Abstract:
A display device includes a gamma adjustment circuit employing a method for adjusting red, green, blue (R, G, B) data of an image signal. The gamma adjustment circuit provides at least one look up table (LUT) to store gamma correction values, determines whether at least two kinds of color data from the R, G, B data require adjustment, searches for gamma correction values corresponding to the at least two kinds of color data from the R, G, B data requiring adjustment in the at least one LUT, and outputs the R, G, B data and the gamma correction values corresponding to the at least two kinds of color data from the R, G, B data requiring adjustment.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure generally relates to display devices, and particularly to a gamma adjustment circuit and method, and a display device using the same. 
         [0003]    2. Description of Related Art 
         [0004]    With widespread use of display devices, high display quality is increasingly prioritized. Accordingly, a gamma adjustment circuit for adjusting chroma of a display device has been developed and employed by the display devices. 
         [0005]    A frequently used gamma adjustment circuit includes a control circuit, a first look up table (LUT) for storing gamma correction values corresponding to red image data (R data), a second LUT for storing gamma correction values corresponding to green image data (G data), and a third LUT for storing gamma correction values corresponding to blue image data (B data). The control circuit receives R, G, B data of an image signal, searches for corresponding gamma correction values respectively from the first, second and third LUTs according to the R, G, B data, and adjusts the R, G, B data. 
         [0006]    However, some of the R, G, B data remains unchanged after adjustment in operation. That is, some image data requires no adjustment, or even unadjusted data has no effect on display quality of a display device. Therefore, the gamma adjustment circuit employing three LUTs results a waste of storage space. 
         [0007]    What is needed, therefore, is a gamma adjustment circuit, a gamma adjustment method and a display device employing the same which can overcome the described limitations. 
       SUMMARY 
       [0008]    A gamma adjustment circuit for processing R, G, B data of an image signal includes at least one LUT to store gamma correction values, a determination circuit to determine whether at least two kinds of color data from the R, G, B data require adjustment, and a control circuit to search for gamma correction values corresponding to the at least two kinds of color data from the R, G, B data requiring adjustment in the at least one LUT and output the R, G, B data and the gamma correction values corresponding to the at least two kinds of color data from the R, G, B data requiring adjustment. 
         [0009]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views, and all the views are schematic. 
           [0011]      FIG. 1  is a schematic circuit block diagram of one embodiment of a gamma adjustment circuit, the gamma adjustment circuit including a first LUT. 
           [0012]      FIG. 2  is a schematic diagram of one embodiment of the first LUT of  FIG. 1 . 
           [0013]      FIG. 3  is a flowchart of one embodiment of a method for processing R data of an image signal by the gamma adjustment circuit of  FIG. 1 . 
           [0014]      FIG. 4  is a flowchart of one embodiment of a method for processing G data of the image signal by the gamma adjustment circuit of  FIG. 1 . 
           [0015]      FIG. 5  is a schematic circuit block diagram of another embodiment of a gamma adjustment circuit. 
           [0016]      FIG. 6  is a schematic circuit block diagram of one embodiment of a display device. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Reference will now be made to the drawings to describe various embodiments in detail. 
         [0018]    Referring to  FIG. 1 , a schematic circuit block diagram of one embodiment of a gamma adjustment circuit is shown. The gamma adjustment circuit  100  receives R, G, B data of an image signal, respectively processes the R, G, B data, and outputs an adjusted image signal. The gamma adjustment circuit  100  includes a determination circuit  110 , a control circuit  120 , a first LUT  130 , a second LUT  140 , a processing circuit  150 , and an output circuit  160 . 
         [0019]    The determination circuit  110  receives the R data and the G data (or data of any other two colors) of the image signal, and determines whether the R data and the G data respectively require gamma correction according to corresponding gray levels of the R data and the G data. When any one or both of the R data and the G data require gamma correction, the determination circuit  110  outputs an address signal corresponding to the R data or the G data or outputs address signals respectively corresponding to the R data and the G data to the control circuit  120 . When neither of the R data or the G data require gamma correction, the determination circuit  110  outputs an output signal corresponding to the R data or the G data or outputs output signals respectively corresponding to the R data and the G data to the control circuit  120 . The determination circuit  110  includes a first comparison circuit  112 , a second comparison circuit  116 , a first address generating circuit  114 , and a second address generating circuit  118 . The first comparison circuit  112  and the first address generating circuit  114  process the R data, so as to output a first address signal or a first output signal corresponding to the R data, and the second comparison circuit  116  and the second address generating circuit  118  process the G data, so as to output a second address signal or a second output signal corresponding to the G data. 
