WO2015074154A1

WO2015074154A1 - Light extraction elements for indirect light distribution

Info

Publication number: WO2015074154A1
Application number: PCT/CA2014/051114
Authority: WO
Inventors: Scott Santoro
Original assignee: Fluxwerx Illumination Inc.
Priority date: 2013-11-22
Filing date: 2014-11-21
Publication date: 2015-05-28

Abstract

A light guide for a luminaire for lighting at least an upper hemisphere of the luminaire is provided. The light guide includes: a light source receiving surface; and a first major surface extending in a downstream direction away from the light source receiving surface. The first major surface comprising an indirect extraction element, wherein a cross-section of the indirect extraction element comprising a serpentine contour.

Description

LIGHT EXTRACTION ELEMENTS FOR INDIRECT LIGHT DISTRIBUTION

Technical Field

[0001] This invention relates to light extraction elements for indirect light distribution, in particular for light guides of light emitting panel assemblies such as luminaires.

Background

[0002] 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.

[0003] Suspended luminaires can emit light into either the upper or lower hemisphere. The upper hemisphere is the area above the horizontal plane of the luminaire. The source of the light emitted into the upper hemisphere is typically not viewable from occupants of a space until it reflects off a surface above the luminaire. This portion of the light distribution is referred to as the indirect distribution. This light serves a variety of purposes, including: providing ambient light to the space reflected off of the ceiling; reducing glare by spreading the visible light over a large area in the space; and allowing increased fixture spacing reducing the number of fixtures required in a space by spreading the light over a large area above the luminaire.

[0004] The lower hemisphere is the area below the horizontal plane of the luminaire. The light emitted from the luminaire into the lower hemisphere primarily arrives directly onto the workplane. As such, this portion of the distribution is referred to as the direct distribution. This light also serves a variety of purposes, including: providing illumination of the space; increasing efficiency of delivered light to the surface by eliminating losses during reflection off of ceiling surfaces; and providing visual luminance on the surface of the luminaire improving occupants well being by giving a sense of the source. Indirect fixtures which do not have a direct component create a cloudy day type of effect due the lack of visual contrast in a space. [0005] An ideal indirect optic evenly and homogeneously illuminates a large area above the luminaire. This is accomplished by creating optics that distribute a significant portion of the light leaving the luminaire in the upper hemisphere at high angles just above the horizontal plane of the luminaire. This limits light directly above the luminaire and redistributes the light further away from the luminaire. The angle at which the strongest point in the distribution occurs is referred to as the peak angle. A metric used to define the performance of an indirect distribution is the Peak to Zenith ratio. This is the level of light leaving from directly above the luminaire (Zenith) to the light leaving at the peak angle. In general to evenly illuminate the ceiling it is preferred to have a high as peak angle as possible and a high Peak to Zenith ratio. How evenly the ceiling is illuminated is dictated by the inverse cosine law:

E=ICos(0)/D2

Where in this case:

E = Illuminance on the ceiling.

I = Intensity of the luminaire at an angle Θ from Nadir of the luminaire

Θ = The angle at which light is incident on the ceiling from the normal to the ceiling. In the case of a luminaire which is mounted without tilt this angle would be equal to the intensity angle. D = The distance from the source in this case from the luminaire to the point at which the light is incident on the ceiling.

[0006] The ideal distribution is governed by this equation in which the intensity varies at the various angles theta to maintain an equal illuminance level E on the ceiling.

[0007] A further optical characteristic is that the distribution needs to illuminate the ceiling without striations, color variations, and hotspots. This involves creating an optic in which the intensity smoothly changes and is consistent in color throughout the distribution. This final optical characteristic can be difficult to accomplish.

[0008] Light extraction elements with improved indirect light distribution for suspended luminaires are desirable. Summary

[0009] In one aspect, a light guide for a luminaire for lighting at least an upper hemisphere of the luminaire is provided. The light guide comprising: a light source receiving surface; a first major surface extending in a downstream direction away from the light source receiving surface, the first major surface comprising an indirect extraction element, wherein a cross-section of the indirect extraction element comprising a serpentine contour.

[0010] The first major surface may comprise an upper hemisphere-facing portion, and the upper hemisphere-facing portion may comprise the indirect extraction element. The serpentine contour may comprise curved and non-curved portions or a continuously curved portion. The serpentine contour may comprise a sinusoidal contour.

