Gradation voltage setting method for multi-level display device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a dot matrix type display method and a voltage setting method of a drive circuit that performs multicolor / multigradation display related to a display device.

【0002】

[Conventional technology]

The conventional liquid crystal display device converts the input interface signal into a drive signal for driving the liquid crystal display device, and gives the drive signal to the liquid crystal drive means. In the liquid crystal drive means, eight levels of the given drive signal are used. The image is displayed by capturing the display data for each line of the screen and outputting it to the liquid crystal panel as an 8-level liquid crystal drive power supply according to the display data. In this method, 8 gradations were displayed by evenly dividing the above 8 levels of voltage as described in the 1991 IEICE Spring National Convention Lecture Paper C-480.

【0003】

However, in this method, the voltage level is divided evenly, and whether or not the gradation balance looks even to the human eye is not considered.

【0004】

The above-mentioned prior art will be described in detail with reference to FIGS. 2 to 8.

【0005】

FIG. 2 is a block diagram showing a conventional liquid crystal display device, where 1 is Red input display data, 2 is Green input display data, 3 is Blue input display data, and 4 is a clock. , Input display data 1 to 3 are sent serially in synchronization with clock 4 for each one pixel, and each of Red input display data 1, Green input display data 2, and Blue input display data 3 is one pixel. The data is composed of 3 bits for minutes and represents 8 gradations. Here, the pixel means one lighting element of each of Red, Green, and Blue, and in the case of a color display device, one dot is composed of three pixels. Details will be described later. 5 is the horizontal clock, 6 is the head signal, and data for one horizontal is sent in one cycle (one horizontal period) of the horizontal clock 5. Further, the head signal 6 indicates the head line of the display data, and the display data for one screen is sent in one cycle. 7 is a liquid crystal drive signal generator, 8 is a liquid crystal display data, 9 is a data clock, 10 is a liquid crystal horizontal clock, 11 is a liquid crystal head signal, and the liquid crystal signal generator 7 displays input display data 1 to 3 on the liquid crystal display. For this purpose, R pixels, G pixels, and B pixels are rearranged in this order, and 8-pixel parallel data is generated for 3-bit liquid crystal display data 8 in which the data for one pixel represents 8 gradations. Further, the clock 4, the horizontal clock 5, and the head signal 6 are input, and the data clock 9, the liquid crystal horizontal clock 10, and the liquid crystal head signal 11 are generated, respectively. 21 is an 8-level uniform liquid crystal applied voltage generator, 22 is an 8-level uniform liquid crystal applied voltage, and the 8-level uniform liquid crystal applied voltage generator 21 generates an evenly divided voltage, and the 8-level uniform liquid crystal applied voltage is generated. Output as 22. 14 is an 8-level data driver represented by Hitachi HD66310, 15 is liquid crystal horizontal data, and the 8-level data driver 14 captures the liquid crystal display data 8 by one horizontal with the data clock 9 and then uses the liquid crystal horizontal clock 10. Synchronously, the captured data is captured in the output stage, and according to the data, one level is selected from the 8-level liquid crystal applied voltage 21 as the liquid crystal horizontal data 15. Output. Therefore, the 8-level data driver 14 outputs the data as the liquid crystal horizontal data 15 one line before the liquid crystal display data 8 of the line captured by the data clock 9. The liquid crystal display data 8 is data that matches the input specifications of the 8-level data driver 14. The input of the Hitachi HD66310 consists of 3 bits of data for one pixel and 4 pixels in parallel, but here the input of the 8-level data driver 14 consists of 3 bits of data for one pixel. It will be described below assuming that 8 pixels are in parallel. 16 is the scan driver, and 17, 18, and 19 are the outputs of the scan driver 16, which are the first line scan line, the second line scan line, and the nth line scan line, respectively, and the liquid crystal horizontal data output by the 8-level data driver 14. The selected voltage is output to the scanning line of the line displaying 15. Reference numeral 20 denotes a liquid crystal panel, which has a resolution of horizontal m dots and vertical n lines, and displays eight gradations according to the voltage of the liquid crystal horizontal data 15.

