Etendue-squeezing illumination optics Number:7,520,641 from the United States Patent and Trademark Office (PTO) owispatent

Title: Etendue-squeezing illumination optics

Abstract: In some embodiments, an apparatus for use generating illumination is provided that comprises a reflective base, a first light source positioned proximate the reflective base, and a reimaging reflector positioned partially about the first light source, where a percentage of light emitted from the first light source is reflected from the reimaging reflector to the reflective base adjacent the first light source establishing a first real image. The reimaging reflector can further comprise a first sector of a first ellipsoid and a second sector of a second ellipsoid, where the first and second sectors establish the first and a second real image. Further embodiments provide a lens that includes a reimaging reflector that receives light and reflects the light establishing a first real image. The reimaging reflector can further comprise a plurality of sectors that reflect light to establish first and second real images.

Patent Number: 7,520,641 Issued on 04/21/2009 to Minano,   et al.

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Inventors:	Minano; Juan C. (Madrid, ES), Benitez; Pablo (Madrid, ES), Sun; Yupin (Yorba Linda, CA), Parkyn; William A. (Lomita, CA), Alvarez; Roberto (South Pasadena, CA), Falicoff; Waqidi (Newport Beach, CA)
Assignee:	Light Prescription Innovators, LLC (Altadena, CA)
Appl. No.:	12/119,039
Filed:	May 12, 2008

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Related U.S. Patent Documents

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	Application Number	Filing Date	Patent Number	Issue Date
	10772088	Feb., 2004	7377671
	60445059	Feb., 2003

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Current U.S. Class:	362/297 ; 362/346; 362/347; 362/507; 362/514; 362/545
Current International Class:	F21V 7/00 (20060101)
Field of Search:	362/297,346,518,241,235,240,341,347,800,555,516,545,459,507,514,517

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References Cited [Referenced By]

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U.S. Patent Documents

3746853	July 1973	Kosman et al.
4868723	September 1989	Kobayashi
5471371	November 1995	Koppolu et al.
6554455	April 2003	Perlo et al.
6773143	August 2004	Chang
6846100	January 2005	Imazeki et al.
7347599	March 2008	Minano et al.
7377671	May 2008	Minano et al.
2004/0145910	July 2004	Lisowski

Primary Examiner: Choi; Jacob Y
Attorney, Agent or Firm: Lebens; Thomas F. Sinsheimer Juhnke Lebens & McIvor, LLP

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Parent Case Text

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PRIORITY CLAIM

This application is a continuation of application Ser. No. 10/772,088, filed Feb. 3, 2004, entitled ETENDUE-SQUEEZING ILLUMINATION OPTICS, which claims the benefit of U.S. Provisional Application No. 60/445,059, file Feb. 4, 2003, entitled ETENDUE-SQUEEZING ILLUMINATION OPTICS, both of which are incorporated herein by reference in their entirety.

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Claims

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What is claimed is:

1. An apparatus for use in generating illumination, comprising: a first light source; a generally planar reflective base positioned adjacent to and extending away from the first light source; and a reimaging reflector positioned separated from the first light source and partially surrounding the first light source, where the reimaging reflector extends from the generally planar reflective base to partially reflectively surround the first light source, where a first percentage of light is emitted from the first light source in a first solid angle and does not strike the reimaging reflector, and a second remaining percentage of light emitted from the first light source is reflected from the reimaging reflector to the generally planar reflective base and is further reflected from the generally planar reflective base to be directed into substantially a same solid angle as the first solid angle of the first percentage of light emitted from the first light source thereby achieving etendue squeezing of the first light source.

2. The apparatus of claim 1, wherein the second percentage of light is approximately half of the light emitted from the first light source, where the reimaging reflector reflects at least a portion of the second percentage of light to the reflective base adjacent the first light source, where the portion of the second percentage reflected to the reflective base defines a first real image of the first light source adjacent the first light source such that the reflective base reflects the light of the first real image into substantially the first solid angle.

3. The apparatus of claim 2, wherein that the first light source and the adjacent first real image define a virtual light source thereby reducing a solid angle of light emissions without substantially increasing etendue of the first light source.

4. The apparatus of claim 3, wherein the reimaging reflector is generally a quarter ellipsoid with a first focus positioned on the first light source and a second focus positioned proximate the first light source at a position of the first real image adjacent the first light source such that the second focus is further positioned at a distance below the reflective base approximately equal to twice a height of a light emitting surface of the first light source from a reflective surface of the reflective base.

5. The apparatus of claim 1, wherein the reimaging reflector is approximately quarter-spherical and comprises a first reflective surface defined by a first sector of a first prolate ellipsoid and a second reflective surface defined by a second sector of a second prolate ellipsoid, where the first and second reflective surfaces are adjacent and joined along a first axis aligned with the first light source, where a first portion of the second percentage of the light reflected from the reimaging reflector is reflected from the first reflective surface to the reflective base adjacent the first light source defining a first real image of the first light source adjacent the first light source on a first side of the first light source such that the reflective base reflects the light of the first real image into substantially the first solid angle, and a second portion of the second percentage of the light reflected from the reimaging reflector is reflected from the second reflective surface to the reflective base adjacent the first light source establishing a second real image of the first light source adjacent the first light source at a second side of the first light source opposite the first side of the first light source and separated from the first real image by the first light source, such that the reflective base reflects the light of the second real image into substantially the first solid angle.

6. The apparatus of claim 5, wherein the first and second real images are aligned with the first light source along a second axis that is about perpendicular to the first axis such that the aligned first light source, the first real image and the second real image define a virtual source having a surface area that is at least twice a surface area of the first light source.