[0011] Sinusoids of the sinusoidal contour may each comprise an upstream face and a downstream face, wherein the upstream face comprises a planar surface and the downstream face comprises a non-planar surface. The non-planar surface may be wavy across a width of the light guide. The non-planar surface may comprise horizontal grooves. The sinusoidal contour may comprise at least two periods. Sinusoids of the sinusoidal contour may decrease in amplitude and/or wavelength in the downstream direction.

[0012] Sinusoids of the sinusoidal contour may comprise an amplitude ranging from 5% to 60%, or 10% to 50%, of an average thickness of the light guide. Sinusoids of the sinusoidal contour 10% to 50% periods ranging from 10% to 150%, or 25% to 90%, of an average thickness of the light guide. A length of the indirect extraction element may be less than 20 mm, or less than 12 mm. The indirect extraction element may comprise a diffuse surface.

[0013] The light guide may comprise a horizontally extending upstream region and a vertically extending downstream region, wherein the horizontally extending upstream region and the vertically extending downstream region are joined by a curved mid-region, and wherein the horizontally extending upstream region comprises the light source receiving surface and the indirect extraction element. The indirect extraction element may be adjacent to the light source receiving surface.

[0014] The light guide may be generally Y-shaped and comprise two horizontally extending upstream regions and a vertically extending downstream region, wherein the horizontally extending upstream regions curve to join to form the vertically extending downstream region, and wherein each of the horizontally extending upstream regions comprise the light source receiving surface and the indirect extraction element. In each horizontally extending upstream region, the indirect extraction element may be adjacent to the light source receiving surface.

[0015] The light guide may taper in the downstream direction. The indirect extraction element may span horizontally across the first major surface. The indirect extraction element may be integral with the light guide. The light guide may comprise a substrate and a film, wherein the film comprises the first major surface and is applied on the substrate.

[0016] According to another aspect, a method of making a light guide is provided. The method comprises extruding a thermoplastic polymeric material through a die corresponding to the cross sectional shape of a light guide as described herein. [0017] According to further aspect, a method of making a light guide is provided. The method comprises injecting a polymeric material into a mold shaped according to a light guide as described herein.

[0018] According to another aspect, a method of making a light guide is provided. The method comprises applying to at least one major surface of a substrate a film comprising an indirect extraction element as described herein.

[0019] According to a further aspect, a light emitting panel assembly is provided. The assembly comprise: at least one light guide according as described herein; and at least one array of light sources in optical communication with the light source receiving surface of the light guide. The at least one array of light sources may be an LED array.

[0020] According to another aspect, a luminaire is provided. The luminaire comprises: a housing; two arrays of light sources facing away from each other; two light guides as described herein, wherein the light source receiving surface of each of the light guides is in optical communication with a respective one of the arrays of light sources, wherein each of the guides comprise a second major surface opposite the first major surface; two reflectors, each of the reflectors adjacent, abutting, or integral with a respective second major surface along at least the horizontally extending upstream region and curved mid-region, whereby the light guide is configurable to emit a batwing distribution of light in at least an upper hemisphere of the luminaire. The arrays of light sources may be LED arrays.

[0021] According to another aspect, a luminaire is provided. The luminaire comprises: a housing; two arrays of light sources facing toward each other; a light guide as described herein, wherein each of the light source receiving surfaces of the light guide are in optical communication with a respective one of the arrays of light sources, wherein the light guide comprise two second major surfaces opposite the first major surface along the horizontally extending upstream region and defining the vertically extending downstream region; two reflectors, each of the reflectors adjacent, abutting, or integral with a respective second major surface along at least the horizontally extending upstream region, whereby the light guide is configurable to emit a batwing distribution of light in at least an upper hemisphere of the luminaire. The arrays of light sources may be LED arrays. Brief Description of the Drawings

[0022] In drawings which show non-limiting embodiments of the invention:

Figure 1 is a partial cross-sectional view of a light guide in a light emitting panel assembly according to an embodiment;

Figure 1A is a close-up partial cross-sectional view of the light guide of Figure 1; Figure 2 is a partial cross-sectional view of the light guide of Figure 1 showing paths of exemplary light rays;

Figure 3 is a close-up partial cross-sectional view of the light guide of Figure 1 showing paths of exemplary light rays;

