KR20050093818A - Display unit and displaying method - Google Patents

Abstract

Luminous and non-luminous combination patterns in the n-th to m-th sub-fields (m and n are positive integers smaller than the number of all sub-fields, and m>n) in first to fourth pixels vertically and laterally adjacent to respective areas on a display panel are different from each other. The gradation values displayed respectively by a first and second pixels located in one diagonal position out of first to fourth pixels vertically and laterally adjacent to respective areas on a display panel are lower than an average of gradation values displayed by first to fourth pixels, and the gradation values displayed respectively by a third and fourth pixels located in the other diagonal position are higher than an average of gradation values displayed by first to fourth pixels.

Description

Display device and display method {DISPLAY UNIT AND DISPLAYING METHOD}

The present invention relates to a display device and a display method for performing gradation display by the subfield method.

The plasma display device using the plasma display panel as the self-luminous image display has the advantage that the thickness and the large screen can be reduced. In this plasma display device, an image is displayed by using light emission at the time of discharge of the discharge cells constituting the pixel. In addition, since the plasma display panel emits light reasonably, a subfield method for displaying halftones is used by superimposing a plurality of overlapping binary images in time.

In the subfield method, one field is time-divided into a plurality of subfields, and each subfield is superimposed. The overlap amount of each subfield corresponds to the light emission amount of each subfield. For example, the number of light emission times is used as the overlapping amount, and the total amount of the overlapping amounts of each subfield corresponds to the brightness of the video signal, that is, the gradation level.

In the subfield method, since the light emission order of the plurality of subfields is fixed, the eyes of the person viewing the light emitting subfield move over the plurality of pixels, so that different subfields are viewed for each pixel. As a result, the viewer perceives a gradation level significantly different from the gradation level to be expressed. In particular, when the surrounding pixels have continuity, a false outline of a stripe shape is perceived as if the gradation level is lost. It is known that the display quality is remarkably impaired by this false outline. The above false contour that appears only in the case of moving images is called pseudo contour noise ("Pseudo contour noise shown in pulse-varying modulated moving image display": Technical Report, Television Society, Vol. 19, No. 2, IDY 95-21, pp. 61-66).

FIG. 11 is a schematic diagram for explaining pseudo contour noise visually recognized when a human eye moves over different pixels. FIG.

In FIG. 11, white circles represent light emitting subfields, black circles represent non-light emitting subfields, and a plurality of subfields are referred to as SF1 to SF10 in the order of small overlapping amounts. In addition, the columns A, B, C, and D shown in FIG. 11 represent column numbers of pixels in the horizontal direction, and row 1 represents row numbers of pixels in the vertical direction.

In FIG. 11, when the human eye does not move from the position of the column A row 1 or the position of the column B row 1, the human eye is placed in the subfields SF1 to SF10 or the column B row of the pixels arranged in the column A row 1. The subfields SF1 to SF10 of the pixels arranged at 1 are respectively recognized. In this case, the light emission patterns of the pixels are "1101110111" and "0111011111", respectively, and the gray level values recognized by the human eye are "955" and "1006", respectively. As such, the value of the gray level of the pixels arranged in the column A row 1 is recognized as lower than the value of the gray level of the pixels arranged in the column B row 1.

As indicated by the solid arrows in FIG. 11, when the human eye I1 moves from the pixels arranged in the column A row 1 to the pixels arranged in the column C row 1, the human eye is connected to the pixels arranged in the column A row 1. The subfields SF1 to SF3, the subfields SF4 to SF8 of the pixels arranged in the column B row 1, and the subfields SF9 and SF10 of the pixels arranged in the column C row 1 are sequentially recognized. In this case, the light emission pattern is "1101011111", and the value of the gradation recognized by the human eye is "1003".

Similarly, as indicated by the dashed arrows in FIG. 11, when the human eye I2 moves from the pixel arranged in column B row 1 to the pixel arranged in column D row 1, the human eye is placed in column B row 1. The subfields SF1 to SF3 of the pixels, the subfields SF4 to SF8 of the pixels arranged in the column C row 1 and the subfields SF9 and SF10 of the pixels arranged in the column D row 1 are sequentially recognized. In this case, the light emission pattern is "0111110111", and the value of the gray scale recognized by the human eye is "956".

In this way, the value of the gradation to be originally displayed as "955" is recognized as "1003" by the movement of the gaze I1, and the value of the gradation to be originally displayed as "1006" by the movement of the gaze I2 is "956". Is perceived as low. In this way, the relationship between the gray level values of the pixels adjacent to each other in row 1 is reversed by the movement of the line of sight. Such a change in the gray level value of the pixel is recognized as pseudo contour noise.

As a method of reducing pseudo contour noise, there is a method of selecting a gradation level in which light emitting subfields are continuously present as a gradation level at which pseudo contour noise is less likely to occur, and using only the selected gradation level for display. In this case, for gradation levels other than the selected gradation level, by selecting two gradation levels in which similar contour noise which interposes the gradation levels up and down is unlikely to occur, and displaying the two gradation levels alternately for each field. (For example, see Japanese Patent Laid-Open No. 2000-276100).

As another method of reducing pseudo contour noise, there is a method of reducing occurrence of pseudo contour noise by reducing the number of subfields. In this case, in order to express the gradation level that cannot be expressed by reducing the number of subfields, one set of four pixels adjacent to each other in the top, bottom, left, and right sides, and in each of the pixel data corresponding to each one set of pixels, The above-mentioned non-expressable gradation levels are expressed as area gradations by allocating and adding four dither coefficients each having different coefficient values. In addition, the noise caused by the dither pattern is reduced by changing the dither coefficients added for each field (see, for example, Japanese Patent Application Laid-Open No. 10-98663).

However, in the method of reducing pseudo outline noise, image quality deterioration occurs by reducing the number of gradation levels that can be expressed.

Disclosure of the Invention

SUMMARY OF THE INVENTION An object of the present invention is to provide a display device and a display method capable of reducing pseudo contour noise without deteriorating the image quality.

Another object of the present invention is to provide a display device and a display method which can efficiently reduce pseudo contour noise based on the generation degree of pseudo contour noise.

A display device according to one aspect of the present invention is a display device that performs gradation display by a subfield method based on a video signal having a gradation level, and includes a plurality of first to fourth pixels adjacent to each other in up, down, left, and right directions. And a first to fourth tables, each of which includes a display panel composed of a region of the first to fourth pixels, and a plurality of first to fourth light emitting patterns corresponding to the first to fourth pixels, and based on the gradation level of the video signal. Select first to fourth light emission patterns corresponding to the first to fourth pixels of each area from the first to fourth tables, and for each subfield based on the selected first to fourth light emission patterns A gradation display section for performing gradation display by emitting or non-emitting the first to fourth pixels in the region, wherein a combination pattern of light emission and non-emission in a predetermined subfield is selected from the first to fourth subfields. 4 luminous patterns stand between Are different from each other, and in each area, the first and second pixels are arranged at one diagonal position, the third and fourth pixels are arranged at the other diagonal position, and at each gradation level, the first and second pixels are arranged. The value of the gradation respectively expressed by the light emission pattern is lower than the average value of the gradation represented by the first to fourth light emission patterns, and the value of the gradation respectively represented by the third and fourth light emission patterns is higher than the average value.

In the display device according to the present invention, the display panel is composed of a plurality of regions each including first to fourth pixels adjacent to each other in the top, bottom, left, and right directions. In each area, the first and second pixels are disposed at one diagonal position, and the third and fourth pixels are disposed at the other diagonal position.

Further, first to fourth tables each containing a plurality of first to fourth light emission patterns corresponding to the first to fourth pixels are stored. Based on the gradation level of the video signal, first to fourth light emission patterns respectively corresponding to the first to fourth pixels of each area are selected from the first to fourth tables, and the plurality of first to fourth light emission selected respectively. Based on the pattern, the first to fourth pixels of each area of the display panel are emitted or non-emitted for each subfield. Thus, gray scale display is performed.

In this case, the first to be expressed based on the first to fourth light emission patterns by the combination pattern of light emission and non-light emission in a predetermined subfield among the plurality of subfields being different from each other between the first to fourth light emission patterns. The value of the gradation of the fourth pixel is different. The gray level of each area is expressed by the average value of the gray level values of the first to fourth pixels.

In particular, by using a subfield in which pseudo contour noise is unlikely to occur as a predetermined subfield, the pseudo contour noise can be suppressed.

