JP2002023692A - Display device and display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device and a display method in which fluctuation in the center of gravity of light emitting time is reduced while securing sufficient number of gradations and animation spurious profiles are reduced. SOLUTION: Low-order subfields SF1 to SF6 are weighted in accordance with their combination so that gradation levels are continuously changed. Moreover, high-order subfields SF7 to SF12 are weighted correspondingly to respective different gradation levels. The level difference between a non-used gradation level which easily generates animation spurious profiles and a used gradation level which hardly generates animation spurious profiles is diffused spatially and in time wise by a gradation converting/diffusing circuit 2 and the non-used gradation level is equivalently displayed by using the used gradation level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention divides one field into a plurality of subfields arranged on a time axis in a predetermined order, weights each subfield in correspondence with a gradation level, and applies a weight to a video signal. The present invention relates to a display device and a display method for performing gray scale display by causing pixels on a display panel to emit light or not to emit light for each subfield.

[0002]

2. Description of the Related Art A plasma display device using a plasma display panel has the advantage that it can be made thinner and larger. In this plasma display device, an image is displayed by utilizing light emission at the time of discharge of a discharge cell constituting a pixel. Further, since the plasma display panel emits light in a binary manner, a subfield method of displaying a halftone by temporally overlapping a plurality of weighted binary images is used.

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

When the above-described subfield method is used, since the viewer's line of sight follows the moving image, the temporal integration region of the eyes changes spatially, and the moving image is unique. False contour noise is observed. This contour is called pseudo contour noise (“pseudo contour noise seen in pulse width modulation moving image display”: Technical Report of the Institute of Television Engineers of Japan, Vo1.1)
9, No. 2, IDY95-21, pp. 61-66)
This causes image quality to deteriorate.

[0005] As a method of reducing the above-mentioned moving image false contour, there is a display method disclosed in Japanese Patent Application Laid-Open No. 10-31455, for example. FIG. 20 is a schematic diagram showing n subfields forming one field period in a conventional display device using this display method.

As shown in FIG. 20, one field is divided into n subfields, and each subfield has a substantially equal maintenance time (black portion in the figure). By setting the sub-fields indicated by black circles in the lower table of FIG. 20 among the n sub-fields thus divided into light emitting states, n gradations from 0 to n can be displayed. In this case, since the sustain periods of the subfields, that is, the weights are substantially equal, and the non-light emitting subfields are not arranged between the light emitting subfields, it is possible to reduce the moving image pseudo contour.

Further, as another method for reducing the false contour of a moving image, there is a display method disclosed in Japanese Patent Application Laid-Open No. 9-34399, for example. FIG. 21 is a schematic diagram showing a configuration of a subfield of a conventional display device using this display method.

[0008] As shown in FIG.
The weights of the subfields 6 to 12 corresponding to the upper 3 bits of the halftone represented by the binary number are set to 32, and the subfields 1 to 5 corresponding to the remaining lower 5 bits are set. Is weighted according to the binary system. In this case, in the subfields 6 to 12 for representing the upper 3 bits, the light emitting state is sequentially turned on in accordance with the increase in the gradation level, and the non-light emitting subfield is not arranged between the light emitting subfields. The contour can be reduced.

[0009]

However, in the former display method, the total number of gradations that can be expressed by a combination of subfields is very small, and when an intermediate gradation is to be displayed, the dither method or the error diffusion method is required. It is necessary to use a lot of diffusion processing based on the above-described method, and the resolution of an image is deteriorated.

In the latter display method, a gradation level at which a subfield having the same weight is carried from a combination of subfields in accordance with a binary number and a gradation level at which a subfield having the same weight is carried by one. In either case, the temporal center of gravity position of the subfield in the light emitting state greatly changes, and as a result, the temporal center of gravity of light emission also greatly changes. For this reason, a moving image pseudo contour is likely to be generated, and the moving image pseudo contour cannot be sufficiently reduced.

An object of the present invention is to provide a display device and a display method capable of reducing the temporal fluctuation of the center of gravity of light emission and reducing the false contour of a moving image while securing a sufficient number of gradations. It is.

[0012]

(1) First invention The display device according to the first invention divides one field into a plurality of subfields arranged on a time axis in a predetermined order, and A display device that performs grayscale display by weighting fields in correspondence with grayscale levels and emitting or not emitting pixels on the display panel for each subfield according to a video signal, wherein a plurality of subfields are ,
A plurality of lower sub-fields weighted so that the gradation level continuously changes by the combination, and each is weighted corresponding to a different gradation level,
Further, the combination of the plurality of gray levels is discontinuously changed, and a plurality of weights are set so as not to include the non-light emitting subfield between the light emitting subfields when displaying each gray level. A subfield associating means for converting an input one-field video signal into a video signal for each subfield, including an upper subfield, and a video signal for each subfield output from the subfield associating means. Light emitting means for emitting or not emitting light from the pixels on the display panel for each subfield.

In the display device according to the first aspect of the invention, the plurality of subfields are weighted so that the grayscale level is continuously changed by a combination of the plurality of subfields, and the plurality of lower subfields are respectively different in grayscale level. Weighted according to the level, and further includes a non-light emitting sub-field between the light emitting sub-fields when the gradation levels change discontinuously and the respective gray levels are displayed. And multiple high-order subfields that are weighted
A video signal of one field is converted into a video signal of each subfield, and pixels on the display panel are made to emit or not emit light for each subfield in accordance with the converted video signal of each subfield.

As described above, the upper subfields are weighted so as to correspond to mutually different gradation levels. Therefore, when the upper subfield becomes luminous due to an increase in the gradation level, the light emission state is changed. Since the temporal center of gravity of the subfield does not fluctuate greatly and the temporal fluctuation of the center of gravity of light emission decreases, it is possible to reduce the dynamic false contour. In addition, since the lower subfields are weighted so that the gradation level changes continuously depending on the combination, the total number of gradations with respect to the number of subfields can be made sufficiently large. As a result, it is possible to reduce the temporal fluctuation of the center of gravity of the light emission and reduce the moving image pseudo contour while securing a sufficient number of gradations.

(2) Second invention In a display device according to a second invention, in the configuration of the display device according to the first invention, a plurality of upper sub-fields are weighted in correspondence with a gradation level. The weights are arranged on the time axis such that the weights increase or decrease monotonically.

In this case, the upper sub-fields are arranged on the time axis such that the weight corresponding to the gradation level monotonically increases or monotonously decreases. When the light emitting device is in the light emitting state, it is possible to minimize the variation in the temporal center of gravity of the subfield in the light emitting state, and to minimize the variation in the temporal center of gravity of the light emission.

(3) Third invention The display device according to the third invention is the display device according to the first or second invention, in which the display device is configured from the maximum value of the weights weighted to the plurality of upper subfields. The value obtained by subtracting 1 is equal to or smaller than the total value of the weights assigned to the plurality of lower subfields.

In this case, the value obtained by subtracting 1 from the maximum value of the weights weighted to the plurality of upper sub-fields is set to be equal to or less than the total value of the weights weighted to the plurality of lower sub-fields. When the upper sub-field is in a light-emitting state due to a carry due to an increase in the tonal level, at least one lower sub-field is in a light-emitting state. Therefore, the fluctuation of the center of gravity of the sub-field in the light-emitting state is suppressed to a very small value. In addition, it is possible to make the fluctuation of the temporal center of gravity of the light emission very small.

(4) Fourth Invention A display device according to a fourth invention is the display device according to any one of the first to third inventions, wherein the display device includes a plurality of lower subfields and a plurality of upper subfields. The gradation levels that can be displayed by the combination are classified into a used gradation level that uses the gradation level as it is and an unused gradation level that does not use the gradation level as it is. In order to equivalently display the levels, the image processing apparatus further includes a diffusion unit that temporally and / or spatially diffuses a difference between the unused gradation level and the used gradation level.

