GB2405461A

GB2405461A - Lighting panel producing multi-coloured lighting effects

Info

Publication number: GB2405461A
Application number: GB0320356A
Authority: GB
Inventors: Paul Francis Mardon; Mark Leonard Gregory
Original assignee: Pulsar Light of Cambridge Ltd
Current assignee: Pulsar Light of Cambridge Ltd
Priority date: 2003-08-30
Filing date: 2003-08-30
Publication date: 2005-03-02
Anticipated expiration: 2023-08-30
Also published as: GB0320356D0; GB2405461B

Abstract

A lighting panel 10 is provided, the panel comprising a plurality of light sources 60, 62, 64, such as LED's, located at the panel's periphery and arranged to direct light 66, 68, 70 onto at least one reflecting surface 21 etc, of the panel to give the appearance of substantially uniform illumination there across. The light sources are arranged in clusters 50 to 59, each of two or more light sources 60, 62, 64, of differing colours, preferably red, blue and green, the spacing in between neighbouring clusters being greater than that between neighbouring sources in any of the clusters. Further disclosed is the orientation of one or all of the clusters so as to improve the effective mixing of the light and uniformity of the illumination.

Description

240546 1 Title: Lighting Panel

Field of the Invention

This invention relates to lighting panels, and in particular to lighting panels which include a number of light sources of two or more different colours to enable multi-coloured lighting effects to be achieved from a single panel.

Background to the Invention

Light emitting diodes (LEDs) are becoming increasingly popular choices as light sources for multi-coloured illumination devices. Typically, LEDs of the three primary colours (red, blue and green) are arranged in a suitable array in a lighting device and connected to a power supply and control device which controls the intensity of the light emitted by the LEDs of each colour. The devices can provide illumination in any one of the three primary colours and, by virtue of the mixing of the light emitted from the LEDs, in practically any other colour in the visible spectrum. In certain types of illumination panel, the LEDs are situated at the panel periphery and co- operate with a reflective surface at least part of which is in the region of the centre of the panel in order to provide reasonably effective mixing of the light emitted by the LEDs. Examples of such panels are shown in If the space between the LEDs is too large, effective mixing does not occur. As the result, a panel may require more LEDs than is strictly necessary, or even practicable, to enable the panel to produce uniform illumination at a desired intensity.

Thus, for example, a panel may require relatively few LEDs in order to provide the desired intensity of illumination, but will not achieve the desired uniformity or colour consistency if the LEDs are distributed around the panel periphery in a conventional configuration.

Summary of the Invention

According to the invention, there is provided a lighting panel comprising a plurality of light sources located at the panel's periphery and arranged to direct light onto at least one reflecting surface of the panel to give the appearance of substantially uniform illumination thereacross, wherein the light sources are arranged in clusters, each of two or more light sources of differing colours, the space in between neighbouring clusters being greater than that between neighbouring sources in any of the clusters.

It has been found that arranging the sources in clusters improves the consistency of light emitted by the panel, despite the fact that this configuration results in relatively large length of the panel periphery in which there are no light sources, i.e. between the clusters.

It is believed that improvement is the result of the more effective mixing of light from the members in a given cluster, and this outweighs any possible deterioration in performance resulting from the gaps between the clusters.

Preferably, each cluster is of three sources, each of a respective colour, preferably red, blue and green.

Preferably, the panel is polygonal, with at least one side of the polygon being provided with a plurality of clusters.

The panel may to advantage be rectangular with the clusters of sources arranged on all four sides of the rectangle.

Preferably, each source comprises a light emitting diode (LED), preferably of a single colour, and preferably contained within a respective plastics body.

Preferably, at least some of the clusters are so orientated as to point towards the gap between two other, neighbouring clusters.

This improves uniformity of illumination.

To that end each cluster of LEDs closest to the corner of the panel is preferably orientated at an acute angle to the side of the panel on which it is mounted, so that the centre beam of the pattern of light emitted by each LED passes through the region of the diagnonally opposite of the corner of the panel.

This "toeing in" of certain clusters has been found to improve the consistency of the light emitted across the face of the panel because it enables the clusters to be spaced from the panel corners, and hence to be more effectively distributed along the length of each side.

Preferably, each of the clusters, other than those closest to the corner is angled towards a portion of the opposite wall of the panel not occupied by another cluster. Thus, the lack of any light source is a gap between neighbouring clusters can be offset by the effect of a cluster on the opposite wall.

Preferably, the outer members of each cluster are orientated towards the middle member so that the central axes of the beams of light emitted by the LEDs converges, preferably at another side of the panel.

