Multi-chip LED color mixing by diffraction

Details Multi-chip LED color mixing by diffraction Multi-chip LED color mixing by diffraction

2001-06-15

2003-08-12

Quach-Lee, Y. My (Department: 2875)

Illumination

Plural light sources

Particular wavelength

C362S244000, C362S309000, C362S800000, C359S571000

Reexamination Certificate

active

06604839

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to semiconductor light emitting devices and more particularly to solid state light sources in which the outputs of several light emiting semiconductor devices are mixed.
BACKGROUND
The advent of high-brightness red, green, and blue light emitting diodes (LEDs), such as In
x
Al
y
Ga
1−x−y
N and In
x
Al
y
Ga
1−x−y
P LEDs, has generated strong interest in finding efficient ways to mix the outputs of several such LEDs to make a white light source. Such an LED-based white light source would have commercially attractive applications including illumination, decorative lighting, and display back-lighting.
In one approach to generating white light with multiple LEDs, the outputs of several LEDs of different colors are directed into a reflective mixing tube which spatially mixes light of different colors. Reflections from the walls of the tube produce virtual images of each light source which make the light sources appear to be spread over a larger area. Such mixing tubes only approximate the virtual overlap of the separated color sources, however. Hence, light of different colors is not uniformly mixed. Improved approximations require longer tube lengths and more reflections, which result in increased light loss.
In another approach to generating white light with multiple LEDs, the outputs of several LEDs of different colors are directed onto dichroic beam splitters which spatially overlap and mix the different colors. Unfortunately, such color mixing optical systems utilizing beam splitters can be complex, bulky, and expensive.
What is needed is an LED-based white light source in which the outputs of several LEDs are simply, efficiently, and uniformly mixed.
SUMMARY
A light emitting device in accordance with an embodiment of the present invention includes a diffractive optical element, a first light emitting diode emitting first light having a first range of wavelengths, and a second light emitting diode emitting second light having a second range of wavelengths. The first light is directed onto the diffractive optical element at a first range of angles of incidence, and the second light is directed onto the diffractive optical element at a second range of angles of incidence. The first light and the second light substantially overlap on the diffractive optical element. The diffractive optical element diffracts at least a portion of the first light and at least a portion of the second light into the same range of angles of diffraction to obtain light having a desired range of wavelengths.
The light emitting device may further include at least a third light emitting diode emitting third light having a third range of wavelengths. The third light is directed onto the diffractive optical element at a third range of angles of incidence such that at least a portion of the third light is diffracted into the same range of angles of diffraction as the portion of the first light and the portion of the second light. In one such embodiment, the first light includes blue light, the second light includes green light, the third light includes red light, and the diffractive optical element provides a white light output.
Advantageously, a light emitting device in accordance with an embodiment of the present invention can efficiently mix the outputs of two or more light emitting diodes to form a substantially uniform output substantially spatially and angularly overlapped in all subsequent regions.


REFERENCES:
patent: 5153751 (1992-10-01), Ishikawa et al.
patent: 5323302 (1994-06-01), Bertling et al.
patent: 5362957 (1994-11-01), Nakai et al.
patent: 5477436 (1995-12-01), Bertling et al.
patent: 5803579 (1998-09-01), Turnbull et al.
patent: 5810469 (1998-09-01), Weinreich
patent: 5995071 (1999-11-01), Mertz
patent: 6132072 (2000-10-01), Turnbull et al.
patent: 6139166 (2000-10-01), Marshall et al.
patent: 6392806 (2002-05-01), Swanson
patent: 6417967 (2002-07-01), Swanson
Christopher L. Coleman, Robert H. Weissman, and Annette Grot, “Applications of Diffractive Optics With LED Sources,” in Diffractive Optics and Micro-Optics, OSA Technical Digest (Optical) Society of America, Washington, DC., 2000, pp. 291-293.
Christopher L. Coleman, Robert H. Weissman, and Annette Grot, “Applications of Diffractive Optics with LED Sources”, presentation at “Diffractive Optics and Micro-Optics 2000,” Jun. 22, 2000, pp. 291-293.
H. Dammann, “Color Separation Gratings,” Applied Optics, vol. 17, No. 15, Aug. 1978, pp. 2273-2279.
Weichung Chao, Sien Hi, Ching Yi Wu, and Chung J. Kuo, “Computer-Generated Holographic Diffuser for Color Blending Considering Divergent Sources,” Opto-Electronics & Systems Laboratories, Industrial Technology Research Institute, pp. 100-107.
Weichung Chao, Sien Chi, Ching Yi Wu, and Chung J. Kuo, “Computer-Generated Holographic Diffuser for Color Mixing,” Optics Communications, 151, May 15, 1998, pp. 21-24.

Affiliated with

Also associated with

Rating

Multi-chip LED color mixing by diffraction does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Multi-chip LED color mixing by diffraction, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-chip LED color mixing by diffraction will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3085791