WO2006085508A1

WO2006085508A1 - Display gradation voltage setting method, display driving method, program, and display

Info

Publication number: WO2006085508A1
Application number: PCT/JP2006/302003
Authority: WO
Inventors: Tomoo Furukawa; Takashi Sasaki; Makoto Shiomi
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2005-02-09
Filing date: 2006-02-06
Publication date: 2006-08-17

Abstract

A display gradation voltage setting method comprises a step for determining the difference of gradation voltage for the gradation in a low gradation region, and a step for correcting the gradation voltage so that the gradation voltage of the maximum differential gradation corresponding to the maximum difference among the obtained differences becomes lower than the gradation voltage of zero gradation before correction. This prevents occurrence of a low gradation region where luminance varies discontinuously and occurrence of an edge (false outline) caused by color crosstalk.

Description

Specification

Display device gradation voltage setting method, display device drive method, program, and display device

Technical field

The present invention relates to a display device gradation voltage setting method, a display device driving method, a program, and a display device that have improved display performance.

Background art

[0002] Many defects have been pointed out regarding the color reproducibility of display devices, and for liquid crystal display devices, for example, the problem of crosstalk caused by adjacent pixels being coupled through a parasitic capacitance. Has been pointed out.

That is, if there is an insulating film between the transparent electrode and the source line, a parasitic capacitance is generated there. Similarly, parasitic capacitance is generated between the gate line and the transparent electrode and between the source line and the common electrode. The display pixel connected to the TFT (Thin Film Transistor) is applied with a desired voltage at the moment of gate high. Connected to the circuit. Since many of these peripheral electrical circuits are related to panel design, setting the drive voltage in consideration of the parasitic capacitance between the display pixel and the peripheral electrical circuit minimizes the effect. It is possible.

However, with regard to the source line, it is not possible to compensate in advance for crosstalk caused by other source lines. As shown in FIG. 11, in addition to the parasitic capacitance Csda with the source line A for driving the self-display pixel A, the parasitic capacitance Csdb is also generated with the source line B for driving the other display pixel B. appear. Due to this parasitic capacitance Csdb, the drive voltage that should be applied to the self-display pixel A changes. This is because the potential of the source line B that drives the other display pixels B cannot be defined in advance.

[0005] In order to eliminate such crosstalk, a technique for reducing parasitic capacitance has been proposed (see, for example, Patent Document 1: JP-A-5-203994 (published on August 13, 1993)). This is insufficient to achieve a sufficient reduction in crosstalk. For this reason, other source A dedicated drive algorithm is used to compensate in advance for crosstalk caused by noise.

[0006] When a predetermined pattern is displayed as shown in FIG. 12, an edge (false contour) force that cannot be resolved by the conventional driving algorithm is generated in the display image (display screen) of the display device. Problem may occur. Although such a problem does not occur originally, a display device designed to perform a specific voltage distribution in the ladder resistance of the driver newly introduces an area recognized as the edge. I found it. More specifically, a region in which the luminance change is discontinuous due to a change in the luminance of the display pixel due to a change in the voltage applied to the liquid crystal due to coupling with an adjacent pixel is recognized as the above edge. The problem arises. Here, “discontinuous” means that a change in liquid crystal applied voltage causes a change in one gradation, for example, a change in three gradations, and a change in one gradation is a continuous change. It is expressed as discontinuous.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a gradation voltage setting method and a program for a display device that can prevent the occurrence of an edge caused by coupling. It is to be realized.

Disclosure of the invention

[0008] The inventors of the present invention have intensively studied to solve the above problems, and as a result, the edge due to the discontinuous luminance change causes an intense driving voltage for driving the low gradation region of the display image. We found that it was caused by voltage fluctuation. More specifically, when a 256-gradation pattern shown in FIG. 12 is displayed, voltage fluctuations become severe in a low gradation region where the gradation is, for example, about 0 to 5, and an edge appears in the display image. Found out that it would occur. This is because when the gradation of B is 0 to 5 among the RGB pixels, the luminance change of the G pixel becomes discontinuous due to the coupling of B and G, and the luminance change is recognized as an edge. It is because of that. The inventors have found the above new knowledge about the cause of the occurrence of an edge in the display image, and have arrived at the present invention based on this new knowledge.

[0009] The reason why the above-described extreme U and voltage fluctuations occur in the low gradation region of the display device will be described below. In recent years, there has been a demand for smooth adjustment of the gradation luminance characteristics of display devices (displays) to the characteristics of γ = 2.2 in the low gradation area. In some cases, it is not possible to adjust the gradation luminance characteristic exactly to γ = 2.2. For this reason, an increasing number of models are using non-linear drivers, especially in display devices such as high-definition LCD TV modules for high definition.

[0010] That is, in a high-definition LCD TV module for high image quality, etc., the ladder resistance of the driver generates a grayscale voltage that causes extreme U and voltage fluctuations in the low grayscale region. V, a so-called non-linear driver, is designed to be used. As a result, the above-described drastic voltage fluctuation occurs in the low gradation region of the display device.

Therefore, in order to solve the above-described problem, the gradation voltage setting method for a display device according to the present invention applies a gradation voltage corresponding to each gradation to a display element to display an image. This is a voltage setting method in which the step of obtaining the difference in gradation voltage for the gradation in the low gradation region and the gradation voltage of the maximum difference gradation corresponding to the maximum difference among the obtained differences are corrected. And a step of correcting the gradation voltage corresponding to each gradation so as to be smaller than the gradation voltage of the 0 gradation.