Preferably, the spacing between adjacent clusters is not more than ten times the spacing between neighbouring members in each cluster. For example, the spacing between adjacent clusters may be not more than 90mm, whilst that between neighbouring members in each cluster is not more than 9mm.

Conveniently, the sides of the panel are approximately 300mm long, so that the panel fills one quarter of the space in a standard ceiling grid.

Preferably, the reflector is in the shape of a pyramid with an apex at the centre of the panel and edges adjacent to the panel's periphery.

Brief Description of the Drawings

The invention will now be described, by way of example, with reference to the accompanying drawings which: Figure 1 is a cut-away plan view of a lighting panel in accordance with the invention, and Figure 2 is a cutaway side view of the panel with the reflector in place.

Detailed Description

Referring to Figure 2, a lighting panel 10 comprises an aluminium housing 12 having a back plate 13 and containing four elongate printed circuit boards, 14, 15, 16 and 17,and a reflector 18. The housing, when viewed in plan, is square, measuring 293mm x 293mm x 75rnm. Each circuit board is attached to the internal surface of the back plate 13 of the housing adjacent to and parallel with a respective side of the housing.

The reflector 18 is vacuum formed from white flocked styrene and is in the general shape of a pyramid with four radiussed corners. Thus the reflector has four reflective, planar central triangular faces each flanked by a pair of curved faces. The corner faces are referenced 21, 23, 25 and 27 in figure 1 whilst reference numerals 29, 21, 33 and 35 denote the central faces. The reflector is located against the internal surface of the back plate 13 and at the centre of the panel. The reflector has an apex 19 lying on a axis which is perpendicular to the plate 13 and runs through the centre of the plate 13, and hence the panel. The reflector in plan is in the shape of a square, having radiussed corners, each side of which is 161mm long and runs parallel to a respective adjacent side of panel. The reflector is 24mm high. Each face forms an angle of 17 with the back plate 13.

The front of the housing 12 is closed by a translucent element in the form of a 3mm thick opal acrylic diffusing plate 20, which is attached to the housing by suitable fasteners (not shown).

The lighting panel further comprises a socket with 24 V do, ground, and O - 10 V tic red, green and blue control signal terminals. The socket is attached to the lighting panel by flying leads. The 24 V tic, ground, and O - 10 V dc red, green and blue control signal terminals are electrically connected to the four printed circuit boards. The socket, which is not shown in Figure 2, enables the lighting panel to be connected to a lighting controller and power supply such as a ChromaZone_ made by Pulsar Light of Cambridge Limited.

Such a controller enables the LEDs to be controlled so that the effective intensity of light emitted by LEDs of any of the three colours may be continuously varied. The controller feeds a respective continuously variable drive current to each set of LEDs to power the LEDs. As well as being continuously variable, the drive currents are continuous, so that the LEDs, and hence the panel emit light which is flicker free.

Each of the opposing printed circuit boards 15 and 17 has mounted on it a respective row of nine LEDs, and each of the opposing circuit boards 14 and 16 has mounted on it a respective to row of six LEDs. Each row extends parallel to its board, and the LEDs are mounted on the circuit boards so that when the circuit boards are attached to the housing, the distance of the LEDs from the back plate 13 is approximately one third of the distance from the back plate 13 to the apex 19 of the reflector 18.

The LEDs on each of the boards 15 and 17 are arranged in three clusters, each of three respective LEDs, whilst those on the each of the boards 14 and 16 are arranged in two clusters, each also being of three respective LEDs. The clusters are denoted by reference numerals 50 - 59. The panel has a total of thirty LEDs, of which 10 are green LEDs, ten are red and ten blue. The three colours of LED are arranged in a repeating sequence so that each cluster has a red, a green and a blue LED. Thus, the cluster 50 has a blue LED 60, a red LED 62 and a green LED 64, this sequence (blue, red, green) being repeated in each of the other clusters.

The spacing between LEDs at each cluster is 9mm, whilst the distance between the closest LEDs on two neighbouring clusters (or the same side of the panel) is 90mm.

The LEDs are all at a non perpendicular angle to the circuit boards 14 17. In order to illustrate the orientations of the LEDs, Figure 2 shows the axis of each LED, and hence of the beam of light emitted by the LED. For example, the LED 60 has an axis 66, the axis of the LED 62 is referenced 68, whilst reference numeral 70 denotes the axis of the LED 64. As can be seen from Figure 2, the two side LEDs of each cluster are angled slightly towards the cluster's central LED so that the axes from that cluster converge at another side of the panel.

