hand, the light ray  16 ′ which forms a relatively small angle with the normal direction of the LED light source  15  is refracted outwards by the first non-spherical surface  12 . 
       FIGS. 2 and 3  illustrate a light pattern and an illuminance distribution of the conventional LED lens structure  10 , respectively. As shown in  FIGS. 2 and 3 , while the conventional LED lens structure  10  is capable of collimating the light rays  16 ,  16 ′ and  16 ″ emitted from the LED light source  15 , a large included angle is formed between the first non-spherical surface  12  and the second non-spherical surface  13 , i.e., the second non-spherical surface  13  is an inclined surface having a large angle of inclination. As a result, some of the light rays incident on the first non-spherical surface  12 , such as the light ray  16 ″, cannot be refracted out of the lens structure  10  because the condition of having an incident angle smaller than a critical angle is not satisfied. Hence, illuminance is not uniform between the first non-spherical surface  12  and the second non-spherical surface  13 , while the LED light source  15  produces a light pattern comprising a number of concentric circles, thereby lowering a uniformity of outgoing light. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a light source-modulating device having composite curved surfaces wherein a shape of the light source-modulating device is particularly designed. Therein, a light-distributing composite refractive surface is designed to allow light rays emitted from a light source and forming with a normal direction thereof angles smaller or larger than a light-distributing reference angle to enter the device through a first refractive surface and a second refractive surface, respectively. Further, a reflective surface is designed to reflect incident light rays from the second refractive surface so that the reflected light rays are refracted outwards by a third refractive surface. The third refractive surface, in turn, is designed to refract outwards all incident light rays from the second refractive surface while modulating outgoing angles of such light rays. Moreover, a fourth refractive surface is designed to refract outwards all incident light rays from the first refractive surface while modulating outgoing angles of such light rays. Thus, outgoing light rays from the LED light source will be collimated and uniform and have reduced divergence angles. 
     To achieve this end, the present invention provides a light source-modulating device having composite curved surfaces, comprising a light-distributing composite refractive surface, a base surface, a reflective surface and a light-modulating composite refractive surface. The light-distributing composite refractive surface has a first refractive surface which is a curved surface defined by a function and has a central surficial axis coexisting with a central axis of the light source-modulating device, wherein the first refractive surface is located to refract light rays emitted from at least one LED light source and forming with a normal direction of the LED light source an angle smaller than a light-distributing reference angle; and a second refractive surface which is a curved surface symmetric with respect to the central axis and has a first periphery connected with a periphery of the first refractive surface to form an accommodating space, wherein the second refractive surface is located to refract light rays emitted from the LED light source and forming with the normal direction of the LED light source an angle larger than the light-distributing reference angle. The base surface has a first periphery connected with a second periphery of the second refractive surface to form a first joint line. The reflective surface is a curved surface symmetric with respect to the central axis and has a first periphery connected with a second periphery of the base surface to form a second joint line, wherein the reflective surface is located to reflect incident light rays from the light-distributing composite refractive surface. The light-modulating composite refractive surface has a third refractive surface which is a curved surface defined by a function and symmetric with respect to the central axis and has a first periphery connected with a second periphery of the reflective surface to form a third joint line, wherein the third refractive surface is located to modulate incident light rays from the reflective surface; and a fourth refractive surface which is a curved surface symmetric with respect to the central axis and has a periphery connected with a second periphery of the third refractive surface to form a fourth joint line, wherein the fourth refractive surface is located to modulate incident light rays from the first refractive surface. Therein, the light-distributing reference angle is within ±10° of a light-distributing critical angle, which is defined as an included angle between a critical light ray before entering the light source-modulating device and the normal direction of the LED light source, wherein the critical light ray is defined as a light ray emitted from the LED light source that enters the light source-modulating device through a joint line connecting the periphery of the first refractive surface with the first periphery of the second refractive surface and then leaves the light source-modulating device through the fourth joint line. 
     Implementation of the present invention at least produces the following advantageous effects: 
     1. Outgoing light rays emitted from the LED light source can be collimated and uniform; and 
     2. A divergence angle of the LED light source can be reduced by changing a shape of the light-modulating composite refractive surface. 
