WO1998046934A1 - Diffuseur de conduit de lumiere a couches dielectriques multiples - Google Patents

Diffuseur de conduit de lumiere a couches dielectriques multiples Download PDF

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Publication number
WO1998046934A1
WO1998046934A1 PCT/CA1998/000211 CA9800211W WO9846934A1 WO 1998046934 A1 WO1998046934 A1 WO 1998046934A1 CA 9800211 W CA9800211 W CA 9800211W WO 9846934 A1 WO9846934 A1 WO 9846934A1
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WO
WIPO (PCT)
Prior art keywords
light
light guide
layers
lighting fixture
dielectric material
Prior art date
Application number
PCT/CA1998/000211
Other languages
English (en)
Inventor
Allan Brent York
Original Assignee
Tir Systems Ltd.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Tir Systems Ltd. filed Critical Tir Systems Ltd.
Priority to AU63888/98A priority Critical patent/AU6388898A/en
Publication of WO1998046934A1 publication Critical patent/WO1998046934A1/fr

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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
    • G02B6/0096—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the lights guides being of the hollow type

Definitions

  • This application is directed to a low aspect ratio, side-emitting hollow light guide formed of alternating layers of smooth, transparent dielectric material and air, for use in diffusing light from a light source whose angular spread is small .
  • a commonly used “spot lamp” lighting fixture employs a parabolic type reflector with a variety of light shaping attachments such as “barn doors”, diffusers, light tents, etc. These attachments can be quickly interchangeably mounted on the light fixture to modify its light output characteristic within a wide range varying from a pinpoint spot light output to a large diffuse globular light output.
  • the present invention provides a lightweight, low aspect ratio light guide diffuser attachment which can be quickly interchangeably mounted on a spot lamp fixture to yield a linear light output characteristic comparable to that of the larger, fragile fluorescent unit.
  • the light guide diffuser incorporates multiple dielectric layers having different refractive indices .
  • the light guide diffuser attachment can be shipped flat or rolled tightly into a tube and easily shipped to a site. Once on location, the lighting practitioner can easily assemble the light guide diffuser attachment and optionally insert one or more light modifying elements to obtain the desired light output characteristic.
  • Such elements can be differ- ent density diffusers, colour correcting filters, colour filters, apertures, polarizing films, etc.
  • the invention provides a light guide which is formed of a plurality (between 2 and 100) of layers of transparent dielectric material such as LEXANTM, with each adjacent pair of dielectric layers being separated by an air gap.
  • the index of refraction of the dielectric material should be between about 1.1 and 2.0.
  • the light guide has a closed transverse cross-sectional shape.
  • the light guide preferably has a low aspect ratio of between about 3 and 36.
  • a light source emits substantially coUimated light rays into one end of the light guide.
  • a mirror at the opposite end of the light guide reflects the light back toward the light source.
  • One or more layers of light modification material may be added to the light guide to alter a selected characteristic of the light which is emitted through the light emitting portion of the light guide.
  • the light modification material layer (s) may be a diffuser having a selected density, a colour correcting filter, a colour filter, an aperture mask, a polarizing film, etc.
  • the invention further provides a lighting fixture having a housing, with a plurality of layers of dielectric material mounted in a front portion of the housing. Each adjacent pair of dielectric material layers is separated by an air gap.
  • a light source emits substantially coUimated light rays into one side of the housing.
  • a mirror mounted in the opposite side of the housing reflects the light back toward the light source.
  • Figures 1A and IB are respectively transverse and longitudinal cross-sectional illustrations of a prior art prismatic light guide coupled to a highly coUimated light source.
  • Figure 2 schematically depicts light interaction with a transparent dielectric in air.
  • Figure 3 is a graph showing the net reflectivity of alternating layers of dielectric and air as a function of angle of incidence for 1, 2, 3, 4 and 8 dielectric layers.
  • Figures 4A and 4B are respectively transverse and longitudinal cross-sectional illustrations of a light guide constructed in accordance with the present invention.
