Solid state illumination source utilizing dichroic reflectors

• US 6,273,589 B1
• Filed: 01/29/1999
• Issued: 08/14/2001
• Est. Priority Date: 01/29/1999
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Cutler, Gergory M., Weber, Andreas G., Trutna, Jr., William R.
• Primary Examiner(s): Husar, Stephen
• Assistant Examiner(s): WARD, JOHN A
• Application Number:
  US09/239,572
• Time in Patent Office: 928 Days
• Field of Search: 362/230, 362/231, 362/259, 362/293
• US Class Current: 362/293
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/50 Wavelength conversion elements
• CPC Class Codes: H01S 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength
• CPC Class Codes: H01S 5/423 having a vertical cavity

Abstract

A light source having emissions in a plurality of spectral bands. The simplest light source according to the present invention is constructed from first and second light sources and a dichroic beam splitter. The first and second solid state light sources emit light in first and second bands of non or only partially-overlapping wavelengths. The dichroic beam splitter combines light from the first and second solid state light sources by passing light in the first band while reflecting light in the second band to generate light having a spectral content in the first and second bands. The solid state light sources are preferably arrays of LEDs, VCSELs, or edge emitting semiconductor lasers. A light source having improved radiance in the green region of the spectrum can be constructed by utilizing first and second solid state light sources that emit in different bands in the green portion of the spectrum. A white light source can be constructed by utilizing a third solid state light source and a second dichroic beam splitter and by choosing the emission bands of the light sources such that light leaving the second dichroic beam splitter is perceived as white by an observer when all three solid state light sources are emitting light. This light source has a radiance that is higher than the radiance of each individual solid state light source.

Claims

1. A light source comprising:

a first solid state light source emitting light in a first band of wavelengths;

a second solid state light source emitting light in a second band of wavelengths different from said first band of wavelengths; and

a first dichroic beam splitter for combining light from said first and second solid state light sources, said beam splitter passing light in said first band of wavelengths while reflecting light in said second band of wavelengths, said first dichroic beam splitter combining light from said first and second solid state light sources to generate light having a spectral content in both of said first and second bands and a radiance greater than the radiance of either said first or second solid state light sources, wherein said first solid state light source comprises an array of LEDs, each LED emitting light in said first band of wavelengths, said first band of wavelengths being different from said second band of wavelengths.

2. A light source comprising:

a first solid state light source emitting light in a first band of wavelengths;

a second solid state light source emitting light in a second band of wavelengths different from said first band of wavelengths; and

a first dichroic beam splitter for combining light from said first and second solid state light sources, said beam splitter passing light in said first band of wavelengths while reflecting light in said second band of wavelengths, said first dichroic beam splitter combining light from said first and second solid state light sources to generate light having a spectral content in both of said first and second bands and a radiance greater than the radiance of either said first or second solid state light sources, wherein said first solid state light source comprises an array of semiconductor lasers.

3. A light source comprising:

a first solid state light source emitting light in a first band of wavelengths;

a second solid state light source emitting light in a second band of wavelengths different from said first band of wavelengths; and

a first dichroic beam splitter for combining light from said first and second solid state light sources, said beam splitter passing light in said first band of wavelengths while reflecting light in said second band of wavelengths, said first dichroic beam splitter combining light from said first and second solid state light sources to generate light having a spectral content in both of said first and second bands and a radiance greater than the radiance of either said first or second solid state light sources, said first band being different from said second band, wherein said first and second solid state light sources comprise arrays of blue emitting LEDs.

4. The light source of claim 3 wherein said first solid state light source comprises a blue emitting solid state light source and a chemical for converting blue light to green light.

5. A light source comprising:

a first solid state light source emitting light in a first band of wavelengths;

a second solid state light source emitting light in a second band of wavelengths different from said first band of wavelengths;

a first dichroic beam splitter for combining light from said first and second solid state light sources, said beam splitter passing light in said first band of wavelengths while reflecting light in said second band of wavelengths, said first dichroic beam splitter combining light from said first and second solid state light sources to generate light having a spectral content in both of said first and second bands and a radiance greater than the radiance of either said first or second solid state light sources;

a third solid state light source emitting light in a third band of wavelengths; and

a second dichroic beam splitter, said second dichroic beam splitter reflecting light in said third band while passing light in said first and second bands, said second dichroic beam splitter combining light from said third light source with light from said first dichroic beam splitter, wherein each of said solid state light sources comprises an array of LEDs and wherein the relative areas of said array of LEDs is chosen such that light leaving said second dichroic beam splitter is perceived as white by an observer when all three solid state light sources are on.