Using multiple types of phosphor in combination with a light emitting device

Abstract

Light is emitted from a light emitting device. The light emitted from the light emitting device is combined with light from a first type of phosphor and a second type of phosphor. The first type of phosphor and the second type of phosphor are within an epoxy placed over the light emitting device. The first type of phosphor, when excited, emits light of a first color. The second type of phosphor, when excited, emits light of a second color. The first color and the second color are different.

1 . A method for generating colored light comprising:
 emitting light from a light emitting device; and,   combining light emitted from light emitting device with light from a first type of phosphor and a second type of phosphor, the first type of phosphor and the second type of phosphor being within an epoxy placed over the light emitting device, wherein the first type of phosphor, when excited, emits light of a first color, wherein the second type of phosphor, when excited, emits light of a second color, and wherein the first color and the second color are different.   
   
   
       2 . A method as in  claim 1  wherein the light emitting device is a blue light emitting diode, wherein the first type of phosphor is a green phosphor, and wherein the second type of phosphor is a yellow phosphor. 
   
   
       3 . A method as in  claim 1 :
 wherein the light emitting device is a blue light emitting diode;   wherein the first type of phosphor is one of the following:
 Strontium Thiogallate:Europium, having a chemical formula of SrGa 2 S 4 :Eu; 
 a thiogallate phosphor that is a mix group II alkaline metal thiogallate phosphor (Sr,Ca,Ba)(Al,Ga) 2 S 4 :Eu; BaSrGa 4 S 7 :Eu; and, 
   wherein the second type of phosphor is a yellow phosphor having one of the following chemical formulas:
 Tb 3 Al 5 O 12 :Ce, 
 Sr(Ba,Ca)SiO 4 :Eu, 
 YAG:Ce.