WO2011109866A1

WO2011109866A1 - Lighting apparatus with a waveguide and a reflective matrix

Info

Publication number: WO2011109866A1
Application number: PCT/AU2011/000261
Authority: WO
Inventors: Tomas Blach
Original assignee: Associated Controls (Australia) Pty Ltd
Priority date: 2010-03-08
Filing date: 2011-03-08
Publication date: 2011-09-15

Abstract

A lighting apparatus comprises an optically transparent waveguide having an upper face, a lower face and one or more edge faces. A light source emits light rays into the waveguide and a reflective matrix is formed on one of the upper face or the lower face of the waveguide. One of the upper face or the lower face of the waveguide forms a light directing region which is shaped such that light rays which directly contact the light directing region after ejection from the light source are substantially internally reflected.

Description

LIGHTNING APPARATUS WITH A WAVEGUIDE AND A REFLECTIVE MATRIX

FIELD OF THE INVENTION

The present invention relates to the field of lighting. More particularly, this invention relates to an improved LED lighting apparatus.

5 BACKGROUND OF THE INVENTION

In the modern world, lighting devices are ubiquitous and the demand for more effective, energy efficient and visually pleasing lighting is ever •present. In recent times, resources and the depletion of fossil fuels has come to the fore and so the efficiency of lighting has become a more important

10 factor in the market place. Environmental concerns have also meant that lighting, such as fluorescent lighting, which contain toxins such as mercury and rare earth metals are now losing popularity. This has caused a shift from traditional lighting, such as incandescent bulbs and fluorescent lighting, to those Using light emitting diodes (LEDs).

15 LEDs have a high light output for a physically very small device, particularly in comparison to a fluorescent light, and are extremely energy efficient. However, the high intensity light output does present drawbacks which have limited the use of LEDs in certain lighting applications. Due to their small size a relatively large number of LEDs will often be used and this

20 can create a visually displeasing multiple shadow effect due to the intense aura around each individual LED being visible to the viewer.

Further, LEDs tend to suffer from blue and UV 'spillage' from the primary semiconductor light generator which is not captured and converted appropriately. This usually manifests itself as a blue halo, or like region as a

25 function of angular deviation from the normal to the source. This is an aesthetically displeasing effect that changes the color as a function of viewing angle and thus makes many LED lamps unsuitable for general lighting application.

There is, therefore, a need for a lighting apparatus which can harness

30 the advantageous high light output of LEDs but at the same time address the disadvantages to achieve a more evenly distributed light which is emitted to the viewer. OBJECT OF THE INVENTION

It is therefore an object of the invention to overcome or alleviate at least one of the aforementioned deficiencies in the prior art or at least provide a useful or commercially attractive alternative.

1 SUMMARY OF THE INVENTION

In one form, although it need not be the only or indeed the broadest form, the invention resides in a lighting apparatus comprising:

(a) an optically transparent waveguide comprising an upper face, a lower face and one or more edge faces;

(b) a light source emitting light rays into the waveguide; and

(c) a reflective matrix adjacent one of the upper face or the lower face of the waveguide;

wherein, one of the upper face or the lower face of the waveguide comprises a light directing region which is shaped such that light rays which directly contact the light directing region after ejection from the light source are substantially internally reflected.

Suitably, the light directing region is shaped such that the majority of light rays emitted from the light source which directly contact the light directing region will make contact at an angle greater than the critical angle.

Preferably, substantially all of the light rays emitted from the light source which directly contact the light directing region will make contact at an angle greater than the critical angle.

Preferably, the substantially internally reflected light is reflected directly onto the reflective matrix.

The face of the waveguide adjacent the reflective matrix may be opposite the face of the waveguide comprising the light directing region.

Suitably, the light source associated with the waveguide is one or more LEDs.

The light directing region is shaped such that the majority of light rays emitted from the one or more LEDs and travelling substantially parallel to an edge face joining the upper face and lower face of the waveguide will contact the light directing region before contacting another face of the waveguide. Preferably, the reflective matrix is adjacent the lower face of the waveguide and the light directing region is formed on the upper face of the waveguide, the upper face being the face from which light is emitted.

Preferably, the light directing region is angled towards the lower face of the waveguide such that light emitted from the one or more LEDs and travelling parallel to the lower face will contact the light directing region and be substantially internally reflected towards the reflective matrix.

Preferably, the one or more LEDs are disposed adjacent an edge face of the waveguide.

Suitably, the one or more LEDs are located within a complimentary recess within an each edge face of the waveguide.

⁴ Preferably, the reflective matrix is formed on the lower face of the waveguide.

Suitably, the reflective matrix is painted or printed onto the lower face of the waveguide.

