Patent Description:
Light emitting panel assemblies use light guides to transmit light from point light sources such as light emitting diodes (LEDs) to extraction elements where the light is extracted. Luminaires are an example of light emitting panel assemblies.

One objective in lighting is to provide even illuminance on a work plane, which can be achieved by providing a lighting distribution known in the art as a "batwing" distribution. Another objective in lighting is to eliminate or reduce glare. Glare is an effect of luminance at high vertical angles that can cause visual discomfort to users.

Luminance of a light emitting panel assembly is determined by dividing luminous intensity by projected area at a particular angle.

Conventional light emitting panel assemblies are horizontally oriented, i.e., the light emitting panel assembly is wider than it is tall. This configuration allows light to leave towards the work plane from traditional sources such as fluorescent and incandescent light sources. A challenge with this configuration is that projected area shrinks as the angle increases so increasing luminous intensity in order to provide even illuminance would create unacceptable levels of high vertical angle luminance, i.e., glare. Baffling is one measure that may be used to mitigate glare in horizontally-oriented light emitting panel assemblies. <CIT> discloses a light guide including: a first major surface; a second major surface opposite the first major surface; an array of extraction elements, each element disposed between an upper and lower edge of the first major surface, each upper and lower edge defining a plane therebetween, each element including: a first face adjoining the upper edge, the first face projecting inwardly relative to the plane at a first angle; a second face adjoining the first face, the second face projecting inwardly at a second angle relative to the plane, the second angle greater than the first angle; a third face adjoining the lower edge and the second face, the third face projecting inwardly relative to the plane at a third angle, the third angle greater than the first angle; wherein the first face, a second face and third face define an indentation projecting inwardly from the plane defined by the first major surface.

Vertically oriented light emitting panel assemblies are advantageous because projected area is smaller at low vertical angles where less luminous intensity is required and projected area increases as the vertical angle increases, as illustrated for example in <FIG> and <FIG>. This configuration allows luminous intensity to be higher at higher vertical angles compared to that of a horizontally oriented light emitting panel assembly, avoiding the problem of glare which would otherwise require resorting to additional measures such as baffling. A challenge with this configuration is that the small projected area at low vertical angles results in high luminance at these angles, as illustrated for example in <FIG>. While light emitting panel assemblies are typically installed above users and not in their direct field of view, too much luminance at low vertical angles can still cause visual discomfort in their peripheral field of view. Minimizing luminous intensity at lower vertical angles is thus desirable for vertically oriented light emitting panel assemblies.

A further objective in lighting is to emit visually homogenous light. Light travels through the light guide by way of total internal reflection until it is extracted. In conventional light guides light is internally reflected through the guide in an uninterrupted linear path in the plane perpendicular to the normal of the flat sides of the light guide. In conventional light guides, when the light is extracted by extraction elements the light can appear to the viewer as undesirable visible lines of light emanating from the light sources. The visual definition of these lines, or "head lamping", can vary depending on the type of extraction elements used, the distance between the extraction elements and the light source(s), and the width or thickness of the light guide. Reducing or eliminating these visible lines of light, and emitting light which is more visually homogenous across the emitting surface, are desirable.

The invention provides a light emitting panel assembly according to independent claim <NUM>. Further embodiments are provided by the dependent claims.

The foregoing discussion merely summarizes certain aspects of the disclosure.

In drawings which show aspects of the disclosure:.

Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the disclosure. However, the disclosure may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

The term "adjacent" as used in this specification refers to being near or adjoining. Adjacent features can be spaced apart from one another or can be in direct contact with one another. In some instances, adjacent features can be connected to one another or can be formed integrally with one another.

The term "inwardly" as used in this specification refers to a direction toward the cross-sectional center of the light guide.

The term "outwardly" as used in this specification refers to a direction away from the cross-sectional center of the light guide.

The terms "upper", "upward", and like terms as used in this specification refers to a direction away from where the light source is located.

The terms "lower", "downward", and like terms as used in this specification refer to a direction toward where the light source is located.

The term "low angle" as used in this specification refers to an angle of approximately <NUM> to <NUM> degrees from the vertical.

The term "peak angle" as used in this specification refers to an angle of approximately <NUM> to <NUM> degrees from the vertical.

