JP2003177696A - Device and method for display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for display which can reduce a moving picture pseudo-outline without increasing the number of subfields nor lowering gradation display capability. <P>SOLUTION: The display device is characterized by that when N subfields SF1, SF2,..., SFN are weighted corresponding to gradations to have smaller weighting quantities in the order or the same weighting quantity, the subfields include at least one subfield SFM (M: a natural number of 2 to N) whose weighting quantity has a larger difference than that of the sum of weight quantities of the subfields SF1 to SF(M-1), compared with the weighting quantity of the SF1 and also includes at least one SFL (L: a natural integer larger than M and less than N) whose weighting quantity has a smaller difference than that between the sum of the SFL to SF(L-1) and that of the SF1, compared with the weighting quantity of the SF1. <P>COPYRIGHT: (C)2003,JPO

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 in a predetermined order on the time axis, weights each subfield in correspondence with a gradation level, and outputs a video signal. Accordingly, the present invention relates to a display device and a display method for performing gradation display by causing pixels on a display panel to emit or not emit light for each subfield.

[0002]

2. Description of the Related Art A plasma display device using a plasma display panel has an advantage that it can be made thin and have a large screen. In this plasma display device, an image is displayed by utilizing the light emission at the time of discharge of the discharge cells forming the pixels. Further, since the plasma display panel emits light in a binary manner, a sub-field method is used in which a plurality of binary images weighted respectively are temporally overlapped to display a halftone.

In this subfield method, one field is time-divided into a plurality of subfields, and each subfield is 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. .

For example, one field is divided into six subfields, and the weight of each subfield is set to 1,
There are those in which 64 gradations are expressed by setting 2, 4, 8, 16 and 32. In this case, the correspondence between the gradation of the video signal and the subfield that emits light is as shown in Table 1. In (Table 1), the subfields marked with a circle indicate that the subfields emit light.

[0005]

[Table 1]

When the above-mentioned subfield method is used, since the line of sight of the viewer follows the moving image with respect to the moving image, the temporal integration region of the eyes changes spatially, which is unique to the moving image. False contour noise is observed. This contour line is referred to as pseudo contour noise ("pseudo contour noise seen in pulse width modulation moving image display": Technical Report of the Television Society, Vo1.1.
9, No. 2, IDY95-21, pp. 61-66)
This causes deterioration of image quality.

In the case of the subfield shown in Table 1, a large moving image pseudo contour is generated at the boundary between the 31st gradation and the 32nd gradation in which the light emission pattern of the subfield greatly changes.

In order to reduce the above-mentioned dynamic false contour, for example, one field is divided into seven subfields as shown in Table 2 below, and the weighting amount of each subfield is set to "1" or "1". 2 ”,“ 4 ”,“ 7 ”,“ 13 ”,
Some are set to "16" and "20".

[0009]

[Table 2]

In this case, the relative weight difference between the sub-fields becomes small, and the change in the light emission pattern of the sub-field having a large boundary between the 31st gradation and the 32nd gradation (Table 2) is small. The contour can be reduced.

[0011]

However, in the example of (Table 2), although the pseudo contour of the moving image can be reduced, the number of subfields is increased from 6 to 7 for that reason. When the number of subfields in one field increases, the writing time or the like required for that increases, the time for maintaining the light emission relatively decreases, and the screen brightness decreases.

It is an object of the present invention to provide a display device and a display method capable of reducing a moving image pseudo contour without increasing the number of subfields and without lowering the gradation display capability.

[0013]

(1) First invention The display device according to the first invention is N (N is a natural number of 1 or more) in which one field is arranged in a predetermined order on the time axis.
, SFN are divided into subfields SF1, SF2, ..., SFN, and a pixel on the display panel is caused to emit or not emit light for each subfield according to an input video signal to perform gradation display. The N subfields SF1, SF2, ..., SFN are weighted corresponding to the gray scales, and the N subfields SF1, SF2
, ..., SFN have smaller or equal weight amounts in this order, and the N subfields SF1, SF2 ,.
The difference between the weight amount of the subfield SFM and the sum of the weight amounts from the subfield SF1 to the subfield SF (M−1) (M is a natural number of 2 or more and less than N) is the weight amount of the subfield SF1. At least one subfield SFM that is larger than the subfield SFM, and the weight amount of the subfield SFL and (L is a natural number greater than M and equal to or less than N) subfields SF1 to SF
It includes at least one subfield SFL whose difference from the sum of the weight amounts up to (L-1) is smaller than the weight amount of the subfield SF1.

In the display device according to the first aspect of the invention, the difference between the weight amount of the subfield SFM and the sum of the weight amounts of the subfields SF1 to SF (M-1) is the weight amount of the subfield SF1. The N subfields are weighted so as to include at least one subfield SFM which is larger than the above. Thereby,
It is possible to realize fine display at low brightness and coarse gradation at high brightness, and to realize display that matches human visual characteristics.

Further, the weight amount of the subfield SFL and the subfields SF1 to SF (L-1)
The n subfields are weighted so that at least one subfield SFL whose difference from the sum of the weight amounts up to is smaller than the weight amount of the subfield SF1 is included. This makes it possible to reduce the difference in weight between the sub-fields in the sub-field that expresses gray levels of medium brightness or higher, and reduce the moving image pseudo contour.

(2) Second invention In the display device according to the second invention, in the configuration of the display device according to the first invention, the gradation of the input video signal is obtained by combining a plurality of subfields. When at least one combinational gradation level that can be displayed is included and the gradation of the input video signal is the combinational gradation level, the selection means for selecting one combination from the plural combinations. Be prepared.