【0006】

FIG. 3 is a timing diagram of each signal related to the operation in which the liquid crystal drive signal generation unit 7 generates the liquid crystal display data 8 from the input display data 1 to 3 in FIG. (a) is Red input display data 1, (b) is Green input display data 2, and (c) is Blue input display data 3. Each is a signal sent serially for one pixel, and one pixel is. It is 3-bit data representing 8 gradations. (d) to (f) are signals obtained by converting input display data 1 to 3 serially sent one pixel at a time from (a) to (c) into parallel for eight pixels, and (g) is a liquid crystal display. Data 8 is parallel data for 8 pixels in which Red, Green, and Blue data are rearranged according to the pixel arrangement of the liquid crystal panel 20.

【0007】

FIG. 4 shows the pixel configuration of the liquid crystal panel 20. 23 is a Red pixel, 24 is a Green pixel, and 25 is a Blue pixel, and these three pixels form one dot 26. The liquid crystal display data 8 will be generated according to this pixel arrangement.

【0008】

FIG. 5 shows the configuration of the 8-level uniform liquid crystal applied voltage generation unit 21. 27 is a liquid crystal drive power supply, 28 to 36 are resistors for dividing the liquid crystal drive power supply into 8 levels of voltage, 37 to 44 are operational amplifiers, and by making all the resistance values of 29 to 35 equal, 8 levels are equal. Generates a liquid crystal applied voltage 22. The voltage values at that time are shown in Table 1.

【0009】

[table 1]

<img file="JP2000200075A_D0001.tif" />【0010】

FIG. 6 is a block diagram showing details of the 8-level data driver 14. Reference numeral 45 is a data shift unit, and 46 is shift data. The data shift unit 45 takes in data for one line during one horizontal period according to the data clock 9, and outputs it as shift data 46. 47 is the 1-line latch means, 48 is the display data, and the 1-line latch means 47 latches the shift data 46 for one line and outputs it as the display data 48 in synchronization with the liquid crystal horizontal clock 10. Reference numeral 49 denotes an 8-level voltage selection unit, which selects one level of the 8-level liquid crystal applied voltage 22 according to the display data 48 and outputs it as liquid crystal horizontal data 15 (X-D1 to X-D3m). X-D1 to X-D3m indicate that the resolution of the liquid crystal panel 20 is horizontal m dots and one dot is composed of 3 pixels, so the horizontal lines of the liquid crystal horizontal data are (3 x m) lines. There is.

【0011】

FIG. 7 is a diagram showing the configuration of the 8-level voltage selection unit. 50 is a 3to8 decoder, 51 to 58 are decoder output lines, 59 to 66 are switching elements, and 67 is a liquid crystal horizontal data line, which is one of the liquid crystal horizontal data (X-D1 to X-D3m). The 3to8 decoder 50 sets one of the decoder output lines 51 to 58 as '1' according to the 3-bit display data 48, thereby setting one of the switching elements 59 to 66 as'on' and equalizes 8 levels. One level of the liquid crystal applied voltage 22 is selected and output to the liquid crystal horizontal data line 67.

【0012】

FIG. 8 is a diagram showing an example of the relationship between the applied voltage of the liquid crystal and the display brightness. It shows the display brightness with the liquid crystal applied voltages V1 to V8 in which 8 levels are evenly divided.

【0013】

FIGS. 2-8 will be referred to again to illustrate the operation of the present invention. In FIG. 2, the liquid crystal drive signal generation unit 7 is sent serially for one pixel each, and one pixel is 3 bits and represents 8 gradations. Red input display data 1, Green input display data 2, and Blue input display data. 3. In parallel with 8 pixels synchronized with the data clock 9 for liquid crystal display from clock 4, 3-bit liquid crystal display data 8 is generated for 1 pixel, and the liquid crystal drive signal is generated from the horizontal clock 5 and the start signal 6. The data clock 9, the liquid crystal horizontal clock 10, and the liquid crystal head signal 11 are generated. The generation of the liquid crystal display data 8 will be described in detail later.