<FIG> shows a light emitting panel assembly <NUM> according to an aspect of the disclosure. Light emitting panel assembly <NUM> has a housing <NUM>. Light guides <NUM> are vertically disposed on both sides of housing <NUM>. Light guides <NUM> partially define a cavity <NUM> between them. Light emitting panel assembly <NUM> also includes light sources <NUM>, upper guide reflectors <NUM>, side guide reflectors <NUM>, and upper reflector <NUM>.

Light source <NUM> is a light emitting diode (LED) or an array of LEDs. In some aspect light source <NUM> may be any other point source emitter of light, including laser diodes and the like. Light source <NUM> is adjacent to a lower surface <NUM> of light guide <NUM>. In some aspects light source <NUM> squarely faces lower surface <NUM>. In some aspects light source <NUM> may be in contact with lower surface <NUM>. In some aspects light source <NUM> may be spaced apart from lower surface <NUM>. For example, spacer elements disposed between individual LEDs may be used to space light source <NUM> apart from lower surface <NUM>. The space or lack thereof between light source <NUM> and lower surface <NUM> determines the quantity of light entering light guide <NUM> in the upward direction and conversely the amount of light illuminating upper reflector <NUM> directly. In some aspects lower surface <NUM> of light guide <NUM> may have a diffuse surface to homogenize light entering light guide <NUM>.

Light guide <NUM> is generally planar, and has a first major surface <NUM> facing away from cavity <NUM> and a second major surface <NUM> facing toward cavity <NUM>.

Light guide <NUM> decreases in width in the downward direction. In the aspect shown, the decrease in width is due to the shape of extraction elements <NUM> on first major surface <NUM>; for example, and with reference to <FIG>, the decreasing width may be achieved by lower face <NUM> being shorter than upper face <NUM> and/or by angle AL being less than angle AU. The individual sections between extraction elements <NUM> along first major surface <NUM> are parallel to second major surface <NUM>. The downward decrease in width of light guide <NUM> results in a greater capacity for light extraction from a lower region of light guide <NUM> (see <FIG>), and lesser capacity for light extraction from an upper region of light guide <NUM> (see <FIG> and <FIG>). This balances out the greater amount of light available for extraction at the upper region of light guide <NUM> (after reflecting off upper guide reflector <NUM>), resulting in a more even extraction of light from the top to the bottom of light guide <NUM>. This even extraction of light contributes to the desirable peaks of the angle batwing distribution shown in <FIG> and <FIG>.

In some aspects light guide <NUM> may not decrease in width in the downward direction, that is, first major surface <NUM> and second major surface <NUM> may extend parallel to one another.

Light guide <NUM> also has a lower lip <NUM> extending toward cavity <NUM>. In some aspects, lower lip <NUM> may be absent. In some aspects the lip may be a separate part. In some aspects the lip may have a diffuse upper and/or lower surface to homogenize light travelling upward through the lip and illuminating upper reflector <NUM>.

Upper guide reflector <NUM> is adjacent to upper surface of light guide <NUM>. Upper guide reflector <NUM> has a diffuse reflective surface facing upper surface. In some aspects the upper guide reflector <NUM> may be partially specular. For example, upper guide reflector <NUM> may be a highly reflective white film. Diffuse reflection homogenizes the light from light guide <NUM>. In some aspects, upper guide reflector <NUM> is pressed against upper surface. In some aspects upper guide reflector <NUM> is integrated with upper surface, for example by lamination or coating. In some aspects, upper guide reflector <NUM> may be co-extruded with light guide <NUM>. Integration of upper guide reflector <NUM> with upper surface of light guide <NUM> reduces boundary losses of light by avoiding having the light exit and re-enter light guide <NUM>.

In some aspects, upper guide reflector <NUM> may be textured to reflect more light back into light guide <NUM> at a lower angle from the vertical, to facilitate even emission of light down the vertical extent of light guide <NUM>. For example, upper guide reflector <NUM> may be linearly diffuse such that a cross sectional plane of upper guide reflector <NUM> parallel to first major surface <NUM> and second major surface <NUM> is ridged or rippled.