In this case, if there are a plurality of combinations of subfields expressing gray levels of medium brightness or higher, a combination of subfields with few moving image pseudo contours can be selected, and the moving image pseudo contours can be reduced. be able to.

(3) Third Invention In the display device according to the third invention, in the configuration of the display device according to the second invention, the selection means has the smallest maximum value of the weights of the subfields used for the combination. It includes a weight-oriented selection means for selecting the following combinations.

In this case, since it is possible to select a combination of subfields having the smallest maximum value, it is possible to reduce the difference in the weights of the subfields to be emitted between the gradations of which the values are relatively close to each other, and the moving image pseudo contour Can be reduced.

(4) Fourth Invention In the display device according to the fourth invention, in the configuration of the display device according to the second invention, the selecting means selects a combination that maximizes the number of subfields used for combination. It includes means for selecting the number of pieces to be selected.

In this case, since the number of selected sub-fields can be maximized, the difference in weight between the selected sub-fields can be reduced and the moving image pseudo contour can be reduced. (5) Fifth Invention In a display device according to a fifth invention, in the configuration of the display device according to the first invention, the gradation of an input video signal can be displayed by a combination of the N subfields. At least one non-display gradation level that cannot be displayed due to the combination of the N subfields is included between the gradation levels.
A conversion unit for converting the gradation of the input video signal to a gradation level near the non-display gradation level when the gradation of the input video signal includes the non-display gradation level. Be prepared. In this case, the plurality of sub-fields are weighted so that at least one non-display gradation level that cannot be displayed by the combination is arranged between the display gradation levels that can be displayed by the combination, and the non-display gradation level is Although there are gradation levels that are appropriately dispersed in the display gradation levels and cannot be displayed only by combining subfields, the total number of gradations and the maximum rank are generally maintained without increasing the number of subfield divisions. The tonal level can be increased.

(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 in the vicinity converted by the conversion means is used to perform the non-display. It further comprises a diffusing means for diffusing the difference between the non-display gray level and the display gray level temporally and / or spatially in order to display the display gray level equivalently.

In this case, when the video signal is a video signal of a non-display gradation level, the difference between the non-display gradation level and the display gradation level is diffused temporally and / or spatially, and after the diffusion, 1 A combination of subfields is performed because the field video signal is converted to a video signal for each subfield, and the pixels on the display panel are made to emit or not emit light for each subfield according to the converted video signal for each subfield. It is possible to equivalently display a non-display gradation level that cannot be directly expressed by using the display gradation level.
Therefore, it is possible to display all the gradation levels including the display gradation level and the non-display gradation level, and it is possible to sufficiently increase the maximum gradation level and the total number of gradations that can be displayed. The tonal level can be reproduced with sufficient detail.

As a result, the maximum gradation level and the total number of displayable gradations can be sufficiently increased and the reproducibility of low gradation levels can be improved without increasing the number of subfield divisions. You can

(7) Seventh Invention A display device according to a seventh invention is the structure of the display device according to the sixth invention, wherein the diffusing means is provided with the non-display gradation level and the non-display gradation level. Dither diffusion means for displaying the non-display gradation level by using the neighboring display gradation level by alternately adding or subtracting the difference from the neighboring display gradation level between peripheral pixels or fields It includes. In this case, the difference between the non-display gradation level and the display gradation level in the vicinity of the non-display gradation level among the display gradation levels is alternately added or subtracted between fields or pixels to diffuse. The difference between the non-display gradation level and the display gradation level can be diffused temporally or spatially by the dither diffusion processing, and the non-display gradation level can be displayed using the non-display gradation level. .

(8) Eighth Invention A display device according to an eighth invention is the same as the display device according to the sixth invention, wherein the diffusing means is provided with the non-display gradation level and the non-display gradation level. It includes an error diffusion means for diffusing a difference from a display gradation level in the vicinity to peripheral pixels. In this case, the non-display gray level is converted into a display gray level near the non-display gray level among the display gray levels, and the difference between the non-display gray level and the display gray level is converted to the non-display gray level. It is diffused to pixels around the pixel having the display gradation level. Therefore, the difference between the non-display gradation level and the display gradation level can be spatially diffused, and the non-display gradation level can be equivalently displayed using the display gradation level.

(9) Ninth Invention The display method according to the ninth invention is N (N is a natural number of 1 or more) in which one field is arranged in a predetermined order on the time axis.
, SFN are divided into subfields SF1, SF2, ..., SFN, and a pixel on the display panel is made to emit or not emit light for each subfield according to an input video signal, thereby performing gradation display. The N subfields SF1, SF2, ..., SFN are weighted corresponding to the gray scales, and the N subfields SF1, SF2
, ..., SFN have smaller or equal weight amounts in this order, and the N subfields SF1, SF2 ,.
The difference between the weight amount of the subfield SFM and the sum of the weight amounts from the subfield SF1 to the subfield SF (M−1) (M is a natural number of 2 or more and less than N) is the weight amount of the subfield SF1. At least one subfield SFM that is larger than the subfield SFM, and the weight amount of the subfield SFL and (L is a natural number greater than M and equal to or less than N) subfields SF1 to SF
It includes at least one subfield SFL whose difference from the sum of the weight amounts up to (L-1) is smaller than the weight amount of the subfield SF1.

In the display method according to the ninth aspect of the invention, the difference between the weight amount of the subfield SFM and the sum of the weight amounts of the subfields SF1 to SF (M-1) is the weight amount of the subfield SF1. The N subfields are weighted so as to include at least one subfield SFM which is larger than the above. Thereby,
It is possible to realize fine display at low brightness and coarse gradation at high brightness, and to realize display that matches human visual characteristics.

