WO2002097323A1 - High efficiency reflector for directing collimated light into light guides - Google Patents
High efficiency reflector for directing collimated light into light guides Download PDFInfo
- Publication number
- WO2002097323A1 WO2002097323A1 PCT/CA2001/001445 CA0101445W WO02097323A1 WO 2002097323 A1 WO2002097323 A1 WO 2002097323A1 CA 0101445 W CA0101445 W CA 0101445W WO 02097323 A1 WO02097323 A1 WO 02097323A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- reflector
- light
- axis
- collimating
- light guide
- Prior art date
Links
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
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4298—Coupling light guides with opto-electronic elements coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers
-
- 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
Definitions
- This invention pertains to efficient reflective coupling of collimat- ed light into the input end of a light guide.
- So-called "point source” optics systems of the type disclosed in United States Patent No. 4,755,918 or Japanese Patent Abstract Publication No. 63-092909A use ellipsoidal and/or spherical reflectors to direct light rays emitted by a lamp through a small optical window for coupling into the input end of a small diameter fibre optic light pipe.
- this invention addresses the problem of directing light rays emitted by an elongate (i.e. non-point) light source into the input end of a comparatively large diameter hollow light guide, while maintaining the input light collimation within a half angle of about 30°.
- FIG. 1 schematically depicts the way in which light is conventionally emitted into the input end of a light guide of the type disclosed in United States Patent Nos. 4,615,579; 4,750,798; 4,787,708; 4,834,495; or, 4,850,665.
- An elongate (i.e. non-point) light source such as an arc-type metal halide light bulb 10 mounted in a socket 12 is slidably inserted through an aperture 14 in a paraboloidal collimator 16.
- the circumferential rim at the wide end of collimator 16 is flanged as shown at 18.
- a mating circumferential flange 20 is provided around the input end of hollow prism light guide 22.
- Flanges 18, 20 are connected together to mechanically couple collimator 16 to the input end of light guide 22.
- Prism light guides work best when the input light is collimated within a half angle of about 30°. This requirement limits the range of suitable light sources, because the efficiency with which light can be emitted into the input end of the light guide decreases rapidly as the size of the light bulb increases.
- Arc-type metal halide light bulbs of the type shown in Figure 1 are reasonably practical light sources for illuminating light guides, due to their high efficiency, compact size and reasonably long lamp life.
- the maximum efficiency with which prior art paraboloidal collimator 16 can couple collimated light into light guide 22 depends on the ratio of the light guide's diameter "D", to the length "L" of the light bulb's arc.
- D:L ratio of about 6: 1
- reflector efficiencies of about 70% can be achieved.
- about 30% of the light emitted by light bulb 10 is typically lost, in the sense that it does not enter the input end of light guide 22.
- a D:L ratio of about 4: 1 typically yields a light guide input coupling efficiency of only about 50% , meaning that about 50% of the light emitted by the light bulb is lost, in the sense that it does not enter the input end of the light guide as collimated light.
- This invention overcomes the coupling efficiency problems associated with conventional light guide systems.
- the invention permits efficient collimation and coupling of light emitted by a one kW metal halide light bulb having a 12,000 hour rated life into a 25 cm diameter light guide.
- Such systems are advantageous in general lighting situations in which high efficiency linear lighting is required and in which maintenance of multiple point source or fluorescent fixtures is problematic.
- the invention provides a reflector for reflecting light emitted by an elongate light source into the input end of a light guide having a light guide diameter "D".
- All embodiments of the invention incorporate a collimating reflector having a narrow apertured end through which the light source is insertably positionable; and, a wide apertured end having a diameter exceeding "D", through which light is emitted into the light guide.
- All embodiments of the invention also incorporate an "output end” annular reflector, or an “input end annular reflector, or both.
- the output end annular reflector has a wide apertured end circumjacent (i.e. circumferentially surrounding) the collimating reflector near its wide apertured end, and a narrow apertured end circumjacent the input end of the light guide.
- the input end annular reflector has a narrow apertured end through which the light source is insertably positionable, and a wide apertured end circumjacent the collimating reflector near its narrow apertured end. All of the reflectors are cylin- drically symmetrical about a common longitudinal axis. Light rays emitted by the light source which pass to the collimating reflector are reflected by the collimating reflector and produce an output light beam having a beam width which varies as a function of distance along the aforementioned axis.
- the light guide's input end is positioned at a selected distance along the axis at which the output light beam has a minimum beam width value.
- the input end annular reflector further has a curved surface, such that, in any cross-sectional plane containing the aforementioned axis, the curved surface defines a first arc on one side of the axis, and, a second arc on an opposed side of the axis.
