WO2007035902A1 - Procédé et système d’extraction de lumière d’une del au moyen d’éléments optiques - Google Patents

Procédé et système d’extraction de lumière d’une del au moyen d’éléments optiques Download PDF

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Publication number
WO2007035902A1
WO2007035902A1 PCT/US2006/036933 US2006036933W WO2007035902A1 WO 2007035902 A1 WO2007035902 A1 WO 2007035902A1 US 2006036933 W US2006036933 W US 2006036933W WO 2007035902 A1 WO2007035902 A1 WO 2007035902A1
Authority
WO
WIPO (PCT)
Prior art keywords
led
light
optical elements
extraction system
emitted
Prior art date
Application number
PCT/US2006/036933
Other languages
English (en)
Inventor
Nayef M. Abu-Ageel
Original Assignee
Abu-Ageel Nayef M
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 Abu-Ageel Nayef M filed Critical Abu-Ageel Nayef M
Priority to US11/534,217 priority Critical patent/US7360936B2/en
Publication of WO2007035902A1 publication Critical patent/WO2007035902A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V7/00—Reflectors for light sources
    • F21V7/04—Optical design
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2115/00—Light-generating elements of semiconductor light sources
    • F21Y2115/10—Light-emitting diodes [LED]

Definitions

  • the invention relates generally to light emitting diodes (LEDs), and more particularly, to optical devices for extracting and conditioning light emitted from light emitting diodes.
  • LEDs Light emitting diodes
  • LEDs are considered attractive light sources for various applications such as such as traffic signals, displays, automobile headlights and taillights and conventional indoor lighting. LEDs are generally more reliable and efficient than other light sources, such as incandescent bulbs.
  • LEDs only a small portion (about 2%) of light generated within the LED active layer can be extracted and utilized while the remaining part is absorbed within the LED structure itself. This is due to the difficulty for light to be extracted from LED semiconductor materials, which have a relatively high index of refraction.
  • Typical LED semiconductors have index of refraction ranging from 2.2 to 3.8, which is high when compared to that of ambient air (about 1.0).
  • the light extraction system uses millions of optical micro-elements formed on an extraction plate to extract and collimate LED light.
  • the extraction plate is manufactured separately using conventional IC fabrication techniques, and then attached or bonded to an LED surface.
  • FIG. IA shows a perspective view of a light extraction system utilizing an extraction plate and LED.
  • FIG. IB shows a perspective view of a light extraction system utilizing an extraction plate, encapsulating epoxy and LED.
  • FIG. 2A shows a perspective view of an extraction plate comprising a micro-aperture, micro-waveguide and micro-lens arrays.
  • FIG. 2B shows a cross sectional view of the extraction plate shown in FIG. 2 A.
  • FIGS. 2C-2D show exploded views of the extraction plate of FIG. 2 A.
  • FIG. 2E shows a cross sectional view of the extraction plate of FIG. 2 A with a highly reflective specular coating applied to the side walls of its micro- waveguides.
  • FIG. 3 A shows a perspective view of an alternative extraction plate comprising micro- aperture and micro-waveguide arrays.
  • FIG. 3B shows a cross sectional view of the extraction plate shown in FIG. 3 A.
  • FIG. 4A shows a top view of another extraction plate comprising micro-aperture and micro-tunnel arrays.
  • FIG. 4B shows a cross sectional view of the extraction plate shown in FIG. 4 A.
  • FIG. 5 A shows a perspective view of another alternative extraction plate comprising micro-aperture and micro-lens arrays.
  • FIG. 5B shows an exploded view of the extraction plate shown in FIG. 5 A.
  • FIG. 5C shows a cross sectional view of the extraction plate shown in FIG. 5 A.
  • FIG. 6A shows a perspective view of a light extraction system having an extraction plate comprising micro-waveguide and optional micro-lens arrays attached to an LED having a patterned reflective coating formed thereon acting as a micro-aperture.
  • FIG. 6B shows an exploded view of the extraction system shown in FIG. 6 A.
  • FIG. 7A shows a perspective view of a light extraction system having an extraction plate comprising a micro-lens array attached to an LED having a patterned reflective coating formed thereon acting as a micro-aperture.
  • FIG. 7B shows an exploded view of the light extraction system shown in FIG. 7 A.
  • FIGS. IA and B show perspective views of LED light extraction systems 200 and 250, respectively, in accordance with exemplary embodiments of the invention.
  • the LED light extraction system 200 includes a light emitting diode (LED)
  • the LED light extraction system 250 (FIG. IB) includes the LED 100, an encapsulating epoxy layer 120 applied to the emitting surface 110 of LED 100 and an extraction plate 50. Extraction plate 50 is bonded directly or attached to the emitting surface 110 (FIG. IA) or to the encapsulation epoxy layer 120 (FIG. IB) of LED 100 using a thin transparent adhesive.
  • the adhesive can be a continuous adhesive layer that covers the whole emitting surface 110 or epoxy layer 120, or alternatively, it may be a patterned adhesive layer that covers only part of the surface 110. Suitable adhesives are well known to those skilled in the art.
  • the extraction plate 50 can have a size equal or smaller than the size of the emitting surface of the LED 100 and its shape can be rectangular, square, circular or any other suitable shape.
  • the LED 100 is any type, structure or color of LED formed on a suitable semiconductor substrate. Although a single LED is depicted in the figures, the invention is not limited to this particular arrangement.
  • the extraction plates disclosed herein can also be applied to arrays of plural LEDs formed on a common semiconductor substrate.
  • FIG. 2 A shows a perspective view of the extraction plate 50, which comprises an aperture plate 34a, micro-waveguide array 34b and a micro-lens array 34c.
  • Each micro-lens corresponds to a micro-waveguide and a micro-aperture.
  • the optical axes of the micro- waveguides and micro-lenses are substantially orthogonal to the LED's light emitting surface 110.
  • the aperture array 34a consists of a plate 34al made of a highly light-transmissive material with a patterned highly reflective coating 34a2 applied to its top surface.
  • the index of refraction of array 34a i.e., the plate material
  • the index of refraction of array 34a is preferably equal or larger than the index of refraction of the LED semiconductor material, e.g., the light emitting layer of the LED material.
  • FIG. 2C A perspective view of the micro-waveguide array 34b and micro-lens array 34c is shown in FIG. 2C. Both arrays 34b and 34c can be made on a single plate of transparent material with a refractive index preferably equal or larger than the index of refraction of the LED semiconductor material.