Further, the weight amount of the subfield SFL and the subfields SF1 to SF (L-1)
The n subfields are weighted so that at least one subfield SFL whose difference from the sum of the weight amounts up to is smaller than the weight amount of the subfield SF1 is included. This makes it possible to reduce the difference in weight between the sub-fields in the sub-field that expresses gray levels of medium brightness or higher, and reduce the moving image pseudo contour.

(10) Tenth Invention In the display method according to the tenth invention, in the configuration of the display method according to the ninth invention, the gradation of the input video signal is obtained by combining a plurality of subfields. Including at least one combination gray level that can be displayed,
When the gradation of the input video signal is the combination gradation level of the plurality of combinations, a selection step of selecting one combination from the plurality of combinations is provided.

In this case, if there are a plurality of combinations of subfields expressing gray levels of medium brightness or higher, a combination of subfields with few moving image pseudo contours can be selected, and the moving image pseudo contours can be reduced. be able to.

(11) Eleventh Invention In the display method according to the eleventh invention, in the configuration of the display method according to the tenth invention, the selection step has the smallest maximum value of the weights of the subfields used for the combination. It includes a weight-oriented selection step of selecting the combination.

In this case, since the combination of subfields having the smallest maximum value can be selected, it is possible to reduce the difference in the weight of the subfields to be emitted between the gradations having relatively close values, and the pseudo contour of the moving image can be obtained. Can be reduced.

(12) Twelfth Invention In the display method according to the twelfth invention, in the configuration of the display method according to the tenth invention, the selecting step selects a combination that maximizes the number of subfields used for the combination. This includes a step of selecting the number of pieces to be selected.

In this case, since the number of selected subfields can be maximized, the difference in weight between the selected subfields can be reduced and the moving image pseudo contour can be reduced.

(13) Thirteenth Invention In the display method according to the thirteenth invention, in the configuration of the display method according to the ninth invention, the gradation of the input video signal is a combination of the N subfields. When at least one non-display gradation level that cannot be displayed due to the combination of the N subfields is included between the gradation levels that can be displayed by, and the gradation of the input video signal is the non-display gradation level, The method further comprises a conversion step of converting the gradation of the input video signal into a gradation level near the non-display gradation level. In this case, the plurality of sub-fields are weighted so that at least one non-display gradation level that cannot be displayed by the combination is arranged between the display gradation levels that can be displayed by the combination, and the non-display gradation level is Although there are gradation levels that are appropriately dispersed in the display gradation levels and cannot be displayed only by combining subfields, the total number of gradations and the maximum rank are generally maintained without increasing the number of subfield divisions. The tonal level can be increased.

(14) Fourteenth Invention A display method according to a fourteenth invention is the display method according to the thirteenth invention, wherein the display gradation levels in the vicinity converted by the conversion step are used to perform the non-display. The method further comprises a diffusion step of temporally and / or spatially diffusing the difference between the non-display gradation level and the display gradation level in order to display the display gradation level equivalently.

In this case, when the video signal is a video signal of the non-display gradation level, the difference between the non-display gradation level and the display gradation level is diffused temporally and / or spatially, and after the diffusion, 1 A combination of subfields is performed because the field video signal is converted to a video signal for each subfield, and the pixels on the display panel are made to emit or not emit light for each subfield according to the converted video signal for each subfield. It is possible to equivalently display a non-display gradation level that cannot be directly expressed by using the display gradation level.
Therefore, it is possible to display all the gradation levels including the display gradation level and the non-display gradation level, and it is possible to sufficiently increase the maximum gradation level and the total number of gradations that can be displayed. The tonal level can be reproduced with sufficient detail.

As a result, the maximum gradation level and the total number of displayable gradations can be sufficiently increased and the reproducibility of low gradation levels can be improved without increasing the number of subfield divisions. You can

(15) Fifteenth Invention A display method according to a fifteenth invention is the structure of the display method according to the sixth invention, wherein the diffusing step is performed for the non-display gradation level and the non-display gradation level. A dither diffusion step of displaying the non-display gradation level by using the neighboring display gradation level by alternately adding or subtracting a difference from the neighboring display gradation level between peripheral pixels or fields. It includes. In this case, the difference between the non-display gradation level and the display gradation level in the vicinity of the non-display gradation level among the display gradation levels is alternately added or subtracted between fields or pixels to diffuse. The difference between the non-display gradation level and the display gradation level can be diffused temporally or spatially by the dither diffusion processing, and the non-display gradation level can be displayed using the non-display gradation level. .

(16) Sixteenth Invention A display method according to a sixteenth invention is the structure of the display method according to the fourteenth invention, wherein the diffusing step is performed for the non-display gradation level and the non-display gradation level. This includes an error diffusion step of diffusing a difference from a display gradation level in the vicinity to peripheral pixels. In this case, the non-display gray level is converted into a display gray level near the non-display gray level among the display gray levels, and the difference between the non-display gray level and the display gray level is converted to the non-display gray level. It is diffused to pixels around the pixel having the display gradation level. Therefore, the difference between the non-display gradation level and the display gradation level can be spatially diffused, and the non-display gradation level can be equivalently displayed using the display gradation level.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION An AC type plasma display device will be described below as an example of a display device according to the present invention. In the following description, the case where the video signal directly corresponds to the brightness, that is, the gradation level will be described. However, when performing color display, the same effect can be obtained by performing the same process for each color. be able to.

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

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

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 it to the gradation conversion / diffusion circuit 2.

