Abstract:
A plurality of different frequency absorbing materials are placed between an LED and a surface so as to generate a non-monochromatic colors. In one embodiment, a light device is arranged with light sources, each of which emit light of a different color, and by surrounding the different colored light sources with a color changing media, each of which absorb light of different colors and by allowing the light sources to be individually calibrated as to power level, a variety of colors can be achieved.

Description:
TECHNICAL FIELD 
     This invention relates to light sources and more particularly to light sources that can selectively change color across a broad spectrum. 
     BACKGROUND OF THE INVENTION 
     There are presently many uses for light sources that can change color. One popular light source is constructed from light emitting diodes (LEDs). One problem is that each LED can only emit light of a single color and usually these colors are monochromatic. Today, these colors are red, green, blue or amber. A multicolor light source could be built with combinations of LED chips (red, blue, green, amber) and then by selectively activating the chips, one of the colors could be achieved. Colors other than the individual chip color could be obtained by activating two or more different color chips at one time. This, however, will result in poor (uneven) color mixing. 
     Additional colors can be achieved by surrounding each LED chip with a color changing medium. For example, by using yellow phosphorus with a blue LED, the color white can be achieved. Phosphors are selected based upon their absorption and emission characteristics. Using this arrangement, a larger number of colors can be achieved, all of which fall on the border of the CIE diagram since they are all saturated colors. Saturated colors are normally produced by the diodes which emit a certain color or wavelength. If this color is not absorbed by the phosphor, a saturated color (generally) will result. Saturated colors can also be produced using the phosphor loading (max) depending on the color desired. 
     BRIEF SUMMARY OF THE INVENTION 
     A plurality of different frequency absorbing materials are placed between an LED and a surface so as to generate non-monochromatic colors. In one embodiment, a light device is arranged with light sources, each of which emit light of a different color, and by surrounding the different colored light sources with a color changing media, each of which absorb light of different colors and by allowing the light sources to be individually calibrated as to power level, a variety of colors can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a multicolored light device having multiple LED chips; 
         FIG. 2  shows one embodiment of a control circuit for analyzing the circuit of  FIG. 1  in a panel arrangement; and 
         FIG. 3  shows a CIE diagram. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows device  10  having housing  11  with substrate  14 . Within cavity  12  of housing  11 , there resides a plurality of different colored LED chips, for example, chips  13 -R 1 ,  13 -G 1 ,  13 -B 1 ,  13 -R 2 ,  13 -G 2 , and  13 -B 2 . Some of these chips could be red (R), some green (G) or some blue (B) or they could be any other available colored chip. Note that while only two chips of each color (R, G, B) are shown, any combination of chips and any number of chips can be utilized. 
     Each of the chips is connected by bond wires  101  to controller  15 . Controller  15 , in conjunction with sensor  16 , controls power to the various LED chips via wires  102 . Sensor  16  measures, for example, the frequency of the light output and/or the intensity of the light and causes controller  15  to add or remove power or to modify other parameters, such as frequency. 
     Cavity  12  has contained therein incapsulant material  13  containing different colored phosphors, such as phosphors  17 - 1 ,  17 - 2 , and  17 - 3 . Some phosphors absorb certain colors and do not absorb other colors. The colors that are not absorbed are emitted as saturated colors. Some of the phosphors can convert the light to a different color, and these converted colors can mix with the saturated colors to obtain colors from within the CIE diagram as shown in  FIG. 3  in the manner to be discussed hereinafter. The intensity of each LED can, if desired, be tuned by the controller so that the intensity of different colors or mixtures of colors can be tuned. Substrate  14  can be connected to a heatsink (not shown) to conduct heat away from the dies, if desired. 
       FIG. 2  shows one embodiment of an arrangement for enabling the system of  FIG. 1  in a panel arrangement. As shown, panel  20  includes substrate  24  having mounted thereon LED chips  23 - 1  to  23 -N. These chips can be any combination of colors desired as discussed above operable under control of controller  15  and sensor  16  to achieve different colors, depending upon the intensity of the LED as compared to the different phosphors  22 - 1  to  22 -N surrounding the LED chips. While  FIGS. 1 and 2  illustrate only a few instances of phosphor, this phosphor can be as dense as is necessary to produce the colors desired. 
       FIG. 3  illustrates a CIE chart showing different colors. Monochromatic colors are at the circumference of the chart (line  301 ) with white shown at the center. The letters on the chart show the blended colors. Thus G is green, B is blue and BG represents blue and green while gB is less green than blue. 
     The output color that a user would observe can be selected using the CIE chart of  FIG. 3 , for example, by selecting a diode color, and a plurality of phosphors to surround the selected diode. Each if the selected phosphors can then be weighted by efficiency and by absorption. For ease of discussion we can call that weighting a QE and express it as a percentage of phosphor. 
     By way of example, assume that an output color is desired that would fall within area  31  (the triangular area formed within broken lines  302 ,  303 ,  304 ). Using such an assumption, a UV blue diode in the range of perhaps 460 nm can be selected. Such a diode would fall at the cross of X coordinate 0.15 and Y coordinate 0.05 (0.15, 0.05). 
     A green phosphor could be selected that would fall at coordinate point 0.2, 7.5. By selecting a 15% QE for the selected phosphor, point  310  is known. Note that point  310  is an assumed point for purposes of this discussion. A red phosphor is also selected that falls at coordinate point 0.6, 3.5. Assume then that the 20% point falls at point  311 . The triangle that is formed between line  302  (which connects the selected diode with the green selected phosphor) and line  303  (which connects the selected diode with the red selected phosphor and line  304  that connects the two phosphor percentage points now bounds the color that will be observed when the blue diode impacts the selected phosphors that are held in the encapsulate material as discussed with respect to  FIGS. 1 and 2 . This then provides blended colors that are not otherwise attainable. By changing the power to the selected diode the resultant output color can change. 
     More than two phosphors can be selected using the scheme discussed herein. Also, more than one diode can be used and by selectively activating different LED chips, and by selectively changing LED chip power level in proximity to different phosphors, a user can select the ultimate color(s) of the device or display. Using this arrangement a full spectrum of colors can be achieved, both on the border of the CIE chart as well as in the center region. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.