In one embodiment the reflective matrix comprises a fluorescent material.

The reflective matrix may be an alternating pattern of reflective portion adjacent non-reflective portion.

Suitably, the size of the reflective portions relative to the non-reflective portions increases with increasing distance from the one or more LEDs.

Preferably, each edge face of the waveguide is provided with an internally reflective surface.

Suitably, the internally reflective surface is a mirror coating.

The lighting apparatus may further comprise a reflective layer beneath the reflective matrix to reflect light rays which exit through the non-reflective portions back into the waveguide.

The lighting apparatus may further comprise a housing at least partially enclosing the waveguide.

In one embodiment the invention resides in two or more of the lighting apparatus operatively associated to increase the total amount of light ejected towards the viewer. Preferably, the lower surface of one lighting apparatus is placed adjacent the upper surface of another lighting apparatus.

Suitably, the reflective and non-reflective portions of respective reflective matrices are not in alignment.

In one embodiment, the invention resides in a lighting apparatus comprising:

(a) an optically transparent waveguide comprising a light directing face, a reflective matrix face and one or more edge faces;

(b) a light source associated with the waveguide; and

wherein, the light directing face is angled with respect to the light source such that light rays emitted therefrom and directly incident upon the light directing face are substantially internally reflected onto the reflective matrix face to thereby eject light from the waveguide after a minimal number of internal reflections.,

A lighting system comprising a first lighting apparatus stacked on top of a second lighting apparatus wherein each of the first and second lighting apparatus comprise an optically transparent waveguide comprising a light directing face, a reflective matrix face and one or more edge faces, a light source associated with an edge face, and wherein the light directing face is angled with respect to the light source such that substantially all of the light rays emitted therefrom and directly incident upori the light directing face make contact at an angle greater than the critical angle.

Further features of the present invention will become apparent from the following detailed description.

Throughout this specification, unless the context requires otherwise, the words "comprise", "comprises" and "comprising" will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

BRIEF DESCRIPTION OF THE FIGURES

In order that the invention may be readily understood and put into practical effect, preferred embodiments will now be described by way of example with reference to the accompanying figures wherein like reference numerals refer to like parts and wherein:

FIG 1 is a plan view and a cross sectional view of an exploded schematic representation of one embodiment of a lighting apparatus;

FIG 2 is a representation of the path taken by three light rays through one embodiment of a waveguide;

FIG 3 is a plan and side view representation of two embodiments of LED arrangement;

FIG 4 is a plan view and a cross sectional view of one embodiment of a waveguide;

FIG 5 is a plan view and a cross sectional view of one embodiment of a lighting apparatus;

FIG 6 is a plan view and a cross sectional view of an alternative embodiment of a lighting apparatus;

FIG 7 is a plan view and a cross sectional view of a further alternative embodiment of a lighting apparatus;

FIG 8 is a plan view and a cross sectional view of yet a further alternative embodiment of a lighting apparatus;

FIG 9 is a representation of one embodiment of a reflector matrix; FIG 10 is a plan view and a cross sectional view of one embodiment of a lighting apparatus with housing and power source; and

FIG 11 is a side view of two lighting apparatus when stacked together.

DETAILED DESCRIPTION OF THE INVENTION

, FIG 1 is a plan view and a cross sectional view of an exploded schematic representation of one embodiment of a lighting apparatus 10. Lighting apparatus 10 comprises a plurality of light emitting diodes (LEDs) 11 disposed on a circuit board 12 which is connected to an external power source (not shown) by power connection 13. LEDs 11 may be chosen from a wide variety of commercially available LEDs. In one embodiment the LEDs 11 may be gallium nitride ultra-high brightness LEDs. RGB LEDs are also suitable for use. Generally, any high powered LED may be useful in the present lighting apparatus. High brightness LEDs offer improved power efficiency and so are preferred.

In one embodiment a UV light source may be suitable for use with the present lighting apparatus when the reflective matrix is photoluminescent.

An optically transparent waveguide 14 is provided with a plurality of recesses 15 which are shaped to receive the LEDs 11. Waveguide 14 may be manufactured from a range of materials suitable for optical applications including but not limited to clear acrylic, glass or polyethylene. Recesses 15 may be formed in, machined from or in some manner cut out of waveguide 14 and subsequently highly polished to thereby closely match the external contours of the particular LEDs 11 being used such that LEDs 14 are a close fit to eliminate or greatly minimise any potential air gap between the LEDs 1 and waveguide 14. In the embodiment shown in FIG 1 recesses 15 are formed along one of edge faces 16 of waveguide 14 but may be formed in more than one, or indeed all, of edge faces 16. All of edge faces 16 are provided with an internally reflective coating 17 which may be formed by white paint, print or a reflective tape. The reflective coating 17 should form a substantially airless union i.e. no air gap, with edge faces 16. Preferably, reflective coating 17 is a mirror coating formed on edge faces 16 to ensure all light contacting edge faces 16 is internally reflected and none is lost to the environment or reduced in intensity due to the effect of an air gap.