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

The gradation conversion / diffusion circuit 2 displays a combination of a plurality of sub-fields when the gradation level of the input image data VD is a non-display gradation level that cannot be displayed due to a combination of a plurality of sub-fields described later. While converting to a possible display gradation level, the difference between the non-display gradation level and the display gradation level is spatially diffused, and the converted image data VV is output to the subfield selector 3.

Since the sub-field selector 3 divides one field into a plurality of sub-fields for display, the sub-field selector 3 selects the sub-field for displaying the gradation of each pixel of the image data of one field, and selects each sub-field. Field image data is created and output to the subfield processor 4.

Specifically, the sub-field selector 3 describes information about which sub-field lights up with respect to the display gradation level, as shown in (Table 3) described later. In the example shown in 3), when the input gradation level is 10, SF4 is selected, SF1 and SF are selected.
2, SF3 may be selected, that is, it is possible to display by a plurality of combinations, but in the example of (Table 3), SF4 is particularly selected.

The subfield processor 4 determines the number of sustain pulses in the sustain period from the image data for each subfield, outputs the data driver drive control signal to the data drive circuit 6, and outputs the scan driver drive control signal and the scan driver drive control signal. 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. In addition, 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 constitutes a pixel on the screen.

The data driving circuit 6 is connected to a plurality of address electrodes of the plasma display panel 7. The scan / sustain drive circuit 5 is 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 the corresponding address electrode of the plasma display panel 7 in accordance with the image data in the write period according to the 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 in the write period. As a result, 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 in the sustain period according to the scan driver drive control signal, and also applies a plurality of sustain electrodes according to the sustain driver drive control signal. Then, a sustain pulse having a phase difference of 180 degrees with respect to the sustain pulse of the scan electrode is applied simultaneously. As a result, sustain discharge is performed in the corresponding discharge cell, and each pixel emits or does not emit light in each subfield.

As described above, in the plasma display device shown in FIG. 1, the ADS (Ad
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 writing period, a sustaining period, and the like, and setup processing of each subfield is performed in the setup period to perform writing. An address discharge for selecting discharge cells to be lit during the period is performed, and a sustain discharge for display is performed during the sustain period.

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

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

The gradation conversion table 21 outputs the display gradation level that can be displayed by combining a plurality of sub-fields among the gradation levels of the input image data as it is, and cannot display it by combining a plurality of sub-fields. The non-display gradation level is converted into a display gradation level near the non-display gradation level and output.

That is, the gradation conversion table 21 includes a table that stores information about display gradation levels, non-display gradation levels, etc., and the input gradation level corresponds to the display gradation level. Convert to. Specifically, the gradation conversion table 21 describes the contents of the display gradation level and the non-display gradation level, for example, as shown in (Table 3) described later, and is shown in (Table 3). In the example,
When the input gradation level is 1, it is output as it is,
When the input gradation level is 2, it is converted to 1 which is the closest display gradation level in the vicinity and is 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 devices 26 to 29, and multipliers 30 to 33.

The adder 23 receives the input image data VD
And the output of the adder 24 are added to obtain the gradation conversion table 21.
And to the subtractor 25. The subtractor 25 is the adder 2
The output of the gradation conversion table 21 is subtracted from the output of No. 3 and output to the delay devices 26 to 29.

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

The multiplier 30 multiplies the input by a predetermined coefficient K1 and outputs it to the adder 24. The multiplier 31 multiplies the input by a predetermined coefficient K2 and outputs it to the adder 24. The multiplier 32 multiplies the input by a predetermined coefficient K3 and outputs it to the adder 24. The multiplier 33 multiplies the input by a predetermined coefficient K4 and outputs it to the adder 24. Here, each coefficient K1, K
2, K3 and K4 are set to appropriate values that satisfy the relationship of K1 + K2 + K3 + K4 = 1, and for example, the coefficients K1 to K4.
Are used as 7/16, 1/16, 5/16, 3/16. 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, the subtractor 25 subtracts the converted gradation level from the original gradation level of the image data VD to obtain the level difference e ′. This level difference e'is delayed by a predetermined time by each of the delay devices 26 to 29, and the predetermined coefficients K1 to K are multiplied by the multipliers 30 to 33.
After being multiplied by 4, they are added by the adder 24 and finally output as the 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. And the gradation after being diffused from the pixel being processed (pixel of e ′) to surrounding pixels (pixels of K1 to K4) and converted by the gradation conversion table 21 with the original gradation level of the pixel being processed. An error diffusion process for spatially diffusing the level difference e ′ from the level is performed, and the converted image data V
V is output. Note that the diffusion error e for a pixel
Is the pixel (pixel of e) as shown in FIG.
It is obtained by summing the errors diffused from the pixels (pixels of K1 to K4) around the.

By performing the above-described error diffusion processing on the entire screen, the gradation levels to be displayed on the entire screen are saved, and when the entire screen is viewed, it is as if the original brightness of the pixel, that is, before the conversion. It seems that it is displayed at the gradation level of. As a result, it is possible to express a high-quality image with no image roughness.

In this way, the gradation conversion / diffusion circuit 2
Converts the non-display gradation level to a display gradation level in the vicinity of the non-display gradation level among the display gradation levels, and calculates the difference between the non-display gradation level and the display gradation level. It is diffused to the pixels around the pixel having the gradation level. Therefore, the difference between the non-display gradation level and the display gradation level can be spatially diffused, and the non-display gradation level can be equivalently displayed using the display gradation level.

In the present embodiment, the gradation conversion / diffusion circuit 2 corresponds to the diffusion means, and the subfield selector 3 corresponds to the selection means. Further, the gradation conversion table 21 corresponds to conversion means, and the error diffusion circuit 22 corresponds to error diffusion means.