Figure 4 is an optical distribution plot of light emitted from the light guide of Figure

1;

Figure 5 is a partial cross-sectional view of light guides in a light emitting panel assembly according to an embodiment;

Figure 5A is a close-up partial cross-sectional view of one of the light guides of Figure 5;

Figure 6 is a partial cross-sectional view of the light guides of Figure 5 showing paths of exemplary light rays;

Figure 7 is a close-up partial cross-sectional view of one of the light guide of Figure 5 showing paths of exemplary light rays;

Figure 8 is an optical distribution plot of light emitted from the light guides of Figure 5;

Figures 9A to 9E are close-up partial cross-sectional views of indirect extraction elements of light guides according to embodiments;

Figures 10A to 10E are close-up partial cross-sectional views of indirect extraction elements of light guides according to embodiments; and

Figure 11 is a partial perspective view of a light guide according to an embodiment.

Description

[0023] Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention 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 invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

[0024] The terms "upstream" and "downstream" as used herein relate to an arrangement of features relative to the light source, wherein relative to a first position from the light source, a second position closer to the light source is "upstream", and a third position further away from the light source is "downstream".

[0025] The term "light source" as used herein refers to any point source emitter of light, including LEDs, laser diodes, and the like.

[0026] The term "cross-section" or "cross- sectional" as used herein refers to a cross-section plane of the light guide parallel to the plane along which light guide extends away from the light source. [0027] The small size of LEDs allow precision distributions to be created with equally small optics. For indirect optics, LEDs however create challenges in illuminating a surface, for example a ceiling, in a homogeneous manner. The primary challenge is that LEDs typically vary in color temperature depending on the angle from the normal of the LED. This effect is referred to as "color over angle". This is due to the amount of phosphor the light has to travel through before it leaves the LED. In many LEDs, light at angles close to the normal travel through less phosphor than the light at angles further from the normal. As the phosphor shifts the light towards warmer color temperatures the more phosphor light travels through the greater the color shift. Therefore the light that leaves an LED at high angles from its normal does so at a warmer color temperature than the light that leaves at angles closer to the normal. An ideal indirect optic needs to mix the light leaving from the LED in a manner that the color is blended at the ceiling into a uniform color temperature. Traditional optical designs do not account for this issue. As such new optical approaches are required.

[0028] Figures 1 to 3 illustrate a light guide 10 which form part of a light emitting assembly 1, both according to example embodiments. Figure 2 and 3 illustrate exemplary light rays emitted by light guide 10/light emitting panel assembly 1. Figure 4 illustrates an optical distribution plot of light emitted from light guide 10/ light emitting panel assembly 1, in particular a wide batwing indirect distribution. Light emitting panel assembly 1 may for example be a luminaire. [0029] Figure 1 shows a cross section of light emitting assembly 1 which includes light guide 10, light sources 2, light source boards 4, and reflectors 6. In some embodiments, light sources 2 may be LED arrays, and light source boards 4 may be LED boards. Reflectors 6 may for example be any reflective flat sheet material. In some embodiments reflectors 6 may be a reflective coating applied to light guide 10. In some of these embodiments reflectors 6 may be specularly reflective. In other embodiments the reflectors 6 may be absent.

[0030] Light guide 10 includes first major surfaces 12 and second major surfaces 14. Light source receiving surfaces 16 of light guide 10 are configured for optical communication with light sources 2. Each first major surface 12 includes an upper hemisphere-facing portion 18, and each upper hemisphere-facing portion 18 includes an indirect extraction element 20. In embodiments such as that illustrated, indirect extraction element 20 is located adjacent to light source receiving surface 16. [0031] As shown in Figures 2 and 3, indirect extraction elements 20 are configured to distribute light in an upper hemisphere of the luminaire in which light emitting panel assembly 1 is installed.