Even when the line of sight moves in any direction, the change in the value of the gradation of the first to fourth pixels disappears from each other. As a result, the change in the value of the recognized pixel is not recognized as pseudo contour noise.

As a result, pseudo contour noise can be reduced without degrading the image quality.

The plurality of subfields have different overlapping amounts, and the predetermined subfield is the largest of the subfields in which the pixel emits light in the order in which the overlapping amount decreases from the subfield with the maximum overlapping amount to the subfield with the minimum overlapping amount. A predetermined number of subfields may be included as a head of a subfield having an overlapping amount of.

In this case, since the subfield which most affects the value of the gradation to be expressed is used as the predetermined subfield, the effect of reducing pseudo contour noise is increased. In addition, since the predetermined subfield is set to be limited to a subfield having a large overlap amount where pseudo contour noise is likely to occur, the number of design steps is reduced.

In the two or more light emission patterns among the first to fourth light emission patterns, the combination patterns in the predetermined subfields may be the same between adjacent gradation levels, respectively.

In this case, it is possible to reduce noise caused by the pseudo contour noise and the dither pattern because the combination patterns in the predetermined subfields are the same between adjacent gradation levels.

The display device further includes a detector that detects a degree of pseudo contour noise in the image displayed on the display panel, and the gray scale display part includes a plurality of fifth to eighth emission patterns corresponding to the first to fourth pixels, respectively. The fifth to eighth tables are further stored, and one of the sets of the first to fourth tables and the set of the fifth to eighth tables is selected based on the detection result by the detection unit, and the fifth to eighth tables are selected. When the set of the eighth table is selected, the fifth to eighth light emission patterns corresponding to the first to fourth pixels of each area are selected from the fifth to eighth tables selected based on the gradation level of the image signal, and the selected The gray scale display is performed by emitting or non-emitting the first to fourth pixels of each region of the display panel based on the fifth to eighth light emission patterns, thereby performing light emission and non-light emission in a predetermined subfield. Combination pattern is the fifth to eighth shot Some of the patterns are the same and at each gradation level, the value of the gradation represented by the fifth and sixth light emission patterns, respectively, is higher than the average value of the gradations represented by the fifth to eighth light emission patterns, and the seventh and The value of the gradation represented by the eighth light emission pattern may be lower than the average value.

In this case, the degree of pseudo contour noise in the image displayed on the display panel is detected.

Further, fifth to eighth tables each including a plurality of fifth to eighth light emission patterns corresponding to the first to fourth pixels are further stored. One set is selected from the set of 1st-4th table and the set of 5th-8th table based on a detection result. When the set of the fifth to eighth tables is selected, the fifth to eighth light emission patterns corresponding to the first to fourth pixels of each area are respectively selected from the fifth to eighth tables selected based on the gradation level of the video signal. Is selected. Based on the selected fifth to eighth light emission patterns, the first to fourth pixels of each area of the display panel are emitted or non-emitted for each subfield. Thereby, gradation display is executed.

The gray level of each area is expressed by the average value of the gray level values of the first to fourth pixels. As in the case where the first to fourth light emission patterns are used, at each gray level, the value of the gray level respectively expressed by the fifth and sixth light emitting patterns is higher than the average value of the gray levels represented by the fifth to eighth light emitting patterns. It is low and the value of the gradation represented by the seventh and eighth light emitting patterns, respectively, is higher than the average value. This eliminates pseudo contour noise.

In particular, the combined pattern of light emission and non-light emission in a predetermined subfield is the same in some of the fifth to eighth light emission patterns. Thereby, although the effect of reducing pseudo contour noise is small compared with the case where the 1st-4th light emission patterns are used, it becomes possible to reduce the noise by a dither pattern.

By selectively using the first to fourth light emitting patterns or the eighth light emitting patterns in accordance with the degree of the pseudo contour noise, the noise caused by the dither pattern can be minimized and the pseudo contour noise can be reduced.

The gradation display section stores the difference between each gradation level and the value of the gradation represented by the first to fourth light emission patterns as the first to fourth dither values, and further includes a first image corresponding to the gradation level of the video signal. A dither value generator for outputting first to fourth dither values, a coefficient adder for adding first to fourth dither values generated by the dither value generator to the gradation level of the video signal, and a first to fourth table Further, the first to fourth light emission patterns are selected from the first to fourth tables based on the addition result of the coefficient adder, and each area of the display panel is displayed for each subfield based on the selected first to fourth light emission patterns. You may include the drive part which light-emits or does not light-emit 1st-4th pixel.

In this case, the difference between the respective gradation levels and the values of the gradations represented by the first to fourth light emitting patterns, respectively, is stored as the first to fourth dither values, and the first to the first corresponding to the gradation levels of the video signal. 4 The dither value is output. The first to fourth dither values are added to the gradation level of the video signal, respectively. The first to fourth tables are stored, and the first to fourth light emission patterns are selected from the first to fourth tables based on the addition result. Based on the selected first to fourth light emission patterns, the first to fourth pixels of each area of the display panel are emitted or non-emitted for each subfield.

Thus, gray scale display is performed using the 1st-4th dither value, and pseudo contour noise is reduced.

When the gray level of the video signal and the average value of the grays respectively expressed by the first to fourth light emitting patterns are different, the display device is used to determine the gray levels represented by the gray level of the video signal and the first to fourth light emitting patterns. A diffusion device may be further provided to spread the error with the average value to the video signal spatially and / or temporally.

In this case, when the gradation level of the video signal and the average value of the gradations respectively expressed by the first to fourth light emission patterns are different, the gradation level of the video signal and the average value of the gradations represented by the first to fourth light emission patterns respectively. Error is spread to the video signal spatially and / or temporally. This makes it possible to express the value of the gray level corresponding to the gray level of the video signal.

A display method according to another aspect of the present invention is a display method for performing gradation display in a display panel by a subfield method based on a video signal having a gradation level, wherein the display panels are adjacent to first, fourth, and fourth sides Comprising a plurality of regions each containing a pixel, in each region, the first and second pixels are arranged at one diagonal position, the third and fourth pixels are arranged at the other diagonal position, the first to Storing the first to fourth tables each comprising a plurality of first to fourth light emission patterns corresponding to the fourth pixel, and the first to fourth tables based on the gradation level of the video signal. Selecting first to fourth emission patterns corresponding to the first to fourth pixels, and emitting the first to fourth pixels of respective regions of the display panel for each subfield based on the selected first to fourth emission patterns. Or gradation by non-emitting And a combination pattern of light emission and non-light emission in a predetermined subfield among the plurality of subfields is different from each other between the first and fourth light emission patterns, and in each gradation level, the first and The value of the gradation represented by the second light emission pattern is lower than the average value of the gradation represented by the first to fourth light emission patterns, and the value of the gradation represented by the third and fourth light emission patterns respectively is higher than the average value. .

In the display method which concerns on this invention, a display panel is comprised from the several area | region which respectively contains the 1st-4th pixel adjacent to upper and lower sides. In each area, the first and second pixels are disposed at one diagonal position, and the third and fourth pixels are disposed at the other diagonal position.

Further, first to fourth tables each containing a plurality of first to fourth light emission patterns corresponding to the first to fourth pixels are stored. Based on the gradation level of the video signal, first to fourth light emission patterns respectively corresponding to the first to fourth pixels of each area are selected from the first to fourth tables, and the plurality of first to fourth light emission selected respectively. Based on the pattern, the first to fourth pixels of each area of the display panel are emitted or non-emitted for each subfield. Thus, gray scale display is performed.

In this case, the first to be expressed based on the first to fourth light emission patterns by the combination pattern of light emission and non-light emission in a predetermined subfield among the plurality of subfields being different from each other between the first to fourth light emission patterns. The value of the gradation of the fourth pixel is different. The gray level of each area is expressed by the average value of the gray level values of the first to fourth pixels.

In particular, by using a subfield in which pseudo contour noise is unlikely to occur as a predetermined subfield, the pseudo contour noise can be suppressed.

Even when the line of sight moves in any direction, the change in the value of the gradation of the first to fourth pixels disappears from each other. As a result, the change in the value of the recognized pixel is not recognized as pseudo contour noise.

As a result, pseudo contour noise can be reduced without degrading the image quality.

The plurality of subfields have different overlapping amounts, and the predetermined subfield is one of the subfields in which the pixel emits light in the order of decreasing the overlapping amount from the subfield with the maximum overlapping amount to the subfield with the minimum overlapping amount. The predetermined number of subfields may be included as a head of the subfield having the maximum overlap amount.