Next, a specific example of the subfield used in this embodiment will be described in detail. (Table 3) is
First used in the plasma display device shown in FIG.
3 is a table showing an example of gradation display by the subfield pattern of FIG. In each table below, “◯” in each subfield column at each gradation level indicates a subfield in a light emitting state, a blank column indicates a subfield in a nonlight emitting state, and a column of display enable / disable is shown. Those with "○" are display gradation levels, and those with "x" in the display enable / disable column are non-display gradation levels.

[0070]

[Table 3]

As shown in (Table 3), the first subfield pattern has six subfields SF1 to SF6.
The subfields SF1 to SF10 have weights of "1", "3", "6", "10", "18",
It is “25”, and the weight amount of each subfield corresponds to the light emission amount (luminance) when the subfield emits light. Of course, the weight amount of each subfield may be considered as the number of light emission pulses assigned to each subfield.

In the first subfield pattern shown in (Table 3), the subfields are SF1, SF2, ...
, M, ..., SFN, the weight amount of the subfield SFM and the subfield SF (M-
The difference from the sum of the weight amounts up to 1) is the subfield SF1.
Includes at least one subfield SFM that is larger than the weight amount of M (M is a natural number of 2 or more and less than N), and the weight amount of the subfield SFL and the order from the subfield SF1 immediately before the subfield SFL. At least one subfield SFL whose difference from the sum of the weight amounts up to a certain subfield SF (L-1) is smaller than the weight amount of the subfield SF1 is included (L is a natural number greater than M and equal to or less than N). ) It is configured. For example, when M = 2, the weight amount of the subfield SF2 is "3", and the sum of the weight amounts up to the subfield SF1 is "1". The difference between the weight amount of the subfield SF1 and the weight amount of the subfield SF2 is “2”, which is larger than the weight amount “1” of the subfield SF1. Further, if L = 4, the weight of the subfield SF4 is “10”, and the subfields SF1 to SF4 are
The sum of the weight amounts up to the subfield SF3 immediately before is
Since SF1 is "1", SF2 is "3", and SF3 is "6", "1 + 3 + 6" is "10". The difference between the weight of subfield 4 and the weight of subfields SF1 to SF3 is 0, which is smaller than the weight 1 of SF1. Further, for example, when M = 3, the sum of the weight amounts from the subfield SF1 to the subfield SF2 is "1" for SF1 and "3" for SF2, so "1 + 3" is "4". The weight amount of the field SF3 is “6”. Sum of weights from subfield SF1 to subfield SF2 and subfield S
The difference from the weight amount of F3 is “2”, and the subfield S
It is larger than the weight amount “1” of F1. Further, if L = 5, the weight of the subfield SF5 is "18", and the sum of the weight amounts from the subfield SF1 to the subfield SF4 is "20". The difference between the weight of subfield 5 and the weight of subfields SF1 to SF4 is "-2", which is smaller than the weight "1" of SF1.

With the subfield weights in Table 3 below, the relative weight difference between the subfields when displaying a video signal of medium luminance or higher can be reduced, and the moving image pseudo contour can be reduced. it can. Also, looking at the subfield emission pattern by gradation, between the gradations in the vicinity,
Since there is no gradation in which the light emission patterns of the subfields are completely different, it is possible to reduce the moving image pseudo contour.

Further, in this case, at least two or more display gradation levels are continuous (in (Table 3), "Displayable /
There is one non-display gradation level between the display gradation levels ("No" in the "No" column) (one gradation in the "Displayable / No" column in Table 3). However, the non-display gradation levels are appropriately dispersed among the display gradation levels. Therefore, the maximum gradation level is 63, and the maximum gradation level can be sufficiently increased without increasing the number of subfields.

If the combination of the sub-fields SF1 to SF6 is used as it is, the non-display gradation levels such as the gradation 2 and the gradation 5 cannot be displayed, but each non-display gradation level is set (Table 3). Is converted into the display gradation level shown in the "Conversion value" column, and the value shown in the "Error" column is used as the difference between the non-display gradation level and the display gradation level by the gradation conversion / diffusion circuit 2. Processing is performed. In (Table 3), for example, the gradation level 2 is the gradation level 1 according to the gradation conversion table 21.
And the error value “1” is diffused by the error diffusion circuit 22.

In this way, all non-display gradation levels can be equivalently displayed using the display gradation levels. Therefore, the total number of gradations is 64, the total number of gradations can be made sufficiently large, and the maximum luminance can also be made sufficiently large. In addition, when displaying a moving image,
It is also possible not to use the gradation level at which a moving image pseudo contour is likely to occur.

With the above structure, in the present embodiment, one non-display gradation level that cannot be displayed by the combination is provided between the display gradation levels that can be displayed by the combination of each subfield of the first subfield pattern. They are weighted so that they are arranged, the non-display gradation levels are appropriately dispersed in the display gradation levels, and there are gradation levels that cannot be displayed only by the combination of subfields. It is possible to increase the total number of gradations and the maximum gradation level as a whole without increasing the number.

Further, when the video signal is a video signal of a non-display gradation level, the gradation conversion / diffusion circuit 2 spatially diffuses the difference between the non-display gradation level and the display gradation level, and The selector 3 converts the video signal of one field after diffusion into the video signal of each subfield, and the subfield processor 4, the scan / sustain drive circuit 5 and the data drive circuit 6 respond to the video signal of each subfield. Since the discharge cells of the plasma display panel 7 are made to emit or not emit light for each subfield, it is possible to equivalently display a non-display gradation level that cannot be directly expressed by a combination of subfields by using the display gradation level. .