         [0020]    The first LUT  130  stores gamma correction values corresponding to part gray scales of the R data in a first predetermined range and part gray scales of the G data in a second predetermined range. That is, the gamma correction values stored in the first LUT  130  merely correspond to part gray scales of the R data and part gray scales of the G data. Referring to  FIG. 2 , a schematic diagram showing a relationship between the gamma correction values and the addresses respectively corresponding to the gamma correction values of the first LUT  130  is shown. The R data in the first predetermined range include a first starting gray scale and a first ending gray scale, and the G data in the second predetermined range include a second starting gray scale and a second ending gray scale. For example, the addresses 0X00 and 0X01 can respectively store the first starting gray scale and the first ending gray scale, and the addresses 8X00 and 8X01 can respectively store the second starting gray scale and the second ending gray scale. Thus, the addresses from 0X02 to 7XF respectively store the gamma correction values corresponding to the gray scales of the R data from the first starting gray scale to first ending gray scale, and the addresses from 8X02 to FXF respectively store the gamma correction values corresponding to the gray scales of the G data from the second starting gray scale to the second ending gray scale. When the gray scale of the R data received by determination circuit  110  is in the first predetermined range, the determination circuit  110  determines that the R data require gamma correction. When the gray scale of the G data received by determination circuit  110  is in the second predetermined range, the determination circuit  110  determines that the G data require gamma correction. 
         [0021]    The second LUT  140  stores gamma correction values corresponding to all gray scales of the B data. That is, all the B data require gamma correction using the gamma correction values stored in the second LUT  140 . 
         [0022]    The control circuit  120  receives the R, G, B data, and the first and second address signals and the first and second output signals output by the determination circuit  110 . The control circuit  120  searches for the gamma correction values corresponding to the R data or the G data requiring gamma correction in the first LUT  130  according to the first or second address signals, controls the first LUT  130  to output the gamma correction values corresponding to the R data or the G data requiring gamma correction to the processing circuit  150 , and also outputs the R data or the G data requiring gamma correction to the processing circuit  150 . In an alternative embodiment, the control circuit  120  can directly obtain the gamma correction values corresponding to the R data or the G data requiring gamma correction by searching in the first LUT  130  according to the first or second address signals and outputting the gamma correction values corresponding to the R data or the G data requiring gamma correction and the R data or the G data requiring gamma correction to the processing circuit  150 . The control circuit  120  outputs the R data or the G data not requiring gamma correction according to the first or the second output signals to the output circuit  160 . The control circuit  120  searches for the gamma correction values corresponding to the B data in the second LUT  140 , directs the second LUT  140  to output the gamma correction values to the processing circuit  150 , and also outputs the B data to the processing circuit  150 . In an alternative embodiment, the control circuit  120  can directly obtain the gamma correction values corresponding to the B data by searching in the second LUT  140  and outputs the correction values and the B data to the processing circuit  150 . The control circuit  120  includes a first control unit  122 , a second control unit  124 , and a third control unit  126  respectively corresponding to the R, G, B data. The first control unit  122  receives the R data, searches for the gamma correction value corresponding to the R data requiring gamma correction in the first LUT  130  according to the first address signal received from the first address generating circuit  114  of the determination circuit  110  and outputs the R data requiring gamma correction, or outputs the R data not requiring gamma correction according to the first output signal. The second control unit  124  receives the G data, searches for the gamma correction value corresponding to the G data requiring gamma correction in the first LUT  130  according to the second address signal received from the second address generating circuit  118  of the determination circuit  110  and outputs the G data requiring gamma correction, or outputs the G data not requiring gamma correction according to the second output signal. The third control unit  126  receives the B data, searches for the gamma correction value corresponding to the B data in the second LUT  140 , and outputs the B data. 