Waveguide 14 can be split, functionally, into two zones. The first zone is light mixing zone 18 which is a part of waveguide 14 where upper face 19 and lower face 20 of waveguide 14 are substantially parallel. This is the zone into which light is emitted by LEDs 11 to undergo mixing and colour purification. Colour purification occurs because the refractive index of the light conducting medium is slightly different for each wavelength of light present, forcing a splitting and recombination process of the white light within. Moreover, the colour impurities are typically angle dependent, thus altering this angle by means of internal reflections as described herein, aids purification. The second functional zone is light control zone 21. At the junction of light mixing zone 18 and light control zone 21 , upper face 19 can be seen to angle down generally towards lower face 20 to form a light directing region 22. It should be appreciated, however, that either or even both of upper face 19 and lower face 20 could comprise light directing region 22 and so the descriptors 'upper face' and 'lower face' are not employed to indicate exactly how the waveguide will be oriented in use of from which face light will be ejected but rather are useful terms to relate to the particular embodiments shown in the figures.

The particular shape and/or angle of light directing region 22 in relation to the positioning of the LEDs 11 is crucial. Light emitted from LEDs 11 which is travelling substantially parallel to lower face 20, as seen in FIG 1 , will contact light directing region 22 at an angle greater than the critical angle with respect to the normal to the portion of the light directing region 22 where the light strikes. This means that substantially all such light rays will be internally reflected from the surface of light directing region 22 to be contained within waveguide 14.

The angle and length of light directing region 22 are also such that the distance light rays have to travel before they are likely to contact upper face 19 or lower face 20 is greatly reduced. For example, in the absence of light directing region 22 light rays emitted from LEDs 11 travelling substantially parallel to lower face 20 would travel to edge face 16, opposite their injection site, and be reflected back by reflective coating 17 before eventually having their path altered or diffused such that they can be ejected from waveguide 14. Light directing region 22 ensures that injected light is forced out of waveguide 14 much sooner by directing a large-portion of the injected light directly onto a reflective matrix 23 which then ejects the light out of apparatus 10. This acts as an internal lens focusing the light onto reflective matrix 23 and so increasing the light output and thereby provides the viewer with a greater perceived intensity of light for the same power output.

Light control zone 21 comprises reflective matrix 23 which will be formed on the portion of either upper face 19 or lower face 20 within the light control zone. In the embodiment shown in FIG 1 reflective matrix 23 is formed on the light directing region 22 of upper face 19. Reflective matrix 23 will typically comprise a pattern of symmetrical shapes which may be formed by etching onto a face of waveguide 14, painting, printing or the like. It is preferable that reflective matrix 23 be painted, printed or etched directly onto waveguide 14 rather than being a separate layer of tape or the like since this avoids a waveguide 14 to air interface and so maximises the amount of light actually reflecting back off reflective matrix 23. Reflective matrix 23 may be formed from a highly reflective paint which should reflect light without generating an image or shadow. To obtain broad frequency reflection the reflective matrix 23 should be white but if mono colour is required then the pattern can be printed in mono colour accordingly. In an alternative embodiment reflective matrix 23 is formed from a fluorescent paint or like material which can effectively provide a boost to the light emitted.

In the embodiment shown in FIG 1 light rays will be reflected from light directing region 22 due to both the angle of inclination of that region and also the presence of reflective matrix 23. The light rays will then impinge upon lower face 20 at an angle less than the critical angle to be substantially all ejected from lighting apparatus 10 towards a viewer. The effect achieved is to force light out of the waveguide 14 much sooner than would otherwise have occurred (i.e. light is ejected after a fewer number of reflections than with prior art devices) while diffusing the bright point source light of the LEDs 1 1 such that improved output is achieved while greatly reducing or removing the likelihood of bright spots being visible to the viewer. Ejecting light out of waveguide 14 sooner means less light is lost due to reflections/collisions with multiple surfaces which provides for a greater net output for the same input thereby providing high efficiency delivery of pleasing light.