[0032] Figure 1A shows details of indirect extraction element 20. Indirect extraction element 20 has a generally serpentine contour. The term "serpentine" contours as used herein refers to contours that consist of a combination of continuously curved portions and non-curved portions, for example as shown in Figures 9A to 9E, and contours that are continuously curved, for example as shown in Figures 10A to 10E. In some embodiments, where the contour consists of curved and non-curved portions, the curved portions comprise at least 50% of the contour. In some embodiments, as shown in Figure 1A, the serpentine contour may be continuously curved in the form of a sinusoidal contour. The inventors have determined that serpentine contours increase the amount of extraction over a set distance as more of the light rays interact with the indirect extraction element than a wedged and/or diffuse- surface structure over the same distance. The inventors have also determined that rays hitting a wide variety of angles on the indirect extraction element also has the added advantage of mixing the input angles as they are extracted out of the light guide to limit or substantially eliminate the unwanted effects of color over angle. [0033] The length L of indirect extraction element 20 in some embodiments is less than 20 mm, and in some embodiments is less than 12 mm. In some embodiments, indirect extraction element 20 may comprise at least two periods of sinusoids. In some embodiments the sinusoids may decrease in amplitude and/or period in the upstream to downstream direction. For example, as shown in Figure 1A, amplitude Ai and period Pi of the first sinusoid are greater than amplitude A₂ and period P₂ of the second sinusoid, where the first sinusoid is upstream of the second sinusoid. This decrease in amplitude (and therefore peak size) in the downstream direction facilitates light to be extracted at high angles without hitting the next, downstream peak(s).

[0034] In some embodiments, the amplitude of the sinusoids of indirect extraction element 20 may range from 5% to 60%, or 10% to 50%, of the average thickness of the light guide at indirect extraction element 20. The average thickness of the light guide at indirect extraction element 20 is determined herein as half of the sum of the thickness of light guide 10 at the upstream end of indirect extraction element 20 (e.g. Ti shown in Figures 1 A and 5A) and thickness of light guide 10 at the upstream end of indirect extraction element 20 (e.g. T₂ shown in Figures 1A and 5A).

[0035] In some embodiments, the period of the sinusoids of indirect extraction element 20 may range from 10% to 150%, or 25% to 90%, of the average thickness of the light guide at indirect extraction element 20.

[0036] As shown in Figure 1A, plane Pc is a plane upon which curved portions of indirect extraction element 20 are centered, and plane P_E is a plane parallel to the direction of extension of the light guide in the upstream to downstream direction. In some embodiments, plane Pc may be angled at angle Θ relative to a plane P_E. In some embodiments angle Θ may range from 0 to 45 degrees, and in some embodiments may range from 0 to 90 degrees.

[0037] Figures 5 to 7 illustrate light guides 110 which form part of a light emitting panel assembly 100, both according to example embodiments. Figure 6 and 7 illustrate exemplary light rays emitted by light guides 110/light emitting panel assembly 100. Figure 8 illustrates an optical distribution plot of light emitted from light guides 110/light emitting panel assembly 100, in particular a high peak to zenith ratio with a homogeneous distribution. Components of light guides 110/light emitting panel assembly 100 are similar to components of light guide 10/light emitting assembly 1 in structure and function. In particular light sources 102, light source boards 104, reflectors 106, first major surface 112, second major surface 114, light source receiving surfaces 116, upper hemisphere facing portions 118, and indirect extraction elements 120 of light guides 110/light emitting panel assembly 100 correspond to like components of light guide 10/light emitting assembly 1. Figure 5 also shows housing 122 of light emitting assembly 100 which supports light guides 110, reflectors 106 and light source boards 104.

[0038] Figure 11 illustrates a light guide 210 according to another example embodiment.

Components of light guide 210 are similar to components of light guide 10 in structure and function. Indirect extraction element 220 of light guide 210 in the illustrated embodiment includes two sinusoids. The upstream sinusoid has greater amplitude than the downstream sinusoid, allowing more light to be extracted at high angles from the upstream sinusoid without hitting the downstream sinusoid. In other embodiments, indirect extraction element 220 may comprise more, or less, than two sinusoids, and the amplitudes of the sinusoids may or may not decrease in the upstream to downstream direction. [0039] Each sinusoid of light guide 210 has an upstream face 232 and a downstream face 234. Upstream face 232 comprises a planar surface, and may be smooth or be configured for diffuse refraction. Downstream face 234 comprises a non-planar surface. The non-planar surface may include continuous or intermittent alternating protrusions and depressions. For example, the non-planar surface may be scalloped across the width of light guide 210 as shown in Figure 11. The non-planar surface of downstream face 234 increases the amount of light extracted and increases light mixing to reduce or eliminate color over angle effects. In some embodiments, downstream face 234 may also be configured for diffuse refraction, for example comprising an array of horizontal grooves 236 extending across the width of light guide 210 as shown in Figure 11. In some embodiments, the non-planar surface of downstream face 234 may be smooth. In other embodiments, downstream face 234 may be planar, and may be smooth or be configured for diffuse refraction.