- the first arc has a first centre of curvature located on the one side of the axis, and further located within a cylinder which is symmetrical about the axis and which has a diameter not greater than the diameter of the collimating reflector's narrow apertured end.
- the second arc has a second centre of curvature located on the opposed side of the axis and further located within the aforementioned cylinder.
- the collimating reflector is preferably an off-axis paraboloidal cross-section, cylindrically symmetrical reflector having a focal point/.
- the output end annular reflector preferably forms a spherical arc section having a center of curvature near the collimating reflector's focal point/.
- the light source is typically a metal halide light bulb having a light emitting arc having one end near the focal point/ and an opposed end near the narrow apertured end of the collimating reflector.
- Figure 1 is a schematic side elevation view of a prior art paraboloidal collimator mounted to reflect light emitted by an arc-type metal halide light bulb into the input end of a light guide.
- Figure 2 is similar to Figure 1 , except that the light guide diameter "D" is less than the diameter of the outward end of the paraboloidal collimator.
- Figure 3 is a schematic side elevation view of a reflector constructed in accordance with the invention.
- Figure 4 is similar to Figure 3, but shows a longer portion of the light guide.
- Figure 5 is a schematic fragmented cross-section showing the geometric characteristics of the preferred off-axis paraboloidal collimator.
- Figure 6 is a schematic side elevation view of a reflector con- structed in accordance with the invention, showing how the paraboloidal collimator reflects into the light guide substantially all light rays which pass directly from the centre "C" of the light source to the paraboloidal collimator.
- Figure 7 is a schematic side elevation view showing how the paraboloidal collimator reflects light rays which pass through the centre, rearward (left) end, and forward (right) end of the light source.
- Figure 8 graphically depicts the variation of the width of the output beam produced at the wide apertured end of the reflector as a function of distance d along the reflector's longitudinal axis.
- reflectors constructed in accordance with the invention include a collimating reflector such as conventional paraboloidal collimator 16A, which is preferably an off-axis paraboloidal cross-section cylindrically symmetric reflector.
- Arc-type metal halide light bulb 10A mounted in socket 12A is slidably inserted through aperture 14A in the narrow end of paraboloidal collimator 16A, as in the case of prior art reflector 16 described above.
- reflectors constructed in accordance with the invention include not only paraboloidal collimator 16A, but also annular reflectors 26 and 28. As seen in Figure 1 , the diameter of prior art paraboloidal collimator 16 at its wide end (i.e.
- the end bearing circumferential flange 18 is substantially equal to the diameter D of light guide 22.
- the wide end diameter of paraboloidal collimator 16A shown in Figures 3 and 4 exceeds the diameter D of light guide 22 A. This facilitates collimation of light emitted by a metal halide light bulb 10A which is larger than light bulb 10, assuming light guides 22, 22A to be of equal diameter.
- Input end annular reflector 26 is an aspherical arc section reflector having a wide apertured end 30 ( Figure 3) circumjacent (i.e. circumferentially surrounding) paraboloidal collimator 16A, near the narrow apertured (i.e. "input") end of paraboloidal collimator 16A.
- Reflector 26 is "annular" in the sense that it forms a ring around axis 27 when viewed from the right along axis 27.)
- Light bulb 10A is slidably inserted through the narrow apertured end 32 of annular reflector 26.
- Annular reflector 26 intercepts much of the light which is emitted rearwardly (i.e. to the left, as viewed in the drawings) by light bulb arc 24A and reflects a substantial portion of such rearwardly emitted light back through aperture 14A and light bulb 10A for further reflection by paraboloidal collimator 16A into light guide 22 A.
- reflector 26 is preferably toroidal in the sense that, when viewed in cross-section as shown in Figures 3 and 4, curved portions 26A and 26B of reflector 26 form circular arcs having centres which lie slightly off the longitudinal axis 27 about which paraboloidal collimator 16A, light guide 22A, reflectors 26, 28 and light bulb 10A are respectively cylindrically symmetrical.
- the circular arc formed by curved reflector portion 26A has a center Cl which is located above axis 27, within the diameter of aperture 14A at the narrow (i.e. "input") end of paraboloidal collimator 16A.
- the center C2 of the circular arc formed by curved reflector portion 26B is beneath axis 27, within the diameter of aperture 14A.
- Centers Cl , C2 need not lie on lines which are diameters of aperture 14A, although such positioning is preferred, as shown in Figure 3. Generally, it is sufficient to locate centers Cl , C2 within a cylinder which is symmetric about axis 27 and which has a diameter equal to the diameter of aperture 14A.
- the inner reflecting surface of reflector 26 is preferably slightly diffuse (i.e. non- specular) to further reduce possible reabsorption by arc 24A of light rays reflected by reflector 26.
- the end of arc 24 A closest to the wide end of paraboloidal collimator 16A is positioned to coincide with, or at least be located near to the focal point/ of paraboloidal collimator 16A.
- Light rays emitted by arc 24A near focal point/ which reach paraboloidal collimator 16A are reflected by paraboloidal collimator 16A through a range of angles toward the input end of light guide 22A. If the input end of light guide 22A were moved away from the output end of paraboloidal collimator 16A (i.e. moved to the right, as viewed in the drawings) then more of the light rays reflected by paraboloidal collimator 16A could be coupled into the input end of light guide 22 A. However, this would again leave an annular region or gap through which light rays passing directly from arc 24A would be lost. Annular reflector 28 solves this problem as well as the aforementioned problem respecting loss of light rays at annular region 25.
- Output end annular reflector 28 is a spherical arc section reflector having a center coinciding with focal point/. More particularly, reflector 28 has a wide apertured end 34 ( Figure 4) circumjacent (i.e. circumferentially surrounding) paraboloidal collimator 16A near the wide apertured (i.e. "output") end of paraboloidal collimator 16A. Reflector 28 also has a narrow apertured end 36 circumjacent the input end of light guide 22A.
- Reflector 28 is "annular" in the sense that it forms a ring around axis 27 when viewed from the left along axis 27.) Light rays which would otherwise be lost through annular region 25 as aforesaid are reflected by reflector 28 for possible re-reflection by paraboloidal collimator 16A into light guide 22A. The efficiency with which reflector 28 reflects light is not particularly high due to a number of factors.
- some rays may be lost due to absorption by reflector 28 itself (collimator 16A and reflector 26 are also absorptive to some degree); some rays may be lost due to reflection onto and reabsorption by arc 24A; some rays may be lost due to reflection through aperture 14A; and, in general, efficiency is reduced whenever multiple reflections occur, such as reflection by reflector 28 followed by further reflection by paraboloidal collimator 16A.
- the inner reflecting surface of reflector 28 may be made slightly diffuse (i.e. non-specular) to further reduce possible reabsorption by arc 24A of light rays reflected by reflector 28, although this is not essential.
- Figure 5 illustrates the preferred geometric characteristics of off- axis paraboloidal collimator 16A.
- these charac- teristics enable collimator 16A to direct into the input end of light guide 22A, as collimated light, substantially all light rays which pass directly from arc 24A to paraboloidal collimator 16A.
- Persons skilled in the art conventionally use the term "collimated", as does this application, to describe a light beam containing light rays which trace paths defining a limited range of directions, as opposed to a non-collimated light beam containing rays which trace paths in all directions.
- paraboloidal collimator 16A is a "collimating" reflector and that light rays 40 depicted in Figure 6 are “collimated", even though rays 40 do not represent theoretically perfect collimation.
- Perfect collimation in which light rays propagate in parallel relationship without any crossing or intersection of the rays' paths, can never be attained in practice, as is well known to persons skilled in the art. See for example The Photonics Dictionary, 45th ed., 1999, Laurin Publ. Co. Inc., Pittsfield, MA which defines collimated radiation as "Radiation in which every ray from any given object point can be considered to be parallel to every other. This is never completely the case: The light from a star is really diverging, and all collimators have aberrations. "
- Paraboloidal collimator 16A consists of two parabolic sections located on opposite sides of axis 27 (i.e. the upper and lower sides of axis 27, as viewed in the drawings).
- the upper parabolic section is formed by rotating a parabola 16A-1 through a 180° arc about and above axis 27, as viewed in Figure 5.
- Parabola 16A-1 is an "off-axis" parabola, in that its vertex V is located above, not on, axis 27.
- the axis 38 of parabola 16A-1 intersects axis 27 at an angle ⁇ , with the parab- ola's focus/being at the point of intersection of axes 27, 38.
- the focal length/ , of parabola 16A-1 is the segment of axis 38 extending between the parabola's vertex V and focus/.
- parabola 16A-1 is defined by the equation:
- the lower parabolic section of paraboloidal collimator 16A is identical to the upper parabolic section, except that it is formed by rotating another off-axis parabola through a 180° arc about and below axis 27, as viewed in Figure 5.
- the above-described off-axis, cylindrically symmetric characteristics of paraboloidal collimator 16A ensure that substantially all of the light rays 40 which pass directly from light bulb arc 24 A (more particularly, all light rays originating or passing through the centre "C" of light bulb arc 24 A) to paraboloidal collimator 16A are reflected into the input end of light guide 22A. Accordingly, rays which would otherwise be lost in annular region 25 ( Figure 2) if a prior art, non off-axis paraboloidal reflector 16 having an output diameter greater than the light guide's input diameter were used, are collimated and directed into the input end of light guide 22A by off-axis paraboloidal collimator 16A.