[0012] With the above configuration, it is possible to prevent the generation of the edge due to the coupling between pixels as described above. In other words, by correcting the gradation voltage as described above, it is possible to prevent the occurrence of a large voltage change caused by coupling in the gradation area below the maximum difference gradation in the low gradation area. . In other words, after the above correction, the gray level below the maximum differential gray level is driven with the voltage value of the driving voltage having a higher gray level than the maximum differential gray level before the correction. The display is performed without using a combination of “gradation” and “gradation voltage” that occur. As a result, it is possible to prevent the occurrence of an edge in the display image of the display device by preventing the occurrence of a discontinuous luminance change that cannot be corrected by using the color crosstalk correction.

[0013] Note that the number of gradations (display gradations) in the low gradation region for obtaining the difference in gradation voltage may be set as appropriate according to the properties of the display device to be driven. Further, the method for obtaining the difference may be performed by a known method. For example, x (gradation) = 1 to 255 is calculated for every gradation according to the following formula.

AV (x) = V (x) -V (x- l) (x represents the gradation, Δ V (x) represents the difference in gradation voltage at gradation X, and V (x) represents the gradation voltage at gradation X.)

Further, the step of correcting the gradation voltage in the gradation voltage setting method of the display device may be performed by applying a gradation voltage corresponding to a gradation one larger than the maximum difference gradation to a gradation of 0 gradation before correction. The gradation voltage corresponding to each gradation may be corrected so as to obtain the regulated voltage. In the case of a display device in which the applied voltage is increased in the direction of low gradation, high force, and low, according to the above configuration, the gradation voltage of the maximum difference gradation is smaller than the gradation voltage of 0 gradation before correction. The gradation voltage can be corrected as follows.

The gradation setting method of the present invention is particularly preferably used when the display device is driven by a source driver having a ladder-resistive division in which a difference in gradation voltage has an extreme value. Can do. Here, a display device using a source driver (non-linear dry type) with ladder resistance division whose gradation voltage difference has an extreme value has an edge (false contour) that cannot be resolved by the conventional drive algorithm. May occur in the display image (display screen), but according to the gradation setting method of the present invention, the occurrence of the edge can be prevented.

[0015] The non-linear driver may be one in which the ladder resistance is combined so that the gradation luminance characteristic is γ = 2.2, for example. If the gradation resistance characteristic of the nonlinear driver is adjusted so that the gradation luminance characteristic is 7 = 2.2, severe voltage fluctuation occurs in the low gradation region, and the voltage difference has an extreme value. According to the gradation setting method of the present invention, it is possible to prevent an edge from being generated due to the intense voltage fluctuation. In addition, the low gradation area where an edge is generated due to severe voltage fluctuations varies depending on the power at which the reference voltage is input and how much γ is assumed as the gradation luminance characteristic. It is an area of 32 gradations or less.

[0016] A display device driving method according to the present invention is a display device driving method for displaying an image by applying a gradation voltage corresponding to each gradation to a display element. The gradation voltage of the display device is set (corrected) by the gradation voltage setting method of the present invention, and the display data below the maximum difference gradation is extracted for integers m and n where 6 ≤n <m. The method further includes the step of selecting low-gradation deletion data, converting the low-gradation deletion data to m bits, and then selecting a digital correction value corresponding to the m-bit data force n bits. It is characterized by.

[0017] With the above configuration, a predetermined gradation (2 ⁿ ) can be maintained as the gradation expression capability of the display image. That is, according to the step of mbiting the low gradation deletion data and selecting a digital correction value for n bits from the m-bit data, the low gradation area below the maximum difference gradation is selected. Therefore, it is possible to compensate for a decrease in gradation expression capability due to correction that sets a gradation voltage smaller than the gradation voltage of 0 gradation before correction. For this reason, the gradation expression capability of the display device can be maintained at a predetermined gradation.

The above-described processing in the driving method of the display device of the present invention is to perform independent γ processing on the data in which the gradation voltage is set and a certain gradation or less is discarded by the gradation setting method of the present invention. is there. Here, “independent γ processing” is processing that changes γ characteristics for each RGB data. In this case, in order to prevent gradation collapse and gradation skipping, for example, in 10-bit data (number of data 102 4). This includes the selection of 8 bits of data (number of data 256) as a digital correction value so that a desired characteristic (for example, γ characteristic) can be obtained from the above.

[0019] The above-mentioned “step of mbiting low gradation deletion data and selecting a digital correction value for n bits from the m-bit data” refers to m-bit data (low order Tone deletion Rather than simply converted data), m-bit gradation data (0 force 2 ^m — all of 1 gradation, that is, data with 2 ^m of data) Medium force Appropriate digital correction value This is done by selecting.

[0020] After the above steps, color crosstalk correction and pseudo multi-gradation may be performed. Here, pseudo multi-gradation is a process used when, for example, an 8-bit driver wants to express 10-bit equivalent. When 10-bit data is converted to 8-bit data, a noise pattern that determines the lower 2-bit data power is added to the upper 8-bit data instead of truncating the lower 2-bit data. It is to realize expressive power. A typical example of pseudo multi-gradation is FRC (Frame Rate Control).

[0021] The driving method of the display device of the present invention is such that, for integers m and n where 6≤n <m, display data equal to or less than the maximum difference gradation is extracted and used as low gradation deletion data. Tone removal After m-bits the data, adjacent pixels of the display device are coupled via parasitic capacitance. Information on the lower (m−n) bit data in the upper n-bit data out of the m-bit data processed by the above steps for correcting the crosstalk problem resulting from the above and the above-mentioned steps for correcting the crosstalk problem And a step to output as n-bit data! Don't panic! ,.