【0014】

The 8-level uniform liquid crystal applied voltage generation unit 21 generates an 8-level liquid crystal applied voltage 22 having an even voltage difference. Details will be described later.

【0015】

The 8-level data driver 14 generates liquid crystal horizontal data 15 from liquid crystal display data 8, data clock 9, liquid crystal horizontal data 10, and 8-level uniform liquid crystal applied voltage 22. Details will be described later. The scanning driver 16 captures the liquid crystal head signal 11 '1' with the liquid crystal horizontal clock 10, outputs the selected voltage to the first line scanning line 17, and then uses the liquid crystal horizontal clock 10 to output the line line scanning lines 18, ... n. The line is sequentially shifted to the scanning line 19, and one screen is scanned. The voltage of the liquid crystal horizontal data 15 output from the 8-level data driver 14 is displayed on the line of the liquid crystal panel 20 to which the selected voltage is output from the scanning driver 16.

【0016】

The details of the operation related to the generation of the display data of the liquid crystal drive signal generation unit 7 will be described with reference to FIGS. 2 to 4.

【0017】

In FIG. 2, the liquid crystal drive signal generation unit 7 converts the data as shown in FIG. 3 because the input data of the 8-level data driver 14 is an 8-dot parallel input. The input display data 1 to 3 of (a) to (c) are serial-parallel converted to obtain parallel data for 8 pixels of each color of (d) to (f). This is rearranged in the order of Red, Green, and Blue according to the pixel arrangement of the liquid crystal panel 20 as shown in FIG. 4, and is output as parallel liquid crystal display data 8 for 8 pixels.

【0018】

The details of the operation of the 8-level uniform liquid crystal applied voltage generation unit 12 will be described with reference to FIGS. 5 and 1.

【0019】

In FIG. 5, the resistors 28 to 36 divide the liquid crystal drive power supply 27 and output through the operational amplifiers 37 to 44. Since the resistance values of the resistors 29 to 35 are all equal, V1 to V8 are output as shown in Table 1 as an 8-level uniform liquid crystal applied voltage 22 having a uniform voltage difference.

【0020】

The details of the operation of the 8-level data driver 14 will be described with reference to FIGS. 6 and 7.

【0021】

In FIG. 6, the data shift unit 45 takes in the liquid crystal display data 8 for one line in one horizontal period according to the data clock 9, and outputs it as shift data 46. The 1-line latching means 47 latches the shift data 46 for one line according to the horizontal clock 10, and outputs the shift data 46 as display data 44 in synchronization with the liquid crystal horizontal clock 10. The 8-level voltage selection unit 49 selects one level of the 8-level uniform liquid crystal applied voltage 22 according to the display data 48, and outputs it as liquid crystal horizontal data 15 (X-D1 to X-D3m).

【0022】

The details of the operation of the 8-level voltage selection unit 49 will be described with reference to FIG.

【0023】

In FIG. 7, the 3to8 decoder 50 sets one of the decoder output lines 51 to 58 to '1' according to the 3-bit display data 48, thereby turning one of the switching elements 59 to 66'on'. Then, one level of the 8-level uniform liquid crystal applied voltage 22 is output to the liquid crystal horizontal data line 67 through the switching element turned on.

【0024】

The operation of color display will be described with reference to FIGS. 4 and 8.

【0025】

Figure 8 shows an example of the luminance characteristics of 8 gradations displayed at the 8-level uniform liquid crystal applied voltage 22. In FIG. 2, since each of the Red pixel 23, the Green pixel 24, and the Blue pixel 26 has the luminance characteristics as shown in FIG. 8, the one dot 27 composed of these three pixels is displayed in 512 colors by 512 combinations. Is done.

【0026】

[Problems to be Solved by the Invention]

In the above-mentioned conventional example, since the voltage applied to the 8-level liquid crystal is evenly divided, the balance of gradations visible to the human eye is not considered.

【0027】

An object of the present invention is to provide a gradation voltage setting method for a multi-gradation display device in which a human visual characteristic is added to the optical characteristics of a display and the gradation balance is seen evenly by the human eye. Is.