  • FIG. 2B A cross-sectional view of the aperture 34a, micro-waveguide 34b and micro-lens 34c arrays is shown in FIG. 2B.
  • Design parameters of each optical element (e.g., micro-waveguide, micro-lens, micro- apertures, or micro-tunnel) within an array 34a, 34b and 34c include shape and size of entrance and exit apertures, depth, sidewalls shape and taper, and orientation.
  • Optical elements within an array 34a, 34b and 34c can have uniform, non-uniform, random or non- random distributions and range from one optical element to millions of micro elements.
  • the optical elements can have a uniform individual structure, or each optical element can be distinct in its structure and/or design parameters. Combinations of uniform and distinct optical elements can be employed in the arrays disclosed herein.
  • the spatial distribution of output radiation of the system 200 or 250 can be varied by changing the arrangement, uniformity, designs, number and density of the optical elements included in the extraction plate 50.
  • the size of the entrance/exit aperture of each optical element is preferably greater than or equal to 5 ⁇ m in diameter in case of visible light in order to avoid light diffraction phenomenon.
  • the optical elements can be arranged as a one-dimensional array, two-dimensional array, circular array and can be aligned or oriented individually.
  • the extraction plate 55 does not include the aperture array 34a. Instead, the sidewalls of the micro-waveguides within micro- waveguide array 34b are coated with a highly reflective coating 34br.
  • the operation of the extraction plates 50 and 55 is described as follows. Some of the light emitted from the LED 100 and impinging on the extraction plate 50 or 55 enters through the openings of the aperture array 34a and the remainder is reflected back into the LED 100 by the highly reflective coating 34a2 and 34br. Some of this reflected light gets absorbed and lost within the LED 100, some gets absorbed and regenerated with a different angle, and the remainder gets reflected back toward the extraction plate 50 and 55 by a reflective coating formed on the bottom side of the LED 100 and/or by total internal reflection (TIR) within the LED 100, depending on the LED structure. This process continues until all the light is either absorbed or transmitted through the extraction plate 50 or 55.
  • TIR total internal reflection
  • extraction plate 50 and 55 provides control over the distribution of output light in terms of intensity and cone angle at the location of each element.
  • FIGS. 3A - 5C show alternative extraction plates structures 60, 70, 80 that can be substituted for the extraction plate 50 shown in FIGS. IA - B.
  • FIGS. 3 A and 3B show perspective and cross sectional views of extraction plate 60 comprising only a micro-waveguide array 34b and an aperture array 34a, without the micro- lens array 34c.
  • the aperture array 34a has a patterned highly reflective coating 35 applied to its top surface.
  • FIGS. 4A and 4B show perspective and cross sectional views of an alternative extraction plate 70 comprising of a micro-tunnel array 37b and an aperture array 37a.
  • the internal sidewalls 38b (exploded view of FIG. 4A) of each micro-tunnel are coated with a highly reflective coating 39b (FIG. 4B).
  • Part of the light impinging on extraction plate 70 enters the hollow micro-tunnel array 37b and gets collimated via reflection off of the sidewalls 38b. The remainder of this light gets reflected back into the LED 100 by the highly reflective coating 39a of aperture array 37a.
  • the advantages of extraction plate 70 are compactness and high transmission efficiency of light without the need for anti-reflective (AR) coatings at the exit 38c apertures of its micro-tunnels.
  • AR anti-reflective
  • micro-tunnels of array 37b are filled with a high-refractive index material.
  • the filled micro-tunnels allow more LED light to enter the micro-tunnels compared to the hollow micro-tunnels.
  • FIGS. 5 A, 5B and 5 C show integrated and exploded perspective views and cross- sectional views, respectively, of an extraction plate 80.
  • the extraction plate 80 comprises an aperture array 74a and a micro-lens array 74c made on a single light-transmissive plate 82.
  • the micro-lens array 74c performs the collimation function of output light via micro-lens refraction.
  • the reflective coatings 33a2, 35, 39a, and 75 of aperture arrays 34a can be of specular or diffusive type, whereas, sidewall reflective coatings 34br and 39b are preferably of the specular type.
  • the aperture array 34a (FIG. 2 and FIG. 3) and 74a (FIG. 5) is omitted, and instead, a highly reflective patterned coating 300 and 310 is applied directly to the emitting surface of the LED (or encapsulating epoxy) leading to extraction systems 400 and 500 as shown in FIG. 6 and FIG. 7, respectively.
  • Extraction plate 350 consists of a micro-waveguide array 34b and an optional micro-lens array 34c while the highly reflective patterned coating 300 is applied directly to the LED surface 110 or epoxy layer 120.
  • Perspective integrated and exploded views of an alternative light extraction system are shown in FIG. 6A and FIG. 6B, respectively.
  • Extraction plate 350 consists of a micro-waveguide array 34b and an optional micro-lens array 34c while the highly reflective patterned coating 300 is applied directly to the LED surface 110 or epoxy layer 120.
  • Extraction plate 360 includes a micro- lens array 74c while the highly reflective patterned coating 310 is applied to the LED surface 110 or epoxy layer 120 directly.
  • the light extraction systems 400, 500 operate is substantially the same manner as described above for the light extraction systems 200, 250 depicted in FIGS. IA - B.
  • the reflective coatings 300 and 310 applied to the LED emitting surface 100 or epoxy layer 120 can be of specular or diffusive type.
  • Antireflection coating such as sub-wavelength structures or gratings can be applied to the front and/or back sides of the extraction plates described herein to reduce Fresnel reflections.
  • optical element arrays disclosed herein can be made using various conventional manufacturing methods including, but not limited to, dry etch techniques such as reactive ion etch (RIE) technique, wet etch techniques such as the use of fluoride-based aqueous etching of Pyrex ® substrates or the use of buffered oxide etch (BOE) to form optical elements in fused silica substrates.
  • RIE reactive ion etch
  • BOE buffered oxide etch
  • Additional fabrication techniques can use photosensitive glasses such as Foturan ® produced by Schott Glass, Inc. or combine a spin-on glass (SOG) process and standard LIGA techniques. Further techniques include glass-drawing which is commonly used in fabricating micro-channel plates (MCPs), laser patterning techniques, nano-technology techniques and combinations of two or more of the foregoing techniques.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Led Device Packages (AREA)

