JPH09305142A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a scanning period and to realize multi-level and high- luminance display by giving a scanning pulse given to a scanning electrode in order to select a light emitting point to optional plural lines in the same timing. SOLUTION: This device is provided with a front plate and a back plate where a display part is arranged at a regular interval, gas sealed between the front and back plates, and plural electrodes arranged in a matrix state; and voltage in accordance with an image signal is impressed on the electrodes arranged in the matrix state, so that the gas discharge is generated at an optional position and image display is executed. In such a case, as to driving waveform 100, the scanning pulse 104 given to the scanning electrode of a 1st line and the scanning pulse 105 given to the scanning electrode of a 2nd line are given in the same timing, and whether or not light is emitting in a maintenance period is selected according to an address pulse 101. Then, the scanning pulses are given to every two lines such as a 3rd line and a 4th line in the same timing and the propriety of light emission is selected according to the presence or absence of the address.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention performs gradation control by a time-division driving method such as a liquid crystal display (LCD), a plasma display (PDP), a digital micromirror display (DMD), etc., and is arranged in a matrix. The present invention relates to a display device that displays an image by selectively causing a pixel to emit light.

[0002]

2. Description of the Related Art A conventional plasma display device will be described as an example of a matrix type display device.

[0003] Plasma display devices are roughly classified into A
It is classified into C type and DC type.

FIG. 11 is a block diagram schematically showing a DC type plasma display device 10. As shown in FIG. The plasma display device 10 includes a display panel 11, an address pulse output circuit 12 for driving the address electrodes 15 included in the display panel 11, a scan electrode 16, a scan pulse and sustain pulse output circuit 13, and signal processing for controlling the output circuit. It is configured by the circuit 14.

The display panel 11 has two glass plates, an address electrode 15, a scanning electrode 16, and a partition partitioning a space between the glass plates. The pixel is constituted by a discharge cell which is a space sandwiched between two glass plates and separated by partition walls. In the discharge cell, for example, He-Xe, N
A rare gas such as e-Xe is enclosed, and when a voltage is applied to the address electrode 15 and the scan electrode 16, electric discharge occurs and ultraviolet rays are generated. A fluorescent material is applied to the partition walls, and the partition walls are excited by ultraviolet rays to emit light. Color display can be performed by separately coating the discharge colors of the phosphors into red, green, and blue for each discharge cell and selecting them according to the image signal.

FIG. 7 shows a driving waveform 30 of a DC type plasma display. The electrodes are driven line-sequentially, and address pulses 31 of voltage VA are sequentially sent to address electrodes corresponding to the n-th column of discharge cells in accordance with an image signal. on the other hand,
A scanning pulse 32 of the voltage VS is sequentially applied to the scanning electrodes from the first row.
Is given. In a cell to which the address voltage VA and the scanning voltage VS are simultaneously applied, the inter-electrode voltage exceeds the discharge starting voltage and discharges. This discharge is called address discharge.

Since charged particles remain in the discharged cells, the discharge is generated again at a voltage lower than the discharge start voltage within a certain period after the discharge. Therefore, in the cell where the address discharge has occurred, the discharge is continued by the sustain pulse 33 of the voltage VS2 applied following the scan pulse 32. Such a driving method is called a memory driving method.

Next, a time division driving method (hereinafter referred to as a subfield method) using the above memory driving method will be described. The sub-field method divides one field into a plurality of sub-fields weighted according to the difference in light emission brightness, and selects an arbitrary sub-field for each pixel according to the amplitude of a signal to realize multi-gradation. It is a method to realize.

A driving sequence 40 according to the time division driving method of FIG.
This is an example in the case of displaying six gradations. The scanning period 41 is the first
The sustain period 42 for selecting a light emitting cell of the subfield represents a period during which the selected cell emits light.
The sustain periods of subfields SF1 to SF4 are 8: 4:
The luminance ratio is weighted to 2: 1, and if these subfields are arbitrarily selected according to the level of the video signal, display of 2 to the fourth power = 16 gradations becomes possible.