[0040] Figure 11 also shows that, downstream of indirect extraction element 220, major surface 212 of light guide 210 features vertically extending flutes 238. Flutes 238 facilitate total internal reflection of light within light guide 210 and prevent unintended extraction or loss of light. The function and structure of flutes 238 is described in detail in WO2013131167, incorporated by reference herein. [0041] In some embodiments, such as those illustrated herein, the extraction elements are integrally formed with the light guide. In such embodiments, the light guide may be formed by extruding a thermoplastic polymeric material through a die corresponding to the desired cross sectional shape of the light guide, or by injecting a polymeric material into a mold in the shape of the light guide. For example, light guide 20 as shown in Figure 1 is designed for injection molding with a vertical slider from the top of the guide, and light guide 120 as shown in Figure 5 is designed for an injection mold which separates up and to the left (for the left light guide) or to the right (for the right light guide). An advantage of the present invention, and in particular embodiments such as those illustrated, is that their design limits variations in thickness of the light guide, which is important during injection molding and extrusion processes. In other embodiments, the light guide may be formed by applying to each side of a panel a film comprising one or more extraction elements.

[0042] As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention. For example, in some embodiments:

• the indirect extraction element of the light guide may additionally be configured for diffuse refraction, which allows light to be released in a homogeneous manner eliminating striations on the ceiling. Diffuse refraction may be provided at or adjacent the surface of the indirect extraction element. For example, diffuse refraction may be achieved by providing a diffuse surface, overlaying a diffuse film on the surface, providing a diffuse material within the light guide immediately underneath the face, and the like. In some embodiments, the diffusion may be in a linear pattern (e.g. ridges or grooves aligned along the normal of the upstream/downstream plane), while in other embodiments the diffusion may be non-linear or random (e.g. randomly arranged bumps or dimples).

• light guide may additionally taper or be wedge-shaped. Such a shape facilitates release of light at high angles from the normal of the guide. Once light enters the light guide the light that is traveling through at angles close to Brewster's angles will be primarily released when the slope of the light guide causes the light to intersect the boundary at angles slightly below Brewster's angle. This light will be released at high angles from the normal of the guide according to the Fresnel Equations.

• the light guide may, instead of curving downward, continue to extend horizontally; curve upward; or end after the indirect extraction element.

• the light source and light source receiving surface may be provided at the bottom of the light guide, with the indirect extraction element situated at the top of the light guide.

• a light emitting panel assembly may have one or more than one light guide as described herein. For example some embodiments may be a light emitting panel assembly similar to light emitting panel assembly 100 but having only one light guide 110, in which case the indirect distribution would be asymmetric, i.e., only the left half or right half of the distribution illustrated in Figure 8.

[0043] This application is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims. Accordingly, the scope of the claims should not be limited by the preferred embodiments set forth in the description, but should be given the broadest interpretation consistent with the description as a whole.

Claims

1. A light guide for a luminaire for lighting at least an upper hemisphere of the luminaire, the light guide comprising:

a light source receiving surface;

a first major surface extending in a downstream direction away from the light source receiving surface, the first major surface comprising an indirect extraction element, wherein a cross-section of the indirect extraction element comprising a serpentine contour.

2. A light guide according to claim 1, wherein the first major surface comprises an upper hemisphere-facing portion, and wherein the upper hemisphere-facing portion comprises the indirect extraction element.

3. A light guide according to claim 1 or 2, wherein the serpentine contour comprises curved and non-curved portions.

4. A light guide according to claim 1 or 2, wherein the serpentine contour comprises a

continuously curved portion.

5. A light guide according to claim 3 or 4, wherein the serpentine contour comprises a

sinusoidal contour.

6. A light guide according to claim 5, wherein sinusoids of the sinusoidal contour each

comprise an upstream face and a downstream face, wherein the upstream face comprises a planar surface and the downstream face comprises a non-planar surface.

