Tunable white point light source using a wavelength converting element

Abstract

A uniform high brightness light source is provided using a plurality of light emitting diode (LED) chips with slightly different pump wavelengths with a wavelength converting element that includes at least two different wavelength converting materials that convert the light to different colors of light. The intensity of the light produced by the LED chips may be varied to provide a tunable CCT white point. The wavelength converting element may be, e.g., a stack or mixture of phosphor or luminescent ceramics. Moreover, the manufacturing process of the light source is simplified because the LED chips are all manufactured using the same technology eliminating the need to manufacture different types of chips.

1 . A light source comprising:
 at least two light emitting diode chips, each of which produces light having wavelengths that differ by 5 nm or more; and   a wavelength converting element mounted to receive the light emitted by the at least two light emitting diode chips, the wavelength converting element comprising at least two different wavelength converting materials that convert the light from the at least two light emitting diode chips to different colors of light.   
     
     
         2 . The light source of  claim 1 , wherein the wavelength converting element comprises a stack of wavelength converting films. 
     
     
         3 . The light source of  claim 1 , wherein the wavelength converting element comprises a mixture of the different wavelength converting materials that convert the light from the at least two light emitting diode chips to different colors of light. 
     
     
         4 . The light source of  claim 3 , wherein the mixture of the different wavelength converting materials is approximately homogenous. 
     
     
         5 . The light source of  claim 1 , wherein the wavelength converting element comprises one or more luminescent ceramics. 
     
     
         6 . The light source of  claim 1 , wherein the wavelength converting element comprises one or more phosphor layers. 
     
     
         7 . The light source of  claim 1 , further comprising at least one submount, the at least two light emitting diode chips mounted to the at least one submount. 
     
     
         8 . The light source of  claim 7 , further comprising:
 a heat sink, the at least one submount being mounted on the heat sink; and   a support that is coupled to the heat sink, the support holding the wavelength converting element.   
     
     
         9 . The light source of  claim 7 , wherein the at least one submount is one submount and the at least two light emitting diode chips are mounted on the one submount. 
     
     
         10 . The light source of  claim 1 , further comprising:
 at least one light detector positioned to receive light produced by the wavelength converting element and producing a signal in response to the intensity of the light detected; and   a drive circuit coupled to the at least two light emitting diode chips and the at least one light detector, the drive circuit controlling the intensity of the light emitted by at least one of the light emitting diode chips in response to the signal produced by the at least one light detector.   
     
     
         11 . The light source of  claim 1 , further comprising a wavelength selection element positioned between the at least two light emitting diode chips and the wavelength converting element. 
     
     
         12 . The light source of  claim 11 , further comprising:
 a collimator element positioned between the at least two light emitting diode chips and the wavelength selection element; and   a concentrator element positioned between the wavelength selection element and the wavelength converting element.   
     
     
         13 . The light source of  claim 1 , wherein the at least two light emitting diode chips produce light having wavelengths that differ by 50 nm or less. 
     
     
         14 . A method comprising:
 producing light from a plurality of light emitting diode chips, each chip producing light with a different range of wavelengths that differ by more than approximately 5 nm;   converting portions of the light from the plurality of light emitting diode chips to at least two different colors of light using a wavelength converting element and transmitting other portions of the light from the plurality of light emitting diode chips through the wavelength converting element to produce a combined converted and transmitted light; and   controlling the white point of the combined converted and transmitted light by altering an intensity of the light from at least one light emitting diode chip to vary an intensity of at least one color of light converted by the wavelength converting element.   
     
     
         15 . The method of  claim 14 , further comprising mounting the plurality of light emitting diode chips on at least one submount. 
     
     
         16 . The method of  claim 15 , further comprising:
 mounting the at least one submount to a heat sink; and   mounting the wavelength converting element over the plurality of light emitting diode chips on a support that is coupled to the heat sink.   
     
     
         17 . The method of  claim 14 , wherein converting portions of the light from the plurality of light emitting diode chips is performed in a stack of wavelength converting films that form the wavelength converting element. 
     
     
         18 . The method of  claim 17 , wherein the stack of wavelength converting films comprises one or more luminescent ceramics. 
     
     
         19 . The method of  claim 14 , wherein the stack of wavelength converting films comprises one or more phosphor layers. 
     
     
         20 . The method of  claim 14 , wherein converting portions of the light from the plurality of light emitting diode chips is performed by a mixture of a different wavelength converting materials in the wavelength converting element. 
     
     
         21 . The method of  claim 20 , wherein the mixture of the different wavelength converting materials is approximately homogenous. 
     
     
         22 . The method of  claim 14 , further comprising:
 detecting the combined converted and transmitted light and producing a signal in response; and   altering an intensity of the light from at least one light emitting diode chip in response to the signal produced by the light detector.   
     
     
         23 . The method of  claim 22 , wherein the detecting and altering are performed continuously or periodically. 
     
     
         24 . The method of  claim 22 , wherein the detecting and altering are performed once. 
     
     
         25 . The method of  claim 14 , further comprising transmitting light from a plurality of light emitting diode chips through a wavelength selection element and reflecting back converted light from the wavelength converting element by the wavelength selection element. 
     
     
         26 . The method of  claim 25 , further comprising:
 approximately collimating the light from a plurality of light emitting diode chips prior to being transmitted through the wavelength selection element; and   concentrating the light from a plurality of light emitting diode chips after being transmitted through the wavelength selection element and prior to being incident on the wavelength converting element.   
     
     
         27 . The method of  claim 14 , the method further comprising producing light from at least one group of light emitting diode chips, each chip within a group producing light with a range of wavelengths that differ by less than approximately 5 nm. 
     
     
         28 . The method of  claim 14 , wherein each chip produces light with a different range of wavelengths that differ by less than approximately 50 nm.