- Light bulb arc 24A is elongate and emits light rays along its entire length "L", not just from its centre "C". As previously explained, this has an important bearing on the efficiency with which collimated light can be coupled into the light guide.
- Figure 7, which is similar to Figure 6 but omits reflectors 26, 28 and light guide 22A, shows not only light rays which originate at the centre "C" of arc 24A, but also light rays which originate near the rearward (left) and forward (right) ends of arc 24A.
- the width of the light beam produced by reflector 16A varies as a function of distance d along axis 27.
- the output beam's width is essentially equal to the diame- ter D r of the wide apertured end of reflector 16A.
- the beam width then decreases as d increases, eventually reaching a minimum value D 0 (d); and, thereafter, the beam width continues to increase as d increases.
- the narrow apertured end 36 of output end annular reflector 28 coincide precisely with the input end of light guide 22A.
- end 36 may project a short distance inside the input end of the light guide.
- This construction which is convenient if the light guide happens to be out-of-round at its input end, is still considered to be circumjacent (i.e. circumferentially surrounds) the input end of the light guide, within the meaning of the claims.
- Persons skilled in the art will also understand that the invention is not confined to the dimensional or geometrical relationships depicted in the drawings. The scope of the invention is to be construed in accordance with the substance defined by the following claims.
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002445433A CA2445433C (en) | 2001-05-29 | 2001-10-11 | High efficiency reflector for directing collimated light into light guides |
JP2003500466A JP2004527014A (en) | 2001-05-29 | 2001-10-11 | Highly efficient reflector for directing parallel light into an optical waveguide |
EP01980073A EP1390663A1 (en) | 2001-05-29 | 2001-10-11 | High efficiency reflector for directing collimated light into light guides |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/865,430 US6418253B2 (en) | 1999-03-08 | 2001-05-29 | High efficiency reflector for directing collimated light into light guides |
US09/865,430 | 2001-05-29 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2002097323A1 true WO2002097323A1 (en) | 2002-12-05 |
Family
ID=25345495
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/CA2001/001445 WO2002097323A1 (en) | 2001-05-29 | 2001-10-11 | High efficiency reflector for directing collimated light into light guides |
Country Status (5)
Country | Link |
---|---|
US (2) | US6418253B2 (en) |
EP (1) | EP1390663A1 (en) |
JP (1) | JP2004527014A (en) |
CA (1) | CA2445433C (en) |
WO (1) | WO2002097323A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7438423B2 (en) | 2005-08-29 | 2008-10-21 | 3M Innovative Properties Company | Illumination system and projection system incorporating same |
Families Citing this family (21)
Publication number | Priority date | Publication date | Assignee | Title |
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DE19932430C2 (en) * | 1999-07-12 | 2002-03-14 | Harting Elektrooptische Bauteile Gmbh & Co Kg | Opto-electronic assembly and component for this assembly |
US6809892B2 (en) * | 2000-07-26 | 2004-10-26 | 3M Innovative Properties Company | Hollow surface illuminator |
US6840633B2 (en) * | 2000-11-30 | 2005-01-11 | Texas Instruments Incorporated | Lamp reflector assembly |
US7064740B2 (en) * | 2001-11-09 | 2006-06-20 | Sharp Laboratories Of America, Inc. | Backlit display with improved dynamic range |
AU2003236963A1 (en) * | 2002-06-28 | 2004-01-19 | Koninklijke Philips Electronics N.V. | Luminaire and dynamic road-marking unit |
US6783250B2 (en) * | 2002-09-25 | 2004-08-31 | Koninklijke Philips Electronics N.V. | Efficient light collector for projection display system |
JP4757201B2 (en) * | 2003-12-18 | 2011-08-24 | シャープ株式会社 | Dynamic gamma for liquid crystal displays |
US8395577B2 (en) | 2004-05-04 | 2013-03-12 | Sharp Laboratories Of America, Inc. | Liquid crystal display with illumination control |
US7872631B2 (en) | 2004-05-04 | 2011-01-18 | Sharp Laboratories Of America, Inc. | Liquid crystal display with temporal black point |