In this case, since the subfield which most affects the value of the gradation to be expressed is used as the predetermined subfield, the effect of reducing pseudo contour noise is increased. In addition, since the predetermined subfield is set to be limited to a subfield having a large overlap amount where pseudo contour noise is likely to occur, the number of design steps is reduced.

In two or more light emission patterns among the first to fourth light emission patterns, the combination patterns in the predetermined subfields may be the same between adjacent gray level levels.

In this case, it is possible to reduce the noise due to the pseudo contour noise and the dither pattern because the combination patterns in the predetermined subfields are the same between adjacent gradation levels.

The display method includes steps of detecting a degree of pseudo contour noise in an image displayed on a display panel, and fifth to eighth each including a plurality of fifth to eighth light emission patterns corresponding to the first to fourth pixels. Further storing the table, selecting one of a set of the first to fourth tables and a set of the fifth to eighth tables based on the detection result of the degree of the pseudo contour noise; Selecting fifth to eighth light emission patterns corresponding to the first to fourth pixels of each region from the fifth to eighth tables selected based on the gradation level of the image signal when the set of eight tables is selected; And performing gradation display by emitting or non-emitting the first to fourth pixels of each area of the display panel for each subfield based on the selected fifth to eighth light emission patterns, in the predetermined subfield. Combination of luminescence and non-luminescence Some of the fifth to eighth light emission patterns have the same turn, and at each of the gradation levels, the values of the gradations respectively represented by the fifth and sixth light emission patterns are the gradations represented by the fifth to eighth light emission patterns. It may be lower than the average value of, and the value of the gradation represented by the seventh and eighth light emitting patterns may be higher than the average value.

In this case, the degree of pseudo contour noise in the image displayed on the display panel is detected.

Further, fifth to eighth tables each including a plurality of fifth to eighth light emission patterns corresponding to the first to fourth pixels are further stored. One set is selected from the set of 1st-4th table and the set of 5th-8th table based on a detection result. When the set of the fifth to eighth tables is selected, the fifth to eighth light emission patterns corresponding to the first to fourth pixels of each area are respectively selected from the fifth to eighth tables selected based on the gradation level of the video signal. Is selected. Based on the selected fifth to eighth light emission patterns, the first to fourth pixels of each area of the display panel are emitted or non-emitted for each subfield. Thereby, gradation display is executed.

The gray level of each area is expressed by the average value of the gray level values of the first to fourth pixels. As in the case where the first to fourth light emission patterns are used, at each gray level, the value of the gray level respectively expressed by the fifth and sixth light emitting patterns is higher than the average value of the gray levels represented by the fifth to eighth light emitting patterns. It is low and the value of the gradation represented by the seventh and eighth light emitting patterns, respectively, is higher than the average value. This eliminates pseudo contour noise.

In particular, the combined pattern of light emission and non-light emission in a predetermined subfield is the same in some of the fifth to eighth light emission patterns. Thereby, although the effect of reducing pseudo contour noise is small compared with the case where the 1st-4th light emission patterns are used, it becomes possible to reduce the noise by a dither pattern.

By selectively using the first to fourth light emitting patterns or the eighth light emitting patterns in accordance with the degree of the pseudo contour noise, the noise caused by the dither pattern can be minimized and the pseudo contour noise can be reduced.

The step of executing gradation display includes storing the difference between each gradation level and the value of the gradation represented by the first to fourth light emission patterns as the first to fourth dither values and the gradation level of the video signal. Outputting corresponding first to fourth dither values, adding first to fourth dither values generated to the gradation level of the video signal, storing the first to fourth tables, and adding Selecting the first to fourth emission patterns from the first to fourth tables based on the result, and the first to fourth pixels of each region of the display panel for each subfield based on the selected first to fourth emission patterns. It may include the step of emitting or not emitting light.

In this case, the difference between the respective gradation levels and the values of the gradations represented by the first to fourth light emitting patterns, respectively, is stored as the first to fourth dither values, and the first to the first corresponding to the gradation levels of the video signal. 4 The dither value is output. The first to fourth dither values are added to the gradation level of the video signal, respectively. The first to fourth tables are stored, and the first to fourth light emission patterns are selected from the first to fourth tables based on the addition result. Based on the selected first to fourth light emission patterns, the first to fourth pixels of each area of the display panel are emitted or non-emitted for each subfield.

Thus, gray scale display is performed using the 1st-4th dither value, and pseudo contour noise is reduced.

The display method is based on the gradation level represented by the gradation level of the video signal and the first to fourth emission patterns, respectively, when the gradation level of the video signal and the average value of the gradations represented by the first to fourth emission patterns are different. The method may further include spreading the error with the average value in the video signal spatially and / or temporally.

In this case, when the gradation level of the video signal and the average value of the gradations respectively expressed by the first to fourth light emission patterns are different, the gradation level of the video signal and the average value of the gradations represented by the first to fourth light emission patterns respectively. Error is spread to the video signal spatially and / or temporally. This makes it possible to express the value of the gray level corresponding to the gray level of the video signal.

1 is a block diagram showing the configuration of a plasma display device according to a first embodiment of the present invention;

FIG. 2 is a diagram for explaining an ADS method applied to the plasma display device shown in FIG. 1;

3 is a schematic diagram showing an example of a light emission pattern of a plurality of subfields of four pixels in each region based on a dither table of a dither value generator;

4A to 4E are explanatory diagrams showing a light emission pattern table included in a dither table and a subfield converter having a dither value generator;

Fig. 5 (a) shows the contrast of each pixel recognized when the human eye does not move, and Fig. 5 (b) shows the angle recognized when the human eye moves in the direction of the arrow (left to right). An explanatory diagram showing the contrast of the pixels,

6 is a block diagram showing the configuration of the error diffusion device shown in FIG. 1;

7 (a) shows the spatial spread of the error, Figure 7 (b) shows the temporal spread of the error,

8A to 8E are explanatory diagrams showing another example of the light emission pattern table included in the dither table and the subfield conversion unit of the dither value generator;

9 is a block diagram showing the structure of a plasma display device according to a second embodiment of the present invention;

10A to 10E are explanatory diagrams showing a light emission pattern table included in a dither table and a subfield converter of the second dither value generator;

FIG. 11 is a schematic diagram for explaining pseudo contour noise visually recognized when a human eye moves over different pixels. FIG.

To practice the invention  Best form for

In the following embodiments, a case where the present invention is applied to a plasma display device having a plasma display panel (PDP) as an example of a display device will be described. The PDP is composed of a plurality of areas each including four pixels adjacent to each other in up, down, left and right.

In addition, below, although monochrome display using one color is demonstrated for simplicity of description, this invention is similarly applied also to the color display using three colors of R (red), G (green), and B (blue). can do.

In the plasma display device of the present embodiment, the gray level of the input video signal is expressed by the average value of the gray level values displayed by four pixels adjacent to each other up, down, left, and right in each region of the PDP.

(Example 1)

1 is a block diagram showing the configuration of a plasma display device according to a first embodiment of the present invention.

The plasma display device of FIG. 1 includes an A / D converter (analog / digital converter) 100, a scan number converter 200, an error diffusion device 300, a coefficient adder 310, and a dither value generator 320. ), A subfield converter 400, a discharge control timing generation circuit 500, a PDP (plasma display panel) 600, a data driver 700, a scan driver 800, and a sustain driver 900.

The video signal VS is input to the A / D converter 100. In addition, the discharge control timing generation circuit 500, the A / D converter 100, the scan rate converter 200, the error diffusion device 300, the coefficient adder 310, the dither value generator 320, and the subfield conversion The horizontal synchronization signal H and the vertical synchronization signal V are applied to the unit 400.

The A / D converter 100 converts the video signal VS into digital image data VD, and applies the image data VD to the scan rate converter 200. FIG.

The scan rate converter 200 converts the image data VD into image data of the number of lines corresponding to the number of pixels of the PDP 600, and applies the image data of each line to the error diffusion device 300. The image data of each line consists of a plurality of image data respectively corresponding to the plurality of pixels of each line.

The error diffusion device 300 spreads spatially and temporally the following error output from the dither value generator 320 to be described later. Details will be described later. The image data VV obtained by the error diffusion device 300 is applied to the coefficient adder 310 and the dither value generator 320. The value of the image data VV represents the gradation level of the corresponding pixel.

