WO2006137018A1

WO2006137018A1 - Illumination system and switching device

Info

Publication number: WO2006137018A1
Application number: PCT/IB2006/051989
Authority: WO
Inventors: Martijn Riemeijer; Wouter P. Kaandorp; Berend J. W. Ter Weeme
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2005-06-23
Filing date: 2006-06-20
Publication date: 2006-12-28
Also published as: TW200707492A

Abstract

An illumination system a plurality of light sources (R5B ;G, A) comprising first and second groups of light sources of distinct primary colors. Each of the groups of light sources is operable in a first or in a second mode of operation switched by a switching device. A disc (10) is provided with at least a first circular contact path (1) connected to one of the current-supply conductors of each group of light sources. The disc is provided with at least a first and at least a second electrical contact pad (21R,21R';21B,21B') connected to the other current-supply conductor of each group of light sources, respectively. First and second contact means (25R,25B) register with the first circular contact path. The contact means are movable with respect to the disc. A particular group of light sources is in the second mode of operation when the corresponding contact means establishes electrical contact between the first circular contact path and the corresponding electrical contact pad.

Description

Illumination system and switching device

FIELD OF THE INVENTION

The invention relates to an illumination system comprising a plurality of light sources operable in a first ("ON") or in a second ("OFF") mode of operation and a switching device for selectively switching between the first and the second mode of operation. The invention also relates to a switching device for use in such an illumination system.

BACKGROUND OF THE INVENTION

Such illumination systems are known per se. They are used, inter alia, for general lighting purposes, such as spotlights, flood lights and for large-area direct-view light emitting panels such as applied, for instance, in signage, contour lighting, and billboards. Additional applications include so-called ambiance-light applications to adapt ambient light conditions to the mood of a person or persons in a room or to the mood of a TV show or movie shown on a screen at home. The illumination systems are further used as task light and as a combined tail, brake and indicator vehicle rear light.

Generally, such illumination systems comprise a multiplicity of light sources, for instance light-emitting diodes (LEDs). LEDs can be light sources of distinct primary colors, such as, for example the well-known red (R), green (G), or blue (B) light emitters. In addition, the light emitter can have, for example, amber (A), magenta or cyan as primary color. These primary colors may be either generated directly by the light-emitting-diode chip, or may be generated by a phosphor upon irradiance with light of shorter wavelength (e.g. green, blue or UV-light) from the light-emitting-diode chip. In the latter case, also the use of mixed colors or white light is possible as one of the primary colors. Generally, the light emitted by the individual light sources is mixed in air or in a transparent element(s) of the optical system to obtain a uniform distribution of the light while eliminating the correlation of the light emitted by the illumination system to a specific light source.

US Patent US-A 5,214,255 discloses a switching device for a multi-filament electric lamp. The filaments of the electric lamp are electrically connected to arcuate contact surfaces arranged in a circle. A conductive bar is arranged to rotate about an axis of the circular arrangement of contact surfaces. The ends of the conductive bar contact the contact surfaces, and an electric power supply is electrically connected to the center portion of the conductive bar. Current flows into the center portion of the conductive bar an out both ends and through the filaments of the electric lamp in patterns determined by actuation of a pull- chain to operate the lamp in "low", "medium", and "high" states. With the conductive bar in a further, pull-chain determined position, the lamp is "off'.

A drawback of the known illumination system is that the switching arrangement in the electric lamp is relatively complicated.

SUMMARY OF THE INVENTION

The invention has for its object to eliminate the above disadvantage wholly or partly. According to the invention, this object is achieved by an illumination system comprising: a plurality of light sources comprising a first group comprising at least one light source of a first primary color and a second group comprising at least one second light source of a second primary color, the first and the second primary colors being distinct from each other, each of the groups of light sources being provided with a first and a second current-supply conductor for providing electrical connection between the groups of light sources and a current source, each of the groups of light sources being operable in a first ("ON") or in a second ("OFF") mode of operation, the illumination system further comprising a switching device for selectively switching between the first and the second mode of operation, the switching device comprising: a disc arranged around an axis, at least a first circular contact path being provided on the disc, the first circular contact path being electrically connected to the second current-supply conductor of the first group of light sources and to the first current-supply conductor of the second group of light sources, at least a first electrical contact pad and at least a second electrical contact pad being arranged in a pre-determined manner on the disc, the first electrical contact pad being electrically connected to the first current-supply conductor of the first group of light sources and the second electrical contact pad being electrically connected to the second current- supply conductor of the second group of light sources, a first contact means and a second contact means being provided, the first and second contact means being movable with respect to the disc, the first and second contact means registering with the first circular contact path, a particular group of light sources being in the second ("OFF") mode of operation when the corresponding contact means establishes electrical contact between the first circular contact path and the corresponding electrical contact pad.

