GB2398373A - Light guide with dichroic coating for display lamp - Google Patents
Light guide with dichroic coating for display lamp Download PDFInfo
- Publication number
- GB2398373A GB2398373A GB0403130A GB0403130A GB2398373A GB 2398373 A GB2398373 A GB 2398373A GB 0403130 A GB0403130 A GB 0403130A GB 0403130 A GB0403130 A GB 0403130A GB 2398373 A GB2398373 A GB 2398373A
- Authority
- GB
- United Kingdom
- Prior art keywords
- light
- conducting element
- light conducting
- containment
- coating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
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Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0005—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being of the fibre type
- G02B6/0006—Coupling light into the fibre
Abstract
A rod-like component 41 for use in a lamp such that light from sources 45,46 in housing 43 enters the end face 44 has an external dichroic coating 42 which varies in thickness and/or composition along the length of the rod. The coating may comprise a stack of layers in two or more sub stacks each sub stack reflecting a different wavelength range.
Description
À . 2 3 98373 DISPLAY COMPONENT, LAMP AND METHOD OF PRODUCTION This
invention relates to a display component, a lamp incorporating the component and a method for its production.
In co-pending International Application PCT/GB97/01121 and corresponding applications based thereon there is described a light outputting device or lamp comprising: a containment for housing an element for emitting light, the containment having a longitudinal axis and a width transverse of the longitudinal axis; a light conducting element extending axially from, and forming a part of' the containment the light conducting element having an axial length substantially greater than the transverse width; the light conducting element being aligned co-axially with the element for emitting light; the width of the light conducting element being similar to the transverse width; and the light conducting element having a light input region whereby light generated by the element is enabled to pass axially into the light conducting element.
Typically the light conducting element is provided on the outside with a uniform coating to provide for improved efficiency of light transmission through the element from a light input region to an output face therefrom.
According to a first aspect of the present invention there is provided a display component comprising a light conducting element having an axial length substantially greater than the transverse width; the light conducting element having a light input region whereby light is enabled to pass axially into the light conducting element and a dichroic coating on an external surface of the light conducting element which coating varies in thickness or composition or both relative to a datum position typically defined by the light input region.
According to a first preferred version of the first aspect of the present invention the dichroic coating varies in thickness or composition or both relative to a datum position along a longitudinal axis of the lightconducting element.
According to a second preferred version of the first aspect of the present invention or of the first preferred version thereof the coating comprises a stack of layers which :' .e e. ace: 2. : reflects all wavelengths in a given range of light wherein the stack is made up of at least two sub stacks, each sub stack serving to reflect a range of light unique to that sub stack. Typically the wavelengths lie in the visible range of 380-760 nanometres and the stack consists of three sub-stacks of which the first sub-stack strongly reflects wavelengths in the range 380-475nn (blue to blue / green), the second 475 - 595nm (blue/green to yellow), and the third covers the range 595 - 760nm (yellow to deep red). Preferably each sub-stack consists of alternating layers of a high refractive index material and a low refractive index material.
According to a third preferred version of the first aspect of the present invention or of any preceding preferred version thereof the variation in the coating in thickness or composition or both provides for the emission of a proportion of light passing into the element through the side walls of the light conducting element to provide a visible optical effect to an observer viewing the element.
According to a second aspect of the present invention there is provided a light outputting device or lamp comprising: a containment for housing an element for emitting light, the containment having a longitudinal axis and a width transverse of the longitudinal axis; a display component according to the first aspect or Any preferred version thereof linked by way of the light input region and extending axially from, and forming a part of' the containment; the light conducting element having an axial length substantially greater than the transverse width; the light conducting elem.ent..being aligned co-axially with the element for emitting light; the width of the light conducting element being similar to the transverse width; light generated by the element being enabled to pass axially into the light conducting element by way of the light input region.
According to a third aspect of the present invention there is provided a method of fabricating a light outputting device according to the second aspect having a containment for housing an element for emitting light, the containment having a longitudinal axis and a width transverse of the longitudinal axis; a light conducting element extending axially from the containment and having an axial length substantially greater than the transverse width; the light conducting element being À a 3 a aligned coaxially with the element for emitting light in the containment by means of the containment or an extension thereof; the width of the light conducting element being similar to the transverse width; and the light conducting element having a light input region whereby light generated by the element is enabled to pass axially into the light conducting element, characterized by the steps of: providing the light conducting element in the form of a longitudinal member with end faces and an outer surface apart from the end faces; locating around the light conducting element a sleeve member of greater length than the light conducting element with a first end of the light conducting element at or near one end of the sleeve so as to leave a length of sleeve projecting beyond the opposite end of the light conducting element the first end; the opposite end of the light conducting element to the first end forming, at least in part, the light input region; causing the sleeve member to be contiguously juxtaposed with the outer surface of the fight conducting element; locating the element for emitting light in the length of sleeve projecting beyond the opposite end; deforming the length of sleeve so as to form together with the light input region of the light conducting element the containment for the element for emitting light; sealing the deformed length of tube to cause the containment to form a gas tight enclosure for the element for emitting light; and coating the external surface of the light conducting element with a dichroic coating the coating varying in thickness or composition or both relative to a datum position typically the element for emitting light.
