Abstract:
A content-adaptive adjustment system and method for a light-emitting display is disclosed. An analysis unit analyzes, for example, the average data intensity/power consumption and the data distribution of the image data to be displayed. An adjustment unit then adjusts, for example, the pixel values of the image data or the drive levels of the light-emitting display according to the analyzed data distribution, such that the consumed power in the light-emitting display could be considerably reduced.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to organic light-emitting diode (OLED) display, and more particularly to adjusting the driving current of the OLED display. 
         [0003]    2. Description of the Prior Art 
         [0004]    The organic light-emitting diode (OLED) has recently received more attention and application in the field of the flat panel display, in television screens, computer displays, and portable electronic device screens. A primary benefit of the OLED over other flat panel displays is that the OLED itself emits light of different colors and therefore does not involve the backlight and color filter as required, for example, in the liquid crystal display (LCD). Further, the OLED display can be more effectively manufactured in process and in cost. Nevertheless, the significant drawback of the OLED is the limited lifetime of the organic materials prone to degradation compared to the LCD, for example. 
         [0005]    The OLED-based display is operated in a current driving manner, and therefore the resistance in the circuit causes a significant voltage drop (or IR drop) problem and heat loss issue. Accordingly, the operation efficiency, particularly the power efficiency, of the OLED-based display becomes low. 
         [0006]    For the foregoing reasons, a need has arisen to propose a novel scheme for the OLED display that not only decreases the voltage drop problem and the heat loss issue, but also increases the power efficiency to save power consumption. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the foregoing, it is an object of the present invention to alleviate the voltage drop problem and the heat loss issue, to save power consumption, and to lengthen the lifetime of the OLED display. 
         [0008]    According to the embodiment of the present invention, a content-adaptive adjustment system and method for a light-emitting display is disclosed. An analysis unit analyzes, for example, the average data intensity/power consumption and the data distribution of the image data to be displayed. An adjustment unit then adjusts, for example, the pixel values of the image data or the drive levels of the light-emitting display according to the analyzed data distribution, such that the consumed power in the light-emitting display could be considerably reduced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1A  illustrates a content-adaptive adjustment system for an organic light-emitting diode (OLED) display according to one embodiment of the present invention; 
           [0010]      FIG. 1B  illustrates a flow of the analysis unit in  FIG. 1A ; 
           [0011]      FIG. 2A  and  FIG. 2B  show exemplary and simplified examples illustrating the data distributions analysis in  FIG. 1B ; 
           [0012]      FIG. 3  shows exemplary tone curves according to one embodiment of the present invention; and 
           [0013]      FIG. 4  shows an exemplary reference-voltage generating circuit according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 1A  illustrates a content-adaptive adjustment system  10  for an organic light-emitting diode (OLED) display according to one embodiment of the present invention. While the OLED display is addressed here, the content-adaptive adjustment system  10  of the present invention can be adapted to another emissive-type display that itself emits light without requiring a backlight or other light source. The content-adaptive adjustment system  10  includes an automatic current limiter (ACL)  12 , which receives image data  14  and then outputs the resultant image on the OLED display  16 . 
         [0015]    The ACL  12  includes an analysis unit  120  for analyzing characteristics of the received image data. In this specification, the term unit is configured to denote a circuit, a piece of program, or their combination.  FIG. 1B  illustrates a flow of the analysis unit  120  according to one embodiment of the present invention. In the embodiment, the intensity of the received image data  14  is analyzed in step  1201 , to obtain, for example, the average data intensity of a frame. Alternatively, the power consumption of the OLED display  16  is analyzed in step  1202 , to obtain, for example, the average power consumption of a frame. 