In this case, the gradation levels that can be displayed by a combination of the plurality of lower subfields and the plurality of upper subfields are used gradation levels that use the gradation levels as they are, and non-use floors that do not use the gradation levels as they are. The difference between the unused gradation level and the used gradation level is temporally and / or spatially diffused, and the unused gradation level is equivalently displayed using the used gradation level. ing. Therefore, the used gradation level is limited to a gradation level based on a combination of subfields in which a moving image pseudo contour is unlikely to be generated, and a gradation level based on a combination of subfields in which a moving image pseudo contour is likely to be generated is set to an unused gradation level. This makes it possible to display all the gradation levels with the used gradation levels at which the moving image false contour is unlikely to occur. As a result, all the combinations of the used subfields are combinations of the subfields in which it is difficult to generate the moving image pseudo contour, and the generation of the moving image pseudo contour can be suppressed for all the gradation levels.

(5) Fifth Invention The display device according to the fifth invention is the display device according to the first or second invention, in which the display device is configured from the maximum value of the weights weighted to the plurality of upper subfields. The value obtained by subtracting 1 is larger than the total value of the weights weighted to the plurality of lower subfields, and the plurality of lower grayscale levels are displayed using display grayscale levels that can be displayed by a combination of the plurality of lower subfields and the upper subfields. The difference between the non-display gradation level and the display gradation level is temporally and / or spatially diffused in order to equivalently display the non-display gradation level that cannot be displayed by the combination of the subfield and the plurality of upper subfields. It further comprises a diffusion means.

In this case, the value obtained by subtracting 1 from the maximum value of the weights weighted to the plurality of upper subfields is made larger than the total value of the weights weighted to the plurality of lower subfields. The weight of the subfield can be reduced, and the difference between the weights of the lower subfields can be reduced. Therefore, the weight of the upper subfield arranged on the lower subfield side on the time axis among the upper subfields can be relatively reduced, so that the subfield which frequently emits light during gradation display is displayed. Can be reduced. As a result, the temporal fluctuation of the center of gravity of the subfield in the light emitting state can be suppressed, and the temporal fluctuation of the center of gravity of the light emission can be extremely reduced.

Further, the difference between the non-display gradation level and the display gradation level is temporally and / or spatially diffused, and the non-display gradation level is equivalently displayed using the display gradation level. Therefore, non-display gradation levels can be displayed, and the total number of gradations can be increased. In addition, when the display gradation level is a gradation level based on a combination of subfields in which a moving image pseudo contour is unlikely to occur, and the non-display gradation level is a gradation level based on a combination of subfields in which a moving image pseudo contour is likely to occur, the moving image Since all gradation levels can be displayed with display gradation levels in which pseudo contours are unlikely to occur, all combinations of sub-fields used are combinations of sub-fields in which pseudo contours are hardly generated, and all gradations are used. It is possible to suppress the generation of the moving image false contour with respect to the level.

(6) Sixth invention A display device according to a sixth invention is the display device according to the fifth invention, wherein the display gradation level is different from the use gradation level that uses the gradation level as it is. The gradation level is classified into an unused gradation level that is not used as it is, and the diffusion unit uses the used gradation level to display the unused gradation level equivalently using the used gradation level. The difference from the tonal level is temporally and / or spatially diffused.

In this case, the display gradation levels are classified into a use gradation level which uses the gradation level as it is and an unused gradation level which does not use the gradation level as it is. The difference from the gray level is temporally and / or spatially diffused, and the unused gray level is equivalently displayed using the used gray level. Therefore, the used gradation level is limited to a gradation level based on a combination of subfields in which a moving image pseudo contour is unlikely to be generated, and a gradation level based on a combination of subfields in which a moving image pseudo contour is likely to be generated is set to an unused gradation level. By doing
All gradation levels can be displayed by using gradation levels in which a moving image false contour is unlikely to occur. As a result, all subfield combinations that are used are less likely to produce video false contours,
The generation of the moving image pseudo contour can be suppressed for all gradation levels.

(7) Seventh invention A display device according to a seventh invention is the display device according to the fourth or sixth invention, wherein the used gradation level is determined when the gradation level is displayed. This is a gradation level that does not include the lower subfields that do not emit light between the lower subfields that emit light.

In this case, since the gradation level that does not include the lower sub-field that does not emit light between the lower sub-fields that emit light when displaying the gradation level is the used gradation level, the light emission state Only the gradation level in which all the lower sub-fields are continuous is actually used for gradation display. At such a gradation level,
When the gradation level changes, the number of light emitting subfields also changes stepwise, so that the temporal change in the center of gravity of the light emitting subfields is very small,
It is possible to perform gradation display using only a combination of subfields in which a moving image false contour is unlikely to occur.

(8) Eighth Invention In the display device according to the eighth invention, in the configuration of the display device according to the fourth or sixth invention, the used gradation level is determined when the gradation level is displayed. This is a gradation level that does not include two or more non-light emitting lower-order sub-fields between the light-emitting lower weight sub-field and the lighter weight lower weight sub-field.

In this case, when displaying the gradation level, there is a lower light emitting state between the lower sub-field having the highest light weight and the lower weight sub-field having the light emitting state. Subfield 2
Since a gradation level not containing more than one is a use gradation level, only a gradation level in which lower subfields in a light emitting state are substantially continuous is actually used for gradation display. At such a gradation level, when the gradation level changes, the number of light emitting subfields also changes almost stepwise, so that the temporal shift of the center of gravity of the light emitting subfield is reduced, and A gradation display can be performed using only a combination of subfields in which a pseudo contour is unlikely to be generated. Further, a gradation level including one lower subfield in a non-light emitting state between the lower subfield having the highest light weight in the light emitting state and the lower subfield having the lowest weight in the light emitting state is also used. Since the tone levels can be used, the number of tone levels that can be used as they are can be further increased.

(9) Ninth Invention A display device according to a ninth invention is the display device according to the fourth or sixth invention, wherein the used gradation level is the same as when the gradation level is displayed. This is a gradation level that does not include three or more lower sub-fields in a non-light emitting state between the lower sub-field in the light emitting state with the highest weight and the lower sub-field in the light emitting state with the lowest weight.

In this case, when displaying the gradation level, there is a lower light emitting state between the lower sub-field having the highest light weight and the lower weight sub-field having the light emitting state. 3 subfields
Since a gradation level not containing more than one is a use gradation level, only a gradation level in which lower subfields in a light emitting state are substantially continuous is actually used for gradation display. At such a gradation level, when the gradation level changes, the number of light emitting subfields also changes approximately stepwise, so that the temporal change in the center of gravity of the light emitting subfields is reduced, and A gradation display can be performed using only a combination of subfields in which a pseudo contour is unlikely to be generated. Also, a gradation level including one or two non-light emitting lower sub-fields between a light weight lower weight sub-field and a light weight lower weight sub-field. Can also be used gradation levels, so that the number of gradation levels that can be used as they are can be further increased.

(10) Tenth Invention In the display device according to the tenth invention, in the configuration of the display device according to any one of the seventh to ninth inventions, the lower sub-field in the non-light emitting state has a weight amount. Does not include the smallest lower subfield.

In this case, since the lower sub-field having the smallest weight is not included in the lower sub-field in the non-light emitting state, the used gradation is excluded except for the lower sub-field having the smaller weight and having the least effect on the moving image false contour. Levels can be set, and the number of gradation levels that can be used as they are can be increased without affecting the generation of moving image false contours.

(11) Eleventh invention In the display device according to the eleventh invention, in the configuration of the display device according to the tenth invention, the lower subfield in the non-light emitting state has the second lowest weight in the lower subfield. It does not include subfields.

In this case, the lower sub-field having the smallest weight and the second lower sub-field are not included in the lower sub-fields in the non-light emitting state.
The used gradation level can be set except for the lower sub-field, which has a small weight and has little effect on the moving picture pseudo contour, and the number of gradation levels that can be used as it is without substantially affecting the occurrence of the moving picture pseudo contour is determined. Can be increased more.

(12) Twelfth Invention In the display device according to the twelfth invention, in the configuration of the display device according to the eleventh invention, the lower subfield in the non-light emitting state has the lower third weight having the third smallest weight. It does not include subfields.

In this case, since the three lower sub-fields from the lowest sub-field to the third lowest sub-field having the smallest weight are not included in the lower sub-fields in the non-light emitting state, the moving picture having the smaller weight is used. The use gradation level can be set except for the lower sub-field that has little effect on the pseudo contour, and the number of gradation levels that can be used as it is without much affecting the generation of the moving picture pseudo contour is further increased. Can be.

