Illumination – Plural light sources – Particular wavelength
Reexamination Certificate
1999-05-20
2001-07-10
Husar, Stephen (Department: 2875)
Illumination
Plural light sources
Particular wavelength
C362S235000
Reexamination Certificate
active
06257737
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a luminaire having a reflector which mixes light from a multi-color array of LEDs, and more particularly to a low-profile luminaire which generates white light from a linear array of LEDs.
A standard low profile luminaire for mounting in a ceiling employs tubular discharge lamps having fluorescent coatings which determine the spectra of emitted light. The lamps generally are not dimmable, and the user has no control over the color temperature.
An array of LEDs in each of a plurality of colors offers the possibility of creating a luminaire in which the color temperature may be controlled at any power level, thereby enabling a lamp which is dimmable and emits a uniformly white light at any power level.
The English abstract of JP-A-06 237 017 discloses a polychromatic light emitting diode lamp having a 3×3 array of light emitting diodes of two types, a first type having elements for emitting red light and blue light, and a second type having elements for emitting red light and green light. The stated object is to mix colors so that the mixed color would be recognized as the same color in any direction, but there are no optical provisions to facilitate mixing. It is simply a two-dimensional array of LEDs in a lamp case filled with resin, which would do little more than provide some diffusion.
U.S. application Ser. No. 09/277,645, which was filed on Mar. 26, 1999, discloses a luminaire having a reflector which mixes light from a multi-color array LEDs. The array is arranged in the entrance aperture of a reflecting tube which preferably flares outward toward the exit aperture, like a horn, and has a square or other non-round cross section. The object is to produce a collimated beam of white light in the manner of a spotlight. However the design is unsuitable for a low-profile luminaire for general diffuse illumination.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a low-profile luminaire which produces white light from a multi-color array of LEDs, plus the ability to control and vary color temperature, at full power and dimmed.
The luminaire according to the invention utilizes a linear array of light injectors, including at least one light injector in each of a plurality of colors, typically red, green, and blue. Each injector has an LED in the respective color, and design optics for confining the emitted light within a cone having semi-angle &thgr;
s
. The array is parallel to the y-axis of an x-y-z coordinate system, arranged so that substantially all of the emitted light is emitted in the positive x and z directions.
A reflector situated beside the array of light injectors has a shape defined by a curve in the x-z plane in the positive x and z directions. The surface is formed by a projection of the curve parallel to the y-axis, and is arranged to receive substantially all of the light within the semi-angles &thgr;
s
of the injectors in the array.
A luminaire according to the invention offers the advantage of adjustable color temperature, because the power to the LEDs in each color of the array may be controlled individually. Likewise, the luminaire is fully dimmable, as the power to the different color LEDs may be controlled in concert.
The preferred luminaire also has two plane mirrors parallel to the x-z plane at the ends of the surface. Their purpose is to contain and redirect light from the injectors and the main reflector either to the main reflector or to the exit aperture.
The reflector preferably has a Lambertian surface, which is a diffusing surface for which the intensity of reflected radiation is substantially independent of direction (a perfectly diffusing surface is a Lambert surface). A phosphor powder coating can yield 95-99% reflection, while a brushed aluminum surface can yield 75% reflection. The surface may have partially specular reflectivity, so that it has partially directional reflected light. Such a luminaire could serve as a wall sconce where a portion of the light is directed at the floor for walking illumination while the rest of the light gives general diffuse illumination.
The luminaire preferably also includes a cover plate which provides mechanical protection for the main reflector, and defines the exit aperture. This plate may be transparent, or may provide any desired amount of diffusion. It may be designed as a lens which cooperates with a reflector having a non-uniform intensity.
Note that the rectangular coordinate system used herein to define the geometry of the luminaire is arbitrarily assigned, as it could be to any other system. However, it is conventional in the United States, for optical apparatus, to show light transmitted in the negative z-direction, from positive to negative.
REFERENCES:
patent: 5222795 (1993-06-01), Hed
patent: 5642933 (1997-07-01), Hitora
patent: 5921652 (1999-07-01), Parker et al.
patent: 4237107A1 (1994-05-01), None
JP 6-237017, “Polychromatic Light Emitting Diode Lamp”, Abstract.
Herman Stephen
Marshall Thomas M.
Pashley Michael D.
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