  • Figure 5 tabulates a comparison of center line exit- ance of light output by a prior art prismatic light guide and a multiple layer dielectric light guide constructed in accordance with the invention.
  • Figure 6 is a graphical depiction of the comparisons tabulated in Figure 5.
  • Figure 7 is a longitudinal cross-sectional illustration of a an unclosed lighting structure embodying an aspect of the invention.
  • FIGS 1A and IB depict a typical prior art prismatic light guide 10 formed by rolling a sheet of Optical Lighting FilmTM ("OLF", available from 3M, St. Paul, MN) material 11 into a tube.
  • OLF Optical Lighting Film
  • a semi-cylindrical outer layer 12 of diffuse white material such as TYVEKTM covers half of the outer circumference of light guide 10.
  • a highly coUimated light source 14 emits highly parallel light rays 16 into light guide 10.
  • Light is emitted from light guide 10 only through the 180° sector thereof which is not covered by layer 12.
  • An outer light diffusing layer of translucent material 18 can be applied over some or all of the 180° sector of light guide 10 which is not covered by layer 12.
  • a strip of white vinyl light extractor material 20 positioned inside light guide 10 reflects light toward OLF wall material 11 at an angle outside the angular range within which OLF wall material 11 can confine incident light within light guide 10 by total internal reflection, thus allowing such reflected light to escape from light guide 10 for illumination purposes.
  • Light guide 10 can easily be disassembled and its sheet components (i.e. OLF wall material 11, outer layer 12, diffuser 18) flattened to simplify shipping to a site at which the sheet components can easily be reformed into the tubular configuration shown in Figures 1A and IB.
  • sheet components i.e. OLF wall material 11, outer layer 12, diffuser 18
  • one or more layers (not shown) of a "light modification material" such as colour filters, diffusers, etc. may be inserted between OLF wall material 11 and diffuser 18 to modify the light output characteristics of light guide 10.
  • the present invention recognizes that it is not always necessary to employ relatively expensive OLF wall material
  • OLF wall material 11 to obtain useful light output characteristics. For example, if light guide 10 is comparatively short and wide (aspect ratio « 8) , and if the light rays output by light source 14 are highly collimated, then most of the light rays emitted by light source 14 do not directly encounter OLF wall material 11 as they travel through light guide 10. The total internal reflection capability of OLF wall material 11 is not necessary in such applications. Instead, it is necessary to make light extractor 20 large enough to ensure that sufficient light will escape from light guide 10.
  • Any light emitted into light guide 10 by highly collimated light source 14 which does encounter OLF wall material 11 will typically do so at very shallow incident angles (less than about 10°) .
  • Most such incident light could be reflected within light guide 10 by a single layer of clear (non-prismatic) material having an index of refraction of about 1.5.
  • a single dielectric layer would be insufficient to form a practical light guide, the following description shows that a number of such dielectric layers separated by air gaps will increase reflectivity significantly.
  • Figure 2 depicts a piece of transparent dielectric material 22 such as plastic or glass (which has an index of refraction of about 1.5) in air 24 (which has an index of refraction of about 1.0) .
  • dielectric material 22 such as plastic or glass (which has an index of refraction of about 1.5) in air 24 (which has an index of refraction of about 1.0) .
  • light ray 26 strikes the front surface of dielectric material 22, some of the light is reflected as light ray 28 and some is transmitted through the dielectric material as light ray 30.
  • light ray 30 encounters the back surface of dielectric material 22, some of the light is again reflected by the back surface as light ray 32 and some is transmitted as light ray 34.
  • the foregoing processes continue until all of the initial incoming light ray 26 is either completely reflected or transmitted by the dielectric material 22.
  • the net reflectivity and transmissivity of dielectric material 22 in air can be determined by summing the intensities of the infinite series of reflected and transmitted rays from the front and back surfaces of dielectric material 22.
  • R j - and R b are the front and back surface reflectivities respectively of dielectric material 22.