7. The apparatus of claim 5, wherein the first reflective surface of the reimaging reflector is defined by the first ellipsoid having first and second foci, and the second reflective surface of the reimaging reflector is defined by the second ellipsoid having third and fourth foci; the first reflective surface is positioned relative to the first light source such that the first focus is positioned on the first light source and the second focus is positioned to the first side of the first light source proximate the first light source at a position of the first real image; and the second reflective surface is positioned such that the third focus is positioned on the first light source and the fourth focus is positioned to the second side of the first light source proximate the first light source at a position of the second real image.

8. The apparatus of claim 1, wherein the reimaging reflector comprises four sectors distributed along an axis aligned with the first light source where each of the four sectors are defined by one of four prolate ellipsoids, where a first portion of light reflected from the reimaging reflector is reflected by first and second sectors of the reimaging reflector to the reflective base at a first side of the first light source establishing a first real image of the first light source, and where a second remaining portion of light reflected from the reimaging reflector is reflected by third and fourth sectors of the reimaging reflector to the reflective base adjacent the first light source on a second side of the first light source establishing a second real image of the first light source adjacent the first light source, such that the reflective base reflects the light of the first and second real images.

9. The apparatus of claim 1, further comprising: a tailored free-form exit face positioned such that the first percentage of light emitted into the first solid angle from the first light source and the second percentage of light reflected by the reimaging reflector and reflective base is emitted from the exit face establishing an output illumination that meets a predefined prescription.

10. The apparatus of claim 1, further comprising: an optical system wherein the first light source is positioned proximate the optical system such that the optical system receives the light at substantially the first solid angle as emitted from the first light source and reflected from the reimaging reflector and the reflective base.

11. The apparatus of claim 10, wherein the optical system comprises the reimaging reflector, and a cavity in which the first light source is positioned.

12. The apparatus of claim 11, wherein the lens further comprises: first reflective surface positioned to receive the light at substantially the first solid angle as emitted from the first light source and reflected from the reimaging reflector and the reflective base; a reflector array positioned to receive and reflect light reflected from the first reflective surface; a mirrored surface positioned to receive and reflect reflected light from the reflector array; and an output surface through which the light reflected by the mirrored surface is emitted.

13. The apparatus of claim 10, wherein the optical system comprises a collimator that directs the light received at substantially the first solid angle as emitted from the first light source and reflected from the reimaging reflector and the reflective base into a collimated output beam.

14. The apparatus of claim 13, wherein the collimator comprises a totally internally reflecting (TIR) lens positioned proximate the first light source opposite from the reimaging reflector such that the TIR lens receives the light at substantially the first solid angle as emitted from the first light source and reflected from the reimaging reflector and the reflective base.

15. The apparatus of claim 14, wherein the TIR lens is a decentered lens comprising an exit face, a central refractive lens, grooved facets having entry faces to receive the light, and totally internally reflecting faces positioned relative to the grooved entry faces to receive the light entering the lens from the entry faces of the grooved facets and to reflect the received light to the exit face.

16. The apparatus of claim 14, wherein the TIR lens comprises a decentered generally rectangular TIR lens having dimensions of a rectangular section of length defined according to a defining complete circular TIR lens extend from a center to a peripheral edge of the defining complete circular TIR lens.

17. The apparatus of claim 13, wherein the collimator comprises a semicircular refractive, reflexive and internal reflection (RXI) lens positioned adjacent the light source to receive the light at substantially the first solid angle as emitted from the first light source and reflected from the reimaging reflector and the reflective base, and to emit the collimated beam.

18. The apparatus of claim 10, further comprising: a first additional reimaging reflector, a second additional reimaging reflector and at least an additional planar reflective surface, where the first additional reimagining reflector is positioned relative to the first light source to receive at least a first portion of the light emitted from the first light source at substantially the first solid angle and reflects the first portion of light to the additional planar reflective surface to be reflected into a second solid angle, the second additional reimagining reflector is positioned relative to the first light source to receive at least a second portion of the light emitted from the first light source at substantially the first solid angle and reflects at least a fraction of the second portion of light to the additional planar reflective surface to be reflected into the second solid angle.

19. The apparatus of claim 18, wherein the first and second additional reimaging reflectors comprise an ellipse cotangent to a confocal parabola with the second additionally reimaging reflector positioned about the first additional reimaging reflector.

20. The apparatus of claim 18, wherein the first and second additional reimaging reflectors comprise reflective surfaces comprising an ellipse segment cotangent to a confocal parabola segment with the confocal parabola segment and the ellipse segment both having a common axis of revolution and meeting with a same tangent.

21. The apparatus of claim 1, further comprising: a first luminaire comprising the a first light source, the generally planar reflective base and the reimaging reflector; a second luminaire comprising: a second light source; an additional generally planar reflective base positioned adjacent to and extending away from the second light source; and an additional reimaging reflector positioned separated from the second light source and partially surrounding the second light source, where the reimaging reflector extending from the generally planar reflective base to partially reflectively surround the second light source, where a first percentage of light is emitted from the second light source in a third solid angle and does not strike the additional reimaging reflector, and a second remaining percentage of light emitted from the second light source is reflected from the reimaging reflector to the additional generally planar reflective base and is further reflected from the additional generally planar reflective base to be directed into substantially a same solid angle as the third solid angle of the first percentage of light emitted from the second light source thereby achieving etendue squeezing of the second light source.

22. An apparatus for use in generating an illumination, comprising: a first off-center etendue squeeze imaged light source; and an optical system optically coupled with the first off-center light source such that the optical system receives the light emitted from the first off-center light source; wherein the first off-center light source comprises: a first reflective base; a first light source positioned on the first reflective base; and a first generally quarter spherical reimaging reflector optically aligned with the first light source, extending from the first reflective base and partially surrounding the first light source, where the first light source emits a first percentage of light such that it does not strike the first reimaging reflector and directs a second percentage of light at the first reimaging reflection, wherein the first reimaging reflector comprises a generally ellipsoidal reflective surface opposed to the first light source to reflect at least a portion of the second percentage of light emitted from the first light source to the first reflective base defining a first real image of the first light source adjacent the first light source, where the first reflective base reflects the light of the first real image away from the first reimaging reflector generally in alignment with the first percentage of light emitted from the first light source.