The dither value generator 320 stores a dither table indicating a relationship between a plurality of gradation levels represented by the image data VV and a plurality of dither values, and further dither values corresponding to the gradation levels of the image data VV from the dither table. Is read and applied to the coefficient adder 310. Here, the dither value corresponds to the difference between the gradation level and the gradation value displayed by each pixel.

The coefficient adder 310 adds the dither value applied by the dither value generator 320 to the image data VV applied by the error diffusion device 300, and adds the addition result as the image data VV1 to the subfield converter 400. ) Is applied.

The image data VV1 represents the value of the gradation displayed by each of the four pixels in each area.

The subfield conversion unit 400 stores a light emission pattern table indicating a relationship between the gray level values displayed by the four pixels of each region and the light emission patterns of the plurality of subfields, and is further based on this light emission pattern table. The image data VV1 is converted into serial data SD corresponding to the plurality of subfields, and the serial data SD is applied to the data driver 700.

The discharge control timing generation circuit 500 generates the discharge control timing signals SC and SU based on the horizontal synchronization signal H and the vertical synchronization signal V. The discharge control timing generation circuit 500 applies the discharge control timing signal SC to the scan driver 800, and applies the discharge control timing signal SU to the sustain driver 900.

The PDP 600 includes a plurality of data electrodes 50, a plurality of scan electrodes 60, and a plurality of sustain electrodes 70. The plurality of data electrodes 50 are arranged in the vertical direction of the screen, and the plurality of scan electrodes 60 and the plurality of sustain electrodes 70 are arranged in the horizontal direction of the screen. The plurality of sustain electrodes 70 are connected in common.

Discharge cells are formed at each intersection of the data electrode 50, the scan electrode 60, and the sustain electrode 70, and each discharge cell constitutes a pixel on the screen.

The data driver 700 converts serial data SD applied from the subfield converter 400 into parallel data, and selectively applies a write pulse to the plurality of data electrodes 50 based on the parallel data.

The scan driver 800 drives each scan electrode 60 based on the discharge control timing signal SC applied from the discharge control timing generation circuit 500. The sustain driver 900 drives the sustain electrode 70 based on the discharge control timing signal SU applied from the discharge control timing generation circuit 500.

In the plasma display device shown in Fig. 1, an ADS (Address Display-Period Separation) method is used as the gradation display driving method.

FIG. 2 is a diagram for explaining an ADS method applied to the plasma display device shown in FIG. 1. In addition, although FIG. 2 shows the example of the negative pulse which discharges at the time of a drive pulse fall, even in the case of the positive pulse which discharges at the time of a rise, basic operation | movement is as follows. In addition, in FIG. 2, for the sake of simplicity, one field includes five subfields SF1 to SF5.

In the ADS system, one field is divided in time into a plurality of subfields. In the example of FIG. 2, one field is divided into five subfields SF1 to SF5. Each subfield SF1 to SF5 is divided into an initialization period R1 to R5, a recording period AD1 to AD5, a sustain period SUS1 to SUS5, and an erase period RS1 to RS5. Initialization processing of each subfield is executed in the initialization periods R1 to R5, address discharge for selecting the discharge cells to be lit in the recording periods AD1 to AD5, and sustain discharge for display is performed in the sustain periods SUS1 to SUS5. .

In the initialization periods R1 to R5, a single initialization pulse is applied to the sustain electrode 70, and a single initialization pulse is applied to the scan electrode 60, respectively. Thereby, preliminary discharge is performed.

In the write periods AD1 to AD5, the scan electrodes 60 are sequentially scanned, and predetermined write processing is performed only on the discharge cells that have received the write pulses from the data electrodes 50. As a result, address discharge is performed.

In the sustain periods SUS1 to SUS5, the sustain pulses corresponding to the values superimposed on the respective subfields SF1 to SF5 are output to the sustain electrode 70 and the scan electrode 60. For example, in the subfield SF1, a sustain pulse is applied to the sustain electrode 70 once, and a sustain pulse is applied to the scan electrode 60 once, so that the discharge cells selected in the writing period AD1 execute two sustain discharges. do. In the subfield SF2, the sustain pulse is applied twice to the sustain electrode 70, the sustain pulse is applied twice to the scan electrode 60, and the discharge cells selected in the writing period AD2 execute the sustain discharge four times.

As described above, in each of the subfields SF1 to SF5, sustain pulses are applied to the sustain electrode 70 and the scan electrode 60 once, twice, four times, eight times, and sixteen times, and the brightness according to the number of pulses ( Brightness of the discharge cells. In other words, the sustain periods SUS1 to SUS5 are periods during which the discharge cells selected in the recording periods AD1 to AD5 discharge at a number of times corresponding to the overlapping amount of brightness.

3 is a schematic diagram showing an example of light emission patterns of a plurality of subfields of four pixels in each region based on the dither table of the dither value generator 320. In the following example, one field is divided into ten subfields.

In FIG. 3, white circles represent light emitting subfields, black circles represent non-light emitting subfields, and the plurality of subfields are called SF1 to SF10 in the order of the smallest overlap amount. In addition, the columns A, B, C,... Represents column numbers of the pixels in the horizontal direction, and rows 1, 2, 3,... Indicates the row number of the pixel in the vertical direction. The area of the PDP 600 is R1, R2, R3, R4,... It is called.

The subfields SF1 to SF10 are used to express the gray level value of one pixel. For example, the overlap amounts of the subfields SF1 to SF10 are "1", "2", "4", "8", "16", "32", "64", "128", and "256", respectively. And "512".

Here, gradation display by four pixels arranged in the column A row 1, the column B row 1, the column A row 2, and the column B row 2 in the region R1 will be described. The gradation level to be displayed by the four pixels of the area R1 is set to "959", respectively.

In addition, the pixel in column B row 2 (lower right) is the first pixel P1, the pixel in column A row 1 (upper left) is the second pixel P2, and the pixel in column A row 2 (lower left) is deleted. The pixel in the column B row 1 (upper right) is referred to as the third pixel P3, and the fourth pixel P4.

The light emission pattern of the first pixel P1 is " 1110111011 (1 indicates light emission and 0 indicates non-emission) " from subfield SF1 to subfield SF10 in order to express a gray scale value of " 887 " in one field. .

The light emission pattern of the second pixel P2 is " 1101110111 " in order from the subfield SF1 to the subfield SF10, and expresses the grayscale value of "955" in one field.

The light emission pattern of the third pixel P3 is " 1011101111 " in order from subfield SF1 to subfield SF10, and expresses a gray scale value of " 989 " in one field.

The light emission pattern of the fourth pixel P4 is " 0111011111 " in order from subfield SF1 to subfield SF10, and expresses a gray scale value of " 1006 " in one field.

The average value of the gradation value displayed by said 1st-4th pixel P1-P4 becomes "959.25" calculated from (955 + 1006 + 989 + 887) / 4.

In the present embodiment, for example, "1101", "0111", "1011" and "1110" are set so that the light emission patterns of the subfields SF5 to SF8 of the first to fourth pixels P1 to P4 are different. It is set.

In addition, in the present embodiment, the light emission patterns of the subfields SF5 to SF8 of the first to fourth pixels P1 to P4 are set to be different from each other, but the present invention is not limited thereto, and any of the first to fourth pixels P1 to P4 may be used. The light emission patterns of the nth to mth subfields may be set to be different from each other. Here, m and n are positive integers smaller than the total number of subfields, where m> n.

Here, "959" which is the gradation level to be displayed by each of the first to fourth pixels P1 to P4, and the first to fourth pixels P1 to P4 actually expressed by the light emission pattern of the subfields SF1 to SF10, respectively. The difference from "959.25" which is the average value of the gray scale value is "-0.25".

The dither value generator 320 outputs the difference of "-0.25" to the error diffusion device 300 as the error of each of the first to fourth pixels P1 to P4. The error diffusion device 300 spreads this error spatially and temporally. The configuration of the error diffusion device 300 and the error diffusion method will be described later.

As described above, in the present embodiment, the light emission patterns of the nth to mth subfields in the first to fourth pixels P1 to P4 are different (condition 1).

In the present embodiment, among the first to fourth pixels P1 to P4 adjacent to each other in the region of the PDP 600, the first pixel P1 and the second pixel P2 disposed at one diagonal position The value of the gray level displayed respectively is lower than the average value of the value of the gray level displayed by said 1st-4th pixel P1-P4, and is based on the 3rd pixel P3 and the 4th pixel P4 arrange | positioned at the other diagonal position. The value of the gradation displayed respectively is higher than the average value of the value of the gradation displayed by said 1st-4th pixel P1-P4 (condition 2).