The illumination system according to the invention is simple, relatively easy to manufacture, relatively easy to use and, in addition, relatively cheap. In addition, a plurality of switching positions can be provided.

In the illumination system according to the invention, the light sources of distinct primary colors are arranged in groups. The (groups of) light sources are in a parallel arrangement connected to the current source via the respective current-supply conductors connected to the first circular contact path and to the respective electrical contact pads on the disc, respectively. Each of the contact means corresponding to a group of light sources is movable with respect to the disc and is in contact means with the first circular contact path. Normally, the (groups of) light sources are in the first mode of operation ("ON"). Only when due to movement of the contact means relative to the disc, a particular contact means is in a position to establish electrical contact between the first circular contact path and the electrical contact pad corresponding to the particular group of light sources, that particular group of light sources is short-circuited and is switched to the second ("OFF") mode of operation. As the illumination system is driven by a current source, the switching "OFF" of a particular group of light sources does not influence the light emission of the other group(s) of light sources.

Depending on the arrangement of the first and second electrical contact pads on the disc and the arrangement and position of the respective contact means relative to the disc, each of the (groups of) light sources can be switched from the first ("ON") to the second ("OFF") mode of operation independently. For a situation with a first group of light sources of a first primary color and a second group of light sources with a second primary color, at least three different switching states can be realized in which at least one of the groups of light sources is "ON": all light sources are "ON", the first group of light sources is "ON" and the second group of light sources is "OFF", and the first group of light sources is "OFF" and the second group of light sources is "ON". In this manner, an illumination system capable of emitting a variety of colors can be realized. Switching between the different color states is realized by changing the positions of the respective contact means relative to the disc.

Preferably, the first and second electrical contact pads are provided at opposing sides of the first circular contact path. Such arrangement facilitates establishing electrical contact by the contact means between the first circular contact path and the electrical contact pad corresponding to a particular (group of) light sources.

Preferably, the first circular contact path is a closed-circular contact path. Such arrangement facilitates full switching of each of the groups of light sources. In addition, such arrangement of the first circular contact path simplifies manufacture of the contact paths on the disc.

Establishing electrical contact between the first circular contact path and the electrical contact pad corresponding to a particular group of light sources is preferably done by mechanical means. To this end, a preferred embodiment of the illumination system according to the invention is characterized in that each of the contact means is a sliding contact means, the first and second contact means being in sliding contact with the first circular contact path. Preferably, such mechanical sliding contact means comprises a metallic spring in constant mechanical and electrical contact with the first circular contact path and, depending on the position of the sliding contact means with respect to the disc, such sliding contact means is in a position to establish electrical contact between the first circular contact path and the electrical contact pad corresponding to the particular group of light sources. In an alternative, preferred embodiment of the illumination system according to the invention is characterized in that each of the contact means is an optical sensor.

The switching capacity of the illumination system according to the invention is improved if the illumination system comprises more than two groups of light sources. To this end, a preferred embodiment of the illumination system according to the invention is characterized in that the plurality of light sources further comprises a third group comprising at least one light source of a third primary color, the three primary colors being distinct from each other, at least a second circular contact path being provided on the disc, the second circular contact path being electrically connected to the second current-supply conductor of the third group of light sources, at least a third electrical contact pad being arranged in a predetermined manner on the disc, the third electrical contact pad being electrically connected to the first current-supply conductor of the third group of light sources, a third contact means movable with respect to the disc registering with the second circular contact path, a particular group of light sources being in the second ("OFF") mode of operation when the corresponding contact means establishes electrical contact between the second circular contact path and the corresponding electrical contact pad.

Depending on the arrangement of the first, second and third electrical contact pads on the disc and the arrangement and position of the respective contact means relative to the disc, each of the (groups of) light sources can be switched from the first ("ON") to the second ("OFF") mode of operation independently. For a situation with a first group of light sources of a first primary color, a second group of light sources with a second primary color, and a third group of light sources with a third primary color at least seven different switching states can be realized in which at least one of the groups of light sources is "ON". In this manner, an illumination system capable of emitting a variety of colors can be realized. Switching between the different color states is realized by changing the positions of the respective contact means relative to the disc.

