Spatial light modulation display system

Abstract

An improved spatial light modulation display system includes light sources for providing red, green, and blue light. A system controller includes functionality for controlling a color balance of the red, green, and blue light. A sensor is provided for sensing light from each of the light sources. The controller can detect a shift in color balance based on the intensity of light sensed by the sensor. If the sensor output indicates that the sensor is operating out of a desirable range, the spatial light modulator can modulate the light in order change the brightness of light sensed by the sensor. The modulation pattern can be varied until the sensor output is a specified value or within a specified range of values. In a preferred embodiment, the sensor is located to receive off-state light from the spatial light modulator so as to avoid obstruction of light used for displaying images.

1 . A display system comprising: 
 a plurality of light sources;    a spatial light modulator located to receive light from at least one of the plurality of light sources, the spatial light modulator including a plurality of independently controllable elements that can be controlled to direct received light in one of a first direction for display and a second direction for non-display;    a light sensor located to receive light directed in the second direction from elements of the spatial light modulator and issue a brightness signal indicative of the intensity of the received light; and    a processing device for detecting a color balance ratio based at least in part on the brightness signal issued by the light sensor.    
   
   
       2 . A display system according to  claim 1 , further comprising an analog to digital converter for converting the brightness signal into digital brightness data and providing the digital brightness data to the processing device.  
   
   
       3 . A display system according to  claim 1 , further comprising a light source controller for controlling activation of the plurality of light sources according to instructional color data received from the processing device.  
   
   
       4 . A display system according to  claim 1 , wherein the plurality of light sources comprises a first LED array for emitting blue light, a second LED array for emitting green light, and a third LED array for emitting red light.  
   
   
       5 . A display system according to  claim 1 , wherein the plurality of light sources comprises a first LED array for emitting red and blue light and a second LED array for emitting green light.  
   
   
       6 . A display system according to  claim 1 , wherein the plurality of light sources include a light source for emitting red light, a light source for emitting green light, and a light source for emitting blue light, wherein the color balance ratio detected by the processing device is a ratio of red, green, and blue.  
   
   
       7 . A display system according to  claim 1 , a processing device determines whether the detected color balance ratio is equal to a specified color balance ratio.  
   
   
       8 . A display system according to  claim 7 , wherein the processing device adjusts an output of at least one of the plurality of light sources if it is determined that the detected color balance ratio is not equal to the specified color balance ratio.  
   
   
       9 . A display system according to  claim 1 , wherein the spatial light modulator comprises a digital micromirror device.  
   
   
       10 . A display system according to  claim 1 , comprising a second spatial light modulator located to receive light from another of the plurality of light sources, the second spatial light modulator including a plurality of independently controllable elements that can be controlled to direct received light in one of a third direction for display and a fourth direction for non-display.  
   
   
       11 . A display system according to  claim 10 , wherein the light sensor is located to also receive light directed in the fourth direction from the controllable elements of the second spatial light modulator.  
   
   
       12 . A display system according to  claim 10 , further comprising a second light sensor located to receive light directed in the fourth direction from the controllable elements of the second spatial light modulator.  
   
   
       13 . A display system comprising: 
 a plurality of light sources;    a spatial light modulator located to receive light from at least one of the light sources, the spatial light modulator including a plurality of independently controllable elements that can be controlled to direct light in one of a first direction for display and a second direction for non-display;    a light sensor for receiving light directed from elements of the spatial light modulator and outputting a brightness signal based on the intensity of the received light; and    a processing device for controlling the spatial light modulator to modulate the light received from at least one of the light sources so that the brightness signal output from the light sensor is within a specified range of values.    
   
   
       14 . A display system according to  claim 13 , wherein the light sensor is located to receive light directed in the second direction from elements of the spatial light modulator.  
   
   
       15 . A display system according to  claim 13 , wherein the processing device controls the spatial light modulator to modulate the light according to a blue-noise pattern.  
   
   
       16 . A display system according to  claim 13 , wherein the processing device determines whether the brightness signal is within the specified range of values, and changes a modulation pattern used by the spatial light modulator to modulate the light if the brightness signal is not within the specified range of values.  
   
   
       17 . A display system according to  claim 13 , wherein the processing device controls the spatial light modulator to modulate the light so that the brightness signal output from the light sensor is a particular value within the specified range of values.  
   
