Method and apparatus for producing untainted white light using off-white light emitting diodes

• US 7,066,623 B2
• Filed: 12/19/2003
• Issued: 06/27/2006
• Est. Priority Date: 12/19/2003
• Status: Expired due to Term

• Current Assignee: Epistar Corporation
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Lee, Soo Ghee, Ng, Kee Yean, Lee, Meng Ee
• Primary Examiner(s): O'Shea, Sandra
• Assistant Examiner(s): Choi, Jacob Y.
• Application Number:
  US10/742,688
• Publication Number:
  US 20050135094A1
• Time in Patent Office: 921 Days
• Field of Search: 362/230, 362/231, 362/236, 362/240, 257/103, 313/503, 313/504, 313/506, 313/509, 313/498
• US Class Current: 362/230
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/49175 Parallel arrangements
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/40 Details of LED load circuits

Abstract

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.

Claims

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.