         [0023]    The processing circuit  150  receives the R, G data requiring gamma correction and the gamma correction values corresponding to the R, G data, and the B data and the gamma correction value corresponding to the B data, generates adjusted R, G, B data, and outputs the adjusted R, G, B data to the output circuit  160 . The processing circuit  150  includes a first adder unit  152 , a second adder unit  154 , and a third adder unit  156 . The first adder unit  152  adds the corresponding gamma correction value to the R data, and generates an adjusted R data. The second adder unit  154  adds the corresponding gamma correction value to the G data, and generates an adjusted G data. The third adder unit  156  adds the corresponding gamma correction value to the B data, and generates an adjusted B data. 
         [0024]    The output circuit  160  outputs the adjusted R, G, B data and the R data or the G data not requiring gamma correction. The output circuit  160  includes a first output unit  162 , a second output unit  164 , and a third output unit  166 . The first output unit  162  outputs the adjusted R data or the R data not requiring gamma correction, the second output unit  164  outputs the adjusted G data or the G data not requiring gamma correction, and the third output unit  166  outputs the adjusted B data. 
         [0025]    Referring to  FIG. 3 , a flowchart of a method for processing R data of an image signal by the gamma adjustment circuit  100  is shown, as follows. 
         [0026]    In step S 11  a first starting gray scale and a first ending gray scale of R data from the first LUT  130  are obtained. When the first comparison circuit  112  of the determination circuit  110  and the first control unit  122  of the control circuit  120  receive original R data of the image signal received by the gamma adjustment circuit  100 , the first comparison circuit  112  reads the first starting gray scale and the first ending gray scale in the first predetermined range of the R data from the first LUT  130 . For example, the first starting gray scale may be set to 80 gray scale and be stored at the address 0X00, and the first ending gray scale may be set to 205 gray scale and be stored at the address 0X01. 
         [0027]    In step S 12 , the first comparison circuit  112  determines whether a gray scale of the original R data is in the first predetermined range which is from the first starting gray scale to the first ending gray scale. If so, step S 13  is implemented. If not, step S 17  is implemented. 
         [0028]    In detail, the first comparison circuit  112  determines whether the gray scale of the original R data is in the first predetermined range. When the gray scale of the original R data is between the first staring gray scale and the first ending gray scale, the original R data requires adjustment. Thus, the first comparison circuit  112  outputs the gray scale of the original R data and the first starting gray scale to the first address generating circuit  114 . When the gray scale of the original R data is less than the first staring gray scale and more than the first ending gray scale, the original R data requires not be adjusted. Thus, the first comparison circuit  112  outputs a first output signal to the first control unit  122 , and the first control unit  122  outputs the original R data not being adjusted to the first output unit  162 . 
         [0029]    In step S 13 , a first address signal corresponding to the original R data in the first LUT  130  is obtained according to the original R data, the first starting gray scale, and a storage order of gamma correction values corresponding to the R data stored in the first LUT  130 . When the addresses from 0X02 to 7XF successively store the gamma correction values corresponding to the gray scales of the R data between the first starting gray scale and the first ending gray scale, the first address generating circuit  114  generates the first address signal corresponding to the original R data by subtracting the first starting gray scale from the gray scale of the original R data and adding 1. For example, if the first starting gray scale and the first ending gray scale respectively equal 100 and 225, when the gray scale of the original R data is 120, because of the equation 120−100+1=21, the first address signal corresponding to the original R data is obtained to be 21. 
         [0030]    In step S 14 , gamma correction value corresponding to the original R data is searched for from the first LUT  130  according to the first address signal. That is, the first address signal corresponding to the original R data is provided to the first control unit  122 , and the first control unit  122  searches for the gamma correction value corresponding to the original R data from the first LUT  130  according to the first address signal. For example, if the first address signal corresponding to the original R data is 21 and the storage order of the first LUT  130  starts from 0, the 22 nd  address 1X05 obtained by counting from the address 0X00 simply stores the gamma correction value corresponding to the original R data. 