FIG 2 is a representation of the path taken by three light rays through the waveguide shown in FIG 1 and gives some indication of the effect achieved by the combination of light directing region 22 and reflective matrix 23. For clarity the actual LEDs 1 1 emitting rays A, B and C are not shown but the light source is indicated as being adjacent an edge face rather than embedded within waveguide 14. Ray A enters waveguide 14 at a relatively sharp angle such that it is immediately ejected towards the viewer through lower face 20 in the light mixing zone 18. This path is taken only at wide initial angles and helps the light fitting to achieve good illumination at angles close to 90 degrees to the normal of the lamp, where reflective matrix 23 may otherwise lose efficiency.

Ray B enters waveguide 14 at an angle such that it contacts lower face 20 at an angle grater than the critical angle and so is reflected internally. It then reflects off light directing region 22 and reflective matrix 23 to either exit directly afterwards through lower face 20 or, as shown in FIG 2, undergoes a further set of reflections before its path is altered such that it contacts lower face 20 at an angle less than the critical angle to then escape waveguide 14. The likelihood of ray B contacting the reflective element increases with the number of reflections as the distance between lower face 20 and light directing region 22 decreases.

Ray C enters waveguide 14 parallel to lower face 20 and therefore contacts light directing region 22 before having contacted any other face of the waveguide. After striking the reflector element of reflective matrix 23 the light ray immediately escapes waveguide 14 through lower face 20.

When rays B and C are indicated as escaping waveguide 14 it will be noted that they are represented in FIG 2 by a cone of light. This is to represent the fact that the reflective portions of the reflective matrix, operatively, act as many small point light sources by reflecting the light for ejection in a non-image forming fashion. This effect takes light from the high brightness LEDs 1 and distributes it over a wider range of reflective area to then eject it without bright or hot spots being visible to the viewer.

FIG 3 is a plan and side view representation of two embodiments of LED arrangement. First LED arrangement 30 shows a plurality of LEDs 31 linearly disposed along an LED board 32 which may be or may be attached to a circuit board. The LEDs 31 in the embodiment shown are more or less square in nature and so may either be accommodated within a waveguide as shown in FIG 1 or may simply be in direct contact with one or more edge faces of the waveguide to inject light directly into the waveguide while minimising any air gap. LED board 32 may be flexible to accommodate its attachment to waveguides which have one or more curved or otherwise non- linear edge faces. LED board 32 should be made from a material to effectively transfer and dissipate heat from LEDs 31 to keep them as cool as possible and prevent loss of efficiency and/or failure. The boards may contain a large proportion of copper or other thermally conductive material, allowing fast heat transfer from LEDs 31 onto either a heat sink or the external housing of the lamp. The large area of the waveguide also aids i thermal dissipation.

Second LED arrangement 40 presents what can be viewed as two rows of offset LEDs 41 on an LED board 42 to thereby provide a greater number of LEDs 41 and hence a greater net light output into the associated waveguide. In this embodiment LEDs 41 have a curved outer surface and so are better accommodated within recesses or the like in the waveguide to ensure the air gap between LED 41 and waveguide is minimised. It will be appreciated that many other arrangements and shapes of LEDs are possible and would be acceptable for use in the present invention.

FIG 4 is a plan view and a cross sectional view of one embodiment of a waveguide 50. The embodiment of waveguide 50 shown has a curved, irregular edge face 51 while the remaining edge faces are linear. Irregular edge face 51 is coated with a reflective coating 52 which is only broken by a plurality of recesses 53 shaped to accommodate closely a number of correspondingly shaped LEDs (not shown). Light will enter waveguide 50 from recesses 53 and enter a light mixing zone 54 which is differentiated functionally from light control zone 55 by the broken line. The structural differences between the two zones 54 and 55 can be seen in the cross sectional view.

Waveguide 50 is seen to have upper face 56 and lower face 57 which, in light mixing zone 54 are parallel to one another. Upon entering light control zone 55, however, both upper face 56 and lower face 57 converge to thereby present first light directing region 58 and second light directing region 59. In this embodiment a reflective matrix (not shown in FIG 4) would be present on light directing region 59 since the reflective matrix should always be on the light directing region furthest away from the viewer to ensure light is ejected therefrom directly towards the viewer. FIG 4 indicates the viewer's eye 60 is adjacent first light directing region 58 and so, in this embodiment, the reflective matrix would be present on second light directing region 59 to aid in ejecting light out of waveguide 50 towards viewer's eye 60.

The presence of both first and second light directing regions 58 and

59, respectively, means that there is a much greater concentration of light being directed towards the reflective matrix, increasing the amount of light striking it. This is useful when the physical dimensions of the lamp are such that the sloping of one face (being the light directing region) is too small to make a substantial difference to the amount of light ejected. The presence of both first and second light directing regions 58 and 59, respectively, narrows the volume of waveguide 50 available to the light and so increases the likelihood of injected light rays encountering one of these regions to thereby result in either direct ejection or initial reflection to contact the reflective matrix, followed by subsequent ejection of light.

