Light source with tunable cri

Abstract

A light-emitting device with at least two light-emitting dies encapsulated with two different types of the wavelength-converting materials is disclosed. Each of the wavelength-converting materials is configured to produce a visible light from a narrow band light near UV region produced by the light-emitting dies, but with different correlated color temperatures (CCT) and different spectral contents. The combination of the two visible light forms the desired visible white light. The Color rendering index of the light-emitting device is tunable by adjusting the supply current to the light-emitting dies. In another embodiment, a light module with tunable CRI for an illumination system is disclosed.

What is claimed is: 
     
         1 . A light-emitting device, comprising:
 a plurality of conductors;   first and second light-emitting dies attached respectively to one the plurality of conductors, the first and second light-emitting dies configured to emit a radiation having a peak wavelength near UV light;   a first wavelength-converting material encapsulating the first light-emitting die, the first wavelength-converting material configured to convert at least a portion of the radiation emitted by the first light-emitting die into a first visible light; and   a second wavelength-converting material encapsulating the second light-emitting die and the first wavelength-converting material, wherein the second wavelength-converting material is configured to convert at least a portion of the radiation emitted by the second light-emitting die into a second visible light having a different color correlation temperature and spectral content compared to the first visible light, and wherein at least a portion of the radiation emitted by the first light-emitting die is configured to be converted into the first visible light prior to entering the second wavelength-converting material.   
     
     
         2 . The light-emitting device of  claim 1 , wherein the first and second light-emitting dies are InGaN dies. 
     
     
         3 . The light-emitting device of  claim 1 , wherein the first radiation has a wavelength between 300 nm and 480 nm. 
     
     
         4 . The light-emitting device of  claim 1 , wherein the first wavelength-converting material comprises red phosphor. 
     
     
         5 . The light-emitting device of  claim 1 , wherein the second wavelength-converting material comprises yellow phosphor. 
     
     
         6 . The light-emitting device of  claim 1 , wherein a portion of the plurality of conductors defines a pad adapted to receive the first and second light-emitting dies. 
     
     
         7 . The light-emitting device of  claim 1 , wherein one of the plurality of conductors defines a hollow adapted to receive the first light-emitting die and the first wavelength-converting material. 
     
     
         8 . The light-emitting device of  claim 7 , wherein the conductor defining the hollow further defines a pad portion adapted to receive the second light-emitting die. 
     
     
         9 . The light-emitting device of  claim 1 , wherein color rendering index of light emitting device is substantially tunable by altering supply current to the second light-emitting die. 
     
     
         10 . A lighting device, comprising:
 a substrate;   a first light-emitting die attached to the substrate, the first light-emitting die configured to emit a first radiation having a peak wavelength near UV light;   a first wavelength-converting material encapsulating the first light-emitting die, the first wavelength-converting material configured to convert the first radiation into a first visible light, the first visible light having a first correlated color temperature and a first spectral content;   a second light-emitting die attached to the substrate, the second light-emitting die configured to emit a second radiation having a peak wavelength near UV light; and   a second wavelength-converting material encapsulating the second light-emitting die and the first wavelength-converting material, wherein the second wavelength-converting material is configured to convert the second radiation into a second visible light, the second visible light having a second correlated color temperature and a second spectral content, the second correlated color temperature and the second spectral content being different compared to the first color correlation temperature and the first spectral content of the first visible light, and wherein the first radiation is configured to be converted into the first visible light prior to entering the second wavelength-converting material.   
     
     
         11 . The lighting device of  claim 10 , wherein the first and second light-emitting dies are InGaN dies. 
     
     
         12 . The lighting device of  claim 10 , wherein the first and second radiations have a peak wavelength between 300 nm and 480 nm. 
     
     
         13 . The lighting device of  claim 10 , wherein the first wavelength-converting material comprises red phosphor. 
     
     
         14 . The lighting device of  claim 10 , wherein the second wavelength-converting material comprises yellow phosphor. 
     
     
         15 . The lighting device of  claim 10 , wherein the substrate further comprises a hollow area adapted to receive the first light-emitting die and the first wavelength-converting material. 
     
     
         16 . The lighting device of  claim 10 , wherein color rendering index of the lighting device is substantially tunable by altering supply current to the second light-emitting die. 
     
     
         17 . The lighting device of  claim 10  forms a portion of an illumination system having at least one additional light-emitting die similar to the first light-emitting die encapsulated by the first wavelength material and at least another additional light-emitting die similar to the second light-emitting die encapsulated by the second wavelength-converting material. 
     
     
         18 . An illumination system, comprising:
 a substrate;   first and second groups of light-emitting dies connected electrically to the substrate, the first and second groups of light-emitting dies configured to emit radiation having a peak wavelength near UV light;   a first wavelength-converting material encapsulating the first group of the light-emitting dies, the first wavelength-converting material configured to convert radiation emitted by the first group of light-emitting dies into a first visible light, the first visible light having a first correlated color temperature and a first spectral content;   a second wavelength-converting material encapsulating the second group of the light-emitting dies and the first wavelength-converting material, the second wavelength-converting material configured to convert radiation emitted by the second group of light-emitting dies into a second visible light having a second correlated color temperature and a second spectral content, the second correlated color temperature and the second spectral content being different from the first correlated color temperature and the first spectral content of the first visible light, wherein at least a portion of radiation emitted by the first group of the light-emitting dies is configured to be converted into the first visible light prior to entering the second wavelength-converting material.   
     
     
         19 . The illumination system of  claim 18 , wherein the first wavelength-converting material comprises red phosphor and the second wavelength-converting material comprises yellow phosphor. 
     
     
         20 . The illumination system of  claim 18 , wherein the first and second light-emitting dies are InGaN dies.