(13) Thirteenth Invention The display device according to the thirteenth invention is the display device according to any one of the first to twelfth inventions, wherein the plurality of lower subfields and the plurality of upper subfields are different from each other. Are arranged on the time axis such that the weights weighted corresponding to the gradation levels monotonically increase or monotonically decrease, and the subfield associating means includes a plurality of lower sub-displays capable of displaying the same gradation level. When there are a plurality of combinations of fields, a video signal of one field is converted into a video signal of each subfield so that lower-level subfields having a smaller weight are preferentially combined to display the gradation level.

In this case, a plurality of lower sub-fields and a plurality of upper sub-fields are arranged on the time axis such that the weight amount weighted corresponding to the gradation level monotonically increases or monotonously decreases. When there are a plurality of combinations of a plurality of lower sub-fields that can display the same gradation level, by selecting the combination used preferentially from the lower sub-fields having a smaller weight, the temporal change of the sub-fields in the light emitting state can be achieved. The position of the center of gravity is gradually moved from the front to the back or from the back to the front of one field, so that the temporal fluctuation of the center of gravity of light emission can be made very small.

(14) Fourteenth Invention A display device according to a fourteenth invention is the display device according to any one of the first to thirteenth inventions, wherein a lower subfield group including a plurality of lower subfields and A plurality of upper subfield groups each including a plurality of upper subfields are set, and the subfield associating means includes:
A video signal of one field is converted into a video signal for each subfield so that a plurality of lower subfield groups and a plurality of upper subfield groups are combined to obtain a gradation level corresponding to the video signal.

In this case, for each field, a plurality of lower sub-fields consisting of a plurality of lower sub-fields and a plurality of upper sub-fields consisting of a plurality of upper sub-fields are respectively set, and a plurality of lower sub-fields and a plurality of upper The video signal of one field is converted into a video signal for each subfield so that the subfields are combined to have a gradation level corresponding to the video signal. Accordingly, when the display frequency becomes low and the display state in which flicker is conspicuous is obtained, the temporal center of gravity position of the sub-field in the light-emitting state is set to 2 within one field.
It is possible to gradually move from the front to the back or from the back to the front of one field with reference to more than one point. Accordingly, the period in which light emission is concentrated can be dispersed into two or more while suppressing temporal fluctuation of the center of gravity of light emission, so that a moving image pseudo contour can be suppressed and flicker can be suppressed. be able to.

(15) Fifteenth Invention The display method according to the fifteenth invention divides one field into a plurality of subfields arranged on the time axis in a predetermined order, and converts each subfield to a gradation level. This is a display method in which gradation is displayed by making the pixels on the display panel emit or not emit light for each subfield according to the video signal in accordance with the video signal. Multiple lower subfields that are weighted so that their levels change continuously,
Each of them is weighted in correspondence with a different gray level, and furthermore, the gray level is discontinuously changed by the combination, and the non-light emitting state is set between the sub-fields that emit light when displaying each gray level. Converting a video signal of one input field into a video signal of each sub-field including a plurality of upper sub-fields weighted so as not to include the sub-fields, Causing the pixels on the display panel to emit or not emit light for each subfield in response to a signal.

In the display method according to the fifteenth aspect,
A plurality of subfields are weighted so as to correspond to different grayscale levels, and a plurality of lower subfields weighted so that the grayscale level continuously changes according to the combination. It comprises a plurality of upper subfields weighted so that the gray level varies discontinuously and the non-light emitting subfields are not included between the light emitting subfields when each gray level is displayed. Then, a video signal of one field is converted into a video signal of each subfield, and pixels on the display panel are illuminated or non-illuminated for each subfield according to the converted video signal of each subfield.

As described above, the upper subfields are weighted so as to correspond to mutually different grayscale levels. Therefore, when the upper subfield becomes light emitting due to an increase in the gray level, the light emitting state is changed. Since the temporal center of gravity of the subfield does not fluctuate greatly and the temporal fluctuation of the center of gravity of light emission decreases, it is possible to reduce the dynamic false contour. In addition, since the lower subfields are weighted so that the gradation level changes continuously depending on the combination, the total number of gradations with respect to the number of subfields can be made sufficiently large. As a result, it is possible to reduce the temporal fluctuation of the center of gravity of the light emission and reduce the moving image pseudo contour while securing a sufficient number of gradations.

(16) Sixteenth Invention A display method according to a sixteenth invention is a display method according to the fifteenth invention, wherein the plurality of upper subfields are:
It is arranged on the time axis such that the weight amount weighted corresponding to the gradation level monotonically increases or monotonically decreases.

In this case, the upper subfields are arranged on the time axis such that the weight corresponding to the gradation level monotonically increases or monotonically decreases. When the light emitting device is in the light emitting state, it is possible to minimize the variation in the temporal center of gravity of the subfield in the light emitting state, and to minimize the variation in the temporal center of gravity of the light emission.

(17) Seventeenth Invention A display method according to a seventeenth invention is directed to the display method according to the fifteenth or sixteenth invention, in which the plurality of upper subfields are weighted from the maximum value. The value obtained by subtracting 1 is equal to or smaller than the total value of the weights assigned to the plurality of lower subfields.

In this case, the value obtained by subtracting 1 from the maximum value of the weights weighted to the plurality of upper subfields is set to be equal to or less than the total value of the weights weighted to the plurality of lower subfields. When the upper sub-field is in a light-emitting state due to a carry due to an increase in the tonal level, at least one lower sub-field is in a light-emitting state. Therefore, the fluctuation of the center of gravity of the sub-field in the light-emitting state is suppressed to a very small value. In addition, it is possible to make the fluctuation of the temporal center of gravity of the light emission very small.

(18) Eighteenth Invention The display method according to the eighteenth invention is directed to the display method according to any one of the fifteenth to seventeenth inventions, wherein the display method comprises a plurality of lower subfields and a plurality of upper subfields. The gradation levels that can be displayed by the combination are classified into a used gradation level that uses the gradation level as it is and an unused gradation level that does not use the gradation level as it is. The method may further include a step of temporally and / or spatially diffusing a difference between the unused gradation level and the used gradation level to display the levels equivalently.

In this case, the gradation levels that can be displayed by a combination of a plurality of lower subfields and a plurality of upper subfields are used gradation levels that use the gradation levels as they are and unused gradation levels that do not use the gradation levels as they are. The difference between the unused gradation level and the used gradation level is temporally and / or spatially diffused, and the unused gradation level is equivalently displayed using the used gradation level. ing. Therefore, the used gradation level is limited to a gradation level based on a combination of subfields in which a moving image pseudo contour is unlikely to be generated, and a gradation level based on a combination of subfields in which a moving image pseudo contour is likely to be generated is set to an unused gradation level. This makes it possible to display all the gradation levels with the used gradation levels at which the moving image false contour is unlikely to occur. As a result, all the combinations of the used subfields are combinations of the subfields in which it is difficult to generate the moving image pseudo contour, and the generation of the moving image pseudo contour can be suppressed for all the gradation levels.

(19) Nineteenth Invention A display method according to a nineteenth invention is directed to the display method according to the fifteenth or sixteenth invention, in which the plurality of upper subfields are weighted from the maximum value. The value obtained by subtracting 1 is larger than the total value of the weights weighted to the plurality of lower subfields, and the plurality of lower grayscale levels are displayed using display grayscale levels that can be displayed by a combination of the plurality of lower subfields and the upper subfields. The difference between the non-display gradation level and the display gradation level is temporally and / or spatially diffused in order to equivalently display the non-display gradation level that cannot be displayed by the combination of the subfield and the plurality of upper subfields. It further includes steps.

In this case, the value obtained by subtracting 1 from the maximum value of the weights weighted to the plurality of upper subfields is made larger than the total value of the weights weighted to the lower subfields. The weight of the subfield can be reduced, and the difference between the weights of the lower subfields can be reduced. Therefore, the weight of the upper subfield arranged on the lower subfield side on the time axis among the upper subfields can be relatively reduced, so that the subfield which frequently emits light during gradation display is displayed. Can be reduced. As a result, the temporal fluctuation of the center of gravity of the subfield in the light emitting state can be suppressed, and the temporal fluctuation of the center of gravity of the light emission can be extremely reduced.

