Abstract:
A timing control circuit provides at least a driver control signal and a display data signal to a driver circuit of a display panel such that a predetermined image is displayed on the display panel, dispensing with an external source providing the signals, thereby an EMI measurement of a display apparatus can be performed without influences from an external source and a cable that connects the external source to the display apparatus to be examined.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a timing control circuit, an image display apparatus, and an evaluation method of the image display apparatus, and especially relates to a timing control circuit, an image display apparatus and an evaluation method of the image display apparatus, evaluation of which is performed by displaying a predetermined image on a display panel. 
     2. Description of the Related Art 
     Conventionally, an EMI (Electromagnetic Interference) evaluation of an image display apparatus, such as an LCD (Liquid Crystal Display), has been performed by a system as shown in FIG.  1 . 
       FIG. 1  shows a block diagram of an example of a system that performs EMI evaluation of an LCD. As for the system of  FIG. 1 , an LCD  1  and a personal computer (henceforth PC)  2  are connected through a cable  3 . 
     Here, the PC  2  transmits a signal (for example, a clock signal, a display enable signal, and a display-data signal) to a timing controller  10  of the LCD  1  through the cable  3  such that the LCD  1  displays a predetermined image for EMI evaluation. 
     The timing controller  10  generates a gate driver control signal (for example, a gate clock signal, and a gate start signal) that controls a gate driver  11 , using the signal received from the PC  2 , and transmits the gate driver control signal to the gate driver  11 . Further, the timing controller  10  generates a source driver control signal (for example, a dot clock signal, an output-control signal, a polarity signal, a display data signal, a data start signal) that controls a source driver  12 , using the signal received from the PC  2 , and transmits the source driver control signal to the source driver  12 . 
     The gate driver  11  and the source driver  12  display the predetermined image for EMI evaluation on a liquid crystal panel  13  according to the gate driver control signal and the source driver control signal, respectively. Here, in the liquid crystal panel  13 , pixels are provided in a matrix form, each pixel including a TFT (Thin Film Transistor)  17  that is connected to a liquid crystal capacitor  18 , a data (source) bus line  15 , and a gate bus line  16 . 
     That is, the LCD  1  receives a signal required in order to display the predetermined image for EMI evaluation from the PC  2 , and displays the predetermined image for EMI evaluation on the liquid crystal panel  13  according to the received signal. 
     As described above, the EMI evaluation of the LCD  1  is performed while the predetermined image for EMI evaluation is displayed on the liquid crystal panel  13 . That is, the LCD  1  has to keep receiving a signal required in order to display the predetermined image for EMI evaluation from the PC  2  during the EMI evaluation. 
     Therefore, in the system of  FIG. 1 , a problem is that the PC  2  and the cable  3  are indispensable in addition to the LCD  1 , which makes it difficult to identify which of the LCD  1 , the PC  2 , and the cable  3  is generating and radiating an EMI. Consequently, in the system of  FIG. 1 , it is difficult to measure an EMI of the LCD  1  itself. 
     The present invention is made in view of the above-mentioned point, and aims at offering a timing control circuit, an image display apparatus, and an evaluation method of the image display apparatus that realize evaluation of the image display apparatus by displaying a predetermined image on a display panel, eliminating influences of the PC  2  and the cable  3 . 
     SUMMARY OF THE INVENTION 
     It is a general object of the present invention to provide an apparatus and a method that substantially obviate one or more of the problems caused by the limitations and disadvantages of the related art. 
     Features and advantages of the present invention will be set forth in the description that follows, and in part will become apparent from the description and the accompanying drawings, or may be learned by practice of the invention according to the teachings provided in the description. Objects as well as other features and advantages of the present invention will be realized and attained by a circuit, an apparatus and a method particularly pointed out in the specification in such full, clear, concise, and exact terms as to enable a person having ordinary skill in the art to practice the invention. 
