GB2425615A

GB2425615A - Beam splitting colour mixing optic for coloured light sources

Info

Publication number: GB2425615A
Application number: GB0508523A
Authority: GB
Inventors: Michael John Hanney
Original assignee: Polymer Optics Ltd
Current assignee: Polymer Optics Ltd
Priority date: 2005-04-27
Filing date: 2005-04-27
Publication date: 2006-11-01
Anticipated expiration: 2025-04-27
Also published as: GB2425615B; GB0508523D0

Abstract

An optical component (1) which is suitable for use with multi-coloured light emitting diode (LED) light sources (6) e.g. three separate coloured light sources (6), splits the light (7) received from each of the coloured light sources (6) into different beams on different optical paths, and then emits these beams from different positions from within the optical component (1). The beams emitted from the optical component (1) remain co-axial, and have similar collimated beam properties. The beams emitted from the optical component (1) exhibit good colour mixing at a wide range of illuminated target distances. Total internal reflection (TIR) surface 2, lens 3 and beam steering prisms 4,5 are shown.

Description

Colour Mixing Optic.

The present invention relates to an optical component used for mixing separate colours of light into a single co-axial beam.

A number of illumination situations require separate colours of light such as red, green and blue to be mixed together in various proportions to provide other colours of light for decorative or functional applications.

Prior art exists for the electrical and electronic control methods used to drive a variety of light source types. Different coloured light sources, most typically red, green and blue (RGB) are controlled to emit different relative levels of light output from each coloured light source. When these emitted illuminations are mixed, a different light colour is produced. By changing the relative proportion of each light colour, a very wide range of mixed colours can be made.

Typically, the light sources used for these colour mixing applications are light emitting diodes (LEDs) since they are available with a range of different coloured light outputs and each can be simply current driven to provide an infinitely variable range of light output intensity within their designed maximum and minimum limits.

A number of optical methods are currently used to collect, collimate or focus the light from LED light sources. These include simple lenses and Fresnel lenses. Another method is total-internal-reflection (TIR) optics which collect light from the LED light source over a wider range of emitted angles and therefore have a higher light collection efficiency than the simple lens and Fresnel lens methods.

When the light from separate light sources is required to be collected and collimated or focused into a narrow beam of single colour light, the spatial separation of each of the light sources is preserved through the collimating optical system and separate patches of each colour are projected at some distance from the assembly. This effect is an optical invariant property in simple optical systems and makes satisfactory mixing of the colours of light difficult.

Optical system can be devised which use coloured beam-splitting optics to reflect and/or transmit each of the colours of light such that the separate colours can be brought on to a single optical axis. However, these beam-splitting filter components are typically expensive and introduce considerable light losses into the light paths.

What is needed is a low cost method of combining the separate colours of light with a satisfactory amount of colour mixing and beam collimation to suit a range of colour controllable illumination tasks.

The present invention solves this problem by use of an optical component which splits the light from each of the coloured light sources into different beams on different optical paths and then emitting these beams from different positions from within the optical component. In this way, a typical device with three light sources ( one red, one blue and one green) will then appear to emit light from a greater number of positions from within the optic. Since these emitted beams remain co-axial and with similar collimated beam properties, the beams will colour mix at a wide range of illuminated target distances.

In one embodiment of the present invention, there is provided a typical TIR type light collection optic, similar to that used for LEDs, with an additional prism feature added above each TIR collimating arrangement. The prism feature separates a proportion of the light collected by the TIR structure and reflects the light through an angle to a second prism feature. The second prism feature reflects the light through an angle such that the emitted beam is parallel with the optical axis of the TIR structure, but is spatially displaced from it.

Preferably, the colour mixing optical component has one TIR light collection structure for each of the coloured light sources and a set of prism features to separate and redirect a proportion of the collimated light.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows orthogonal views of a colour mixing optic for three light sources such as red, green and blue LEDs and a cross section of the prism features and the light paths created.

Figure 2 is a plan view of the colour mixing optic designed for three light sources, one of red, one of green and one of blue, and the emission positions of the resulting beams.

Figure 3 shows a plan view of a colour mixing optic for four light sources, one of red, one of green, one of blue and one of orange, and the emission positions of the resulting beams..

A colour mixing optic will now be described with reference to Figure 1.

The colour mixing optic 1 comprises of one or more TIR reflector surfaces 2, one or more focusing lenses 3 and at least one pair of beam steering prisms 4 and 5.

The colour mixing optic 1 is positioned over a light sources but preferably an LED light sources 6. The paths of light 7 emitted from the light source 6 are projected into the colour mixing optic I where the outer bundle of ray paths at wider angles enters the colour mixing optic 1 by refracting through the internal near vertical wall 8. The refracted light then internally reflects off of the TIR surface 2 and is projected forward out of the colour mixing optic I in a near collimated beam along the optical axis of the light source 6.

The paths of light 7 emitted from the light source 6 within a narrow range of angles vertically above the light source 6 are collected by the focusing lens 3 and refracted into a collimated beam. The collimated beam of light from the focusing lens 3 is then internally reflected from a first prism 4 and directed towards a second prism 5 where it is similarly internally reflected in a forward direction out of the colour mixing optic I such that the beam remains collimated and parallel to the optical axis of the light source 6.