Further, the difference between the non-display gradation level and the display gradation level is temporally and / or spatially diffused, and the non-display gradation level is equivalently displayed using the display gradation level. Therefore, non-display gradation levels can be displayed, and the total number of gradations can be increased. In addition, when the display gradation level is a gradation level based on a combination of subfields in which a moving image pseudo contour is unlikely to occur, and the non-display gradation level is a gradation level based on a combination of subfields in which a moving image pseudo contour is likely to occur, the moving image Since all gradation levels can be displayed with display gradation levels in which pseudo contours are unlikely to occur, all combinations of sub-fields used are combinations of sub-fields in which pseudo contours are hardly generated, and all gradations are used. It is possible to suppress the generation of the moving image false contour with respect to the level.

(20) Twentieth invention A display method according to a twentieth invention is the display method according to the nineteenth invention, wherein the display gradation level is different from the use gradation level that uses the gradation level as it is. The gradation level is classified into an unused gradation level that is not used as it is, and the diffusion step is performed by using the unused gradation level and the used gradation in order to equivalently display the unused gradation level using the used gradation level. And temporally and / or spatially diffusing the difference from the tonal level.

In this case, the display gradation levels are classified into a use gradation level that uses the gradation level as it is and an unused gradation level that does not use the gradation level as it is. The difference from the gray level is temporally and / or spatially diffused, and the unused gray level is equivalently displayed using the used gray level. Therefore, the used gradation level is limited to a gradation level based on a combination of subfields in which a moving image pseudo contour is unlikely to be generated, and a gradation level based on a combination of subfields in which a moving image pseudo contour is likely to be generated is set to an unused gradation level. By doing
All gradation levels can be displayed by using gradation levels in which a moving image false contour is unlikely to occur. As a result, all subfield combinations that are used are less likely to produce video false contours,
The generation of the moving image pseudo contour can be suppressed for all gradation levels.

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an AC plasma display device will be described as an example of a display device according to the present invention. FIG. 1 is a block diagram showing a configuration of a plasma display device according to one embodiment of the present invention. In addition,
In the following description, the case where the video signal directly corresponds to the luminance, that is, the gradation level, will be described. However, even when performing color display, the same effect can be obtained by performing the same processing for each color as follows. it can.

The plasma display device shown in FIG.
A / D (analog / digital) converter 1, gradation conversion / diffusion circuit 2, video signal-subfield associator 3, subfield processor 4, scan / sustain drive circuit 5, data drive circuit 6, plasma display It includes a panel 7 and a timing pulse generator 8.

The video signal VS is input to the A / D converter 1. The A / D converter 1 converts the analog video signal VS into digital image data VD and outputs the digital image data VD to the gradation conversion / diffusion circuit 2.

The timing pulse generator 8 outputs the video signal V
A predetermined timing signal TC based on the horizontal synchronization signal HC and vertical synchronization signal VC of S, a predetermined clock CLK, and the like.
Is generated and supplied to each unit in the apparatus as needed.

The gradation conversion / diffusion circuit 2 converts the gradation level of the input image data VD into a displayable gradation level by a combination of a lower subfield and an upper subfield, which will be described later. VV is output to the video signal-subfield correlator 3.

Video signal-subfield correlator 3
In order to divide one field into a plurality of sub-fields including a lower sub-field and an upper sub-field and display it, image data of each sub-field is created from image data of one field, and the sub-field processor 4
Output to

The subfield processor 4 determines the number of sustain pulses in the sustain period from the image data and the like for each subfield, outputs a data driver drive control signal to the data drive circuit 6, and outputs the scan driver drive control signal and The sustain driver drive control signal is output to the scan / sustain drive circuit 5.

The plasma display panel 7 includes a plurality of address electrodes (data electrodes), a plurality of scan electrodes (scan electrodes), and a plurality of sustain electrodes (sustain electrodes). The plurality of address electrodes are arranged in the vertical direction of the screen, and the plurality of scan electrodes and the plurality of sustain electrodes are arranged in the horizontal direction of the screen. The plurality of sustain electrodes are commonly connected. Address electrode,
A discharge cell is formed at each intersection of the scan electrode and the sustain electrode, and each discharge cell forms a pixel on the screen.

The data drive circuit 6 is connected to a plurality of address electrodes of the plasma display panel 7. The scan / sustain drive circuit 5 includes a plasma display panel 7
Are connected to a plurality of scan electrodes and sustain electrodes.

The data drive circuit 6 applies a write pulse to a corresponding address electrode of the plasma display panel 7 according to image data during a write period according to a data driver drive control signal.

In accordance with the scan driver drive control signal, the scan / sustain drive circuit 5 sequentially applies the write pulse to the plurality of scan electrodes while shifting the shift pulse in the vertical scanning direction during the write period. Thereby, an address discharge is performed in the corresponding discharge cell. Also,
The scan / sustain drive circuit 5 applies a periodic sustain pulse to a plurality of scan electrodes of the plasma display panel 7 during a sustain period in accordance with a scan driver drive control signal, and a plurality of sustain electrodes in accordance with a sustain driver drive control signal. , A sustain pulse 180 ° out of phase with respect to the sustain pulse of the scan electrode is simultaneously applied. As a result, a sustain discharge is performed in the corresponding discharge cell, and each pixel emits light or no light for each subfield.

As described above, in the plasma display device shown in FIG. 1, ADS (Ad
A dress display-period separation (address / display period separation) method is used. In the ADS method, one field is temporally divided into a plurality of subfields, and each subfield is divided into a setup period, a write period, a sustain period, and the like. An address discharge for selecting a discharge cell to be turned on in a period is performed, and a sustain discharge for display is performed in a sustain period.

Next, the gradation conversion / diffusion circuit 2 shown in FIG. 1 will be described in detail. FIG. 2 shows the gradation conversion /
FIG. 3 is a block diagram showing a configuration of a spreading circuit 2.

The gradation conversion / diffusion circuit 2 shown in FIG. 2 includes a gradation conversion table 21, an error diffusion circuit 22, and a dither circuit 41.

The gradation conversion table 21 includes a gradation level for use and a dither circuit 41 for directly using a gradation level which can be displayed by a combination of a plurality of upper and lower subfields among gradation levels of an input video signal. The dither gray level displayed by the dither diffusion processing is output as it is, and the error diffusion gray level displayed by the error diffusion processing of the error diffusion circuit 22 is converted into a use gray level and output.

That is, the gradation conversion table 21 includes a table storing information on the used gradation level and the non-used gradation level, etc., and converts the inputted gradation level into the used gradation level corresponding to the gradation level. Convert to Specifically, the gradation conversion table 21 includes, for example, FIG.
19, the contents of the used gradation level and the dither gradation level are described. In the example shown in FIG. 5, the case where the inputted gradation level is 7 and the inputted gradation level are In the case of 8 (gradation level by dither), it is output as it is, and when the input gradation level is 15, it is converted to 14 which is the nearest used gradation level and output.

Next, the error diffusion circuit 22 will be described in detail. The error diffusion circuit 22 includes adders 23 and 24, a subtractor 25, delay units 26 to 29, and multipliers 30 to 33.

The adder 23 receives the input image data VD
And the output of the adder 24, and the gradation conversion table 21
And to the subtractor 25. The subtractor 25 is the adder 2
3 is subtracted from the output of the gradation conversion table 21 and output to the delay units 26 to 29.

The delay unit 26 delays the input by one pixel (1T) and outputs it to the multiplier 30. The delay unit 27 delays the input by one line and one pixel (1H + 1T) and outputs the result to the multiplier 31. The delay unit 28 delays the input by one line (1H) and outputs it to the multiplier 32. Delay device 2
9 is output to the multiplier 33 after being delayed by one pixel (1H-1T) before one line.