     Features and advantages of the present invention will be described below in detail so that the technical content of the present invention can be understood and carried out by those skilled in the art, while objectives and advantages of the present invention can be readily comprehended by reference to the content, claims and drawings disclosed herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention as well as a preferred mode of use, further objectives and advantages thereof will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a cross-sectional view of a conventional LED lens structure; 
         FIG. 2  illustrates a light pattern of the conventional LED lens structure; 
         FIG. 3  is a plot showing an illuminance distribution of the conventional LED lens structure; 
         FIG. 4  is a perspective view of a light source-modulating device having composite curved surfaces according to the present invention; 
         FIG. 5  is a first cross-sectional view of the light source-modulating device having composite curved surfaces according to the present invention; 
         FIG. 6  is a second cross-sectional view of the light source-modulating device having composite curved surfaces according to the present invention; 
         FIG. 7  is a third cross-sectional view of the light source-modulating device having composite curved surfaces according to the present invention; 
         FIG. 8  is a fourth cross-sectional view of the light source-modulating device having composite curved surfaces according to the present invention; 
         FIG. 9  is a fifth cross-sectional view of the light source-modulating device having composite curved surfaces according to the present invention; 
         FIG. 10  is a sixth cross-sectional view of the light source-modulating device having composite curved surfaces according to the present invention; 
         FIG. 11  is a light pattern of the light source-modulating device having composite curved surfaces shown in  FIG. 7 ; and 
         FIG. 12  is a plot showing an illuminance distribution of the light source-modulating device having composite curved surfaces shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 4 , a light source-modulating device  20  having composite curved surfaces comprises a light-distributing composite refractive surface  30 , a base surface  40 , a reflective surface  50  and a light-modulating composite refractive surface  60 . The light source-modulating device  20  has a central axis  21  and is of a circularly or elliptically symmetric structure with respect to the central axis  21 . Further, the light source-modulating device  20  can be made of a plastic material by injection molding. 
     The light-distribution composite refractive surface  30  has a first refractive surface  31  and a second refractive surface  32 . The light-distributing composite refractive surface  30  serves to distribute light rays emitted from an LED light source  15 , so that the light rays enter the light source-modulating device  20  through the first refractive surface  31  and the second refractive surface  32 , respectively. 
     The first refractive surface  31  is a curved surface defined by a function and can be designed as needed as different curved surfaces defined by corresponding functions. For instance, the first refractive surface  31  can be a surface defined by a concave function (as shown in  FIGS. 5 and 8 ), a convex function (as shown in  FIGS. 6 and 9 ) or a plane function (as shown in  FIGS. 7 and 10 ). Furthermore, the first refractive surface  31  has a central surficial axis coexisting with the central axis  21  of the light source-modulating device  20 . The first refractive surface  31  is located to refract light rays emitted from the at least one LED light source  15  and forming with a normal direction of the LED light source  15  an angle smaller than a light-distributing reference angle θ, which is defined in the following paragraphs. 
     As shown in  FIG. 5 , the light source-modulating device  20  is particularly designed so that a light ray emitted from the LED light source  15  and entering the light source-modulating device  20  through a joint line connecting a periphery of the first refractive surface  31  and a first periphery of the second refractive surface  32  leaves the light source-modulating device  20  through a fourth joint line  25  (defined further below). This particular light ray is defined as a critical light ray  70 , and a light-distributing critical angle is an included angle between the critical light ray  70  before entering the light source-modulating device  20  and the normal direction of the LED light source  15 . The light-distributing critical angle may range from 15° to 75°. 
     The light-distributing reference angle θ is within ±10° of the light-distributing critical angle. For example, if the light-distributing critical angle is 15°, the light-distributing reference angle may range from 5° to 25°. Preferably, the light-distributing reference angle θ is equal to the light-distributing critical angle. If a light ray emitted from the LED light source  15  forms with the normal direction thereof an angle smaller than the light-distributing reference angle θ, then the light ray will be distributed to the first refractive surface  31 , which refracts the light ray into the light source-modulating device  20 . 
     Referring to  FIG. 4  and  FIGS. 5 to 10 , the second refractive surface  32  is an arbitrary curved surface symmetric with respect to the central axis  21 . The first periphery of the second refractive surface  32  is connected with the periphery of the first refractive surface  31  to form an accommodating space for accommodating the LED light source  15 . The LED light source  15  can be an LED chip or a packaged LED and has a light-emitting wavelength ranging from 350 nm to 850 nm. 
     The second refractive surface  32  is located to refract light rays emitted from the LED light source  15  and forming with the normal direction thereof an angle larger than the light-distributing reference angle θ. In other words, all light rays emitted from the LED light source  15  forming with the normal direction thereof angles larger than the light-distributing reference angle θ will be distributed to the second refractive surface  32 , which refracts the light rays into the light source-modulating device  20 . 
     The base surface  40  has a first periphery connected with a second periphery of the second refractive surface  32  to form a first joint line  22 , and a second periphery connected with a first periphery of the reflective surface  50  to form a second joint line  23 . The base surface  40  is provided with a positioning structure for retaining the LED light source  15  in place inside the accommodating space formed by the first refractive surface  31  and the second refractive surface  32 , so that a geometric center of the LED light source  15  is located on an extension line of the central axis  21  of the light source-modulating device  20 , allowing light rays emitted from the LED light source  15  to enter the light source-modulating device  20  uniformly. 
     The reflective surface  50  is an arbitrary curved surface symmetric with respect to the central axis  21  and has the first periphery connected with the second periphery of the base surface  40  to form the second joint line  23 . Moreover, the reflective surface  50  is located to reflect incident light rays from the light-distributing composite refractive surface  30 , wherein a shape of the reflective surface  50  can be so designed that all light rays incident thereon are totally reflected to a third refractive surface  61 . In this case, the shape of the reflective surface  50  must satisfy a condition that all light rays incident thereon have incident angles larger than a critical angle, so that the light rays are totally reflected by the reflective surface  50 , thereby changing travel directions of the light rays. 
     The light-modulating composite refractive surface  60  has the third refractive surface  61  and a fourth refractive surface  62 . The light-modulating composite refractive surface  60  serves to modulate light rays reflected by the reflective surface  50  and light rays refracted by the first refractive surface  31 . Outgoing paths of the light rays can be modulated by properly designing the light-modulating composite refractive surface  60 , so that light rays emitted from the LED light source  15  are collimated and uniform. 
     The third refractive surface  61  is an arbitrary curved surface defined by a function and symmetric with respect to the central axis  21 . The third refractive surface  61  has a first periphery connected with a second periphery of the reflective surface  50  to form a third joint line  24 , and is located to modulate light rays reflected by the reflective surface  50 . Moreover, the third refractive surface  61  has a shape allowing light rays incident thereon to have incident angles smaller than the critical angle, so that the light rays are refracted out of the light source-modulating device  20  nearly parallel to the central axis  21 . In other words, outgoing light rays from the third refractive surface  61  have very small divergence angles and are considerably collimated. 
     The fourth refractive surface  62  is an arbitrary curved surface, such as a convex surface, symmetric with respect to the central axis  21  and has a periphery connected with a second periphery of the third refractive surface  61  to form the fourth joint line  25 . In addition, the fourth refractive surface  62  is located to modulate incident light rays from first refractive surface  31 . A shape of the fourth refractive surface  62  can be designed to allow light rays incident thereon to have incident angles smaller than the critical angle, so that the light rays which have been refracted by the first refractive surface  31  are refracted once again, and the light rays refracted out of the light source-modulating device  20  are nearly parallel to the central axis  21 . In other words, outgoing light rays emitted from the light source-modulating device  20  are considerably collimated. 
     In order to fine-tune a collimation and uniformity of outgoing light rays emitted from the light source-modulating device  20  of the embodiment of the present invention, the shape of the third refractive surface  61  can be further designed. As shown in  FIGS. 5 ,  6  and  7 , a first distance D 1  can be designed to be greater than a second distance D 2  (D 1 &gt;D 2 ), wherein the first distance D 1  is a vertical distance between the third joint line  24  and the base surface  40 , and the second distance D 2  is a vertical distance between the fourth joint line  25  and the base surface  40 . Or alternatively, as shown in  FIGS. 8 ,  9  and  10 , the first distance D 1  and the second distance D 2  can be both designed to be greater than a third distance D 3  (D 1 &gt;D 3  and D 2 &gt;D 3 ), wherein the third distance D 3  is a vertical distance between a lowest point of the third refractive surface  61  and the base surface  40 . 
     Take for example the light source-modulating device  20  having composite curved surfaces in  FIG. 7 , wherein the light source-modulating device  20  is of a circularly symmetric structure. An optical simulation software ASAP (Advanced System Analysis Program) from the Breault Research Organization in the United States was used to simulate a light pattern and an illuminance distribution of the light source-modulating device  20  having composite curved surfaces in  FIG. 7  on a plane approximately  18  mm from the LED light source  15 , as shown in  FIGS. 11 and 12 , respectively. The light pattern has an effective, uniform range with a diameter of approximately  15  mm while the illuminance is uniformly distributed. In addition, there are no more concentric circles in the light pattern. In other words, outgoing light rays emitted from the light source-modulating device  20  having composite curved surfaces are considerably collimated and have a very uniformly distributed illuminance. 
     The light source-modulating device  20  having composite curved surfaces according to the embodiment of the present invention serves to collimate light rays emitted from the LED light source  15  and provide the light rays with a uniform illuminance. Therefore, it is advised to first analyze an LED light source  15  to be modulated, and then plan and design the light-distributing composite refractive surface  30 , the reflective surface  50  and the light-modulating composite refractive surface  60  of the light source-modulating device  20  according to a desired distance and range of illumination, so as to achieve such illumination distance and range. 
     It should be noted that the embodiments of the present invention as described above are intended to demonstrate features of the present invention, so that a person skilled in the art can understand the content disclosed herein and carry out the present invention accordingly. However, these embodiments are not intended to limit the scope of the present invention. Therefore, all equivalent modifications and alterations should be encompassed by the appended claims provided such modifications and alterations do not depart from the spirit of the present invention.