US7602369B2 (en) | 2004-05-04 | 2009-10-13 | Sharp Laboratories Of America, Inc. | Liquid crystal display with colored backlight |
US7777714B2 (en) | 2004-05-04 | 2010-08-17 | Sharp Laboratories Of America, Inc. | Liquid crystal display with adaptive width |
US7898519B2 (en) | 2005-02-17 | 2011-03-01 | Sharp Laboratories Of America, Inc. | Method for overdriving a backlit display |
US8050512B2 (en) | 2004-11-16 | 2011-11-01 | Sharp Laboratories Of America, Inc. | High dynamic range images from low dynamic range images |
US8050511B2 (en) | 2004-11-16 | 2011-11-01 | Sharp Laboratories Of America, Inc. | High dynamic range images from low dynamic range images |
US8121401B2 (en) | 2006-01-24 | 2012-02-21 | Sharp Labortories of America, Inc. | Method for reducing enhancement of artifacts and noise in image color enhancement |
US9143657B2 (en) | 2006-01-24 | 2015-09-22 | Sharp Laboratories Of America, Inc. | Color enhancement technique using skin color detection |
US7592996B2 (en) * | 2006-06-02 | 2009-09-22 | Samsung Electronics Co., Ltd. | Multiprimary color display with dynamic gamut mapping |
US8941580B2 (en) | 2006-11-30 | 2015-01-27 | Sharp Laboratories Of America, Inc. | Liquid crystal display with area adaptive backlight |
JP2010140888A (en) * | 2008-11-14 | 2010-06-24 | Seiko Epson Corp | Lighting device, and projector |
US8632232B2 (en) * | 2010-03-31 | 2014-01-21 | Koito Manufacturing Co., Ltd. | Vehicular headlamp having a columnar light guide |
JP2011216278A (en) * | 2010-03-31 | 2011-10-27 | Koito Mfg Co Ltd | Lamp fitting for vehicle |
Citations (1)
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WO2000053972A1 (en) * | 1999-03-08 | 2000-09-14 | Minnesota Mining And Manufacturing Company | High efficiency reflector for directing collimated light into light guides |
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US2179161A (en) | 1938-03-24 | 1939-11-07 | Rambusch Decorating Company | Illuminating device |
US4241382A (en) | 1979-03-23 | 1980-12-23 | Maurice Daniel | Fiber optics illuminator |
US4615579A (en) | 1983-08-29 | 1986-10-07 | Canadian Patents & Development Ltd. | Prism light guide luminaire |
US4750798A (en) | 1983-08-29 | 1988-06-14 | Canadian Patents And Developement Limited | Prism light guide luminaire |
JPS6392909A (en) | 1986-10-08 | 1988-04-23 | Alps Electric Co Ltd | Condenser |
US4850665A (en) | 1987-02-20 | 1989-07-25 | Minnesota Mining And Manufacturing Company | Method and apparatus for controlled emission of light from prism light guide |
US4755918A (en) | 1987-04-06 | 1988-07-05 | Lumitex, Inc. | Reflector system |
US4787708A (en) | 1987-05-08 | 1988-11-29 | Tir Systems Ltd. | Apparatus for continuously controlled emission of light from prism light guide |
US4834495A (en) | 1987-05-08 | 1989-05-30 | Minnesota Mining And Manufacturing Company | Collapsible light pipe |
-
2001
- 2001-05-29 US US09/865,430 patent/US6418253B2/en not_active Expired - Lifetime
- 2001-10-11 WO PCT/CA2001/001445 patent/WO2002097323A1/en not_active Application Discontinuation
- 2001-10-11 CA CA002445433A patent/CA2445433C/en not_active Expired - Lifetime
- 2001-10-11 EP EP01980073A patent/EP1390663A1/en not_active Withdrawn
- 2001-10-11 JP JP2003500466A patent/JP2004527014A/en active Pending
-
2002
- 2002-05-10 US US10/142,161 patent/US6522807B2/en not_active Expired - Lifetime
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2000053972A1 (en) * | 1999-03-08 | 2000-09-14 | Minnesota Mining And Manufacturing Company | High efficiency reflector for directing collimated light into light guides |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7438423B2 (en) | 2005-08-29 | 2008-10-21 | 3M Innovative Properties Company | Illumination system and projection system incorporating same |
US7841726B2 (en) | 2005-08-29 | 2010-11-30 | 3M Innovative Properties Company | Illumination system and projection system incorporating the same |
Also Published As
Publication number | Publication date |
---|---|
US20010038736A1 (en) | 2001-11-08 |
EP1390663A1 (en) | 2004-02-25 |
US6418253B2 (en) | 2002-07-09 |
CA2445433A1 (en) | 2002-12-05 |
JP2004527014A (en) | 2004-09-02 |
US20020159692A1 (en) | 2002-10-31 |
CA2445433C (en) | 2007-03-27 |
US6522807B2 (en) | 2003-02-18 |
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