WO2013115864A1

WO2013115864A1 - Center-lit lighting assembly

Info

Publication number: WO2013115864A1
Application number: PCT/US2012/062402
Authority: WO
Inventors: Timothy A. Mccollum; Fumitomo Hide; Gregg M. Podojil; Ian Hardcastle
Original assignee: Rambus Inc.
Priority date: 2012-02-03
Filing date: 2012-10-29
Publication date: 2013-08-08

Abstract

A lighting assembly has a light guide (120) with light guide portions (LGPs, 122, 124) each having a distal edge (134, 144) and a castellated proximal edge (136, 146) in which first edge segments (150, 160) alternate with second edge segments (152, 162) that are offset from the first edge segments towards the distal edge. The LGPs are arranged with the first edge segments of one abutting the second edge segments of the other. Each LGP tapers such that it is thicker than the other at its first edge segments to define respective light input edge segments. Respective solid-state light emitters are located adjacent the light input edge segments of each LGP to input light to the LGP. The light propagates along the LGP by total internal reflection at the major surfaces thereof. Each LGP additionally includes light extracting elements at at least one of its major surfaces to extract light through the front major surface thereof.

Description

Center-Lit Lighting Assembly Background

[0001] Lighting assemblies used in general lighting and display applications locate solid-state light emitters such as light-emitting diodes (LEDs) adjacent one edge of a light guide. Light input to the light guide propagates along the light guide by total internal reflection at the major surfaces of the light guide. Light extracting elements located at at least one of the major surfaces of the light guide selectively extract light from the light guide through one or both major surfaces. The extracted light has a defined intensity profile, such as a uniform intensity profile, and a defined light ray angle distribution. In this disclosure, intensity profile refers to the variation of intensity with position within a light-emitting region. The term light ray angle distribution is used herein to describe the variation of the intensity of light with ray angle (typically a solid angle) over a defined range of light ray angles.

[0002] In some applications, the aesthetics of a lighting fixture of which the lighting assembly forms part, or of a display backlit by the lighting assembly, are impaired by the need to locate the solid state light emitters at the edge of the light guide. What is needed is a lighting assembly in which the solid-state light emitters are not located at the edge of the light guide so that light is emitted from the entire width or height of the lighting assembly or display.

However, relocating the solid-state light emitters away from the edge of the light guide typically gives rise to dark spots or bright lines in the light output from the lighting assembly.

Brief Description of the Drawings

[0003] Figures 1A, IB and 1C are respectively a perspective back view, an end view and a perspective front view showing an example of an embodiment of a lighting assembly as disclosed herein.

[0004] Figures 2A, 2B and 2C are respectively a perspective back view, a side view and an end view showing an example of the first light guide portion of the lighting assembly shown in Figures 1A-1C in which the taper is confined to the castellated proximal edge.

[0005] Figure 3 A is an exploded perspective view showing an example of the light guide of the lighting assembly in the course of assembling the first and second light guide portions to form the light guide. [0006] Figure 3B is a perspective view showing the light guide shown in Figure 3A when its assembly is complete.

[0007] Figure 4 is a perspective view showing the front major surface of the light guide

example shown in Figures 3A and 3B.

[0008] Figure 5 is a perspective back view showing an example of the light guide of the lighting assembly in which the light guide is a monolithic light guide that includes the first light guide portion and the second light guide portion.

[0009] Figures 6A, 6B and 6C are respectively a perspective back view, a side view and an end view showing the location of the solid-state light emitters relative to the first light guide portion of the lighting assembly shown in Figures 1A-1C.

[0010] Figure 7A is an enlarged partial side view showing respective light attenuating elements interposed between the back major surfaces of the light guide portions and the solid-state light emitters of the lighting assembly shown in Figures 1A-1C.

[0011] Figure 7B is a perspective view showing the positions of the light attenuating elements relative to the back major surfaces of the light guide portions of the lighting assembly shown in Figures 1A-1C.

[0012] Figure 7C is a perspective view showing light propagation within the light guide

portions of the lighting assembly shown in Figures 1A-1C.

[0013] Figures 8A and 8B are respectively a perspective back view and a side view showing an example the first light guide portion of the lighting assembly shown in Figures 1A and IB in which the light guide portion progressively tapers in thickness from the first proximal edge segments to the distal edge.

[0014] Figures 9A and 9B are respectively a perspective back view and an end view showing an example of the lighting assembly shown in Figures 1A-1C in which the solid-state light emitters are mounted on a printed circuit board.

[0015] Figures 10A and 10B are respectively a perspective view and an edge view showing an example of another embodiment of a lighting assembly as disclosed herein.

[0016] Figure 11 is a schematic drawing showing an example of a display in which a display panel is back lit by a lighting assembly as disclosed herein.

[0017] Figure 12 is a schematic drawing showing an example of a lighting fixture that

incorporates a lighting assembly as disclosed herein. Description

[0018] In an embodiment, a lighting assembly as disclosed herein includes a light guide that includes a first light guide portion and a second light guide portion. Each light guide portion includes a front major surface and a back major surface offset from one another in a thickness direction, a distal edge extending between the major surfaces, and castellated proximal edge opposite the distal edge. The proximal edge of each light guide portion includes first proximal edge segments alternating with second proximal edge segments with the second proximal edge segments offset from the first proximal edge segments towards the distal edge. The light guide portions are arranged with the first proximal edge segments of each light guide portion abutting the second proximal edge segments of the other light guide portion. Each light guide portion is tapered in thickness such that, at each first proximal edge segment of the light guide portion, the light guide portion is thicker than the other light guide portion to define a respective light input edge segment. The lighting assembly additionally includes solid-state light emitters and light extracting elements. A respective solid-state light emitter is located adjacent each light input edge segment to input light to the light guide portions. Light from the solid-state light emitters propagates along the light guide portions by total internal reflection at the major surfaces of the light guide portion. The light extracting elements are at at least one of the major surfaces of each light guide portion to extract light from the light guide portion through the front major surface of the light guide portion.