7. A light guide according to claim 6 wherein the non-planar surface is wavy across a width of the light guide.

8. A light guide according to claim 7 wherein the non-planar surface comprises horizontal grooves.

9. A light guide according to any one of claims 5 to 8, wherein the sinusoidal contour comprises at least two periods.

10. A light guide according to claim 9 wherein sinusoids of the sinusoidal contour decrease in amplitude and/or wavelength in the downstream direction.

11. A light guide according to claim 9 or 10 wherein sinusoids of the sinusoidal contour comprise an amplitude ranging from 5% to 60% of an average thickness of the light guide.

12. A light guide according to claim 11, wherein the amplitude ranges from 10% to 50% of the average thickness of the light guide.

13. A light guide according to any claim 9 or 10 wherein sinusoids of the sinusoidal contour comprise periods ranging from 10% to 150% of an average thickness of the light guide.

14. A light guide according to claim 13, wherein the periods range from 25% to 90% of the average thickness of the light guide.

15. A light guide according to any one of claims 1 to 14 wherein a length of the indirect extraction element is less than 20 mm.

16. A light guide according to any one of claims 1 to 14 wherein a length of the indirect extraction element is less than 12 mm.

17. A light guide according to any one of claims 1 to 16 wherein the indirect extraction element comprises a diffuse surface.

18. A light guide according to any one of claims 1 to 17 comprising a horizontally extending upstream region and a vertically extending downstream region, wherein the horizontally extending upstream region and the vertically extending downstream region are joined by a curved mid-region, and wherein the horizontally extending upstream region comprises the light source receiving surface and the indirect extraction element.

19. A light guide according to claim 18 wherein the indirect extraction element is adjacent to the light source receiving surface.

20. A light guide according to any one of claims 1 to 17 wherein the light guide is generally Y-shaped and comprises two horizontally extending upstream regions and a vertically extending downstream region, wherein the horizontally extending upstream regions curve to join to form the vertically extending downstream region, and wherein each of the horizontally extending upstream regions comprise the light source receiving surface and the indirect extraction element.

21. A light guide according to claim 20 wherein, in each horizontally extending upstream region, the indirect extraction element is adjacent to the light source receiving surface.

22. A light guide according to any one of claims 1 to 21 wherein the light guide tapers in the downstream direction.

23. A light guide according to any one of claims 1 to 22 wherein the indirect extraction element spans horizontally across the first major surface.

24. A light guide according to any of claims 1 to 23 wherein the indirect extraction element is integral with the light guide.

25. A light guide according to any of claims 1 to 23 comprising a substrate and a film, wherein the film comprises the first major surface and is applied on the substrate.

26. A method of making a light guide comprising extruding a thermoplastic polymeric material through a die corresponding to the cross sectional shape of a light guide according to any one of claims 1 to 25.

27. A method of making a light guide comprising injecting a polymeric material into a mold shaped according to a light guide according to any one of claims 1 to 25.

28. A method of making a light guide comprising applying to at least one major surface of a substrate a film comprising an indirect extraction element according to any one of claims 1 to 25.

29. A light emitting panel assembly comprising:

at least one light guide according to any one of claims 1 to 25;

at least one array of light sources in optical communication with the light source receiving surface of the light guide.

30. A light emitting panel assembly according to claim 29 wherein the at least one array of light sources is an LED array.

31. A luminaire comprising :

a housing;

two arrays of light sources facing away from each other;

two light guides according to claim 18 or 19, wherein the light source receiving surface of each of the light guides is in optical communication with a respective one of the arrays of light sources, wherein each of the guides comprise a second major surface opposite the first major surface;

two reflectors, each of the reflectors adjacent, abutting, or integral with a respective second major surface along at least the horizontally extending upstream region and curved mid-region,

whereby the light guide is configurable to emit a batwing distribution of light in at least an upper hemisphere of the luminaire.

32. A luminaire comprising:

a housing;

two arrays of light sources facing toward each other;

a light guide according to claim 20 or 21, wherein each of the light source receiving surfaces of the light guide are in optical communication with a respective one of the arrays of light sources, wherein the light guide comprise two second major surfaces opposite the first major surface along the horizontally extending upstream region and defining the vertically extending downstream region;

two reflectors, each of the reflectors adjacent, abutting, or integral with a respective second major surface along at least the horizontally extending upstream region,

A luminaire according to claim 31 or 32 wherein the arrays of light sources are LED arrays.