' Àe c: A: ...: À .. . . . . . À A À À À . A display component according to the first aspect can receive light from one or more of several different sources. However it is particularly intended for use with a lamp which serves as a source of light which is fed into the face of the element. The display component has an existence independent of the lamp so that if necessary the lamp can be replaced or changed to a lamp of a different type or different light output.
Typically the display component can be provided with a reflector, typically parabolic, to direct light into the light-conducting element which would, in the absence of the reflector, tend to be emitted in a direction away from the light-conducting element.
Consideration will now be briefly given to an observed optical effect with reference to the accompanying drawings of which: Figure 1 is a diagrammatic view of a longitudinal section of an uncoated rod; Figure 2 is a diagrammatic view of a longitudinal section of an uncoated rod; Figure 3 is a diagrammatic section of a longitudinal section of a decorative unit; and Figure 4 is a diagrammatic section of a lamp.
1 LIGHT TRANSMISSION IN A LIGHT coNDucTING ELEMENT IN THE FORM OF A QUARTZ
ROD BY TOTAL INTERNAL REFLECTION
Reference is now made to Figure 1. A rod 11 of quartz with an outer surface 12 has a refractive index no and is surrounded by a medium with a refractive index n2. A light ray L coming to an interface between media of different refractive indices is in general partially reflected and partially transmitted.
If the angle the light ray L makes with the normal to the surface is i and the angle the transmitted ray makes with the normal is _ then by Snell's Law.
no sin| = n2 sin r where no = refractive index of the medium through which the incident ray passes where n2 = refractive index of the medium through which the transmitted ray passes Also, the angle of reflection in medium 1 = the angle of incidence, i, in medium 1 If the angle of incidence of the ray, i exceeds the critical angle, c, given by c= 1/sinn then there is no transmitted ray: the ray is totally internally reflected at the interface.
Is' - Àe. . : :: À À # . . . . À À . That is to say Total Internal Reflection (TIR) can only occur if no > n: Reference is now made to Figure 2. For an element 11 of quartz, light incident at the inner surface at angles greater than 40 degrees to the normal are totally internally reflected. This is the theory behind a quartz light guide and also of optical fibres.
Angle i >40 degrees.
2. MULTI-LAYER OPTICAL COATINGS.
The coating on the element of the present invention consists of a stack of, typically, between 4 and fifty or more very thin layers of two or more transparent materials. In a design, which reflects all wavelengths in the visible range of 380-760 nanometers, the stack may consist of three sub-stacks. The first sub-stack strongly reflects wavelengths in the range say 380-475nn - blue to blue / green, the second say 475 - 595nm blue/green to yellow, and the third covers the range say 595 - 760nm yellow to deep red. Each sub-stack consists of alternating layers of a high refractive index material and a low refractive index material. Silicon dioxide, tantalum oxide, and/or titanium dioxide are commonly used to form the layers. These high melting point materials are typically evaporated into using electron beams.
Figure 3 shows a decorative unit 30 with a rod 31 having a non-uniform coating 32 in the form of a stack made up of three subs-tacks as described in the preceding paragraph. The unit 30 is provided with inlet face 33 at one end whereby ambient light enters the rod 31 and by the mechanisms descried earlier causes visually significant variations in the outside appearance of the unit 30 along the length of the rod 31.
Figure 4 shows a lamp 40 incorporating a rod 41 and with a non-uniform coating 42 similar to that, respectively, of rod 31 and coating 32 in Figure 3. In this case the rod 41 is permanently attached to an integral containment 43 and opens into it by way of inlet face 44.. The containment houses energisable filaments 45, 46. The filaments 45, 46 each serve to produce light of different colours which can be energised either separately or together, if necessary by way of a programmable system so that the :' c: e À À 8 À À À 6. .' : lamp 40 can produce continuously a range of different visual effects to an observer of the outside surface of coating 42.