     To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the present invention provides at least a timing control circuit that generates a display data signal and a driver control signal such that a predetermined test image is generated without needing the display data and the driver control signals to be supplied from an external source. Here, the display data signal and the driver control signal can be generated using a clock signal generated in an image display apparatus. Accordingly, the present invention realizes evaluation of an image display apparatus by displaying a predetermined image on a display panel, which is not influenced by an external component, such as the PC  2  and the cable  3 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an example of a system that performs EMI evaluation of an LCD; 
         FIG. 2  is a block diagram of an LCD of an embodiment of the present invention; 
         FIG. 3  is an image figure of an example of an H-pattern; 
         FIG. 4  is a block diagram of a timing controller of an embodiment of the present invention; 
         FIG. 5  is a block diagram of an H-pattern horizontal cycle counter of an embodiment of the present invention; 
         FIG. 6  is a timing chart of an example of an H-pattern horizontal cycle counter; 
         FIG. 7  is a block diagram of an H-pattern vertical cycle counter of an embodiment of the present invention; 
         FIG. 8  is a timing chart of an example of the H-pattern vertical cycle counter; and 
         FIG. 9  is a block diagram of an H-pattern generating circuit of an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, embodiments of the present invention will be described with reference to the accompanying drawings. Although descriptions below explain embodiment examples of EMI evaluation of an LCD as an example of an image display apparatus, the present invention is applicable to other image display apparatuses such as a PDP (Plasma Display Panel) display apparatus, an EL (Electro Luminescence) display apparatus and so on. 
       FIG. 2  shows a block diagram of an LCD  1  of the embodiment of the present invention. The LCD  1  of  FIG. 2  includes a timing controller  10 , a gate driver  11 , a source driver  12 , a liquid crystal panel  13 , and an oscillator  14 . That is, the LCD  1  of  FIG. 2  does not require a signal (for example, a display enable signal, and a display data signal) from an external source in displaying a predetermined screen for EMI evaluation. 
     The oscillator  14 , such as a crystal oscillator, generates a clock signal CK, and supplies the generated clock signal CK to the timing controller  10 . The timing controller  10  generates a gate driver control signal (for example, a gate clock signal GCLK, and a gate start signal GST) that controls the gate driver  11 , using the supplied clock signal CK, and transmits the gate driver control signal to the gate driver  11 . 
     The timing controller  10  further generates a source driver control signal (for example, a dot clock signal DCK, an output-control signal LP, a polarity signal POL, a display data signal DXX, and a data start signal DST) that controls the source driver  12 , using the supplied clock signal CK, and transmits the source driver control signal to the source driver  12 . 
     That is, the timing controller  10  of  FIG. 2  generates the gate driver control signal, and the source driver control signal, using the clock signal CK. Details of process that generate the gate driver control signal and the source driver control signal using the clock signal CK are given later. 
     Further, the gate driver  11  and the source driver  12  display a predetermined image for EMI evaluation on the liquid crystal panel  13  according to the gate driver control signal and the source driver control signal. The predetermined image for EMI evaluation includes one or more H-patterns aligned horizontally and one or more the H-patterns aligned vertically. An example of an H-pattern is shown in FIG.  3 . 
     The H-pattern in this example occupies a dot matrix of 15×12, and uses a black dot as a background, and a white dot to represent an H-pattern. Here, row numbers  0 - 14  are given to horizontal lines from top to bottom, and column numbers  0 - 11  are given to vertical columns from left to right. 
     Hereafter, processing of the timing controller  10  is explained in detail.  FIG. 4  shows a block diagram of the timing controller  10  of the embodiment of the present invention. The timing controller  10  of  FIG. 4  includes input terminals  21  and  22 , output terminals  23 - 25 , an internal-timing start checking circuit  31 , a horizontal cycle counter  32 , a vertical cycle counter  33 , a control signal generating circuit  34 , an H-pattern horizontal cycle counter  35 , an H-pattern vertical cycle counter  36 , and an H-pattern generating circuit  37 . 