【0028】

[Means for solving problems]

The above object can be realized by providing a means for generating an 8-level liquid crystal applied voltage so as to equalize the color difference of the gradation display.

【0029】

[Action]

When the 8-level liquid crystal applied voltage generating means performs 8-gradation display, the color difference from the adjacent gradation becomes equal, so that the gradation display in which the balance looks even to the human eye can be realized.

【0030】

[Example]

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1, 9 to 14 and Table 2. FIG. 1 is a block diagram of an embodiment of a multi-gradation display device to which the present invention is applied, where 1 is Red input display data, 2 is Green input display data, 3 is Blue input display data, and 4 is a clock. In this embodiment, each of the input display data 1 to 3 is synchronized with the clock 4, the data for each pixel is sent serially, and the data for one pixel is data representing 8 gradations with 3 bits. 7 is a liquid crystal drive signal generator, 8 is a liquid crystal display data, 9 is a data clock, 10 is a liquid crystal horizontal clock, and 11 is a liquid crystal head signal. A data clock 9, a liquid crystal horizontal clock 10, and a liquid crystal head signal 11 are generated. Reference numeral 12 is an 8-level liquid crystal applied voltage generator, 13 is an 8-level liquid crystal applied voltage, and the 8-level liquid crystal applied voltage generator 12 generates an 8-level liquid crystal applied voltage 13 in consideration of human visual characteristics. 14 is an 8-level data driver, 15 is liquid crystal horizontal data, and the 8-level data driver 14 generates liquid crystal horizontal data 15 as in the conventional case. 16 is the scan driver, and 17, 18, and 19 are the outputs of the scan driver 16, which are the first line scan line, the second line scan line, and the nth line scan line, respectively. The scan driver 16 has 8 levels as before. The selected voltage is output to the scanning line of the line displaying the liquid crystal horizontal data 15 output by the data driver 14. 20 is a liquid crystal panel.

【0031】

FIG. 9 shows an example of the internal configuration of the 8-level liquid crystal applied voltage generation unit 12. 27 is a liquid crystal drive power supply, 68 to 83 are resistors, 84 to 91 are operational amplifiers, resistors 68 and 69, 70 and 71, 72 and 73, 74 and 75, 76 and 77, 78 and 79, 80 and 81, 82. And 83 divide the liquid crystal drive power supply 27, respectively, and output them as V1 to V8 of the 8-level liquid crystal applied voltage 13 through the operational amplifiers 84 to 91. In this embodiment, V1&gt; V2&gt; ...&gt; V7&gt; V8, gradation 1 (black display) by V1, gradation 8 (white display) by V8, and gradation 2 to 7 (white display) by other V2 to V7. Halftone) will be obtained.

【0032】

FIG. 10 shows an example of setting the voltage applied to the 8-level liquid crystal. The settings of V1 to V8 are not even.

【0033】

FIG. 11 shows the characteristics of the 8-gradation luminance obtained by the liquid crystal panel used in this embodiment when the 8-level liquid crystal applied voltage 13 is not set evenly as shown in FIG.

【0034】

FIG. 12 is a CIELUV uniform color space, and the distance between the coordinates in this color space represents the difference in color visible to the human eye. 92 is the coordinates of the black display by V1 of the 8-level liquid crystal applied voltage 13, 93 is the coordinates of the white display by V8, and 94 is the trajectory of the coordinates when the 8-level liquid crystal applied voltage is changed from V1 to V8.

【0035】

FIG. 13 is a diagram showing the color difference between each gradation in the 8-gradation display of the liquid crystal panel used in this embodiment, and 99 is obtained when the 8-level uniform liquid crystal application voltage 22 is set to the setting of Table 1. The color difference between each gradation of gradation, 100 is the color difference between each gradation obtained by setting the brightness between 8 gradations evenly as shown in Fig. 11, 101 is the setting of 8 level liquid crystal applied voltage 13 in Table 2. The color difference between each of the eight gradations obtained in this case is shown.

【0036】

FIG. 14 is a diagram showing the display luminance obtained when the 8-level liquid crystal applied voltage 13 is set to the setting shown in Table 2.

