JP2662307B2 - Simple matrix drive type color liquid crystal display - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a simple matrix drive type color liquid crystal display device.

[Prior Art] In a liquid crystal panel of a simple matrix drive system, a group of signal electrodes extending in a vertical direction and a group of scanning electrodes extending in a horizontal direction are arranged in a matrix. Become.

A voltage is applied to each scanning electrode one line at a time, and display data for one line is simultaneously applied to each signal electrode as a signal voltage. Therefore, a voltage corresponding to the potential difference between the intersecting signal electrode and the scanning electrode is applied to each pixel.

Now, paying attention to a certain pixel, when the scanning electrode is active, a signal voltage to be displayed is applied to the signal electrode. However, even when the scanning electrode is inactive, the signal electrode is common, so that another pixel is displayed. A signal voltage is applied.

Therefore, it is affected by data of pixels belonging to the same column on another line. This is called crosstalk and is a major factor in lowering the contrast.

Conventionally, a voltage averaging method or the like is known as a method for reducing crosstalk. The voltage averaging method is a method for averaging the voltages applied to the non-selected pixels to reduce the variation in the applied voltage between the pixels.

[Problems to be Solved by the Invention] However, in this voltage averaging method, when the number of scanning electrodes increases, a decrease in contrast cannot be avoided, and it is difficult to achieve a sufficient effect.

Therefore, an object of the present invention is to reduce crosstalk without lowering contrast.

[Means for Solving the Problems] According to the present invention, first calculation means for adding input display dot data of each color of red, green and blue for each column, and output from the first calculation means. First storage means for storing the addition data of each color for one line,
A second calculating means for converting the final addition data of each color sequentially read out from the storage means into brightness correction data of each color in consideration of a visual brightness difference of each color, and each color outputted from the second calculating means. A second storage means for storing the luminance correction data for one line, a third arithmetic means for adding the luminance correction data of each color sequentially read from the second storage means to the display dot data and outputting the same, Control means for controlling the operation of each calculation means and the storage means based on the displayed display timing signal, and an image based on the display dot data of each color to which the luminance correction data output by the third calculation means is added. It is to reproduce.

Further, the present invention provides a fourth arithmetic means for converting the input display dot data of each color of red, green and blue into luminance data in consideration of a visual luminance difference of each color, and an output from the fourth arithmetic means. Calculating means for adding the luminance data to be added for each column, first storing means for storing one line of added data output from the first calculating means, and sequentially reading out from the first storing means. Second arithmetic means for converting the final addition data to be converted into brightness correction data, second storage means for storing one line of the brightness correction data output from the second calculation means, and sequentially from the second storage means. Third calculating means for adding the read luminance correction data to the display dot data of each color and outputting the same, and control means for controlling the operation of each calculating means and storage means based on the input display timing signal. Be prepared And performs image reproduction according to the third colors of the display dot data obtained by adding the luminance correction data outputted from the arithmetic means.

[Operation] Crosstalk is caused by the application of an extra voltage because the signal electrode is shared between pixels in the same column. This crosstalk becomes more pronounced when the amount of extra voltage differs greatly between adjacent columns.

For example, all of the pixel groups in both adjacent columns are white (display is on)
If half of the pixel groups in the column between them is white (display on) and the other half is black (display off), the extra voltage applied to the pixel displaying half white is Is smaller than the extra voltage applied to the pixel displaying white, so that it becomes darker than white on both sides.

In the above configuration, the input display dot data is added for each column, luminance correction data in each column is obtained based on the final added data, and the luminance correction data is added to the input display dot data.

That is, the gray level of white (display ON) is increased for each column according to the sum of the extra voltages applied to each column.

Therefore, the brightness difference due to the extra voltage is corrected without lowering the contrast, and the crosstalk is reduced.

[Embodiment] First, a simple matrix drive type monochrome liquid crystal display device as shown in FIG. 7 will be described.

In FIG. 1, reference numeral 1 denotes a display system including a video memory. The display dot data DATA and the display timing signal STM output from the display system 1 are supplied to the crosstalk mitigation circuit 2.