[0022] In the driving method of the display device of the present invention, when the display data displayed on the display device has 256 gradations, for example, as described in the embodiments described later, n = 8, If m = 10, the display data below the maximum difference gradation is extracted from the display data as low gradation deletion data, the low gradation deletion data is converted to 10 bits, and then the 10 bits are input. As for the data power, a digital correction value for 8 bits is selected. In this case, 256 gradations can be maintained as the gradation representation ability of the display image.

The present invention can also be configured as a program for causing a computer to execute the step of the gradation voltage setting method for the display device of the present invention.

[0024] In addition, in order to solve the above-described problems, the display device according to the present invention is a display device that displays an image by applying a gray voltage corresponding to each gray level to the display element to display an image. The gradation voltage difference is calculated for the gradation of the gradation area, and the gradation voltage of the maximum difference gradation corresponding to the largest difference among the obtained differences is set to be higher than the gradation voltage of the 0 gradation before correction. It is characterized by having correction means for correcting the gradation voltage corresponding to each gradation so as to decrease.

[0025] With the above configuration, it is possible to prevent the occurrence of an edge due to coupling between pixels. In other words, the display device according to the present invention prevents the occurrence of a large voltage change caused by coupling in a region below the maximum differential gradation in the low gradation region by correcting the gradation voltage by the correction unit. be able to. In other words, after correction, the voltage that was used as the drive voltage below the maximum difference gradation in the low gradation area before correction is used as the drive voltage for the gradation that is larger than the maximum difference gradation. Display is performed without using a combination of a gradation and a gradation voltage at which a large voltage change occurs. As a result, it is possible to prevent the occurrence of a discontinuous change in luminance that cannot be corrected using color crosstalk correction, and to prevent the occurrence of an edge in the display image of the display device.

Note that the number of gradations (display gradations) in the low gradation region for obtaining the gradation voltage difference is as described above. [0027] Further, in the above configuration, the correction means may be configured so that the gradation voltage corresponding to the gradation one larger than the maximum difference gradation becomes the gradation voltage of 0 gradation before correction. It is preferable to have a configuration that corrects the gradation voltage corresponding to the key.

[0028] This configuration is suitable for a display device in which the applied voltage is increased by increasing the force with low gradation.

Furthermore, it is preferable that the display device according to the present invention is driven by a source driver having a ladder resistance division such that a difference in gradation voltage has an extreme value.

[0030] A display device using a source driver (non-linear driver) having a ladder resistance division whose gradation voltage difference has an extreme value displays an edge (false contour) that cannot be eliminated by a conventional driving algorithm. Although it may occur in an image (display screen), according to the configuration of the present invention, the occurrence of the edge can be prevented.

[0031] The non-linear driver may be one in which the ladder resistance is combined so that the gradation luminance characteristic is γ = 2.2, for example. If the gradation resistance characteristic of the nonlinear driver is adjusted so that the gradation luminance characteristic is 7 = 2.2, severe voltage fluctuation occurs in the low gradation region, and the voltage difference has an extreme value. According to the configuration of the present invention, it is possible to prevent an edge from being generated by the intense voltage fluctuation. Also, in low gradation areas where edges occur due to intense voltage fluctuations, the power that varies depending on which gradation the reference voltage is input to and how much wrinkle is assumed as gradation luminance characteristics. It is an area below the 32nd floor.

[0032] Further, another display device according to the present invention is a display device for displaying an image by applying tl to a display element with a gradation voltage corresponding to each gradation in order to solve the above problem. The gradation voltage difference is calculated for the gradation in the low gradation area, and the gradation voltage of the maximum difference gradation corresponding to the maximum difference among the obtained differences is the gradation of 0 gradation before correction. The gradation voltage corresponding to each gradation is corrected so that it becomes smaller than the voltage, and for the integers m and n where 6≤n <m, the display data below the maximum difference gradation is taken out and the low gradation is deleted. After the low gradation deletion data is m-bit data, the m-bit data power is also provided with a correction means for selecting a digital correction value for n bits.

[0033] Further, another display device according to the present invention is provided for each gradation in order to solve the above problem. A display device that displays an image by applying the corresponding gradation voltage to the display element, and obtains the difference in gradation voltage for the gradation in the low gradation region, and corresponds to the maximum difference among the obtained differences. The gradation voltage corresponding to each gradation is corrected so that the gradation voltage of the maximum difference gradation is smaller than the gradation voltage of the 0 gradation before correction, and one gradation difference is added. Correction means for correcting the gradation voltage corresponding to each gradation is provided so that the gradation voltage corresponding to the large gradation becomes the gradation voltage of 0 gradation before correction, and the correction means includes 6≤ For integers m and n where n <m, the display data below the maximum difference gradation is taken out and used as low gradation deletion data. The low gradation deletion data is converted to m bits, and then the m bit converted data is converted to m bits. It is equipped with a correction means for selecting a digital correction value for one taka n bits. To have.

With the above configuration, in addition to the above effects, a predetermined gradation (2 ⁿ ) can be maintained as the gradation expression capability of the display image. In other words, if the low gradation deletion data is converted to m bits and a digital correction value corresponding to n bits of the m-bit keyed data is selected, the low gradation area below the maximum difference gradation is converted to the low gradation area before the correction. It is possible to compensate for a decrease in gradation expression capability due to correction for setting a gradation voltage smaller than the gradation voltage of 0 gradation. For this reason, the gradation expression capability of the display device can be maintained at a predetermined gradation.