If it is desired to increase the number of gradations, the number of subfields may be increased. For example, if the number of subfields is 8, 256 gradations can be displayed. The luminance level of each subfield is controlled by the number of pulses. A device and a driving method of this kind are disclosed in, for example, Japanese Patent Laid-Open No. 5-119.
No. 740, etc.

FIG. 12 is a block diagram showing an outline of an AC type plasma display device 20. The plasma display device 20 includes a display panel 21, an address electrode 26, a scan electrode 27, and a sustain electrode 28 included in the display panel 21.
An address pulse output circuit 22, a scan pulse output circuit 23, a sustain pulse output circuit 25, and a signal processing circuit 24 for controlling the output circuit.

The display panel 20 has two glass plates, an address electrode 26, a scan electrode 27, a sustain electrode 28, and partition walls for partitioning a space sandwiched by the glass plates. 2 pixels
It is constituted by discharge cells which are spaces sandwiched between two glass plates and separated by partition walls. Scan electrode 2 for AC type
7. The DC type is characterized in that the sustain electrode 28 is covered with a dielectric.

For example, He-Xe and Ne- are used in the discharge cell.
A rare gas such as Xe is filled in, and the address electrode 2
6. When voltage is applied between the scan electrodes 27, discharge occurs,
Ultraviolet rays are generated. A fluorescent material is applied to the partition walls, and the partition walls are excited by ultraviolet rays to emit light. Color display can be performed by separately coating the discharge colors of the phosphors into red, green, and blue for each discharge cell and selecting them according to the image signal.

FIG. 9 shows an AC type plasma display drive waveform 50. The electrodes are driven line-sequentially, and address pulses 51 of voltage VA are sequentially sent to the address electrodes corresponding to the n columns of discharge cells in accordance with the image signal. on the other hand,
The scanning electrode 52 has a scanning pulse 52 of the voltage VS sequentially from the first row.
Is given. In a cell to which the address voltage VA and the scanning voltage VS are simultaneously applied, the inter-electrode voltage exceeds the discharge starting voltage and discharges. This discharge is called address discharge.

In the cell where the discharge is generated, charges are accumulated on the dielectric covering the electrodes (hereinafter referred to as wall charges), and within a certain period thereafter, at a voltage lower than the discharge start voltage,
The discharge can be generated again. Similar to the DC type, such a driving method is called a memory driving method, and like the DC type, it can be driven by the driving sequence 40 of FIG. In the example of FIG. 12, pulses are alternately applied to the scan electrodes 27 and the sustain electrodes 28 to repeatedly perform discharge and accumulation of wall charges. However, the memory effect due to wall charges is
Other drive sequences have been proposed because of the longer duration of the effect compared to the memory effect with C-type charged particles.

A driving sequence 60 by the time division driving method of FIG. 10 is an example in which 16 gradations are displayed by four subfields SF1 to SF4. The scanning period 61 represents a period for selecting a light emitting cell in the first subfield, and the sustain period 62 represents a period in which the selected cell emits light.

The sustain periods of the subfields SF1 to SF4 are weighted to a luminance ratio of 8: 4: 2: 1, and if these subfields are arbitrarily selected according to the level of the video signal, it becomes 2 It is possible to display 4th power = 16 gradations. As described above, the principle of the time division driving method is similar to that of the DC type (FIG. 7) described above, but the scanning period 61 and the display period 62 are completely separated, and the sustain period is common to all screens. Is characterized in that the drive pulse of For this type of device, for example,
92-86 (1993-3, pp7-11) and the like.

FIG. 13 shows the configurations of the signal processing circuit 14 and the signal processing circuit 24 in the above two conventional examples. The input analog video signal is converted into digital data by the A / D converter 71, and then written into the frame memory 73 through the data write processing circuit 72. The data read from the frame memory 73 is input to the address pulse output circuit via the data read processing circuit 74.

The data converted into a plurality of bits by the A / D converter 71 are processed in parallel in each bit when written in the frame memory 73, and each bit is read in a so-called bit frame unit when read out from the frame memory 73. It is processed. Each bit is assigned to each subfield according to the luminance weighting. As described above, the main feature of this driving method is the digital driving method.