Side guide reflector <NUM> extends parallel and adjacent to first major surface <NUM>. In some aspects, the distance DS between side guide reflector <NUM> and first major surface <NUM> is minimized, that is, less than <NUM>, or <NUM>, or <NUM>. Side guide reflector <NUM> may be specular, semi-specular or white. In some aspects side guide reflector <NUM> may be pressed against or laminated to first major surface <NUM> such that the only space between them would be at the extraction elements.

Side guide reflector <NUM> angles inwardly as it extends downward, in parallel to the decreasing width of first major surface <NUM> in the downward direction. In aspects wherein first major surface <NUM> does not decrease in width in the downward direction, side guide reflector <NUM> may angle inwardly as it extends downward, or go straight downward. The inward angling of side reflector <NUM> is to compensate for light refracting out extraction elements <NUM> on first major surface <NUM>, as shown for example in <FIG>, at a lower angle than light internally reflecting off extraction elements <NUM>, as shown for example in <FIG>. In some aspects the angle of side guide reflector <NUM> may be <NUM> to <NUM> degrees from the vertical.

Upper reflector <NUM> spans between upper sections of opposing light guides <NUM>. Upper reflector <NUM> has a fully diffuse surface. Upper reflector <NUM> may be specular, semi-specular or white. Upper reflector <NUM> defines an upper boundary of cavity <NUM>. In some aspects, for example wherein light emitting panel assembly <NUM> is very narrow, upper reflector <NUM> may be absent.

As best shown in <FIG>, first major surface <NUM> has a plurality of extraction elements <NUM> and second major surface <NUM> has no extraction elements. In some aspects second major surface <NUM> may have extraction elements. Extraction elements <NUM> are shaped to extract both light travelling upward and light travelling downward within light guide <NUM>. Each extraction element <NUM> has an upper face <NUM> and lower face <NUM> that together define an inwardly extending depression in first major face <NUM>. In some aspects, relative to plane PF parallel to first major face <NUM>, upper face <NUM> angles inwardly at an angle AU of <NUM> to <NUM> degrees, or <NUM> to <NUM> degrees, or about <NUM> degrees, and lower face <NUM> angles inwardly at an angle AL of <NUM> to <NUM> degrees, or <NUM> to <NUM> degrees, or about <NUM> degrees. In some aspects, upper face <NUM> and lower face <NUM> may be symmetrical, that is, their dimensions may be identical and angles AU and AL may be identical.

In some aspects, upper face <NUM> and lower face <NUM> may not be symmetrical. For example, as mentioned above, lower face <NUM> is shorter than upper face <NUM> and/or AL is less than AU to facilitate even extraction of light along light guide <NUM>. As another example, angles AU and AL may different in order to ensure an even distribution of light across upper reflector <NUM>.

Extraction element <NUM> has a height HE. In some aspects, height HE is negatively correlated to a height HL of light guide <NUM>; that is, the taller the light guide, the smaller the extraction elements since they would need to release less light, and vice versa.

In some aspects height HE of extraction elements <NUM> increases in the downward direction along light guide <NUM>. In some aspects the distance DE between extraction elements <NUM> decreases in the downward direction along light guide <NUM> to increase the density of extraction elements <NUM> in a lower region of light guide <NUM>. The foregoing features, individually and in combination, provide greater light extraction capacity at a lower region of light guide <NUM> compared to an upper region of light guide <NUM>, resulting in more even extraction of light from the top to the bottom of light guide <NUM> and thus contributing to the desirable peak angle batwing distribution shown in <FIG> and <FIG>.

In some aspects, extraction element <NUM> may have a shape different than that illustrated in <FIG>, but still extract light travelling upward and downward in light guide <NUM>. <FIG> are examples of other possible shapes of extraction element <NUM>.

<FIG>, <FIG>, <FIG> illustrate exemplary paths of rays of light emitted from light source <NUM> of light emitting panel assembly <NUM>.

<FIG> illustrate rays of light which internally reflect off an extraction element <NUM> of first major surface <NUM> in a lower region of light guide <NUM>, refract out of second major surface <NUM> into cavity <NUM> toward upper reflector <NUM>, and reflect off upper reflector <NUM> into cavity <NUM> to a workspace.