Preferably, the second circular contact path is a closed-circular contact path. Such arrangement facilitates full switching of each of the groups of light sources. In addition, such arrangement of the second circular contact path simplifies manufacture of the contact paths on the disc.

The switching capacity of the illumination system according to the invention is further improved if the illumination system comprises more than three groups of light sources. To this end, a preferred embodiment of the illumination system according to the invention is characterized in that the plurality of light sources further comprises a fourth group comprising at least one light source of a fourth primary color, the four primary colors being distinct from each other, the second circular contact path being electrically connected to the first current-supply conductor of the fourth group of light sources, at least a fourth electrical contact pad being arranged in a pre-determined manner on the disc, the fourth electrical contact pad being electrically connected to the second current-supply conductor of the fourth group of light sources, a fourth contact means movable with respect to the disc being provided registering with the second circular contact path, a particular group of light sources being in the second ("OFF") mode of operation when the corresponding contact means establishes electrical contact between the second circular contact path and the corresponding electrical contact pad.

Preferably, the third and fourth electrical contact pads are provided at opposing sides of the second closed-circular contact path. Such arrangement facilitates establishing electrical contact by the contact means between the second circular contact path and the electrical contact pad corresponding to a particular (group of) light sources.

A iavorable embodiment of the illumination system according to the invention is characterized in that the first, second, third and fourth contact means are mechanically coupled to each other. Movement of all contact means is coupled. Depending on the arrangement of the first, second, third and fourth electrical contact pads on the disc and the arrangement and position of the respective contact means relative to the disc, each of the (groups of) light sources can be switched from the first ("ON") to the second ("OFF") mode of operation independently. For a situation with a first group of light sources of a first primary color, a second group of light sources with a second primary color, a third group of light sources with a third primary color, and a fourth group of light sources with a fourth primary color, at least fifteen different switching states can be realized in which at least one of the groups of light sources is "ON". In this manner, an illumination system capable of emitting a variety of colors can be realized. Switching between the different color states is realized by changing the positions of the respective contact means relative to the disc.

The color of the light emitted by the groups can be tempered by adding some white light sources. To this end, a preferred embodiment of the illumination system according to the invention is characterized in that the illumination system further comprises a fifth group comprising at least one light source (W) of a fifth primary color, the fifth primary color being substantially white.

The invention also relates to a switching device for use in such an illumination system. Such switching device comprises a disc provided with at least a first circular contact path and with at least a first and at least a second electrical contact pad arranged in a predetermined manner. At least a first and a second contact means movable with respect to the disc are provided registering with the first circular contact path.

Preferably, the disc of the switching device is further provided with a second circular contact path and with at least a third electrical contact pad arranged in a predetermined manner. A third contact means movable with respect to the disc is provided registering with the second circular contact path. Preferably, the disc of the switching device is further provided with at least a fourth electrical contact pad arranged in a pre-determined manner. A fourth contact means movable with respect to the disc is provided registering with the second circular contact path.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. In the drawings:

Figure IA is a perspective view of an embodiment of the illumination system according to the invention;

Figure IB is a side view of the embodiment of the illumination system as shown in Figure IA;

Figure 2 is an embodiment of switching device for use in an illumination system according to the invention; Figure 3 is a schematics of the switching of a switching device for use in an illumination system according to the invention, and

Figure 4 is a C.I.E. 1931 color triangle diagram with a number of color points generated by an embodiment of an illumination system according to the invention.

The Figures are purely diagrammatic and not drawn to scale. Notably, some dimensions are shown in a strongly exaggerated form for the sake of clarity. Similar components in the Figures are denoted as much as possible by the same reference numerals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure IA shows schematically a perspective view of an embodiment of the illumination system according to the invention. Figure IB shows schematically a side view of the embodiment of the illumination system as shown in Figure IA. The illumination system comprises a plurality of light sources R, G, B, A, for example light-emitting diodes (LEDs), mounted in a housing 6 with an axis 9. LEDs can be light sources of distinct primary colors, such as in the example of Figure IA and IB, the well-known red R, green G, blue B and amber A LEDs. Alternatively, the light emitter can have, for example, cyan as primary color. The primary colors may be either generated directly by the LED chip, or may be generated by a phosphor upon irradiance with light from the LED chip. In the latter case, also mixed colors or white light can act as one of the primary colors of the illumination system. Preferably, the LEDs are mounted on a (metal-core) printed circuit board (PCB). LEDs have a light emission pattern which deviates from other light sources. In general, a LED emits light in a half hemispherical part of space: all the light at the location of the LED chip is directed away from the face of the LED chip; no light is directed "backwards".