   
       18 . A method of controlling color balance comprising: 
 controlling a spatial light modulator to direct light from a light source in an off-state direction for non-display;    sensing an intensity of light directed in the off-state direction from elements of the spatial light modulator; and    detecting a color balance ratio based at least in part on the sensed intensity.    
   
   
       19 . A method according to  claim 18 , further comprising converting the brightness signal into digital brightness data and providing the digital brightness data to a processing device.  
   
   
       20 . A method according to  claim 18 , wherein the light source is one of a plurality of light sources, wherein the plurality of light sources comprise a light source for emitting red light, a light source for emitting green light, and a light source for emitting blue light, wherein the detecting of the color balance ratio includes detecting a ratio of red, green, and blue.  
   
   
       21 . A method according to  claim 18 , further comprising determining whether the detected color balance ratio is equal to a specified color balance ratio.  
   
   
       22 . A method according to  claim 21 , wherein the light source is one of a plurality of light sources, further comprising adjusting an output of at least one of the plurality of light sources if it is determined that the detected color balance ratio is not equal to the specified color balance ratio.  
   
   
       23 . A method of controlling color balance comprising: 
 controlling a spatial light modulator to direct light from a light source in at least one of an on-state direction for display and an off-state direction for non-display;    sensing an intensity of light directed from the spatial light modulator;    outputting a brightness signal based on the sensed intensity of the light; and    controlling the spatial light modulator to modulate the light directed in at least one of the on-state direction and the off-state direction so that the brightness signal is within a specified range of values.    
   
   
       24 . A method according to  claim 23 , wherein, in the sensing of the intensity of light, said light is directed from the spatial light modulator in the off-state direction.  
   
   
       25 . A method according to  claim 23 , wherein the controlling of the spatial light modulator to modulate the light includes controlling the spatial light modulator to modulate the light according to a blue-noise pattern.  
   
   
       26 . A method according to  claim 23 , further comprising determining whether the brightness signal is within the specified range of values, and changing a modulation pattern used by the spatial light modulator to modulate the light if the brightness signal is not within the specified range of values.  
   
   
       27 . A method according to  claim 23 , further comprising controlling the spatial light modulator to modulate the light so that the brightness signal is a particular value within the specified range of values.  
   
   
       28 . A method of controlling color balance comprising: 
 (a) controlling a spatial light modulator to direct light from a first light source of a first color in an off-state direction and to direct light from a second light source of a second color in an on-state direction;    (b) sensing a first intensity level of the light from the first light source directed in the off-state direction;    (c) controlling the spatial light modulator to direct light from the second light source in the off-state direction and to direct light from the first light source in the on-state direction;    (d) sensing a second intensity level of light from the second light source directed in the off-state direction;    (e) determining an intensity ratio based at least in part on the thus sensed first and second sensed intensity levels; and    (f) adjusting control of the first and second light sources as needed according to the thus determined intensity ratio to attain a specified color balance.    
   
   
       29 . A method according to  claim 28 , further comprising: 
 (g) detecting whether at least one of the first and second intensity levels is out of a specified range; and    (h) if the first intensity level is detected to be out of range, performing steps of: 
 (h1) controlling the spatial light modulator to direct only a portion of light from the first light source in the off-state direction according to a specified calibration pattern and to direct light from the second light source of a second color in an on-state direction, and  
 (h2) sensing a third intensity level of the portion of the light from the first light source directed in the off-state direction; and  
   (i) if the second intensity level is detected to be out of range, performing steps of: 
 (i1) controlling the spatial light modulator to direct only a portion of light from the second light source in the off-state direction according to the specified calibration pattern and to direct light from the first light source in an on-state direction, and  
 (i2) sensing a fourth intensity level of the portion of the light from the first light source directed in the off-state direction.  
   
   
   
       30 . A method according to  claim 28 , wherein: 
 step (a) includes controlling the spatial light modulator to direct light from a third light source of a third color in the on-state direction, and    step (c) includes controlling the spatial light modulator to direct light from a third light source of a third color in the on-state direction;    further comprising:    (j) controlling the spatial light modulator to direct light from the third light source in the off-state direction and to direct light from the first and second light sources in the on-state direction, and    (k) sensing a third intensity level of the light from the third light source directed in the off-state direction;    wherein:    step (e) includes determining said intensity ratio based at least in part on the thus sensed first, second, and third sensed intensity levels, and    step (f) includes adjusting control of the third light source as needed according to the thus determined intensity ratio to attain a specified color balance.