Further, in the present embodiment, the light emission patterns of the subfields SF5 to SF8 in the first pixel P1, the second pixel P2, the third pixel P3 and the fourth pixel P4 are set to be different (bold in FIGS. 4A to 4D). Line)), but the present invention is not limited thereto, and the light emission patterns of arbitrary n-mth subfields in the first to fourth pixels P1 to P4 may be set to be different.

The first to fourth pixel P1 is formed by the combination pattern of light emission and non-emission light emitted from the n-th mth subfield among the plurality of subfields being different from each other between the light emission patterns of the first to fourth pixels P1 to P4. The value of the gradation expressed based on the light emission pattern of ˜P4 is different.

In addition, by using a subfield in which pseudo contour noise is unlikely to occur as an arbitrary n-m th subfield, pseudo contour noise can be suppressed.

4A to 4E are explanatory diagrams showing a light emission pattern table included in the dither table included in the dither value generator 320 and the subfield converter 400.

The relationship between the gradation level and the first to fourth dither values in FIGS. 4A to 4D and the gradation level and the error in FIG. 4E is included in the dither table included in the dither value generator 320. The dither value generator 320 determines whether the image data VV corresponds to any one of the first to fourth pixels P1 to P4 based on the horizontal synchronizing signal H and the vertical synchronizing signal V, and selects a dither value corresponding to this pixel. do.

In addition, the relationship between the values of the first to fourth gray levels and the first to fourth light emission patterns in FIGS. 4A to 4D is included in the light emission pattern table included in the subfield conversion unit 400. 4A indicates the gray level of the first pixel P1, the gray level shown in FIG. 4B indicates the gray level of the second pixel P2, and the gray level shown in FIG. 4C indicates the gray level of the third pixel P3. 4D indicates the gray level of the fourth pixel P4.

Here, for example, the gradation display by the first pixel P1 when the gradation level of the image data VV corresponding to the first pixel P1 is "959" will be described.

As shown in FIG. 4A, when the image data VV of the gradation level "959" is input to the dither value generator 320, the dither value generator 320 counts the first dither value "-72" based on the dither table. Output to the adder 310.

The coefficient adder 310 adds the first dither value " -72 " and the gradation level " 959 " of the image data VV, and converts the image data VV1 having the first gradation value " 887 " To 400).

The subfield converter 400 reads the first light emission pattern "1110111011" corresponding to the value "887" of the first gray scale of the image data VV1 from the light emission pattern table in Fig. 4A, and converts it into serial data SD. Based on the serial data SD, the data driver 700 drives the data electrode 50 corresponding to the first pixel P1 of the PDP 600.

The same gradation display is also performed for the second pixel P2, the third pixel P3, and the fourth pixel P4.

Further, the dither value generator 320 reads the error "-0.25" corresponding to the gradation level "959" of the input image data VV from the dither table of FIG. 4E and outputs it to the error diffusion device 300. That is, the dither value generator 320 spreads the error "-0.25" which is the difference between the gradation level "959" and the average value "959.25" of the values of the first to fourth gray levels of the first to fourth pixels P1 to P4 as an error. Output to device 300.

Next, based on the light emission pattern satisfying the condition 1 and condition 2 of the first to fourth pixels P1 to P4 of each region of the PDP 600, the first to fourth pixels P1 to P4 are emitted or non-emitted. The method for reducing pseudo contour noise by explaining the above description will be described. In addition, pseudo contour noise occurs when the gradation level of adjacent pixels is the same or approximate.

5 (a) is an explanatory diagram showing the contrast of each pixel recognized when the human eye does not move, and FIG. 5 (b) is a case where the human eye moves in the direction of the arrow (from left to right). It is explanatory drawing which shows the contrast of each pixel recognized.

5 (a) and 5 (b), the pixel indicated by "bright" displays a value of the gradation higher than the average value of the gradation value displayed by the first to fourth pixels P1 to P4 in each region. The pixel shown as "dark" is a pixel which displays the value of the gradation lower than the average value of the gradation value displayed by the 1st-4th pixel P1-P4 in each area | region.

As shown in FIG. 5A, the grayscale values of the first pixel P1 and the second pixel P2 of the respective regions R1, R2, R3, and R4 of the PDP 600 are determined by the first to fourth pixels P1 to P4. It is set lower than the average value of the gradation value, and the value of the gradation of the 3rd pixel P3 and the 4th pixel P4 is set higher than the average value of the gradation value of the 1st-4th pixel P1-P4.

In particular, in this embodiment, each area R1, R2, R3, R4,... Of the PDP 600 is provided. The values of the pixels of the first pixel P1, the second pixel P2, the third pixel P3, and the fourth pixel P4 are p1, p2, p3, and p4, respectively, and the grayscale values of the first to fourth pixels P1 to P4 are used. If the average value is pa, the gray scale values of the first to fourth pixels P1 to P4 are set so that the following relationship is established.

p1 <p2 <pa <p3 <p4 ‥‥ (1)

All areas of the PDP 600 have a relationship of the above formula (1).

As shown in Fig. 5B, when the human eye moves in the direction of the arrow, the gradation of the first pixel P1 and the second pixel P2 in each of the regions R1, R2, R3, and R4 of the PDP 600 is shown. The value of is recognized to be higher than the average value of the gray scale values of the first to fourth pixels P1 to P4, and the gray scale values of the third and fourth pixels P3 and P4 are the gray scales of the first to fourth pixels P1 to P4. It is recognized lower than the mean value of.

As described above, although the relationship between the gray level values of the adjacent pixels is reversed by the movement of the eye, the change of the gray level value of the second pixel P2 and the change of the gray level value of the third pixel P3 disappear from each other, and the first pixel is eliminated. The change in the value of the gray level of P1 and the change in the value of the gray level of the fourth pixel P4 disappear from each other. As a result, the change in the value of the recognized pixel is not recognized as pseudo contour noise.

In addition, when the human eye moves from the second pixel P2 toward the first pixel P1 (upper left to lower right), each area R1, R2, R3, R4,... The relationship between the value of the gray level of the first pixel P1 and the value of the gray level of the second pixel P2 is recognized to be reversed, and the relationship between the value of the gray level of the third pixel P3 and the value of the gray level of the fourth pixel P4 is reversed. It is recognized.

As described above, the relationship between the gray level values of pixels adjacent to the diagonal direction is reversed by the movement of the eye in the diagonal direction, but the change of the gray level values of the second pixel P2 and the first pixel P1 and the third pixel P3 and The change of the gray level value of the fourth pixel P4 disappears from each other. As a result, the change in the value of the recognized pixel is not recognized as pseudo contour noise.

In addition, not only when the line of sight moves in the direction of the arrow, but also in the direction opposite to the direction of the arrow (from right to left) and from the second and fourth pixels P2 and P4 to the third and first pixels P3 and P1. Direction (downward direction) and vice versa (upward direction), the direction from the first pixel P1 to the second pixel P2 (upper left to upper left) and the direction from the fourth pixel P4 to the third pixel P3 (from upper right) Even when the line of sight moves in the lower left) and vice versa (lower left to upper right), the change in the value of the recognized pixel is not recognized as pseudo contour noise.

As a result, pseudo contour noise can be reduced without degrading the image quality.

In addition, since the human eye recognizes the gray level value in the area constituted by the first to fourth pixels P1 to P4, the human eye is caused by a characteristic stripe pattern or the like that can be seen when it is concentrated in a part having similar contour noise. Deterioration of image quality is prevented.

In the above example, the case where the gradation level of the image data VV corresponding to the first to fourth pixels P1 to P4 in each area is the same, but the gradation of the image data VV corresponding to the first to fourth pixels P1 to P4 is shown. The level is not limited to the same. Even when the gradation levels of the image data VV corresponding to the first to fourth pixels P1 to P4 in each area are different, when they have adjacent gradation levels (the difference in gradation levels is 1 or 2, etc.), the above formula (1) Luminous pattern table is set so that the relationship of? In addition, when the gradation level of the image data VV corresponding to the 1st-4th pixel P1-P4 in each area | region differs significantly, the relationship of said Formula (1) does not hold. However, when the gradation level to be displayed by the pixels of the first to fourth pixels P1 to P4 in each area is greatly different, there is no problem because pseudo contour noise does not occur.