【0037】

FIG. 15 is a diagram showing the display luminance characteristics of the eight gradations of this embodiment.

【0038】

Hereinafter, FIGS. 1, 9 to 15 and Table 2 will be used again to explain the operation of this embodiment.

【0039】

In FIG. 1, the liquid crystal drive signal generation unit 7 displays the liquid crystal display synchronized with the data clock 9 for the liquid crystal display from the red input display data 1, the green input display data 2, the blue input display data 3, and the clock 4 as in the conventional case. Data 8 is generated, and the data clock 9, the liquid crystal horizontal clock 10, and the liquid crystal head signal 11 which are the liquid crystal driving signals are generated from the horizontal clock 5 and the head signal 6.

【0040】

The 8-level liquid crystal applied voltage generation unit 12 generates an 8-level liquid crystal applied voltage 13 in which the voltage difference is arbitrarily set. Details will be described later.

【0041】

The 8-level data driver 14 generates the liquid crystal horizontal data 15 from the liquid crystal display data 8, the data clock 9, the liquid crystal horizontal data 10, and the 8-level uniform liquid crystal applied voltage 13 as in the conventional case. The scanning driver 16 captures the liquid crystal head signal 9 '1' with the liquid crystal horizontal clock 10, outputs the selected voltage to the first line scanning line 17, and then uses the liquid crystal horizontal clock 10 to output the second line scanning line 18, ... The nth line is sequentially shifted to the scanning line 19, and one screen is scanned. On the line of the liquid crystal panel 20 to which the selected voltage is output from the scanning driver 16, the display is performed according to the voltage of the liquid crystal horizontal data 15 output from the 8-level data driver 14. The operation of color display is the same as the conventional one, and 512 colors are displayed by combining 8 gradations.

【0042】

The details of the setting method of the 8-level liquid crystal applied voltage 13 according to the human visual characteristics will be described with reference to FIGS. 9 to 15.

【0043】

In FIG. 9, the liquid crystal drive power supply 27 is arbitrarily divided by resistors 68 and 69, 70 and 71, 72 and 73, 74 and 75, 76 and 77, 78 and 79, 80 and 81, 82 and 83. Through operational amplifiers 84 to 91, the voltage applied to the 8-level liquid crystal becomes V1 to V8.

【0044】

The display luminance when V1 to V8 are set unevenly is shown in FIG. 10, and the display luminance characteristic of 8 gradations is as shown in FIG. In this case, the logarithm of the display brightness is set to be even.

【0045】

Figure 12 shows the CIELUV uniform color space defined by the CIE of the International Commission on Illumination, and the distance between the coordinates in this space represents the difference in color visible to the human eye. Of the 8-level liquid crystal applied voltage 13, the coordinates * shown in the black display coordinates 92 by V1 and the white display coordinates 93 by V8 are the coordinates obtained by optical measurement (Y, u ́, v ́). It is shown that a psychological element is added to, and the coordinate locus when the 8-level liquid crystal applied voltage is changed from V1 to V8 is 94. Further, since these coordinates differ depending on the characteristics of the liquid crystal panel, they are the coordinates obtained by performing optical measurement after setting the voltage. The optical measurement method in this embodiment is shown below.

【0046】

The optical measuring instrument used in this example is 1980B manufactured by PHOTO RESEARCH. By measuring the light on the surface of the liquid crystal panel with SPECTRARADIOMETER MODE in the measurement mode of 1980B manufactured by PHOTO RESEARCH, it is possible to obtain (Y) representing brightness and coordinates (u ́, v ́) representing color. The measurement range is within a circle with a diameter of about 5 mm at the center of the liquid crystal panel. The coordinates (Y, u ́, v ́) obtained by optical measurement for any voltage setting can be replaced with the coordinates in the CIELUV uniform color space by calculating according to Equation 1.

【0047】

[Number 1]

<img file="JP2000200075A_D0002.tif" />【0048】

The distance between the coordinates in this CIELUV uniform color space is the color difference that is visible to the human eye, which is called the color difference. The calculation method of the color difference between the black display by the 8-level liquid crystal applied voltage V1 and the white display by V8 in FIG. 12 is as shown in Equation 2.