     The input terminal  21  is connected to the oscillator  14 . A clock signal CK is supplied to the internal-timing start checking circuit  31  from the input terminal  21 . In addition, the input terminal  22  may be connected to the PC  2  through the cable  3 , if necessary. When the PC  2  is connected to the input terminal  22  by the cable  3 , a display enable signal ENAB as a display-position control signal is supplied to the internal-timing start checking circuit  31  from the input terminal  22 . 
     The internal-timing start checking circuit  31  switches a timing mode between an external timing mode and an internal-timing mode, depending upon whether or not the display enable signal ENAB is supplied from the input terminal  22 . 
     Here, the external timing mode is the mode that displays an image on the liquid crystal panel  13  according to a signal (for example, a clock signal, a display enable signal, a display data signal) received from the PC  2 . Conversely, the internal-timing mode is the mode that displays an image on the liquid crystal panel  13  according to the signal (for example, the gate driver control signal, the source driver control signal) generated by the timing controller  10 . 
     For example, the internal-timing start checking circuit  31  counts the number of clock pulses while a level of the display enable signal ENAB supplied does not change, and when the counted number reaches a predetermined value, the mode is changed from the external timing mode to the internal-timing mode. In addition, if the level of display enable signal ENAB changes while operating under the internal-timing mode, the internal-timing start checking circuit  31  switches the mode from the internal-timing mode to the external timing mode. 
     When the internal-timing start checking circuit  31  switches the mode from the external timing mode to the internal-timing mode, a pulse that starts the internal-timing mode is supplied to the horizontal cycle counter  32 . 
     When the pulse that starts the internal-timing mode is received from the internal-timing start checking circuit  31 , the horizontal cycle counter  32  starts counting the clock pulses CK supplied from the input terminal  21 . The horizontal cycle counter  32  resets a counted number when the counted number reaches a predetermined value (for example, the number of clock pulses equivalent to one horizontal cycle), while supplying a one-clock-wide pulse to the vertical cycle counter  33 , the control signal generating circuit  34 , and the H-pattern vertical cycle counter  36 . 
     Further, the horizontal cycle counter  32  supplies a display-position start signal ITMSTART that indicates a display-position start (for example, left end of a display area) to the H-pattern horizontal cycle counter  35  and the H-pattern vertical cycle counter  36 . 
     The vertical cycle counter  33  counts the number of the one-clock-wide pulses supplied from the horizontal cycle counter  32 , resets the counted number, when the counted number reaches a predetermined value (for example, the number of the pulses equivalent to one vertical cycle), and supplies a one-clock-wide pulse to the control signal generating circuit  34 . The timing controller  10  generates a horizontal cycle and a vertical cycle by the horizontal cycle counter  32  and the vertical cycle counter  33 , respectively. 
     The control signal generating circuit  34  generates the gate driver control signal and the source driver control signal, using the one-clock-wide pulse supplied from the horizontal cycle counter  32 , and the one-clock-wide pulse supplied from the vertical cycle counter  33 , respectively. Further, the control signal generating circuit  34  outputs the source driver control signal from the output terminal  24 , while outputting the gate driver control signal from the output terminal  23 . 
     The H-pattern horizontal cycle counter  35  starts counting the number of the clock pulses CK supplied from the input terminal  21 , when the display-position start signal ITMSTART is supplied from the horizontal cycle counter  32 . 
     The H-pattern horizontal cycle counter  35  counts the number of clock pulses that corresponds to the horizontal cycle of the H-pattern (for example, 0-11 of the H-pattern of FIG.  3 ), and supplies the counted number to the H-pattern generating circuit  37 . In addition, the H-pattern horizontal cycle counter  35  resets the counted number, when the number of clocks equivalent to the horizontal cycle of the H-pattern is reached. 