23. The apparatus of claim 22, further comprising: a second off-center etendue squeeze imaged light source optically coupled with the optical system such that the optical system received the light emitted from the second off-center light source; wherein the second off-center light source comprises: a second reflective base; a second light source positioned on the second reflective base; and a second generally quarter spherical reimaging reflector optically aligned with the second light source, extending from the second reflective base and partially surrounding the second light source, where the second light source emits a first percentage of light such that the first percentage of light emitted from the second source does not strike the second reimaging reflector and directs a second percentage of light at the second reimaging reflection, wherein the second reimaging reflector comprises a generally ellipsoidal reflective surface opposed to the second light source to reflect at least a portion of the second percentage of light emitted from the second light source to the second reflective base defining a first real image of the second light source adjacent the second light source, where the second reflective base reflects the light of the first real image of the second light source away from the second reimaging reflector generally in alignment with the first percentage of light emitted from the second light source.

24. The apparatus of claim 23, wherein the optical system comprises a totally internally reflecting (TIR) lens positioned proximate the first and second off-center light sources such that the TIR lens receives the first percentage of light from the first and second light sources and the light of the first real images of the first and second light sources reflected by the first and second reflective bases, respectively.

25. The apparatus of claim 24, wherein the TIR lens comprises an exit face, grooved facets having entry faces to receive the light, and totally internally reflecting faces positioned relative to the grooved entry faces to receive the light entering the lens from the entry faces of the grooved facets and to reflect the received light to the exit face.

26. The apparatus of claim 22, wherein the optical system comprises a semicircular refractive, reflexive and internal reflection (RXI) lens positioned adjacent the light source to receive the first percentage of light from the first light source and the light of the first real image of the first light source reflected by the first reflective base, and to emit a collimated beam.

27. The apparatus of claim 22, wherein the first off-center light source comprises a second reimaging reflector, a third reimaging reflector and a second planar reflective surface, where the second reimagining reflector is positioned relative to the first light source to receive at least a first portion of the light emitted from the first light source and reflects the first portion of light to the second planar reflective surface such that the second planar reflective surface reflects the first portion of light, the third reimagining reflector is positioned relative to the first light source to receive at least a second portion of the light emitted from the first light source and reflects at least a fraction of the second portion of light to the second planar reflective surface such that the second planar reflective surface reflects the fraction of the second portion of light.

28. The apparatus of claim 27, wherein the second and third reimaging reflectors comprise an ellipse cotangent to a confocal parabola with the third reimaging reflector positioned about the second reimaging reflector.

29. The apparatus of claim 27, wherein the second and third reimaging reflectors comprise reflective surfaces comprising an ellipse segment cotangent to a confocal parabola segment with the confocal parabola segment and the ellipse segment both having a common axis of revolution and meeting with a same tangent.

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Description

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TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to optical illumination lenses, and more particularly to etendue-squeezing primary source-optics utilizing either commercially available packaged LEDs or immersive-lens designs suitable for LEDs mounted in the chip-on-board fashion.

BACKGROUND OF THE INVENTION

Among the more challenging illumination tasks for solid-state lighting is forward lighting meeting predefined criteria, such as forward lighting for vehicles, utilizing non-thermal light sources, e.g. light-emitting diodes (LEDs). The lifetime of LEDs in the vibration environment of a ground vehicle is far greater than that of conventional incandescent sources. Some recently developed white LEDs are surpassing the significant 100-lumen luminosity threshold, marking the feasibility of fulfilling that most difficult of all forward vehicle lighting tasks, automotive-headlight intensity standards. Peak intensities in the tens of thousands of candela, however, can not be achieved with LEDs alone.

Beyond efficiency, moreover, automotive design pressures for highly compact forward-lighting systems pose severe tradeoffs of device size against attainment of sharp intensity cutoffs required to minimize glare to other vehicles. Prior LED optics employ unacceptable device size when compared to competing incandescent-source designs such as projector lamps.

SUMMARY OF THE INVENTION

The above needs are at least partially met through provision of the method, apparatus, and system for using generating illumination that, in some embodiments, utilize etendue squeezing described in the following detailed description, particularly when studied in conjunction with the drawings. In some embodiments, an apparatus for use generating illumination is provided that comprises a reflective base, a first light source positioned proximate the reflective base, and a reimaging reflector positioned partially about the first light source, where a percentage of light emitted from the first light source is reflected from the reimaging reflector to the reflective base adjacent the first light source establishing a first real image of the first light source adjacent the first light source such that the reflective base reflects the light of the first real image. The reimaging reflector can, in some embodiments, be generally a quarter ellipsoid with a first focus positioned on the first light source and a second focus positioned proximate the first light source at a position of the first real image and below the reflective base at a height below a surface of the reflective base equal to a height of a light emitting surface of the first light source from the surface. In some embodiments, the reimaging reflector can further comprise a first sector of a first prolate ellipsoid and a second sector of a second prolate ellipsoid, where the first and second sectors joined along an axis.

