Illumination – Plural light sources – With modifier
Reexamination Certificate
1999-09-24
2001-07-24
O'Shea, Sandra (Department: 2875)
Illumination
Plural light sources
With modifier
C362S241000, C362S244000, C362S245000, C362S247000, C362S327000, C362S331000, C362S348000
Reexamination Certificate
active
06264346
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to apparatus for mixing light from different color lamps, in particular to produce white light.
The standard light source for small to moderate size narrow beam lighting for accent lighting and general illumination is the incandescent/halogen bulb, such as a PAR (parabolic aluminized reflector) lamp. These sources are compact and versatile, but they are not very efficient. A given lamp operates at a given color temperature for a fixed power, and while they are dimmable, the color temperature shifts with applied power according to the blackbody law, which may or may not be the variation that the user desires.
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.
U.S. application Ser. No. 09/338,997 filed Jun. 24, 1999 discloses apparatus having beam splitters which mix light from an array of different color LEDs. A square array of four LEDs is arranged so that each pair emits light toward an opposite side of a semi-reflective layer at 45°, and a pair of mixed light beams is transmitted from each side at 45°. A second identical stage mixes the two pairs of mixed beams so that four identical mixed beams emerge in parallel as white light. The semi-reflective surface may be approximated by a checkerboard pattern of fully reflective and fully transmissive areas which are sufficiently small that emerging sub-beams cannot be resolved and appear to be fully mixed.
SUMMARY OF THE INVENTION
The invention, like the prior art discussed above, has for its object to mix light from different colored LEDs, e.g. red, green, and blue, to produce white light. The apparatus according to the invention mixes light beams input from up to four different sources, provided that the sources have the same initial beam profiles.
The invention takes a different approach from the prior art. According to the invention, a faceted surface has a plurality of parallel first facets alternating with a plurality of parallel second facets to form a sawtooth pattern. The facets are arranged so that a first light beam incident on the first facets and parallel to the second facets will be deflected by the first facets as a plurality of spaced apart first sub-beams, and so that a second light beam incident on the second facets and parallel to the first facets will be deflected by the second facets as a plurality of spaced apart second sub-beams. The first sub-beams alternate with the second sub-beams, and all sub-beams are parallel.
According to a first embodiment, the faceted surface is a first. reflective surface, each pair of first and second facets having an angle of 120° therebetween, the first and second light beams each having an angle of incidence of 30° to the normals of the facet surfaces. All sub-beams are therefore reflected at 30° to these normals and emerge in parallel. The output beams have the same angular distribution as the input beams. Therefore, if the input color beams are highly collimated, the output white beams will also be highly collimated.
An identical second reflective surface may be arranged to reflect third and fourth light beams as alternating parallel sub-beams. A third substantially identical surface has first facets which receive the mixed sub-beams from the first reflective surface, and second facets which receive the sub-beams from the second reflective surface. The third reflective surface reflects all of the sub-beams in parallel.
According to a second embodiment, the faceted surface is a refractive surface which refracts each input beam into spaced apart parallel sub-beams. For two light sources which transmit light parallel to the first and second facets, the first sub-beams alternate with the second sub-beams in an overlapping area. According to a preferred variation of the second embodiment, the faceted surface is a second refractive surface, and a first refractive surface is provided parallel to the second refractive surface. For light sources which transmit parallel input beams perpendicular to the first refractive surface, the facets of the first surface refract each input beam into a pair of diverging first and second beams which are incident on respective first and second facets of the second refractive surface. For each pair of light beams incident on the first refractive surface, 50% of the first sub-beams alternate with 50% of the second sub-beams. For a linear array of pairs, this alternation or overlap will increase with the number of pairs in the array.
The first and second refractive surfaces are preferably formed on opposite sides of a first solid refractive splitting element. For a square array of light sources, an identical second splitting element is arranged parallel to the first element and rotated 90°. Where a 6×6 array of light sources is provided, a 7×7 array of sub-beams will be output with a 5×5 array of mixed sub-beams.
According to all embodiments the period (peak to peak spacing) of the facets is sufficiently small that the individual sub-beams of color cannot be resolved by an observer. The resulting white light is thus an apparent white light, much the same as a white field on a color CRT screen, which is actually a mixture of red, green, and blue. The two stage mixers according to the invention typically produce red/green and blue/green mixed beams in the first stage, and white beams approximated by a mixture of red/green and blue/green beams in the second stage.
The beam mixing apparatus of the present invention may offer manufacturing efficiencies which render it more suitable than the prior art for some applications.
REFERENCES:
patent: 1193999 (1916-08-01), Dixon
patent: 5174649 (1992-12-01), Alston
Herman Stephen
Marshall Thomas
Pashley Michael D.
Halajian Dicran
O'Shea Sandra
Philips Electronics North America Corp.
Zeade Bertrand
LandOfFree
Apparatus for mixing light from different color LEDs does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for mixing light from different color LEDs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for mixing light from different color LEDs will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2533713