GB2263983A - Means for producing lighting effects - Google Patents

Abstract

Lighting effects are produced by controlled disruption of the internal reflected light in a plurality of superposed laminar light guides 18, 19, 20. Methods for producing the areas of disruption include mechanical and chemical treatments and the addition of material to the surface of the or each light guide. By illuminating the light guides 18, 19, 20 with different colours full-colour shaded images can be produced, suitable for use as eg a display or menu board. <IMAGE>

Description

WEANS FOR PRODUCING LIGHTING EFFECTS This invention relates to means for producing lighting effects hy controlled disruption of the internal reflection of light within a light guide.

Total or substantial internal reflection is widely used for lighting in various forms. Flexible fibre optics are used in surgical and decorative lighting applications as well as in telecommunications.

Interrupted internal reflection within substantially flat sheets is used in a variety of edge lighting equipment, to produce a simple informative sign, such as for a fire exit, or to produce a diffuse light output to illuminate an area evenly.

With these existing techniques it is difficult to produce a detailed picture or other decorative effect.

Fibre optics are awkward to arrange to form an image being both bulky and expensive, while edge lit lights have limitations on the colour and image detail that can be produced.

According to the present invention, means for producing lighting effects comprises two or more laminar light guides arranged in superimposed relationship, with each light guide having at least one area on a surface in which the internal reflection is disrupted, and illuminating means arranged to illuminate at least one edge of each light guide causing light to be emitted from the area of disrupted internal reflection.

This arrangement produces images defined by the areas of disrupted internal reflection, and which have an appearance of depth generated by different portions of the image being in different planes. Alternatively the different portions of the image may be generated in substantially the same plane, but on different light guides. In this way more detail and/or more complicated effects can be generated.

The extent to which the internal reflection is interrupted within an area of the light guide may be constant or alternatively it may be varied to produce differing intensities of light emitted for different parts of the image. One or both surfaces of a guide may be provided with areas of disruption.

The areas of disruption in the internal reflection of the light guide may be formed by physically altering the surface of the light guide, by methods such as mechanical abrading, chemical etching, scratching, pock marking or the like.

Alternatively the areas of disruption may be formed by the application to and retention of a material on the surface of the light guide. Preferably the material has a refractive index which differs from that of the light guide material. Inks, films, resins lacquers, paints or the like are all suitable materials. The material applied may be removable, and easily applied in the desired pattern. The materials may be applied by means such as screen printing, air brushing, spraying, painting or writing. Alternatively the materials may be cut to the desired pattern and applied.

The materials applied are preferably transparent or translucent, but need not be to cause the disruption required.

The areas of disruption on the light guides, or even one single area, may be generated by any one or a combination of such methods.

Each light guide may be illuminated by the same colour light, the light emitted by each disrupted area being the combination of the light colour applied to the light guide together (where applicable) with the colour of the material applied to or causing the area of disruption. Thus if white light is applied to a light guide having a red area of disruption the light emitted will be red.

Alternatively, adjacent light guides may be illuminated by different colour light, so that the areas of disruption on each light guide are illuminated by light of the colour applied to that light guide. One or more light guides may each be illuminated by a different colour at each of two or more of its edges.

The image created will vary in colour with the viewing angle of the viewer to the plane of the image.

The light colour may be obtained by light sources of different colours. Conveniently however the light colour is obtained by applying a coloured transparent layer of the required colour to the illuminated edge.

The layer conveniently is a lacquer. This reduces the light source requirement from one for each individual edge or colour to be illuminated, to simply one for each set of edges.

Two or more coloured layers may be applied to the edge of a light guide in longitudinal sections. By placing appropriate light sources close to the points where the colour change-over occurs the section of the light guide extending perpendicular to that section is illuminated in that colour with a blended section comprising the two colours in a wedge-like area. The extent of this blended area depends on the extent to which the light source extends on either side of the cross-over point.

By applying different coloured light to different edges of the same light guide the colour light emitted by an area of disruption will be observed to vary with the angle of the observer to the light guide.

Both methods of causing disruption allow multi-coloured composite images to be formed. Where areas of disruption on two or more light guides, or surfaces of the same light guide, overlap then the area of that overlapping disrupted area will be illuminated by the resulting combination of the colours illuminating the respective disrupted area which are superimposed. In this manner colour shades can be produced. By producing the areas in a manner slightly out of register the impression of depth can be increased by creating a shadow effect.

By illuminating parts of the light guides sequentially an impression of movement can be achieved, using a slightly different image of a part, or the whole of the picture, on different light guides. When not illuminated the area of disruption on a light guide is barely visible.