Therefore, it is possible to display all the gradation levels including the display gradation level and the non-display gradation level, and it is possible to sufficiently increase the maximum gradation level and the total number of gradations that can be displayed. It is also possible to reproduce low gradation levels sufficiently finely. As a result, the maximum gradation level and the total number of displayable gradations can be sufficiently increased and the reproducibility of low gradation levels can be improved without increasing the number of subfield divisions.

(Second Embodiment) Next, a plasma display device according to a second embodiment of the present invention will be described. The difference between the plasma display device according to the second embodiment and the plasma display device shown in FIG. 1 is that the gradation conversion / diffusion circuit 2 is changed to a dither circuit 2a for performing dither diffusion processing. Since the points are similar to those of the plasma display device shown in FIG. 1, only the dither circuit 2a will be described in detail below.

FIG. 4 is a block diagram showing the structure of a dither circuit used in the plasma display device according to the second embodiment of the present invention.

The dither circuit 2a shown in FIG. 4 comprises a dither amount table 42, an adder 43, a subtractor 44 and a selection circuit 4.
Including 5.

The image data VD is stored in the dither amount table 4
2, input to the adder 43 and the subtractor 44. Also in the plasma display device according to the second embodiment, for example, the first subfield pattern shown in (Table 3) is used, and the dither amount table 42 can display (Table 3).
Information is stored as a table in which the non-display gradation level indicated by “x” in the no column and the dither amount described in the dither amount column are associated with each other.

That is, when the gradation level of the input image data VD is the non-display gradation level subjected to the dither diffusion process, the dither amount table 42 adds the dither amount used for the dither diffusion process to the adder 43. When the gradation level of the input image data VD is not the gradation level for the dither diffusion processing, that is, the display gradation level, 0 is output as the dither amount. For example, in the example shown in (Table 3), the dither amount table 42 is
When the gradation level is 2, 1 is output as the dither amount.

The adder 43 receives the output of the image data VD and the dither amount table 42, adds them, and outputs the result to the selection circuit 45. The subtractor 44 receives the image data VD and the output of the dither amount table 42, and receives the image data VD.
A value obtained by subtracting the output of the dither amount table 42 from D is output to the selection circuit 45. The selection signal SC produced by the timing pulse generator 8 is input to the selection circuit 45, and the output of the adder 43 and the subtractor 44 are output at a predetermined timing.
And output of the converted image data VV.

With the above configuration, when the gradation level of the image data VD is the non-display gradation level for performing the dither diffusion processing, the dither circuit 2a diffuses the dither amount set to the non-display gradation level. The dither diffusion process for expressing using the display gradation level obtained in this way is performed. Specifically, when the gradation level of the input image data VD is a non-display gradation level, the dither circuit 2a sets the display gradation level distant by a dither amount from the gradation level to an even number in one field. Image data to be displayed by alternating fields and odd fields is generated.

In the above dither diffusion processing, addition and subtraction of the dither amount (diffusion amount) on the screen are performed such that the total sum 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 vertically and horizontally adjacent pixels, 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. 5, for example, the case shown in FIG. 5A is an even field, and the case shown in FIG. 5B is an odd field.

In this way, the display gradation levels are temporally averaged and an intermediate non-display gradation level can be expressed on the screen. For example, in the example shown in (Table 3), when the gradation level is 2 and the dither amount is 1, the gradation level 1 (gradation "2" -gradation "1") is displayed in one of the even or odd fields. On the other hand, the gradation level 3 (gradation “2” +
The gradation "1") is displayed.

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

The diffusion of the dither amount in the dither diffusion process is not particularly limited to the above example, and addition / subtraction may be performed for each line or addition / subtraction may be performed for each predetermined area. Further, the dither diffusion processing is performed not only in the time diffusion as described above, but also in the same manner as the error diffusion processing, the dither amount is diffused between the pixels by using a predetermined dither pattern, and the spatial diffusion is performed. May be.

In the present embodiment, the dither circuit 2a corresponds to the diffusing means and the dither diffusing means, the video signal-subfield associator 3 corresponds to the subfield associating means, the subfield processor 4, the scanning / scanning The sustain drive circuit 5 and the data drive circuit 6 correspond to the light emitting means.

As described above, in the present embodiment, the difference between the non-display gradation level and the display gradation level in the vicinity of the non-display gradation level among the display gradation levels is determined by the dither circuit 2a between fields. Spread by adding or subtracting alternately. Therefore, the difference between the non-display gradation level and the display gradation level can be temporally diffused by the dither diffusion process. As a result, it is possible to display the non-display gradation level by using the non-display gradation level.
It is possible to obtain the same effect as that of the embodiment.

(Third Embodiment) Next, a plasma display device according to a third embodiment of the present invention will be described. The difference between the plasma display device according to the third embodiment and the plasma display device shown in (Embodiment 1) is that the subfield selecting means 3 has the smallest maximum value of the weights of the subfields used for the combination. Weight-oriented selector 31a for selecting a combination
The sub-field selector 3a is changed to a sub-field selector 3a, and other points are the same as those of the plasma display device shown in FIG.

FIG. 6 is a block diagram showing the structure of a subfield selector 3a used in the plasma display device according to the third embodiment of the present invention.

The subfield selector 3a shown in FIG.
It includes a weight-oriented selector 31a for selecting a combination having the smallest maximum value of weights of subfields used for the combination.

That is, when there are a plurality of combinations of subfields for the input video signal VV, the weight-oriented selector 31a selects the combination of subfields having the smallest maximum value. According to the present embodiment, for example, the subfield pattern shown in (Table 4) is used. In (Table 4), gradation 10, gradation 19, gradation 25, gradation 28, gradation 29, gradation 31, gradation 32, gradation 34, gradation 35, and gradation 38 are plural sub-values. It can be displayed by combining fields ((Table 4)
The gradation marked with ◎ on the right). Specifically, for gradation 10, a pattern in which SF1, SF2, SF3 emit light and S
There is a pattern in which F4 emits light.

