Dynamic power and brightness control for a display screen

Abstract

An image is displayed on an electronic display device at a reduced power level. Power used by the display device is maintained below a predetermined maximum power level by uniformly scaling the initial optical intensity of an image to a lower optical intensity whenever displaying the image at the initial optical intensity would result in power consumption of the display device exceeding the predetermined maximum power level.

We claim: 
     
         1 . A method of displaying an image on an electronic display system, comprising:
 receiving frames of image data to be displayed, wherein the image data includes an optical output intensity of each pixel and subpixel of a display device of the display system to produce the image or frame and the sub-pixels are red, green, and blue subpixels;   determining an average power level for displaying one or more frames of image data, wherein the average power level is defined as the ratio of the power required by the display device to produce an image at the power required by the display device to produce a fully white screen;   determining an adjusted optical output intensity for each pixel and subpixel as a function of the average power level and the optical output intensity of each subpixel;   adjusting a parameter of the electronic display system in accordance with the average power level, wherein adjusting a parameter comprises scaling the brightness of each pixel and subpixel to the adjusted optical output intensity; and   wherein the electronic display system includes multiple display devices each with a light source and wherein each light source produces a portion of the image data.   
     
     
         2 . The method of  claim 1 , wherein the average power level is determined based on a single frame of image data. 
     
     
         3 . The method of  claim 1 , wherein the average power level is determined based on multiple frames of image data. 
     
     
         4 . The method of  claim 3 , wherein the parameter is continuously set each time a frame of image data is displayed, based on the average power level that is determined from a running average of the multiple frames of image data. 
     
     
         5 . The method of  claim 1 , wherein said adjusting includes scaling down a brightness level of the electronic display system. 
     
     
         6 . The method of  claim 5 , wherein the brightness level of the electronic display system is scaled down in accordance with a function that maps target brightness levels to average power levels. 
     
     
         7 . The method of  claim 1 , wherein said adjusting includes scaling down a power level of the electronic display system. 
     
     
         8 . The method of  claim 7 , wherein the power level of the electronic display system is scaled down in accordance with a function that maps target power levels to average power levels. 
     
     
         9 . The method of  claim 1 , wherein the parameter is adjusted so as to maintain a desired gamma. 
     
     
         10 . The method of  claim 1 , wherein the average power level is defined by the following equation: 
       
         
           
             
               APL 
               = 
               
                 
                   ∑ 
                   
                     i 
                     = 
                     1 
                   
                   
                     i 
                     = 
                     N 
                   
                 
                  
                 
                   
                     I 
                     i 
                   
                   * 
                   
                     1 
                     
                       255 
                       * 
                       N 
                     
                   
                 
               
             
           
         
         where N is the total number of subpixels of the display device and I is the intensity of optical output of a subpixel (measured in DAC counts).