The multiplier 30 multiplies the input by a predetermined coefficient K 1 and outputs the result to the adder 24. The multiplier 31 multiplies the input by a predetermined coefficient K2 and outputs the result to the adder 24. The multiplier 32 multiplies the input by a predetermined coefficient K3 and outputs the result to the adder 24. The multiplier 33 multiplies the input by a predetermined coefficient K4 and outputs the result to the adder 24. Here, each coefficient K1, K
2, K3 and K4 are set to appropriate values satisfying the relationship of K1 + K2 + K3 + K4 = 1, for example, coefficients K1 to K4
For example, 7/16, 1/16, 5/16, and 3/16 are used. The adder 24 adds the outputs of the multipliers 30 to 33 and outputs the result to the adder 23.

With the above configuration, the gradation conversion table 21
When the gradation level is converted in step (1), the converted gradation level is subtracted from the original gradation level of the image data VD by the subtractor 25, and a level difference e ′ is obtained. This level difference e 'is delayed by a predetermined time by each of the delay units 26 to 29, and is output by a predetermined coefficient K1 to K
After being multiplied by 4, they are added by an adder 24, and finally output as a diffusion error e.

That is, in the error diffusion circuit 22, the level difference e ′ between the original gradation level of the image data VD and the gradation level after conversion by the gradation conversion table 21 is as shown in FIG. Then, the gray level after being diffused from the pixel under processing (pixel e ′) to surrounding pixels (pixels K1 to K4) and converted by the gray level conversion table 21 with the original gray level of the pixel under processing Error diffusion processing for spatially diffusing the level difference e ′ from the level is performed. As shown in FIG. 3B, the diffusion error e for a certain pixel is obtained by summing the errors diffused from the pixels (K1 to K4) around the pixel (e). Can be

By performing the above-described error diffusion processing on the entire screen, the gradation levels to be displayed on the entire screen are preserved, and when the entire screen is viewed, the human eyes feel as if they were the luminance of the original pixels, ie, before conversion. It looks like it is displayed at the gradation level of. As a result, a high-quality image free of image roughness can be expressed.

Next, the dither circuit 41 will be described in detail. The dither circuit 41 includes a dither amount table 42, an adder 43, a subtractor 44, and a selection circuit 45.

The image data output from the gradation conversion table 21 is output to the dither amount table 42, the adder 43, and the subtractor 44. The dither amount table 42 stores, as a table, information for associating dither gradation levels and dither amounts shown in FIGS.

That is, when the gradation level output from the gradation conversion table 21 is a dither gradation level subjected to dither diffusion processing, the dither amount table 42 adds the dither amount used for the dither diffusion processing to the adder. When the gradation level outputted from the gradation conversion table 21 is not the gradation level at which the dither diffusion process is performed, that is, when the gradation level is the used gradation level, 0 is output as the dither amount. For example, in the example shown in FIG. 5, the dither amount table 42 outputs 0 as the dither amount when the gradation level is 7, and outputs 1 as the dither amount when the gradation level is 8.

The adder 43 receives the output of the gradation conversion table 21 and the output of the dither amount table 42, adds the two, and outputs the result to the selection circuit 45. The subtractor 44 receives the output of the gradation conversion table 21 and the output of the dither amount table 42, and outputs a value obtained by subtracting the output of the dither amount table 42 from the output of the gradation conversion table 21 to the selection circuit 45. The selection signal SC generated by the timing generator 8 is input to the selection circuit 45, and the output of the adder 43 and the output of the subtractor 44 are alternately switched at a predetermined timing, and the converted image data VV is output. .

With the above configuration, when the gradation level output from the gradation conversion table 21 is a dither gradation level for performing dither diffusion processing, the dither circuit 41 sets the dither gradation level to the dither gradation level. A dither diffusion process for expressing using a used gradation level obtained by diffusing by an amount is performed. Specifically, when the gradation level of the input image data is a dither gradation level, the dither circuit 41
Image data is generated for alternately displaying the used gradation level, which is separated from the gradation level by a dither amount before and after the dither amount, with one even field and one odd field.

In the above-mentioned dither diffusion processing, the addition and subtraction of the dither amount (diffusion amount) on the screen are performed, for example, such that the sum total becomes 0 between the even field and the odd field as shown in FIG. The dither amount is diffused to change the gradation level for each pixel. That is, in the even field or the odd field, the addition / subtraction of the dither amount is reversed between adjacent pixels in the vertical and horizontal directions, and the addition / subtraction of the dither amount is reversed at the same pixel position in the even field and the odd field. In the example shown in FIG. 4, for example, the case shown in FIG. 4A is an even field, and the case shown in FIG. 4B is an odd field.

In this way, the used gradation levels are averaged over time, and an intermediate gradation level can be expressed on the screen. For example, in the example shown in FIG. 5, when the gradation level is 16 and the dither amount is 2, the gradation level 14 (16-2) is displayed on one of the even or odd fields, and the gradation level 18 (16 + 2) on the other. ) Is displayed.

The resolution is degraded by temporally diffusing the difference between the original gradation level of the image data and the used gradation level actually used for display as a dither amount using the above-mentioned dither diffusion processing. Without this, the level difference can be temporally diffused for each pixel.

The spread of the dither amount in the dither spread processing is not particularly limited to the above example, and addition / subtraction may be performed for each line or may be performed for each predetermined area. As described above, the dither diffusion process not only performs temporal diffusion, but also performs spatial diffusion by spreading a dither amount between pixels using a predetermined dither pattern, similarly to the error diffusion process. You may.

Further, in the gradation conversion / diffusion circuit 2, a difference in gradation level is spatially and temporally diffused using an error diffusion circuit 22 for spatial diffusion and a dither circuit 41 for temporal diffusion. However, the diffusion process may be performed by only one of the spatial diffusion and the temporal diffusion.

In the present embodiment, the video signal-subfield associator 3 corresponds to the subfield associating means, and the subfield processor 4, the scanning / sustaining driving circuit 5 and the data driving circuit 6 correspond to the light emitting means. I do. Further, the gradation conversion / diffusion circuit 2 corresponds to a diffusion unit.

Next, a specific example of the subfield used in the present embodiment will be described in detail. 5 to 9
FIG. 2 is a diagram showing an example of gray scale display by a first subfield group used in the plasma display device shown in FIG. In each of the figures below, “1” in each subfield column at each gradation level indicates the lower and upper subfields of the light emitting state, and blank columns indicate the lower and upper subfields of the non-light emitting state. .

As shown in FIG. 5, the first subfield group is composed of 12 subfields of 6 lower subfields SF1 to SF6 and 6 upper subfields SF7 to SF12. The weights of the fields SF1 to SF12 are 1, 2, 4,
7, 12, 21, 30, 32, 34, 36, 37, 39
It is.

In this case, the lower subfields SF1 to SF
The sum of the weights of F6 is 37, the weight of the upper subfield SF12 having the largest weight among the upper subfields SF7 to SF12 is 39, and a value obtained by subtracting 1 from the weight of the upper subfield SF12. Is smaller than the total value of the weights of the six lower subfields SF1 to SF6.

The weight amount of each subfield corresponds to the light emission amount (luminance) when the subfield emits light. In this example, the subfields SF1 to SF12 are combined to basically provide the 0th to 255th floors. All gradation levels of the key can be expressed, and all gradation levels can be displayed only by a combination of subfields.

However, in this example, among the gradation levels that can be expressed by the lower and upper subfields SF1 to SF12, the gradation levels based on the combination of the subfields in which the dynamic false contour is likely to occur are not used for display. Only the gradation levels indicated by black circles in the column of gradation used for display in the figure are used for display, and the gradation levels are used gradation levels. Further, the gray level in which a black circle is attached in the column of dither by dither in the figure is the dither gray level subjected to dither diffusion processing by the dither circuit 41, and the numerical value described in the dither amount column Is the dither amount used for the dither diffusion processing.

The above-mentioned used gradation level and dither gradation level are gradation levels which are output without being converted by the gradation conversion table 21. Further, the gray level in which the black circles are not added to the columns of the gray scale used for display and the gray scale by dither is an error diffusion gray level displayed by the error diffusion process by the error diffusion circuit 22.
The error diffusion gray level and the dither gray level are the unused gray levels. In FIG. 5, for example, the gradation level 15 corresponds to the unused gradation level.

