Liquid crystal display with color backlighting employing light emitting diodes

Abstract

A color display device ( 210, 310, 410 ) includes a backlight ( 214, 414 ) that cyclically emits first, second, and third component color backlighting in turn over a cycle period. The cycle period repeats at a cycling frequency (f) that exceeds a maximum human visual response frequency. A liquid crystal display (LCD) ( 112, 312, 412 ) generates a first display during the first component color backlighting, a second display during the second component color backlighting, and a third display during the third component color backlighting.

1 . A color display device including: 
 a light-transmissive liquid crystal display (LCD);    a backlight arranged to illuminate the light-transmissive LCD, the backlight including at least a two-dimensional array of first color component light emitting diodes (first color component LEDs), a two-dimensional array of second color component light emitting diodes (second color component LEDs) distributed amongst the first color component LEDs, and a two-dimensional array of third color component light emitting diodes (third color component LEDs) distributed amongst the first and second color component LEDs;    LED circuitry that cyclically alternates between powering the first color component LEDs to produce first color component backlighting, powering the second color component LEDs to produce second color component backlighting, and powering the third color component LEDs to produce third color component backlighting; and    LCD circuitry that updates a display shown on the LCD, the updates being synchronized with color changes of the backlight.    
   
   
       2 . The color display device as set forth in  claim 1 , wherein the first, second, and third color component LEDs are arranged as a two-dimensional array of LED pixels, each LED pixel including at least one first color component LED, a at least one second color component LED, and at least one third color component LED, the LED pixels corresponding to pixels of the light-transmissive LCD.  
   
   
       3 . The color display device as set forth in  claim 1 , wherein each LED of the backlight corresponds with a pixel of the light-transmissive LCD.  
   
   
       4 . The color display device as set forth in  claim 1 , wherein the first color component LEDS, second color component LEDs, and third color component LEDS do not correspond with pixels of the light-transmissive LCD.  
   
   
       5 . A color display device including: 
 a light-transmissive liquid crystal display (LCD); 
 an array of LEDs defining a backlight for the LCD, the array of LEDs including a plurality of groups of LEDs producing light of different colors, the LEDs of each group of LEDs being distributed two-dimensionally across a display area of the LCD;  
 LED circuitry that selectively powers each group of LEDs in turn to produce a temporally varying backlight color that cycles through the different colors produced by the groups of LEDs with a frequency higher than a human visual response frequency; and  
 LCD circuitry that updates opacity of pixels of the light-transmissive LCD in synch with the temporally varying backlight color to produce a color display.  
   
   
   
       6 . The color display device as set forth in  claim 5 , wherein the pixels of the light-transmissive LCD do not include color filters.  
   
   
       7 . The color display device as set forth in  claim 5 , wherein the groups of LEDs include groups of LEDs producing at least light of red, green, and blue primary colors.  
   
   
       8 . The color display device as set forth in  claim 7 , wherein the group of LEDs producing the blue primary color produce relatively lower light intensity than the group of LEDs producing the red primary color, and the LED circuitry powers the group of LEDs producing the blue primary color for a relatively longer duration than it powers the group of LEDs producing the red primary color.  
   
   
       9 . The color display device as set forth in  claim 7 , wherein the LEDs of the group of LEDs producing the blue primary color produce relatively lower light intensity than the LEDs of the group of LEDs producing the red primary color, and the number of LEDs in the group of LEDs producing the blue primary color is larger than the number of LEDs in the group of LEDs producing the red primary color to compensate for the relatively lower light intensity of the LEDs producing the blue primary color.  
   
   
       10 . The color display device as set forth in  claim 5 , wherein the light-transmissive LCD is relatively more absorbing for light of a first color produced by a first group of LEDs of the array of LEDS compared with light of a second color produced by a second group of LEDs of the array of LEDS, and an illumination intensity of the first group of LEDs is greater than an illumination intensity of the second group of LEDs to compensate for the color-dependent absorption of the LCD.  
   
   
       11 . The color display device as set forth in  claim 5 , wherein the LEDs of the array of LEDs are arranged to define backlight pixels, each backlight pixel including at least one LED from each group of LEDs.  
   
   
       12 . The color display device as set forth in  claim 11 , wherein each backlight pixel is optically coupled with at least one corresponding LCD pixel, the corresponding LCB pixel operating in conjunction with the temporally varying backlight color produced by the optically coupled backlight pixel as a full-color LCD pixel.  
   
   
       13 . The color display device as set forth in  claim 5 , wherein each LED of the array of LEDs is optically coupled with a corresponding LCD pixel.  
   
   
       14 . The color display device as set forth in  claim 5 , wherein there is no particular correspondence between particular LEDs of the array of LEDs and pixels of the LCD.  
   
   
       15 . The color display device as set forth in  claim 14 , further including: 
 a waveguiding material disposed between the array of LEDs and the light transmissive LCD.    
   
   
       16 . The color display device as set forth in  claim 15 , wherein the waveguiding material includes light scattering centers that distribute light generated by the array of LEDs.  
   
   
       17 . The color display device as set forth in  claim 5 , wherein each LCD pixel operates in conjunction with the temporally varying backlight color as a full-color pixel.  
   
   
       18 . The color display device as set forth in  claim 5 , wherein the LEDs of the array of LEDs are selected from a group consisting of semiconductor light emitting diodes, organic light emitting diodes, and semiconductor lasers.  
   
   
       19 . A color display device including: 
 a light-transmissive liquid crystal display (LCD); 
 a two-dimensional array of LEDs arranged parallel with the LCD to backlight the LCD, the two-dimensional array of LEDs including a plurality of groups of LEDs producing light of different colors, the LEDs of each group of LEDs being distributed two-dimensionally across a display area of the LCD;  
   a waveguiding material disposed between the two-dimensional array of LEDs and the parallel light-transmissive LCD to optically couple the two-dimensional array of LEDs with the LCD; 
 LED circuitry that selectively powers each group of LEDs in turn to produce a temporally varying planar backlight color that cycles through the different colors produced by the groups of LEDs with a frequency higher than a human visual response frequency; and  
 LCD circuitry that updates opacity of pixels of the light-transmissive LCD in synch with the temporally varying planar backlight color to produce a color display.