[0019] In another embodiment, a lighting assembly includes solid-state light emitters and a light guide. The light guide includes a front major surface and a back major surface offset from one another in a thickness direction, a first edge extending between the major surfaces, and second edge opposite the first edge. The light guide additionally includes first light input structures alternating with second light input structures arrayed nominally parallel to the first edge. The light input structures protrude from the back major surface of the light guide part-way between the first edge and the second edge. Each of the first light input structures includes a respective first light input edge segment closer to the second edge than the first edge, and tapers in thickness from the first light input edge segment towards the first edge. Each of the second light input structures comprises a respective second light input edge segment closer to the first edge than the second edge, and tapers in thickness from the second light input edge segment towards the second edge. Each of the solid-state light emitters is located adjacent a respective light input edge segment to input light to the light guide. Light from the solid-state light emitters propagates along the light guide by total internal reflection at its major surfaces. The light guide additionally includes light extracting elements at at least one of its major surfaces to extract light from the light guide through the front major surface.

[0020] Figures 1A, IB and 1C show an example of a lighting assembly 100. Lighting assembly 100 includes solid-state light emitters, an exemplary one of which is shown at 110, and a light guide 120. Throughout this disclosure, a reference numeral that refers to an exemplary element is also used to refer to the elements collectively. Thus, reference numeral 110 is used herein to refer to the solid-state light emitters collectively. Light guide 120 includes a first light guide portion 122 and a second light guide portion 124.

[0021] Figures 2A, 2B and 2C show an example of first light guide portion 122. Second light guide portion 124 is typically identical to first light guide portion 122 and will therefore not be separately described. However, reference numerals for corresponding elements of second light guide portion 124 that will be referred to in the description below are set forth in parentheses in the following description. First light guide portion 122 includes a front major surface 130 (140) and a back major surface 132 (142) offset from one another in the thickness direction of first light guide portion 122. First light guide portion 122 additionally includes a distal edge 134 (144), and a castellated proximal edge 136 (146) opposite distal edge 134 (144).

[0022] Castellated proximal edge 136 (146) includes first proximal edge segments, an

exemplary one of which is shown at 150 (160), alternating with second proximal edge segments, an exemplary one of which is shown at 152 (162, Figures 3 A and 3B). Second proximal edge segments 152 (162) are offset from first proximal edge segments 150 (160) towards distal edge 134 (144). A respective third proximal edge segment extends from the end of each first proximal edge segment 150 (160) to the end of the adjacent second proximal edge segment 152 (162). An exemplary third proximal edge segment is shown at 154 (164).

[0023] Light guide portions 122, 124 are arranged with the first proximal edge segments of each light guide portion abutting the second proximal edge segments of the other light guide portion. Figure 3 A shows an example of light guide 120 in which light guide portions 122, 124 are separate components optically bonded to one another to form light guide 120. Figure 3 A shows light guide 120 in the course of assembly: the first proximal edge segments 150 of first light guide portion 122 face the second proximal edge segments 162 of second light guide portion 124, and the first proximal edge segments 160 of second light guide portion 124 face the second proximal edge segments 152 of first light guide portion 122. Additionally, the third proximal edge segments 154 of first light guide portion 122 face the third proximal edge segments 164 of second light guide portion 124.

[0024] Figure 3B shows light guide 120 when its assembly is complete. The first proximal edge segments 150 of first light guide portion 122 abut the second proximal edge segments 162 of second light guide portion 124, and the first proximal edge segments 160 of second light guide portion 124 abut the second proximal edge segments 152 of first light guide portion 122. Additionally, the third proximal edge segments 154 of first light guide portion 122 abut the third proximal edge segments 164 of second light guide portion 124.

[0025] Figure 4 shows the front major surface 121 of the example of light guide 120 shown in Figures 3 A and 3B in which the light guide is made by assembling light guide portions 122, 124. The front major surfaces 130, 140 of light guide portions 122, 124 constitute the front major surface 121 of light guide 120. In the example shown in Figure 4, front major surfaces 130, 140 are planar and are co-planar in front major surface 121.

[0026] Figure 5 shows an example of a monolithic embodiment of light guide 120 that includes light guide portions 122, 124. In this example, the first proximal edge segments 150 of first light guide portion 122 abut the second proximal edge segments 162 of second light guide portion 124, and the first proximal edge segments 160 of second light guide portion 124 abut the second proximal edge segments 152 of first light guide portion 122. Additionally, the third proximal edge segments 154 of first light guide portion 122 abut the third proximal edge segments 164 of second light guide portion 124.

[0027] Hence, more than one construction technique is disclosed. In one embodiment, the

construction technique involves mating first light guide portion 122 with second light guide portion 124 to construct the light guide 120 as shown, for example, in Figures 3A through 4. In this embodiment, the parts are joined using adhesive, welding, chemical bonding, heat bonding, or the like, or are mechanically held in a desired arrangement with respect to each other. As indicated, the light guide portions optically interact as desired to have optical isolation between them or optical coupling between them. In another embodiment, the construction technique involves fabricating the light guide 120 as a monolithic light guide inclusive of the first and second light guide portions 122, 124 as shown, for example in Figures 1A-1C and 5. In either case, monolithic light guide 120 or the components of an assembled light guide 120 (e.g., separate light guide portions 122 and 124) are made by a technique such as injection molding or machining from stock material.

[0028] Referring again to Figure 1 A, light guide portions 122, 124 are tapered in thickness such that, at each first proximal edge segment of each light guide portion, the light guide portion is thicker than the other light guide portion to define a respective light input edge segment. First light guide portion 122 is tapered in thickness such that, at each first proximal edge segment 150 of the first light guide portion, the first light guide portion is thicker than second light guide portion 124 to define a respective light input edge segment that will be referred to as a first light input edge segment. An exemplary first light input edge segment of first light guide portion 122 is shown at 156. Second light guide portion 124 is tapered in thickness such that, at each first proximal edge segment 160 of the second light guide portion, the second light guide portion is thicker than first light guide portion 122 to define a respective light input edge segment that will be referred to as a second light input edge segment. An exemplary second light input edge segment is shown at 166.

[0029] A respective solid-state light emitter 110 is located adjacent each light input edge

segment 156, 166 to input light to light guide portions 122, 124. Light from solid-state light emitters 110 propagates along light guide portions 122, 124 by total internal reflection at the major surfaces 130, 132; 140, 142 of the light guide portions. Respective solid-state light emitters 110 adjacent first light input edge segments 156 are referred to herein as first solid- state light emitters, an exemplary one of which is shown at 112. Respective solid-state light emitters 1 10 adjacent second light input edge segments 166 are referred to herein as second solid-state light emitters, an exemplary one of which is shown at 114. A respective one of the first solid-state light emitters 112 is located adjacent each first light input edge segment 156 to input light to first light guide portion 122, and a respective one of the second solid-state light emitters 114 is located adjacent each second light input edge segment 166 to input light to second light guide portion 124. Light from first solid-state light emitters 112 propagates along first light guide portion 122 by total internal reflection at the major surfaces 130, 132 of the first light guide portion. Light from second solid-state light emitters 114 propagates along second light guide portion 124 by total internal reflection at the major surfaces 140, 142 of second light guide portion.

[0030] Figures 6A, 6B and 6C shows the location of respective first solid-state light emitters 112 adjacent the first light input edge segments 156 of first light guide portion 122. Each first light input edge segment 156 is part of a respective first proximal edge segment 150 of first light guide portion 122 closer to the back major surface 132 of the first light guide portion than to the front major surface 130 thereof. Second solid-state light emitters 114 that input light to second light guide portion 124 are similarly located relative to the second light input edge segments 166 of the second light guide portion. Each second light input edge segment 166 is part of a respective first proximal edge segment 160 of second light guide portion 124 closer to the back major surface 142 of the second light guide portion than to the front major surface 140 thereof.

[0031] Referring again to Figure 1A, lighting assembly 100 additionally includes light

extracting elements at at least one of the major surfaces 130, 132; 140, 142 of each light guide portion 122, 124 to extract light from the light guide portion through the front major surface 130, 140 of the light guide portion. Light extracting elements located on, in or under a major surface of light guide portion 122, 124 are referred to herein as being located "at" the respective major surface of the light guide portion. In the example shown, light extracting elements are located on the back major surfaces 132, 142 of first light guide portion 122 and second light guide portion 124. An exemplary light extracting element located on the back major surface 142 of second light guide portion 140 is shown in the enlarged portion of Figure lA at 180.

[0032] Referring now to Figure 7A, a light attenuating element 116 is interposed between

second solid-state light emitter 114 and the back major surface 132 of first light guide portion 122 adjacent the exemplary second light input edge segment 166 of second light guide portion 124. Light attenuating element 116 has a light attenuating property that reduces the intensity of stray light from second solid-state light emitter 114 that enters first light guide portion 122 through the back major surface 132 thereof. The reduced intensity prevents such stray light from causing a bright spot in the light output by the first light guide portion. In an

embodiment, light attenuating element 116 is opaque and/or reflective and prevents stray light output by second solid-state light emitter 114 from entering first light guide portion 122. Typically, light attenuating element 116 is affixed to or otherwise coupled to second solid- state light emitter 114. Figure 7B shows the location of light attenuating element 116 adjacent second light input edge segment 166. A respective light attenuating element is located adjacent each second light input segment 166, but the light attenuating elements adjacent the remaining second light input edge segments 166 have been omitted to simplify the drawing.

[0033] Additionally, a light attenuating element 117 is interposed between the first solid-state light emitter 112 and the back major surface 142 of second light guide portion 124 adjacent the exemplary first light input edge segment 156 of first light guide portion 122. Light attenuating element 117 has a light attenuating property that reduces the intensity of stray light from first solid-state light emitter 112 that enters second light guide portion 124 through the back major surface 142 thereof. The reduced intensity prevents such stray light from causing a bright spot in the light output by the second light guide portion. In an embodiment, light attenuating element 117 is opaque and/or reflective and prevents stray light from the first solid-state light emitter 112 from entering second light guide portion 124 and causing a bright spot in the light output by the second light guide portion. Typically, light attenuating element 117 is affixed to or otherwise coupled to first solid-state light emitter 112. Figure 7B shows the location of the light attenuating element 117 adjacent first light input edge segment 156. A respective light attenuating element is located adjacent each first light input segment 156, but the remaining light attenuating elements have been omitted to simplify the drawing.

[0034] First solid-state light emitter 112 is located adjacent first light input edge segment 156 to input light to first light guide portion 122. Light attenuating element 117 is interposed between the back major surface 142 of second light guide portion 124 and first solid-state light emitter 112. Light attenuating element 117 prevents stray light from first solid-state light emitter 1 12 from passing through second light guide portion 124 and being emitted from the front major surface 140 of the second light guide portion, or attenuates the intensity of such stray light. Second solid-state light emitter 114 is located adjacent light input edge segment 166 to input light to second light guide portion 124. Light attenuating element 116 is interposed between the back major surface 132 of first light guide portion 122 and solid-state light emitter 114. Light attenuating element 116 prevents stray light from solid-state light emitter 114 from passing through first light guide portion 122 and being emitted from the front major surface 130 of the first light guide portion, or attenuates the intensity of such light. Light attenuating elements 116, 117 are located in front of solid-state light emitters 114, 112, respectively, to prevent stray light from solid-state light emitters 114, 112 causing bright spots in the light output from front major surfaces 130, 140, respectively.

[0035] As noted above with reference to Figures 1A-1C, light extracting elements 180 are

located at at least one of the respective major surfaces 130, 132, 140, 142 of light guide portions 122, 124 to extract light from the light guide portion through its front major surface 130, 140. Typically the light extracting elements are located on the respective back major surface 132, 142 of each light guide portion 122, 124. Such light extracting elements reflect light propagating along the light guide portion from the light input edge segments 156, 166 thereof out through the front major surface 130, 140. To cause light to be emitted from the entire area of front major surfaces 130, 140, light extracting elements 180 are located in substantially all of the area of respective back major surfaces 132, 142. Light extracting elements 180 vary in one or more of area density, size, height, and depth with position on back major surfaces 132, 142 to extract light from the respective light guide portion 122, 124 with a defined intensity profile, such as a nominally-uniform intensity profile. Intensity profile characterizes the variation of the intensity of the extracted light with location on the front major surface 130, 140 of light guide portion 122, 124. The geometry of the light extracting elements defines the light ray angle distribution of the extracted light.