<FIG> illustrate rays of light which refract out of an extraction element <NUM> of first major surface <NUM> in a lower region of light guide <NUM>, reflect off of side guide reflector <NUM>, refract through first major surface <NUM> and second major surface <NUM> into cavity <NUM> toward upper reflector <NUM>, and reflect off upper reflector <NUM> into cavity <NUM> to a workspace.

<FIG> illustrate rays of light which refract through lower lip <NUM> into cavity <NUM> toward upper reflector <NUM>, and reflect off upper reflector <NUM> into cavity <NUM> to a workspace.

Light rays such as those generally following the paths illustrated in <FIG>, <FIG> combine to illuminate upper reflector <NUM> to create a homogenous luminance surface. Light leaving this surface provides the low angle light distribution of the light distribution shown in <FIG>. <FIG> shows a light distribution of light emitting panel assembly <NUM> without upper reflector <NUM>, that is, without the contribution of light rays generally following the paths illustrated in <FIG>, <FIG>.

<FIG> illustrate rays of light which internally reflect up to the top of light guide <NUM>, reflect off upper guide reflector <NUM>, internally reflect down light guide <NUM>, internally reflect off extraction element <NUM> in an upper region of light guide <NUM>, and refract out of second major surface <NUM> into cavity <NUM> to a workspace.

<FIG> illustrate rays of light which internally reflect up to the top of light guide <NUM>, reflect off upper guide reflector <NUM>, internally reflect down light guide <NUM>, refract out of an extraction element <NUM> in a upper region of light guide <NUM>, reflect off of side guide reflector <NUM>, and then refract through first major surface <NUM> and second major surface <NUM> into cavity <NUM> to a workspace.

Light rays such as those generally following the paths illustrated in <FIG>, <FIG> advantageously mix and spread with light rays from adjacent LEDs from the LED array as they travel from light source <NUM> to upper guide reflector <NUM>. Light reflecting off upper guide reflector <NUM> is homogenized, eliminating "head lamping" effects, and reenters light guide <NUM>. These light rays contribute to the desirable peak angle batwing distribution shown in <FIG> and <FIG>.

<FIG> shows exemplary simulated light ray traces of light emitting panel assembly <NUM> without upper reflector <NUM>. <FIG> show exemplary simulated light ray traces of light emitting panel assembly <NUM> of two ray reactions, four ray reactions, and one hundred ray reactions respectively according to example aspects. The two ray reaction shown in <FIG> isolates the simulation to rays primarily such as those rays shown in <FIG>, <FIG>, that is, light refracting out of a lower region or lower lip <NUM> of light guide <NUM> upward toward upper reflector <NUM> to illuminate upper reflector <NUM>. The four ray reaction shown in <FIG> is similar to the two ray reaction of <FIG> but also begins to show some reflections off upper reflector <NUM>. The one hundred ray reaction shown in <FIG> demonstrates full optical reactions to light emitting panel assembly <NUM>, and the optical distribution of these reactions is plotted in <FIG>.

Thus in light emitting panel assembly <NUM>, light from light source <NUM> traveling through light guide <NUM> toward upper guide reflector <NUM> spreads within light guide <NUM>, and upper guide reflector <NUM> homogenizes the light before the light is redirected to light guide <NUM> to be extracted by extraction elements <NUM> at angles visible in the lower hemisphere. In addition to allowing for improved optical distributions, the foregoing features of the present disclosure allow for larger spacing between individual lights within light source <NUM> (e.g. spacing between LEDs), resulting in cost savings with respect to light source <NUM>.

<FIG> shows a light emitting panel assembly <NUM> according to an aspect. Light emitting panel assembly <NUM> has a housing <NUM> defining a cavity <NUM>. A pair of light guides <NUM> is vertically disposed on the sides of housing <NUM>. Light emitting panel assembly <NUM> also includes light sources <NUM>, upper guide reflectors <NUM>, side guide reflectors <NUM>, and upper reflector <NUM>. Compared to light emitting panel assembly <NUM>, light emitting panel assembly <NUM> has a significantly wider upper reflector <NUM> and other differences to facilitate even distribution of light across the wider upper reflector <NUM>. In some aspects, width WU of upper reflector <NUM> is at least twice the height HL of light guides <NUM>.