The use of two sloping surfaces, as shown in FIG 4, may be desirable where it is impractical to regulate the light redirection by one surface alone, for example where. the surface is to be physically long, as the increased angular deviation causes the light to escape over effectively a shorter path, as described. This embodiment may eject light too quickly, i.e. after only a single reflection from the reflective matrix bearing light directing region 59, and so will be used mainly in lighting apparatus which by necessity are physically long.

FIGs 5 through to 8 show different embodiments of a lighting apparatus 70 which vary mainly in the shape adopted for the waveguide and so the numbering will be maintained throughout the description of these embodiments as the numerals relate to like parts. Although present on all, for the sake of convenience a reflective coating has not been shown on any of the edge faces in FIGs 5 to 8.

FIG 5 is a plan view and a cross sectional view of one embodiment of a lighting apparatus 70. A plurality of LEDs 71 are disposed along an LED board 72 and located such that they are in operative contact with an edge face 73 of waveguide 74. LEDs 71 have a square or rectangular outer shape such that they form close contact with the flat surface of edge face 73 and so do not need to be embedded within waveguide 74.

Light rays injected into waveguide 74 by LEDs 71 will be mixed and colour purified in a light mixing zone 75 before entering light control zone 76. The cross sectional view shows upper face 77 and lower face 78 of waveguide 74. Upper face 77 comprises an angled light directing region 79 which, unlike the embodiment shown in FIG 1 , is found opposite a reflective matrix 80 which is formed on lower face 78. In this embodiment, light entering the light control zone 76, substantially at ninety degrees to edge face 73 adjacent LEDs 71 , will encounter light directing region 79 at an angle greater than the critical angle and so will be internally reflected and, particularly, directed towards reflective matrix 80. This, will result in the reflecting portions of reflective matrix 80 reflecting the light back up, in the manner of a large number of point light sources, towards light directing region 79 at an angle less than the critical angle to be deliberately ejected out of lighting apparatus 70 towards the viewer.

Waveguide 74 is also seen to comprise projection 81 which is provided, and must be small enough (typically a couple of centimetres), so that the light doesn't lose on intensity in this region. There is no physical reason why projection 81 could not be a point, but for convenient manufacturing reasons may take the form as shown in FIG 5.

FIG 6 is a plan view and a cross sectional view of an alternative embodiment of a lighting apparatus 70. Similarly to FIG 5, LEDs 71 are disposed along LED board 72 adjacent edge face 73. However, in the embodiment shown in FIG 6 this situation is repeated on the directly opposite edge face 73 to lend lighting apparatus 70, symmetry. Provision of a dual array of LEDs 71 clearly provides for a greater input , and therefore output, of light into waveguide 74.

Dual light mixing and control zones 75 and 76, respectively, are also present. Again, the cross sectional view shows upper face 77 and lower face 78 of waveguide 74 with upper face 77 comprising, in this embodiment, two light directing regions 79. Light directing regions 79 are angled in a complimentary manner to formed a wide V shape with a flattened apex. Lower face 78 is provided with a reflective matrix 80 which extends the length of both light directing regions 79. As mentioned above it will be appreciated that the embodiment shown in FIG 6 has symmetry and the particular arrangement of elements means that the light from each array of LEDs 71 is dealt with substantially as described before but the viewer sees only the combined effect.

Light directing regions 79 end at and are joined by a connecting region 81. Since this embodiment of lighting apparatus 70 has a greater capacity to inject, control, diffuse and direct light compared with those embodiments having only one similarly sized light directing region 79 it is preferred to reserve such embodiments for high light output applications.

FIG 7 is a plan view and a cross sectional view of a further alternative embodiment of a lighting apparatus 70. This embodiment is similar in structure to that shown in FIG 6 with the same elements including LEDs 71 , LED board 72, edge faces 73 of waveguide 74 and light mixing and control zones 75 and 76, respectively. The major difference in the embodiment shown in FIG 7 is that there are four light directing regions 79 to form a square presentation angling in to connecting region 81. A reflective matrix 80 is present in the form of a square matrix corresponding to all of light directing regions 79 and is formed on lower face 78.

This embodiment clearly has a greater light input and controlling capacity, yet again, than that in FIG 6. Light injected in from the plurality of LEDs 71 , which now correspond to all edge faces 73 of waveguide 74, will contact one of light directing regions 79, be directed down onto reflective matrix 80 and then substantially ejected through upper face 77 either immediately or following a small number of reflections. Light is free to pass from one edge face 73 beyond one light directing region 79 to then be ejected through another light directing region 79. In this manner, light rays are far more likely to encounter one of light directing regions 79 after a relatively short path length from their injection point to then be directed onto reflective matrix and ejected from lighting apparatus 70.