         [0031]    In step S 15 , obtaining adjusted R data is obtained by adding the gamma correction value to the original R data. The first control unit  122  outputs the gray scale of the original R data to the first adder unit  152 . The first adder unit  152  receives the gray scale of the original R data and the gamma correction value corresponding to the original R data, adds the gamma correction value to the gray scale of the original R data to obtain the adjusted R data, and outputs the adjusted R data to the first output unit  162 . 
         [0032]    In step S 16 , the adjusted R data is output. The first output unit  162  receives and outputs the adjusted R from the first adder unit  152 . 
         [0033]    In step S 17 , the original R data is output. The first output unit  162  receives and outputs the original R data not being adjusted from the first control unit  122 . 
         [0034]    Referring to  FIG. 4 , a flowchart of a method for processing G data of an image signal by the gamma adjustment circuit  100  is shown. The method is similar to the method for processing the R data, as follows. 
         [0035]    In step S 21 , a second starting gray scale and a second ending gray scale of the second predetermined range of G data from the first LUT  130  are obtained. When the second comparison circuit  116  of the determination circuit  110  and the second control unit  124  of the control circuit  120  receive an original G data of the image signal received by the gamma adjustment circuit  100 , the second comparison circuit  116  reads the second starting gray scale and the second ending gray scale of the second predetermined range of the G data from the first LUT  130 . For example, the second starting gray scale may be stored at the address 8X00, and the second ending gray scale may be stored at the address 8X01. 
         [0036]    In step S 22 , the second comparison circuit  116  determines whether a gray scale of the original G data is in the second predetermined range which is from the second starting gray scale to the second ending gray scale. If so, step S 23  is implemented. If not, step S 27  is implemented. 
         [0037]    In detail, the second comparison circuit  116  determines whether the gray scale of the original G data is in the second predetermined range. When the gray scale of the original G data is between the second staring gray scale and the second ending gray scale, the original G data requires adjustment. Thus, the second comparison circuit  116  outputs the gray scale of the original G data and the second starting gray scale to the second address generating circuit  118 . When the gray scale of the original G data is less than the second staring gray scale and more than the second ending gray scale, the original G data requires no adjustment. Thus, the second comparison circuit  116  outputs a second output signal to the second control unit  124 , and the second control unit  124  outputs the original G data not being adjusted to the second output unit  164 . 
         [0038]    In step S 23 , a second address signal corresponding to the original G data in the first LUT  130  is obtained according to the original G data, the second starting gray scale, and a storage order of gamma correction values corresponding to the G data stored in the first LUT  130 . When the addresses from 8X02 to FXF successively store the gamma correction values corresponding to the gray scales of the G data between the second starting gray scale and the second ending gray scale, the second address generating circuit  118  generates the second address signal corresponding to the original G data by subtracting the second starting gray scale from the gray scale of the original G data and adding 129. For example, if the second starting gray scale and the second ending gray scale respectively equal 100 and 225, when the gray scale of the original G data is 120, because of the equation 120−100+129=149, the second address signal corresponding to the original G data is obtained to be 149. 
         [0039]    In step S 24 , gamma correction value corresponding to the original G data is searched for from the first LUT  130  according to the second address signal. That is, the second address signal corresponding to the original G data is provided to the second control unit  124 , and the second control unit  124  searches for the gamma correction value corresponding to the original G data from the first LUT  130  according to the second address signal. For example, if the second address signal corresponding to the original R data is 149, the 150 th  address 9X05 obtained by counting from the address 0X00 just stores the gamma correction value corresponding to the original G data. 
         [0040]    In step S 25 , adjusted G data is obtained by adding the gamma correction value to the original G data. The second control unit  124  outputs the gray scale of the original G data to the second adder unit  154 . The second adder unit  154  receives the gray scale of the original G data and the gamma correction value corresponding to the original G data, adds the gamma correction value to the gray scale of the original G data to obtain the adjusted G data, and outputs the adjusted G data to the second output unit  164 . 
         [0041]    In step S 26 , the adjusted G data is output. The second output unit  164  receives and outputs the adjusted G from the second adder unit  154 . 
         [0042]    In step S 27 , the original G data is output. The second output unit  164  receives and outputs the original G data not being adjusted from the second control unit  124 . 