Light guide <NUM> and light source <NUM> are substantially similar to light guide <NUM> and light source <NUM> of light emitting panel assembly <NUM> except that lower surface <NUM> of light guide <NUM> and light source <NUM> are spaced apart to define a gap <NUM>. Gap <NUM> is shaped to allow a predetermined amount of light from light source <NUM> to first reflect off side guide reflector <NUM> before hitting light guide <NUM>. In some aspects, a first edge <NUM> of light source <NUM>, defined as the edge of light source <NUM> further from side guide reflector <NUM>, is closer to lower surface <NUM> of light guide <NUM> than an opposite second edge <NUM> of light source <NUM>. In some aspects, first edge <NUM> is adjacent to, and may abut, lower surface <NUM>. In the aspect shown, light source <NUM> is angled in the direction of side guide reflector <NUM> to define a triangular gap <NUM> between light source <NUM> and lower surface <NUM>. In some aspects, an angle AL between a major plane PL of light source <NUM> and a horizontal plane PH ranges from or <NUM> to <NUM> degrees, or <NUM> to <NUM> degrees, or <NUM> to <NUM> degrees. In some aspects, light source <NUM> is horizontal (i.e., major plane PL of light source <NUM> lies in horizontal plane PH) but lower surface <NUM> is angled to define a triangular gap <NUM>. In some aspects, both light source <NUM> and lower surface <NUM> are angled to define a triangular gap <NUM>.

Side guide reflector <NUM> angles away from light guide <NUM> in the downward direction. In some aspects the angle of side guide reflector <NUM> may be <NUM> to <NUM> degrees from the vertical. Similar to side guide reflector <NUM>, the angling of side reflector <NUM> is to compensate for light refracting out extraction elements <NUM> on first major surface <NUM>, as shown for example in <FIG>, at a lower angle than light which internally reflects off extraction elements <NUM>, as shown for example in <FIG>.

Side guide reflector <NUM> includes a lower extension <NUM>. In some aspects lower extension <NUM> extends horizontally in the direction of light source <NUM>. In some aspects lower extension <NUM> spans at least half of a gap <NUM> defined between a bottom region of side guide reflector <NUM> and a bottom region of light source <NUM>. In some aspects lower extension <NUM> may be formed as a separate reflector from the rest of side guide reflector <NUM>. Gap <NUM> provides distance between light source <NUM> and side guide reflector <NUM> to perform at least two functions: (i) increases optical control over the distribution of light for illuminating upper reflector <NUM>; and (ii) reduces the amount of light reflected back at light source <NUM> and thereby wasted.

As shown in <FIG>, first major surface <NUM> has a plurality of extraction elements <NUM>. In some aspects, second major surface <NUM> has no extraction elements. Extraction elements <NUM> are configured to only extract light travelling downward in light guide <NUM>; this advantageously preserves light for peak angle distribution as described in relation to <FIG> below. Each extraction element <NUM> comprises an angled step <NUM> that widens light guide <NUM> in the upward direction. In some aspects, relative to plane PF parallel to first major face <NUM>, angled step <NUM> angles outwardly at an angle AA of <NUM> to <NUM> degrees, or <NUM> to <NUM> degrees, or about <NUM> degrees.

Other aspects of extraction elements <NUM> such as their dimensions and distribution are similar to extraction elements <NUM> previously discussed. For example, height Hs of extraction elements <NUM> increases in the downward direction along light guide <NUM>. In some aspects the distance DS between extraction elements <NUM> decreases in the downward direction along light guide <NUM> to increase the density of extraction elements <NUM> in a lower region of light guide <NUM>. In some aspects angle AA of extraction elements <NUM> increases in the downward direction along light guide <NUM>. The foregoing features, individually and in combination, provide for greater light extraction capacity at a lower region of light guide <NUM> compared to an upper region of light guide <NUM>, resulting in more even extraction of light from the top to the bottom of light guide <NUM> and thus contributing to the desirable peak angle batwing distribution shown in <FIG>.

<FIG>, <FIG> illustrate exemplary paths of rays of light emitted from light source <NUM> of light emitting panel assembly <NUM>.

<FIG> illustrate rays of light which internally reflect up to the top of light guide <NUM>, reflect off upper guide reflector <NUM>, internally reflect down light guide <NUM>, internally reflect off extraction element <NUM>, and refract out of second major surface <NUM> into cavity <NUM> to a workspace.