     The H-pattern vertical cycle counter  36  counts the number of the one-clock-wide pulses supplied from the horizontal cycle counter  32 . The H-pattern vertical cycle counter  36  counts the number of the pulses that corresponds to the vertical cycle of the H-pattern (for example,  0 - 14  of the H-pattern of FIG.  3 ), and supplies the counted number to the H-pattern generating circuit  37 . In addition, the H-pattern vertical cycle counter  36  resets the counted number when the number of the pulses equivalent to the vertical cycle of the H-pattern is reached. 
     The H-pattern generating circuit  37  generates the display data according to the H-pattern using the counted number supplied from the H-pattern horizontal cycle counter  35 , and the counted number supplied from the H-pattern vertical cycle counter  36 . The H-pattern generating circuit  37  outputs the generated display data from the output terminal  25 . 
     In the case of the H-pattern of  FIG. 3 , for example, the H-pattern horizontal cycle counter  35  supplies the numbers of counts  0 - 11 , and the H-pattern vertical cycle counter  36  supplies the numbers of counts  0 - 14 , each to the H-pattern generating circuit  37 . 
     Here, the H-pattern of  FIG. 3  is configured by black lines (line numbers  0 ,  1 ,  13 , and  14 ) which consist of only black cells, black-and-white mixed lines (line numbers  2 - 6 ,  8 - 12 ) for vertical strokes of the character “H”, and a line (line number  7 ) for a horizontal stroke of the “H”. 
     The black lines are displayed by the H-pattern generating circuit  37  generating a display data signal of 12 consecutive black dots, and outputting from the output terminal  25 . In the case of the black-and-white mixed lines, the H-pattern generating circuit  37  generates “black, black, black, white, black, black, black, black, white, black, black and black” dots in this sequence and outputs from the output terminal  25 . In the case of displaying the horizontal stroke, the H-pattern generating circuit  37  generates three black dots, six white dots and three black dots in this order, and outputs from the output terminal  25 . 
     Selection of a black line, a black-and-white mixed line, and a line for the horizontal stroke can be performed by matching a counted number  0 - 14  supplied from the H-pattern vertical cycle counter  36 , and the line numbers  0 - 14 . Thus, it is possible to generate a display data signal representing the H-pattern by using a counter that is reset according to the horizontal and vertical cycle of the H-pattern. 
       FIG. 5  shows a block diagram of the H-pattern horizontal cycle counter  35  of the embodiment of the present invention. The H-pattern horizontal cycle counter  35  of  FIG. 5  includes NOT circuits  40  and  41 , AND circuits  42  and  43 , an OR circuit  44 , a JK-flip-flop circuit (henceforth a JK-FF circuit)  45 , and a counter circuit  46 . 
     Hereafter, processing of the H-pattern horizontal cycle counter  35  is explained, referring to a timing chart of  FIG. 6  that shows operational timing of an example of the H-pattern horizontal cycle counter  35 . 
     The display-position start signal ITMSTART such as shown by (B) in  FIG. 6  is supplied from the horizontal cycle counter  32  to the OR circuit  44 . In the present embodiment, the display-position start signal ITMSTART is active when at a high level, and expresses the display-position start. If the display-position start signal ITMSTART becomes high, the OR circuit  44  will supply the high-level signal to the terminal J of the JK-FF circuit  45 . 
     When the high-level signal is supplied to terminal J, the JK-FF circuit  45  supplies the high-level signal HLDN as shown by (c) of  FIG. 6  to a terminal LDN of the counter circuit  46 . When the high-level signal HLDN is supplied to the terminal LDN, the counter circuit  46  starts counting the clock signal CK as shown by (D) of  FIG. 6 , which is supplied from the input terminal  21 . 
     The counter circuit  46  outputs a counted number of clock pulses of the clock signal CK as shown by (A) of FIG.  6 (A) in a binary number from terminals QA-QD. For example, when the counted number is 11, the outputs are 1 from terminal QA, 1 from terminal QB, 0 from terminal QC and 1 from terminal QD. The counter circuit  46  supplies the output counted number to the H-pattern generating circuit  37 . 