In general, LEDs have relatively high source brightness. Heat generated by the LEDs can be readily dissipated by heat conduction via the PCB. In a favorable embodiment of the illumination system, the (metal-core) printed circuit board is in contact with the housing 6 of the illumination system via a heat-conducting connection.

In the example of Figure IA and IB the illumination system is embodied as a complete system with contact pins 7 A, 7B in a well-known manner for connection to a power outlet (not shown in Figure IA and IB). In the example of Figure IB the illumination system is provided with a rotary dome 8 arranged around axis 9 and connected to the housing 6 such that the rotary dome 8 can be rotated manually with respect to the housing 6. Preferably, the rotary dome 8 mixes the light emitted by the light sources R, G, B, A. In addition, the rotary dome 8 functions as a switching device (not shown in Figure IA and IB) for selectively switching groups of light sources between a first and a second mode of operation (see the description below). Preferably, the rotary dome 8 also mixes the light emitted by the groups of light sources R, G, B, A.

Figure 2 schematically shows an embodiment of switching device for use in an illumination system according to the invention. The illumination system as shown in Figure 2 comprises a plurality of light sources R, B; G, A comprising a first group comprising at least one light source R (only one red LED of the group of LEDs is shown in Figure 2) of a first primary color and a second group comprising at least one second light source B (only one blue LED of the group of LEDs is shown in Figure 2)of a second primary color, the first and the second primary colors being distinct from each other. Each of the groups of light sources R, B is provided with a first 1 IR; 1 IB and a second 12R; 12B current-supply conductor for providing electrical connection between the groups of light sources and a current source 3. Each of the groups of light sources R, B is operable in a first ("ON") or in a second ("OFF") mode of operation. The illumination system as shown in Figure 2 further comprises a switching device for selectively switching between the first ("ON") and the second ("OFF") mode of operation. The switching device comprises a disc 10 arranged around an axis 9, the axis 9 being perpendicular to the plane of drawing. The disc 10 is provided with at least a first circular contact path 1 electrically connected to the second current-supply conductor 12R of the first group of light sources R and to the first current-supply conductor 1 IB of the second group of light sources B. In addition, the disc 10 is provided in a pre-determined manner with at least a first electrical contact pad 2 IR, 2 IR' and at least a second electrical contact pad 2 IB, 21B'. The first electrical contact pad 2 IR, 2 IR' is electrically connected to the first current-supply conductor 1 IR of the first group of light sources R and the second electrical contact pad 2 IB, 2 IB' is electrically connected to the second current-supply conductor 12B of the second group of light sources B.

In the embodiment of Figure 2, the first and second electrical contact pads 2 IR, 2 IR'; 2 IB, 2 IB' are provided at opposing sides of the first circular contact path 1. In addition, the first circular contact path 1 is a closed-circular contact path.

In the example of Figure 2, a first contact means 25R and a second contact means 25B are provided just above the disc 10. The first and second contact means 25R; 25B are movable with respect to the disc 10. The arrangement of the first and second contact means 25R; 25B with respect to the disc is such that the first and second contact means 25R; 25B register with the first circular contact path 1. In the embodiment shown in Figure IA and IB, the first and second contact means 25R; 25B are coupled to the rotary dome 8 arranged around axis 9. In the embodiment shown in Figure IA and IB, the rotary dome 8 can be rotated manually with respect to the housing 6 thereby shifting first and second contact means 25R; 25B to other position with respect to the disc 10.

Normally, a particular group of light sources R; B is in the first ("ON") mode of operation when the corresponding contact means 25R; 25B is in such a position that no electrical contact is made between the first circular contact path 1 and the corresponding electrical contact pad 21 R, 21R'; 21B, 21B'. However, the particular group of light sources R; B switches to the second ("OFF") mode of operation when the corresponding contact means 25R; 25B establishes electrical contact between the first circular contact path 1 and the corresponding electrical contact pad 21 R, 21R'; 21B, 21B'. Only when due to movement of the contact means 25R; 25B relative to the disc 10, a particular contact means 25R; 25B is in a position to establish electrical contact between the first circular contact path 1 and the electrical contact pad 21 R, 21R'; 21B, 21B' corresponding to the particular group of light sources, that particular group of light sources is short-circuited and is switched to the second ("OFF") mode of operation. As the illumination system is driven by a current source, the switching "OFF" of a particular group of light sources does not influence the light emission of the other group(s) of light sources.

