Method and apparatus for producing untainted white light using off-white light emitting diodes
View Patent ↗A white light emitting device by using off-white light emitting diodes (LED's). Rather than using just pure white LEDs, the white light emitting device arranges those LEDs which exhibit off-white colors in a manner such that the combination of light emanating from these off-white LEDs produces a radiation which appears substantially pure white to the human eye.
1. A light generating apparatus comprising:
a purplish-white light emitting diode comprising:
a first blue light emitting diode, wherein said first blue light has a wavelength between 460 and 465 nm; and
a first layer comprising a wavelength converting material for converting said first blue light to white light;
a greenish-white light emitting diode comprising:
a second blue light emitting diode, wherein said second blue light has a wavelength between 470 and 480 nm; and
a second layer comprising said wavelength converting material,
wherein a combination of light emanating from said purplish-white light emitting diode and said greenish-white light emitting diode is white to the human eye.
2. The apparatus of claim 1 , wherein said purplish-white light emitting diode has color coordinates which lie on one side of a black body curve and said greenish-white light emitting diode has color coordinates which line on the other side of said black-body curve.
3. The apparatus of claim 1 wherein said wherein said first and second layers comprise yellow phosphor wavelength converting material.
4. The apparatus of claim 1 further comprising a plurality of purplish-white light emitting diodes and an equal number of greenish-white light emitting diodes arranged in a manner to complement said plurality of purplish-white light to produce said pure white light.
5. A white light emitting device comprising:
a substrate with electrically conductive traces;
an array comprising a first blue LED having a wavelength emission range of 470–480 nm and a second blue LED having a wavelength emission range of 460–465 nm, wherein said first blue LED and said second blue LED are attached to said substrate;
encapsulant comprising yellow phosphor wavelength converting material, covering each LED, wherein a combination of converted light from said first blue LED and said second blue LED produces pure white light;
a circuit for providing electric current to each LED.
6. The white light emitting device of claim 5 wherein said substrate has cavities onto which said first blue LED and said second blue LED are disposed thereon, said cavities acting as a reflector in collecting and directing light out in a desired direction.
7. The white light emitting device of claim 5 wherein said encapsulant and said yellow phosphor wavelength converting material are shaped in a lens configuration to impart a desired radiation pattern of emitted light.
8. The white light emitting device of claim 5 further comprising an optical lens placed over said array of LEDs used to enhance a radiation pattern of emitted light.
9. The white light emitting device of claim 5 wherein light generated by the first blue LED and the second blue LED are used to illuminate an object for an image capturing device.