  • the reflectivity is:
  • the reflectivity is:
  • ⁇ is the angle that the incident light makes with the normal to the front surface of dielectric material 22.
  • Equations (1) and (2) then facilitate determination of the reflectivity of multiple layers of a transparent dielectric material separated by air gaps.
  • Figure 3 graphically depicts the results of such calculations . Note that at higher angles of incidence (i.e. the angles between the light ray and the surface become smaller) the reflectivity approaches 1. For example, for one layer the incident angle has to be at least 86° (or 4° from the surface) to provide a reflectivity of about 80%. However, when 3 layers are used, the angle can increase to 80° (or 10° from the surface) .
  • Light guide diffuser 40 can be a 40 inch long, 5 ⁇ z inch diameter cylinder having three layers of clear LEXANTM dielectric material 42 separated by air gaps 44.
  • a semi- cylindrical outer layer 46 of TYVEKTM covers half of the outer circumference of light guide diffuser 40. Light is emitted from light guide diffuser 40 only through the 180° sector 48 thereof which is not covered by layer 46. If desired, light guide diffuser 40 can be completely enclosed within an outer sheath 50 of diffuse LEXANTM material to "soften" light emitted through sector 48.
  • a strip of ScotchCalTM material 52 is positioned inside light guide diffuser 40 to serve as a light extractor.
  • a mirror 54 can be used to cover the end of light guide diffuser 40 opposite the end to which light source 56 is coupled. Light source 56 emits substantially collimated light rays into light guide diffuser 40, at an average dispersion angle which is less than about 15°.
  • Multiple layer dielectric light guide diffusers constructed in accordance of the invention preferably employ from 2 to 100 layers of transparent dielectric material .
  • the index of refraction of the dielectric material may vary within the range of about 1.1 to 2.0.
  • the dielectric layers are stacked on top of one another and formed into a structure which may be circular, square, rectangular or irregular in cross-section. A small air gap is left between each layer. The air gap is critical since it is the changes in the indices of refraction between the dielectric material and the air which provides the reflectivity.
  • the reflectivity of a multiple layer dielectric light guide diffuser such as that depicted in Figures 4A and 4B is low in comparison to the reflectivity of a prior art prism light guide (i.e. four layers of both dielectric and air have a reflectivity of 84% at an angle of incidence of 80 degrees) .
  • a prior art prism light guide i.e. four layers of both dielectric and air have a reflectivity of 84% at an angle of incidence of 80 degrees
  • such low reflectivity is desirable for diffusing light from a source whose angular spread is small, using a short, tubular multi-layer dielectric light guide diffuser. Since more light is transmitted through the light guide diffuser per interaction with the guide walls, it is easier for the light guide diffuser to extract light from a shallow angle (i.e. substantially collimated) light source.
  • such light guide diffusers can guide most of the light emitted by a substantially collimated light source. This includes the majority of the light emitted by the parabolic reflector of a typical "spot lamp” lighting fixture of the type commonly used in set location lighting applications.
  • the guided light can easily be extracted from the light guide diffuser at a desired distance from the light source by scattering the light via a highly reflective, diffuse material such as ScotchCalTM. The remaining light encounters the internal walls of the light guide diffuser at angles where the reflectivity is lower. In other words, such light easily escapes from the light guide diffuser.
  • the more efficient linear diffuser is a hollow light guide made of multiple layers of transparent dielectric material separated by air gaps, combined with a diffuse extractor, as shown in Figures 4A and 4B.
  • Figure 5 tabulates (in lumens per square foot) and Figure 6 graphically depicts a comparison of center line exitance of light output by a prior art "OLF” prismatic light guide; and, by a multiple layer dielectric ("MLD”) light guide diffuser constructed in accordance with the invention.
  • the comparison indicates that the MLD light guide diffuser delivers almost 25% more surface exitance through its light emitting sector with a significantly higher level of uniformity.
  • Subjective evaluation of light output by the two types of guides reveals that light output by the multiple layer dielectric light guide "looks" significantly more uniform, whether viewed along the length of the guide, or from side to side through the guide's 180° light emitting sector.