In the example of Figure 2, the plurality of light sources R, B; G, A further comprises a third group comprising at least one light source G of a third primary color, the three primary colors being distinct from each other. To this end the disc 10 is provided with at least a second circular contact path 2 electrically connected to the second current-supply conductor 12G of the third group of light sources G. At least a third electrical contact pad 22G is arranged in a pre-determined manner on the disc 10. The third electrical contact pad 22G is electrically connected to the first current-supply conductor 1 IG of the third group of light sources G. In addition, a third contact means 25G movable with respect to the disc 10 registers with the second circular contact path 2.

In the example of Figure 2, the plurality of light sources R, B; G, A further comprises a fourth group comprising at least one light source A of a fourth primary color, the four primary colors being distinct from each other. The second circular contact path 2 is electrically connected to the first current-supply conductor 12A of the fourth group of light sources A. At least a fourth electrical contact pad 22A, 22A' is arranged in a pre-determined manner on the disc 10. The fourth electrical contact pad 22 A, 22 A' is electrically connected to the second current-supply conductor HA of the fourth group of light sources A. In addition, a fourth contact means 25 A movable with respect to the disc 10 is provided registering with the second circular contact path 2.

Normally, a particular group of light sources G; A is in the first ("ON") mode of operation when the corresponding contact means 25G; 25 A is in such a position that no electrical contact is made between the second circular contact path 2 and the corresponding electrical contact pad 22G; 22 A, 22 A'. However, the particular group of light sources G; A switches to the second ("OFF") mode of operation when the corresponding contact means 25G; 25A establishes electrical contact between the second circular contact path 2 and the corresponding electrical contact pad 22G; 22 A, 22 A'.

In the embodiment of Figure 2, the third and fourth electrical contact pads 22G; 22A, 22A' are provided at opposing sides of the second circular contact path 2. In addition, the second circular contact path 2 is a closed-circular contact path.

Preferably, the first, second, third and fourth contact means 25R, 25B, 25G, 25 A are mechanically coupled to each other. Preferably, movement of the rotary dome 8 is coupled to a simultaneous movement of the first, second, third and fourth contact means 25R, 25B, 25G, 25A. In a favorable embodiment of the illumination system, each of the contact means 25R, 25B, 25G, 25A is embodied as a sliding contact means, the first and second contact means 25R, 25B being in sliding contact with the first circular contact path 1, the third and fourth contact means 25G, 25A being in sliding contact with the second circular contact path 2. In an alternative embodiment, each of the contact means is embodied as an optical sensor.

Figure 3 shows schematics of the switching of a switching device for use in an illumination system according to the invention. Very schematically it is shown that the rotary dome 8 is mechanically coupled to the contact means 25R, 25B, 25G, 25A for selectively switching groups of light sources R, B; G, A. Four additional diodes Dl, D2, D3, D4 are shown to complete the connection to the current source 3.

To temper the colors emitted by the illumination system a fifth group comprising at least one light source W of a fifth primary color, the fifth primary color being substantially white. Preferably, these white light sources are be switched on and off independently of the movement of the contact means 25R, 25B, 25G, 25 A.

In a favorable embodiment of the illumination system according to the invention the arrangement of the first, second, third and fourth electrical contact pad 2 IR, 2 IR'; 2 IB, 21B'; 22G; 22 A, 22 A' on the disc 10 is such to enable at least fifteen different switching positions in which at least one of the groups of light sources is in the first ("ON") mode of operation. To this end, Figure 4 shows a so-called C.I.E. 1931 color triangle diagram with a number of color points generated by an embodiment of an illumination system according to the invention. The 1931 C.I.E. color triangle is well known to those skilled in the art. A suitable choice of the color co-ordinates of the individual groups of light sources and of the ratio between the various colors enables the illumination system to generate light having a great variety of color temperatures and color points. For example, the color point of the light emitted by the illumination system can be chosen to be on the so-called blackbody locus.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. An illumination system comprising, a plurality of light sources (R, B; G, A) comprising a first group comprising at least one light source (R) of a first primary color and a second group comprising at least one second light source (B) of a second primary color, the first and the second primary colors being distinct from each other, each of the groups of light sources (R, B) being provided with a first (HR; HB) and a second (12R; 12B) current-supply conductor for providing electrical connection between the groups of light sources (R, B) and a current source (3), each of the groups of light sources (R, B) being operable in a first (ON) or in a second (OFF) mode of operation, the illumination system further comprising a switching device for selectively switching between the first and the second mode of operation, the switching device comprising: a disc (10) arranged around an axis (9), at least a first circular contact path (1) being provided on the disc (10), the first circular contact path (1) being electrically connected to the second current-supply conductor (12R) of the first group of light sources (R) and to the first current-supply conductor (1 IB) of the second group of light sources (B), at least a first electrical contact pad (2 IR, 2 IR') and at least a second electrical contact pad (21B, 21B') being arranged in a pre-determined manner on the disc (10), the first electrical contact pad (21R, 21R') being electrically connected to the first current-supply conductor (HR) of the first group of light sources (R) and the second electrical contact pad (21B, 21B') being electrically connected to the second current-supply conductor (12B) of the second group of light sources (B), a first contact means (25R) and a second contact means (25B) being provided, the first and second contact means (25R; 25B) being movable with respect to the disc (10), the first and second contact means (25R; 25B) registering with the first circular contact path