FIG 8 is a plan view and a cross sectional view of yet a further alternative embodiment of a lighting apparatus 70. The various elements are as previously described for FIGs 5 to 7 with the clear difference in FIG 8 being that waveguide 74 is substantially circular in shape. This results in one large inverted cone-shaped light directing region 79 which sits in alignment with a circular reflective matrix 80 (circular refers to the area reflective matrix 80 covers and not necessarily to the actual shape of the reflective portions of reflective matrix 80). The mode of action of lighting apparatus 70, as seen in FIG 8, is substantially as described previously.

FIG 9 is a representation of one embodiment of a reflector matrix 90 which is printed or otherwise formed onto a waveguide 91. The light mixing zone 92 of waveguide 91 , where light is injected, is free of reflective matrix 90 but then, upon entering light control zone 93, it is seen to begin.

Reflective matrix 90 comprises a repeating pattern of printed reflective portions 94 adjacent non-printed non-reflective portions 95. In FIG 9 the repeating pattern is a square pattern but is not limited thereto. Any form of geometric or even non-geometric pattern may suffice so long as the reflecting portions 94 can alter the trajectory of incident light rays such that they are more likely to be ejected from waveguide 91. It is the action of reflecting portions 94 which makes them appear to the viewer as the actual light source. Given that there are so many reflecting portions 94 this results in the bright, highly focused LED light sources having their intensity evenly transmitted across all of reflecting portions 94 so that ejected light appears even and diffused.

It can be seen from FIG 9 that the surface area of each of the internal reflecting portions 94 increases evenly, at the expense of the non-reflective portions, on moving further away from the light source and light mixing zone 92. Each new row (i.e. reflecting portion 94 of the row) of the repeating reflective matrix 90 pattern is bigger from the preceding row by an equal amount. This results in a greater effective area for the ejection of light rays in the region of waveguide 91 furthest from the light source which, of course, is where the density of light rays would be lowest. Thus the light ejection power increase due to increasing area of reflecting portions 94 compensates for the roughly r² power loss of the light intensity as a function of distance from the light source.

FIG 10 is a plan view and a cross sectional view of one embodiment of a lighting apparatus 100 with housing 111 and power source 120. Lighting apparatus 100 is fully assembled and so waveguide 110 is held within housing 111 which also encloses the LED light sources which, accordingly, cannot be seen by the observer. Waveguide 110, as discussed previously, comprises a light mixing zone 112 near the light injection point and a light control zone 113 which contains reflective matrix 114. A cover or housing 115 extends over the surface of lighting apparatus 100 which will be viewed by the observer and may be continuous around waveguide 110 and provides a reflective layer 119 on its lower surface.

In the cross sectional view upper face 116 and lower face 117 of waveguide 110 can be seen. Upper face 116 comprises an angled region which is a light directing region 118, as discussed previously, while the reflective matrix 114 is formed on lower face 117. Beneath lower face 117 is a reflective layer 119, which may be an integral part of housing 115 which is a layer of white paint or printing or a mirror coated layer which will reflect any light escaping through lower face 117 back into waveguide 110. It is preferable that any air gap between lower face 117 and reflective layer 119 is minimised. A power source 120 is also present which may be connected to mains power or may use or be capable of using batteries when mains power is not available.

In operation, the LEDs inject light into waveguide 110 and it is mixed and colour purified in light mixing zone 112 before passing into light control zone 113. A large proportion of the LED light will be travelling more or less parallel to upper face 116 and lowerface 117, as they sit in light mixing zone 112, and will therefore contact the angled light directing region 118 of upper face 116. Light directing region 118 is angled such that substantially all of the light incident on its surface, which has not previously collided with any other surface of waveguide 110, will contact it at an angle greater than the critical angle, with respect to the normal, and so will be totally internally reflected.

The effect of light directing region 118 is therefore two-fold. Firstly, the mean path length of light rays injected into waveguide 110 is greatly reduced because light directing region 1 8 ensures they encounter a surface from which they are reflected and subsequently ejected at the earliest point rather than relying on a potentially large number of reflections around a standard waveguide to achieve the same end. Secondly, light directing region 118 could be described, functionally, as acting as an internal lens in that it scatters a greater proportion of light directly onto reflective matrix 114 which results in its subsequent ejection. This means that a greater proportion of light is ejected sooner compared with prior art approaches where the light is encouraged to mix and undergo multiple internal reflections. The light output of the present lighting apparatus 100 is thus significantly increased and provides an efficient way of harnessing the high power of the LED light sources.