【0049】

[Number 2]

<img file="JP2000200075A_D0003.tif" />【0050】

However, this distance is a straight line distance and is different from the distance of the locus 94 in FIG. Therefore, the distance between adjacent applied voltages and the distance of the locus 94 can be calculated by gradually changing the applied voltage between V1 and V8, calculating the color difference between the respective voltages, and accumulating them. In the present invention, in order to equalize the color difference between the gradations of 8 gradations, this locus 94 is divided into (number of gradations-1), that is, 7 divisions in the case of 8-gradation display, and the color difference between each gradation is , Find a set of applied voltages that almost matches the value obtained by the division. Optical measurement is performed for each gradation display after the voltage is set, and the color difference between each gradation is calculated using Equation 2. In this case, if the obtained color difference is different from the required color difference, the voltage setting, the optical measurement, and the color difference calculation are performed again, and this is repeated until the required color difference is obtained. The results obtained in this way are shown in Table 2.

【0051】

[Table 2]

<img file="JP2000200075A_D0004.tif" />【0052】

The color difference value in the table represents the color difference from the gradation in the upper column, for example, the color difference value in the gradation 3 column represents the color difference from the gradation 2. As shown in Table 2, by setting the 8-level liquid crystal applied voltage 13 so that the color difference between each gradation is even, the gradation to the human eye regardless of the characteristics of the liquid crystal panel such as the liquid crystal material and the color filter. It is possible to realize an 8-gradation display in which the differences between the two are evenly visible.

【0053】

FIG. 13 compares the color difference between each gradation in the 8-gradation display of the liquid crystal panel used in this embodiment, and when the voltage is equalized as shown in Table 1, the brightness is equalized as shown in FIG. When the voltage is set so as to be, Table 2 shows the case where the voltage is set so that the color difference is even.

【0054】

When the 8-level liquid crystal applied voltage 13 is set to the setting shown in Table 2, the 8-gradation display luminance obtained by the liquid crystal panel used in this embodiment is as shown in FIG. 14, so the 8-gradation display luminance characteristic is shown in FIG. become that way. Therefore, in the case of the liquid crystal panel used in this embodiment, by setting the 8-level liquid crystal applied voltage so as to obtain the 8-gradation display luminance characteristic as shown in FIG. 15 without measuring the color difference, a human being can use the liquid crystal panel. It is possible to realize an 8-gradation display in which the difference between gradations can be seen evenly by the eyes. In addition, even if the characteristics of the liquid crystal material such as the liquid crystal material or the color filter change, by setting the 8-level liquid crystal applied voltage 13 so that the color difference between each gradation is even, regardless of the characteristics of the liquid crystal panel. It is possible to obtain an 8-gradation display that looks even to the human eye.

【0055】

Further, an example in which the number of gradations is increased from 8 gradations to 16 gradations by the FRC (frame rate control) method will be described with reference to FIGS. 16 and 17 and Tables 3 and 4.

【0056】

FRC is a method of obtaining a gradation between the two gradations by alternately switching two gradation displays for a certain pixel for each frame (single screen scanning period).

【0057】

FIG. 16 is a block diagram of an embodiment of a liquid crystal multi-gradation display device to which this embodiment is applied. 95 is the Red input display data, 96 is the Green input display data, 97 is the Blue input display data, and 4 is the clock. In this embodiment, the input display data 95 to 97 are sent in synchronization with the clock 4. Bit data. 98 is the liquid crystal drive signal generator for gradation control, 8 is the liquid crystal display data, 9 is the data clock, 10 is the liquid crystal horizontal clock, 11 is the liquid crystal head signal, and the liquid crystal drive signal generator 95 for gradation control is 4 bits. The input display data 95 to 97 of the above are converted into 3-bit liquid crystal display data, and the data clock 9, the liquid crystal horizontal clock 10, and the liquid crystal head signal 11 are generated as in the conventional case. The 8-level liquid crystal applied voltage generation unit 12 generates the 8-level liquid crystal applied voltage 13 for the FRC method. Details of the method of converting the 4-bit input display data 95 to 97 to the 3-bit liquid crystal display data 8 and the method of setting the 8-level liquid crystal applied voltage will be described later. The 8-level data driver 14, the scanning driver 16, and the liquid crystal panel 20 are the same as the 8-gradation display.