         [0016]    According to the embodiment of the present invention, customer specification or requirement (block  18 ) is provided. In the embodiment, the image data, among others, provided by the customer are examined. The examination of the image data is usually performed off line. As a result, a number of data pairs are obtained (in block  124 ), each representing average data intensity and its associated gain. The gain value is, for example, a positive number less than 1. In general, greater average data intensity associates with a lesser gain, and vice versa. These data pairs are stored, for example, as a lookup table in a storage device. Subsequently, a determination unit  122  determines the gain applied to each pixel value according to the average data intensity (from step  1201 ) or the average power consumption (from step  1202 ), with respect to the lookup table  124 . In other words, given an average value from the block  120 , the determination unit  122  then retrieves an associated gain value from the lookup table  124 . 
         [0017]    Referring back to  FIG. 1B , in step  1204 , the image data may be subjected to further analysis to determine data distribution.  FIG. 2A  and  FIG. 2B  show exemplary and simplified examples illustrating the data distributions analysis. For the case exemplified in  FIG. 2A , the ratio between the white area and the black area is small (e.g., 0.05), or the overall average data intensity is small, as represented in the accompanied histogram. On the other hand, for the case exemplified in  FIG. 2B , the ratio between the white area and the black area is large (e.g., about 1), or the overall average data intensity is large, as represented in the accompanied histogram. Subsequently, an adjustment unit  126  ( FIG. 1A ) is utilized to adjust the pixel values according to the data distribution. For better understanding the adjustment, please refer to the case illustrated in  FIG. 2A . As the ratio of the white area to the black area in  FIG. 2A  is determined to be very small in the step  1204  ( FIG. 1B ), the adjustment unit  126  then performs some adjustment, for example by using conventional digital image processing technique, on the white pixel values. The resultant adjusted pixel values are shown as dotted line in the accompanied histogram. Accordingly, the white pixel values are shifted somewhat to grey pixel values. As the OLED display inherently has a higher contrast compared to other flat panel display, the adjustment in  FIG. 2A  has little visual effect on the contrast of the image perceived by human eyes, but this adjustment somewhat reduces the driving current, and thus the consumed power. This reduction in consumed power not only alleviates the heat loss issue, but also lengthens the lifetime of the OLED display. Please further refer to the case illustrated in  FIG. 2B . As the ratio of the white area to the black area in  FIG. 2B  is determined to be large enough in the step  1204  ( FIG. 1B ), the adjustment unit  126  then performs substantive adjustment on the white pixel values with adjustment extent greater than that in  FIG. 2A . The resultant adjusted pixel values are shown as dotted line in the accompanied histogram. As discussed above, the adjustment in  FIG. 2B  has little visual effect on the contrast of the image perceived by human eyes, but substantially reduces the driving current, and thus the consumed power. 
         [0018]    The performance of the adjustment unit  126  may be, in general, represented by a tone curve as exemplified in  FIG. 3 . In the figure, the horizontal axis represents the tones of the original input image, and the vertical axis represents the tones of the adjusted output image. The dotted linear line  1240  indicates that no adjustment is done. The exemplary curve  1242  indicates that the high grey levels are tone remapped to a lower level, while the low grey levels are substantially maintained. 
         [0019]    According to another embodiment of the present invention, the adjustment unit  126 , in accordance with the results of the analysis unit  120 , is utilized to adjust the drive levels of a reference-voltage generating circuit of a display driver, instead of adjusting the pixel values in the previous embodiment.  FIG. 4  shows an exemplary reference-voltage generating circuit or a Gamma generating circuit, in which the reference voltages are generated according to the results of the analysis unit  120 . The drive-level adjustment in the adjustment unit  126  or the reference-voltage generating circuit is performed in a manner such that it has little visual effect on the contrast of the image perceived by human eyes, while substantially reduces the consumed power. This reduction in consumed power not only alleviates the heat loss issue, but also lengthens the lifetime of the OLED display. Compared to the previous embodiment, the present embodiment performs the content-adaptive adjustment on the drive levels rather than pixel values as in the previous embodiment. The present embodiment is implemented by an analog circuit rather than a digital image processor as in the previous embodiment. 
         [0020]    Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.