In general terms the combined stack deposited on the element reflects the entire visible spectrum strongly while allowing infrared and ultraviolet energy to escape through it. This allows the element to run relatively coolly, since 95% of the radiation from an associated lamp is in the infrared and ultraviolet ranges of wavelengths. This cold mirror' coating is sometimes termed 'dichroic', since the radiant energy is sent in two directions, according to wavelength. 'Dichroic' coatings are widely used as a mirror surfaces for display lamps, ensuring that the objects being illuminated are not excessively heated.
In an experimental versions of an element according to the present invention when coupled to a lamp of the type described the dichroic coating has been deposited on the element the total internal reflections of the light travelling down the element are possibly disrupted, allowing light of particular wavelengths (i.e. colours) to escape at various locations on the rod. The coating process used on the element appears to have resulted in the element having a coating, the thickness of which reduces with distance from the light input end. The result would be that the optical properties of the coating would change with position on the element, so the wavelengths of light transmitted out of the rod would vary from location to location.
It also appears that the angle of incidence of light on a dichroic coating strongly affects the actual range of wavelengths reflected and the range of wavelengths transmitted. A coating deposited on a conventional element will have been designed to work optimally over a small range of angles, probably near normal incidence (i.e. at 90 degrees to the surface). Along the proposed element other very different angles of incidence of light on to the coating appear to arise so the coating will become transmitting for certain visible wavelengths at various locations for this reason too.
Another aspect arises from theory telling us that total internal reflection can occur only in the element if the refractive index outside the element is less than that of the : . . . À 8 À À À À 7. . quartz. If a high refractive index material has been deposited on an element of quartz first in the coating process, then light would be expected to escape into the coating.
Whether or not the light is returned to the pipe from the coating would depend on many factors including the angle of incidence and the stack characteristics at that location. Consequently, a complex pattern of coloured light emitted from the pipe could be expected.
Some images observed may be a result of imaging effects. As a result, an imperfect image or even multiple images of a lamp filament may form in the rod. Rays; diverging from these images could give rise to the star like images that have been observed.
Further experimental work is required to establish the mechanism by which the various observed images are formed. However at present it seems likely that as light passes down the element the proportion of the longer wavelength radiation in it (i.e. the red) is steadily reduced due to radial leakage out of the coated curved surface.
The coating at the light input end of the element may be thick enough to be effective at reflecting yellow, green and blue radiation back into the element. However it is assumed that with the dichroic coating steadily reduces in thickness down the element. Then as the light passes down the element, orange, yellow, green, blue and finally violet radiation will escape radially as the coating is too thin to reflect these colours back into the element. This may explain an observed rainbow effect.
The invention is capable of embodiment in a large number of ways. As described in the exemplary embodiments the source of light can be naturally occurring light or many forms of artificial light sources, as described in the earlier application PCT/GB97/01121, including filament, discharge, arc and LED and LCD sources. In addition several different light sources can be used either sequentially or simultaneously. One use would be in connection with a number of LEDs of different colours. Since the coating variation will lead to particular regions of the rod showing different colours then the use of lights of different colours will cause the rod to reveal :'p. c . . À 8 À . . : different visual features depending on the colour of the light or lights currently energised.
The coating on a rod can in addition to being non-uniform in thickness or composition or both along its length can also be subject to local abrasion or shot blasting or other physical disruption resulting in either local thinning of the coating or its complete removal.
The embodiments show a light conducting element in the form of a straight rod. It is not essential that the light carrying element should be straight or of circular or unchanging cross section. The optical effects observed can clearly arise from a light conducting element of a wide variety of shapes so long as the effect of the non- uniform coating is obtained along the length of the element from the light entry region.
Claims (12)
1 A display component comprising a light conducting element having an axial length substantially greater than the transverse width; the light conducting element having a light input region whereby light is enabled to pass axially into the light conducting element and a dichroic coating on an external surface of the light conducting element which coating varies in thickness or composition or both relative to a datum position typically defined by the light input region.
2 A display component as claimed in Claim 1 wherein the dichroic coating varies in thickness or composition or both relative to a datum position along a longitudinal axis of the light-conducting element.
3 A display component as claimed in Claim 1 or Claim 2 wherein the coating comprises a stack of layers which reflects all wavelengths in a given range of light wherein the stack is made up of at least two sub stacks, each sub stack serving to reflect a range of light unique to that sub stack.
4 A display component as claimed in Claim 3 wherein the wavelengths lie in the visible range of 380-760 nanometres and the stack consists of three sub-stacks of which the first sub-stack strongly reflects wavelengths in the range 380 475nn (blue to blue / green), the second 475 - 595nm (blue/green to yellow), and the third covers the range 595 - 760nm (yellow to deep red).