This crosstalk reducing circuit 2 is configured as shown in FIG.

In the figure, a display timing signal STM is
Supplied to The control unit 21 controls the operation of each calculation unit and storage unit described later.

The calculating means 22 and the storage means 23 constitute a circuit for calculating the sum of the display dot data of each column.

In this case, the calculating means 22 is constituted by an adder. In the calculating means 22, the input display dot data DATA and the storage means are stored.
The data read from 23 are added.

The storage means 23 has a buffer memory for one line. At the same time as the display timing, the addition data of each column is sequentially read and supplied to the arithmetic means 22,
New addition data supplied from the calculating means 22 is stored again.

This operation is repeated for all the lines during the display period, and finally, the storage means 23 stores the total sum (final addition data) of the display dot data of each column.

The total sum of the display dot data of each column stored in the storage means 23 is supplied to the storage means 25 through the arithmetic means 24 during the flyback period. At the same time, the contents of the storage means 23 are cleared.

The calculation means 24 is constituted by a conversion circuit for converting the sum of the display dot data of each column into brightness correction data. In this case, the conversion is performed such that the larger the sum of the display dot data, the smaller the luminance correction data. The correction level may be optimized in advance or may be set arbitrarily.

The storage means 25 has a buffer memory for one line. The storage unit 25 stores the luminance correction data of each column converted by the calculation unit 24.

The brightness correction data of each column stored in the storage means 25 is displayed simultaneously with the display dot data DA at the start of the display period.
The data is read out in synchronization with the TA and supplied to the calculating means 26. The calculation means 26 is supplied with the display dot data DATA.

The calculating means 26 is constituted by an adder, and the luminance correction data is added to the display dot data DATA only when the display dot data DATA is the display ON data.

Returning to FIG. 7, the display dot data DATA 'to which the luminance correction data has been added by the arithmetic means 26 is supplied to an LCD (liquid crystal display) controller 3 as display data. The LCD controller 3 is supplied with a display timing signal STM from the display system 1.

As a result, a monochrome image based on the display dot data DATA 'is reproduced on a liquid crystal panel (not shown) of the simple matrix drive system.

In the example of FIG. 7, the display dot data DATA is added for each column, and the larger the total sum of the display dot data DATA in each column is, the smaller the brightness correction data is formed. This brightness correction data is added to the display dot data DATA. Is done. And
On the liquid crystal panel, a monochrome image is reproduced by the display dot data DATA 'to which the luminance correction data has been added. That is,
In the example of FIG. 7, the white gradation is increased and displayed for each column according to the sum of the extra voltages applied to each column of the liquid crystal panel. The difference in the brightness of the columns can be corrected, and the crosstalk can be reduced.

Next, an embodiment of the present invention will be described with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 7 are denoted by the same reference numerals.

In the figure, red output from the display system 1
The green and blue display dot data DR, DG, DB and the display timing signal STM are supplied to the crosstalk mitigation circuit 200, respectively.

The crosstalk reduction circuit 200 is one of the color liquid crystal panels.
The configuration is different depending on the arrangement of the red (R), green (G), and blue (B) filters constituting the pixel.

As shown in FIG. 2A, when pixels are composed of pixels arranged in the horizontal direction and the arrangement of the RGB filters is a vertical stripe arrangement, it is necessary to calculate an extra voltage in pixel units. It is configured as shown in FIG.

Further, as shown in FIG. 2B, when pixels are arranged in the vertical direction and pixels are formed, and when the arrangement of the RGB filters is a horizontal stripe arrangement, it is necessary to calculate an extra voltage in pixel units. It is configured as shown in FIG.

First, the crosstalk reduction circuit 200 of FIG. 3 will be described. In FIG. 3, parts corresponding to those in FIG. 8 are indicated by the same reference numerals, or R and B.

