Patent Publication Number: US-2010109576-A1

Title: General illumination system and an illuminaire

Description:
TECHNICAL FIELD 
     The present invention relates to a lighting system, and an illuminaire. 
     BACKGROUND ART 
     Light emitting diode (LED) technology develops rapidly. The increasing amount of lumen per LED package together with the decreasing amount of money per lumen may in the future introduce LED technology on a large scale to the general lighting market. 
     Commercial departments may use the looks of an illumination system in order to distinguish themselves from their competitors. Therefore, there is a need for a generic lighting system that can be customized after installation. It is also desirable that the system can be changed easily, such that a new system or illumination pattern may be created in e.g. the ceiling at low cost. This may be desirable due to season changes, discount offers etc. 
     Therefore, it is a problem to design such illuminaire. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a lighting system having increased functionality. 
     Hence, a lighting system is provided comprising a light guide, a light source arranged for coupling light into the light guide, 
     wherein the light guide is arranged such that at least part of the light is emitted in a first general direction, and 
     at least part of the light is emitted in a second general direction different to the first direction. 
     The inventive lighting system is advantageous in that it simultaneously may provide a general illumination and an illumination of e.g. an object. 
     The light coupled out from the light guide in the first general direction may be collimated, which is advantageous in that glare is avoided or reduced. 
     The light coupled out from the light guide in the second general direction may be divergent, which is advantageous in that e.g. an object may be illuminated uniformly. 
     The light guide may be a light guide plate. 
     The second general direction may be opposite to the first direction. 
     The light source may be a solid state light source. The solid state light source may be a light emitting diode. 
     The lighting system may comprise a plurality of light sources arranged for coupling light into the light guide. The plurality of light sources may be arranged in a distribution in a plane at the light guide. At least one section of the light source distribution may comprise an incoupling facet for coupling light from any light source into the light guide and a first outcoupling facet for coupling light out of the light guide in the first general direction, which is advantageous in that no external components are used for incoupling of light and outcoupling of light in the first general direction. At least one light source of said plurality of light sources may comprise a collimator, which is advantageous in that annoying glare is avoided or reduced in a simple way. 
     The section of the LED distribution further comprises a second outcoupling facet arranged for coupling light out of the light guide in the second general direction the section of the LED distribution further comprises a second outcoupling facet arranged for coupling light out of the light guide in the second general direction. 
     The section of the light source distribution may further comprise a second outcoupling facet arranged for coupling light out of the light guide in the second general direction, which is advantageous in that no external components are used for outcoupling of light in the second general direction. 
     Each first outcoupling facet may be opposite to corresponding incoupling facet, which is advantageously in that the fabrication is made easily. 
     The first or second, or both of the outcoupling facets may be reflective and tilted in relation to the plane of the light guide, which is advantageous in that less or no light from a LED will penetrate into another section, which would degrade light efficiency due to absorption or scattering at other light sources. 
     The second outcoupling facet may be curved, which is advantageous in that the extracted light may have a wider angular spread. This may also be accomplished by an outcoupling facet comprising a rough and diffusive reflecting surface. 
     The second outcoupling facet may be adjacent to the first outcoupling facet, which is advantageous in that the first and the second outcoupling facets may be manufactured in a simple way. 
     The first outcoupling facet and the second outcoupling facet may form a common v-shape, which is advantageous in that it is easy to adjust the amount of light extracted in the two different directions. 
     The second outcoupling facet may be arranged adjacent to the LED, which is advantageous where unmixed light is to be extracted in the second direction. 
     At least one LED of said plurality of LEDs may comprise a collimator and the collimator may comprise the second outcoupling facet, which is advantageous in that it makes use of less components. 
     The lighting system may further comprise an electronic control unit arranged to individually control at least one of the LEDs, which is advantageous in that a light pattern may be created. 
     According to another aspect of the invention, a transparent illuminaire may comprise a lighting system according to the invention. This is advantageous in that a discreet, elegant, stylish or attractive lamp may be created. For example, the lamp can be transparent such that a viewer can see the ceiling, where for example an image or a neat stucco work is present, through the lamp. 
     Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “divergent” are to be interpreted openly as referring to a state of light where the incorporated light beams are spread from each other in the direction of travel. Compared to collimated light, the term “divergent light” means light having a broader angular distribution. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which 
         FIG. 1  is a top view according to an embodiment of the present invention, 
         FIG. 2  is a top view according to a second embodiment of the present invention, 
         FIG. 3  is a side view of a section of the lighting system according to a third embodiment, 
         FIG. 4  is a side view of a section of the lighting system according to a fourth embodiment, 
         FIG. 5  is a side view of a section of the lighting system according to a fifth embodiment, 
         FIG. 6  is a side view of a section of the lighting system according to a sixth embodiment, 
         FIG. 7  is a side view of an alternative geometry for an illuminaire using LEDs,  FIG. 8  is a side view of a second alternative geometry for an illuminaire using LEDs, and 
         FIG. 9  is a side view of a lighting system of the present invention in use. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
       FIG. 1  illustrates a first embodiment of the present invention. A lighting system  1  comprises a light guide plate  3  and a plurality of light sources  5 , in this exemplary embodiment light emitting diodes (LEDs), arranged in a staggered distribution  7 . The LED distribution has a plurality of sections  9  and each such section  9  comprises an incoupling facet  11 , a first outcoupling facet  13  and a second outcoupling facet  15 . 
     It is to be noted that other light sources, which may be fluorescent or incandescent lamp, or a solid state light source, such as the exemplary LED or a solid state laser, can be used in any of the embodiments. Slight modifications may be necessary. For example, if a laser is used, no collimation is needed. 
     It is further to be noted that the number of light sources can be any from one to a large plurality, depending on how the lighting system is to be designed and used. 
       FIG. 2  illustrates a second embodiment of the present invention, where a lighting system  1  comprises a light guide plate  3  and a plurality of LEDs  5 , arranged in a staggered distribution  7 . The LED distribution has a plurality of sections  9  and each such section  9  comprises an incoupling facet  11 , a first outcoupling facet  13  and a second outcoupling facet  115  arranged on a collimator  125 . 
     In  FIG. 3  a section  9  according to an embodiment of the present invention is described in more detail. The LED  5  is positioned in a portion  17  of the light guide plate  3 . The portion  17  may for example be an excess, a hole or a portion comprising a different light guide material. The LED  5  may also be moulded or mounted in any other suitable way into the light guide plate  3 . The LED  5  emits light in a general light emitting direction  19  and with an angular distribution that depends on the used LED. Thus, the emitted light may form a beam profile of any type common for LED technology. The LED  5  may be a side emitting LED or a top emitting LED tilted about  90  degrees. The general light emitting direction  19  is towards the incoupling facet  11 . The incoupling facet  11  is arranged perpendicular to the plane of the light guide plate  3 , therefore the incident light is not reflected when it transmits into the light guide plate  3 . 
     The first outcoupling facet  13  is positioned opposite to the incoupling facet  11 , i.e. the light emitted from the LED  5  in the light emitting direction  19  will not be incident on the first outcoupling facet  13 . The first outcoupling facet  13  is arranged inclined to the plane of the light guide plate  3 . The second outcoupling facet  15  is positioned adjacent to the first outcoupling facet  13  such that the first and the second outcoupling facet  13  and  15  forms a V-shape. The level of inclination of the first and the second outcoupling facet  13  and  15  is set as design parameters, as well as the physical proportions of the first and second outcoupling facet  13  and  15 . 
     The light emitted from the LED  5  in the light emitting direction  19  is incident on the incoupling facet  11 . The light is transmitted into the light guide plate  3  and propagates in said light guide plate  3  under total internal reflection (TIR). The beam profile of the LED  5  may be collimated. Due to the TIR condition, light from several LEDs  5  is mixed in the light guide plate  3 . 
     After the light has propagated in said light guide plate  3 , a first part of the light will be incident on a first outcoupling facet  13 . Since the first outcoupling facet  13  is slanted, the TIR condition will not be valid any longer, and the first part of the light will be reflected and extracted from the light guide plate  3  in a first general direction  21 . The reflection of the light may be further enhanced by making the first outcoupling facet  13  in a light reflecting material, such as a metal. 
     A second part of the light which is propagating in the light guide plate  3  will be incident on the second outcoupling facet  15 . Since the second outcoupling facet  15  is slanted in a direction opposite to the first outcoupling facet  13 , the TIR condition will not be valid and the second part of the light will be reflected and extracted from the light guide plate  3  in a second general direction  23  opposite to the first general direction  21 . The amount of light extracted in the different directions  21  and  23  may be adjusted by individually changing the lengths of the V-shape formed by the first and second outcoupling facets  13  and  15 . If an equal amount of light in both directions  21  and  23  is desirable, for example, the first and second outcoupling facets  13  and  15  should be equally arranged components, i.e. they should form a symmetrical V-shape. 
       FIG. 4  illustrates a second embodiment where a section  9  comprises a light guide plate  3  and a portion  17 . The portion  17  comprises a LED  5  and a collimator  125 . The collimator  125  is positioned between the LED  5  and the incoupling facet  11 . Alternatively, the collimator can be a part of the light guide, e.g. being integrated in the light guide plate. In this alternative embodiment, there is no incoupling facet. Returning to the embodiment illustrated in  FIG. 4 , opposite to said incoupling facet  11 , a first outcoupling facet  13  is arranged at the interface between the portion  17  and the light guide plate  3 . The collimator  125  comprises a second outcoupling facet  115 , facing the LED  5 . 
     The light emitted from the LED  5  has a direction  19 , and the light is incident on the collimator  125 . A first part of the light is incident on the planar surface of the collimator  125 , collimated by said collimator  125  and emitted out from the collimator  125  and thereby incident on the incoupling facet  11 . When the first part of the light enters the light guide plate  3 , it will travel under substantially total internal reflection in the light guide plate  3  and mix with light emitted from other LEDs  5  present in the lighting system  1  until it is incident on a first outcoupling facet  13 . The first part of the light may then be extracted from the light guide plate  3  in a first general direction  121 . A second part of the light emitted from the LED  5  will however be incident on the slanted surface of the collimator, i.e. the second outcoupling facet  115 . The second part of the light will then be reflected and extracted out from said portion  17  in a second general direction  123  opposite to said first general direction  121 . The second part of the light is then unmixed, which means that each LED  5  will extract collimated and mixed light in the first general direction  121 , and divergent and unmixed light in the second direction  123 . 
       FIGS. 5 and 6  illustrates alternative embodiments of the portion  17 . In  FIG. 5 , an optical component  227  is arranged between the LED  5  and the collimator  225 . The optical component  227  comprises an outcoupling facet  215 . In  FIG. 6  the optical component  227  is arranged between the collimator  225  and the incoupling facet  11 . 
     Although specific embodiments of the present invention have been described above, different geometries or designs for incoupling and mixing of light can be applicable for the present invention. 
       FIGS. 7 and 8  illustrates alternative geometries for luminaries using LEDs and a light guide for mixing the light. In  FIG. 7 , a light guide plate  3  is shown having a plurality of LEDs  5  arranged in the plane of the light guide  3 . Adjacent to each LED  5 , a mirror strip  35  is arranged for incoupling of light into the light guide plate  3 . An asymmetric redirection foil  33  is arranged adjacent to the light guide plate  3  for changing the direction of the light outcoupled from the light guide plate  3 . 
     In  FIG. 8 , another illuminaire geometry is shown. A plurality of LEDs  5  are arranged on a printed circuit board  37  that also comprises a plurality of slots. A light guide plate  3  comprises mini wedges, and the light guide plate  3  is arranged such that the plurality of LEDs  5  are arranged in a plane at the light guide plate  3 . Collimator strips  39  are arranged adjacent to the LEDs  5  for incoupling of light into said light guide  3 . Each collimator strip  39  comprises surrounding mirror strips  41 . An asymmetric redirection foil  33  is arranged adjacent to the light guide plate  3  for changing the direction of the light outcoupled from the light guide plate  3 . 
       FIG. 9  illustrates an embodiment of a lighting system  1 , attached to a ceiling but similar applies, which can be readily understood, for any mounting, such as of a wall etc. The lighting system  1  emits collimated light in a first general direction  21  towards the floor thus creating a general illumination, and light in a second direction  23 . The light emitted in the second direction  23  may be collimated or non-collimated, i.e. divergent. An object  29  can be attached to the ceiling above the lighting system  1 , such that the object  29  is illuminated by the light emitted from the lighting system  1  in the second direction  23 . Due to the different degree of collimation of the light emitted in the first direction  21  and the light emitted in the second direction  23 , a spectator  31  watching the illuminated object  29  will not be glared by the general illumination. 
     Now referring to  FIGS. 4 ,  5 ,  6 , and  9 , in a further embodiment, each LED  5  arranged in the distribution  7  may be controlled individually by a control unit. The LEDs  5  may emit light in different colors, and since mixed light is extracted in the first general direction  21 ,  121  the general illumination will be of homogenous color. However, the light which is extracted in the second direction  23 ,  123  is divergent and unmixed, and will create a bright spot on the ceiling. Since the LEDs  5  can be individually controlled, a static or dynamic picture can be created on the ceiling. The light emitted in the second general direction  23 ,  123  may also be collimated in order to achieve a more distinct light spot from each LED  5 . The distance between the lighting device  1  and the ceiling determines the size of the spot, and typically this distance may be about the same distance between two LEDs. For such application, the resolution may be approximately one LED per cm 2 . By using low power LEDs, in the order of 60 mW, the overall power consumption of the lighting system  1  is lowered and the need for a heat management system such as a heat sink is eliminated. It should be noted that improvements in LED efficiency, and/or the use of higher power LEDs, will allow for larger LED spacing, while keeping the light output of the lighting device the same. The control unit may use a column and row driving scheme which is well known from prior art and widely used for active electronic displays like LCD, OLED etc. 
     The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.