To increase the intensity of the image as a whole the edges of each light guide which are not illuminated are advantageously provided with a reflective coating which reflects the light back into the light guide and eventually out through the disrupted areas. The same reflective coating or an opaque one may also be used to prevent illumination of an edge when this is not required.

Alternatively the intensity of the image can be controlled and varied by the intensity of the applied light source, the image density and the thickness of the light guide. The thicker the light guide the more intense the image produced.

The light guides are preferably glass or plastics sheets, and may be flat, curved or moulded to any given shape.

A lighting effect of this kind is suitable for a number of uses, for instance, pictures, menu boards, advertising signs (including ones where a construction in accordance with the invention actually forms the window), nightlights or other forms of display for presenting information where a multicoloured and/or three-dimensional effect may be beneficial.

Some embodiments of the present invention are illustrated, by way of example only, in the accompanying drawings in which: Figure 1 is a partially sectioned view of a light picture assembly with three light guides; Figure 2 is an end view section of Figure 1; Figure 3 is a side sectional view of an embodiment of the invention used as a menu board or other presentation display; Figure 4 shows the embodiment of Figure 3 in use; Figure 5 is a schematic plan view of a light guide demonstrating the variation in image colour with viewing angle of a light guide illuminated with a different colour from each side; and Figure 6 is a view of a light guide illuminated by two different colours on one edge.

Figure 1 shows a means for producing lighting effects in the form of a light picture assembly having three transparent plastics sheets, in this example acrylic, which act as light guides 2, 4, 7, mounted within a framework 1. The three light guides are arranged in a superimposed relationship with a small spacing between them. The front light guide 2 has an area in the form of a circle 3 on its rear face within which the internal reflection of light is disrupted.

The middle light guide 4 has a similar circular area 5 on its front face, with a further similar area 6 on the front face of the rear light guide 7. Each light guide has a layer of transparent lacquer on its upper edge.

The front light guide 2 has a layer of blue lacquer 8, the middle light guide 4 a layer of green lacquer 9, and the rear light guide 7 a layer of red lacquer 10.

As can be seen from Figures 1 and 2 the framework 1 containing the light guides 2, 4, 7 has a light box 11 for accommodating illuminating means in the form of conventional fluorescent tubes 12 around the edges of the light guides 2, 4, 7. Each light box 11 is separated from the others by a series of baffles 13 which prevent light from one light box undesirably illuminating another.

The spacing between the light guides is also sealed, around their periphery, with suitable means, such as tape, 14 to prevent light shining directly between the light guides 2, 4, 7 from the illuminating means. The framework 1 is closed at the rear by a back panel 15.

The three circular areas of disruption to the internal reflection of light, in Figure 1, all overlap each other slightly. When the three light guides are edge-illuminated using a white light illuminating means 12 in the top light box 11, the light emitted from the area of disruption 3, 5, 6 in each light guide 2, 4, 7 is of the same colour as the lacquer 8, 9, 10 applied to the top of the particular light guide. The circular area on the front light guide is, therefore, illuminated in blue, the middle one in green and the rear one in red. Where the circular areas overlap then the image view will be coloured by the combination of the colours involved. In this way the blue/green overlap will appear cyan, the blue/red overlap will appear magenta, the green/red overlap will appear yellow and the red/green/blue overlap at the centre will appear substantially white.Other combinations of coloured lacquers applied to edges with overlapping areas of disruption will be similarly illuminated in the resultant shade.

By varying the extent of the disruption to any one area of each of the three light guides in Figure 1 the amount of red, green and blue light emitted at that point in the image can be controlled and hence any colour desired obtained, so that a full-colour picture is possible.

The extent of the disruption and hence the intensity of light emitted can be varied in a large number of ways, for instance by varying the amount of abrasion or etching applied to an area, by applying materials of different colour densities or thicknesses or by varying the thickness of the light guide involved.

In a modification of Figure 1, an additional sheet can be placed close to the rear surface of the rear light guide 7, 18 to provide a backdrop. The backdrop may be coloured, and also serves to prevent any detrimental reflection of light back through the picture. In a further alternative, not shown, both the backdrop and back panel 15 may be omitted, so that the image can be viewed from both sides, if appropriate.

Figure 3 shows such a modification of Figure 1 suitable for use as a menu board or any such situation where information is to be displayed. Corresponding reference numerals have been applied to corresponding parts. The assembly 16 of Figure 3 consists of a framework 1 which encloses the edges of the various components to form a single unit. The framework 1 abuts a back panel 15, provided with a bar 17 for supporting decorative header panels 18, 19. A write-on panel 20 is provided in front of the decorative header panels 18, 19. All three panels, 18, 19, 20 act as light guides.