Some alternative embodiments provide apparatuses for use in transmitting light. These apparatuses can comprise a first etendue squeeze light source comprising a first reimaging reflector positioned partially about the first light source, where a percentage of light emitted from the first light source is reflected from the first reimaging reflector establishing a first real image of the first light source adjacent the first light source. Some embodiments further include a second etendue squeeze light source. A luminaire is often included in many embodiments, where the luminaire comprises first and second reflective surfaces, where the first source is positioned proximate an edge of the second reflective surface to direct light onto the first reflective surface, and the second source is positioned proximate an edge of the first reflective surface to direct light onto the second reflective surface. The first and second sources can each further include a free-form lens positioned to receive light from the respective light source and the respective first and second real images, such that the light passes through the free-form lens at solid angle subtended by dimensions of the corresponding first and second reflector surfaces. In some embodiments, a luminaire is included that is generally boat-shaped, with first and second reflective surfaces being generally paraboloidal, with the first source being positioned at a focal point of the paraboloidal first surface and the second source being positioned at a focal point of the paraboloidal second surface.

Further embodiments provide a lens that includes a reimaging reflector positioned to receive a percentage of a total light received by the lens. The reimaging reflector reflects the percentage of light establishing a first real image that is further directed away from the reimaging reflector and into the lens. The reimaging reflector can be generally ellipsoidal in shape. Additionally and/or alternatively, the reimaging reflector can further comprise a plurality of sectors where each sector is defined by a prolate ellipsoid, such that a first sector reflects a first sub-percentage of the percentage of light establishing the first real image, and a second sector reflects a second sub-percentage of the percentage of light establishing a second real image that is further directed away from the reimaging reflector and into the lens. Some lens embodiments further comprises a first etendue-squeezing reflector and a second etendue-squeezing reflector both positioned to receive a percentage of the total light received. The first etendue-squeezing reflector can have a profile comprises a parabola segment and an ellipse segment, where the parabola segment and the ellipse segment both have a common axis of revolution and meeting with the same tangent.

Some preferred embodiment provide for a method of manufacturing an optical device. The method can comprise defining a first position for placement of an optical source; and defining a first prolate paraboloidal surface further comprising defining a first focus at the first position and defining a second focus at a second position a first distance from the first position in a first direction, providing a three-dimensional representation of an optical source. The defining of the second focus can further include defining a plane relative to the optical source and the first position such that a second distance is defined in a second direction from the plane to an emitting surface of the optical source, and defining the second focus of the first paraboloidal surface at a third distance defined in a third direction from the plane to the second focus where the third distance is equal to the second distance such that the third direction is opposite the second direction.

Additional embodiments provide methods for manufacturing an optical device. These methods can comprises generating a two-dimensional representation of a plurality of entry surfaces and a plurality of corresponding reflective surfaces, and exit surface; rotationally sweeping the two-dimensional representation about a central axis providing a three-dimensional representation of the plurality of entry and corresponding reflective surfaces, and exit surface; and defining a cutout of the three-dimensional representation that extends from about a center of the three-dimensional representation at the central axis to a periphery of the three-dimensional representation providing a three-dimensional representation of an optical lens. Some embodiments additionally comprise defining an optical source for positioning proximate the central axis that further comprises: defining a first position for placement of an optical source; and defining a first prolate paraboloidal surface that includes defining a first focus at the first position, and defining a second focus at a second position a first distance from the first position in a first direction. The defining the optical source can further comprises defining a second prolate paraboloidal surface by defining a first focus of the second prolate paraboloidal surface at the first position, and defining a second focus of the second prolate paraboloidal surface at a third position a first distance from the first position in a second direction opposite the first direction.

A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description of the invention and accompanying drawings which set forth an illustrative embodiment in which the principles of the invention are utilized.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:

FIG. 1 depicts a simplified elevated view of a circular aperture that surrounds a centrally positioned light source;

FIG. 2 shows an elevated view of an aperture having a semicircular configuration with an area that is approximately equal to the area of the circular aperture of FIG. 1;

FIG. 3 depicts a rectangular aperture that has substantially the same area as the circular aperture of FIG. 1, but with a length that is about four times the radius of the circular aperture;

FIG. 4 shows a simplified block diagram of a linear array of multiple triangular luminaires with decentered, peripherally positioned, light sources;

FIG. 5 depicts the configuration of a prolate-ellipsoidal reimaging mirror with central LED;

FIG. 6 depicts the reimaging operation of this mirror;

FIG. 7 depicts a two-sector reimaging mirror;

FIG. 8 depicts is optical operation forming two images;

FIGS. 9 and 10 depict two views of a four-sector reimaging mirror;

FIG. 11 depicts a means of stray-light suppression;

FIG. 12 depicts a right-hand view of reimaging, showing that each source image has 25% of source etendue;

FIG. 13 depicts a left-hand view of reimaging;

FIG. 14 is an outline of a forward-lighting preferred embodiment meeting a low-beam prescription;

FIG. 15 shows a cross section of this preferred embodiment with its folded optical path;

FIG. 16 is a perspective rear view of this preferred embodiment;

FIG. 17 is a perspective front view of this preferred embodiment.

FIG. 18 is a cross section of a closely related but thicker preferred embodiment with a fluid-filled interior and one less fold in its path;

FIG. 19 is a perspective view of this preferred embodiment;

FIG. 20 depicts three pairs of low-beam and high-beam versions of this preferred embodiment, acting in concert with an identical pair to fulfill both prescriptions;

FIG. 21 is a top view of a semicircular lens with a reimaging reflector;

FIG. 22 is a bottom view of this lens, showing how its LED source is received;

FIG. 23 depicts an off-axis forward-lighting preferred embodiment meeting a fog-lamp prescription;

FIG. 24 is an end view of this embodiment, showing its circular symmetry and its linear lens;

FIG. 25 is a lateral view of one lens light-source module, slightly from above;

FIG. 26 is a lateral view of the same, slightly from below;

FIG. 27 is a schematic cross-section of the two reflectors depicted in FIGS. 25 and 26;

FIGS. 28-30 depict a decentered circular TIR lens with an etendue-squeezed light source;

FIGS. 31-33 depict a decentered rectangular TIR lens with an etendue-squeezed light source;

FIG. 34 depicts a two-sector boat-shaped luminaire;

FIG. 35 depicts the collimating action of one sector of the luminaire of FIG. 34;

FIG. 36 shows a faceted version of FIG. 34;

FIG. 37 shows a trisymmetric version of FIG. 34;

FIG. 38 shows a quadrisymmetric version of FIG. 34;

FIG. 39 is the deflection diagram for a source of FIG. 34;

FIG. 40 depicts the deflection diagram similar to that of FIG. 39 demonstrating horizontal limit-angles;

FIG. 41 depicts the deflection diagram similar to that of FIGS. 39 and 40 showing vertical limit-angles;

FIG. 42 is a cutaway of the source of FIG. 34;

FIG. 43 shows the entire free-form lens of FIG. 42 without cutaway;

FIG. 44 shows a semi-transparent end view of the TIR boat lens with optical sources similar to the sources depicted in FIGS. 42-43; and

FIG. 45 shows a view from below of a boat lens similar to that of FIG. 44 utilizing sections of a circular TIR lens.

Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are typically not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A better understanding of the features and advantages of the present embodiments will be obtained by reference to the following detailed description of the invention and accompanying drawings, which set forth illustrative examples in the design of which the principles of the embodiments are utilized.

The present embodiments provide for apparatuses and methods for etendue squeezed light sources, as well as optics and/or luminaries that utilize the etendue squeezed light sources and are optimized through the use of the optics.

Some embodiments provide sources can be utilized to provide forward vehicle lighting, such as headlights for automobiles that satisfy some of the most challenging forward vehicle-lighting prescriptions. Present embodiments can further utilize light-emitting diodes (LED) as well as solid-state chip-on-board light sources in general. Moreover, the preferred embodiments disclosed herein can include configurations comprising separately molded luminaires and lenses in which the solid-state chip-on-board light sources are immersed.

The present embodiments relate generally to optical illumination lenses, and some preferred embodiments utilize immersive lens designs suitable for LEDs mounted in the chip-on-board fashion. Immersion refers to the practice of surrounding an LED with a transparent dielectric. This can increase the light-extraction efficiency over the operation of the LED in air, by decreasing Fresnel reflectance and reducing the extent of total internal reflection within the chip. The present embodiments furthermore can utilize tailored free-form folded optics to meet particular prescriptions, such as prescriptions for forward vehicular lighting. The present embodiments can be employed in illumination lenses utilizing a novel optical principle, that of etendue squeezing, for example through ellipsoidal reimaging as fully described below.

The immersive lens of the LEDs and/or optics utilized with the LEDs can be formed from substantially any relevant material, such as plastics, polymers, glass, silicon and other such material. Plastic optics can be formed through injection molding of transparent polymeric plastics such as acrylic, polycarbonate, polyarylate, cyclo-olefins, and other similar materials. The cyclo-olefins group, for example, can be used at high operating temperatures, for example at 161.degree. C., as exemplified by a cyclo-olefin based product Zeonor 1600R, produced by Zeon Corporation of Japan. Optical injection molding is also possible with silicones, while low-pressure molding is possible with glass.

The terms used herein of light and illumination are not restricted to the visible wavelength range of 380 to 750 nanometers, but can additionally encompass the entire ultraviolet and infrared range that is amenable to geometric optics. In these non-visible ranges, the present embodiments have similar technological benefits to those it provides in the visible range. Further, the present embodiments can be equally applied to near-ultraviolet LEDs, which may be primary light sources for exciting visible-light phosphors.

In the near-infrared regime (e.g., 700-1100 nm), night-vision illuminators based on the present embodiments can be implemented to use commercially available near-infrared LEDs as light sources for lenses that can be molded of the above-mentioned materials, in the same manner as for visible-light illuminators.

Previous LEDs were generally too fragile to withstand the rigors of the injection-molding process. Recently, however, new chip-on-board designs have eliminated the delicate gold-wire leads that could not withstand injection molding. Now it becomes possible to precisely mold miniature optical elements adjacent to an LED chip. In some embodiments this ability to precisely mold optical elements adjacent to LED chips is utilized.

Government and industry standards for vehicular forward lighting involve a high-intensity hot-spot with a broader and less intense overall pattern that gradually extends sideways but must fall off very rapidly above the horizontal plane. In addition, headlights must have high-beam capability, which requires even higher intensity levels in the hot-spot. Attempts to fulfill such prescriptions through previous LED optics involved configurations that are too thick for injection molding to be suitably produced and/or implemented. Alternatively, the present embodiments provide luminaire designs with the device size greatly reduced compared with previous device sizes that were necessary to fulfill forward-lighting prescriptions.

The present embodiments configure and/or arrange light sources to establish a high-performance etendue light source and/or optics. A conserved quantity of a bundle of light rays, etendue, is the product of a bundle area and its projected solid angle. A solid angle, measured in steradians (sr), can be visualized as a piece of the sky, where a projected solid angle refers to a unit circle below the unit hemisphere on which solid angle is defined.

A solar concentrator makes a small solar image via its concentrated solar rays converging on its collector from over a much wider angle than the half-degree angular width of the Sun as its nearly parallel rays entered the concentrator. Conversely, a searchlight mirror transforms the omnidirectional emission of a small source into a large well-directed beam with narrow angular width. Both for concentrators and collimators, area and angle are traded off, but their product, etendue, generally cannot increase because it is an invariant property of any ray bundle, from the moment the bundle was created by the light source. By geometric necessity, etendue can only be reduced by removing rays from a bundle. The etendue concept can be considered generally analogous to the entropy concept in thermodynamics, where entropy according to the Second Law of thermodynamics never decreases.

Etendue is the phase-space volume of a bundle of light rays. If lateral coordinates x and y are defined across a device aperture .SIGMA., two angles can be defined according to a light ray passing through these axes. Ray-directions can be defined by variables p and q, defined according to the cosines of the above two angles, and as multiplied by a local refractive index n. Thus the dimensions of phase space are x, y, p, and q. Whether a bundle of rays is concentrated or collimated, its phase-space volume does not change.

The etendue can be determined for substantially any light source. For example, if a light source is defined by a square LED chip having an encapsulated dome with an index of refraction n, the etendue of this LED source can be given by: E=.pi.n.sup.2(D.sup.2+2DL), Eq. 1 where D is the width and L is the length of the LED. For example, if the LED source has a width D=2 mm, and height L=0.18 mm, and the LED is further encapsulated within a spherical dome (such as a dome made of a cyclic olefin copolymer) having an index of refraction n=1.53, and the LED is located on a planar mirror so that its side emission radiates into a full hemisphere, the etendue equals E=34.71 mm.sup.2-sr according to Equation 1.

Similarly, a circular collimator with a nominal diameter (e.g., a diameter of two inches, minus 1 mm for mounting), an optical radius R (for example, a radius R=24.5 mm) and that emits into air can provide an output beam, of half-angle .theta., that has an etendue defined according to: E=(A.sub.e)(.pi. sin.sup.2 .theta.), Eq. 2 where A.sub.e=.pi.R.sup.2 is the output area. If all of the source rays of the output bean exit within the half-angle .theta. of a system axis, the output etendue equals the source etendue, and the half-angle can be defined by:

.theta..times..pi..times..times. ##EQU00001## so that .theta.=4.4.degree. is the approximate minimum possible output half-angle, beyond which beam intensity would be generally zero. When luminaire intensity is non-uniform, however, this angle is called the telecentric approximation, since it often turns out to be close to the angle of half-maximum intensity. As such, the etendue can be defined as a volume in a four-dimensional phase space. The etendue can additionally and/or alternatively be defined according to a two-dimensional phase space with a light source specified by its width D and projected angle, which is given by twice the sine of the half-angle .theta.. The two-dimensional etendue can be represented as an area on the planar phase space defined according to: E.sub.2d=2n D sin .theta.. Eq. 4

This two dimensional representation of the etendue measure is useful when analyzing rotationally symmetric optics in terms of their diameter and average beam divergence. Commercially available LED chips are typically squares cut out of a wafer, whereas the rotational symmetry of a circular chip provides a direct comparison of a full 4-D etendue with 2-D etendue. A disc source of width D and height L, embedded in a medium of refractive index n, emits hemispherically so that .theta.=90.degree., giving 2-D etendue according to: E.sub.2d=n(2D+2L), Eq. 5 which results in a two dimensional etendue of 6.67 mm (where D=2 mm, L=0.18 mm and n=1.53, as in the example above). The corresponding minimum half-angle is defined according to:

.theta..times..times..times..times..times..times..times..times. ##EQU00002## which equals .theta..sub.2d=3.90.degree. in continuing the example above where R=24.5 mm. The discrepancy with slightly larger value above for a square chip can be reconciled by considering the four dimensional etendue of a rotationally symmetric disc source of diameter D and height L:

.pi..times..times..pi..times..pi..times..function..pi..times..times..times- . ##EQU00003## so that the etendue E=27.25 mm.sup.2-sr and the four dimensional half-angle .theta..sub.4d=3.90.degree..

The output beam of a collimator can be decomposed into elemental beamlets emitted from small patches of its output surface. The i.sup.th beamlet has etendue E.sub.i, so the total beam has etendue is defined by the summation:

.times..times. ##EQU00004##

One of the important aspects of the present embodiments is the varying shapes and angular sizes of these beamlets across the output surface of a luminaire. For example, an edge of a parabolic reflector or mirror that is the farthest from a source provides a narrower beamlet than more central positions on the reflector closer in proximity to the source. As such, the total output beam of a parabola can be defined as a collection of beamlets of different widths, but all being substantially parallel to the system axis. In the case of vehicular forward lighting, however, the narrower beamlets are typically directed so as to promote a rapid vertical cutoff.

Some present embodiments alternatively utilize de-centered collimator segments illuminated by etendue-squeezing source optics. The uses of these de-centered, etendue-squeezing sources are fully described below.

The United States Department of Transportation (DOT) utilizes a logarithmic definition of intensity gradient (G) at vertical angle .theta., according to the intensity values I(.theta.) and I(.theta.+0.1.degree.): G=log.sub.10 I(.theta.)-log.sub.10 I(.theta.+0.1.degree.). DOT regulation FMVSS 108 mandates G>0.13 for forward transmitting vehicular headlights. A gradient according the this mandate results in an intensity reduction or shrinkage equal to 10.sup.-0.13=0.741 for every 0.1 degree, a factor of about twenty smaller in only 1.degree. of elevation. To accomplish this, previous systems require luminaires to be big enough that its smallest beamlets could be used to meet this difficult standard, resulting in excessively large and impractical luminaries. Alternatively, some present embodiments employ etendue squeezing allowing for luminaries that are substantially more compact while still meeting the regulatory standards and manufacturer preferences in its prescription.

The present embodiments implement the etendue squeezing through one of at least two methods, and in some embodiments employ more than one squeezing method. In some embodiments the etendue squeezing produces non-circular beamlets with a narrow vertical extent. Such non-circular bundles are directed so as to achieve a high vertical intensity gradient. The thinness of some LED chips, particularly green, blue, and white LEDs based on gallium indium nitride, assist this effect through their oblique rays bearing a very thin and elongated chip-image. Some embodiments alternatively and/or additionally implement the etendue squeezing by shrinking the narrowest beamlets. The shrinking of the narrowest beamlets is achieved in some embodiments by de-centering a light source.