[0097]

[Table 4]

In this case, the weight-oriented selector 31a selects a pattern in which the maximum value of combined subfield weights is small, that is, a light emission pattern having SF1, SF2, and SF3 whose maximum value is "6" of SF3. .
Gradation 19, gradation 25, gradation 28, gradation 29, gradation 31,
Also in gradation 32, gradation 34, gradation 35, and gradation 38, the maximum values of subfield weights that are similarly combined are compared, and the maximum value is a small pattern (Table 4).
The subfield emission pattern shown in is selected. The weighting-oriented selector 31a stores the information (Table 4) which is the result of such comparison, and selects subfields to be combined in accordance with the information. In this way, if subfields to be combined in (Table 4) are selected, the difference in light emission pattern of subfields between neighboring gray scales is further increased as compared with the selection pattern of subfields shown in (Table 3). It becomes smaller, and the pseudo contour of the moving image can be further reduced. Further, when the panels are sequentially driven from SF1 to SF6, the subfields that emit light are temporally concentrated more than in the case of (Table 3), and thus the moving image pseudo contour can be reduced also in this respect.

Further, in (Table 4), the gradation level that cannot be displayed due to the possibility of display is converted into a gradation in the vicinity, and the function of equivalently using error diffusion / dither or the like is used for display. Operations similar to those of the embodiment and the second embodiment have similar effects. (Fourth Embodiment) Next, a plasma display device according to a fourth embodiment of the present invention will be described. The difference between the plasma display device according to the fourth embodiment and the plasma display device according to (Embodiment 1) is that the subfield selection unit 3 selects a combination that maximizes the number of subfields. The subfield selector 3b is changed to the subfield selector 3b, and other points are the same as those of the plasma display device shown in FIG. 1. Therefore, only the subfield selector 3b will be described in detail below.

FIG. 7 is a block diagram showing a structure of a subfield selector 3b used in the plasma display device according to the fourth embodiment of the present invention.

The subfield selector 3a shown in FIG.
It includes a number-oriented selector 31b for selecting a combination having the largest number of subfields used for the combination.

That is, in the number-oriented selector 31b, when there are a plurality of combinations of subfields with respect to the input video signal VV, the combination of subfields having the largest number of combined subfields is selected. To do. According to the present embodiment, similar to (Embodiment 3), for example, the subfield pattern shown in (Table 4) is used. In Table 4, gradation 1
0, gradation 19, gradation 25, gradation 28, gradation 29, gradation 3
It is possible to display 1, gradation 32, gradation 34, gradation 35, and gradation 38 in a plurality of combinations of subfields. Specifically, for gradation 10, SF1, SF2, and SF
3 and the pattern in which three subfields emit light, and S
There is a pattern in which only F4 emits light. In this case, the number-oriented selector 31b selects a light emission pattern including SF1, SF2, and SF3 in which the number of combined subfields is large. Gradation 19, gradation 25, gradation 2
8, gradation 29, gradation 31, gradation 32, gradation 34, gradation 3
5, the number of subfields to be similarly combined is compared in the gradation 38, and the subfield emission pattern shown in (Table 4) is selected. Number-oriented selector 31b
Stores the information (Table 4) that is the result of such comparison, and the subfields to be combined are selected according to the information. In this way, if subfields to be combined are selected, similar to the example described in (Embodiment 3), the selection patterns of subfields shown in (Table 3) are further increased between neighboring gray scales. The difference in the light emitting pattern between the subfields is reduced, and the pseudo contour of the moving image can be further reduced. Also, SF
When the panel is driven in order from 1 to SF6 (Table 3)
Since the subfields that emit light are temporally concentrated more than in the case of (3), it is possible to reduce the moving image pseudo contour in this respect as well.

The number of subfields, the amount of weight, and the like applied to the plasma display device of the present invention are not particularly limited to the examples of the above-described embodiment, and various changes can be made.

[0104]

According to the present invention, a plurality of subfields are weighted so that at least one non-display gradation level that cannot be displayed by the combination is arranged between the display gradation levels that can be displayed by the combination. When the video signal is a non-display gray level, the non-display gray level is displayed because the difference between the non-display gray level and the display gray level is diffused temporally and / or spatially. The gradation level can be used for equivalent display.
Therefore, it is possible to display all the gradation levels including the display gradation level and the non-display gradation level, and it is possible to sufficiently increase the maximum gradation level and the total number of gradations that can be displayed. The tonal level can be reproduced with sufficient detail. As a result, the maximum gradation level and the total number of displayable gradations can be sufficiently increased and the reproducibility of low gradation levels can be improved without increasing the number of subfield divisions.

Further, it is possible to reduce the relative weight difference between the subfields when displaying a video signal of medium brightness or higher, and to reduce the moving image pseudo contour. Further, looking at the light emission pattern of the sub-field according to the gray scale, there is no gray scale in which the light emission patterns of the sub-fields are completely different between the neighboring gray scales, and the moving image pseudo contour can be reduced.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a gradation conversion / diffusion circuit of the plasma display device.

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

FIG. 4 is a block diagram showing a configuration of a dither circuit used in the plasma display device according to the second embodiment of the present invention.

FIG. 5 is a schematic diagram for explaining diffusion of the dither amount in the dither diffusion processing in the even field and the odd field.

FIG. 6 is a block diagram showing a configuration of a subfield selection circuit used in a plasma display device according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a subfield selection circuit used in the plasma display device according to the fourth embodiment of the present invention.

