Abstract:
A lighting system comprises a plurality of adjacent light sources of different colors. Each light source has a wide angle beam in a first plane and a narrower angled beam in a substantial perpendicular second plane. As a result, efficient mixing of light is achieved in the first plane.

Description:
FIELD OF INVENTION 
     This invention relates to the mixing of a plurality of electronically controlled light sources which are filtered to produce specific colours and then mixed to make any one of a range of colours including, with appropriate filtering, any colour in the visual spectrum. 
     BACKGROUND OF THE INVENTION 
     Systems for mixing red, green and blue coloured light to produce other colours has long been used to produce colour television pictures. However, in the area of direct lighting the larger the light sources and high powers involved have made it difficult to produce beams of light with homogenous colour. This difficulty arises because of the relatively large size of light sources and the fact that a compromise has to be made between effective colour mixing and efficient beams of light. Colour mixing can be best achieved by diffusing the light whilst efficient beams of light are produced by focusing the light. 
     SUMMARY OF THE INVENTION 
     A preferred embodiment of the present invention overcomes these problems by creating a wide angle mixing beam in one plane of illumination whilst maintaining a narrow beam in a substantially perpendicular plane. Using such a system makes it possible to illuminate a surface with uniformly colored light of any colour in the spectrum using apparatus containing only three suitably filtered light sources. 
     A further preferred embodiment of the invention uses semi specular or linear prismatic reflectors combined with small viewing shields to minimize the colour mixing zone and obscure it from view. This allows lighting units embodying the invention to be mounted within low height ceiling voids thus greatly enhancing the number of applications to which they can be put. 
     In a further preferred embodiment the surface being illuminated has its base inclined towards the viewer. 
     Preferably, a single action user interface is incorporated which may be a rotary knob or a slider with a purpose made colour scale that defines a set number of colours or change cycles to enable the user to turn the knob or slide the slider to a given colour and that colour will appear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is defined in the appended claims to which reference should now be made. 
     A preferred embodiment of the invention will now be described in detail by way of example with reference to the accompanying drawings which: 
     FIGS. 1 and 2 show schematic block diagrams of systems embodying the invention; 
     FIG. 3 is a schematic plan view of a lighting unit embodying the invention; 
     FIG. 4 is a side view of a lighting unit for use at the top of a wall to be illuminated; 
     FIG. 5 is a front view of a similar unit. 
     FIGS. 6A through 6F show a variety of mounting arrangements for the lighting unit; and 
     FIGS. 7 and 8 show plan and side views of an embodiment of the invention to be used behind e.g., a picture hung on the wall. 
    
    
     DETAILED DESCRIPTION 
     The schematic diagram of FIG. 1 shows a lighting unit  2  containing three light sources. A red source  4 , a green source  6 , and a blue source  8 . Each of these is connected to a voltage transformer device  10  which supplies voltage to operate each of the light sources. The human interface  12  with a rotary knob  14  supplies control signals to a power controller  16  which in turn supplies power to the voltage transformers  10  in proportions dependent upon the position of the rotary knob  14 . The human interface  12  is able to supply control signals to supply power to the voltage transformers  10  and thus to the light sources  4 ,  6 ,  8  in desired proportions so that any desired colour can be obtained. 
     Alternatively in FIG. 2, the schematic diagram shows a lighting unit  2  containing three light sources, as above, which are connected to a three channel combined dimmer/transformer  15  which supplies power to operate each of the light sources. The human interface  12  with a rotary knob  14  supplies control signals direct to the transformation device  15  which in turn supplies power to the lamps in proportion dependent upon the position of rotary knob  14 . The human interface  12  is able to supply control signals to supply power to the light sources  4 ,  6 ,  8  in desired proportions so that any desired colour can be obtained. 
     The light sources  4 ,  6  and  8  are positioned adjacent to each other and if a wider field of illumination is required then additional banks of red, green and blue light sources can be provided next to the lighting unit to give whatever width of illumination is required. 
     The lighting unit is illustrated in more detail in FIG.  3 . Each of the light sources  4 ,  6  and  8  comprises a lamp  20  positioned at the end of a reflector  22  which reflects light through colour filters red  5 , green  7 , and blue  9  from the lamp into a columniation tube  24 . The columniation tube focus the light into a substantially column-shaped beam. At the end of each columniation tube is a diffuser  26  which diffuses the light from the light sources and transmits it to a spread lens  28  which covers the whole of the front of the lighting unit. This comprises a set of parallel semi-specular or linear prismatic reflectors which are perpendicular to the plane of FIG.  3  and which cause the light to be diffused further up and down the plane of FIG. 3 as shown by the ray lines  30 . As seen in this figure, the light is thus diffused in the plane along which the axes of the light beams emitted from the columniation tubes  24  are oriented. Thus, the lighting unit produces a wide beam up and down the plane of FIG. 3 whilst maintaining a narrow beam in a plane perpendicular to FIG.  3 . This gives a very good mixing of the three colours and enables a surface such as a wall to be washed with the colour. This may be further enhanced by an auxiliary reflector of either semi-specular or prismatic material which further mixes the colour and turns the beam through an appropriate angle. 