In the figure, the display dot data DR, DG, DB for each color
Are supplied to the signal processing circuits 201R, 201G, and 201B, respectively. Although detailed description is omitted, the arithmetic means 22R to the arithmetic means 26R of the signal processing circuit 201R and the arithmetic means 22G of the signal processing circuit 201G
The operation of the arithmetic means 26G and the arithmetic means 22B to 26B of the signal processing circuit 201B are controlled by the control means 21, and operate in the same manner as the arithmetic means 22 to 26 in the example of FIG. Therefore, the display dot data DR ′, DG ′ of red, green and blue to which the luminance correction data is added
DB 'is output.

In the calculation means 24R, 24G, 24B, red,
The final addition data for each column for green and blue colors is converted to luminance correction data, but is converted to luminance correction data in consideration of the visual luminance difference between each color.

Display dot data DR ', D of each color to which the luminance correction data output from the signal processing circuits 201R, 201G, 201B are added.
G 'and DB' are supplied to arithmetic means 28R, 28G and 28B, respectively.

A control signal SC for controlling whether or not to perform inverse gamma correction is supplied from the display system 1 (not shown in FIG. 3) to each of these arithmetic means 28R, 28G, and 28B.

By the way, since the emission characteristics of the CRT become as shown by the broken line a in FIG. 5A, so-called gamma correction may be performed on the video signal with the characteristics shown by the solid line b in FIG. The above-described inverse gamma correction is a process of correcting display dot data with the characteristics of the solid line c in FIG. 5B to cancel gamma correction.

The calculation means 28R is configured, for example, as shown in FIG.

In the figure, display dot data DR ′ output from a signal processing circuit 201R is supplied to a selector 282 via a table 281.
Of the selector 282 and directly to the B side of the selector 282. The table 281 is configured with RAM, ROM, etc.
The display dot data DR 'is supplied as address data, and the data DR "subjected to inverse gamma correction is read.

Selection by the selector 282 is controlled based on the control signal SC. For example, when the control signal SC indicates that the inverse gamma correction is to be performed, the inverse gamma corrected display dot data DR ″ input to the A side is selected and output, while the control signal SC performs the inverse gamma correction. If not, display dot data DR 'which is not reverse gamma-corrected and input to the B side is selected and output.

Although the description is omitted, the calculation means 28G and 28B are also configured in the same manner as the calculation means 28R described above.

Next, the crosstalk mitigation circuit 200 of FIG. 4 will be described. In FIG. 4, parts corresponding to those in FIGS. 8 and 3 are denoted by the same reference numerals or further denoted by RB.

In the figure, the display dot data DR, DG, DB for each color
Is supplied to the calculating means 27 and converted into luminance data.
The conversion into the luminance data is performed, for example, as follows in consideration of the visual luminance difference between the colors.

Luminance data = 0.30R + 0.59G + 0.11B The luminance data output from the calculating means 27 is supplied to the signal processing circuit 202. Although the description is omitted, the operation of the signal processing circuit 202 is controlled by the control means 21 and operates in the same manner as the calculation means 22 to 25 in the example of FIG.
Therefore, the storage unit 25 stores the luminance correction data of each column converted by the calculation unit 24.

Then, the luminance correction data of each column stored in the storage means 25 is read out in synchronization with the display dot data DR, DG, DB at the same time as the display period starts, and is read out by the arithmetic means 26R, 2R.
Supplied to 6G, 26B.

The calculation means 26R, 26G, and 26B are supplied with the display dot data DR, DG, and DB of each color, respectively. These calculation means 26
The operations of R, 26G, and 26B are controlled by control means 21,
The operation is similar to that of the calculating means 26 in the example of FIG. Therefore, the display dot data DR 'and DG'DB' to which the luminance correction data has been added are output from the calculating means 26R, 26G and 26B.

Then, the display dot data DR ', DG', DB 'of each color output from the calculating means 26R, 26G, 26B are supplied to the calculating means 28R, 28G, 28B, respectively.

These calculating means 28R, 28G and 28B are configured as described in the example of FIG.
R ', DG', DB ', or display dot data DR ", DG", DB "further subjected to inverse gamma correction are output.

