Color modulated led-based illumination

Abstract

An LED based illumination device transmits information by receiving an amount of digital data and modulating a color of light emitted from the LED based illumination device based on the digital data. The luminous flux of the emitted light remains approximately constant while the color of light varies. A receiver may receive the emitted light and demodulate a signal indicative of the color of emitted light to determine the digital data. The color of the light may be modulated by varying current provided to different LEDs, where the different LEDs cause different color of light to be emitted from the LED based illumination device.

What is claimed is: 
     
         1 . A method of receiving information from an LED based illumination device, comprising:
 receiving an amount of light emitted from the LED based illumination device, wherein a luminous flux of the amount of light emitted from the LED based illumination device remains approximately constant while a color of light varies;   determining a signal indicative of the color of the received light; and   demodulating the signal indicative of the color of the received light to determine the digital data received from the LED based illumination device.   
     
     
         2 . The method of  claim 1 , wherein the receiving of the amount of light emitted from the LED based illumination device involves a color sensing device. 
     
     
         3 . The method of  claim 2 , wherein the color sensing device is any of a Complementary Metal-Oxide Semiconductor (CMOS) device, a Charge-Coupled Device (CCD) device, and a filtered photodiode. 
     
     
         4 . The method of  claim 1 , wherein the demodulating the signal indicative of the color of the received light involves any of amplitude demodulation, frequency demodulation, pulse width demodulation, and phase demodulation. 
     
     
         5 . The method of  claim 1 , wherein the color of the light received from the LED based illumination device varies at a frequency less than 2,000 hertz. 
     
     
         6 . The method of  claim 1 , wherein the color of the light received from the LED based illumination device varies along lines of constant Correlated Color Temperature (CCT) in a CIE 1931 color space. 
     
     
         7 . The method of  claim 1 , wherein a Correlated Color Temperature (CCT) of the light received from the LED based illumination device varies in a CIE 1931 color space. 
     
     
         8 . An LED based illumination device comprising:
 a first LED configured to receive a first current, wherein light emitted from the first LED enters a color conversion cavity, and wherein a first light emitted from the LED based illumination device based on the light emitted from the first LED is a first colored light;   a second LED configured to receive a second current, wherein light emitted from the second LED enters the color conversion cavity, and wherein a second light emitted from the LED based illumination device based on the light emitted from the second LED is a second colored light; and   a modulator configured to receive an amount of digital data and modulate the first current and the second current such that a luminous flux of the light emitted from the LED based illumination device remains approximately constant and a combined color of light emitted from the LED based illumination device varies based on the digital data.   
     
     
         9 . The LED based illumination device of  claim 8 , wherein the modulating of the first and second currents involves any of amplitude modulation, frequency modulation, pulse width modulation, and phase modulation. 
     
     
         10 . The LED based illumination device of  claim 8 , wherein the color of the light emitted from the LED based illumination device varies at a frequency less than 2,000 hertz. 
     
     
         11 . The LED based illumination device of  claim 8 , wherein the color of the light emitted from the LED based illumination device varies along lines of constant Correlated Color Temperature (CCT) in a CIE 1931 color space. 
     
     
         12 . The LED based illumination device of  claim 8 , wherein a Correlated Color Temperature (CCT) of the light emitted from the LED based illumination device varies in a CIE 1931 color space. 
     
     
         13 . The LED based illumination device of  claim 8 , wherein a color point of the light emitted from the LED based illumination device varies within a degree of departure Δxy of 0.010 from a nominal color point in a CIE 1931 xy diagram. 
     
     
         14 . The LED based illumination device of  claim 8 , wherein the light emitted from the first LED preferentially illuminates a first wavelength converting material that is physically separated from a light emitting surface of the first LED, and wherein the light emitted from the second LED preferentially illuminates a second wavelength converting material that is physically separated from a light emitting surface of the second LED.