In previous devices, an omnidirectional light source is typically placed at the center of a luminaire. Alternatively, the present embodiments position a light source so that the light source is not centered with respect to the luminaire and in some embodiments position the light source at an edge of a luminaire. De-centering the light source lengthens the distance from the light source to the farthest point of the aperture, making the narrowest beamlet even narrower than would be achieved in previous devices. This de-centering and/or edge-placement additionally positions the source closer to the external environment, thereby reducing the thermal paths for removing the source's waste-heat.

Some embodiments additionally redirect portions of the source light to more completely utilize the source flux. For example, additional optical means are employed near the source so as to redirect what might be unused portions of the omnidirectional emission into the luminaire, as is discussed fully below. When placement of the source is at an edge of a luminaire, about half of the omnidirectional emission might be redirected and in some instances more than half depending on the positioning and configuration of the luminaire. In some preferred embodiments employing LED light sources, the dimensions of the optics employed in redirecting emissions are maintained to a minimum, for example, only a few times bigger than the LED source. Further, the redirecting device and/or optics can include a precisely predefined shape and have precise positioning relative to the source. Some embodiments utilize in-mold-chip-on-board features to implement the redirectional device and/or positioning relative to the source.

In some embodiments, a non-circular aperture is additionally utilized. The aperture can be altered from a circular configuration to accommodate the peripheral placement of the source and to lengthen the distance from the light source to the farthest point of the aperture narrowing the beamlet. For simplicity, implementation of off-center positioning of a source and/or the aperture re-shaping is hereinafter referred to as etendue squeezing, and is further elucidated below.

A further desired effect and/or desideratum for some lighting, such as vehicular lighting, is a compact configuration. Previous lighting devices often required long optical path lengths in order to meet exacting prescriptions. These long paths typically resulted in unacceptable device sizes. The present embodiments alternatively incorporate folded optics to provide increased path lengths while limiting the size of the lighting devices.

The present embodiments additionally can be configured to include freeform optical surfaces specifically configured to shape an output beam to both low- and high-beam automobile headlight patterns. As such, the present embodiments can utilize LED light sources to power any number of lighting devices, such as automotive headlights. Previous automotive headlights utilized incandescent sources that have much higher power consumption than the LED sources. Additionally, the present invention takes advantage of LED's much higher tolerance to vibration and shock, and much longer lifetimes, which can generally exceed the expected operating life of automobiles.

FIGS. 1-3 schematically depict simplified elevated views of three aperture shapes having substantially the same geometric area: a circular aperture 10, a semicircular aperture 13, and a rectangular aperture 16, respectively. Because their areas are substantially equal, the overall etendue of their output beams will typically be the same (assuming a similar source is employed). It is the narrowest beamlet, however, that is of interest to the present embodiments. The actual size of the sources shown in these diagrams places them within the purview of the small-angle approximation, whereby a small angle and its sine and tangent can be used interchangeably: sin .theta..about.<.theta..about.<tan .theta.. For example, at the .+-.7.5.degree. of beamlet 12, the sin(.theta.), .theta. and tan(.theta.) in radians equal 0.13053, 0.13090, and 0.13165, respectively, with a difference or an error of +0.6%/-0.3%. The resulting difference or error is even smaller for beamlets 15 and 18 of FIGS. 2 and 3, respectively. Further, the difference or error does not reach .+-.1% until the angle of the beamlet is about .theta.=14.degree..

FIG. 1 depicts a simplified elevated view of a circular aperture 10 that surrounds a centrally positioned light source 11. A beamlet 12 is defined by a pair of rays that span the distance from source 11 to the periphery of the aperture 10. The ratio of the radius of source 11 to that of the radius of the aperture 10 defines an angular semi-width of the beamlet 12 that is the narrowest beamlet from the luminaire. It is noted that for the sake of simplicity, FIGS. 1-3 do not show beamlets 12, 15, and 18 being redirected out of the plane of the paper, the direction of emission from the apertures 10, 13, and 16, respectively.

FIG. 2 shows an elevated view of an aperture 13 having a semicircular configuration with an area that is approximately equal to the area of the circular aperture 10 of FIG. 1. The distance from the source 14 to the periphery of the semicircular aperture 13, however, is about {square root over (2)} times greater than the distance 12 from the source 11 to the periphery of the circular aperture 10 of FIG. 1. The beamlet 15 is accordingly about {square root over (2)} times narrower in angle than the beamlet 12 of circular aperture 10 of FIG. 1.

Referring to FIG. 3, a rectangular aperture 16 is shown that has substantially the same area as circular aperture 10 of FIG. 1, but the length of the aperture 16 is about four times the radius of the circular aperture 10. The beamlet 18 is thus also about four times smaller in angular width than beamlet 12.

The de-centering of a light source relative to an aperture lengthens the distance from the light source to the farthest point of the aperture and provides for the reduced beamlet angular width. The reduced angular width provided by the off center positioning of the source allows, in part for the promotion of a rapid vertical cutoff. Additionally, the narrowed beamlet angular width can provide for a high vertical intensity gradient.

FIG. 4 depicts an array 1000 of equilateral generally triangular-shaped luminaires 1001, each with lensed light source 1002, which advantageously lie on an edge of the luminaries. By positioning the sources 1002 on an edge of the array, the tasks of conveying electric power to and removing waste heat from the sources are simplified.

Some preferred embodiments utilize edge-placement tactics and/or additionally redirect omnidirectional source-emissions to be redirected into a narrower solid angle subtended by an aperture from the source, to in part avoid wasting luminous flux. In utilizing a semi-circular aperture such as the aperture of FIG. 2, for example, the present embodiments redirect substantially all, and preferably all of the flux that would have been direction in a -Y direction to instead be redirected in the +Y direction and thereby into semicircular aperture 13.

