GB2517432A

GB2517432A - A light diffuser

Info

Publication number: GB2517432A
Application number: GB1314803.6A
Authority: GB
Inventors: Jitendra Makvana
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-08-19
Filing date: 2013-08-19
Publication date: 2015-02-25
Anticipated expiration: 2033-08-19
Also published as: GB2517432B; GB201314803D0

Abstract

A light diffuser unit suitable for use in the path of light emitted from a source to diffuse the emitted light comprises two major surfaces 301a, 301b for transmitting light from one side of the light diffuser unit to the other. A first major surface is convex and a second major surface is not co-planar with the first major surface. The diffuser unit is constructed of a light diffusing material. This lens-like structure creates a uniform distribution of light across the subject side of the diffuser unit.

Description

A LIGHT DIFFUSER

BACKGROUND

Technical Field of the Invention

The invention is in the field of lighting, particularly ornamental lighting and the provision of soft lighting. The invention also relates to screens capable of displaying images.

Description of Related Art

Lighting is generally provided by a point-source such as an LED or light bulb. This can be uncomfortable to view directly because when enough light is provided to illuminate a room or to be visible at a distance, then the point source is necessarily bright which can be distracting and harsh. Light diffusers are often used to spread this peak in light intensity and soften' the effect. Light diffusers generally comprise a single layer of optically transparent material, such as plastic or glass having a surface which has been roughened or ground to spread out or scatter light.

is Examples of diffusers include W02011041667, where an LED-based light source is combined with a curved diffuser to provide an omni-directional diffuse light source.

However, in such arrangements local bright spots can still exist which can be distracting for observers and also detract from the illusion that light is not being emitted from a point source. It is an object of the invention to provide a diffuser for a light source which overcomes these problems.

SUMMARY OF THE INVENTION

The present invention therefore provides a light diffuser unit suitable for use in the path of light emitted from a source to diffuse the emitted light, the light diffuser unit comprising two major surfaces for transmitting light from one side of the light diffuser unit to the other, wherein a first major surfaces is convex and a second major surface is not co-planar with the first major surface, and wherein the diffuser unit is constructed of a light diffusing material. This lens-like structure having light diffusing qualities creates a uniform distribution of light across the subject side of the diffuser unit.

The diffuser unit may be hollow, which allows the unit to be lightweight and relatively inexpensive to produce. The diffuser unit may be solid. The material of which the light diffuser unit is made may be inherently light diffusing, such as translucent white plastic or both of the major surfaces of the light diffuser may be roughened, rough surfaces being good at diffusing light. The second major surface may be planar, i.e. flat so that the diffuser unit is a piano-convex shape to provide a non-intrusive flat surface. Alternatively the second major surface may be convex, which can enhance the lensing effect of the unit.

The curvature of the convex surface or surfaces may be spherical or parabolic or a combination of both The periphery of the major surfaces may be circular or polygonal, e.g. square, rectangular or hexagonal.

The diffuser unit may be used in a lighting unit comprising at least one light source and a housing, the housing arranged to locate the diffuser unit in front of the at least one light source and to prevent light from escaping other than through the diffuser unit. Two or more light sources may be provided capable of producing light of different colours.

A display unit formed of a plurality of light cells may be provided, wherein each cell comprises a diffuser unit and at least one light source. Internal partitions may be provided to prevent light leaking between cells. Each light cell may include an individually controllable red light source, green light source and blue light source.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which: Figure la shows a point source of light.

Figure lb shows the light intensity profile from the point source of light of Figure la.

Figure 2a shows light from a point source being transmitted through a conventional single surface light diffuser.

Figure 2b shows the light intensity distribution from the arrangement shown in Figure 2a.

Figure 3a shows light from a point source being transmitted through a light diffuser in accordance with an embodiment of the invention.

Figure 3b shows the light intensity distribution from the arrangement shown in Figure 3a.

Figure 4a shows the components of a diffuser unit according to an embodiment of the invention.

Figure 4b shows an alternative embodiment of the diffuser unit having convex surfaces of parabolic shape.

Figure 4c shows an alternative embodiment of the diffuser unit having convex surfaces of spherical shape.