<FIG> illustrate rays of light which internally reflect up to the top of light guide <NUM>, reflect off upper guide reflector <NUM>, internally reflect down light guide <NUM>, refract out of an extraction element <NUM>, reflect off of side guide reflector <NUM>, and then refract through first major surface <NUM> and second major surface <NUM> into cavity <NUM> to a workspace.

Light rays such as those generally following the paths illustrated in <FIG> advantageously mix and spread with light rays from adjacent LEDs from the same LED array as they travel from light source <NUM> to upper guide reflector <NUM>. Light reflecting off upper guide reflector <NUM> is homogenized, eliminating "head lamping" effects, and reenters light guide <NUM>. These light rays contribute to the desirable peak angle batwing distribution shown in <FIG>.

<FIG> illustrate rays of light which leave light source <NUM> at angles at or near the horizontal such that they travel through gap <NUM> and gap <NUM> and are reflected by side guide reflector <NUM> (or lower extension <NUM> and side guide reflector <NUM>) before refracting through first major surface <NUM> and second major surface <NUM> at a lower region of light guide <NUM> at an upward angle through cavity <NUM> to upper reflector <NUM>. Side guide reflector <NUM> may include a bottom face <NUM> that is angled slightly upward to reflect light through a lower region of light guide <NUM> toward upper reflector <NUM> to facilitate even spreading of light on upper reflector <NUM>. The light rays exemplified by <FIG> create a homogenous luminance surface on upper reflector <NUM>, and the light leaving this surface provides the low angle light distribution of the light distribution shown in <FIG>.

<FIG> shows exemplary simulated light ray traces of ray reactions of light emitting panel assembly <NUM>. <FIG> shows exemplary simulated light ray traces of ray reactions at a lower section of one side of light emitting panel assembly <NUM>. <FIG> is an optical distribution plot of light emitted from light emitting panel assembly <NUM> except with the top portion of the housing <NUM> and upper reflector <NUM> removed.

<FIG> shows a light emitting panel assembly <NUM> according to an aspect, not forming part of the claimed invention. Light emitting panel assembly <NUM> includes a centrally positioned light guide <NUM> having a first major surface <NUM> and second major surface <NUM>. Each of first major surface <NUM> and second major surface <NUM> have extraction elements (not shown) similar in features and functions to extraction elements <NUM> of light emitting panel assembly <NUM>. For example, the extraction elements are configured to only extract light travelling downward in light guide <NUM>, advantageously preserving light for peak angle distribution. Because both major surface <NUM> and second major surface <NUM> have extraction elements, downward travelling light is extracted out of both sides of light guide <NUM>. Light emitting panel assembly <NUM> also includes a light source <NUM>, upper guide reflector <NUM>, a pair of convex reflectors <NUM> a pair of lips <NUM>, and a lower surface <NUM>, each of which are similar in feature and function to corresponding features of light emitting panel assemblies <NUM> and <NUM>, except in the case of reflector <NUM> which is convex rather than flat.

<FIG> shows exemplary simulated light ray traces of ray reactions of light emitting panel assembly <NUM>. <FIG> shows exemplary simulated light ray traces of ray reactions of the entire light emitting panel assembly <NUM>. <FIG> shows a close up of exemplary simulated light ray traces of ray reactions of the light emitting panel assembly <NUM>.

This disclosure is intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this disclosure is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains.

As an example of a variation, <FIG> show the lower section of light emitting panel assembly <NUM>', a variation of light emitting panel assembly <NUM>. Assembly <NUM>' has two light guides <NUM>', each with an array of light sources <NUM>' facing respective lower surfaces <NUM>', spacer elements <NUM>' between individual light sources <NUM>' to space light sources <NUM>' from lower surface <NUM>', and a lip element <NUM>' on each side being a distinct component from light guide <NUM>'. The upper surface and/or lower surface of each lip element <NUM>' may be diffuse for homogenizing light from light source <NUM>' that illuminates the convex reflectors <NUM>' above (not shown). In the aspect shown, lip elements <NUM>' are injection molded lenses with a textured, i.e., diffuse, lower surface. <FIG> shows an isolated view of a lip element <NUM>' with spacer elements <NUM>'.

