FIELD OF THE INVENTION

The present invention relates to a lamp. In particular to a lamp comprising a plurality of light sources arranged side-by-side in a line and a collimator to control the distribution of light emitted from said light sources onto a surface to be illuminated.

BACKGROUND OF THE INVENTION

An area of a wall may be illuminated using a lamp provided with a light source such as light-emitting diodes (LEDs). The size or spread of the illumination area on a wall is limited, though it can be increased by using more LEDs. However, this results in higher manufacturing costs and also increased cost of using the lamp.

Furthermore, the position of the illumination area on the wall is also dependent on the location of the light source and so if a light source is located on a floor next to the wall, the illumination area on the wall is positioned immediately adjacent to said light source and does not extend up across the wall.

To overcome the problems mentioned above, a collimator may be used. A collimator is a device used for controlling radiation by collimating the light rays so that they, for example, converge so as to focus the rays on a particular point, diverge away from one another or alternatively are made parallel relative to one another. A collimator typically consists of a mirror or a lens which is placed on top of a light source so that light rays passing through the collimator become collimated as they exit the collimator on the opposite side.

However, a problem with one type of known collimators is that a single collimator has to be positioned over each LED which limits the blending of light emitted from the LEDs. Another known type of collimator comprises a straight elongate body which has a general trapezoidal cross-section. This collimator can be used together with several LEDs and enables the emitted light to blend. An example of such a collimator is shown in Figure 1. However, the size and spread of the illumination area is difficult to control as can be appreciated from Figure 2. This Figure shows a computer simulation of an illumination area on a two by two meter wall when positioning the light source 20 cm away from the wall. The illumination area is irregular and does not have a uniform shape, in particular, lower corners of the illumination area are bent downwards. SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a lamp comprising a light source and a collimator that overcomes or substantially alleviates the problems mentioned above.

According to the present invention, there is provided a lamp comprising a plurality of light sources arranged side-by-side in a line and a collimator to control the distribution of light emitted from said light sources onto a surface to be illuminated, wherein the collimator is arcuate in shape so that said line of light sources defines a corresponding arcuate path within the collimator.

Advantageously, the light emitted onto the surface forms an even and uniform illumination area without any portions of the illumination area that bends downwards as is seen when using a straight collimator known from the prior art.

Preferably, the collimator comprises a bottom face formed with a channel, the channel being configured to receive the line of light sources.

Advantageously, the channel enables the majority of the light emitted by the light source to be passed through the collimator when the light source is positioned within the collimator.

Conveniently, the collimator is arcuate about an axis extending at right angles to a plane of the bottom face.

In one embodiment, the collimator is at least part-circular in shape about said axis.

In an alternative embodiment, the collimator follows an elliptical path around said axis.

In yet another embodiment, the collimator comprises a linear portion in addition to a portion that is arcuate about said axis. In this embodiment, the line of light sources may be linear in the linear portion of the collimator.

The different shaped collimators spread the emitted light differently and so the shape and size of the illumination area can be controlled.

In one embodiment, the arcuate shape of the collimator follows a polynomial curve.

Preferably, the collimator comprises a top face through which light is emitted, the top face having a cut out portion which diffuses emitted light.

Advantageously, the cut out portion increases diffusion of emitted light and so the spread of light within the illumination area is more uniform. Conveniently, the collimator comprises a top face through which light is emitted, the top face having a surface roughness which diffuses emitted light.

This provides the advantage of emitted light being diffused and so creates a uniform spread of light within the illumination area.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of a known collimator which does not form part of the present invention;

Figure 2 shows a computer simulation of an illumination area from a light source used in combination with the collimator shown in figure 1 ;

Figure 3 shows top view of a collimator according to the present invention; Figure 4 shows a side view of the collimator shown in Figure 3; Figure 5 shows a computer simulation of an illumination area from a light source used in combination with the collimator of the present invention;

Figure 6 shows a computer simulation of another illumination area from a different light source used in combination with the collimator of the present invention;

Figure 7 shows a top view of a collimator of an alternative embodiment;

Figure 8 shows a top view of a collimator of yet another embodiment; and

Figure 9 shows a cross-sectional view of a collimator according to the present invention.