In this example, the lower subfield SF
In the case of 1 to SF6, the case where there are two or more lower sub-fields in the non-light emitting state between the light emitting sub-fields is defined as the gradation level at which the moving image false contour is likely to occur.

For example, the gradation level 8 is such that the lower subfield SF1 and the subfield SF4 emit light, but the subfield SF2 and the subfield SF3 continuously emit light, so that the gradation level is lower. It becomes an unused gradation level.

In this case, most of the lower sub-fields in the light emitting state are continuous, and even if the gray level changes, only the gray level in which the lower sub-fields in the light emitting state are almost continuous is actually displayed in the gray scale display. Will be used. At such a gradation level, when the gradation level changes, the number of light emitting subfields also changes almost stepwise, so that the temporal shift of the center of gravity of the light emitting subfield is reduced, and A gradation display can be performed using only a combination of subfields in which a pseudo contour is unlikely to be generated.

Further, a gradation level including one lower sub-field in a non-light emitting state between the lower sub-field in the light emitting state having the highest weight and the lower sub-field in the light emitting state having the lowest weight. Can also be used gradation levels, so that the number of gradation levels that can be used as they are can be further increased.

In this example, the least significant subfield S having the smallest weight is used as the non-light emitting subfield.
F1 is not considered. This is because the least significant subfield SF1 has the smallest weight, and is considered to have little effect on the moving image pseudo contour.

The lower sub-field not considered as a non-light emitting sub-field is not particularly limited to only the sub-field SF1 having the smallest weight, and the lower sub-field S1 having the second smallest weight is not considered.
F2 and the lower subfield SF having the third smallest weight
You may remove up to three.

The unused gradation level is not particularly limited to the above example, and a gradation level that does not include the lower sub-field in the non-light emitting state between the lower sub-fields in the light emitting state is regarded as the unused gradation level. Is also good. In this case, only the gradation level in which all the lower sub-fields in the light-emitting state are continuous is actually used for the gradation display. In such a gradation level, when the gradation level changes, the number of sub-fields in the light-emitting state is changed. Also, the temporal change of the center of gravity of the subfields in the light-emitting state is very small, and the gradation display can be performed using only the combination of the subfields in which the moving image pseudo contour is hardly generated. it can.

A gradation level that does not include three or more lower sub-fields in the non-light emitting state between lower sub-fields in the light emitting state may be used as the unused gradation level. In this case, only the gradation levels in which the lower sub-fields in the light-emitting state are substantially continuous are actually used for gradation display. In such a gradation level, the number of sub-fields in the light-emitting state when the gradation level changes is changed. Also changes roughly step by step,
The variation in the temporal center of gravity of the subfield in the light emitting state is reduced, and the gradation display can be performed using only the combination of the subfields in which the moving image pseudo contour is hardly generated.

Further, one or two lower sub-fields in the non-light emitting state are included between the lower sub-field in the light emitting state having the highest weight and the lower sub-field in the light emitting state having the lowest weight. Since the gradation level can also be used gradation level, the number of gradation levels that can be used as it is can be further increased.

In this example, the gradation level at which a moving image pseudo contour is likely to be generated is expressed by the diffusion processing as described above. However, even if the gradation level at which a moving image pseudo contour is likely to be generated is not used at all. Good. The above points regarding the gradation level at which the moving image false contour is likely to occur are the same for the subfields of other examples described later.

As described above, the lower subfields SF1 to SF6 according to the present example are weighted so that the gradation level continuously changes depending on the combination. In this case, the gradation levels from 0 to 47 are set. It can be expressed continuously. Also, upper subfields SF7 to SF7
Numerals 12 are weighted so that the gradation level changes discontinuously according to the combination, and are weighted in correspondence with mutually different gradation levels. The gradation level is set so that the upper subfield in the non-light emitting state is not included in the upper subfield in the light emitting state among the upper subfields SF7 to SF12.

As described above, the upper subfields SF7 to SF7
Since SF12 is weighted so as to correspond to different grayscale levels, when the higher-order subfields SF7 to SF12 enter the light emitting state due to an increase in the grayscale level, the time of the subfield to be in the light emitting state is reduced. Since the position of the center of gravity does not fluctuate significantly and the temporal fluctuation of the position of the center of gravity of light emission is reduced, the pseudo contour of the moving image can be reduced.

The lower subfields SF1 to SF6
Are weighted so that the gradation level changes continuously depending on the combination, so that the total number of gradations with respect to the number of subfields can be made sufficiently large. As a result, it is possible to reduce the temporal fluctuation of the center of gravity of the light emission and reduce the moving image pseudo contour while securing a sufficient number of gradations.

Also, upper subfields SF7 to SF1
2 is arranged on the time axis so that the weight amount monotonically increases, so that when the upper subfield becomes luminous when the carry level increases due to an increase in the gradation level, the time of the subfield that becomes luminous It is possible to minimize the variation of the temporal center of gravity, and to minimize the variation of the temporal center of gravity of light emission. In this regard, the same applies to the case where the weights are arranged on the time axis so as to monotonously decrease.

Also, a plurality of lower subfields SF1 to SF1
SF6 and a plurality of upper subfields SF7 to SF1
2 are temporally arranged so that the weight amount of 2 monotonically increases. At this time, when there are a plurality of combinations of a plurality of lower subfields SF1 to SF6 capable of displaying the same gradation level, for example, the gradation level 7 is set to the subfield SF
In this example, the gradation level 7 is expressed using the lower subfields SF1 to SF3. As described above, by selecting the combination preferentially used from the lower subfields having the smaller weight, the lower subfields SF1 to SF1 in the light emitting state are selected.
The temporal center of gravity position of No. 6 is gradually moved from the front to the rear or from the rear to the front of one field, so that the fluctuation of the temporal center of gravity of light emission can be made very small. In this regard, the same applies to a case where the weights are arranged on the time axis so as to decrease monotonously.

Next, as another example, a second subfield group used in the plasma display device shown in FIG. 1 will be described. FIGS. 10 to 14 are diagrams showing examples of gray scale display by the second subfield group used in the plasma display device shown in FIG.

As shown in FIG. 10, the second subfield group includes 12 lower subfields SF1 to SF6 and 6 upper subfields SF7 to SF12. The weights of the fields SF1 to SF12 are 1, 2, and 2, respectively.
4, 6, 10, 16, 33, 34, 35, 37, 38,
39.

In this case, lower subfields SF1 to SF
The total weight of F6 is 39, the weight of the upper subfield SF12 having the largest weight among the upper subfields SF7 to SF12 is 39, and a value obtained by subtracting 1 from the weight of the upper subfield SF12. Is smaller than the total value of the weights of the six lower subfields SF1 to SF6.

The weight amount of each subfield corresponds to the light emission amount (luminance) when the subfield emits light. In this example, the subfields SF1 to SF12 are basically combined to form the 0th to 255th floors. It is possible to express all the gradation levels of the tones, but does not use a gradation level by a combination of subfields in which a moving image false contour is likely to occur among the gradation levels that can be expressed by the lower and upper subfields SF1 to SF12. Gray level,
In the figure, the dither gradation level in which a black circle is attached to the column of dither gradation and the error diffusion gradation level in which both the gradation used for display and the dither gradation column are not marked with black circles are different. The used gradation level is used, and the gradation level indicated by a black circle in the column of gradation used for display in the figure is the used gradation level.

Also in this example, lower subfield SF
In the case of 1 to SF6, when there are two or more lower subfields in the non-light emitting state between the subfields in the light emitting state, it is regarded as a gradation level at which a moving image false contour is likely to occur, and the weight of the non-light emitting subfield is the smallest. The lowest subfield SF1 is not considered.

As described above, the lower sub-fields SF1 to SF6 according to the present example are weighted so that the gradation level continuously changes according to the combination. In this case, the gradation levels from 0 to 39 are set. It can be expressed continuously. Also, upper subfields SF7 to SF7
Numeral 12 is weighted so that the gradation level changes discontinuously according to the combination, and is weighted in correspondence with mutually different gradation levels. The gradation level is set so that the upper sub-field in the non-light emitting state is not included in the upper sub-field in the light emitting state among the upper sub-fields SF7 to SF12. As described above, also in this example, the same effects as those in the example using the first subfield group can be obtained.