This redirection can be achieved in some embodiments through the utilization of a mirror. For example, a vertically oriented planar mirror could be used, but such a flat mirror would preferably be positioned immediately adjacent to the source 14, to avoid a dark gap that might appear between the source and its adjacent image. A hemispheric mirror positioned to be centered on the source could be employed with sources that allowed free passage of those reflected rays avoiding dark gaps, and LEDs typically do not allow free passage of reflected rays.

In one preferred embodiment of the present invention, the redirection of light from the source can be implemented through an ellipsoid reflector, with non-imaging achieved by designing and position the ellipsoid with its focus at an edge of the source. The edge-ray principle of non-imaging optics utilized in the present embodiments advantageously strive to ensure that substantially all, and preferably all reflected source-rays appear to come from an image immediately adjacent to the source, even though a surface of an ellipsoid reflector itself is distant from the source.

FIG. 5 depicts a simplified schematic view of a portion of a prolate ellipsoid reflector 20, an LED chip 21, a substrate 22, and a cutaway view of a mirror or reflective base 23. The LED 21 and ellipsoid reflector 20 are positioned relative to each other such that a first focus F1 of the ellipsoid is positioned on the surface of chip 21, at a point (F1X,F1Y,F1Z) that is in some preferred embodiments on the edge of the LED, and a second focus F2 is positioned at a point (F2X,F2Y,F2Z). In some preferred embodiments, the ellipsoid reflector is configured and/or positioned relative to the source such that the second focus F2 is positioned to be below the mirror 23, and laterally displaced from the first focus F1 by a width W of the LED chip 21. The real image can be positioned such that a small safety gap or guard-distance .DELTA. can be included between the source and an adjacent real image of the source, which can be any sized gap, for example about 0.05 mm in some embodiments, depending on the size of the source, ellipsoid reflector, and other similar factors.

The surface of ellipsoidal mirror 20 can further be configured according to some design considerations to pass through a point P at (PX,PY,PZ). The size of ellipsoidal mirror 20 is relative to the size of the source 21 in achieving accurate reimaging. An ellipsoid center 24 lies midway between the first and second foci F1 and F2, with a center-to-focus distance c given by c=1/2 [(F1X-F2X).sup.2+(F1Y-F2Y).sup.2+(F1Z-F2Z).sup.2].

The location of surface point P fulfills the definition of an ellipse as the locus of points of constant sum 2a of the distances from it to each focus, where a is the semi-major axis, accordingly given by:

.times..times..times..times..times..times..times..times..times..times..tim- es..times..times..times..times..times..times..times..times..times..times..- times..times..times..times. ##EQU00005## A Semi-minor axis b is given by b= {square root over ((a.sup.2-c.sup.2)}, completing the specification of the ellipsoid by the coordinates of the foci and of a single point on its surface. Prolate ellipsoid 20 is delineated by polar grid 25, which is aligned with axis defined by a line joining foci F1 and F2.

Still referring to FIG. 5, the ellipsoid is configured such that the second focus F2 is defined to have a depth below the mirror 23 that is twice the height at which the first focus F1 above the mirror. This is so that the real image of the chip, as formed by ellipsoid 20, is at same height as the chip itself. In some embodiments, the second focus F2 can also be shifted slightly further away from the LED chip 21 so that there is a small gap between the chip and its real image, in an attempt to avoid reflected rays from hit the chip.

Similar etendue squeezing can be achieved with other shaped sources such as rectangular, oval and substantially any other shape with the source off center and appropriate reflectance to generate reimaging and achieve the desired illumination pattern. As described above with reference to FIG. 3, a source can be rectangular with the LED positioned off center.

FIG. 6 depicts the reimaging action of prolate ellipsoidal reflector 20 on a percentage of emission 26 from chip 21. A real image 27 is formed on mirror 23, adjacent to chip 21, of the percentage of the light emitted from the light source 21 that impinges the reimaging reflector 20. The real image 27 thereafter acts as a virtual source equivalent to another chip at that location. The percentage of rays striking reflector 20 would have otherwise continued outward, but are now recruited into image 27. A difficulty arises in some implementations, however, as shown by rays 26b, which can be seen to intercept chip 21 on their way to image 27. Some present embodiments alleviate this problem by utilizing a two-sector ellipsoid reflector.

FIG. 7 depicts a simplified elevated view of a two-sector reimaging mirror 30 according to some embodiments. Reimaging mirror 30 includes a first or left-half prolate ellipsoid 30L and second or right-half prolate ellipsoid 30R, each configured similarly in specification and in some embodiments substantially identical in specification, to ellipsoid 20 of FIG. 2 and FIG. 2A. Right-half prolate ellipsoid is centered at point 30Rc, while left-half prolate ellipsoid 30L has a corresponding center point, not shown, on the other side of source 31. The two sectors abut and are joined along centerline 30CL and share defining point 30P. LED chip 31, substrate 32, and mirror or reflective base 33 are similar to those described above in relation to FIG. 2.

FIG. 8 depicts the reimaging action of two-sector ellipsoidal reflector 30 of FIG. 3. LED chip 31 produces emission and a percentage of the emissions 36 are directed toward the reimaging reflector 30. A sub-percentage of the emissions are reimaged by right-side reimaging reflector or mirror 30R providing a right-side real image 37R and another sub-percentage of the emissions are reimaged by left-side reimaging mirror 37L providing a left-side real image 37L. In utilizing the two ellipsoid halves 30R and 30L, the present embodiments solve the problem of rays impacting the source as described above in relation to FIG. 2A. It can also be seen that right-side image 37R radiates into the front-right quadrant of directions. Thus images 37R, and 37L equally, each bear approximately 25% of the etendue of light source 31, as is fully discussed below, for example with respect to FIG. 11 below. However, the amount reflected by the ellipsoidal reflector depends on the size of the ellipsoidal and the placement of the source relative to the ellipsoidal.

FIGS. 9-10 depict simplified schematic diagrams