Abstract

Dans la présente invention, une plaque d’extraction de lumière (50) peut être utilisée avec une diode électroluminescente (DEL) (100) pour extraire efficacement et réaliser un contrôle sur la distribution spatiale de la lumière extraite en termes d’intensité et d’angle. La plaque d’extraction (50) peut comporter des millions de microéléments optiques et peut être fabriquée indépendamment de la DEL au moyen de techniques de fabrication de circuit intégré (IC) conventionnelles. La plaque d'extraction (50) est de préférence reliée ou fixée à une surface de la DEL (110).
PCT/US2006/036933 2003-06-10 2006-09-21 Procédé et système d’extraction de lumière d’une del au moyen d’éléments optiques WO2007035902A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US11/534,217 US7360936B2 (en) 2003-06-10 2006-09-22 Method and system of LED light extraction using optical elements

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US71910905P 2005-09-21 2005-09-21
US60/719,109 2005-09-21

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US10/458,390 Continuation-In-Part US7306344B2 (en) 2003-06-10 2003-06-10 Light guide array, fabrication methods and optical system employing same

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US11/534,217 Continuation US7360936B2 (en) 2003-06-10 2006-09-22 Method and system of LED light extraction using optical elements

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WO2007035902A1 true WO2007035902A1 (fr) 2007-03-29

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8742406B1 (en) 2011-02-16 2014-06-03 Iowa State University Research Foundation, Inc. Soft lithography microlens fabrication and array for enhanced light extraction from organic light emitting diodes (OLEDs)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5396350A (en) * 1993-11-05 1995-03-07 Alliedsignal Inc. Backlighting apparatus employing an array of microprisms
US5598281A (en) * 1993-11-19 1997-01-28 Alliedsignal Inc. Backlight assembly for improved illumination employing tapered optical elements

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5396350A (en) * 1993-11-05 1995-03-07 Alliedsignal Inc. Backlighting apparatus employing an array of microprisms
US5598281A (en) * 1993-11-19 1997-01-28 Alliedsignal Inc. Backlight assembly for improved illumination employing tapered optical elements

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8742406B1 (en) 2011-02-16 2014-06-03 Iowa State University Research Foundation, Inc. Soft lithography microlens fabrication and array for enhanced light extraction from organic light emitting diodes (OLEDs)

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