【0058】

FIG. 17 is a diagram showing the display luminance characteristics of the 16-gradation display according to this embodiment.

【0059】

In order to explain the details of the operation of this embodiment, FIGS. 16 and 17 will be used again.

【0060】

In FIG. 16, the liquid crystal drive signal generation unit 98 is a 3-bit sequenced 4-bit serial Red input display data 95, Green input display data 96, Blue input display data 97, and clock 4 synchronized with data clock 9 for liquid crystal display. Generates the liquid crystal display data 8 of. An example of conversion from 4 bits to 3 bits is shown in Table 3.

【0061】

[Table 3]

<img file="JP2000200075A_D0005.tif" />【0062】

The gradation in which two types of 3-bit data are shown is the gradation in which the FRC method is performed, and the liquid crystal display data generation unit 98 for gradation control switches between these two types of data for each frame.

【0063】

Further, as in the case of the 8-gradation display, the data clock 9, the liquid crystal horizontal clock 10, and the liquid crystal head signal 11 which are the liquid crystal driving signals are generated from the horizontal clock 5 and the head signal 6.

【0064】

The 8-level liquid crystal applied voltage generation unit 12 generates an 8-level liquid crystal applied voltage 13 in which the voltage difference is arbitrarily set. The voltage is set so as to show the same luminance characteristics as in the case of 8-gradation display. Table 3 shows the voltage value in that case and the color difference between each gradation. As shown in Table 3, the color difference has an error of ± about 50% with respect to the average of 7.1, and there is a limit to the adjustment because the FRC method is used, but there is no problem in visual evaluation. The 16-gradation display luminance characteristic of FIG. 17 shows the same characteristics as the 8-gradation display luminance characteristic when a liquid crystal panel having the same characteristics is used.

【0065】

The reason why the color difference error in this embodiment is large is that in the FRC method, when the voltage value of the gradation (for example, gradation 3) that does not depend on FRC is changed, the adjacent FRC gradation (gradations 2 and 4) is changed. This is because it is difficult to equalize the color difference because the voltage value of) also changes.

【0066】

The 8-level data driver 14 generates the liquid crystal horizontal data 15 from the liquid crystal display data 8, the data clock 9, the liquid crystal horizontal data 10, and the 8-level uniform liquid crystal applied voltage 13 as in the conventional case. The scanning driver 16 captures the liquid crystal head signal 9 '1' with the liquid crystal horizontal clock 10, outputs the selected voltage to the first line scanning line 17, and then uses the liquid crystal horizontal clock 10 to output the second line scanning line 18, ... The nth line is sequentially shifted to the scanning line 19, and one screen is scanned. The liquid crystal horizontal data 15 output from the 8-level data driver 14 is displayed on the line where the selected voltage is output from the scanning driver 16 of the liquid crystal panel 20.

【0067】

Further, in FIG. 16, the 8-level liquid crystal applied voltage generation unit is provided independently for each of Red, Green, and Blue, and the liquid crystal drive signal generation unit 98 for gradation control also converts data from 4 bits to 3 bits in Red, Green, and By performing each of Blue independently, it is possible to obtain 16 gradations that are evenly visible to the human eye for each color.

【0068】

Table 4 shows another example of the combination of the voltage setting and the FRC method for obtaining the 16-gradation display having the luminance characteristics as shown in FIG. Even if the combination is changed, if the color difference between the gradations is equal, it is possible to obtain a 16-gradation display in which the difference between the gradations looks even to the human eye. Further, in the case of the liquid crystal panel used in this embodiment, the difference between gradations is evenly distributed to the human eye by matching the 16-gradation display luminance characteristic as shown in FIG. 17 without measuring the color difference. A visible 16-gradation display can be obtained.