The correction means of the display device of the present invention performs independent γ processing on the data in which the gradation voltage is set and a certain gradation or less is discarded. Here, independent γ processing is processing that changes γ characteristics for each RGB data. In this case, in order to prevent gradation collapse and gradation skipping, for example, the medium strength of 10-bit data (number of data 1024) is appropriate. It is configured to include the selection of data for bit data (number of data 256) as a digital correction value.

[0036] The above "move the low gradation deletion data and select the digital correction value for n bits from the m-bit data" means m-bit data (low-order data) Selects an appropriate digital correction value instead of m-bit gradation data (0 force is also 2 ^m — data of 2 ^m of all data). Is done.

[0037] The correction unit may be configured to perform color crosstalk correction and pseudo multi-gradation after selecting an appropriate digital correction value. Here, pseudo multi-gradation means For example, this is the process used when an 8-bit driver wants to express 10 bits. When 10-bit data is converted to 8-bit data, a noise pattern that determines the low-order 2-bit data power is added to the high-order 8-bit data rather than truncating the low-order 2-bit data. Realizes expressive power. A typical example of pseudo multi-gradation is FRC (Frame Rate Control).

[0038] In addition, in the display device according to the present invention, in the above configuration, the correction unit is low except for display data that is equal to or less than the maximum difference gradation with respect to integers m and n where 6≤n <m. Cross-talk problem caused by the fact that the low-gradation deletion data is converted to m-bit data by converting the low-gradation deletion data to m-bit data, and then the adjacent pixels of the display device are coupled through a parasitic capacitance. Of the above m-bit data corrected for the crosstalk problem, and the upper (n) bit data is added to the upper (n) bit data and output as n-bit data. Anyway.

[0039] According to the above configuration, when the display data displayed on the display device has 256 gradations, for example, if n = 8 and m = 10, the maximum difference gradation is determined from the display data. Except for the following display data, it is used as low gradation deletion data, and after the low gradation deletion data is 10 bits long, 8-bit digital correction value is selected from the 10 bits of data. In this case, 256 gradations can be maintained as the gradation representation capability of the display image.

[0040] Still other objects, features, and advantages of the present invention will be sufficiently enhanced by the following description. The benefits of the present invention will become apparent from the following description with reference to the accompanying drawings.

Brief Description of Drawings

FIG. 1 (a) is a graph showing an example of gradation voltage setting after correction by the gradation voltage setting method of the present invention.

FIG. 1 (b) is a graph showing a difference in gradation voltage setting shown in FIG. 1 (a).

FIG. 2 (a) is a graph showing an example of gradation voltage setting before correction by the gradation voltage setting method of the present invention.

FIG. 2 (b) is a graph showing a difference in gradation voltage setting shown in FIG. 2 (a). FIG. 3 is a block diagram showing an example of the configuration of a color display device in which gradation voltages are set according to the present invention.

4 is a plan view showing in detail the configuration of a display panel in the color display device of FIG. 3. FIG.

FIG. 5 is a diagram showing a state in which the display pattern changes in the display panel of FIG.

FIG. 6 is a diagram for comparing original white luminance with synthetic white luminance.

[Fig. 7] A graph showing the difference between the monochromatic luminance and the original monochromatic luminance as a difference in stimulus values of chromaticity X, Υ, and Z for each gradation.

[FIG. 8] A graph showing the error rate for each gradation with respect to the difference between the monochromatic luminance and the original monochromatic luminance.

FIG. 9 is a graph showing color crosstalk correction values when the other source is 0 gradation.

FIG. 10 is a block diagram showing the procedure of correction processing when displaying 8-bit 256 gradation using the gradation voltage after correction according to the present invention.

[Fig. 11] Fig. 11 is a schematic diagram for explaining a conventional technique and explaining crosstalk caused by another source line with respect to the source line.

FIG. 12 is a diagram showing that an edge due to a discontinuous luminance change occurs in a display image when a specific pattern is displayed.

BEST MODE FOR CARRYING OUT THE INVENTION

[1 Configuration of Display Device]

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 3, the color display device (display device) 1 according to the present embodiment includes a color crosstalk correction circuit (correction means) 2, a polarity inversion circuit 3, a timing controller 4, and a source driver 5. A gate driver 6, a display panel 7, and a storage unit 8. In FIG. 3, V and / or the configuration related to the present invention are largely omitted.

[0043] The color crosstalk correction circuit 2 indicates the gradation level of the red signal R, G (second display color) indicating the gradation level of the R color (first display color) input from the outside. In order to correct the applied voltage to each display pixel (not shown) in the display panel 7 based on the input color signal consisting of the green signal G and the blue signal B indicating the gradation level of the B color (second display color) Outputs color video signal R, -G '· Β'. The first display color is cyan, the second Even if the display color is magenta and the third display color is yellow.

In particular, the color crosstalk correction circuit 2 includes an applied voltage correction circuit (correction means) 9 and a saturation enhancement circuit (correction means) 10, and one of these two circuits is used. As a result, the voltage applied to each display pixel (not shown) in the display panel 7 is corrected. These applied voltage correction circuit 9 and saturation enhancement circuit 10 latch the input color video signal R'G'B and delay it one dot at a time, so that two display pixels connected to the same gate line are connected. The processing described later is performed.

Note that, as in the display device 1 of the present embodiment shown in FIG. 3, it is possible to include both the applied voltage correction circuit 9 and the saturation enhancement circuit 10 using other means (not shown), Either one may be configured to function. In addition, only one of the applied voltage correction circuit 9 and the saturation enhancement circuit 10 is provided!

[0046] The polarity inversion circuit 3 is based on the color video signal R, -G '· 基づき' that is digital data output from the applied voltage correction circuit 9 or the saturation enhancement circuit 10, and each display pixel in the display panel 7 This determines the data (analog data) of the voltage applied to.