     The AND circuit  43  supplies a high-level signal to a terminal K of the JK-FF circuit  45 , when the counted number output from the counter circuit  46  is 10.The JK-FF circuit  45  changes the level of the signal HLDN to low as shown by (C) of  FIG. 6 , which is supplied to the terminal LDN of the counter circuit  46 , when the high-level signal is supplied to the terminal K. The counter circuit  46  resets the counted number of the clock signal CK, when the signal HLDN indicating the low level is supplied to terminal LDN. 
     The AND circuit  42  supplies a high-level signal to the terminal J of the JK-FF circuit  45  through the OR circuit  44 , when the counted number output from the counter circuit  46  is 11. The JK-FF circuit  45  supplies the signal HLDN in the high level to the terminal LDN of the counter circuit  46 , when the high-level signal is supplied to the terminal J. The counter circuit  46  starts counting the number of clock pulses of the clock signal CK, when the high-level signal HLDN is supplied to terminal LDN. 
     Therefore, the H-pattern horizontal cycle counter  35  counts the number of clocks equivalent to the horizontal cycle of the H-pattern (for example, 0-11 in FIG.  5 ), and supplies the counted number to the H-pattern generating circuit  37 . 
       FIG. 7  shows a block diagram of an H-pattern vertical cycle counter  36  of the embodiment of the present invention. The H-pattern vertical cycle counter  36  of  FIG. 7  includes an AND circuit  50 , a JK-FF circuit  51 , and a counter circuit  52 . 
     Processing of the H-pattern vertical cycle counter  36  is explained, referring to the timing chart of  FIG. 8  that shows operational timing of an example of the H-pattern vertical cycle counter  36 . 
     The display-position start signal ITMSTART, as shown by (C) of  FIG. 8 , is supplied from the horizontal cycle counter  32  to a terminal J of the JK-FF circuit  51 . When a high-level signal is supplied to the J terminal, the JK-FF circuit  51  supplies a high-level signal VLDN, as shown by (D) of  FIG. 8 , to a terminal LDN of the counter circuit  52 . When the high-level signal VLDN is supplied to the terminal LDN, the counter circuit  52  starts counting the number of  1 HPLS pulses, shown by (B) of  FIG. 8 , supplied from the horizontal cycle counter  32  for every 1 horizontal cycle. 
     The counter circuit  52  counts the number of the  1 HPLS pulses, as shown by (A) of FIG.  8 (A), and outputs the number in a binary number from terminals QA, QB, QC and QD. For example, when the counted number is 7, 1 is output from the terminal QA, 1 is output from the terminal QB, 1 is output from the terminal QC, and 0 is output from the terminal QD. The counter circuit  52  supplies the output counted number to the H-pattern generating circuit  37 . 
     When the counted number output from the counter circuit  52  is 15, the AND circuit  50  supplies a high-level signal to the terminal K of the JK-FF circuit  51 . The JK-FF circuit  51  supplies the signal VLDN in a low level as shown by (D) of  FIG. 8  to the terminal LDN of the counter circuit  52 , if a high-level signal is supplied to the terminal K. The counter circuit  52  will reset the counted number of the  1 HPLS pulses, when the signal VLDN of a low level is supplied to the terminal LDN. 
     Accordingly, the H-pattern vertical cycle counter  36  counts the number equivalent to the vertical cycle of the H-pattern (for example, 0-15 in FIG.  5 ), and supplies the counted number to the H-pattern generating circuit  37 . 
       FIG. 9  shows a block diagram of an H-pattern generating circuit  37  of the embodiment of the present invention. The H-pattern generating circuit  37  of  FIG. 9  includes OR circuits  60 ,  65 ,  69 ,  74 , and  76 , and AND circuits  61 - 64 ,  66 - 68 ,  70 - 73  and  75 . 