FIG 11 is a side view of two lighting apparatus when stacked together. It is an advantageous and unique feature of the present invention that, should a higher intensity of light output be required then the design of each light apparatus is such that they can be operatively associated or stacked together to achieve a greater light output than could be attained by attempting to associate more LEDs with one lighting apparatus alone.

FIG 11 shows a stacked lighting apparatus 200 which comprises a first lighting apparatus 210 and a second lighting apparatus 220. Both first and second lighting apparatus 210 and 220, respectively, are as previously described herein with light directing region 211 and lower face comprising reflective matrix 212 apparent on first lighting apparatus 210 and light directing region 221 and lower face comprising reflective matrix 222 on second lighting apparatus 220. The LEDs are powered by power source 230 which can represent mains power or a connection thereto as well as a battery power supply.

Although the mode of operation of first and second lighting apparatus 210 and 220, respectively, are as previously described there are some modifications that should be made as a result of the stacking feature. Firstly, reflecting matrices 212 and 222 should be offset so that, when viewed from above, they would present one large reflecting area. Each reflecting portion from reflecting matrix 222 reflects light in a cone or like spread but the greatest intensity would be directly above the reflecting portion. For this reason it is best that there is not a reflecting portion located directly above this one as a greater proportion of light may be reflected back into second lighting apparatus 220.

In another embodiment or in addition to the modification of matrix alignment, reflecting matrix 212 may be formed from a still at least partially reflective but translucent material. This means it provides less of a barrier to light trying to enter first lighting apparatus 210 from second lighting apparatus 220, below. Any light escaping first lighting apparatus 210 would then be reflected back from reflective matrix 222 of second lighting apparatus 220. This feature is particularly useful when more than 2 lamps are stacked together and altering the reflective matrix pattern such as to minimise light impacting on lower matrix surfaces. It allows light boosting well beyond the effect achieved by use of two lamps, separately.

A single lighting apparatus will have a reflective layer located below the reflective matrix to ensure that light does not escape but, clearly, when stacking lighting apparatus this would present a barrier to light transmission from one apparatus to the next and so this element will not be present on any but the lighting apparatus closest the power source i.e. the furthest away from the viewer.

Although FIG 11 shows two light apparatus stacked one on top of the other, it will be appreciated that 3, 4, 5 or even more may be associated together to achieve an ever increasing light output.

The present invention provides a lighting apparatus which allows the use of LEDs while addressing their disadvantages such as visible hot spots and uneven light colour and/or intensity. It effectively harnesses the power of LEDs and also maximises the output of light rays (for the same LED input) obtained therefrom by use of an angled light directing region and reflective matrix to shorten the mean light path length before ejection and helps intensify the light in the ejection zone.

The design of the lighting apparatus described herein is such that it can be scaled up to sizes which were previously unworkable in terms of achieving satisfactory visually pleasing light. The ability to arrange a large number of LEDs around all edge faces of the waveguide in combination with the effectiveness of the light ejected from all areas of the light directing region/reflective matrix means loss of light with distance isn't a problem.

Further, although the embodiments described in the figures all show a linearly angled light directing region this is not necessarily the only acceptable form. The inventors have found that curved designs and even hyperbolic or parabolic shapes are also effective. Such shapes may, of course, require additional modification to the pattern of the reflective matrix to avoid the generation of light hot spots due to the curvature of the light directing region.

A further advantage of the present invention is that it is entirely recyclable. Unlike fluorescent lighting which has the problem of mercury and rare earth components, the present lighting apparatus provides a simple collection of non-toxic and fully recyclable components and therefore presents genuine advantages in terms of environmental impact.

The principles disclosed herein also lend themselves to applicability in a range of lighting apparatus of different shapes and sizes, including those which were not previously satisfactorily achievable. For example, a lighting apparatus may be produced with no reflective backing behind the reflective matrix thereby allowing a light source to have a spillage angle greater than 180 deg. This could result in a spherical light waveguide. Various embodiments combining a number of the features described herein may be envisaged. For example, one lighting apparatus may take the form of a small disc approximately 150mm diameter. No cut outs within the waveguide are needed as the curvature of the edge face is sufficient. A second embodiment may comprise a narrow and long waveguide, with the LEDs disposed along one side. Due to limited space, this one may not have cut outs within the waveguide and so flat faced LEDs would be used. In a third embodiment the waveguide is relatively wide (300mm) with LEDs disposed along both sides.