The lighting unit 21 is provided at the top edge of the assembly 1 and comprises a support frame 22 which carries the lighting means 23, in the form of a fluorescent tube, a reflector 24, and controls 26. The lighting unit 21 is enclosed by a casing 25, of UPVC, which covers the tube 23 and controls 26 provided on the support frame 22. The casing 25 is provided with a reflective coating on its internal surfaces.

Ventilation holes 27, 28 are provided in the back panel 15 and casing 21 respectively.

The decorative header panels 18, 19 are designed to remain in the unit, while the write-on panel 20 is designed to be easily removable and replaceable as it is invariably susceptible to wear and tear over time.

As shown in Figure 3 the light guides are placed in contact with one another, without the spacing indicated in Figure 1. In this way the image portions are brought much closer to each other. This reduces the depth of the image and also reduces any parallax which may occur between different portions of the image. In such a modification there is obviously no need for the provision of the sealing means 14, as no light can enter between the light guides when they are in planar contact. However, image masking 29 may still be provided to avoid any seepage of light from the other guide means.

Figure 4 shows a view of the entire apparatus, the upper portion of which was shown in Figure 3, in use as a free standing display. The assembly is of course suitable for wall mounting, hanging or any other form of display.

In Figure 4, the lighting unit 21 is provided at the top of the assembly with the write-on panel 20 extending down the front of the assembly. In the upper portion, the decorative header panels 18, 19 are provided behind the write-on panel 20. The lower limit of the decorative header panels 18, 19 is shown by dotted line 30. The whole apparatus is supported by a pivotally mounted leg 31.

In use the decorative header panels 18, 19 are provided with the permanent features of the display, such as the name of the establishment, split into red, green and blue elements with the resulting images each being applied to a light guide surface.

It is possible to apply all three images to a single surface of a single light guide, but the resulting illumination is poor, especially in the parts of the light guide furthest from the light source. In practice, therefore, the split images are applied to separate faces. However, where one image is only present in very limited amounts it may conveniently share a light guide, with a more prominent image, without undue detriment. The split images are applied to the light guide surfaces using a screen printing technique. Stencils and spraying or air brushing have also been successfully used, as well as coloured self-adhesive films, or films of the type which attach due to electrostatics or surface tension, all of which may be computer-profiled.

The write-on panel provided on the front on the display is designed to receive the information which varies with time, such as a menu. The write-on panel is provided with permanent borders. The information is written onto the write-on panel and removed as required. Chinagraph pencils, wax based crayons, dry wipe markers and in particular fluorescent dry wipe markers have all been found to be suitable.

While these materials are all more suitable for quick application and removal there is no reason why the above mentioned techniques applied to the decorative panels, cannot be used for the write-on panel and vice-versa.

The permanent display features on the decorative header panels are only present in the upper portion in Figure 4, but in an alternative they may extend over the entire board, down one side or in any other arrangement as desired for the application.

It is also envisaged that the sealing means 14, may be omitted even when a spacing is present between the light guides. In this way possibly desirable effects may be obtained by light shining between the light guides.

It should be appreciated that a fully enclosing framework 1 may not be required. The framework 1 is simply necessary to retain the light guides in the desired arrangement and to accommodate the illuminating means 21. The framework 1 may for example be limited to a small proportion of one or more sets of edges, leaving any number free.

Free edges such as these may be provided with a reflective coating, described in more detail below.

Alternatively they may be left uncoated to emit light of the colour or colours illuminating the respective light guide or an additional coloured layer may be provided on the edge to modify the light emitted.

It will be appreciated that, although a full-colour picture using three light guides is desirable, there are circumstances in which only two light guides may be necessary, each being illuminated by a different colour. Further, it is also possible to produce single colour pictures using two or more light guides, and these will give an appearance of depth generated by different portions of the image being in different planes. In a further modification, the proportion of light emitted from a light guide through the disrupted areas is increased by coating the non-illuminated edges with a reflective coating. Such a coating can also prevent a light guide being illuminated at an unsecured edge while still enabling other edges to be illuminated from that light box.

While the areas of disruption may be generated on either face of a light guide a number of different effects have been noted, in some circumstances, where the face on which the area is generated is important.

For instance, the application of an opaque coloured medium to the back face of a light guide, (the face further from the viewer) will still cause light of the same colour as the area of disruption to be emitted. Application of the same medium to the front face of a light guide will be ineffective, only producing a dark area. The opaque material will reflect light, but not transmit it.

A similar effect occurs where light, medium and dark images are applied in ink. On the back face there is little difference in the image brightness formed.

However, when applied to the front the images have the graduated variation in brightness expected.