Figure 4d shows an alternative embodiment of the diffuser unit having convex surfaces of different shapes.

Figure 4e shows an alternative embodiment of the diffuser unit having one convex surface of parabolic shape and the other a planar surface.

Figure 5a shows an embodiment where the diffuser unit is hollow.

Figure 5b shows an embodiment where the diffuser unit is solid.

Figure 6 shows a lighting unit having a diffuser unit in accordance with an embodiment of the invention.

Figure 7a shows a diffuser unit with a point light source which is not aligned with the optical axis of the diffuser unit, and a corresponding light intensity profile at the outer surface of the diffuser unit.

Figure 7b shows a diffuser unit with multiple point light sources, and a corresponding light intensity profile at the outer surface of the diffuser unit.

Figure 7c shows a conventional diffuser with multiple light sources, and a corresponding light intensity profile at the outer surface of the diffuser.

Figure 8a shows a diffuser unit having a polygonal periphery, in a plan view and in a profile view.

Figure 8b shows a display panel of adjoining cells, each cell having a diffuser unit in accordance with an embodiment of the invention.

Figure 9 shows an LED having a diffuser unit in accordance with an embodiment of the invention at its tip.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Soft light is produced by a source which is large relative to the subject and casts diffuse shadows with soft edges. Point sources are by definition small with respect to their subject and therefore cast shadows with sharp edges, and are said to be hard light. The ideal diffuser is one which is large by comparison to the source and is diffuses the light from the source evenly across its surface so that the surface of the diffuser then becomes the apparent light source. This increases the size of the light source relative to a subject and produces soft light.

A point source of light 101 is shown in Figure la with emanating light rays and the corresponding intensity profile in relation to distance is shown in Figure lb. A clear spike in intensity can be seen in the centre of the distribution.

A conventional diffuser 201 is shown in Figure 2a located above a source of light 202 and the corresponding intensity profile of light across the diffuser is shown in Figure 2b. No real life diffuser can be perfect and there will always be preferential scattering of a light ray straight through the diffuser. Therefore the general level of intensity is elevated across the surface of the diffuser 201 but there is still an increased intensity at the centre of the diffuser 201 which manifests itself as a bright spot on the surface of the diffuser.

In an embodiment of the invention a double diffuser arrangement 301 is provided, as shown in Figure 3a, comprising two diffusing surfaces 301a, 301b. When the diffuser unit 301 is positioned between the light source 302 and the subject to be illuminated (not shown) the entire surface of the diffuser closest to the subject (herein after referred to as the outer diffuser unit surface 301 b) appears to glow as if it were the source of light itself, which to the observer is unexpected and can have a soothing effect. The corresponding light intensity profile when viewed from the subject side is shown in Figure 3b where it can be seen that the light intensity is even across the surface of the diffuser in comparison to the single diffuser of Figure 2a.

The diffuser unit 301 is formed of two diffusing surfaces 301 a, 301 b arranged so that light emanating from the light source 302 is incident on each surface consecutively, the first diffusing surface 301a (also referred to herein as the inner diffusing surface of the diffuser unit) and then the second diffusing surface 301b (the outer diffusing surface of the diffuser unit). In use a first diffusing surface 301a is arranged to be closer to the light source 302 than a second diffusing surface 301 b. Each of the two surfaces are curved to form a focussing lens-like structure. Each curved surface has an apex 403a, 403b as shown in Figure 4a and a rim 404a, b and the two surfaces are arranged so that their apexes are spaced further apart than their rims. In an embodiment the rims of each diffusing surface describe a circle and the rims of each diffusing surface are in contact. The apexes of the diffusing surfaces define an optical axis AA' for the diffuser unit 301.

The curvature of each diffusing surface may be parabolic, as shown in Figure 4b or spherical, as shown in Figure 4c. Alternatively, the first diffusing surface 301a may be of a different curvature to that of the second diffusing surface 301 b, as shown in Figure 4d. The second surface may not in fact be curved at all but planar, as shown in Figure 4e.

In an embodiment the diffusing surface is provided on a thin sheet of a suitable material such as plastic or glass, as shown in Figure 5a. The material may have an inherent diffusive quality, such as translucent white plastic. Alternatively a diffusive surface may be applied to the material by for example grinding or sand blasting glass or etching plastic to produce a roughened face. The diffuser unit then comprises two dished surfaces joined at their edges enclosing a void.