This embodiment may have wavy edge faces (as seen in FIG 4), as the LEDs are further apart. Finally, a fourth embodiment may take the form of a

600x600mm waveguide and may have all edge faces wavy to accommodate a relatively large number of LEDs.

The various features and embodiments of the present invention, referred to in individual sections above apply, as appropriate, to other sections, mutatis mutandis. Consequently features specified in one section may be combined with features specified in other sections as appropriate.

Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. It will therefore be appreciated by those of skill in the art that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention.

v.

Claims

1. A lighting apparatus comprising:

(b) a light source to emit light rays into the waveguide;

(c) a reflective matrix adjacent one of the upper face or the lower face of the waveguide; and

2. The lighting apparatus of claim 1 wherein the light directing region is angled with respect to the light source such that the majority of light rays emitted from the light source which directly contact the light directing region will make contact at an angle greater than the critical angle.

3. The lighting apparatus of claim 2 wherein substantially all of the light rays emitted from the light source which directly contact the light directing region will make contact at an angle greater than the critical angle.

4. The lighting apparatus of any one of the preceding claims wherein the substantially internally reflected light is reflected directly from the light directing region onto the reflective, matrix.

5. The lighting apparatus of any one of the preceding claims wherein the face of the waveguide adjacent the reflective matrix is opposite the face of the waveguide comprising the light directing region.

6. The lighting apparatus of claim 1 wherein the light source is one or more LEDs.

7. The lighting apparatus of claim 6 wherein the one or more LEDs are disposed adjacent an edge face of the waveguide.

8. The lighting apparatus of claim 7 wherein each LED is located within a complimentary recess within the edge face of the waveguide.

9. The lighting apparatus of claim 6 wherein the light directing region is shaped such that the majority of light rays emitted from the one or more LEDs and travelling substantially parallel to an edge face joining the upper face and lower face of the waveguide will contact the light directing region before contacting another face of the waveguide.

10. . The lighting apparatus of any one of the preceding claims wherein the reflective matrix is adjacent the lower face of the waveguide and the light directing region is formed on the upper face of the waveguide, the upper face^' being the light emitting face.

11. The lighting apparatus of claim 10 wherein the light directing region is angled towards the lower face of the waveguide such that the majority of light emitted from the one or more LEDs and travelling parallel to the lower face will contact the light directing region and be substantially internally reflected towards the reflective matrix.

12. The lighting apparatus of any one of the preceding claims wherein the reflective matrix is formed on the lower face of the waveguide.

13. The lighting apparatus of claim 12 wherein the reflective matrix is painted or printed onto the lower face of the waveguide. .

14. The lighting apparatus of any one of the preceding claims wherein the reflective matrix comprises a fluorescent material.

15. The lighting apparatus of any one of the preceding claims wherein the reflective matrix comprises an alternating pattern of reflective portions adjacent non-reflective portions.

16. The lighting apparatus of claim 15 wherein the size of the reflective portions relative to the non-reflective portions increases with increasing distance from the light source.

17. The lighting apparatus of claim 15 wherein the lighting apparatus further comprises a reflective layer beneath the reflective matrix to reflect light rays which exit through the non-reflective portions back into the waveguide.

18. The lighting apparatus of any one of the preceding claims wherein each edge face of the waveguide is provided with an internally reflective surface.

19. The lighting apparatus of claim 18 wherein the internally reflective surface is a mirror coating.

20. The lighting apparatus of any one of the preceding claims wherein the lighting apparatus further comprises a housing at least partially enclosing the waveguide.

21. The lighting apparatus of any one of the preceding claims wherein two or more of the lighting apparatus are operatively associated to increase the total amount of light ejected towards the viewer.

22. The lighting apparatus of claim 21 wherein the lower surface of one lighting apparatus is placed adjacent the upper surface of another lighting apparatus.

23. The lighting apparatus of claim 22 wherein the reflective and non- reflective portions of respective reflective matrices are not in alignment.

24. A lighting apparatus comprising:

(b) a light source associated with an edge face of the waveguide; and

wherein, the light directing face is angled with respect to the light source such that light rays emitted therefrom and directly incident upon the light directing face are substantially internally reflected onto the reflective matrix face to thereby eject light from the waveguide after a minimal number of internal reflections.

25. The lighting apparatus of claim 24 according to any one of claim 1 to claim 23.

26. A lighting system comprising a first lighting apparatus stacked on top of a second lighting apparatus wherein each of the first and second lighting apparatus comprise an optically transparent waveguide comprising a light directing face, a reflective matrix face and one or more edge faces, a light source associated with an edge face, and wherein the light directing face is angled with respect to the light source such that substantially all of the light rays emitted therefrom and directly incident upon the light directing face makes contact at an angle greater than the critical angle.