[Explanation of symbols]

1,1a A / D converter 2, 2b, 2c, 2d gradation conversion / diffusion circuit 2a dither circuit 3 subfield selector 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 delay device 30-33 multiplier

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/66 101 G09G 3/28 HF term (reference) 5C058 AA11 BA01 BA07 BA33 BB04 BB25 5C080 AA05 BB05 DD30 EE29 FF12 GG11 GG12 JJ02

Claims (16)

[Claims] 1. A field is divided into N (N is a natural number of 1 or more) subfields SF1, SF2, ..., SFN arranged in a predetermined order on a time axis, and is divided according to an input video signal. , SFN for displaying gray scales by causing pixels on a display panel to emit or not emit light for each subfield.
, The N subfields SF1, SF2, ..., SFN have smaller or equal weight amounts in this order, and the N subfields SF1, SF2 ,. , SFN
Is the weight of the subfield SFM and (M is 2 or more and N
Less than a natural number) a difference from the sum of the weight amounts from subfield SF1 to subfield SF (M-1) is greater than the weight amount of subfield SF1, and at least one subfield SFM is included, and The weight amount of the subfield SFL and (L is a natural number greater than M and less than or equal to N) subfields SF1 to SF (L
The difference from the sum of the weight amounts up to -1) is the subfield SF
Subfield SF that is smaller than the weight amount of 1
A display device comprising at least one L. 2. The gradation of the input video signal includes at least one combination gradation level that can be displayed by a plurality of combinations of the sub-fields, and the gradation of the input video signal is the plurality of gradation levels. The display device according to claim 1, further comprising: a selection unit that selects one combination from the plurality of combinations in the case of a combination combination gradation level. 3. The display device according to claim 2, wherein the selecting unit includes a weight-oriented selecting unit that selects a combination having the smallest maximum value of weights of subfields used for the combination. 4. The display device according to claim 2, wherein the selection unit includes a number-oriented selection unit that selects a combination having the largest number of subfields used for the combination. 5. The gradation of the input video signal includes at least one non-display gradation level that cannot be displayed by the combination of the subfields, between the gradation levels that can be displayed by the combination of the subfields, When the gradation of the input video signal is the non-display gradation level, a conversion means for converting the gradation of the input video signal into a gradation level near the non-display gradation level is provided. The display device according to claim 1, wherein the display device is a display device. 6. The non-display gray level and the display gray level for displaying the non-display gray level equivalently using the neighboring display gray level converted by the converting means. The display device according to claim 5, further comprising a diffusing unit that diffuses the difference temporally and / or spatially. 7. The diffusion means alternately adds or subtracts a difference between the non-display gray level and a display gray level near the non-display gray level between neighboring pixels or fields. 7. The display device according to claim 6, further comprising dither diffusion means for displaying the non-display gradation level by using the neighboring display gradation level. 8. The diffusion means includes an error diffusion means for diffusing a difference between the non-display gradation level and a display gradation level near the non-display gradation level to peripheral pixels. The display device according to claim 6. 9. One field is divided into N (N is a natural number of 1 or more) subfields SF1, SF2, ..., SFN arranged in a predetermined order on the time axis, and is divided according to an input video signal. , SFN, which is a display method for performing gradation display by causing pixels on a display panel to emit or not emit light for each subfield.
, The N subfields SF1, SF2, ..., SFN have smaller or equal weight amounts in this order, and the N subfields SF1, SF2 ,. , SFN
Is the weight of the subfield SFM and (M is 2 or more and N
Less than a natural number) a difference from the sum of the weight amounts from subfield SF1 to subfield SF (M-1) is greater than the weight amount of subfield SF1, and at least one subfield SFM is included, and The weight amount of the subfield SFL and (L is a natural number greater than M and less than or equal to N) subfields SF1 to SF (L
The difference from the sum of the weight amounts up to -1) is the subfield SF
Subfield SF that is smaller than the weight amount of 1
A display method comprising at least one L. 10. The gradation of the input video signal includes at least one combination gradation level that can be displayed by a plurality of combinations of the sub-fields, and the gradation of the input video signal is the plurality of gradation levels. 10. The display method according to claim 9, further comprising a selection step of selecting one combination from the plurality of combinations in the case of a combination combination gradation level. 11. The display method according to claim 10, wherein the selection step includes a weight-oriented selection step of selecting a combination in which the maximum value of the weights of subfields used for the combination is the smallest. 12. The display method according to claim 2, wherein the selection step includes a number-oriented selection step of selecting a combination having the largest number of subfields used for the combination. 13. The gradation of the input video signal includes at least one non-display gradation level that cannot be displayed by the combination of the subfields, between the gradation levels that can be displayed by the combination of the subfields, When the gradation of the input video signal is the non-display gradation level, a conversion step of converting the gradation of the input video signal to a gradation level near the non-display gradation level is provided. The display method according to claim 9, wherein the display method is a display method. 14. The non-display gray level and the display gray level for displaying the non-display gray level equivalently using the neighboring display gray level converted by the converting step. 14. The display method according to claim 13, further comprising a diffusing step of diffusing the difference temporally and / or spatially. 15. The diffusion step comprises alternately adding or subtracting a difference between the non-display gradation level and a display gradation level near the non-display gradation level between peripheral pixels or fields. 15. The display method according to claim 14, further comprising a dither diffusion step of displaying the non-display gradation level by using the neighboring display gradation level. 16. The diffusion step includes an error diffusion step of diffusing a difference between the non-display gradation level and a display gradation level near the non-display gradation level to peripheral pixels. The display device according to claim 14.