The timing controller 4 generates a source driver timing signal and a gate driver timing signal for driving the source driver 5 and the gate driver 6 based on the input RGB synchronization signal. The source driver timing signal is input to the source driver 5 via the polarity inverting circuit 3.

[0048] The source driver 5 drives each source line connected to each display pixel provided in the display panel 7 via the TFT so that the voltage determined by the polarity inversion circuit 3 is applied to each display pixel. Is to do. The source driver 5 may be configured integrally with the polarity inversion circuit 3.

[0049] The gate driver 6 is for driving each gate line connected to each display pixel provided in the display panel 7 via a TFT.

[0050] The display panel 7 performs image display by driving a plurality of display pixels arranged in a matrix by a plurality of source lines and a plurality of gate lines. Specifically, as shown in FIG. 4, the source line Si (i is an integer) and the gate line Gj (j is an integer) are provided so as to be orthogonal to each other. Table at the intersection A display pixel 11 and a switching element 12 are provided.

Note that the configuration of the display panel 7 is not different from the configuration in the above-described conventional liquid crystal display device (see FIG. 11). Therefore, one display pixel among the display pixels 11 is set as the display pixel (A), and is driven by the same gate line G2 as the display pixel (A), and the display pixel ′ (A) is parasitic. When the display pixel (B) connected to the source line S3 connected via the capacitor via the switching element is the display pixel (B), the display pixel (A) is surrounded as follows. Parasitic capacitance Csda · Csdb · Cgd · Ccs is formed.

[0052] Parasitic capacitance Csda: parasitic capacitance formed between the source line for driving the display pixel (A) and the display pixel (A)

Parasitic capacitance Csdb: Parasitic capacitance formed between the source line for driving the display pixel (B) and the display pixel (A)

Parasitic capacitance Cgd: Parasitic capacitance formed between the gate line for driving the display pixel (A) and the display pixel (A)

Parasitic capacitance Ccs · · · Parasitic capacitance formed between the common electrode line and the display pixel (A).

[0053] As described above, the configuration of the display panel 7 is the same as the configuration of the display panel provided in the conventional liquid crystal display device, and thus each of the configurations provided in the display panel 7 by the conventional driving method. When the display pixels 11 are driven, the gray level of the target display pixel differs from the desired gray level due to the voltage applied to the source line that drives the other display pixels. This causes a crosstalk problem. .

For example, in the configuration shown in FIG. 4, when attention is paid to the display pixel (A) as the first display pixel, the gradation of the display pixel (A) drives the display pixel (B) as the second display pixel. Will be affected by the voltage applied to the source line S3.

[0055] [2 Crosstalk correction processing]

[2-1 Luminance balance fluctuation]

In the color display device 1 of the present embodiment, the applied voltage correction circuit 9 or the saturation enhancement circuit 10 is provided to improve the crosstalk problem that occurs as described above. In order to clarify the correction procedure of the input color video signal by these two circuits, the fluctuation of the luminance balance for each display pattern is explained below. For example, it is assumed that patterns 1 to 3 as shown in FIG. Specifically, in pattern 1, R, G, B, black, black, and black are displayed in order from the left for six adjacent display pixels. In pattern 2, black, G, B, R, black, and black are displayed. In Pattern 3, black, black, B color, R color, G color, and black color are displayed.

[0057] The images displayed on the display panel 7 by each of these patterns 1 to 3 should all be the same. In fact, the voltage applied to the display pixel on the left side of the display pixel displaying black (display pixel with gradation level 0: 0 gradation) is displayed in black. It is affected by the voltage applied to the display pixel. As a result, a gradation level slightly lower than the desired gradation level is displayed at the pixel on the left side.

[0058] For example, in pattern 1, since the B display pixel is adjacent to the black display pixel, the B color is displayed at a slightly lower gradation level than the desired gradation level. Similarly, in pattern 2, the R color is displayed at a gradation level slightly lower than the desired gradation level, and in pattern 3, the G color is displayed at a gradation level slightly lower than the desired gradation level. Thus, the luminance balance between a plurality of adjacent display pixels varies depending on the display pattern on the display panel.

[0059] Considering the case where white is displayed by three adjacent display pixels, as shown on the left side of the equation in FIG. 6, the R, G, and B colors in the order of the left force for the three display pixels. Ideal white is displayed when is displayed. In the following description, this ideal white color may be referred to as “original white luminance”, or simply “white luminance” or “white”.

[0060] On the other hand, as shown on the right side of the equation in FIG. 6, in the three adjacent display pixels, white should be displayed by switching the display to each of the following patterns 4 to 6. It is. Note that white display in this case may be referred to as “synthetic white brightness” or “synthetic white” in the following description.

That is, in the patterns 4 to 6, when the display color in each of the three display pixels is described in order of the left pixel force,

Pattern 4: R color, black, black Pattern 5: Black, G color, black

Pattern 6: Black, black, B color

It is.

[0062] Here, the original white brightness should be equal to the composite white brightness (red brightness + green brightness + blue brightness 1 * 2 * black brightness), but in fact, the composite white brightness is lower than the white brightness. . This is because, as described above, the voltage applied to the R, G, or B color display pixels fluctuates due to being dragged by the voltage applied to the black display pixels.

[0063] As described above, the white luminance and the composite white luminance (monochrome R + monochrome G + monochromatic B-2 * black) should be equal, but in actuality, in monochromatic display, the own source: monochromatic, Other sources: The condition of 0 is not satisfied, and color crosstalk occurs between adjacent sources. For this reason, as a result of the monochromatic luminance being lower than the original monochromatic luminance, the composite white luminance is smaller than the white luminance.

