摘要：
A lighting system uses an edge lit waveguide. The bottom has a set of elongate light extraction features for out-coupling light from the light guide towards a reflector which reflects light back into the light guide. The top face of the light guide functions as the output for the lighting system. In some examples it has a set of elongate beam shaping features extending substantially orthogonally to the set of light extraction 5 features for beam shaping of light exiting the top face.
技术功效语段：
[0019]The light guide performs two functions. A first is to extract light preferentially from the bottom face, towards the reflector. After reflection, the same light guide functions acts as an optical transmission plate. It may for example mainly transmit light with a low angle (for example less than 60 degrees) to the normal and this optical transmission then implements a beam shaping function. By the feature that each light extraction feature extends continuously and essentially over the full length of the lighting arrangement, the risk on crosstalk and undesired reflections/refractions, caused by end faces of said light extraction features, is reduced compared to the (risk on) glare resulting from the known light extraction features of US2002136996.
[0025]The light guide system can be made with a low profile and is simple to construct. It enables a non-collimated light source to be used, such as LEDs without collimation.
[0029]The reflector may be a white diffuse reflector. This is simple to manufacture. Alternatively, the reflector may be a specular reflector with a diffuser over the top. This diffuser may comprise a Gaussian diffuser to (better) obtain a highly desired delta-shaped intensity pattern.
[0032]These relationships enable nearly all light to be extracted from the light extraction features, instead of being reflected internally to the top face where the light may then escape before being passed to the reflector.
权利要求：
1. A lighting system, comprising: a light guide (30) having a top face and a bottom face and outer edges extending between the top and bottom faces; a lighting arrangement (32) for coupling light into at least one of the outer edges of the light guide; and a reflector (34) arranged beneath the bottom face having a diffuse reflection function, wherein the light guide (30) comprises a set of light extraction features (38) on the bottom face for out-coupling light from the light guide (30) towards the reflector (34), each light extraction feature (38) extending over at least 80% of the full length of the lighting arrangement (32) alongside the lighting arrangement, wherein the light extraction features (38) have a maximum width w and a height h and the material of the light guide has a refractive index n, wherein: 1.2 n 2 − 1 ≤ h w ≤ 3 n 2 − 1 , wherein the lighting system further comprises an air gap (36) between the bottom face of the light guide (30) and the reflector (34) which has a height of more than 1.5 times the average pitch between the light extraction features (38).
2. A lighting system as claimed in claim 1, wherein the light extraction features (38) comprise pillars having a length 1, wherein the length 1 is at least hundred times larger than the width w and/or the height h.
3. A lighting system as claimed in any preceding claim, wherein the reflector (34) is a white diffuse reflector or a specular reflector with a Gaussian diffuser over the top.
4. A lighting system as claimed in any preceding claim, wherein the light extraction features (38) extend between -5 degrees and +5 degrees to an edge into which light is coupled into the light guide.
5. A lighting system as claimed in any preceding claim, wherein the light extraction features (38) comprise pillars extending alongside the length of the lighting arrangement (32), each with a rectangular or tapered rectangular cross section.
6. A lighting system as claimed in any preceding claim, wherein the lighting extraction features (38) are arranged with an average pitch p, and wherein: p w ≥ 10
7. A lighting system as claimed in claim 4, 5, or 6, wherein each lighting extraction feature (38) has a tapered cross section to taper to a thinner dimension at its end with a taper angle of less than 10 degrees, more preferably less than 5 degrees.
8. A lighting system as claimed in any preceding claim, wherein the light extraction features (38) comprise pillars extending alongside the length of the lighting arrangement, each with a semi-circular cross section.
9. A lighting system as claimed in any preceding claim, wherein the light guide comprises a set of beam shaping features (40) on the top face, a length direction of the beam shaping features (40) extending between 85 and 95 degrees to the set of light extraction features (38), for beam shaping of light exiting the top face and each beam shaping feature (40) extending over at least 80% from one outer edge to the opposite outer edge on the top face.
10. A lighting system as claimed in claim 9, wherein the beam shaping features (40) comprise prism structures.
11. A lighting system as claimed in any preceding claim, wherein the lighting arrangement comprises an LED (32) arrangement provided at one edge or at a pair of opposing parallel edges of the light guide.
12. A lighting method, comprising: coupling light into at least one outer edge of a light guide (30) with a lighting arrangement (32), the light guide (30) having a top face and a bottom face and outer edges extending between the top and bottom faces; out-coupling light from the bottom face of the light guide (30) using a set of light extraction features (38) extending over at least 80% of the full length of the lighting arrangement (32) on the bottom face alongside the lighting arrangement (32); reflecting light which passes out of the bottom face using a reflector (34) having a diffuse reflection function, thereby returning reflected, diffused light into the light guide (30); and issuing reflected, diffused light as output light from the top face of the light guide (30), wherein the light extraction features are fulfilling the equation: 1.2 n 2 − 1 ≤ h w ≤ 3 n 2 − 1 with n being the refractive index of material of the light guide; w and h being respectively a maximum width and a height of the light extraction features, and wherein an air gap (36) is provided between the bottom face of the light guide (30) and the reflector (34) which has a height of more than 1.5 times the average pitch between the light extraction features (38).
13. A method as claimed in claim 12, wherein providing output light from the top face of the light guide (30) comprises using a set of beam shaping features (40) extending over at least 80% from one outer edge to the opposite outer edge on the top face, a length direction of the beam shaping features (40) extending between 85 and 95 degrees to the set of light extraction features (38), thereby beam shaping the output light exiting the top face.