(1), a particular group of light sources (R; B) being in the second (OFF) mode of operation when the corresponding contact means (25R; 25B) establishes electrical contact between the first circular contact path (1) and the corresponding electrical contact pad (2 IR, 21R'; 21B, 21B').

2. An illumination system as claimed in claim 1, wherein the first and second electrical contact pads (21R, 21R'; 21B, 21B') are provided at opposing sides of the first circular contact path (1).

3. An illumination system as claimed in claim 1 or 2, wherein the first circular contact path (1) is a closed-circular contact path.

4. An illumination system as claimed in claim 1 or 2, wherein the plurality of light sources (R, B; G, A) further comprises a third group comprising at least one light source (G) of a third primary color, the three primary colors being distinct from each other, at least a second circular contact path (2) being provided on the disc (10), the second circular contact path (2) being electrically connected to the second current-supply conductor (12G) of the third group of light sources (G), at least a third electrical contact pad (22G) being arranged in a pre-determined manner on the disc (10), the third electrical contact pad (22G) being electrically connected to the first current-supply conductor (HG) of the third group of light sources (G), a third contact means (25G) movable with respect to the disc (10) registering with the second circular contact path (2), a particular group of light sources (G) being in the second (OFF) mode of operation when the corresponding contact means (25G) establishes electrical contact between the second circular contact path (2) and the corresponding electrical contact pad (22G).

5. An illumination system as claimed in claim 4, wherein the second circular contact path (2) is a closed-circular contact path.

6. An illumination system as claimed in claim 4, wherein the plurality of light sources (R, B; G, A) further comprises a fourth group comprising at least one light source (A) of a fourth primary color, the four primary colors being distinct from each other, the second circular contact path (2) being electrically connected to the first current-supply conductor (12A) of the fourth group of light sources (A), at least a fourth electrical contact pad (22A, 22A') being arranged in a predetermined manner on the disc (10), the fourth electrical contact pad (22A, 22 A') being electrically connected to the second current-supply conductor (HA) of the fourth group of light sources (A), a fourth contact means (25A) movable with respect to the disc (10) being provided registering with the second circular contact path (2), a particular group of light sources (A) being in the second (OFF) mode of operation when the corresponding contact means (25A) establishes electrical contact between the second circular contact path (2) and the corresponding electrical contact pad (22A, 22A').

7. An illumination system as claimed in claim 6, wherein the third and fourth electrical contact pads (22G; 22A, 22A') are provided at opposing sides of the second closed- circular contact path (2).

8. An illumination system as claimed in claim 6, wherein the first, second, third and fourth contact means (25R, 25B, 25G, 25A) are mechanically coupled to each other.

9. An illumination system as claimed in claim 6, wherein the arrangement of the first, second, third and fourth electrical contact pad (21R, 21R'; 21B, 21B'; 22G; 22A, 22A') on the disc (10) is such to enable at least fifteen different switching positions in which at least one of the groups of light sources (R, B; G, A) is in the first (ON) mode of operation.

10. An illumination system as claimed in claim 6, wherein the illumination system further comprises a fifth group comprising at least one light source (W) of a fifth primary color, the fifth primary color being substantially white.

11. An illumination system as claimed in claim 6, wherein each of the contact means (25R, 25B, 25G, 25A) is a sliding contact means, the first and second contact means (25R, 25B) being in sliding contact with the first circular contact path (1), the third and fourth contact means (25G, 25A) being in sliding contact with the second circular contact path (2).

12. An illumination system as claimed in claim 6, wherein each of the contact means (25R, 25B, 25G, 25A) is an optical sensor.

13. A switching device for use in an illumination system as claimed in claim 1 or 2.