In the present embodiment, the first pixel P1 and the second pixel P2 in each region are referred to as pixels which display a value of gray scale lower than the average value of the gray scale values displayed by the first to fourth pixels P1 to P4. Although the 3rd pixel P3 and the 4th pixel P4 in each area | region are made into the pixel which displays the value of the gradation higher than the average value of the value of the gradation displayed by the 1st-4th pixel P1-P4, it is not limited to this. The first pixel P1 and the second pixel P2 in each area are pixels that display a value of gray level higher than the average value of the gray level values displayed by the first to fourth pixels P1 to P4, and the third pixel in each area. The pixel P3 and the fourth pixel P4 may be pixels that display a value of a gradation lower than an average value of the values of the gradations displayed by the first to fourth pixels P1 to P4.

Next, the error diffusion device 300 that spatially and temporally spreads the error e1 output from the dither value generator 320 will be described.

FIG. 6 is a block diagram showing the configuration of the error diffusion device 300 shown in FIG. 1.

As shown in FIG. 6, the error diffusion device 300 includes adders 11 and 12, multipliers 13 to 16, an interfield delay 5, and an intrafield delay 6. The intrafield delay 6 includes delays 61-64.

The error e1 output from the dither value generator 320 is input to the interfield retarder 5. The interfield delay unit 5 outputs the error e1 to the adder 12 by delaying the period (1V) of one field.

The error e1 is input to the delays 61 to 64 in the intrafield delay 6, respectively.

The delay unit 61 delays the error e1 by the period 1T of one pixel and outputs the result to the multiplier 13. The delay 62 outputs the error e1 to the multiplier 14 by delaying the error e1 by one pixel longer than the one line (1H + 1T). The delay unit 63 delays the error e1 by the period 1H of one line and outputs the result to the multiplier 15. The delay unit 64 outputs the error e1 to the multiplier 16 by delaying the error e1 by one pixel shorter period (1H-1T) than one line.

The multiplier 13 multiplies the error e1 output from the delayer 61 by a predetermined coefficient K1 and outputs it to the adder 12. The multiplier 14 multiplies the error e1 output from the delayer 62 by the predetermined coefficient K2 and outputs it to the adder 12. The multiplier 15 multiplies the error e1 output from the delayer 63 by the predetermined coefficient K3 and outputs it to the adder 12. The multiplier 16 multiplies the error e1 output from the delay unit 64 by a predetermined coefficient K4 and outputs it to the adder 12.

Here, each coefficient K1, K2, K3, K4 is set to an appropriate value satisfying the relationship of K1 + K2 + K3 + K4 = 1. For example, 7/16, 1/16, 5/16, and 3/16 are used as coefficients K1 to K4, respectively.

The adder 12 adds the output of the interfield delayer 5 and the outputs of the multipliers 13 to 16, and outputs the addition result to the adder 11 as the final error component e2.

Then, the adder 11 adds the image data VD and the final error component e2 output from the adder 12, so that the final error component e2 is spread spatially and temporally.

In addition, in the present embodiment, the error e1 output from the dither value generator 320 is diffused to the video signal temporally and spatially. However, the present invention is not limited thereto, and the error e1 is distributed only to the image data VD only temporally or spatially. You may diffuse.

FIG. 7A is a diagram illustrating spatial diffusion of error e1, and FIG. 7B is a diagram illustrating temporal diffusion of error e1.

As shown in Fig. 7A, the error e1 of the pixel Px0 of interest is the pixel Px1 adjacent to the right side of the same line, the pixel Px2 below the right inclination in the lower line, the pixel Px3 adjacent to the lower side of the pixel Px0 and the left side. It is spatially diffused to the pixel Px4 below the slope.

The value of multiplying the coefficient K1 by the error e1 is diffused into the pixel Px1, the value of multiplying the coefficient K2 by the error e1 is diffused into the pixel Px2, and the value of multiplying the coefficient K3 by the error e1 into the pixel Px3. The furnace is spread with a value obtained by multiplying the error e1 by the coefficient K4.

By the error diffusion process, when the average value of the gradation level of the image data VD and the gradation value respectively expressed by the 1st-4th light emission patterns differs, the value of the gradation corresponding to the gradation level of the image data VD is represented. It becomes possible.

As shown in FIG. 7B, the error e1 of the pixel Px0 of interest is spread in time to the pixel Px6 having the same coordinates as the pixel Px0 of interest in the next field.

In addition, although the gradation level of the image data VD corresponding to 1st-4th pixel P1-P4 is not limited, for example, when determining the error corresponding to 1st pixel P1, 1st-4th It is assumed that the gradation level of the image data VD corresponding to the pixels P1 to P4 is equal, and an error, which is a difference between the gradation level and the average value of the gradation values represented by the first to fourth light emission patterns, is read from the dither table. .

Next, another example of the dither table included in the dither value generator 320 and the light emission pattern table included in the subfield converter 400 will be described.

8A to 8E are explanatory diagrams illustrating another example of the dither table included in the dither value generator 320 and the light emission pattern table included in the subfield converter 400.

The relationship between the gradation level and the first to fourth dither values in FIGS. 8A to 8D and the gradation level and the error in FIG. 8E is included in the dither table included in the dither value generator 320. The relationship between the values of the first to fourth gray levels and the first to fourth light emission patterns of FIGS. 8A to 8D is included in the light emission pattern table included in the subfield conversion unit 400. 8A indicates the gradation level of the first pixel P1, the gradation level shown in FIG. 8B indicates the gradation level of the second pixel P2, and the gradation level shown in FIG. 8C indicates the gradation level of the third pixel P3. The gradation level shown in FIG. 8D represents the gradation level of the fourth pixel P4.

8A to 8D, in the order of decreasing the overlap amount from the subfield SF10 having the maximum overlap amount to the subfield SF1 having the minimum overlap amount, the subfield having the largest overlap amount among the subfields in which the pixel emits light. The combination pattern of light emission and non-light emission up to a predetermined number of subfields is different from the first to fourth pixels P1 to P4, starting at (heading 3).

Hereinafter, the subfields in which the pixels emit light are called light emitting subfields, and the subfields in which the pixels do not emit light are called non-light emitting subfields.

In the present embodiment, the predetermined number of subfields includes four subfields, starting with the subfield having the largest overlapping amount among the light emitting subfields in the first to fourth light emitting patterns.

In this case, the combination pattern of light emission and non-emission of the four subfields in the first to fourth light emission patterns is selected from five patterns of "1110", "1101", "1011", "0111" and "1111". do.

For example, when the gradation level of the image data VV is "13", the subfields SF4 to SF1 satisfy the condition 3, as indicated by thick lines in Figs. 8A to 8D. The combined pattern of light emission and non-emission of the first pixel P1 that satisfies condition 3 is “1011” as shown in FIG. 8A, and the combination pattern of light emission and non-emission of the second pixel P2 that satisfies condition 3 is satisfied. As shown in FIG. 8B, "1101" is set, and the combination pattern of light emission and non-emission of the third pixel P3 that satisfies condition 3 is "1110", as shown in FIG. 8C, and the condition is The combination pattern of light emission and non-emission of the fourth pixel P4 that satisfies 3 becomes “1111” as shown in FIG. 8D.

As described above, in the order of decreasing the overlap amount from the subfield SF10 having the largest overlapping amount to the subfield SF1 having the minimum overlapping amount, the subfield having the largest overlapping amount among the subfields in which the pixel emits light is 4 as a head. The combined pattern of light emission and non-light emission in the two subfields is different from the first to fourth pixels P1 to P4. Pseudo contour noise caused by a combination pattern of emission and non-emission of subfields having a large overlapping amount produces a significant deterioration of image quality. Therefore, the effect of the reduction of pseudo contour noise increases because the combination pattern of light emission and non-light emission of the subfield which most affects the value of the gradation expressed is different.

In addition, since the light emission pattern is set only to a subfield having a large overlap amount where pseudo contour noise is likely to occur, the number of design steps is reduced.

In addition to the setting of the light emission pattern which satisfies condition 1 and condition 2 above, or the setting of the light emission pattern which satisfies condition 2 and condition 3 as well, the first to the second agents of FIGS. 4A to 4D and 8A to 8D. In two or more light emission patterns among the four light emission patterns, the combination pattern of light emission and non-light emission in a predetermined subfield may be the same between adjacent gray level levels (condition 4).

Hereinafter, setting of the light emission pattern which satisfy | fills condition 2, the condition 3, and the condition 4 as an example is demonstrated using FIGS. 8A-8D.

In the first to fourth light emission patterns of FIGS. 8A to 8D, for example, when expressing the gradation level "23" of the image data VV, the subfields SF5 to SF2 of the first to fourth light emission patterns are each " 0111 "," 1011 "," 1101 ", and" 1110 ".