[0036] A particular region of the back major surface 132 of first light guide portion 122 in which light extracting elements 180 are located is a respective light extraction region adjacent each light input edge segment 166 of second light guide portion 124. Such light extracting region is in front of the light attenuating element 116 located in front of each first solid-state light emitter 112. An object in front of another object is aligned with the other object in a plane parallel to the front major surface 130, 140 and is closer to front major surface 130, 140 than the other object, and an object behind another object is aligned with the other object in the aforementioned plane and is further from the front major surface 130, 140 than the other object. Referring to Figures 7A and 7C, an exemplary light extraction region of the back major surface 132 of first light guide portion 122 is shown at 138. Similarly, a particular region of the back major surface 142 of second light guide portion 124 in which light extracting elements 180 are located is a respective light extraction region adjacent each light input edge segment 156 of first light guide portion 122. Such light extraction region is in front of the light attenuating element 117 in front of the each second solid-state light emitter 114. An exemplary light extraction region of second light guide portion 124 is shown at 148. An exemplary light extracting element 180 in light extraction region 148 is shown in the enlarged portion of Figure 7C. Light extraction regions 138, 148 are regions of back major surfaces 132, 142, respectively, in front of respective light attenuating elements 116, 117. In some embodiments, light extraction regions 138, 148 are larger in a plane parallel to front major surfaces 130, 140 than respective light attenuating elements 116, 117.

[0037] Referring to Figure 7C, light input edge segment 156 of first light guide portion 122 and first solid-state light emitter 112 adjacent thereto are configured to direct a portion 170 of the light from first solid-state light emitter 112 input through light input edge segment 156 towards the light extracting region 138 of the back major surface 132 of first light guide portion 122. Light portion 170 passes in front of an adjacent second solid-state light emitter identified by reference numeral 115 that inputs light to second light guide portion 124. Light extracting elements 180 located in light extracting region 138 extract at least some of the light portion 170 from first light guide portion 122 through the front major surface 130 of the first light guide portion. The light extracted from first light guide portion 122 in front of second solid-state light emitters 114 fills in dark areas that could otherwise appear in the light extracted through the front major surface 130 of the first light guide portion. Typically, light input edge segment 156 of first light guide portion 122 and first solid-state light emitter 112 adjacent thereto are additionally configured to direct another portion (not shown) of the light from first solid-state light emitter 112 input through light input edge segment 156 towards the light extracting region (not shown) in front of another adjacent second solid-state light emitter identified by reference numeral 118 and light extracting elements within the light extraction region extract at least part of the light through front major surface 130. The remaining first light input segments 156 and their respective first solid-state light emitters 112 are similarly configured to direct light in front of respective at least one adjacent second solid-state light emitter. In an example, light input edge segment 156 includes a lens array (not shown) to direct the light from first solid-state light emitter 112 as just described.

[0038] Similarly, light input edge segment 166 of second light guide portion 124 and second solid-state light emitter 114 are configured to direct a portion 172 of the light input through light input edge segment 166 towards light extracting region 148 of back major surface 142 of second light guide portion 124. Light portion 172 passes in front of a respective adjacent first solid-state light emitter identified reference numeral 113 that inputs light to first light guide portion 122. Light extracting elements 180 located in light extracting region 148 extract at least some of the light portion 172 from second light guide portion 124 through the front major surface 140 of the second light guide portion. The light extracted from second light guide portion 124 in front of first solid-state light emitters 112 fills in dark areas that could otherwise appear in the light extracted through the front major surface 140 of the second light guide portion. Typically, light input edge segment 166 of second light guide portion 124 and second solid-state light emitter 114 adjacent thereto are additionally configured to direct another portion (not shown) of the light from second solid-state light emitter 114 input through light input edge segment 166 towards a light extracting region 149 in front of another adjacent second solid-state light emitter (not shown) and light extracting elements within light extraction region 149 extract at least part of the light through front major surface 140. The remaining second light input segments 166 and their respective second solid-state light emitters 1 14 are similarly configured to direct light in front of respective at least one adjacent first solid-state light emitter. In an example, light input edge segment 166 includes a lens array (not shown) to direct the light from second solid-state light emitter 114 as just described.

[0039] In some embodiments, additional light extracting elements (not shown) are located at the front major surface 130 of first light guide portion 122 within light extraction region 138 to extract additional light from the first light guide portion in front of adjacent second solid-state light emitters 114, and additional light extracting elements (not shown) are located at the front major surface 140 of second light guide portion 124 within light extraction region 148 to extract additional light from the second light guide portion in front of first adjacent solid-state light emitters 112.

[0040] Light extracting regions 138 in which some of the light extracting elements 180 of first light guide portion 122 are located are in front of respective second solid-state light emitters 114 that input light to second light guide portion 124. Light extracting regions 148 in which some of the light extracting elements 180 of second light guide portion 124 are located are in front of respective first solid-state light emitters 112 that input light to first light guide portion [0041] Solid-state light emitters 112, 114 that input light to each light guide portion 122, 124 are located behind the back major surface 142, 132 of the other light guide portion 124, 122. As shown in Figure 7 A, first solid-state light emitters 112 that input light to first light guide portion 122 are located behind the back major surface 142 of second light guide portion 124, and second solid-state light emitters 114 that input light to second light guide portion 124 are located behind the back major surface 132 of first light guide portion 122.

[0042] Referring again to Figures 1A and 2A, each third proximal edge segment 154 of first light guide portion 122 extends non-orthogonally to first proximal edge segment 150 and second proximal edge segment 152. The non-orthogonal direction of the third proximal edge segments 154 at the opposite ends of each first proximal edge segment 150 enables light input by each first solid-state light emitter 112 at the respective light input edge segment 156 of first light guide portion 122 to spread laterally, including spreading in front of the adjacent second solid-state light emitters 114, as described above. Similarly, the non-orthogonal direction of the third proximal edge segments 164 at the opposite ends of each first proximal edge segment 160 of second light guide portion 124 enables light input by each second solid-state light emitter 114 at the respective light input edge segment 166 of second light guide portion 124 to spread laterally, including spreading in front of the adjacent first solid-state light emitters 112, as described above.

[0043] Referring to Figure 1A, in some embodiments, third proximal edge portion 154 is

oriented to totally internally reflect light input through adjacent light input edge segment 156. Similarly, third proximal edge portion 164 is oriented to totally internally reflect light input through adjacent light input edge segment 166. In other embodiments, third proximal edge portion 154 includes a reflective coating 158, and third proximal edge portion 164 includes a reflective coating 168.

[0044] In some embodiments, light guide portions 122, 124 constituting light guide 120 are separate components affixed to one another at their castellated proximal edges 136, 146 in a manner that optically isolates the light guide portions from one another. In an example, each light guide portion 122, 124 has a reflective or light-absorbing layer (not shown) on second proximal edge segments 152, 162 and at least one light guide portion 122, 124 has a reflective or light-absorbing layer (not shown) on third proximal edge segments 154, 164 to provide the optical isolation. Additionally, first solid-state light emitters 112 are independent of second so lid-state light emitters 114 to enable light guide portions 122, 124 to output light independently of one another. In an example, light guide portions 122, 124 output light independently of one another to provide local dimming in an application in which lighting assembly 100 is used to back light a display panel. In another example, light guide portions 122, 124 are arranged with their castellated proximal edges abutting but are neither optically bonded nor optically isolated.

[0045] In some embodiments, the first proximal edge segments 150 of first light guide portion 122 extend nominally parallel to the distal edge 134 of the first light guide portion.

Additionally or alternatively, the first proximal edge segments 160 of second light guide portion 124 extend nominally parallel to the distal edge 144 of the second light guide portion.

[0046] In some embodiments, each light guide portion 122, 124 progressively tapers in

thickness from first proximal edge segments 150, 160 to distal edge 134, 144. Figures 8A and 8B show an embodiment of first light guide portion 122 in which the light guide portion progressively tapers in thickness between first proximal edge segments 136 and distal edge 134. In the example shown in Figures 8A and 8B, both major surfaces 130, 140 are planar and back major surface 132 is tilted relative to front major surface 130 to provide the taper. In other embodiments (not shown), the taper stops part- way between proximal edge 136 and the distal edge 134, and the remainder of the light guide portion has a constant thickness. In such embodiments, front major surface 130 is planar and back major surface 132 is contoured: part of back major surface 132 adjacent proximal edge 136 is tilted relative to front major surface 130 to provide the taper and the remainder of back major surface 132 adjacent distal edge 134 is parallel to front major surface 130.

[0047] In other embodiments, the taper of each light guide portion 122, 124 is located within a region between the first proximal edge segments and the second proximal edge segments of the castellated proximal edge, and the remainder of the light guide extending from the second proximal edge segments to the distal edge is not tapered. In such embodiments, each light guide portion tapers in thickness between the first proximal edge segments and the second proximal edge segments of the castellated proximal edge. In the example of first light guide portion 122 shown in Figures 2A-2C, light guide portion 122 tapers progressively from the first proximal edge segments 150 to the second proximal edge segments 152 of castellated proximal edge 136. The remainder of first light guide portion 122 between second proximal edge segments 152 and the distal edge 134 is not tapered. In this example, front major surface 130 is planar and back major surface 132 is contoured: part of back major surface 132 between first proximal edge segments 150 and second proximal edge segments 152 is tilted relative to front major surface 130 to provide the taper, and the remainder of back major surface 132 extending from second proximal edge segments 152 to distal edge 134 is parallel to front major surface 130.

[0048] Second light guide portion 124 is tapered in ways similar to those just described with reference to first light guide portion 122 and will not be separately described. Moreover, in the examples described above, light guide portions 122, 124 have a linear taper. In other examples (not shown), the taper is non-linear.

[0049] In the example shown in Figure 1A, light guide 120 is rectangular in shape. In other examples, light guide 120 has other shapes, such as, but not limited to, square, polygonal, circular, and elliptical. In the example shown in Figure 1 A, rectangular light guide 120 has a greater width along distal edges 134, 144 than height between distal edges 134, 144. In other examples, rectangular light guide 120 has a greater height than width.

[0050] Figures 7A, 9A and 9B show an example of lighting assembly 100 in which solid-state light emitters 110 are mounted on a printed circuit board 190. Printed circuit board 190 mechanically supports the solid-state light emitters and provides electrical connections to the solid-state light emitters. In an embodiment in which first and second light guide portions 122, 124 are optically isolated from one another, the electrical connections provided by printed circuit board 190 to first solid-state light emitters 112 are separate from those provided to second solid-state light emitters 114. Printed circuit board 190 is directly or indirectly mechanically coupled to light guide 120 to locate the light output surface (not shown) of each first solid-state light emitter 112 in a defined positional relationship to a respective first light input edge segment 156 and to locate the light output surface (not shown) of each second solid-state light emitter 114 in a defined positional relationship to a respective second light input edge segment 166. In some embodiments, printed circuit board 190 is directly affixed to the back major surfaces 132, 142 of light guide portions 122, 124. In other embodiments, printed circuit board 190 and light guide 120 are affixed to a common mechanical support, such as a tray (not shown, but see Figures 11 and 12). In such embodiments, the tray is thermally conductive and printed circuit board 190 is thermally coupled to the tray to enable the tray to dissipate heat generated by solid-state light emitters 110.

[0051] In the embodiment of Figures 7 A, 9A and 9B, the first and second solid-state light

emitters 112, 114 are mounted to the printed circuit board 190 so that light output surfaces of the first and second solid-state light emitters 1 12, 114 are adjacent the respective light input edges 156, 166 in planes normal to the front major surfaces 130, 140 and the light input edges 156, 166 are parallel to the light output surfaces.

[0052] Solid-state light emitters 110 are typically light emitting diodes (LEDs) such as

semiconductor LEDs or organic LEDs (OLEDs). In the example shown in Figures 7 A, 9 A and 9B, solid-state light emitters 110 are side-fire LEDs mounted on printed circuit board 190 to input light to light guide 120 through first light input edge segments 156 and second light input segments 166.