         [0043]    Referring to  FIG. 1  again, a method for processing B data of an image signal by the gamma adjustment circuit  100  includes: providing an original B data to the third control unit  126 , obtaining a gamma correction value corresponding to the original B data from the second LUT  140  by the third control unit  126  according to gray scale of the original B data, providing the gamma correction value corresponding to the original B data and the gray scale of the original B data to the third adder unit  156 , obtaining adjusted B data by adding the gamma correction value to the gray scale of the original B data via the third adder unit  156 , providing the adjusted B data to the third output unit  166 , and outputting the adjusted B data by the third output unit  166 . 
         [0044]    It should be noted that the original R, G, B data received by the gamma adjustment circuit  100  is usually 8-bit data. However, 10-bit data output by the gamma adjustment circuit  100  may be required in actual application. Thus, the control circuit  120  is required to transform the 8-bit data to the 10-bit data, and outputs the 10-bit data. The control circuit  120  can transform the 8-bit data to the 10-bit data by left shifting the 8-bit data by 2 bits. For example, 8-bit data of the gray scale of the original R data of 11111111, after being processed by the first control unit  122  becomes 10-bit data of 1111111100. Similarly, the second control unit  124  can also transform 8-bit data of gray scale of the original G data to 10-bit data, and provide the 10-bit data to the second adder unit  154  or the second output unit  164 . The third control unit  126  can also transform 8-bit data of gray scale of the original B data to 10-bit data, and provide the 10-bit data to the third adder unit  156 . 
         [0045]    The gamma adjustment circuit  100  employs the first LUT  130  to merely store gamma correction values corresponding to part gray scales of the R, G data, employs the determination circuit  110  to determine whether the gray scales of the original R, G data require adjustment, and employs the control circuit  120  to search for gamma correction values corresponding to the original R, G data requiring adjustment in the first LUT  130  and directly outputting the original R, G data not being adjusted. Thus, the gamma adjustment circuit  100  merely requires a first LUT  130  for processing the R, G data, and saves storage space. 
         [0046]    Referring to  FIG. 5 , a schematic circuit block diagram of another embodiment of a gamma adjustment circuit is shown. The gamma adjustment circuit  200  is similar to the gamma adjustment circuit  100 , however, the gamma adjustment circuit  200  merely includes one LUT  230 , and further includes a third comparison circuit  215  and a third address generating circuit  217 . The LUT  230  stores gamma correction values corresponding to part gray scales of the R, G, B data. A method for processing B data of an image signal by the gamma adjustment circuit  200  is similar to that processing the R, G data by the gamma adjustment circuit  100 . The method for processing the B data by the gamma adjustment circuit  200  is as follows. 
         [0047]    A third starting gray scale and a third ending gray scale of a third predetermined range of B data from the LUT  230  are obtained. 
         [0048]    The third comparison circuit  215  determines whether gray scale of an original B data is in the third predetermined range. If so, the subsequent step is implemented. If not, outputting the original B data. 
         [0049]    An address signal corresponding to the original B data in the LUT  230  is obtained according to the original B data, the third starting gray scale, and a storage order of gamma correction values corresponding to the B data stored in the LUT  230 . 
         [0050]    A gamma correction value corresponding to the original B data is searches for from the LUT  230  according to the address signal. 
         [0051]    Adjusted B data is obtained by adding the gamma correction value to the original B data. 
         [0052]    The adjusted B data is output. 
         [0053]    Referring to  FIG. 6 , a schematic circuit block diagram of one embodiment of a display device is shown. The display device  10  includes a gamma adjustment circuit  40 , a data driving circuit  30 , and a display panel  20 . The gamma adjustment circuit  40  receives R, G, B data of an image signal, processes the R, G, B data to obtain adjusted R, G, B data, and provides the adjusted R, G, B data to the data driving circuit  30 . The data driving circuit  30  generates display driving signals according to the adjusted R, G, B data, and provides the display driving signals to the display panel  20 . The display panel  20  displays the image according to the display driving signals. The display panel  20  may be a liquid crystal display panel. The gamma adjustment circuit  40  can be the gamma adjustment circuit  100  or the gamma adjustment circuit  200 . Thus, the display device  10  can accordingly conserve storage space. 
         [0054]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the embodiments or sacrificing all of their material advantages.