DETAILED DESCRIPTION

A collimator 1 according to the present invention will now be described with reference to the drawings. The collimator 1 comprises a body 2 having a top and bottom surfaces 3, 4, first and second side surfaces 5, 6 and two end surfaces 7, 8. The body 2 has a semi-circular shape when viewed from the top as illustrated in Figure 3. The cross-section of the body is trapezoidal as can be appreciated from Figure 4. The bottom surface 4 of the body 2 is formed with a channel 9 extending between the two end surfaces 7, 8. The channel 9 is configured to receive a line or an array of light sources such as LEDs 10. The array of light sources (LEDs) have a shape corresponding to the channel 9 of the body 2 so that they can fit neatly into said channel 9. A ceiling 11 of the channel 9 is convex such that it bulges towards the light source. This is best illustrated in Figure 9. The body 2 of the collimator 1 is made out of an optical plastic such as acrylic plastic and is formed into a semi-circular shape by extrusion or moulding such as injection moulding. Alternatively, the body 2 of the collimator 1 may be formed out of an optical glass, such as borosilicate, by extrusion or pressing.

A computer simulation of an illumination area 12 on a two by two meter wall when using the collimator 1 according to the present invention together with LEDs 10 along the whole length of the channel 9 is shown in Figure 5. The light source is positioned 20 cm away from the wall and at the lower end of the wall. The illumination area 12 is more evenly spread and uniform compared to the illumination area shown in Figure 2 when using a known collimator having a straight body as described in the introduction. In particular, the curve or arch of the collimator 1 according to the present invention counteracts the bending or drooping of the lower corners of the illumination area produced when using a known straight collimator as illustrated in Figure 1.

In an alternative embodiment, LEDs 10 are positioned in the centre of the channel 9 only and are not provided in the channel 9 towards the two end faces 7, 8 of the body 2. A computer simulation of the resulting illumination area 13 on a two by two meter wall with the light source positioned 20 cm away from the wall is shown in Figure 6. The distribution and shape of the illumination area is different to the illumination area 12 when using LEDs along the whole length of the channel 9. In particular, the illumination area 13 has an overall more rectangular shape. It is also clear from the illumination area 13 shown in Figure 6, that using LEDs only in the centre of the arched collimator also reduces or counteracts the bending or drooping of the lower corners of the illumination area when using a known straight collimator as illustrated in Figure 1.

It is also intended within the scope of the present invention that the body 16 of the collimator 15 is elliptical in shape when viewed from the top as illustrated in Figure 7. Alternatively, the body may comprise a combination of straight and curved sections so as to achieve the desired spread and size of the illumination area. An example of such a body 17 is shown in Figure 8, wherein a central portion 18 of the body is straight and adjacent side portions 19 are bent or curved. Furthermore, in an alternative un-illustrated embodiment, the collimator follows a polynomial curve. It should be understood that in these three

embodiments, the channel and the array of light source follow the overall shape of the collimator. It shall be appreciated that the collimator according to the different

embodiments described herein are arcuate about an axis extending at right angles to a plane of the bottom face.

Furthermore, the collimator having any of the above described shapes according to the present invention, may have its cross-section modified so as to further diffuse the emitted light. An example of such an embodiment is shown in Figure 9 wherein the top surface 22 of the collimator is cut out so as to create an additional diffusive effect. The cut out portion also reduces the weight of the collimator and it is easy to produce via injection moulding.

Alternatively, a diffusive effect can be created on any of the above described embodiments of the collimator by increasing the surface roughness of the top surface of said collimator. For example, in the embodiment described above with reference to Figures 3 and 4, the surface roughness of the top surface 3 of the collimator 1 can be increased so to increase diffusion of the light rays. This provides the advantage that visible uneven light spread within the illumination area that may be present due to irregularities in the collimated light rays is reduced.

Although the above embodiments have been described to be used with LEDs it should be appreciated that alternative light source may be used, for example a halogen light.

It is envisaged that the collimator according to the present invention is to be used with Philips® Livingcolour lamps where the light is used for creating an ambiance rather than providing light for increasing visibility. However, the collimator is not limited to such a lamp and can be used together with any lamp or light source where the illumination area needs to be controlled.

Furthermore, it should be appreciated that the collimator is not limited to use with a light source for lighting up a wall. It may be used together with a light source for illuminating any surface or the like where a uniform illumination area is desired.

It will be appreciated that the term "comprising" does not exclude other elements or steps and that the indefinite article "a" or "an" does not exclude a plurality. A single processor may fulfill the functions of several items recited in the claims. 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 an advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims. Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel features or any novel combinations of features disclosed herein either explicitly or implicitly or any generalization thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the parent invention. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of features during the prosecution of the present application or of any further application derived there from.

Other modifications and variations falling within the scope of the claims hereinafter will be evident to those skilled in the art.