Alternatively the diffusing surfaces can be applied to a solid lens-shaped object as shown in Figure 5b made of for example plastic or glass and the outer surface of the object can then be provided with a light diffusing surface.

When the diffuser unit 301 is position near a light source, light incident on the first diffusing surface 301a is scattered through a range of angles, but the predominant intensity is the straight-through beam perpendicular to the surface of the disc. Light scattered from the first surface is then incident on the second surface and is further scattered by the second surface 301b. This second scattering stage ensures that the intensity profile is even across the outer surface of the diffuser.

Applications of the diffuser unit include wall lighting, as shown in Figure 6. A lighting unit 601 is provided for fixing to a wall 600. The lighting unit 601 includes a light source 603, such as a light bulb or Light Emitting Diode (LED) and a housing 602 which supports the light source 603 and is capable of being fixed to the wall 600.

The housing 602 is also arranged to support a diffuser unit 301 of the type described above in close proximity to the light source.

Other functional lighting equipment are envisaged such as a table lamp or night light which also use a diffuser unit of the type described above.

Figure 3b shows the intensity distribution of light across the surface of the diffuser unit for a light source which is aligned with the optical axis AA' of the diffuser unit. If the light source is positioned away from the optical axis, as shown in Figure 7a, the light distribution across the outer surface of the diffuser unit 301 remains substantially unchanged. Therefore multiple light sources 701a, b, c may be positioned near the diffuser unit 301 and a substantially constant light distribution maintained across the outer surface of the second diffuser element 301b, as shown in Figure 7b.

This may be contrasted with a conventional single surface diffuser where, if multiple light sources in different locations are used, peaks in light intensity on the surface of the diffuser can be observed, as shown in Figure 7c.

If the multiple light sources used are of different colours, for example if three light sources are used, one of red, one of blue and one of green, the light from each of the sources is uniformly distributed across the surface of the diffuser unit 301 and therefore uniformly mixed with the light from each of the other sources. In this example where red, green and blue light sources are used, by varying the intensity of each of the three light sources any colour can be produced on the outer surface of the diffuser. The visual effect is similar to viewing closely located separate light sources from a distance, where the discrete light sources cannot be resolved and the overall impression is that of a single light source of a colour that is a blend of the component parts. However, when the light sources are viewed close up through the diffuser unit 301 the well-mixed uniform colours give the impression of light being emitted from the outer surface of the diffuser unit 301.

This may be contrasted with a conventional single surface diffuser, where if three light sources are used, the colours from each will not be uniformly mixed, resulting in peaks in individual colour and a small area where the colours blend in a uniform way.

Applications for this arrangement also include wall and table lamps. By providing a remote controller for the light intensity of each of the multiple light sources, colours can be produced to suit the taste of the use. The colours can be varied according to a pre-set pattern or even varied according to sound levels in the room.

In another embodiment the diffuser element 301 has edges which are not circular but straight, to provided square or rectangular or any other polygonal shaped diffuser element, as shown in Figure 8a. This allows a number of diffuser of elements to be tiled together to form a larger panel of diffusers, as shown in Figure 8b. A cell may be formed by providing a single light source 802a, 802b etc close to the inner surface of a diffuser element 801 a, 801 b etc and partitions provided to prevent to the light from a source straying to the diffuser of a neighbouring cell. Alternatively multiple coloured light sources may be provided within each cell, and the intensity of each light source controllable remotely. If red, green and blue light sources are used within each cell the panel may then be used a display to display moving images.

In another embodiment, the diffuser element may be integrated into a light source itself, for example in the tip of an LED package, as shown in Figure 9. This can eliminate the bright spot of an LED and produce a uniform light which is beneficial in some applications.

Alternatively, the diffuser unit 301 can be a solid lens-shaped object formed of inherently scattering material such as translucent white plastic. In this instance light is not scattered at the surface but within the solid material itself.

It is to be understood that various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown and such modifications and variations also fall within the spirit and scope of the appended claims.