     Incoming signals HPTH  1 - 4  of  FIG. 9  are the same as HPTH  1 - 4  signals output from the counter circuit  46  of  FIG. 5 , respectively. Incoming signals HPTV  1 - 4  are the same as signals HPTV  1 - 4  output from the counter circuit  52  of  FIG. 7 , respectively. Incoming signals XHPTV  1 - 4  and XHPTH  1 - 4  are reverse signals of the incoming signals HPTV  1 - 4  and HPTH  1 - 4 , respectively. Here, inverter circuits that generate the reverse signals are omitted. 
     The AND circuit  61  outputs a high-level signal to the OR circuit  65 , when the counted number output from the counter circuit  52  is one of  2  and  3 . The AND circuit  62  outputs a high-level signal to the OR circuit  65 , when the counted number output from the counter circuit  52  is one of  4 ,  5  and  6 . The AND circuit  63  outputs a high-level signal to the OR circuit  65 , when the counted number output from the counter circuit  52  is one of  8  through  11 . The AND circuit  64  outputs a high-level signal to the OR circuit  65 , when the counted number output from the counter circuit  52  is 12. 
     Accordingly, the OR circuit  65  outputs the signal VERLNV which becomes high-level to the AND circuit  70 , when the counted number output from the counter circuit  52  is one of  2  through  6 , and  8  through  12 . In other words, the signal VERLNV becomes high when the black-and-white mixed lines are processed. 
     On the other hand, the AND circuit  66  outputs to the AND circuit  75  a signal HORLNV that becomes high, when the counted number output from the counter circuit  52  is 7. In other words, the signal HORLNV becomes high when processing the line that includes the horizontal stroke of the character “H”. 
     The AND circuit  67  outputs a high-level signal to the OR circuit  69 , when the counted number output from the counter  46  is 3. The AND circuit  68  outputs a high-level signal to the OR circuit  69 , when the counted number output from the counter  46  is 8. Consequently, the OR circuit  69  outputs to the AND circuit  70  a signal that becomes high, when the counted number outputted from the counter circuit  46  is one of 3 and 8. 
     Accordingly, the AND circuit  70  outputs a signal that becomes high to the OR circuit  76 , when the counted number output from the counter circuit  52  is one of  2  through  6 , and  8  through  12 , and when the counted number output from the counter circuit  46  is one of  3  and  8 . In other words, the AND circuit  70  outputs to the OR circuit  76  a signal that becomes high when one of the line numbers  2  through  6  and  8  through  12  and one of the column numbers  3  and  8  of the H-pattern of  FIG. 3  are processed. 
     On the other hand, the AND circuit  71  outputs a high-level signal to the OR circuit  74 , when the counted number output from the counter  46  is 3. The AND circuit  72  outputs a high-level signal to the OR circuit  74 , when the counted number output from the counter circuit  46  is one of  4  through  7 . Further, the AND circuit  73  outputs a high-level signal to the OR circuit  74 , when the counted number output from the counter circuit  46  is 8. Consequently, the OR circuit  74  outputs to the AND circuit  75  a signal that becomes high, when the counted number outputted from the counter circuit  46  is one of  3  through  8 . 
     Accordingly, the AND circuit  75  outputs to the OR circuit  76  a signal that becomes high, when the counted numbers output from the counter circuit  52  is 7, and when the counted number output from the counter circuit  46  is one of 3 through 8. In other words, the AND circuit  75  outputs to OR circuit  76  a signal that becomes high when the line number  7 , and one of the column numbers  3  through  8  of the H-pattern of  FIG. 3  are processed. 
     As mentioned above, the OR circuit  76  can output display data corresponding to the H-pattern as shown in FIG.  3 . Although this embodiment is explained around an example of outputting display data of the H-pattern, it is possible to output display data corresponding to various patterns by changing the combination of the logical circuits of the H-pattern horizontal cycle counter  35 , the H-pattern vertical cycle counter  36 , and the H-pattern generating circuit  37 . 
     In the manner described above, a predetermined test image can be displayed without having to receive display data from an outside source via a cable, both of which are sources of disturbance when ascertaining an EMI level of a display apparatus to be examined. 
     Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No. 2001-251720 filed on Aug. 22, 2001 with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.