[0064] FIG. 7 shows the difference between the monochromatic luminance and the original monochromatic luminance caused by the above-described reason as the difference of the stimulation values of chromaticity X, Y, and Z (△ stimulation value) for each gradation. Is. In the figure, the vertical axis represents the difference in stimulus value between white and synthetic white of chromaticity X, Υ, and Z, and the horizontal axis represents gradation (0 to 255 gradations). In addition, when expressed in RGB, because the colors are entangled, in FIG. 7, the chromaticity stimulus value is used.

[0065] At first glance, the graph of FIG. 7 showing the change between white and composite white appears to cause a large error in the high gradation region. However, the display problem area in the display device is determined by the ratio of the error of the actual stimulus value to the stimulus value of the gradation to be originally displayed, not the absolute value of the error. Therefore, in the relationship between the stimulus value of gradation and the display, this “ratio of stimulus value error” (error rate) is important. Here, the error rate for each chromaticity is obtained by dividing the white error (that is, △ stimulus value) for X, Υ, and Z shown in Fig. 7 by using the stimulus values of X, Y, and Z for white luminance. It is obtained by calculation (division method).

[0066] Fig. 8 shows the result of obtaining the error rate for each gradation as described above. In the figure, the vertical axis shows the error rates of X, Y, and Z (stimulus value error rate), and the horizontal axis shows the tone. As shown in the figure, the ratio (error rate) of the error of the actual stimulus value to the stimulus value of the tone to be originally displayed is larger in the tone in the low tone region than in the high tone region. I'm angry. That is, it is understood that the gray scale error in the low gradation area has a large influence on the display, and that the problem in actual display is the gradation in the low gradation area rather than the high gradation area.

[0067] Subsequently, the force that causes the error rate of the error rate obtained as described above to be calculated is calculated, and the calculated result is used as a LUT (Look Up Table) to store the storage unit of the color display device 1. 8 (See Fig. 3). In order to obtain this LUT, the error rate for each of X, Y, and Z is divided by the difference when the color to be corrected changes by one gradation. However, even if the error rate is divided by using the above difference, the change gradation is divided by X, Y, and Z. It ’s no longer meaningful! You just get the data.

Therefore, in determining the LUT, the error rate of X is divided by the difference of X, the error rate of Y is divided by the difference of Y, and the error rate of Z is divided by the difference of Z. The result obtained by this calculation is that the error gradation power of X, Υ, and Z is almost the same curve. For this reason, the correction tables for R, G, and B may be the same. The graph shown in FIG. 9 shows the color crosstalk correction value when the other source is 0 gradation, and the value is taken out for every 32 gradations, for example, as the LUT. In the figure, the vertical axis indicates the corrected gradations of X, Υ, and Z, and the horizontal axis indicates the gradation.

[0069] [2-2 Color Crosstalk Correction Method]

Color crosstalk should be corrected correctly by voltage. In this embodiment, first, correction processing is performed by a driving algorithm. For this reason, the correction gradation of display pixel A is calculated from the combination of the gradation of display pixel A as shown in FIG. 4 and the gradation of display pixel B adjacent to display pixel A, and is used as the display pixel. It is also realistic to add a method to the gradation data of A.

[0070] An example of the procedure is shown below.

(1) Measure the brightness and chromaticity of the original white and the actual RGB colors for each gradation.

(2) The white error (white—composite white (R + G + B—2 * black)) is calculated for each gradation (ie, △ stimulus value). (3) Calculate the white error rate (white error Z white luminance obtained in (2) above) for each gradation.

(4) Divide the white error rate by the difference of the combined white luminance to obtain the corrected gradation C of display pixel A when B display pixel is 0 gradation.

(5) The correction value when the B display pixel is not 0 gradation is the correction value SO when the gradation of the A display pixel and the B display pixel are the same, so when A≥B, between C and 0 Interpolate linearly. When A <B, the correction value is 0.

[0071] As a practical matter, the correction gradation obtained in this way varies greatly depending on the panel design, driver, gradation setting, etc., so it is easy to create an algorithm for correcting with a unified equation. Therefore, for example, these correction values taken every 32 gradations are provided as LUTs, and the final correction gradation is obtained by performing interpolation calculation according to the target gradation. Table 1 below shows examples of LUTs determined by gradation and adjacent gradation.

[0072] [Table 1]

[3 Correction of low gradation area]

By the above-described method, color crosstalk correction that corrects the gradation of the display pixel in consideration of the coupling with the adjacent pixel can be performed from the gradation of the display pixel and the adjacent pixel. However, even if the above-described color crosstalk correction is used, there are cases in which it is not possible to correct the low gradation region where the voltage fluctuation is severe. Specifically, when the gradation voltage is set as shown in FIG. 2 (a), severe voltage fluctuations occur in the low gradation region as shown in FIG. 2 (b). Tsuma When a non-linear driver is used to adjust the γ characteristics of the liquid crystal display more smoothly, for example, the gradation voltage characteristics shown in Fig. 2 (a) are obtained, and as a result, as shown in Fig. 2 (b), Severe voltage fluctuation occurs in the low gradation region. Due to this voltage fluctuation, that is, the difference in gradation voltage in the low gradation region changes greatly, there arises a problem that the region where the luminance change is discontinuous is recognized as an edge (false contour). . Therefore, in this embodiment, the following correction method is added to the color crosstalk correction described above to correct the gradation voltage in the low gradation region.