【0069】

[Table 4]

<img file="JP2000200075A_D0006.tif" />【0070】

Further, even when the number of gradations is increased, if the color difference between the gradations is equal, it is possible to obtain a multi-gradation display in which the difference between the gradations looks even to the human eye, which is used in this embodiment. By matching the display luminance characteristics with the curve as shown in FIG. 17, it is possible to obtain a gradation display in which the difference between gradations can be seen evenly by the human eye. In addition, even if the characteristics of the liquid crystal material such as the liquid crystal material or the color filter change, by equalizing the color difference between each gradation, the difference between the gradations is equal to the human eye regardless of the characteristics of the liquid crystal panel. It is possible to obtain a gradation display that looks like.

【0071】

[Effect of the invention]

According to the present invention, by equalizing the color difference between adjacent gradations in the gradation display, the difference between gradations is equal to the human eye regardless of the characteristics of the liquid crystal panel such as the liquid crystal material and the color filter. It is possible to realize a multi-gradation display that looks like.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram of an Example of an 8-gradation display device using the present invention.

[Figure 2]

It is a block diagram of a conventional 8-gradation display device.

[Fig. 3]

It is an operation timing diagram of the liquid crystal drive signal generation part shown in FIG.

[Fig. 4]

It is a pixel block diagram of the liquid crystal panel shown in FIG.

[Fig. 5]

It is an internal block diagram of the 8-level uniform liquid crystal applied voltage generation part shown in FIG.

[Fig. 6]

It is a block diagram of the 8-level data driver shown in FIG.

[Fig. 7]

It is an internal block diagram of the 8-level voltage selection part shown in FIG.

[Fig. 8]

It is a figure which shows an example of the relationship between the liquid crystal applied voltage and the display luminance.

[Fig. 9]

It is an internal block diagram of the 8-level liquid crystal applied voltage generation part shown in FIG.

[Fig. 10]

It is a figure which shows an example of setting of an 8-level liquid crystal applied voltage.

[Fig. 11]

It is a figure which shows the characteristic of 8 gradation display luminance obtained by the voltage setting of FIG.

[Fig. 12]

It is a figure which shows the coordinates of white display and black display in CIELUV uniform color space.

[Fig. 13]

It is a figure which shows the color difference between each gradation of 8 gradations obtained by the voltage setting shown in Table 1, FIG. 10, and Table 2.

[Fig. 14]

It is a figure which shows the display luminance when the voltage is set so that a color difference becomes uniform.

[Fig. 15]

It is a figure which shows the characteristic of 8 gradation display luminance obtained by the voltage setting of FIG.

[Fig. 16]

It is a block diagram of an Example of a 16-gradation display device using the present invention.

[Fig. 17]

It is a figure which shows the display luminance characteristic of the 16-gradation display by this invention.

[Explanation of symbols]

1 ... 3-bit Red input display data, 2 ... 3-bit Green input display data, 3 ... 3 bit Blue input display data, 4 ... clock, 5 ... horizontal clock, 6 ... leading signal, 7 ... LCD drive signal generator, 8 ... LCD display data, 9 ... data clock, 10 ... LCD horizontal clock, 11 ... LCD top signal, 12 ... 8 level liquid crystal applied voltage generator, 13 ... 8 level LCD applied voltage, 14 ... 8 level data driver, 15 ... LCD horizontal data, 16 ... scanning driver, 17 ... 1st line scanning line, 18 ... 2nd scan line, 19 ... nth scan line, 20 ... LCD panel, 21 ... 8 level uniform liquid crystal applied voltage generator, 22 ... 8 level uniform liquid crystal applied voltage, 23 ... Red pixel, 24 ... Green pixels, 25 ... Blue pixels, 27 ... LCD drive power supply, 45 ... Data shift section, 46 ... shift data, 47 ... 1 line latch means, 48 ... Display data, 49 ... 8 level voltage selector, 50 ... 3to8 decoder, 67 ... LCD horizontal data line, 95 ... 4-bit Red input display data, 96 ... 4-bit Green input display data, 97 ... 4-bit Blue input display data, 98 ... LCD drive signal generator for gradation control.