[0020]

At present, a display device is required to have high resolution and high gradation (multi-color) in order to be compatible with all media. In addition, a natural image (whether a moving image or a still image) is captured on the screen and an operation such as enlarging / reducing the image is often performed. In the subfield method in the above-mentioned conventional technique, the scanning period becomes longer as the number of display scanning lines increases, and the sustain period relating to display becomes shorter. Further, if the number of display bits is increased and the number of display gradations is increased, the scanning period becomes longer and the sustain period becomes shorter in the same manner. Therefore, the usage situation as described above, for example, SV
GA (800 x 600 dots), XGA (1024 x 7)
68 dots), SXGA (1280 x 1024), or other high-resolution screens when displaying natural images such as TVs and photo CDs cannot display sufficient brightness or the number of colors, resulting in unnatural display. There were cases. An object of the present invention is to make it possible to represent an image with a sufficient number of colors and brightness under such a use condition.

[0021]

Under the above-mentioned usage conditions, the resolution of a natural image input is generally lower than the resolution of a display in many cases. In that case, since enlarged display is performed, a plurality of dots form one pixel.

As a first configuration for achieving the above object, in the present invention, the scanning pulse applied to the scanning electrodes for selecting the light emitting point is applied to arbitrary plural rows at the same timing. As a result, the scanning period per subfield can be shortened, and the number of subfields and the sustain period can be increased. That is, it is possible to increase the number of gradations and increase the brightness.

As a second structure for achieving the above object, according to the present invention, a plurality of different subfields are assigned to a plurality of dots forming one pixel. As a result, the same effect as increasing the number of subfields in one field can be obtained. Further, it becomes possible to change the linearity of the luminance with respect to the gradation level, and it is possible to obtain a higher quality image.

[0024]

DETAILED DESCRIPTION OF THE INVENTION A first embodiment according to the present invention is shown in FIG. Here, in the display device of the present invention, the display parts are arranged in a matrix with a front plate and a back plate arranged at a constant interval, a gas sealed between the front plate and the back plate. A gas discharge display device having a plurality of electrodes and applying a voltage according to an image signal to electrodes arranged in a matrix to generate a gas discharge at an arbitrary position and display an image.

FIG. 1 shows a driving waveform 100 and a driving sequence 110 when the screen is doubled in the AC type plasma display device 20 of FIG. Here, the conventional drive waveform 50 of FIG. 10 and the drive waveform 100 are compared.

In the drive waveform 50, scanning pulses having different phases are applied to each row, and whether to emit light in the sustain period is selected depending on the presence or absence of the corresponding address pulse. Therefore, when an image is to be enlarged in the vertical direction, it is done by manipulating the address data. On the other hand, in the drive waveform 100, the scan pulse 104 given to the scan electrode of the first row and the scan pulse 105 given to the scan electrode of the second row are given at the same timing, and the address pulse 101 causes light emission in the sustain period. Whether or not is selected.

In the following, scanning pulses are given at the same timing every two rows, such as the third row and the fourth row. Whether to emit light during the sustain period is selected depending on the presence or absence of the corresponding address pulse. The address pulse is determined from the relationship between the number of scanning lines of the signal to be displayed and the number of scanning lines of the display area. For example, when expanding a signal having 240 scanning lines to 480, the address data is 24
It is sufficient to apply the scanning pulse every two rows at the same time with the number of scanning lines being 0. When the number of lines of the input signal is smaller than the number of effective display lines of the display, if an arbitrary plurality of lines are simultaneously scanned, enlarged display can be performed.

When only the central portion of the signal having 480 scanning lines is enlarged and displayed twice, the address pulse is thinned out every other row to obtain data for 240 scanning lines, and scanning is performed. It suffices to apply pulses every two rows at the same time.

Next, the conventional drive sequence 60 and drive sequence 110 of FIG. 10 will be compared. According to the driving waveform 100, in the driving sequence 110, the scanning period 111 required for selecting the light emitting pixel is reduced to one half of the driving sequence 60. Here, if the sustain periods per field are made equal in the drive sequence 60 and the drive sequence 110 so that the emission brightness is preserved, the number of subfields can be increased from 4 to 7. As a result, the number of gray levels that can be displayed is 16 to 128.
Increase to. In this way, the number of display gradations can be increased by giving the scanning pulse like the drive waveform 100.

The display brightness can be increased by applying the decrease in the scanning period to increase the sustain period instead of increasing the number of subfields. Further, increasing the number of subfields and increasing the sustain period may be combined.

Although only the vertical enlarging method has been described above, any method may be used as the horizontal image enlarging method, and any method may be used in the present invention. INDUSTRIAL APPLICABILITY The present invention is particularly effective in displaying a signal such as a TV signal, which has a relatively low resolution but many natural images and important color reproducibility, on a display having a relatively high resolution such as a computer display. Depending on the image, it is possible to intentionally sacrifice the resolution and improve the color reproducibility.

FIG. 2 shows a drive waveform 120 and a drive sequence 130 when the screen is enlarged 1.5 times in the AC type plasma display device 20 of FIG.

In the drive waveform 120, the scanning pulses of the first row and the second row are given at the same timing.

Further, the scan pulse is independently applied to the third row. That is, three scanning lines are scanned in the scanning time of two scanning lines, and the scanning period 131 in the driving sequence 130 is shortened to two thirds of the conventional one. It has the same features as the embodiment of FIG. 1 except that the scanning pulse is applied differently, and the number of gradations and brightness can be increased by shortening the scanning period. In this way, it is possible to arbitrarily set the magnification of the display image enlargement.

3 and 4 show a second embodiment according to the present invention. FIG. 3 shows a driving sequence 140 in the case where, for example, adjacent upper and lower dots form one pixel, two lines corresponding to each dot form a scan line for one pixel, and enlarged display of the screen is performed. There is. The number of subfields per field is three, but by forming scanning lines for one pixel in two rows as will be described later, it is possible to obtain a gradation equivalent to four subfields in appearance. Further, FIG. 4 shows the driving sequence 1
The drive waveform 150 when 40 is adopted is shown. The scanning pulse is applied in synchronization with the address pulse, and selects the pixel that emits light. The selected pixel is supplied with the voltage VS1 by the sustain pulse A in the odd rows and the voltage VS2 by the sustain pulse B in the even rows to emit light.

The sustain pulses A and B are adjusted in the number of sustain pulses per subfield according to the driving sequence 140. In FIG. 3, the odd-numbered scanning period 141 and the even-numbered scanning period 142 are shown in a divided manner for the sake of explanation, but one row to n rows may be scanned one by one as shown in FIG. Of course, separately from this, scanning may be performed every other row twice.

Next, the relationship between gradation and luminance according to the above driving method will be described. FIG. 14 shows the relationship between the gradation and the relative luminance that can be represented by four subfields in the conventional drive sequence 60 of FIG. The notation “1” in the figure means that the corresponding subfield has been selected.
It is possible to express 16 gradations by combining subfields.

15 to 17 show the relationship between the gradation and the relative luminance that can be expressed in this embodiment.

FIG. 15 shows the relationship between gradation and relative luminance that can be expressed when the sustain periods of the odd and even rows are made equal in the drive sequence 140 of FIG. FIG.
The notation “1” in the middle indicates that the corresponding subfield has been selected, and it is 1 depending on the combination of subfields.
5 gradations can be expressed.

The gradation-relative luminance relationship 160 of FIG. 5 is a graph of the gradation characteristic 161 of FIG. 14 and the gradation characteristic 162 of FIG.

As described above, according to the present invention, apparently,
With three subfields per field, it is possible to realize the same gradation characteristics as when driving by four subfields. Therefore, the scanning period can be shortened and the luminance can be improved. Further, as in the conventional example, if there are four subfields, it is possible to obtain the gradation number corresponding to five subfields. In addition,
Fig. 1 shows the combination of subfields for each gradation.
5 shows only an example, and any combination may be selected.