[0073] First, the difference of each gradation voltage is obtained for the gradation voltage before correction. Figure 2 (b) is a graph showing the difference for each calculated gray scale voltage. As shown in the figure, the difference in grayscale voltage changes greatly in the low grayscale region, and the 0 grayscale (VO) force increases toward the 5th grayscale (V5). ), The maximum difference is taken, and for gradations larger than these five gradations (maximum difference gradation), the difference is sharply reduced. The problem that the above-mentioned edge occurs in the display image before correction is due to the fact that the voltage in the region where the difference changes greatly is used as the gradation voltage in the low gradation region (0 to 5 gradations). And then.

[0074] Therefore, the gradation voltage of the maximum difference gradation is corrected so that the voltage of the gradation area where the difference greatly changes is not used as the driving voltage of the gradation below the maximum difference gradation (low gradation area). The gradation voltage is corrected so as to be smaller than the driving voltage of the previous 0 gradation. As a result, the above-mentioned problem of edge generation can be solved.

In the gradation voltage correction as described above, for example, the gradation voltage may be set so as to be a gradation voltage of 6 gradations (V6) of VO force before the correction. Along with this correction, the gradation voltages corresponding to the other gradations are reset so as to have continuity. Fig. 1 (a) shows the gradation voltage setting after correcting the gradation voltage as described above. By correcting the grayscale voltage as shown in the figure, as shown in Fig. 1 (b), the image is displayed without using the low grayscale region where the magnitude of the grayscale voltage difference is V5 or less. be able to. In other words, the drive voltage for the low gradation region of V5 (5 gradations) or less where the difference is maximum is set to be smaller than the voltage value of the VO drive voltage before correction. The adverse effect on the display due to the lower low gradation region can be eliminated.

In FIG. 1B and FIG. 2B, in the low gradation region, the peak of the difference in gradation voltage ( There are two local maxima. This is a result of matching the ladder resistance of the driver so that the gradation luminance characteristic is _Ύ = _2.2 . In addition, the second small maximum value that exists in the high gradation region than V5 is considered to be close to noise, as the difference result of the gradation voltage in the high gradation region is rattling. . For this reason, as a result of obtaining the difference, the gradation drive voltage having the maximum difference among the multiple maximum values in the low gradation region where the difference in the gradation voltage is higher is the 0 gradation before the correction. The drive voltage is adjusted to be lower than the grayscale voltage (target VO voltage). Table 2 shows specific examples of drive voltage settings for each gradation before and after correction using the above method.

[0077] [Table 2]

In this embodiment, 6 gradations (V6) = 0. 5V is because the gradation voltage (V0) of 0 gradation of the current LCD module is 0.5V. In this case, the effect of preventing the occurrence of edges does not change, but the contrast of the display is lowered (V6 = 0.5V, CR = 840) V6 = 1.0V and CR = 760.) Since it is not desirable that CR divide 800, the gradation voltage of V6 (6 gradations), which is one gradation larger than V5 (5 gradations), where the gradation voltage difference becomes the maximum value (maximum value) Used as V0 of LCD module in a row, preferably 0.5V.

As described above, according to the grayscale voltage setting method of the present embodiment, the grayscale voltage of the maximum differential grayscale is prevented in order to prevent the occurrence of a region where the luminance change recognized as an edge is discontinuous. The correction is made so that it is smaller than the gradation voltage of 0 gradation (target V0 voltage) before correction. A data processing method that is preferably used together with this gradation voltage correction will be described below. The following data processing method is performed by the applied voltage correction circuit (correction means) 9 or the saturation enhancement circuit (correction means) 10 of the display device 1 shown in FIG.

[0079] As shown in FIG. 10, digital data processing corrects the use of 6 to 255 gradations out of 8-bit 256 gradations (0 to 255 gradations) and low gradation removal data. After that, the processing to select an appropriate digital correction value from the 10-bit data (independent γ processing), color crosstalk correction, pseudo-multiple By performing gradation, it is possible to maintain the gradation expression capability in image display at 256 gradations. Each correction process shown in the figure will be briefly described below.

[0080] Independent γ processing: correction for converting an input gradation into a specified gradation. Since the conversion process is determined only by the input gradation, it can be realized using a simple LUT. In order to avoid losing gradation information at the time of conversion, it is common to convert, for example, 8-bit data into 10-bit data as in the present embodiment.

Color crosstalk correction: Follow the method described in [2 Crosstalk correction processing].

Pseudo multi-tone: For example, techniques such as FRC (Frame Rate Control) and dithering. As an example, if the driver output is n-bit data, out of m-bit data where m> n, the upper n-bit data is output with a noise pattern obtained from the lower (mn) bit data information power, and n in bit drivers are techniques such as to have equivalent data expressive and m-bit data (in this embodiment is n = 8, m = 10. ) 0

Note that each unit and each processing step of the display device according to the present embodiment executes a program stored in a storage means such as a calculation means output ROM (Read Only Memory) or RAM such as a CPU, and inputs such as a keyboard. It can be realized by controlling the means, the output means such as a display, or the communication means such as an interface circuit. Therefore, the computer having these means reads the recording medium storing the program and executes the program, thereby realizing the various functions and the various processes of the display device of the present embodiment. be able to. In addition, the above program is a removable recording medium. By recording on the body, the above-described various functions and various processes can be realized on any computer.

As this recording medium, a program medium such as a memory (not shown) such as ROM may be used for processing by the microcomputer, and V not shown is an external storage device. It may be a program medium provided with a program reading device and readable by inserting a recording medium therein.