     FIG. 4 shows a side view of a unit in which the lighting unit  2  of FIG. 3 can be mounted. The unit is thus perpendicular to its position in FIG.  3  and the wide beam of the unit is therefore perpendicular to the plane of FIG.  4 . 
     Usually unit  2  is mounted so that its primary direction of illumination is perpendicular to a wall  32 . A reflector  34  reflects the narrow beam of mixed light  36  downwards onto the wall  32 . A shield  38  is provided to stop a viewer seeing the mixing zone. 
     As can be seen, the wall  32  has its base inclined towards the viewing side. This improves the uniformity of illumination of the wall. Additionally, a mirror placed at the base of the wall will reflect the beam back up the wall and double the effect. 
     Alternatively, unit  2  can be mounted in the following positions relative to the wall with the noted different arrangements of lens and reflector and thus achieving the effects described as shown in FIGS. 6A to  6 F. 
     1. Mounted to ceiling at an appropriate angle. Unit shall have linear refractor and no reflector achieving a soft spread of light to the ceiling (FIG.  6 A). 
     2. Mounted in a ceiling at right angles to wall. Unit shall have a linear refractor lens and reflector  82  achieving a soft spread of coloured light on the wall (FIG.  6 B). 
     3. Mounted to the ceiling at right angles to the floor using linear refractor and no reflector achieving a soft spread of light on the wall. Effect can be doubled by return mirror  80  (FIG.  6 C). 
     4. Mounted from the ceiling at right angles to wall. Unit shall have a linear refractor lens and reflector  82  achieving a soft spread of coloured light on the wall. Effect can be doubled by return mirror  80  (FIG.  6 D). 
     5. Mounted in the floor at right angles to wall. Unit shall have a linear refractor lens and reflector  82  achieving a soft spread of coloured light on the wall. Effect can be doubled by ceiling mounted return mirror  80  (FIG.  6 E). 
     6. Mounted to the floor at right angles to ceiling, using linear refractor and no reflector achieving a soft spread of light on the wall and ceiling. Effect can be doubled by ceiling mounted return mirror  80  (FIG.  6 F). 
     7. (Not shown) Mounted to ceiling at right angles to floor. Unit shall have diffuser and calumniating lens in place of linear refractor achieving a clearly defined circular area of light. 
     A front view of the lighting unit  2  is shown in FIG.  5 . As can be seen the lighting unit is terminated by an end of unit cut-off shield  40  to prevent any light escaping to the side of the unit. The unit  2  is adjacent to a further unit  2  and additional units may be fixed adjacent to this according to the width of illumination required. 
     Using units as shown in FIG.  4  and FIG. 5 enables lighting units embodying the invention to be mounted within low height ceiling voids. 
     Alternatively, with a different arrangement of reflector and cut-off shields the unit could be mounted at the base of a wall shining light towards it. 
     The knob  14  on the human interface  12  is a single action knob and has a colour scale around it such that control sequences are sent to the power controller to send power to the voltage transformers  10  in desired proportions to ensure that a desired colour is produced by the lighting unit. This is intended to simplify the three separate controls which would usually be provided for the red, green and blue light sources. 
     The embodiment described above shows the use of red, green and blue light sources which will enable any colour in the spectrum to be produced with appropriate control signals. However, the invention could also be used with only two light sources, thus giving a narrower range of available colours. 
     The unit need not be used to produce only a wash of light. Using a suitable arrangement of lenses, the unit could be used to produce e.g., a focused beam of light. Such an application is shown in FIGS. 7 and 8 which shows a diagram of the invention arranged as a “Picture Light” as it is mounted behind e.g., a picture hung on the wall. 
     Lamps  50 , connected to transformers as described above, project a narrow beam of light through dichroic filters in red  52 , green  54 , and blue  56  this coloured light passes along tubes  58  and is diffused by diffuser  60  and spread by refractor  62 , the three beams mix into a single colour with the help of a diffusing dome  64  which reflects and mixes the diffused light. The groups of three lamps and optical system are repeated around the dome  64  to form a continuous ring. The assembly is hung a small distance from a surface with the course surface of the dome towards the surface, and illuminates the surface with whatever colour the user sets with the control system described above. This happens as light is reflected and mixed by the course surface of the dome onto the surface to be illuminated.