Next, as still another example, a third subfield group used in the plasma display device shown in FIG. 1 will be described. FIGS. 15 to 19 are diagrams showing examples of gray scale display by a third subfield group used in the plasma display device shown in FIG.

As shown in FIG. 15, the third subfield group includes 12 subfields of 6 lower subfields SF1 to SF6 and 6 upper subfields SF7 to SF12. The weights of the fields SF1 to SF12 are 1, 2, and 2, respectively.
4, 6, 10, 14, 19, 26, 33, 40, 47,
53.

In this case, lower subfields SF1 to SF
The sum of the weights of F6 is 37, the weight of the upper subfield SF12 having the largest weight among the upper subfields SF7 to SF12 is 53, and a value obtained by subtracting 1 from the weight of the upper subfield SF12. Is larger than the total value of the weights of the six lower subfields SF1 to SF6.

The weight amount of each subfield corresponds to the light emission amount (luminance) when the subfield emits light. In this example, 0 to 115, 118 to 155 are obtained by combining the subfields SF1 to SF12. , 165
To 202, 218 to 255, and 116, 117, 156 to 164, 203
217 cannot be expressed.

For this reason, in this example, the gradation levels that can be expressed by the lower and upper subfields SF1 to SF12, that is, 0 to 115, 118 to 155, 165
To 202, 218 to 255 as display gradation levels, and gradation levels that cannot be expressed, ie, 116, 11
The gradation levels of 7,156 to 164,203 to 217 are set as non-display gradation levels, and the above-described diffusion process is performed using the display gradation levels to display the dither gradation column among the non-display gradation levels in the drawing. The dither gradation levels with black circles and the error diffusion gradation levels without black circles are displayed in the columns of gray scales used for display and dither.

Further, among the display gradation levels, a gradation level based on a combination of subfields in which a moving image false contour is likely to occur is set as an unused gradation level. The dither gradation level with a black dot and the error diffusion gradation level without a black dot in the columns of gradation to be used for display and gradation by dither are the unused gradation levels. The gradation level indicated by a black circle in the column of gradation to be used is the used gradation level.

Also in this example, lower subfield SF
In the case of 1 to SF6, when there are two or more lower subfields in the non-light emitting state between the subfields in the light emitting state, it is regarded as a gradation level at which a moving image false contour is likely to occur, and the weight of the non-light emitting subfield is the smallest. The lowest subfield SF1 is not considered.

As described above, the lower subfields SF1 to SF6 according to the present example are weighted so that the gradation level continuously changes depending on the combination. In this case, the gradation levels from 0 to 37 are set. It can be expressed continuously. Also, upper subfields SF7 to SF7
Numerals 12 are weighted so that the gradation level changes discontinuously according to the combination, and are weighted in correspondence with mutually different gradation levels. The gradation level is set so that the upper subfield in the non-light emitting state is not included in the upper subfield in the light emitting state among the upper subfields SF7 to SF12. As described above, also in this example, the same effects as those in the example using the first subfield group can be obtained.

Further, in this example, a value obtained by subtracting 1 from the maximum value of the weight amount weighted to the plurality of upper sub-fields SF7 to SF12 is used as the lower sub-field SF1 to SF1.
Since the sum of the weights weighted to SF6 is larger, the weight of each of the lower subfields SF1 to SF6 can be reduced, and the lower subfield SF1
It is possible to set so that each difference between the weight amounts of SF6 to SF6 becomes small.

Therefore, the weight of the upper subfield, for example, the upper subfield SF7, which is arranged on the time axis in the lower subfields SF1 to SF6 among the upper subfields can be relatively reduced. It is possible to reduce the difference between the weights of the subfields that frequently emit light during gradation display. As a result, the temporal fluctuation of the center of gravity of the subfield in the light emitting state can be suppressed, and the temporal fluctuation of the center of gravity of the light emission can be extremely reduced.

In this example, the difference between the non-display gradation level and the display gradation level is temporally and spatially diffused, and the non-display gradation level is equivalently displayed using the display gradation level. So that non-display gradation levels can be displayed,
The total number of gradations can be increased. Further, the display gradation level is classified into the used gradation level and the unused gradation level, and the difference between the non-used gradation level and the used gradation level is temporally and spatially diffused. Unused gradation levels are equivalently displayed using the used gradation levels.

Therefore, the used gradation level is limited to a gradation level based on a combination of subfields in which a moving image pseudo contour is unlikely to be generated, and a gradation level based on a combination of subfields in which a moving image pseudo contour is likely to be generated is a non-display gradation level. Alternatively, by setting a non-use gradation level, all gradation levels can be displayed using a use gradation level in which a moving image false contour hardly occurs. As a result, all the combinations of the used subfields are combinations of the subfields in which it is difficult to generate the moving image pseudo contour, and the generation of the moving image pseudo contour can be suppressed for all the gradation levels.

In each of the above examples, gradation display is performed using only one set of a lower subfield group including a plurality of lower subfields SF1 to SF6 and an upper subfield group including a plurality of upper subfields SF7 to SF12. Has been described, a plurality of lower sub-field groups and upper sub-field groups are set for each field, and gradation display is performed using the plurality of lower sub-field groups and upper sub-field groups. It may be.

In this case, for example, when the field frequency is as low as 50 Hz as in the case of a PAL television signal, flicker is more conspicuous, but the temporal barycentric position of the subfield used is two in one field. Based on the above points, it is possible to gradually move from the front to the back or from the back to the front of one field. Therefore, while suppressing the temporal fluctuation of the center of gravity of the light emission, the period in which the light emission is concentrated can be dispersed into two or more to make the apparent frequency higher, and the occurrence of flicker can be suppressed. In addition, it is possible to suppress the generation of a moving image false contour.

The numbers and weights of upper and lower subfields applied to the plasma display device of the present invention are not particularly limited to the above examples, and various changes can be made.

[0132]

According to the present invention, when the upper subfield becomes luminous due to an increase in the gradation level and the upper subfield becomes luminous, the temporal fluctuation of the center of gravity of luminescence is reduced, and the pseudo contour of a moving image is reduced. And the total number of gradations with respect to the number of subfields can be made sufficiently large. The contour can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a configuration of a gradation conversion / diffusion circuit shown in FIG. 1;

FIG. 3 is a schematic diagram for explaining error diffusion and accumulation by error diffusion processing.

FIG. 4 is a schematic diagram for explaining the spread of dither amount in dither spread processing in even and odd fields;

FIG. 5 is a first diagram showing an example of gray scale display by a first subfield group used in the plasma display device shown in FIG. 1;

FIG. 6 is a second diagram showing an example of gray scale display by a first subfield group used in the plasma display device shown in FIG. 1;

FIG. 7 is a third diagram showing an example of gray scale display by a first subfield group used in the plasma display device shown in FIG. 1;

FIG. 8 is a fourth diagram showing an example of gray scale display by a first subfield group used in the plasma display device shown in FIG. 1;

9 is a fifth diagram showing an example of gray scale display by a first subfield group used in the plasma display device shown in FIG. 1;

FIG. 10 is a first diagram showing an example of gray scale display by a second subfield group used in the plasma display device shown in FIG. 1;

FIG. 11 is a second diagram showing an example of gray scale display by a second subfield group used in the plasma display device shown in FIG. 1;

12 is a third diagram showing an example of gray scale display by a second subfield group used in the plasma display device shown in FIG. 1;

13 is a fourth diagram showing an example of gray scale display by a second subfield group used in the plasma display device shown in FIG. 1;

14 is a fifth diagram showing an example of gray scale display by a second subfield group used in the plasma display device shown in FIG. 1;

FIG. 15 is a first diagram showing an example of gray scale display by a third subfield group used in the plasma display device shown in FIG. 1;

16 is a second diagram showing an example of gray scale display by a third subfield group used in the plasma display device shown in FIG. 1;

17 is a third diagram showing an example of gray scale display by a third subfield group used in the plasma display device shown in FIG. 1;

FIG. 18 is a fourth diagram showing an example of gray scale display by a third subfield group used in the plasma display device shown in FIG. 1;

19 is a fifth diagram showing an example of gray scale display by a third subfield group used in the plasma display device shown in FIG. 1;

FIG. 20 is a schematic diagram showing n subfields forming one field period in a conventional display device.