When the gradation level "24" adjacent to the gradation level "23" is expressed, the subfields SF5 to SF2 of the first to fourth light emission patterns are "0111", "1011", "1110" and " 1111 ".

In this case, the subfields SF5 to SF2 of the first emission pattern and the subfield SF5 of the second emission pattern among the subfields SF5 to SF2 of the first to fourth emission patterns representing the gradation level "23" and the gradation level "24". ~ SF2 are the same respectively.

In this case, the dither value is changed by one or two between adjacent gradation levels. Therefore, the dither value between the pixels is smoothly changed in the pixels adjacent to the pixels having small gray level difference. As a result, it becomes possible to reduce the noise due to the pseudo contour noise and the dither pattern.

Thus, in two or more light emission patterns among the 1st-4th light emission patterns, image quality improves more because the combination pattern of light emission and non-emission in a predetermined subfield is the same between adjacent gradation levels, respectively.

In this embodiment, the PDP 600 corresponds to the display panel, the coefficient adder 310, the dither value generator 320, and the subfield converter 400 correspond to the gradation display unit, and the data driver 700 and the scan driver. The 800 and the sustain driver 900 correspond to the driving unit, and the error diffusion device 300 corresponds to the diffusion device.

Moreover, in each of the 1st-4th light emission patterns, you may set a light emission pattern so that the location where the non-light emission subfield may be interposed between light emission subfields may be small. As a result, pseudo contour noise is less likely to occur. For example, in the subfield having the smallest overlapping amount from the light emitting subfield having the largest overlapping amount, the number of non-light emitting subfields interposed between the light emitting subfields may be limited to two or less.

In the present embodiment, among the four pixels in each region, the value of the gray level of the first pixel P1 is minimum, and the value of the gray level of the second pixel P2 is next to the value of the gray level of the first pixel P1. Although the value of the gradation of the three pixels P3 is next to the value of the gradation of the second pixel P2, the value of the gradation of the fourth pixel P4 is maximum, but the value of the gradation of the fourth pixel P4 is minimum in the next field, and the third pixel So that the value of the gradation of P3 is next to the value of the gradation of the fourth pixel P4, the value of the gradation of the first pixel P1 is next to the value of the gradation of the third pixel P3, and the value of the gradation of the second pixel P2 is maximum. You may display gradation.

That is, the light emission pattern table may be set such that the values p1 to p4 and the average value pa of the gradations of the first to fourth pixels P1 to P4 alternately repeat the relationship of the following expressions (1) and (2) for each field.

p1 <p2 <pa <p3 <p4 ‥‥ (1)

p1> p2> pa> p3> p4 ‥‥ (2)

In this way, by performing gradation display so that the magnitude relationship of the gradation values of the first to fourth pixels P1 to P4 for each field is circulated, the magnitude relation of the gradation values of the first to fourth pixels P1 to P4 for each field is performed. Noise generated when the same is reduced is reduced.

In the present embodiment, the plasma display device is used as an example of the display device for performing gradation display by the subfield method. However, the present invention is not limited thereto, and other display devices such as a digital mirror device may be used.

(Example 2)

EMBODIMENT OF THE INVENTION Hereinafter, Example 2 of this invention is described. Fig. 9 is a block diagram showing the construction of a plasma display device in accordance with a second embodiment of the present invention.

As shown in Fig. 9, the plasma display device of the present embodiment differs from the plasma display device of the first embodiment in that the second coefficient adder 330, the second dither value generator 340, and the selector 350 are different. ) And a pseudo contour detector 360.

The discharge control timing generation circuit 500, the A / D converter 100, the scan rate converter 200, the error diffusion device 300, the first coefficient adder 310, the first dither value generator 320, and the first The horizontal synchronization signal H and the vertical synchronization signal V are applied to the two coefficient adder 330, the second dither value generator 340, the selector 350, the pseudo contour detector 360, and the subfield converter 400.

The error diffusion device 300 spreads the errors e2 and e3 output from the first dither value generator 320 or the second dither value generator 340 spatially and temporally.

The image data VV obtained by the error diffusion device 300 includes the first coefficient adder 310, the first dither value generator 320, the second coefficient adder 330, the second dither value generator 340, and the selector 350. Is applied. The value of the image data VV represents the gradation level of the corresponding pixel.

The first dither value generator 320 stores a dither table indicating a relationship between the plurality of gradation levels represented by the image data VV and the plurality of dither values, and further corresponds to the gradation levels of the image data VV from the dither table. The dither value is read and applied to the first coefficient adder 310. Here, the dither value corresponds to the difference between the gradation level and the gradation value displayed by each pixel.

The first coefficient adder 310 adds the dither value applied by the first dither value generator 320 to the image data VV applied by the error diffusion device 300, and selects the addition result as the image data VV1. 350). The image data VV1 represents the value of the gradation displayed by each of the four pixels in each area.

The second dither value generator 340 stores a dither table indicating a relationship between the plurality of gradation levels represented by the image data VV and the plurality of dither values, and further corresponds to the gradation level of the image data VV from the dither table. The dither value is read and applied to the second coefficient adder 330.

The second coefficient adder 330 adds the dither value applied by the second dither value generator 340 to the image data VV applied by the error diffusion device 300, and selects the addition result as the image data VV2. 350). The image data VV2 represents the value of the gradation displayed by each of the four pixels in each area.

The pseudo outline detector 360 detects the degree of occurrence of pseudo outline noise from the light emission pattern of the subfield as the information included in the image data VD, the amount of change in the gradation level, the speed of the image movement, the direction in which the image moves, and the like. The result is applied to the selector 350. In the present embodiment, the pseudo outline detector 360 is constituted by a motion amount detection circuit that detects the motion amount of the image.

The pseudo contour detector 360 is not limited to the motion detection circuit, and other circuits capable of detecting a value related to the degree of occurrence of pseudo contour noise may be used.

The selector 350 applies the image data VV applied from the error diffusion device 300, the image data VV1 applied from the first coefficient adder 310, and the second coefficient based on the detection result applied from the pseudo contour detector 360. Any one of the image data VV2 applied from the adder 330 is selected and applied to the subfield converter 400.

The subfield conversion unit 400 stores a light emission pattern table indicating a relationship between the gray level values displayed by the four pixels of each region and the light emission patterns of the plurality of subfields, and is further based on this light emission pattern table. One of the image data VV, VV1, and VV2 is converted into serial data SD corresponding to the plurality of subfields, and the serial data SD is applied to the data driver 700.

The light emission pattern table included in the dither table included in the first dither value generator 320 and the subfield converter 400 corresponding to the dither table is the same as the dither table and light emission pattern table shown in FIGS. 8A to 8E described above. .

Hereinafter, the dither table of the second dither value generator 340 and the light emission pattern table of the subfield converter 400 corresponding to the dither table will be described.

10A to 10E are explanatory diagrams showing a light emission pattern table included in the dither table included in the second dither value generator 340 and the subfield converter 400.

The relationship between the gradation level and the first to fourth dither values in FIGS. 10A to 10D and the gradation level and the error in FIG. 10E is included in the dither table included in the second dither value generator 340. The first dither value generator 320 and the second dither value generator 340 determine whether the image data VV corresponds to any one of the first to fourth pixels P1 to P4 based on the horizontal synchronizing signal H and the vertical synchronizing signal V. FIG. The dither value corresponding to this pixel is selected.

The relationship between the values of the first to fourth gray levels and the first to fourth light emission patterns of FIGS. 10A to 10D is included in the light emission pattern table included in the subfield conversion unit 400. 10A indicates the gray level of the first pixel P1, the gray level shown in FIG. 10B indicates the gray level of the second pixel P2, and the gray level shown in FIG. 10C indicates the gray level of the third pixel P3. And the gradation level shown in FIG. 10D indicates the gradation level of the fourth pixel P4.

When it is detected by the pseudo contour detector 360 that the generation degree of the pseudo contour noise is large, the image data VV1 of the first coefficient adder 320 is selected by the selector 350, and the generation degree of the pseudo contour noise is small. Is detected by the pseudo contour detector 360, the image data VV2 of the second coefficient adder 340 is selected by the selector 350. In addition, when it is detected by the pseudo contour detector 360 that no pseudo contour noise occurs at all, the image data VV of the error diffusion device 300 is selected by the selector 350.