A display component as claimed in Claim 3 or Claim 4 wherein each substack consists of alternating layers of a high refractive index material and a low refractive index material.
6 A display component as claimed in any preceding claim wherein the variation in the coating in thickness or composition or both provides for the emission of a proportion of light passing into the element through the side walls of the light conducting element to provide a visible optical effect to an observer viewing the element.
t. .. . . . . . :: Is: À:- Àe:: :: À À. À in À
7 A light outputting device or lamp comprising: a containment for housing an element for emitting light, the containment having a longitudinal axis and a width transverse of the longitudinal axis; a display component as claimed in any preceding claim linked by way of the light input region and extending axially from, and forming a part off the containment; the light conducting element having an axial length substantially greater than the transverse width; the light conducting element being aligned co- axially with the element for emitting light; the width of the light conducting element being similar to the transverse width; light generated by the element being enabled to pass axially into the light conducting element by way of the light input region.
8 A light outputting device as claimed in Claim 7 wherein the containment house at least two elements for emitting light.
9 A light outputting device as claimed in Claim 8 wherein each element is adapted to provide a unique colour relative to the remaining element or elements.
A method of fabricating a light outputting device as claimed in Claim 7, 8 or 9 having a containment for housing at least one element for emitting light, the containment having a longitudinal axis and a width transverse of the longitudinal axis; a light conducting element extending axially from the containment and having an axial length substantially greater than the transverse width; the light conducting element being aligned coaxially with the element for emitting light in the containment by means of the containment or an extension thereof; the width of the light conducting element being similar to the transverse width; and the light conducting element having a light input region whereby light generated by the element is enabled to pass axially into the light conducting element, characterized by the steps of: ea. e .' providing the light conducting element in the form of a longitudinal member with end faces and an outer surface apart from the end faces; locating around the light conducting element a sleeve member of greater length than the light conducting element with a first end of the light conducting element at or near one end of the sleeve so as to leave a length of sleeve projecting beyond the opposite end of the light conducting element the first end; the opposite end of the light conducting element to the first end forming, at least in part, the light input region; causing the sleeve member to be contiguously juxtaposed with the outer surface of the fight conducting element; locating the element for emitting light in the length of sleeve projecting beyond the opposite end; deforming the length of sleeve so as to form together with the light input region of the light conducting element the containment for the element for emitting light; sealing the deformed length of tube to cause the containment to form a gas tight enclosure for the element for emitting light; and coating the external surface of the light conducting element with a dichroic coating the coating varying in thickness or composition or both relative to a datum position typically the element for emitting light.
11 A method of fabricating as claimed in Claim 10 characterized in that the coating step involves the deposition of a coating comprising a stack of layers of dichroic material.
12 A method of fabricating as claimed in Claim 9 wherein the stack comprises at least two sub-stacks.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0303209A GB0303209D0 (en) | 2003-02-12 | 2003-02-12 | A lamp and a method of production thereof |
| GB0305657A GB0305657D0 (en) | 2003-03-12 | 2003-03-12 | Display component |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0403130D0 GB0403130D0 (en) | 2004-03-17 |
| GB2398373A true GB2398373A (en) | 2004-08-18 |
Family
ID=32031894
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0403130A Withdrawn GB2398373A (en) | 2003-02-12 | 2004-02-12 | Light guide with dichroic coating for display lamp |
Country Status (2)
| Country | Link |
|---|---|
| GB (1) | GB2398373A (en) |
| WO (1) | WO2004072702A1 (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5426576A (en) * | 1993-04-23 | 1995-06-20 | Light & Sound Design, Limited | Colour cross-fading system for a luminaire |
| WO1996000920A1 (en) * | 1994-06-30 | 1996-01-11 | The Whitaker Corporation | Optoelectronic package and bidirectional optical transceiver for use therein |
| US6837606B2 (en) * | 1996-04-23 | 2005-01-04 | Fibre Optic Lamp Company Limited | Light emitting device and arrays thereof |
| AU6454000A (en) * | 1999-07-27 | 2001-02-13 | Fibre Optic Lamp Company Limited | Fibre optic lamps |
-
2004
- 2004-02-12 WO PCT/GB2004/000568 patent/WO2004072702A1/en active Application Filing
- 2004-02-12 GB GB0403130A patent/GB2398373A/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| WO2004072702A1 (en) | 2004-08-26 |
| GB0403130D0 (en) | 2004-03-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |