JPH09258689A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a pseudo-counter generated in a moving picture by performing a display by a picture diffusion signal whose signal level is changed with prescribed offsets or amplitudes every (n) pixels and line. SOLUTION: An input video signal VIN and an offset video signal VOF are changed over every pixel by a diffusion control signal DSW to be converted into a picture element diffusion signal VDS. After the signal VDS modulated in such a manner is converted into a digital signal by being inputted to an A/D conversion part 16, an arrangement conversion for driving a PDP panel 19 is performed in a digital signal processing part 17 and this signal is converted into the driving signal of the PDP panel 19 by being inputted to a PDP display driving part 18 to be displayed on the panel 19. Thus, a signal whose phases are inverted each other every one pixel in horizontal and vertical directions in a screen to emit light is displayed on the screen. Then, when the pixel interval of the screen is a small area in the output picture diffusion signal VDS of a video signal selecting part 15, two changed over levels of the signal are recognized by being averaged by the spatial and timewise integration effect of the visual sense of a human being.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for displaying a halftone image on a display device, and more particularly, to A / D conversion of a video signal, and the obtained digital signal is time-width or pulse-width modulated. However, the present invention relates to a matrix type display device such as a plasma display device (hereinafter referred to as PDP) or a liquid crystal, which performs halftone or gradation display by controlling emission / non-emission.

[0002]

2. Description of the Related Art Conventionally, in a matrix type display device which displays an image by binary light emission and non-light emission,
As a method of expressing a half-tone image, for example, in the case of PDP, the document "A half-tone moving image display by AC type plasma display" (IE72 image engineering research group material IT72-45, Kaji et al., 1973-03), etc. There is a method. This method is capable of gradation expression equivalent to that of a display device typified by a conventional CRT, and the PDP has N levels.
It may be used as a method of displaying a natural image such as TSC.

FIG. 15 is a diagram showing the principle of displaying a halftone image of a conventional matrix type display device, for example, a PDP, and shows the timing of light emission in each pixel of the display device. Generally, when a video signal is subjected to digital signal processing, it is quantized by 6 to 8 bits or more, but in this figure, for simplification, it is quantized by 4 bits and the timing for displaying 16 gradations is shown. In the figure, 1
Is the addressing period for writing to the PDP panel,
2, 3, 4, and 5 are 2 ⁰ = 1, 2 ¹ = 2, 2 ² =
Shows the weighted emission period by the time a load of 4,2 ⁴ = 8. The addressing period shown in 1 is a period for selecting and switching to the pixels of the entire screen whether or not to light the selected pixel in the following light emitting periods of 2, 3, 4, and 5. It is assumed that light emission is not performed during the period. The sequence including 1 to 5 is sequentially repeated for each unit of one field (1F), and the 16 gradation levels displayed in each pixel are obtained by combining the binary-weighted light emitting periods 2, 3, 4, and 5. The amount of light emitted in one field is controlled and expressed by. Also, control the gradation of all pixels for each field,
This makes it possible to express halftone gradations corresponding to moving images. Thus, a display device such as a PDP is
The video signal of one field is divided into a plurality of subfields each having a different relative ratio of luminance, and light emission and non-light emission of these subfields are controlled for each pixel to perform halftone gradation display.

[0004]

Since the display device using the binary light emitting element represented by the conventional PDP is constructed as described above, it has the following problems. FIG. 16 shows 1 when the gradation changes from “7” to “8” based on the sequence shown in FIG.
The light emission pattern of the pixel is shown. In this case, the gradation
In 7 ″, since 7 = (0111) ₂ , the light emitting periods 2, 3,
Only 4 emits light, and when the gradation is “8”, 8 = (1000) ₂ so that only the emission period 5 emits light.

Here, in consideration of general human visual characteristics, according to the document “Visual Information Processing” (Kenji Tasaki et al., Asakura Shoten), “temporal weighted effect on brightness sensation” is obtained. can give. This effect is a Ferry-Port
Also known as the er rule, the critical flicker frequency (CFF, C
Rital flicker frequency
y) With the above frequencies, it is shown that the blinking light does not flicker and is felt as if it were continuous light. The frequency of flicker changes depending on the brightness, but
It is found that the sensitivity becomes maximum at about 20 Hz, and the sensitivity gradually decreases at frequencies around that, so that the flicker of brightness at the field frequency (about 60 Hz) of a general television signal such as NTSC is hardly detected. .
(Hereafter, this effect is called the "temporal integration effect" of visual characteristics.)

Therefore, the PD is formed in the pattern as shown in FIG.
If all the pixels of the P panel change in gradation at the same time, gradation
In the 7 "and gradation" 8 "light emitting regions, the light emitting and non-light emitting components that fluctuate within the field frequency are integrated and averaged by the temporal integration effect of the human visual characteristics described above, and the level is smoothed. It seems that the key has changed from "7" to "8".

However, the above change is displayed as a pattern in which the change of each pixel is different on the screen, that is, as a moving image,
When observed, the following phenomena occur. For example, if a pattern that divides the screen in the vertical direction (left screen has gradation "8" and right screen has gradation "7") moves from left to right on the screen over time, the light emission on the screen The pattern can be represented by the schematic diagram shown in FIG. Here, the horizontal axis indicates the pixel array in the horizontal direction, and is configured in units of one pixel.
The vertical axis is a time axis, and time has passed downward. The light emission pattern appearing on this plane is obtained by rotating the pattern shown in FIG. 16 clockwise by 90 degrees and changing the gradation by one pixel. Each one is drawn by shifting one field in the time direction. In the figure, the shaded portion 6 represents the light emitting period, and the white portion 7 represents the non-light emitting period. As shown in the figure, the switching portion between the gradation “7” and the gradation “8” is moved from left to right. In this figure,
Although the signal change of only one line is shown in the horizontal direction, but if the signal is not changed in the vertical direction, the light emission pattern of FIG. 17 is generated at the same timing on all lines. When such a pattern is displayed, the human eye tracks the switching portion of the light emission pattern, and therefore, it looks as if the light emission pattern was observed obliquely. As a result, it is perceived as the brightness represented by the perceptual brightness characteristic 8 in the lower right of FIG. Then
By observing the light emission pattern obliquely, the light emission gap 9 between the gradation “7” and the gradation “8” is detected as a fixed pattern that does not change in the time direction, and a black (no light emission) band-shaped Detected as jamming. Also, if the above gradation change is changed to the reverse pattern of gradation "8" to gradation "7", or if the moving direction of the moving image is changed from right to left with the above gradation change, the above disturbance will occur. Occurs as a concentrated light emission and becomes a high-luminance (white or colored) band-shaped interference. This phenomenon is a disturbance peculiar to displaying a moving image and is known as a false contour. This disturbance occurs not only in the change from the gradation "7" to "8" as in the above example, but also in the case of the carry or the carry of the binary display to some extent to some extent.

Further, as described with reference to FIG. 15 above, the number of gray scales to be displayed is determined by the number of periods in which the addressing period and the light emitting period weighted by the time load are combined. PD with restrictions
In P, etc., when displaying a video signal such as NTSC, the number of display gradations that can be incorporated in a given field period (about 16.7 ms) is limited, and in particular, due to human visual characteristics, black which is sensitive to level changes On the side, there was a problem that the gradation was insufficient.

The present invention has been made to solve the above problems, and a first object thereof is to display a moving image on a matrix type display device for displaying an image by binary light emission / non-light emission. The purpose is to reduce false contours detected in the case of. The second object is to improve the gradation performance near the black level of the signal even when the number of gradations to be driven is small.

[0010]

In a display device according to the present invention, an image signal of one field is divided into a plurality of subfields having different luminance relative ratios, and each of the plurality of subfields emits light for each pixel. In a display device that displays a halftone image by not emitting light, based on the image signal to be displayed, the signal level for each n pixels (n is an integer of 1 or more) and for each line has a predetermined offset or amplitude. Then, a pixel diffusion signal that changes with is generated, and display control is performed by the pixel diffusion signal.

Further, on the basis of the image signal to be displayed, a pixel diffusion signal whose signal level changes with a predetermined offset or amplitude for every n pixels (n is an integer of 1 or more), for each line, and for each field is generated. However, display control is performed by the pixel diffusion signal.

Further, a signal group having a plurality of different offset levels or signal amplitudes is generated from the image signal to be displayed,
Select two types of signals from these converted signals,
The display is switched and displayed alternately for every n pixels (n is an integer of 1 or more) and for each line.

Further, a signal offset means for superimposing an offset signal on the input image signal is provided, and the superimposing offset level is switched and displayed for every n pixels (n is an integer of 1 or more) and for each line. is there.

Further, a signal amplitude control means for varying the amplitude of the input image signal is provided to switch and display the output signal amplitude for every n pixels (n is an integer of 1 or more) and for each line. is there.

Further, there is provided signal level conversion means for performing analog / digital conversion (hereinafter referred to as A / D conversion) of the image signal to be displayed, and level conversion of the digitally converted image signal, and converting the level of the image signal. A plurality of types of tables are provided, and two types of conversion tables are selected and displayed from the signal conversion table by a switching signal in which the polarity is inverted for each n pixel (n is an integer of 1 or more) and for each line.

Further, the characteristics of the two types of conversion tables selected from the plurality of types of conversion tables provided in the signal level conversion means are conversion characteristics different from each other.
The average level of the conversion table of the type is set so as to compensate for the characteristic added in advance to the input video signal, for example, the inverse γ characteristic of the CRT.

Further, the characteristics of the two types of conversion tables selected from the plurality of types of conversion tables provided in the signal level conversion means have mutually different conversion characteristics, and the conversion of the selected two types of conversion tables is performed. The switching level is set to a different place.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the display device according to the present invention, a pixel diffused signal whose signal level changes with a predetermined offset or amplitude for every n pixels (n is an integer of 1 or more), or n
Since the pixel diffusion signal whose signal level changes with a predetermined offset or amplitude is displayed for each pixel (n is an integer of 1 or more), for each line, and for each field, continuous display is performed on the screen. Pixels that carry up or down the gradation level can be separated and further shifted, and as a result, the level of false contours that occur in a moving image is dispersed, and the level is averaged with the offset or amplitude-changed signal level. Work to be visible.

With respect to the two types of conversion tables, the average level is set in advance so as to be a characteristic for correcting the characteristic added to the input signal. It works as a characteristic obtained by adding the two characteristics of the conversion table to the correction characteristics of the various changes.

Furthermore, regarding the above-mentioned two types of conversion tables, since the switching portions of the conversion characteristics are set at different places, the composite characteristics of the two types of conversion tables work so that the number of gradations increases.

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. In the following description of the embodiments, a display method according to the present invention or a control method thereof is referred to as a “pixel diffusion method”, and a switching signal for controlling according to the present invention is a (pixel) diffusion control signal, The converted video signal will be referred to as a pixel diffusion signal.

Embodiment 1. 1 is a block diagram of a PDP device according to a first embodiment of the present invention.
Is a clock generator that receives a horizontal synchronizing signal HD and supplies a clock signal CLK synchronized with the horizontal synchronizing signal HD, and 11 divides the clock signal by 1 / (n + 1) (n is an integer of 1 or more),
a switching signal for switching the video signal for every n pixels,
A clock divider circuit that inverts it and generates an inverted switching signal that is 180 degrees out of phase, 12 is a spread switching signal generator that receives the HD and the vertical synchronization signal VD as input, and generates a spreading switching signal that is inverted at every HD, 13 is a clock frequency dividing circuit 11
The spread control signal DS is selected by the spread switching signal from two types of divided pulses obtained from
A divided signal selection unit for generating W, 14 is an input video signal V
Offset video signal VO with offset added to IN
A video signal level conversion unit for obtaining F, a video signal selection unit for selecting the input video signal VIN and the offset video signal VOF by the diffusion control signal DSW, and a pixel diffusion signal VDS, and a pixel diffusion signal VDS for the pixel diffusion signal VDS. Is converted into a digital signal, 17 is a digital signal processing part for performing processing for driving the PDP on the A / D-converted pixel diffusion signal, and 18 is various controls for driving the display of the PDP panel 19. Signal and drive signal generation PDP
It is a display drive unit. Further, 20 is a clock frequency dividing circuit 1
1 is a spreading control signal generating unit including a spreading switching signal generating unit 12 and a divided signal selecting unit 13.

The operation of the PDP device thus constructed will be described below. 2 is a block diagram of the spreading control signal generator 2 of FIG.
The timing chart of the vertical synchronizing signal VD, the horizontal synchronizing signal HD, the clock CLK, and the diffusion control signal DSW of an arbitrary field at 0 is shown. However, here, CL
K indicates a waveform when HD is divided by an even division ratio, and DSW is when the division ratio of the clock dividing circuit 7 is divided by ½ (when n = 1). The waveform is shown.

First, the spread control signal DS shown in FIG.
Looking at the W waveform, if the first line of this field is a pulse starting with a positive polarity, the next second line is a pulse starting with a negative polarity, and the next third line is a positive polarity. The pulse to be started and the signal whose polarity is inverted line by line become a signal, and the relationship in which the polarity is inverted line by line is continuously maintained in the field,
The inversion relationship for each pixel and line continues,
It forms the diffusion control signal DSW.

The input / output waveforms of the video signal selecting section 15 at this time are shown in FIG. The input video signal VIN and the offset video signal VOF are converted into a pixel diffusion signal VDS switched for each pixel by the diffusion control signal DSW. The pixel diffusion signal VDS modulated in this way is supplied to the A / D converter 1
6 is converted into a digital signal, the digital signal processing unit 17 performs array conversion for driving the PDP panel 19, and this is input to the PDP display driving unit 18 and P
Converted into a drive signal for the DP panel 19 and converted into a PDP panel 19
Is displayed. As a result, signals that are mutually phase-inverted in the horizontal and vertical directions on the screen are emitted and displayed.

Here, when considering the general human visual characteristics, there are the following spatial characteristics in addition to the "temporal integration effect" described in the conventional example. According to the document "Visual Information Processing" (Asakura Shoten, Kyoji Tasaki et al.), There is spatial weighting in addition to temporal weighting in brightness perception, and when the area of the stimulating light is within a certain limit, light is perceived. It is not the luminance L that defines the threshold, but rather the luminance multiplied by the stimulus area A L × A
According to Ricco's law, it is understood that, for example, when binary brightness is alternately emitted in a small area, the brightness becomes an average value thereof. It is also known that the human spatial frequency characteristic (MTF) is a band pass type to a low pass type characteristic. From these facts as well, a pattern in which light emission and non-light emission are alternately arranged in a small area is performed. Indicates that the brightness is an average value and the spatial pattern of the light emission is difficult to detect. (Hereafter, this effect is called the "spatial integration effect" of visual characteristics.)

Therefore, if the pixel spacing is a small area, the output pixel diffusion signal VDS of the video signal selection section 15 has two signal levels switched by the spatial and temporal integration effect of human vision. Are averaged and recognized.

The appearance of an image when the signal processed as described above is displayed on a PDP device as a moving image will be described below. As described in the conventional example, the false contour interference at the time of displaying a moving image is caused by a human being when moving in a direction where there is a gradation change portion where a carry or a carry occurs in a binary display of a light emission pattern of a pixel. The eye follows the carry up or down part (brightness change part),
This is a disturbance in which a gap or concentration of light emission is perceived due to a change in the light emission pattern at that portion. Therefore, if the carry-up or carry-down of the gradation is shifted between adjacent pixels, it can be expected to reduce the perceived level of this disturbance by the visual spatial integration effect.

In the description of this embodiment, the offset amount is "+1" for simplicity. Therefore, 7 = (0111) for the conventional light emitting area of gradation "7".
_{It is} assumed that ₂ and (1000) ₂ are switched and displayed 8 = (1000) ₂ and (1001) ₂ for each pixel and for each line in the light emitting area of the conventional gradation “8”.

FIG. 4 shows a light emission pattern in the "pixel diffusion method" of the present invention, in which the horizontal axis represents a pixel array in the horizontal direction, and is composed of one pixel unit. The vertical axis is the time axis, and time passes downward. Here, assuming that the interval between vertically adjacent pixels is very small and the signals between these pixels are signals with offsets respectively,
Due to the above visual spatial integration effect, the light emission pattern of each pixel can be seen as a pattern in which light is emitted in the vertical direction, that is, two adjacent offset signals are averaged.

Here, the pixel diffused light emission pattern appearing on this plane is divided into the following three light emission levels. Two
The shaded region 1 indicates the entire light emission period in which both polarities of the diffusion control signal DSW emit light, and the shaded region 22 indicates the single emission period in which light is emitted in only one polarity according to the diffusion control signal DSW, 23 If the region indicated by white circles is a non-light emitting period, the perceived amount of brightness here is 0.5 when the total light emitting period of 21 is 1, and the non-light emitting period of 23 is 0.5. The period is considered by multiplying the coefficient by 0. As a result,
As shown in the brightness perception characteristic 24, the gradation is originally “7”.
The gap 9 of the light emission that occurred when the carry of the gradation "8" from the
Has been reduced.

In the first embodiment, the conversion signal VOF generated in the video signal level conversion unit 14 is limited to one type, and the input video signal VIN and the conversion signal VOF are alternately switched for each pixel. However, the degree of the above-mentioned effect changes depending on the offset amount of the signal, the pixel speed to be displayed, etc.,
The video signal level conversion unit 14 generates a plurality of types of offset video signal groups, and two optimum types of converted signals from the offset signal group and the input signal are displayed. It may be designed to be selectively switched according to an image or a moving image.

The conversion signal generated by the video signal level conversion unit 14 does not change the offset level of the input video signal, but its signal amplitude (gain) is controlled according to the timing of the diffusion control signal DSW. However, as is clear from the principle described in this embodiment,
The same effect can be obtained.

Further, when the pixel pitch of the panel to be displayed is smaller than the frequency band of the input video signal,
The same effect can be obtained by increasing the frequency division ratio of the pixel diffusion signal and configuring the device with the frequency division ratio of 2 pixels or more n pixels.

Embodiment 2 In the above-described first embodiment, an example in which the spread control signal DSW in which the offset is superimposed by the switching signal whose polarity is inverted for each pixel and for each line of the display screen is formed has been described. Further forms the diffusion control signal DSW by a switching signal whose polarity is inverted also in the time direction, that is, between fields. This is because switching is performed only for each pixel or line of the display screen, and in a small / medium screen with a small pixel pitch of the PDP panel, the spatial patterns diffused by the pixels are averaged only by the spatial integration effect, which is sufficient. Although such a false contour reduction effect can be obtained, when the screen is enlarged and the viewer can recognize the pixel pitch to a certain extent or more, the spatial integration effect alone becomes insufficient. Therefore, in the present embodiment, when a spatial pattern diffused by pixels is detected, the false contour reduction is further achieved by adding a temporal integration effect for each pixel.

FIG. 5 shows a vertical sync signal VD, a horizontal sync signal HD, a clock CLK, and a spread control signal DSW of an arbitrary M-th field (M is a positive integer) in the present embodiment.
And the spreading control signal DS of the next (M + 1) th field
It is a diagram showing a timing chart of W, and the schematic configuration of other devices is the same as that of FIG. 1 described in the first embodiment. Also in the present embodiment, CLK indicates a waveform when HD is divided by an even division ratio, and two DSWs divide the division ratio of the clock dividing circuit 7 by 1/2. Is shown (when n = 1).

First, looking at the waveform of the diffusion control signal DSW in the Mth field shown in FIG. 5D, assuming that the first line of this field is a pulse starting with a positive polarity, the next second line Is a pulse that starts with a negative polarity, and the next third line is a pulse that starts with a positive polarity and is a signal whose polarity is inverted line by line. It is maintained continuously.

Next, looking at the waveform of the spreading control signal DSW in the (M + 1) th field in FIG. 5E, the first line of this signal starts with the negative polarity of the opposite polarity to that in the previous Mth field. The second second line is a pulse signal having a positive polarity, and the next third line is a pulse signal having a negative polarity. A polarity signal obtained by inverting the signal in the Mth field is a signal of this field. It is continuously maintained within. The relationship of the signal polarities in the Mth field and the (M + 1) th field of the diffusion control signal DSW is continuously maintained thereafter, and the inversion relationship for each pixel, each line, and each field is continued, and the diffusion control signal It forms the DSW. The operation of the device using this spread control signal is the same as that of the first embodiment, and therefore its explanation is omitted.

Embodiment 3 In the first or second embodiment, first, the converted signal V is converted by the video signal level converter 14.
After the OF is obtained, the video signal selection unit 15 alternately switches the input video signal VIN and the conversion signal VOF for each diffusion control signal DSW. However, as shown in FIG. 6, the DC level of the video signal VIN is directly controlled. The pixel diffusion signal VDS can be obtained even if the signal offset control unit 25 is configured, and the same effect can be obtained.

Embodiment 4 FIG. Further, in the first or second embodiment, the conversion signal V generated by the video signal level conversion unit 14 is not changed in the offset level but is changed in signal amplitude (gain).
Although the structure of the OF is also shown, as shown in FIG.
Even if the signal amplitude control unit 26 capable of directly controlling the signal amplitude of IN is used, the pixel diffusion signal VD
S can be obtained, and the same effect can be obtained.

Embodiment 5. FIG. 8 shows an input video signal VIN
27 shows an embodiment in which the signal level is converted after A / D conversion, and 27 is a signal level conversion for level converting the digital video signal VID after the input signal is digitally converted by the A / D converter 16. The output is converted by the diffusion control signal DSW into the pixel diffusion video signal VDS diffused into two signal levels. As a result, with the same effect as described in the first or second embodiment, it is possible to reduce the false contour that occurs when a moving image is displayed.

Here, as an example of the configuration of the signal level conversion unit 27, a memory device or the like is used, and the input / output conversion table is set to 2
It can be easily realized by incorporating various types. In particular, when the input video signal is a standard television signal or the like, the input video signal has an inverse γ for correcting the CRT emission characteristic.
Since the characteristics are applied, when displaying on a display device such as a PDP or a liquid crystal, it is necessary to perform γ conversion on an input video signal, and in many cases, a γ correction signal level conversion unit is already installed. The signal level converter 27 of the present invention
May be configured independently of the γ-correction signal level conversion section, but in the γ-correction signal level conversion section, a plurality of characteristic tables are prepared in advance and the spread signal generated by the spread signal generation section 15 is generated. With the structure that can be controlled by the DSW, the effect of the present invention can be obtained without adding a new circuit element.

FIG. 9 shows an example of the above-mentioned input / output conversion table. In FIG. 9, characteristic 28 and characteristic 29
Indicates the two types of signal levels obtained from the signal level conversion unit 27, and the average level 30 of these is the characteristic that is visually recognized. Therefore, in the above example, the characteristics 28 and 29 may be determined so that the γ correction signal level conversion characteristic becomes the average level 30. In the case of this embodiment, the variation width ΔS of the characteristics 28 and 29 with respect to the average level 30 is linearly increased in a region where the input level is small, and is a constant value in a region where the input level is medium to large. Here is an example. Of course, Δ
The amount of change in S can be set to a fixed value, or it can be changed stepwise,
You may combine these.

Embodiment 6 FIG. Next, the PD configured in FIG.
In the P device, an example in which the input level of the conversion table in the signal level conversion unit 27 is low, that is, the characteristics in the vicinity of the black level of the signal, is shown in FIG. In this case, two types of signal conversion levels 2 with respect to the average level 30
When 8 and 29 are selected as shown in FIG. 10, the number of gradations at the level 30 which is visually recognized as the average value thereof is compared with the number of gradations 31 shown in FIG. 11 in the case where the present invention is not performed. It shows that it is possible to increase.

That is, according to the present invention, since the average level 30 obtained by averaging the characteristic 28 having a large inclination and the characteristic 29 having a small inclination is perceived, the number of gradations obtained as a result is the addition of two gradation characteristics. If the characteristics are determined so that the gradation on the side of the characteristic 28 where the conversion level has a large slope is increased, the gradation is increased especially near the black level of the signal where the original gradation change is gentle. It has the effect of increasing the number.

Next, in FIG. 12, the conversion level 28 when the average level 30 of the two signal conversion levels is very gentle and the slope of the conversion level 28 having the larger slope as described above cannot be made too large, An example of how to give 29 is shown. That is, as shown in the figure, by shifting the change points of the two types of signal conversion levels 28 and 29, it is possible to increase the number of gradations of the averaging level 30 of the two characteristics. FIG. 13 shows the level conversion characteristic 31 when the present invention is not performed along the asymptote of the average level 30 of FIG. Clearly, it can be seen that the averaging level 30 according to the present invention in FIG. 12 has an increased number of gradations.

As described above, in addition to the effect of reducing the false contour described in the first or second embodiment of the present invention, the conversion characteristics of the two types of signal conversion levels are given as shown above. The effect of being able to reproduce more gradations than the actual gradation number can be expected without increasing the number of operating gradations.

Embodiment 7 FIG. FIG. 14 shows the fifth embodiment.
In the above, the signal level control unit 27 is replaced by a signal offset control unit 32. In this case, the signal offset control unit 32 causes the spread control signal D
By controlling the offset amount of the input signal at the timing of SW, the pixel diffusion signal VDS can be directly obtained, and the false contour reducing effect can be obtained in the same manner as described above.

Embodiment 8 FIG. In addition, in FIG. 15, in the fifth embodiment, a signal amplitude control unit 33 is provided instead of the signal level conversion unit 27. In this case, the signal amplitude control unit 33
In, the amplitude of the input signal can be controlled at the timing of the diffusion control signal DSW to directly obtain the pixel diffusion signal VDS, and the false contour reducing effect can be obtained in the same manner as described above.

By the way, in the above description, the present invention is applied to the PD.
Although the case of using it for the P device has been described, it goes without saying that it can also be used for other matrix type display devices which display an image by binary light emission / non-light emission.

[0051]

Since the present invention is constructed as described above, it has the following effects.

In the display device according to the present invention, display is performed for every n pixels (n is an integer of 1 or more) and for each line by a pixel diffusion signal whose signal level changes with a predetermined offset or amplitude. Therefore, it is possible to separate the pixels that carry up or down the gradation level continuously on the screen and shift them further. As a result, the level of the false contour generated in the moving image is dispersed, and the offset or amplitude changes. It works by making it visible at the level averaged with the signal level, and can reduce false contours that occur in moving images.

Further, in the display device according to the present invention, a pixel diffusion signal whose signal level changes with a predetermined offset or amplitude for every n pixels (n is an integer of 1 or more), for each line, and for each field. Since the display is performed, it is possible to separate pixels that carry or carry a gradation level continuously on the screen, and further shift them.
Since the level of the false contour generated in the moving image can be further dispersed, the false contour generated in the moving image can be further reduced by working so as to be seen as an averaged level with the signal level with the offset or the amplitude changed.

Further, a plurality of signal groups having different offset levels or amplitude levels are generated from the image signal to be displayed, two kinds of signals are selected from these, and the selected two signals are selected.
By obtaining the pixel diffusion signal by switching the type of signal for every n pixels of the display and for each line,
False contours that occur in moving images can be reduced.

Further, by providing the signal offset control means to obtain the pixel diffusion signal in which the offset amount of the signal changes every n pixels of the display and every line from the direct input image signal, the false contour generated in the moving image is reduced. it can.

Further, a signal amplitude control means is provided,
By obtaining a pixel diffusion signal in which the signal amplitude changes every n pixels of the display and every line from the direct input image signal, the false contour generated in the moving image can be reduced.

Further, the level conversion means provided with a plurality of A / D conversion means and a conversion table for converting the level of the signal is profitable, two kinds of conversion tables are selected from the plurality of conversion tables, and n pixels of the display are selected. By obtaining these pixel diffusion signals by switching between these two types of conversion tables for each and every line, it is possible to reduce false contours that occur in a moving image.

Further, regarding the above-mentioned two types of conversion tables, by making the average level a characteristic for correcting the change characteristic added in advance to the input signal, the circuit originally provided for the correction of the characteristic can be reduced. In addition, the gradation can be improved for the characteristic that the signal changes gently.

Furthermore, regarding the above two types of conversion tables, the number of gradations can be increased and the gradation can be improved by setting the switching portions of the conversion characteristics to different places.

[Brief description of drawings]

FIG. 1 is a block diagram of a PDP device showing a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the spreading error signal generating unit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing operation waveforms according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a light emission pattern of a moving image according to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining the operation of the spreading error signal generating unit according to the second embodiment of the present invention.

FIG. 6 is a block diagram of a PDP device showing a third embodiment of the present invention.

FIG. 7 is a block diagram of a PDP device showing a fourth embodiment of the present invention.

FIG. 8 is a block diagram of a PDP device showing a fifth embodiment of the present invention.

FIG. 9 is a diagram showing an example of a conversion table provided in a signal level conversion unit according to a fifth embodiment of the present invention.

FIG. 10 is a diagram showing an example of effects of the sixth embodiment of the present invention.

FIG. 11 is a diagram showing an example of a conversion table in a conventional example.

FIG. 12 is a diagram showing an example of a second effect of the sixth embodiment of the present invention.

FIG. 13 is a diagram showing a second example of a conversion table in a conventional example.

FIG. 14 is a block diagram of a PDP device showing a seventh embodiment of the present invention.

FIG. 15 is a block diagram of a PDP device showing an eighth embodiment of the present invention.

FIG. 16 is a diagram showing a principle of displaying a halftone image of light emitted from a PDP.

FIG. 17 is a diagram showing a light emission pattern of pixels of a PDP.

FIG. 18 is a diagram showing a light emission pattern of a conventional moving image.

[Explanation of symbols]

1 addressing period, 2 1 time-weighted emission period, 32 time-weighted emission period, 4 4 time-weighted emission period, 5 8 time-weighted emission period , 6 light emitting period, 7 non-light emitting period, 8 brightness perception amount characteristic, 9 light emitting gap, 10 clock generating unit, 11
Clock divider circuit, 12 Spread switching signal generator, 13
Frequency division signal selection unit, 14 Video signal level conversion unit, 15
Video signal selection section, 16 A / D conversion section, 17 digital signal processing section, 18 PDP display drive section, 19 PD
P panel, 20 Spread control signal generator, 21 Full emission period, 22 Single emission period, 23 Non-emission period, 24 Perceptual characteristic of brightness, 25 Signal offset unit, 26 Signal amplitude control unit, 27 Signal level conversion unit, 28 Conversion table characteristics with a larger slope, 29 Conversion table characteristics with a smaller slope, 30 Average level conversion table characteristics, 31 Conversion table characteristics when the present invention is not implemented

Claims (7)

[Claims] 1. A halftone image is displayed by dividing an image signal of one field into a plurality of subfields each having a different relative ratio of luminance and making each of the plurality of subfields emit or not emit light for each pixel. In a display device, a pixel diffusion signal is generated for every n pixels (n is an integer of 1 or more) and for each line, the signal level of which changes with a predetermined offset or amplitude based on the image signal to be displayed, A display device characterized by performing display control by a spread signal. 2. The predetermined change of the signal level of the pixel diffusion signal is changed every n pixels (n is an integer of 1 or more), line by line, and field by field. Item 2. A display device according to item 1. 3. The pixel diffusion signal includes two types of signals selected from a plurality of types of signal groups having different offset levels or signal amplitudes for every n pixels (n is an integer of 1 or more) and for each line. The switching signal is generated alternately by switching based on a switching signal whose polarity is inverted.
The display device according to any one of the preceding claims. 4. The pixel diffusion signal is obtained by directly determining an offset level or a signal amplitude of an image signal to be displayed based on a switching signal in which the polarity is inverted for every n pixels (n is an integer of 1 or more) and for each line. The display device according to claim 1, wherein the display device is controlled and generated. 5. A signal level conversion means having a plurality of types of conversion tables for converting the signal level of a digitally converted image signal is provided, and the pixel diffusion signal is provided for every n pixels (n is an integer of 1 or more), 2. The display device according to claim 1, wherein the display device is configured to alternately perform level conversion using two types of conversion tables selected from the signal level conversion means based on a switching signal whose polarity is inverted line by line. 6. The conversion characteristics of the selected two types of conversion tables are set so that the average level obtained by conversion based on the two types of conversion tables corrects the characteristics added in advance to the image signal to be displayed. The display device according to claim 5, wherein the display device is a display device. 7. The conversion characteristic of the selected two types of conversion tables is set such that the change points of the signal conversion level are different from each other. Display device.