It can also be seen that the LEDs of the clusters closest to a corner of the panel, i.e. clusters 50, 52, 55 and 57, face towards the region of the diagonally opposite corner (at which there is a gap between neighbouring clusters) so that the respective axes converge on a region of the adjacent side lacking any cluster. Each of the remaining clusters is so angled that its axes converge on a region of the opposite side of the panel where there is no cluster.

It has been found that, by angling the clusters in this way, the uniformity of illumination of the panel is improved. In addition the close spacing of the LEDs in each cluster helps to ensure proper mixing of the light that they emit so that, for example, if the panel is supposed to be emitting white light, no coloured patches on the panel are perceived.

The magnitude of a O - 10 V do red control signal applied to the red control signal terminal of the socket is used to control the magnitude of a current that flows through the red LEDs. The green and blue LEDs are controlled in the same manner by O -10 V dc green and blue controls signals, respectively.

The lighting panel further comprises four strips 26, 28, 34 and 36 of translucent styrene, each strip being attached to a respective circuit board adjacent to the row of LEDs so as to be interposed between that row and the lens 20. The strips therefore diffuse light emitted in the direction of the diffusing lens 20 from the sides of the LEDs, which light would otherwise appear as a row of bright red, green and blue spots along the periphery of the lens 20.

In Figure 1, the lens 20 has been omitted to show the inside of the housing, and the strips 26, 28, 34, and 36 have also been partially cut away to reveal to reveal the LEDs.

In use, the LEDs of are controlled to emit light which is reflected and diffused by the reflector 18 and further diffused by the lens 20, or which passes through the diffusing strips 26, 28, 34 and 36 to the lens 20. The reflector 18, lens 20 and diffuser strips 26, 28, 34 and 36 cause that light to give the appearance of constant intensity illumination of the panel across the lens 20.

The perceived colour of that light will depend on the relative intensities of the red blue and green components emitted by the LEDs, so that by controlling the amount of light emitted by each colour group of LEDs it is possible to control the perceived colour of light emitted by the panel. That colour can be continuously varied by correspondingly varying the relative intensitities of any of the red, blue and green colour components emitted by the LEDs.

Claims

Claims 1. A lighting panel comprising a plurality of light sources located

at the panel's periphery and arranged to direct light onto at least one reflecting surface of the panel to give the appearance of substantially uniform illumination thereacross, wherein the light sources are arranged in clusters, each of two or more light sources of differing colours, the space in between neighbouring clusters being greater than that between neighbouring sources in any of the clusters.
2. A lighting panel according to claim 1, wherein each cluster is of three light sources, each of a respective colour.
3. A lighting panel according to claim 2, wherein each cluster has a red, blue and a green light source.
4. A lighting panel according to any preceding claim, wherein the panel is polygonal, with at least one side of the polygon being provided with a plurality of clusters.
5. A lighting panel according to claim 4, wherein the panel is rectangular with the clusters of sources arranged on all four sides of the rectangle.
6. A lighting panel according to any preceding claim, wherein each source comprises a light emitting diode (LED).
7. A lighting panel according to claim 6, wherein each LED is of a single colour.
8. A lighting panel according to claim 6 or 7, wherein each LED is contained within a respective plastics body.
9. A lighting panel according to any preceding claim, wherein at least some of the clusters are so orientated as to point towards the space between two other, neighbouring clusters.
10. A lighting panel according to claim 5 or any claim dependent therefrom, wherein each cluster closest to a corner of the panel is orientated at an acute angle to the side of the panel on which it is mounted, so that the centre beam of the pattern of light emitted by each cluster passes through the region of the diagonally opposite corner of the panel.
11. A lighting panel according to claim 10, wherein each of the clusters, other than those closest to the corners, is angled towards a portion of the opposite wall of the panel not occupied by another cluster.
12. A lighting panel according to any preceding claim, wherein the outer members of each cluster are orientated towards the middle member so that the central axes of the beams of light emitted by the sources converge.
13. A lighting panel according to claim 12, wherein the outer members of each cluster are orientated towards the middle member so that the central axes of the beams of light converge at another side of the panel.
14. A lighting panel according to any preceding claim, wherein the spacing between adjacent clusters is not more than ten times the spacing between neighbouring members in each cluster.
IS. A lighting panel according to claim 5 or any claim dependent therefrom, wherein the sides of the panel are approximately 300mm long.
16. A lighting panel according to any preceding claim, wherein the reflecting surface is in the shape of a pyramid with an apex at the centre of the panel and edges adjacent to the panel's periphery.
17. A lighting panel substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.