Claims

CLAIMS1. A light diffuser unit suitable for placing in the path of light emitted from a light source to diffuse the light emitted from the light source, the light diffuser unit comprising two major surfaces for transmitting light from one side of the light diffuser unit to the other, wherein a first major surfaces is convex and a second major surface is not co-planar with the first major surface, and wherein the diffuser unit is made of a light diffusing material.
2. A light diffuser unit in accordance with claim 1, wherein the diffuser unit is hollow.
3. A light diffuser unit in accordance with claim 1, wherein the diffuser unit is solid.
4. A light diffuser unit in accordance with any preceding claim, wherein the material of which the light diffuser unit is made is inherently light diffusing.
5. A light diffuser unit in accordance with any preceding claim, wherein both of the major surfaces of the light diffuser are rough.
6. A light diffuser unit in accordance with any preceding claim, wherein the second major surface is planar.
7. A light diffuser unit in accordance with any one of claims 1 to 5, wherein the second major surface is convex.
8. A light diffuser unit in accordance with any preceding claim, wherein the curvature of the convex surface or surfaces spherical.
9. A light diffuser unit in accordance with any one of claims 1 to 7, wherein the curvature of the convex surface or surfaces is parabolic.
10. A light diffuser unit in accordance with any preceding claim, wherein the periphery of the major surfaces is circular.
11. A light diffuser unit in accordance with any one of claims 1 to 9, wherein the periphery of the major surfaces is polygonal.
12. A lighting unit having a diffuser unit as described in claims 1 toll, comprising at least one light source and a housing, said housing arranged to locate the diffuser unit in front of the at least one light source and to prevent light from escaping other than through the diffuser unit.
13. A lighting unit in accordance with claim 12, wherein two or more light sources are provided capable of producing light of different colours.
14. A display unit formed of a plurality of light cells, wherein each cell comprises a diffuser unit as described in claims 1 to 11 and at least one light source.
15. A display unit in accordance with claim 14, wherein internal partitions are provided to prevent light leaking between cells.
16. A display unit in accordance with claim 15, wherein each light cell includes an individually controllable red light source, green light source and blue light source.Amendments to the Claims have been filed as follows:-C [AIM S 1. A light diffuser unit suitable for placing in the path of light emitted from a light source to diffuse the light emitted from the light source, the light diffuser unit comprising two major surfaces for transmitting light from one side of the light diffuser unit to the other, wherein a first major surfaces is convex and a second major surface is not co-planar with the first major surface, and wherein the diffuser unit is made of a light diffusing material, wherein the first and second major surfaces of the diffuser unit form a shell defining an internal void such that the interior of the diffuser unit is hollow and wherein the light from the light source passes through the two major surfaces.2. A light diffuser unit in accordance with any preceding claim, wherein the material of which the light diffuser unit is made is inherently light diffusing.3. A light diffuser unit in accordance with any preceding claim, wherein both of the major surfaces of the light diffuser are rough. (0C\i 20 4. A light diffuser unit in accordance with any preceding claim, wherein the second major surface is planar.5. A light diffuser unit in accordance with any one of claims 1 to 3, wherein the second major surface is convex.6. A light diffuser unit in accordance with any preceding claim, wherein the curvature of the convex surface or surfaces is spherical.7. A light diffuser unit in accordance with any one of claims 1 to 5, wherein the curvature of the convex surface or surfaces is parabolic.8. A light diffuser unit in accordance with any preceding claim, wherein the periphery of the major surfaces is circular.9. A light diffuser unit in accordance with any one of claims 1 to 7, wherein the periphery of the major surfaces is polygonal.10. A lighting unit having a diffuser unit as described in claims 1 to 9, S comprising at least one light source and a housing, said housing arranged to locate the diffuser unit in front of the at least one light source and to prevent light from escaping other than through the diffuser unit.11. A lighting unit in accordance with claim 10, wherein two or more light sources are provided capable of producing light of different colours.12. A display unit formed of a plurality of light cells, wherein each cell comprises a diffuser unit as described in claims 1 to 9 and at least one light source.13. A display unit in accordance with claim 12 wherein internal partitions are provided to prevent light leaking between cells.co 14. A display unit in accordance with claim 13, wherein each light cell includes an individually controllable red light source, green light source and blue light source.