In the present embodiment, a part of the combination pattern of light emission and non-light emission of the predetermined subfield of the first to fourth light emission patterns in the dither table included in the second dither value generator 340 is the same.

For example, the subfields SF5 to SF2 of the first to fourth light emission patterns corresponding to the gradation level "23" are "1010", "1011", "1011" and "1101", respectively, and the second and third light emission. The combined pattern of light emission and non-light emission in the subfields SF5 to SF2 of the pattern is the same.

Thereby, although the effect of reducing the pseudo contour noise is small compared with the case of using the 1st-4th light emission pattern in the dither table which the 1st dither value generator 320 has, the noise by a dither pattern can be reduced. Become.

As described above, in this embodiment, the image data VV, the image data VV1 output from the first coefficient adder 320 or the image data VV2 output from the second coefficient adder 340 are selectively used according to the degree of pseudo contour noise. Thus, pseudo contour noise can be reduced while minimizing noise caused by the dither pattern.

In the present embodiment, the first coefficient adder 310, the second coefficient adder 330, the first dither value generator 320, the second dither value generator 340, the selector 350, and the subfield converter 400 ) Corresponds to the gradation display unit, the pseudo outline detector 360 corresponds to the detection unit, the data driver 700, the scan driver 800 and the sustain driver 900 correspond to the driving unit, and the error diffusion device 300 It corresponds to a diffusion device.

Claims (12)

A display device for performing gradation display by a subfield method on the basis of a video signal having a gradation level, A display panel including a plurality of regions each including first to fourth pixels adjacent to upper and lower left and right, and The first to fourth tables each comprising a plurality of first to fourth light emission patterns corresponding to the first to fourth pixels are stored, and the first to fourth tables are based on the gradation level of the video signal. Select first to fourth light emission patterns corresponding to the first to fourth pixels of each area from each other, and based on the selected first to fourth light emission patterns, the first to fourth light emission patterns of each area of the display panel for each subfield. A gradation display section for performing gradation display by emitting or non-emitting the fourth pixel, Combination patterns of light emission and non-light emission in a predetermined subfield among the plurality of subfields are different from each other between the first to fourth light emission patterns, In each region, the first and second pixels are disposed at one diagonal position, the third and fourth pixels are disposed at the other diagonal position, At each gradation level, the value of the gradation represented by the first and second light emission patterns, respectively, is lower than the average value of the gradations represented by the first to fourth light emission patterns, respectively by the third and fourth light emission patterns. The value of the gradation expressed is higher than the average value Display device. The method of claim 1, The plurality of subfields have different overlap amounts, The predetermined subfield is leading the subfield having the largest overlapping amount among the subfields in which the pixel emits light in the order in which the overlapping amount decreases from the subfield having the largest overlapping amount to the subfield having the minimum overlapping amount. A predetermined number of subfields Display device. The method of claim 1, In the two or more light emission patterns of the first to fourth light emission patterns, the combination pattern in the predetermined subfield is the same between adjacent gray level levels, respectively. Display device. The method of claim 1, And a detecting section for detecting a degree of pseudo contour noise in the image displayed on the display panel, The gradation display section further stores fifth to eighth tables each including a plurality of fifth to eighth light emission patterns corresponding to the first to fourth pixels, and based on the detection result by the detection unit. Selecting one of the set of the first to fourth tables and the set of the fifth to eighth tables and selecting the set based on the gradation level of the video signal when the set of the fifth to eighth tables is selected Selecting fifth to eighth light emission patterns corresponding to the first to fourth pixels of each region from the fifth to eighth tables, and for each subfield based on the selected fifth to eighth light emission patterns Gray scale display is performed by emitting or non-emitting the first to fourth pixels of each region of A combination pattern of light emission and non-emission light in the predetermined subfield is the same as some of the fifth to eighth light emission patterns, At each gradation level, the value of the gradation represented by the fifth and sixth light emission patterns, respectively, is higher than the average value of the gradations represented by the fifth to eighth light emission patterns, and respectively by the seventh and eighth light emission patterns. The value of the gradation expressed is lower than the average value. Display device. The method of claim 1, The gradation display unit, A first difference between the respective gradation levels and the values of the gradations represented by the first to fourth light emitting patterns, respectively, as a first to fourth dither value, and further comprising a first corresponding to the gradation level of the video signal. A dither value generator for outputting a fourth dither value, A coefficient adder for respectively adding first to fourth dither values generated by the dither value generator to the gradation level of a video signal; The first to fourth tables are stored, and the first to fourth emission patterns are selected from the first to fourth tables based on the addition result of the coefficient adder, and the selected first to fourth emission patterns are selected. A driver configured to emit or not emit light of the first to fourth pixels of each area of the display panel based on each subfield; Display device including. The method of claim 1, When the gradation level of the video signal and the average value of the gradations represented by the first to fourth light emission patterns are different, the gradation level of the video signal and the average value of the gradations represented by the first to fourth light emission patterns, respectively; And a spreading device for diffusing an error of the signal into a video signal in a spatial and / or temporal manner. Display device. A display method for performing gradation display on a display panel by a subfield method based on a video signal having a gradation level, The display panel includes a plurality of areas each including first to fourth pixels adjacent to each other in the top, bottom, left, and right directions, and in each area, the first and second pixels are disposed at one diagonal position, and the third and The fourth pixel is disposed at the diagonal position on the other side, Storing first to fourth tables each comprising a plurality of first to fourth emission patterns corresponding to the first to fourth pixels; Selecting first to fourth light emission patterns corresponding to the first to fourth pixels of each area from the first to fourth tables based on the gray level of the image signal;  Performing gradation display by emitting or non-emitting first to fourth pixels of each area of the display panel for each subfield based on the selected first to fourth emission patterns And Combination patterns of light emission and non-light emission in a predetermined subfield among the plurality of subfields are different from each other between the first to fourth light emission patterns, At each gradation level, the value of the gradation represented by the first and second light emission patterns, respectively, is higher than the average value of the gradations represented by the first to fourth light emission patterns, respectively by the third and fourth light emission patterns. The value of the gradation expressed is lower than the average value. Display method. The method of claim 7, wherein The plurality of subfields have different overlap amounts, The predetermined subfield is leading the subfield having the largest overlapping amount among the subfields in which the pixel emits light in the order in which the overlapping amount decreases from the subfield having the largest overlapping amount to the subfield having the minimum overlapping amount. A predetermined number of subfields Display method. The method of claim 7, wherein 2. The display method according to claim 1, wherein the combination patterns in the predetermined subfields are the same between two or more emission patterns among the first to fourth emission patterns. The method of claim 7, wherein Detecting the degree of pseudo contour noise in the image displayed on the display panel; Further storing a fifth to eighth table each comprising a plurality of fifth to eighth light emission patterns corresponding to the first to fourth pixels; Selecting one of the set of the first to fourth tables and the set of the fifth to eighth tables based on a detection result of the degree of pseudo contour noise; Fifth to eighth corresponding to the first to fourth pixels of each region from the selected fifth to eighth tables based on the gradation level of the image signal when the set of the fifth to eighth tables is selected; Selecting an emission pattern, Performing gradation display by emitting or non-emitting first to fourth pixels of each area of the display panel for each subfield based on the selected fifth to eighth light emission patterns Further provided, A combination pattern of light emission and non-emission light in the predetermined subfield is the same as some of the fifth to eighth light emission patterns, In each of the gradation levels, the value of the gradation represented by the fifth and sixth light emission patterns, respectively, is lower than the average value of the gradation represented by the fifth to eighth light emission patterns, and is respectively represented by the seventh and eighth light emission patterns. The value of the gradation expressed is higher than the average value Display method. The method of claim 7, wherein The step of executing the gradation display includes storing the difference between each gradation level and the value of the gradation represented by the first to fourth light emitting patterns, respectively, as the first to fourth dither values; Outputting first to fourth dither values corresponding to the gradation level of the video signal; Adding first to fourth dither values generated to the gradation level of the video signal, respectively; Storing the first to fourth tables; Selecting first to fourth light emission patterns from the first to fourth tables based on the addition result; Emitting or not emitting light from the first to fourth pixels of each area of the display panel for each subfield based on the selected first to fourth light emitting patterns Display method comprising a. The method of claim 7, wherein When the gradation level of the video signal and the average value of the gradations represented by the first to fourth light emission patterns are different, the gradation level of the video signal and the average value of the gradations represented by the first to fourth light emission patterns, respectively; And spreading the error of the signal to the video signal in a spatial and / or temporal manner. Display method.