  • a further advantage of the invention is that it is significantly easier to design a light extractor for a multiple layer dielectric light guide diffuser than for a prior art prism light guide. This is because the loss rate of the multiple layer dielectric light guide diffuser is significantly higher than that of a prior art prism light guide.
  • Figures 5 and 6 clearly demonstrate the inherent weakness of using short aspect ratio prism light guides with highly collimated light sources.
  • the prism light guide's high reflectivity inhibits the optical performance of the device, whereas a variable number of layers of transparent dielectric material can be "tuned" to the correct level of reflectivity required to match the combination of aspect ratio and angular dispersion of the input light source.
  • Figure 7 shows a multiple layer dielectric light guide diffuser 60 forming the light-emitting front surface of a sign structure 62.
  • Light source 64 emits substantially collimated light into rectangular housing 66.
  • the inner rear surface of housing 66 is covered with a specular or diffuse reflective light extractor material 68, which may also extend up the sides of housing 66.
  • An end mirror 70 formed of specular or white material is mounted in the end of housing 66 opposite light source 64.
  • Mirror 70 is preferably tilted to reflect light at a slight angle (less than about 6°) with respect to an axis extending between light source 64 and mirror 70, toward light source 64 but predominantly toward extractor 68.
  • mirror 70 depends upon the aspect ratio of light guide diffuser 60 and the nature of extractor material 68. For example, if light guide diffuser 60 is very short then it may be advantageous to use a diffuse white material to form mirror 70 to uniformly reflect light back within light guide diffuser 60. If mirror 70 is formed of a specular reflective material then, in a very short light guide diffuser, even if mirror 70 is tilted to reflect light toward extractor 68, mirror 70 may introduce unacceptable "flare" in the form of non-uniform variations in light output by light guide diffuser 60 through its light-emitting front surface.
  • the aspect ratio (AR) of a light guide can be defined as the length of the light guide divided by its smallest significant cross sectional dimension (diameter, thickness or chord length) .
  • the present invention is suitable for applications requiring more than a simple diffuser (AR «l-3) but less than a prismatic or slit hollow light guide (AR «100) . While prismatic guides perform very well at high aspect ratios, they suffer at lower aspect ratios. Simple diffusers usually can not be extended successfully beyond an aspect ratio of about 2 or 3. The invention is well suited to use in hybrid designs.
  • an outer jacket material is often used to "hide” the light extractor material positioned inside the light guide.
  • Such jacket material may not be required in multiple layer dielectric light guide diffusers constructed in accordance with the invention because the internal light extractor material itself may not be required in many cases.
  • the aspect ratio of the device is low (less than about 20) the natural loss rate of the dielectric "stack" may be sufficient to deliver acceptable uniformity and optical efficiency without the use of any other extraction mechanism. This makes it possible to produce true 360° emitting light guides, a feat which is difficult, if not impossible, to achieve with prior art prism light guides having the same aspect ratio.
  • Low aspect ratio, 360° emitting light guides can be useful in pedestrian lighting, bollards, flag poles, and other applications involving short longitudinal structures .
  • Multiple layer dielectric light guide diffusers constructed in accordance with the invention may also incorporate one or more layers of optical "light modification material” to further modify the output light characteristic.
  • a layer of colored polyester gel material could be used to filter the emitted light and change the colour of the light output.
  • Further layers of diffusing material could be added to further “smooth" the light output.
  • masks specific areas to create a custom illumination effect. For example, two masks could be cut and applied to a light guide diffuser, with one mask on the front side of the bottom half of the light guide diffuser, and the other mask on the back side of the top half of the light guide diffuser to yield opposed, upper and lower 180° light emitting sectors in the one device .