As another example of variations, while the light sources, light guides and upper guide reflectors in the aspects of the light emitting panel assemblies described above are generally aligned vertically, in some aspects these features may be aligned along an angle other than the vertical for example as shown in <FIG>.

<FIG> shows a light emitting panel assembly <NUM> according to an aspect, not forming part of the claimed invention. Light emitting panel assembly <NUM> has a housing <NUM> defining an interior cavity <NUM>. A pair of light guides <NUM> is disposed on the sides of housing <NUM>. Light emitting panel assembly <NUM> also includes light sources <NUM>, upper guide reflectors <NUM>, side guide reflectors <NUM>, and upper reflector <NUM>.

In contrast to the light guides of assemblies <NUM>, <NUM> and <NUM>, light guides <NUM> in assembly <NUM> are angled off from the vertical. In the aspect shown in <FIG>, light guides <NUM> are angled approximately <NUM> degrees off from the vertical. In some aspects, light guides <NUM> may be angled off from the vertical by up to <NUM> degrees, <NUM> degrees, <NUM> degrees, or <NUM> degrees (i.e., horizontal).

First major surfaces <NUM> of light guides <NUM> comprise extraction elements <NUM>. In some aspects, extraction elements <NUM> are similar in structure and function to extraction elements <NUM> of assembly <NUM>, and therefore only extract light travelling downward in light guide <NUM>, i.e., after being reflected by upper guide reflector <NUM>.

In some aspects, extraction elements <NUM> are similar in structure and function to extraction elements <NUM> of assembly <NUM>, and therefore extract light travelling upward and downward in light guide <NUM>. Extraction elements <NUM> are configured such that light extracted while travelling upward in light guide <NUM> is limited to light leaving at an angle high enough to strike the opposing arm <NUM>, <NUM>' and thereby stay within the confines of interior <NUM>. Preventing light travelling upward in the light guide from leaving at a low enough angle to escape interior <NUM> eliminates the possibility of un-homogenized light (which causes headlamping) from being visible from below assembly <NUM>.

Assembly <NUM> also has a secondary optic <NUM> adjacent each second major surface <NUM> of light guides <NUM>. Secondary optic <NUM> may, for example, bend light toward the normal, or away from the normal, as required by the application. In some aspects, secondary optic <NUM> may be a transflective optic. In some aspects, secondary optic <NUM> may be absent.

As a further example of variations, while assemblies such as assemblies <NUM>, <NUM> and <NUM> are two-sided and define a cavity therebetween, other configurations are possible. For example, some aspects may be three-sided (triangular from a top plan view), four-sided (square or rectangular from a top plan view), multi-sided (polygonal from a top plan view), round (circular from a top plan view), oval (oval from a top plan view) and the like, each defining a centrally-located cavity.

Claim 1:
A light emitting panel assembly (<NUM>, <NUM>) comprising:
a housing (<NUM>, <NUM>);
a generally planar light guide (<NUM>, <NUM>) and an opposing generally planar light guide (<NUM>, <NUM>) within the housing, the opposing light guide positioned in lateral opposition to the light guide, the light guide and the opposing light guide defining lateral boundaries of a cavity (<NUM>, <NUM>) therebetween, the light guide and the opposing light guide each comprising:
a first major surface (<NUM>) comprising a plurality of extraction elements (<NUM>, <NUM>),
a second major surface (<NUM>),
a lower end surface (<NUM>, <NUM>),
an upper end surface,
a light source (<NUM>) and an opposing light source (<NUM>) adjacent to the corresponding one of the lower end surfaces of the light guides and adjacent to lowermost portions of the housing;
an upper guide reflector (<NUM>, <NUM>) and an opposing upper guide reflector (<NUM>) each comprising a diffuse reflective surface adjacent to and facing the corresponding one of the upper end surfaces of the light guides; and,
an upper reflector (<NUM>, <NUM>) defining an upper boundary of the cavity,
wherein light from the light source and the opposing light source travelling through the light guide and the opposing light guide toward the respective upper guide reflector and opposing upper guide reflector spreads within the light guide and the opposing light guide, and whereby the upper guide reflector and the opposing upper guide reflector homogenize the light before the light is redirected to the light guide and the opposing light guide.