[0053] Each of the solid-state light emitters 110 may be a broad-spectrum LED (e.g., a white light emitter) or may be composed of one or more LEDs (or LED dies) that emit light of a desired color or spectrum (e.g., red light, green light, blue light, or ultraviolet light), or a mixture of broad- spectrum LEDs and LEDs that emit narrow-band light of a desired color. In one embodiment, the solid-state light emitters 110 emit light with no operably-effective intensity at wavelengths greater than 500 nanometers (nm) (i.e., the solid-state light emitters 110 emit light at wavelengths that are predominantly less than 500 nm). In some embodiments, the LEDs that constitute each solid-state light emitter 110 all generate light having the same nominal spectrum. In other embodiments, at least some of the LEDs that constitute each solid- state light emitter 110 generate light that differs in spectrum from the light generated by the remaining LEDs that constitute each solid-state light emitter 110. In an example, each solid- state light emitter 110 includes two different types of LED.

[0054] Figures 10A and 10B shows an example of another embodiment of a lighting assembly that includes solid-state light emitters and a light guide 220. An exemplary solid-state light emitter is shown at 110. Light guide 220 includes a front major surface 230 and a back major surface 232 offset from one another in a thickness direction, a first edge 234 extending between the major surfaces 230, 232, and second edge 244 opposite the first edge. Light guide 220 additionally includes first light input structures alternating with second light input structures arrayed nominally parallel to first edge 234. An exemplary first light input structure is shown at 226. An exemplary second light input structure is shown at 228. Light input structures 226, 228 protrude from the back major surface 232 part-way, typically but not necessarily half-way, between first edge 234 and second edge 244.

[0055] Each first light input structure 226 includes a respective first light input edge segment 256 closer to second edge 244 than to first edge 234, and tapers in thickness from light input edge segment 256 towards first edge 234. Each second light input structure 228 includes a respective second light input edge segment 266 closer to first edge 234 than to second edge 244, and tapers in thickness from second light input edge segment 266 towards second edge 244. In the example shown, the taper of the first light input structures 226 is confined to a region between the light input edge segments 256 of the first light input structures and the light input edge segments 266 of the second light input structures, and the taper of the second light input structures 228 is confined to a region between the light input edge segments 266 of the second light input structures and the light input edge segments 256 of the first light input structures.

[0056] Each solid-state light emitter 110 is located adjacent a respective light input edge

segment 256, 266 to input light to light guide 220. Light from solid-state light emitters 110 propagates along light guide 220 by total internal reflection at major surfaces 230, 232. Light guide 220 additionally includes light extracting elements 180 at at least one of major surfaces 230, 232 to extract light from the light guide through front major surface 230.

[0057] In some embodiments, light guide 220 is a monolithic light guide. In other embodiments, light guide 220 is made by assembling two light guide portions each having a castellated proximal edge in a manner similar to that described above with reference to Figures 2A-2C, 3A, 3B and 4. Hence, more than one construction technique may be used to fabricate light guide 220. In one embodiment, the construction technique involves mating a first light guide portion similar to first above-described light guide portion 122 with a second light guide portion similar to above-described second light guide portion 124 to construct light guide 220 in a manner similar to that shown by example in Figures 3 A through 4. In this embodiment, the light guide portions are joined with adhesive, welding, chemical bonding, heat bonding, or the like, or are mechanically held in a desired arrangement with respect to each other. As indicated, the light guide portions optically interact as desired to have optical isolation between the parts or optical coupling between the light guide portion. In another embodiment, the construction technique involves fabricating light guide 220 as a monolithic item, as shown by example in Figures 10A and 10B. In either case, monolithic light guide 220 or the components of an assembled light guide 220 (e.g., separate light guide portions similar to light guide portions 122 and 124) are made by a technique such as injection molding or machining from stock material.

[0058] In other respects, lighting assembly 200 is similar to lighting assembly 100 and will therefore not be further described.

[0059] Figure 11 shows an example of a display 300 that includes a display panel 310, and a lighting assembly arranged to back light the display panel. In the example shown, above- described lighting assembly 100 is used to back light display panel 310. In other examples, above-described lighting assembly 200 is used to back light display panel 310. Display panel 310 includes a two-dimensional array of light valves 330. The light valves operate in response to an electrical signal, such as an electrical signal that represents a still picture or a motion picture, to spatially modulate the light extracted from the front major surface 130 of the light guide 120 of lighting assembly 100. Light valves based on various types of liquid crystals or various micromechanical devices can be used as light valves 330.

[0060] Since lighting assembly 100 is capable of emitting light from the entirety of the surface area of the front major surface 130 of light guide 120, a display panel having a narrow bezel, e.g., a bezel less than 8 mm wide, or even a zero-width bezel can be used as display panel 310. In the example shown in Figure 11, lighting assembly 100 is mounted in a narrow tray 340 that extends around the perimeter of and behind lighting assembly. Tray 340 is thermally coupled to the solid-state light emitters 110 of lighting assembly 100 to dissipate heat generated by the solid-state light emitters. Tray 340 is additionally used to mount display panel 310 in front of lighting assembly 100. In other examples, tray 340 is located exclusively behind lighting assembly 100, and display panel 310 is mounted in front of lighting assembly 100 without the use of a tray. In some embodiments, tray 340 is made of a reflective material, or includes a reflective insert. Stray light emitted from the back major surfaces 132, 142 of light guide portions 122, 124 is reflected by such embodiments of tray 340 back towards the light guide portions, propagates through the light guide portions and is emitted from the front major surfaces 130, 140 of the light guide portions. In one embodiment, the tray 340 or the reflective insert conforms to the back major surfaces 134, 142. [0061] In the example shown in Figure 11, a single lighting assembly 100 back lights display panel 310. In an embodiment, first light guide portion 122 is optically isolated from second light guide portion 124, and first solid-state light emitters 112 are operated independently of second solid-state light emitters 114. In this embodiment, first and second light guide portions 122, 124 emit light independently of one another to provide large-scale local dimming. In other examples (not shown), a one-dimensional array of lighting assemblies or a two- dimensional array of lighting assemblies 100 is used to back light display panel 310. In some embodiments, the lighting assemblies 100 in the array are not optically isolated from one another and the solid-state light emitters 110 that input light to the light guides are operated in unison.

[0062] In other embodiments, the lighting assemblies 100 in the array are optically isolated from one another and the solid-state light emitters 110 that input light to the light guides are operated independently of one another. In this embodiment, lighting assemblies 100 emit light independently of one another to provide smaller-scale local dimming. Optionally, the first light guide portion 122 of each lighting assembly 100 in the array is optically isolated from second light guide portion 124 thereof, and first solid-state light emitters 112 of each lighting assembly in the array are operated independently of second solid-state light emitters 114 of the lighting assembly to increase the spatial resolution of the local dimming.

[0063] In an embodiment of display 300 having an array of lighting assemblies 100, each

lighting assembly back lights a corresponding group of the light valves 330 of the display panel, and has a light output independently controlled for local dimming of display 300 according to brightness values in a video signal applied to display 300 for the corresponding group of light valves and the light output of the lighting assembly updated for each frame of the video signal.

[0064] Figure 12 shows an example of a lighting fixture 400 that includes a lighting assembly as disclosed herein. Lighting fixture 400 is used to provide light in various domestic, commercial and industrial applications. In the example shown, above-described lighting assembly 100 is used as part of lighting fixture 400. In other examples, above-described lighting assembly 200 is used is as part of lighting fixture 400.

[0065] Since lighting assembly 100 is capable of emitting light from the entirety of the surface area of the front major surface 130 of light guide 120, lighting assembly 100 can be used to make a lighting fixture 400 having a narrow bezel, e.g., a bezel less than 8 mm wide, or even a zero-width bezel. In the example of lighting fixture 400 shown in Figure 12, lighting assembly 100 is mounted in a narrow tray 420 that extends around the perimeter of and behind the lighting assembly. Tray 420 is thermally coupled to the solid-state light emitters 110 (Figure 1A) of lighting assembly 100 to dissipate heat generated by the solid-state light emitters. Tray 420 is additionally used to mechanically couple lighting assembly to supports 430 that in turn directly or indirectly couple lighting assembly 400 to an architectural surface and a source of electric power. In other examples, tray 420 is located exclusively behind lighting assembly 100 to give lighting fixture 400 a substantially zero-width bezel. In one embodiment, the tray 420 or the reflective insert conforms to the back major surfaces 134, 142,

[0066] In the above-described examples of lighting assemblies 100 and 200, light guide 120, 220 has a flat, planar front major surface 130, 230. In other embodiments (not shown), especially in embodiments used in lighting fixtures, light guide 120, 220 is curved about an axis parallel to a line that extends orthogonally to distal edge 134 or first edge 234. In some embodiments (not shown), light guide 120, 220 forms a cylinder about the above-mentioned axis. Some curvature of light guide 120, 220 about an axis orthogonal to the above-mentioned axis is also possible.

[0067] Light guide portions 122, 124 and light guide 220 are each a solid article made from an optically-transmissive material such as acrylic, polycarbonate, poly(methyl-methacrylate) (PMMA), glass, or another appropriate material. Light guide portions 122, 124 and light guide 220 may also have a multi-layer structure with two or more layers (not shown) that may differ in refractive index.

[0068] Each light extracting element 180 functions to disrupt the total internal reflection of propagating along light guide portion 122, light guide portion 124 or light guide 220 and that is incident on the light extracting element. In one embodiment, the light extracting elements at one major surface reflect light toward the opposite major surface so that the light exits the light guide portion or the light guide through the opposite major surface. Alternatively, the light extracting elements transmit light through the light extracting elements and out of the major surface of the light guide portion or the light guide at which the light extracting elements are located. In another embodiment, both types of light extracting elements are present. In yet another embodiment, the light extracting elements reflect some of the light and refract the remainder of the light incident thereon.

[0069] Light guide portions and light guides having such light extracting elements are typically formed by a process such as stamping, molding, embossing, extruding, laser etching, chemical etching, or another suitable process. Light extracting elements may also be produced by depositing elements of curable material on the major surface of the light guide portion or light guide and curing the deposited material using heat, UV-light or other radiation. The curable material can be deposited by a process such as printing, ink jet printing, screen printing, or another suitable process.

[0070] Exemplary light extracting elements include light-scattering elements, which are

typically features of indistinct shape or surface texture, such as printed features, ink-jet printed features, selectively-deposited features, chemically etched features, laser etched features, and so forth. Other exemplary light extracting elements include features of well-defined shape, such as V-grooves, lenticular grooves, and features of well-defined shape that are small relative to the linear dimensions of the major surfaces of the light guide portions or the light guide, which are referred to herein as micro-optical elements. The smaller of the length and width of a micro-optical element is less than one-tenth of the longer of the length and width (or circumference) of the major surface and the larger of the length and width of the micro-optical element is less than one-half of the smaller of the length and width (or circumference) of the major surface. The length and width of the micro-optical element is measured in a plane parallel to the major surface for planar light guides or along a surface contour for non-planar light guides.

[0071] Light extracting elements 180 are configured to extract light with a defined intensity profile, and/or a defined light ray angle distribution over the entire area of front major surfaces 130, 230. An example of a defined intensity profile is a uniform intensity profile.

[0072] Micro-optical elements are shaped to predictably reflect or refract light. However, one or more of the surfaces of the micro-optical elements may be modified, such as roughened, to produce a secondary effect on light output. Exemplary micro-optical elements are described in U.S. Patent No. 6,752,505 and, for the sake of brevity, are not described in detail in this disclosure. In the disclosure set forth above, the major surfaces of the light guide are referred to as the front major surface and the back major surface to distinguish the major surfaces from one another. These appellations are not intended to impose particular orientation on the lighting assemblies. In some applications, the front major surface of a lighting assembly may face rearward, upward, downward or another direction. Regardless of the orientation of the front major surface, the back major surface is always opposite the front major surface.

Claims

Claims We claim:

1. A lighting assembly, comprising:

a light guide comprising a first light guide portion and a second light guide portion, each light guide portion comprising a front major surface and a back major surface offset from one another in a thickness direction, a distal edge extending between the major surfaces, and castellated proximal edge opposite the distal edge, in which:

the proximal edge of each light guide portion comprises first proximal edge segments alternating with second proximal edge segments, the second proximal edge segments offset from the first proximal edge segments towards the distal edge,

the light guide portions are arranged with the first proximal edge segments of each light guide portion abutting the second proximal edge segments of the other light guide portion;

each light guide portion is tapered in thickness such that, at each first proximal edge segment thereof, the light guide portion is thicker than the other light guide portion to define a respective light input edge segment; and

the lighting assembly additionally comprises:

a respective solid-state light emitter located adjacent each light input edge segment to input light to the light guide portions, light from the solid-state light emitters propagating along the light guide portions by total internal reflection at the major surfaces thereof; and light extracting elements at at least one of the major surfaces of each light guide portion to extract light from the light guide portion through the front major surface thereof.

2. The lighting assembly of claim 1, in which:

the light input edge segments of the first light guide portion are first light input edge segments;

the light input edge segments of the second light guide portion are second light input edge segments;

the solid-state light emitters adjacent the first light input edge segments are first solid-state light emitters; and

the solid-state light emitters adjacent the second light input edge segments are second solid- state light emitters.

3. The lighting assembly of claim 2, in which at least one of the first light input edge segments and the first solid-state light emitter adjacent thereto are configured to direct a portion of the light from the first solid-state light emitter towards a region of the first light guide portion in front of at least one of the second solid-state light emitters.

4. The lighting assembly of claim 3, in which the least one of the first light input edge segments comprises a lens array.

5. The lighting assembly of claim 3, in which the at least one of the second solid-state light emitters is adjacent the first solid-state light emitter.

6. The lighting assembly of claim 3, in which some of the light extracting elements of the first light guide portion are in front of the second solid-state light emitters.

7. The lighting assembly of claim 3, in which at least one of the second light input edge segments and the second solid-state light emitter adjacent thereto are configured to direct a portion of the light from the second solid-state light emitter towards a region of the second light guide portion in front of at least one of the first solid-state light emitters.

8. The lighting assembly of claim 7, in which the at least one of the first solid-state light emitters is adjacent the second solid-state light emitter.

9. The lighting assembly of claim 7, in which some of the light extracting elements of the second light guide portion are in front of the first solid-state light emitters.

10. The lighting assembly of claim 1, in which the solid-state light emitters that input light to each light guide portion are located behind the back major surface of the other light guide portion.

11. The lighting assembly of claim 10, in which the light extracting elements are at the back major surface of each light guide portion.

12. The lighting assembly of claim 10, additionally comprising respective light attenuating elements between the solid-state light emitters adjacent the light input edge segments of each light guide portion and the back major surface of the other light guide portion.

13. The lighting assembly of claim 12, in which the light attenuating elements are reflective and/or opaque.

14. The lighting assembly of claim 1, in which the castellated proximal edge additionally comprises a respective third proximal edge segment extending between an end of each first proximal edge segment and an adjacent end of a respective second proximal edge segment.

15. The lighting assembly of claim 14, in which the third proximal edge segment extends non-orthogonally to the first proximal edge segment and the second proximal edge segment.

16. The lighting assembly of claim 14, in which the third proximal edge segment is oriented to totally internally reflect light input through the adjacent light input edge segment.

17. The lighting assembly of claim 14, in which the third proximal edge segment comprises a reflective coating.

18. The lighting assembly of claim 1, in which the light guide is monolithic.

19. The lighting assembly of claim 1, in which the first light guide portion and the second light guide portion are separate components optically bonded to one another at their castellated proximal edges.

20. The lighting assembly of claim 19, in which the front major surfaces of the light guide portions are planar and co-planar with each other.

21. The lighting assembly of claim 1, in which the first light guide portion and the second light guide portion are separate components arranged with their castellated proximal edges adjacent.

22. The lighting assembly of claim 21, in which the first light guide portion and the second light guide portion are optically isolated from one another.

23. The lighting assembly of claim 22, in which the first solid-state light emitters are operable independently of the second solid-state light emitters.

24. The lighting assembly of claim 1, in which the first proximal edge segments of at least one of the light guide portions extend nominally parallel to the distal edge thereof.

25. The lighting assembly of claim 1, in which each light guide portion tapers in thickness between the castellated proximal edge thereof and the distal edge thereof.

26. The lighting assembly of claim 1, in which each light guide portion tapers in thickness between the first proximal edge segments and the second proximal edge segments of the castellated proximal edge.

27. The lighting assembly of claim 1, in which the light guide is rectangular in shape.

28. The lighting assembly of claim 1, additionally comprising a printed circuit board on which the solid-state light emitters are mounted.

29. The lighting assembly of claim 1, additionally comprising a tray thermally coupled to the solid-state light emitters.

30. The lighting assembly of claim 1, in which the solid-state light emitters comprise light emitting diodes (LEDs).

31. A display, comprising:

a display panel; and

a lighting assembly in accordance with claim 1 arranged to back light the display panel.

32. The display of claim 31, in which the display panel comprises a liquid crystal display panel.

33. The display of claim 31, in which the display panel is a narrow-bezel display panel..

34. The display of claim 31, in which the lighting assembly is one of an array of lighting assemblies arranged to back light the display panel.

35. The display of claim 34, in which the lighting assemblies are optically isolated from one another.

36. The display of claim 34, in which:

the display panel comprises an array of light valves; and

each of the lighting assemblies back lights a corresponding group of the light valves of the display panel, and each lighting assembly has a light output independently controlled for local dimming of the display according to brightness values in a video signal applied to the display for the corresponding group of light valves and the light output updated for each frame of the video signal.

37. A lighting fixture, comprising a lighting assembly in accordance with claim 1.

38. A lighting assembly, comprising:

solid-state light emitters; and

a light guide, comprising:

a front major surface and a back major surface offset from one another in a thickness direction,

a first edge extending between the major surfaces, and second edge opposite the first edge, and

first light input structures alternating with second light input structures arrayed nominally parallel to the first edge, the light input structures protruding from the back major surface part-way between the first edge and the second edge, in which:

each of the first light input structures comprises a respective first light input edge segment closer to the second edge than the first edge, and tapers in thickness from the first light input edge segment towards the first edge;

each of the second light input structures comprises a respective second light input edge segment closer to the first edge than the second edge, and tapers in thickness from the second light input edge segment towards the second edge;

each of the solid-state light emitters is located adjacent a respective light input edge segment to input light to the light guide, light from the solid-state light emitters propagating along the light guide by total internal reflection at the major surfaces thereof; and

the light guide additionally comprises light extracting elements at at least one of the major surfaces thereof to extract light from the light guide through the front major surface thereof.

39. The lighting assembly of claim 38, in which the light guide is monolithic.