[0083] In any case, the stored program is preferably configured to be accessed and executed by a microprocessor. Further, it is preferable that the program is read out, and the read program is downloaded to the program storage area of the microcomputer and the program is executed. Note that this download program is stored in advance in the main unit.

[0084] Further, the program medium is a recording medium configured to be separable from the main body, such as a tape system such as a magnetic tape or a cassette tape, a magnetic disk such as a flexible disk or a hard disk, or a disk such as a CDZMOZMDZDVD. Disk system, card system such as ic card (including memory card), mask ROM, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read)

Only Memory) and recording media that carry a fixed program including semiconductor memory such as flash ROM.

[0085] Further, if the system configuration is capable of connecting a communication network including the Internet, the recording network is preferably a recording medium that fluidly carries the program so as to download the program.

[0086] Further, when the communication network capability is downloaded as described above, it is preferable that the download program is stored in the main device in advance or installed with another recording medium strength. .

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention. Industrial applicability In a display device that displays an image by applying a gradation voltage corresponding to each gradation to a display element, it is possible to eliminate display defects such as edges (false contours) caused by color crosstalk. .

Claims

The scope of the claims

[1] A gradation voltage setting method for a display device for displaying an image by applying a gradation voltage corresponding to each gradation to a display element,

The step of obtaining the gradation voltage difference for the gradation of the low gradation region, and the gradation voltage of the maximum difference gradation corresponding to the maximum difference among the obtained differences are represented by the gradation voltage of 0 gradation before correction. And a step of correcting the gradation voltage corresponding to each gradation so as to be smaller than the gradation voltage setting method for a display device.

[2] The gradation voltage corresponding to each gradation is corrected so that the gradation voltage corresponding to the gradation one larger than the maximum difference gradation becomes the gradation voltage of 0 gradation before correction. The gradation voltage setting method for a display device according to claim 1, wherein

[3] The gradation of the display device according to claim 1 or 2, wherein the display device is driven by a source driver having a ladder resistance division in which a difference in gradation voltage has an extreme value. Voltage setting method.

[4] A driving method of a display device for displaying an image by applying a gradation voltage corresponding to each gradation to a display element,

A gradation voltage of the display device is set by the method according to claim 1 or 2,

For integers 111 and n where 6≤11 <111, display data below the maximum difference gradation is extracted as low gradation deletion data, the low gradation deletion data is converted to m bits, and then the corresponding m bits The display device driving method further comprising the step of selecting a digital correction value corresponding to the converted data force n bits.

[5] For integers 111 and n where 6≤11 <111, the display data below the maximum difference gray level is excluded, and the low gray level deletion data is converted to m bits. Correcting for crosstalk problems arising from adjacent pixels of the display device being coupled through parasitic capacitances;

Of the _m- bit data processed by the above steps to correct the crosstalk problem, the upper n-bit data is appended with the lower (mn) bit data information and output as n-bit data. 5. The display device driving method according to claim 4, further comprising:.

[6] A program for causing a computer to execute the steps according to claim 1.

[7] A display device for displaying an image by applying a gradation voltage corresponding to each gradation to a display element!

The gradation voltage difference is calculated for the gradation in the low gradation area, and the gradation voltage of the maximum difference gradation corresponding to the maximum difference among the obtained differences is calculated from the gradation voltage of the 0 gradation before correction. A display device comprising correction means for correcting a gradation voltage corresponding to each gradation so as to be smaller.

[8] The correction means has a gradation voltage corresponding to a gradation one larger than the maximum difference gradation.

8. The display device according to claim 7, wherein a gradation voltage corresponding to each gradation is corrected so as to be a gradation voltage of 0 gradation before correction.

9. The display device according to claim 7, wherein the display device is driven by a source driver having a ladder resistance division in which a difference in gradation voltage has an extreme value.

[10] A display device that displays an image by applying a gradation voltage corresponding to each gradation to the display element!

The gradation voltage difference is calculated for the gradation in the low gradation area, and the gradation voltage of the maximum difference gradation corresponding to the maximum difference among the obtained differences is greater than the gradation voltage of the 0 gradation before correction. In addition to correcting the gradation voltage corresponding to each gradation so that the

For integers 111 and n where 6≤11 <111, display data below the maximum difference gradation is extracted as low gradation deletion data, the low gradation deletion data is converted to m bits, and then the corresponding m bits A display device characterized by comprising correction means for selecting a digital correction value corresponding to n-bit data power.

[11] A display device that displays an image by applying a gradation voltage corresponding to each gradation to the display element tl.

The gradation voltage difference is calculated for the gradation in the low gradation area, and the gradation voltage of the maximum difference gradation corresponding to the maximum difference among the obtained differences is greater than the gradation voltage of the 0 gradation before correction. The gradation voltage corresponding to each gradation is corrected so that the gradation voltage becomes smaller, and the gradation voltage corresponding to the gradation one larger than the maximum difference gradation is the gradation voltage of the 0 gradation before correction. Correction means for correcting the gradation voltage corresponding to each gradation is provided, For the integers 111 and n where 6≤11 <111, the correction means takes out display data below the maximum difference gradation and uses it as low gradation deletion data. And a correction means for selecting a digital correction value corresponding to the m bits of data power n bits.

The correction means removes the display data below the maximum difference gradation for the integers 111 and n where 6≤11 <111, and uses the low gradation deletion data as mbits. After correcting for m-bit data, the problem of crosstalk caused by the adjacent pixels of the display device being coupled through a parasitic capacitance is corrected.

Of the _m- bit data corrected for the crosstalk problem, V is configured to add the information of the lower (mn) bit data to the upper n-bit data and output as n-bit data. The display device according to claim 10 or 11.