FIG. 21 is a schematic diagram showing a configuration of a subfield of a conventional display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 A / D converter 2 Gradation conversion / diffusion circuit 3 Video signal-subfield associator 4 Subfield processor 5 Scan / sustain drive circuit 6 Data drive circuit 7 Plasma display panel 8 Timing pulse generator 21 Gradation conversion Table 22 Error diffusion circuit 23, 24 Adder 25 Subtractor 26-29 Delayer 30-33 Multiplier 41 Dither circuit 42 Dither amount table 43 Adder 44 Subtractor 45 Selection circuit

Continued on the front page (72) Inventor Tomoko Morita 1006 Kazuma Kadoma, Osaka Pref.Matsushita Electric Industrial Co., Ltd. 5C058 AA11 BA02 BA04 BA07 BA35 BB03 BB04 BB13 BB14 BB21 BB25 5C080 AA05 BB05 DD01 EE19 EE29 JJ02 JJ04 JJ05

Claims (20)

[Claims] 1. One field is divided into a plurality of subfields arranged on a time axis in a predetermined order, each subfield is weighted in accordance with a gradation level, and each subfield is weighted in accordance with a video signal. What is claimed is: 1. A display device which performs gray scale display by emitting or non-emitting pixels on a display panel, wherein the plurality of sub-fields are weighted such that a gray level is continuously changed by a combination thereof. The lower subfields are weighted so as to correspond to mutually different grayscale levels, and further, the grayscale levels change discontinuously due to the combination thereof, and the subfields that emit light when each grayscale level is displayed. A plurality of upper sub-fields weighted so as not to include a sub-field that is in a non-light emitting state, and Subfield associating means for converting a video signal of one field into a video signal of each subfield, and a subfield corresponding to each subfield in accordance with the video signal of each subfield output from the subfield associating means. A display device comprising: a light emitting unit that emits or does not emit light from a pixel. 2. The method according to claim 1, wherein the plurality of upper subfields are arranged on a time axis such that a weighting amount weighted corresponding to a gradation level monotonically increases or monotonically decreases. The display device according to the above. 3. The method according to claim 1, wherein a value obtained by subtracting 1 from a maximum value of the weights weighted to the plurality of upper subfields is equal to or less than a total value of the weights weighted to the plurality of lower subfields. 3. The display device according to claim 1, wherein 4. A gradation level which can be displayed by a combination of the plurality of lower sub-fields and the plurality of upper sub-fields; a used gradation level which uses the gradation level as it is; and a non-use which does not use the gradation level as it is. And the difference between the unused gradation level and the used gradation level is temporally and / or in order to display the unused gradation level equivalently using the used gradation level. 2. The apparatus according to claim 1, further comprising a diffusing means for spatially diffusing the light.
The display device according to any one of claims 1 to 3. 5. A value obtained by subtracting 1 from a maximum value of weights weighted to the plurality of upper subfields is greater than a total value of weights weighted to the plurality of lower subfields; Using a display gray level that can be displayed by a combination of a subfield and the plurality of upper subfields, a non-display gray level that cannot be displayed by a combination of the plurality of lower subfields and the plurality of upper subfields is equivalently displayed. 3. The display device according to claim 1, further comprising a diffusion unit for temporally and / or spatially diffusing a difference between the non-display gradation level and the display gradation level. 6. The display device according to claim 6, wherein the display gradation level is classified into a use gradation level that uses the gradation level as it is and an unused gradation level that does not use the gradation level as it is. The difference between the unused gradation level and the used gradation level is temporally and / or spatially diffused in order to equivalently display the unused gradation level using the gray level. The display device according to claim 5. 7. The use gradation level is a gradation level which does not include a lower sub-field which does not emit light between lower sub-fields which emit light when the gradation level is displayed. 7. The display device according to claim 4, wherein: 8. The used gradation level is set between a lower sub-field having the largest weight in a light emitting state and a lower sub-field having a smallest weight in a light emitting state when the gradation level is displayed. 7. The display device according to claim 4, wherein the gradation level does not include two or more lower subfields in a non-light emitting state. 9. The used gradation level is set between a lower sub-field having the largest weight in a light emission state and a lower sub-field having a smallest weight in a light emission state when the gradation level is displayed. 7. The display device according to claim 4, wherein the gradation level does not include three or more lower subfields in a non-light emitting state. 10. The display device according to claim 7, wherein the lower sub-field in the non-light emitting state does not include a lower sub-field having the smallest weight. 11. The display device according to claim 10, wherein the lower sub-field in the non-light emitting state does not include a lower sub-field having the second smallest weight. 12. The display device according to claim 11, wherein the lower sub-field in the non-light emitting state does not include a lower sub-field having the third smallest weight. 13. The method according to claim 13, wherein the plurality of lower subfields and the plurality of upper subfields are arranged on a time axis such that a weight amount weighted corresponding to a gradation level monotonically increases or decreases. When there are a plurality of combinations of the plurality of lower sub-fields capable of displaying the same gradation level, the sub-field associating means displays the gradation level by preferentially combining the lower sub-fields having a smaller weight. 13. The display device according to claim 1, wherein a video signal of one field is converted into a video signal of each subfield. 14. A plurality of lower sub-field groups each including the plurality of lower sub-fields and a plurality of upper sub-field groups each including the plurality of upper sub-fields, wherein the sub-field associating means includes: 3. A video signal of one field is converted into a video signal of each sub-field so that a group and a plurality of upper sub-field groups are combined to obtain a gradation level corresponding to the video signal. 13
The display device according to any one of the above. 15. A field is divided into a plurality of subfields arranged on a time axis in a predetermined order, each subfield is weighted in correspondence with a gradation level, and each subfield is weighted according to a video signal. A display method for performing gray scale display by emitting or non-emitting pixels on a display panel, wherein the plurality of sub-fields are weighted such that a gray level is continuously changed by a combination thereof. The lower subfields are weighted so as to correspond to mutually different grayscale levels, and further, the grayscale levels change discontinuously due to the combination thereof, and the subfields that emit light when each grayscale level is displayed. And a plurality of upper sub-fields weighted so as not to include a sub-field which is in a non-light emitting state. Converting the video signal of one field into a video signal for each subfield, and emitting or not emitting pixels on the display panel for each subfield in accordance with the converted video signal for each subfield. A display method characterized by including: 16. The method according to claim 15, wherein the plurality of upper sub-fields are arranged on a time axis such that the weight amount weighted in correspondence with a gradation level monotonically increases or monotonically decreases. Display method of description. 17. The method of claim 1, wherein a value obtained by subtracting 1 from a maximum value of the weights weighted to the plurality of upper subfields is equal to or less than a total value of the weights weighted to the plurality of lower subfields. Claim 15 or 16
Display method of description. 18. A gradation level that can be displayed by a combination of the plurality of lower sub-fields and the plurality of upper sub-fields, a use gradation level that uses the gradation level as it is, and a non-use that uses the gradation level as it is. And the difference between the unused gradation level and the used gradation level is temporally and / or in order to display the unused gradation level equivalently using the used gradation level. 16. The method of claim 15, further comprising the step of spatially spreading.
18. The display method according to any one of claims 17 to 17. 19. A value obtained by subtracting 1 from the maximum value of the weights weighted to the plurality of upper subfields is greater than the total value of the weights weighted to the plurality of lower subfields; Using a display gray level that can be displayed by a combination of a subfield and the plurality of upper subfields, a non-display gray level that cannot be displayed by a combination of the plurality of lower subfields and the plurality of upper subfields is equivalently displayed. 17. The display method according to claim 15, further comprising a step of temporally and / or spatially diffusing a difference between a non-display gradation level and a display gradation level. 20. The display gradation level is classified into a use gradation level that uses the gradation level as it is and an unused gradation level that does not use the gradation level as it is. And temporally and / or spatially diffusing the difference between the unused gradation level and the used gradation level to equivalently display the unused gradation level using the gradation level. 20. The display method according to claim 19, wherein: