Abstract:
A method and apparatus for gamma correction and a flat panel display using the same. Weighted values corresponding to red, green and blue of an image signal are respectively evaluated to determine the dominant color in the image signal, and a Gamma correction based on the dominant color is then performed, thereby obtaining displaying quality similar with that obtained by independently performing red, green, or blue Gamma correction.

Description:
BACKGROUND  
       [0001]     The invention relates to a method and apparatus for Gamma correction, and more particularly, to a Gamma correction method and apparatus for use in a flat panel display.  
         [0002]     Gamma correction is widely adopted to function for improving image display quality in flat panel displays. Conventional source driver circuits in a flat panel display, however, comprise only a resistor string for generating reference voltage, thus Gamma can not be individually corrected for red, green and blue. Therefore a room temperature gray level gamma curve is taken as the basis for the Gamma correction voltage.  
         [0003]      FIG. 1  shows gray level, red, green and blue Gamma curves at room temperature, wherein “W” indicates the gray level. Obviously the Gamma curve varies by color, thus the display quality of the flat panel display may be diminished due to color distortion when the gray level Gamma curve is the only basis for Gamma correction.  
       SUMMARY  
       [0004]     Embodiments of the invention therefore provide a method and apparatus for Gamma correction. The weighted values corresponding to red, green and blue of an image signal are respectively evaluated to determine the dominant color in the image signal, and a Gamma correction based on the dominant color is then performed; thereby obtaining display quality similar to that obtained by Gamma correction individually performed for red, green, or blue.  
         [0005]     An embodiment of the invention provides a Gamma correction method for use in a flat panel display. First, weighted values of a first color, a second color and a third color in an image signal are obtained, and a dominant color is determined accordingly. Thereafter, a reference voltage corresponding to the dominant color is determined for performing the Gamma correction for the flat panel display.  
         [0006]     The step of determining the reference voltage comprises the following steps. First, reference voltage tables of the first, second and third colors are provided, and one of the reference voltage tables is selected according to the dominant color. Thereafter, the value of reference voltage is looked up in the selected reference voltage table.  
         [0007]     The step of determining the reference voltage alternatively comprises the following steps. First, a memory unit for storing configurations of the first, the second and the third colors is provided. A programmable reference voltage table generator is provided, and the configuration corresponding to the dominant color is obtained from the memory unit. Thereafter, the configuration of the dominant color is input to the programmable reference voltage table generator to generate the reference voltage.  
         [0008]     Another embodiment of the invention provides a Gamma correction device for use in a flat panel display. The Gamma correction device comprises a capture unit, a first color reference voltage table, a second color reference voltage table, a third color reference voltage table, and a selector. The capture unit receives an image signal and obtains weighted values of a first color, second color and third color therein. The selector, coupled to the first, second and third color reference voltage tables, selects one table and outputs a reference voltage corresponding thereto.  
         [0009]     Another embodiment of the invention provides a Gamma correction device for use in a flat panel display. The Gamma correction device comprises a capture unit, a memory unit, a programmable reference voltage table generator. The capture unit receives an image signal and obtains weighted values of a first color, a second color and a third color therein. The memory unit stores configurations of the first, the second and the third colors, and is capable of determining a dominant color according to the weighted values, and outputting the configuration of the dominant color. The programmable reference voltage table generator for receiving the configuration of the dominant color generates corresponding reference voltage. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The following detailed description, given by way of example and not intended to limit the invention solely to the embodiments described herein, will best be understood in conjunction with the accompanying drawings, in which:  
         [0011]      FIG. 1  shows gray level, red, green and blue Gamma curves at room temperature;  
         [0012]      FIG. 2  is a block diagram of a flat panel display according to an embodiment of the invention;  
         [0013]      FIG. 3  is block diagram of a gamma correction device according to an embodiment of the invention;  
         [0014]      FIG. 4  is block diagram of a gamma correction device according to an embodiment of the invention; and  
         [0015]      FIG. 5  is block diagram of a gamma correction device according to an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     A detailed description of embodiments of the invention is provided in the following.  
         [0017]      FIG. 2  is a block diagram of a flat panel display according to an embodiment of the invention. The flat panel display  2  comprises a gamma correction device  20 , a data driver  22 , a scan driver  24  and a display panel  26 . The Gamma correction device  20  first determines a dominant color that has the greatest weight among the three primary colors, and then outputs corresponding Gamma correction voltage V G  to the data driver  22 . The data driver  22  receives the image signal and the Gamma correction voltage V G , and the display panel  26  is driven by the data driver  22  and scan driver  24 . The flat panel display  2  can be a liquid crystal display, or any flat panel display capable of applying Gamma correction.  
       First Embodiment  
       [0018]     The first embodiment of the invention provides a Gamma correction method for a flat panel display. First, image signal is analyzed to evaluate weighted values of red, green and blue. Based on the weighted values, a dominant color can then be determined. A reference voltage corresponding to the dominant color can then be determined for Gamma correction.  
         [0019]     The process of determining the reference voltage corresponding to the dominant color comprises the following steps. First, red, green and blue reference voltage tables are provided. One of the tables is then selected according to the dominant color, for lookup of the reference voltage.  
         [0020]      FIG. 3  is block diagram of a gamma correction device according to this embodiment. The Gamma correction device  20  comprises a capture unit  200 , a red reference voltage table  202 , a green reference voltage table  204 , a blue reference voltage table  206  and a selector  210 . The capture unit  200  receives an image signal and evaluates weighted values of the red, green and blue colors in the image signal. The selector  210  coupled to the red reference voltage table  202 , green reference voltage table  204  and blue reference voltage table  206 , selects one table according to the weighted values for output of a reference voltage.  
         [0021]     The selector  210 , for example, can be a multiplexer. If in the image signal, the red color has the greatest weighted value among the three primary colors, the multiplexer outputs the reference voltage looked up in the red reference voltage table  202 , to drive the data driver  22 .  
         [0022]     Additionally, a gray level reference voltage table  208  can be provided at room temperature. If the weighted values of red, green and blue colors are substantially even, the multiplexer can choose the reference voltage looked up in the gray level reference voltage table  208  for output.  
       Second Embodiment  
       [0023]     Alternatively, another embodiment of a method for determining the reference voltage corresponding to the dominant color is provided.  
         [0024]     First a memory unit is provided, storing at least three configuration sets of red, green and blue and a programmable reference voltage table generator is also provided. According to the dominant color, a corresponding configuration of the dominant color is then obtained from the memory unit. Thereafter, the configuration of the dominant color is input to the programmable reference voltage table generator for generating the reference voltage.  
         [0025]      FIG. 4  shows the Gamma correction device  20  according to this embodiment of the invention. The Gamma correction device  20  comprises a capture unit  200 , a memory unit  220  and a programmable reference voltage generator  222 . The capture unit  200  receives an image signal and evaluates the weighted values of red, green and blue colors therein. The memory unit  220  stores at least three configuration sets corresponding to red, blue, and green, one of which is chosen for output as the configuration of the dominant color based on the weighted values. The programmable reference voltage generator  222  receives the configuration of the dominant color, and accordingly generates the reference voltage.  
         [0026]     In this embodiment, the memory unit  220  can be an EEPROM, and the stored configurations can be red reference voltage table  202 , green reference voltage table  204 , blue reference voltage table  206  and gray level reference voltage table  208 . The weighted values of the red, green and blue colors are taken as a basis for choosing a corresponding reference voltage table.  
         [0027]     The programmable reference voltage generator  222 , for example, can be a programmable Gamma buffer for receiving the reference voltage table corresponding to the dominant color, and generating the reference voltage corresponding to the dominant color.  
         [0028]     If the red color has the greatest weighted value in the image signal, the capture unit  200  outputs corresponding control signal (or addressing signal), and the red reference voltage table  202  is then obtained from memory unit  220 . The programmable Gamma buffer analogizes a digital voltage in the red reference voltage table  202  to obtain a red reference voltage, for driving the  22 .  
       Third Embodiment  
       [0029]     Flat panel displays, such as liquid crystal displays, typically employ multi-tube backlight modules, thus generating relatively high environmental temperature. In order to compensate for the Gamma curve shift due to environmental temperature variation, a temperature sensor  224  can be added to the flat panel display or the Gamma correction device, as shown in  FIG. 5 .  
         [0030]     The memory unit  220  obtains the configuration of the dominant color based on the weighted values and the temperature detection result provided by the temperature sensor  224 .  
         [0031]     In this embodiment, the memory unit  220  stores three sets of red reference voltage tables  202  R 1  to R 3 , three sets of green reference voltage tables  204  G 1  to G 3 , and three sets of blue reference voltage tables  206  B 1  to B 3 , each corresponding to a different environmental temperature range.  
         [0032]     If red in the image signal has the greatest weighted value, the red reference voltage tables  202  R 1  to R 3  in the memory unit  220  are chosen first. The temperature sensor  224  chooses the most appropriate reference voltage tables from the R 1  to R 3  by detecting environmental temperature.  
         [0033]     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.