In this way, the colour mixing optic 1 provides two collimated beams from each light source 6 where the beams are parallel to each other, but spatially separated across the exit face of the optic.

When the colour mixing optic 1 is used with two or more light sources 6 each with different coloured light emissions, the resulting beam emitted from the colour mixing optic I projected onto a target surface at some distance will be rendered more uniformly mixed.

Figure 2 shows the plan view of a colour mixing optic 1 designed for three light sources, one of red, one of green and one of blue, and the emission positions of the resulting beams.

Light from the red light source is collected by the TIR surface 2 and emitted out of the colour mixing optic in the position shown. Light from the red light source is also focussed by the focusing lens and collimated to the first reflecting prism 4. The reflected light is then directed to the second prism 5 where the collimated red light is emitted parallel to the light from the TIR surface 2. Similarly the green and blue light sources produce a pair of emission points from each single light source. In this way the three coloured light sources appear as six individual light sources in the beams emitted from the colour mixing optic 1.

It is desirable to design the size of the first prism 4 and the second prism 5 so that their projected area is similar to that of the projected area of the TIR surface 2. In this way, the intensity of light emitted from the TIR surface 2 and the second prism 5 will be of approximately equal strength.

Figure 3 shows the plan view of a further embodiment of a colour mixing optic I which is designed to work with four separate light sources of different colour light output.

Light from the red light source is collected by the TIR surface 2 and emitted out of the colour mixing optic in the position shown. Light from the red light source is also focussed by the focusing lens and collimated to the first reflecting prism 4. In this preferred embodiment the first reflecting prism 4 is constructed as a compound prism with two prism facets 9 such that the incident beam is split into two different paths.

The reflected light is then directed to two of the second prisms 5 in two different positions. Similarly, the second prisms 5 are constructed as a compound prism with two prism facets 10 such that the incident beams from the corresponding two first prisms 4 remain collimated and are emitted parallel to the light emitted directly from the TIR surface 2. Similarly the green, blue and orange light sources represented in Figure 3 produce three emission points from each single light source.

In this way the light from each pair of adjacent light sources is emitted from a second prism 5 such that the four coloured light sources appear as twelve individual light sources in the beams emitted from the colour mixing optic 1.

Claims

Claims: 1. An optical component which is suitable for in use splitting

light received from each of a plurality of coloured light sources into different beams on different optical paths, and then emitting these beams from different positions from within the optical component.
2. An optical component as claimed in claim 1, wherein in use the emitted beams remain co-axial and with similar collimated beam properties.
3. An optical component as claimed in claim 2, comprising one TIR (Total Internal Reflection) collection structure for each of the coloured light sources.
4. An optical component as claimed in claim 3, comprising a prism feature added above each TIR collection structure.
5. An optical component as claimed in claim 4, comprising a set of prism features to separate and redirect a proportion of the light for each of the coloured light sources.
6. An optical component as claimed in claim 5, wherein the set of prism features comprises a first prism feature arranged to separate a proportion of the light collected by the TIR collection structure and to reflect the light through an angle to a second prism feature.
7. An optical component as claimed in claim 6, wherein the second prism feature in use reflects light incident thereon through an angle such that the emitted beam is parallel with the optical axis of the TIR collection structure, and such that the emitted beam is spatially displaced from the optical axis of the TIR collection structure.
8. An optical component as claimed in claim 6 or claim 7, wherein the size of the first prism and the second prism is such that their projected area is similar to that of the projected area of the TIR surface, such that in use the intensity of light emitted from the component from the TIR surface is in use approximately equal to the intensity of light emitted from the component via the second prism.
9. An optical component as claimed in claim 6, 7 or 8, wherein the first reflecting prism is constructed as a compound prism with two prism facets such that in use a beam incident thereon is split into two different paths.
10. An optical component as claimed in claim 9, wherein in use light reflected from each facet of the first prism is directed to separate second prisms.
11. An optical component as claimed in claim 10, wherein the second prisms are constructed as a compound prism with two prism facets, such that in use beams incident thereon from corresponding two first prisms remain collimated and are emitted from the component parallel to light emitted directly from the TIR collecting surface.
12. An optical component of claim 11, wherein the TIR collecting surface and the second prisms cooperate in use such that each singe light source produces three emission points.
13. An optical component substantially as herein described.
14. An optical component substantially as herein described, with particular reference to the accompanying drawings.
15. In combination an optical component as claimed in any preceding claim and light sources.
16. The combination of claim 15, wherein the optical is component is positioned over the lights sources.
17. The combination of claim 15 or 16, wherein the light sources comprise three light sources.
18. The combination of claim 15, 16 or 17, wherein the light sources comprise light emitting diode (LED) light sources.
19. The combination of claim 18, wherein the light sources comprise one red source, one green source and one blue source.
20. The combination of claim 18 or 19, wherein the light sources comprise four light sources.
21. The combination of claim 20, wherein the light sources comprise one red source, one green source, one blue source and one orange source.
22. A combination of optical component and light sources substantially as herein described.
23. A combination of optical component and light sources substantially as herein described, with particular reference to the accompanying drawings.