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Planar Illumination Modules (AREA)

Abstract

Conduit (40) de lumière formé d'une pluralité (entre 2 et 100) de couches de matériau diélectrique transparent (42) tel que le LEXANMD, chaque couche diélectrique est séparée de la couche adjacente par une couche d'air (44). L'indice de réfraction du matériau diélectrique se situe entre 1,1 et 2,0. En coupe transversale, le conduit de lumière forme une structure fermée, avec un faible rapport hauteur-largeur, compris entre environ 3 et 36. Une source lumineuse (56) émet des rayons lumineux sensiblement collimatés dans une extrémité du conduit de lumière. Un miroir (54) placé à l'extrémité opposée du conduit de lumière réfléchit la lumière en sens inverse, en direction de la source lumineuse. Une ou plusieurs couches de matériau modifiant la lumière peuvent être ajoutées au conduit de lumière pour modifier une caractéristique choisie de la lumière émise à travers la partie émettrice de lumière du conduit de lumière. La couche de modification de lumière peut être un diffuseur présentant une densité sélectionnée, un filtre correcteur de couleurs, un filtre coloré, un masque ajouré ou un film de polarisation. L'invention décrit en outre un dispositif d'éclairage comprenant un boîtier (66); une pluralité de couches de matériau diélectrique sont montées sur une partie avant du boîtier. Chaque couche diélectrique est séparée de la couche diélectrique adjacente par une couche d'air. Une source lumineuse (64) émet des rayons de lumière sensiblement collimatés dans un côté du boîtier. Un miroir (70) monté dans le côté opposé du boîtier réfléchit la lumière en sens inverse, en direction de la source lumineuse.
PCT/CA1998/000211 1997-04-15 1998-03-06 Diffuseur de conduit de lumiere a couches dielectriques multiples WO1998046934A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU63888/98A AU6388898A (en) 1997-04-15 1998-03-06 Multiple layer dielectric light guide diffuser

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US83962397A 1997-04-15 1997-04-15
US08/839,623 1997-04-15

Publications (1)

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WO1998046934A1 true WO1998046934A1 (fr) 1998-10-22

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000017968A1 (fr) * 1998-09-24 2000-03-30 Xircom, Inc. Indicateur d'etat pour un dispositif electronique
CN110906272A (zh) * 2018-09-14 2020-03-24 深圳市绎立锐光科技开发有限公司 一种光源装置及车灯

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1984000800A1 (fr) * 1982-08-09 1984-03-01 Space Lyte Int Systeme de distribution optique avec guide de lumiere
EP0355727A2 (fr) * 1988-08-22 1990-02-28 GTE Products Corporation Guide de lumière de haute réflexion
WO1990004132A1 (fr) * 1988-10-07 1990-04-19 Gulton Industries, Inc. Systeme d'eclairage
EP0437069A1 (fr) * 1990-01-10 1991-07-17 Minnesota Mining And Manufacturing Company Source lumineuse directionnelle de ligne

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1984000800A1 (fr) * 1982-08-09 1984-03-01 Space Lyte Int Systeme de distribution optique avec guide de lumiere
EP0355727A2 (fr) * 1988-08-22 1990-02-28 GTE Products Corporation Guide de lumière de haute réflexion
WO1990004132A1 (fr) * 1988-10-07 1990-04-19 Gulton Industries, Inc. Systeme d'eclairage
EP0437069A1 (fr) * 1990-01-10 1991-07-17 Minnesota Mining And Manufacturing Company Source lumineuse directionnelle de ligne

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6095851A (en) * 1997-11-17 2000-08-01 Xircom, Inc. Status indicator for electronic device
US6241550B1 (en) 1997-11-17 2001-06-05 Xircom, Inc. Connector system
WO2000017968A1 (fr) * 1998-09-24 2000-03-30 Xircom, Inc. Indicateur d'etat pour un dispositif electronique
CN110906272A (zh) * 2018-09-14 2020-03-24 深圳市绎立锐光科技开发有限公司 一种光源装置及车灯
CN110906272B (zh) * 2018-09-14 2021-11-16 深圳市绎立锐光科技开发有限公司 一种光源装置及车灯

Also Published As

Publication number Publication date
AU6388898A (en) 1998-11-11

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