Semiconductor white light sources

Abstract

Semiconductor white light sources presented herein include special combinations of a blue source and a yellow source where these light fields are substantially overlapped. The source of blue light includes a blue emitting semiconductor operating in a conventional manner. However, this blue light source is combined with a special yellow light source and the light produced by each is mixed together. The yellow light source is primarily comprised of a high output ultraviolet emitting semiconductor coupled to a wavelength shifting medium whereby the semiconductor pumps the wavelength shifting medium causing re-emission at longer wavelengths; namely those corresponding to yellow colored light. These two sources operating in conjunction with each other operate to produce higher outputs than those attainable in competitive white light semiconductor systems. In special versions, provision is made whereby the color coordinates may be tuned by a variable current applied to the blue emitting semiconductor.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims and drawings where:

FIG. 1 illustrates a simplest version of these optical systems in a cross section diagram;

FIG. 2 shows these systems in conjunction with a ray trace diagram showing illumination field overlap;

FIG. 3 is an intensity plot of the excitation spectrum of a wavelength shifting medium—a YAG phosphor;

FIG. 4 is an intensity plot of the excitation spectrum a wavelength shifting medium—a silicate phosphor;

FIG. 5 is an intensity plot of a compound system comprising spectral peaks at 455 (blue) and 555 (yellow);

FIG. 6 is a diagram including separate electrical drive inputs for two semiconductors;

FIG. 7 is a chromaticity diagram showing a plot of light sources which may be used in these systems.

FIG. 8 is a special version with modification to the output of one of the semiconductor elements;

FIG. 9 shows a special version where semiconductor elements are stacked into a vertical column; and

FIG. 10 is another version having semiconductors in a vertical column with further system support elements.

Claims

1) Semiconductor white light sources comprising: a blue emitting semiconductor;an ultraviolet emitting semiconductor; anda wavelength shifting medium,said wavelength shifting medium being proximately disposed about said ultraviolet emitting semiconductor whereby it is illuminated with ultraviolet light,said blue emitting semiconductor and ultraviolet emitting semiconductor are arranged to emit light into a common illumination field.

2) Semiconductor white light sources of claim 1, said semiconductors are comprised of InGaN structures.

3) Semiconductor white light sources of claim 2, said ultraviolet emitting semiconductor has an emission spectral peak between about 365 and 420 nanometers, said blue emitting semiconductor has an emission spectral peak between about 445 and 480 nanometers, said wavelength shifting medium has an emission spectral peak between about 540 and 580 nanometers.

4) Semiconductor white light sources of claim 1, said wavelength shifting medium is embodied as a colloid of phosphor grains suspended in a binder material.

5) Semiconductor white light sources of claim 4, said wavelength shifting medium includes phosphors characterized as either silicates or theogalates.

6) Semiconductor white light sources of claim 1, said blue emitting semiconductor and ultraviolet emitting semiconductor are arranged closely spaced and side-by-side on a substrate whereby each of their primary emission surface is substantially parallel to a mounting surface of the substrate, and their emission fields form a substantial overlap.

7) Semiconductor white light sources of claim 6, said semiconductors laying under an optical lens having a cavity in an underside, said cavity at least partly filled with said wavelength shifting medium.

8) Semiconductor white light sources of claim 4, said blue emitting semiconductor and ultraviolet emitting semiconductor are arranged closely spaced and side-by-side on a substrate whereby each of their primary emission surface is substantially parallel to a mounting surface of the substrate, and their emission fields form a substantial overlap in the far-field of a lens.

9) Semiconductor white light sources of claim 1, further comprising: a lens and a mounting substrate arranged to form an enclosed cavity when they are pushed together.

10) Semiconductor white light sources of claim 7, said blue emitting semiconductor further being enveloped in a dispersant material.

11) Semiconductor white light sources of claim 10, said dispersant material and said wavelength shifting material together substantially fill a cavity formed between a lens and a substrate.

12) Semiconductor white light sources of claim 11, said dispersant material being comprised of a colloid of dispersant grains suspended in a binder material.

13) Semiconductor white light sources of claim 1, said ultraviolet emitting semiconductor having a primary emission surface parallel to a primary emission surface of said blue emitting semiconductor, mounted together each symmetric about a single optic axis.

14) Semiconductor white light sources of claim 13, further having electrical contact coupling therebetween said ultraviolet emitting semiconductor and said blue emitting semiconductor, said contacts suitable for carrying electrical current for energizing said semiconductors and additionally providing mechanical support.

15) Semiconductor white light sources of claim 13, further comprising a dispersant medium, said wavelength shifting medium enveloping said ultraviolet emitting semiconductor and said dispersant medium enveloping said blue emitting semiconductor.

16) Semiconductor white light sources of claim 15, further comprising: a reflector element formed into a recess of a substrate; anda blue transparent intermediate substrate,said reflector element optically coupled to said blue emitting semiconductor, andsaid blue transparent intermediate substrate is disposed between said ultraviolet emitting semiconductor and said blue emitting semiconductor having thereon opposing sides said wavelength shifting medium and said dispersant medium.

17) Semiconductor white light sources of claim 1, said blue emitting semiconductor further comprising coupling to a variable current source.

18) Semiconductor white light sources of claim 3, said blue emitting semiconductor further comprising coupling to a variable current source.

19) Semiconductor white light sources of claim 6, said blue emitting semiconductor further comprising coupling to a variable current source.

20) Semiconductor white light sources of claim 13, said blue emitting semiconductor further comprising coupling to a variable current source.