Returning to FIG. 1, red, green, and blue display dot data DR ', DG', and DB 'output from the crosstalk reduction circuit 200.
Alternatively, DR ″, DG ″, and DB ″ are supplied as display data to the LCD controller 3. The LCD controller 3
Is supplied with a display timing signal STM from the display system 1.

Accordingly, the color liquid crystal panel of the simple matrix drive system can display the display dot data DR ', DG', DB 'or
A color image by DR ", DG", DB "is reproduced.

As described above, also in this example, the brightness is increased for each column in accordance with the sum of the extra voltages applied to each column of the liquid crystal panel, and the display is performed. Obtainable.

Further, according to this example, the display dot data DR ″, DG ″, and DB ″ that have been inversely gamma-corrected by the control signal SC can be output from the crosstalk mitigation circuit 200. Therefore, the display dot data DR, DG , DB is gamma-corrected data, image reproducibility can be further improved by inverse gamma correction.

Note that, although not described above, the black-and-white liquid crystal display device of FIG. 7 can also include an arithmetic unit for performing inverse gamma correction.

[Effects of the Invention] As described above, according to the present invention, the white gradation is increased for each column according to the sum of the extra voltages applied to each column of the liquid crystal panel. The difference in brightness of each column due to the extra voltage to be applied can be corrected, and crosstalk can be reduced. Even if the number of scanning electrodes increases, the contrast does not decrease unlike the voltage averaging method, which is very useful.

In addition, by selectively providing the function of inverse gamma correction, it is possible to improve image reproducibility when display dot data (video signal) is gamma-corrected data.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing an example of an arrangement of RGB filters in a color liquid crystal panel, FIGS. 3 and 4 are configuration diagrams of a crosstalk reduction circuit, and FIGS. FIG. 6 is an explanatory diagram of the inverse gamma correction, FIG. 6 is a configuration diagram of an arithmetic unit for performing the inverse gamma correction, FIG. 7 is a configuration diagram of a monochrome liquid crystal display device, and FIG. is there. DESCRIPTION OF SYMBOLS 1 ... Display system including video memory 2,200 ... Crosstalk mitigation circuit 3 ... Liquid crystal display controller 21 ... Control means 22,22R-22B, 24,24R-24B, 26,26R-26B, 28R-28B ... …
Arithmetic means 23, 23R to 23B, 25, 25R to 25B ... Storage means 201R to 201B, 202 ... Signal processing circuit

Claims (3)

(57) [Claims] A first calculating means for adding the input display dot data of each color of red, green and blue for each column, and adding data of each color outputted from the first calculating means to each of the columns. A first storage unit for storing one line, and a second storage unit for converting the final addition data of each color sequentially read from the first storage unit into luminance correction data of each color in consideration of a visual luminance difference of each color. Calculation means; second storage means for storing one line of the luminance correction data of each color output from the second calculation means; and luminance correction data of each color sequentially read from the second storage means. A third calculating means for adding to and outputting the display dot data, and a control means for controlling the operation of each of the calculating means and the storing means based on the input display timing signal; The third color liquid crystal display device of simple matrix drive method which performs image reproduction by adding the colors of the display dot data in the luminance correction data outputted by the operation means. 2. A fourth arithmetic means for converting the input display dot data of each color of red, green and blue into luminance data in consideration of a visual luminance difference of each color; First calculating means for adding the output luminance data for each column; first storing means for storing one line of added data output from the first calculating means; and first storing means A second calculating means for converting the final added data sequentially read from the second calculating means into brightness correction data;
Second storage means for storing lines, third calculation means for adding luminance correction data sequentially read from the second storage means to the display dot data of each color, and outputting the same, and input display timing And control means for controlling the operation of each of the arithmetic means and the storage means based on the signal. The image reproduction by the display dot data of each color to which the luminance correction data output from the third arithmetic means is added. A simple matrix drive type color liquid crystal display device. 3. A simple matrix drive type color liquid crystal display device according to claim 1, wherein a means for performing inverse gamma correction on the display dot data of each color is provided at a subsequent stage of said third arithmetic means.