Further effects can be obtained by the modifications shown in Figures 5 and 6. By applying a different coloured lacquer to opposing edges of a light guide and illuminating both edges of the light guide the colour of the image will change with the angle to the light guide from which it is viewed. In Figure 5 blue lacquer is applied to the edge 33 and red lacquer is applied to the edge 34. When both edges are illuminated and the area of disruption 35 is viewed from position A then the image will appear magenta. As the observer's viewing position moves towards position B the image will become predominantly red in colour. If the viewer, however, moves towards position C then the image will become increasingly blue in colour.

If two or more lacquers of different colours are applied to longitudinal strips of a light guide edge, as illustrated in Figure 6, different areas of disruption on the same light guide can be illuminated in different colours. In Figure 6 green transparent lacquer is applied to section 36 of the light guide edge and orange transparent lacquer to section 37 with a boundary 38 between the two. By illuminating the edge using a small illuminating means such as G simple filament bulb 39 close to the boundary 38, the image of a leaf 40 is illuminated in green light and the image of a sun 41 is illuminated in orange. The area between the dotted lines 42 represents the approximate area over which any disruption present would be illuminated by a blend of orange and green light. It will be appreciated that the type of illuminating means used will vary with the effect and extent of illumination required. A light guide with a wide ranging area or areas of disruption may most suitably be illuminated along a large proportion of the light guide's edge, for instance by a fluorescent tube as in Figure 1. Where two or more colours are applied to one edge of a light guide a smaller light source may be needed to minimise the area of blending of the colours, defined by dotted lines 42 in Figure 6. Where more than two colours are used on one edge it may be necessary to provide additional baffles to separate the discrete light sources placed under each boundary, to prevent the light shining into an area illuminated by another discrete illuminating means and so causing undesirable blending.

It is also possible to create the effect of movement on a picture by illuminating light sources sequentially, to illuminate parts of the light guides in turn, these parts having different images which, therefore, appear sequentially.

While planar rectangular light guides have been described, it will be appreciated that other forms and shapes of guides can also be used as required. The only requirement of the light guide is that it is able to internally reflect a substantial proportion of the light to the area of disruption. As is known from fibre optics such forms can be very varied in shape.

While the means for producing lighting effects has been described in relation to light guides, and signs it will be appreciated that it can be applied to other items, such as advertising signs, nightlights and the like just as well.

Claims (19)

1. A means for producing lighting effects comprising two or more laminar light guides arranged in superimposed relationship with each light guide having at least one area on a surface in which the internal reflection is disrupted, and illuminating means arranged to illuminate at least one edge of each light guide causing light to be emitted from the area of disrupted internal reflection.

2. A means according to claim 1 in which at least one of the light guides is provided with an area of disrupted internal reflection on at least two of its surfaces.

3. A means according to claim 1 or claim 2 in which at least a portion of an area of disrupted internal reflection on at least one light guide surface is provided in a superimposed relationship with at least a portion of an area of disrupted internal reflection on at least one other surface of a light guide.

4. A means according to any preceding claim in which the extent of disruption to the internal reflection of a light guide varies within at least one area of disrupted internal reflection.

5. A means according to any preceding claim in which one or more areas of disrupted internal reflection are produced by mechanical treatment of one or more light guides.

6. A means according to any preceding claim in which one or more areas of disrupted internal reflection are produced by chemical treatment of one or more light guides.

7. A means according to any preceding claim in which one or more areas of disrupted internal reflection are produced by treatment including the addition of material to one or more light guides.

8. A means according to claim 7 in which the material is removable.

9. A means according to any one of claims 5 to 8 in which the treatment is applied to an area defined by a stencil, screen or mask.

10. A means according to any preceding claim in which the area of disrupted internal reflection is coloured.

11. A means according to any preceding claim in which the light entering a light guide is coloured.

12. A means according to any preceding claim in which coloured material is applied to one or more illuminated edges of one or more light guides.

13. A means according to any preceding claim in which at least one of the light guides is of plastic material.

14. A means according to any preceding claim in which reflective material is applied to one or more edges of one or more light guides.

15. A means according to any preceding claim in which the light entering two or more longitudinal portions of an edge of a light guide is of a different colour to that entering one or more of the other portions.

16. A means according to any preceding claim in which the light entering the opposing edges of a light guide is of different colours.

17. A means according to any preceding claim in which the areas of disrupted internal reflection on two or more light guide surfaces correspond to a split of a coloured image into three images, each image being that part formed by one of the primary colours.

18. A means according to claim 17 in which the three images are each provided on a separate surface of a light guide.

19. A means for producing lighting effects substantially as described herein with reference to and as illustrated in the accompanying drawings.