16 and 17 show the relationship between the gradation and the relative luminance that can be expressed when the luminances of the sustain periods of the odd-numbered row and the even-numbered row are set to different values. In the present embodiment, when the luminance ratio of the sustain periods of the odd rows is set to 4: 2: 1 and the luminance ratio of the sustain periods of the corresponding even rows is set to 8: 4: 2,
The relationship between gradation and relative brightness is shown. That is, the sustain period 151 of the drive sequence 140 of FIG.
It is set to 1/2 of 2. The notation "1" in the figure indicates that the corresponding subfield has been selected, and 15 gradations can be expressed by combining the subfields.

As described above, it is possible to realize a display device in which a plurality of dots form one pixel and the plurality of dots forming one pixel have a plurality of different gradation characteristics.

The gradation-relative luminance relationship 170 in FIG. 6 is shown in FIG.
6 is a graph showing the gradation characteristic 172 of No. 6 and the gradation characteristic 171 of FIG. As is clear from the graph, it is possible to change the rate of change of the relative luminance with respect to 15 gradations. The changing point of gradation characteristics can be changed by a combination of subfield selection for emitting light. It is also possible to change the slope of the characteristic by the ratio of the sustain period of the even-numbered rows and the odd-numbered rows.

By changing the gradation characteristics in this way, it becomes possible to display a video with a clearer gradation and a sense of depth when displaying a natural image or the like.

In the above description, the number of basic subfields is four for ease of explanation, but the number is not limited to this and may be any number. Further, the weighting of the sustain period of the subfield does not have to be as shown in this figure. Although the plasma display device 20 of FIG. 12 has been described, the plasma display device 10 of FIG.
The same method can be applied to the drive sequence 40 and the drive waveform 30 of 10 to obtain the same effect.

[0047]

According to the present invention, in a display device which performs gradation control by a time division driving method, for example, SV
GA (800 x 600 dots), XGA (1024 x 7)
68 dots), SXGA (1280 x 1024), or other high-resolution screen, when a natural image such as a TV or photo CD is enlarged and displayed, sufficient brightness or the number of colors can be expressed, and a more natural and high-quality display It is possible to provide an image.

[Brief description of drawings]

FIG. 1 shows a driving waveform and a driving sequence of a display device according to a first embodiment of the present invention.

FIG. 2 illustrates another driving waveform and another driving sequence of the display device according to the first embodiment of the present invention.

FIG. 3 shows a driving sequence of a display device according to a second embodiment of the present invention.

FIG. 4 shows a driving waveform of a display device according to a second embodiment of the present invention.

FIG. 5 shows a gradation-relative luminance relationship in the second embodiment of the present invention.

FIG. 6 shows a gradation-relative luminance relationship in the second embodiment of the present invention.

FIG. 7 shows an example of a drive waveform of a conventional DC type plasma display device.

FIG. 8 shows an example of a driving sequence of a conventional DC type plasma display device.

FIG. 9 shows an example of a drive waveform of a conventional AC plasma display device.

FIG. 10 shows an example of a drive sequence of a conventional AC type plasma display device.

FIG. 11 is a block diagram showing an outline of a conventional DC type plasma display device.

FIG. 12 is a block diagram showing an outline of a conventional AC type plasma display device.

FIG. 13 is a block diagram showing an outline of a signal processing circuit of a conventional plasma display device.

FIG. 14 is a diagram showing the relationship between gradation and relative luminance that can be realized by four subfields in a conventional drive sequence 60.

FIG. 15 is a diagram showing the relationship between gradation and relative luminance that can be expressed when the sustain periods of the odd-numbered row and the even-numbered row in the driving sequence 140 are made equal.

FIG. 16 is a diagram showing a relationship between gradation and relative luminance that can be realized when the luminances of the sustain periods of the odd-numbered row and the even-numbered row are set to different values.

FIG. 17 is a diagram showing a relationship between gradation and relative luminance that can be realized when the luminances of the sustain periods of the odd-numbered row and the even-numbered row are set to different values.

[Explanation of symbols]

10 DC type plasma display device 11, 21 Display panel 12, 22 Address pulse output circuit 14, 24 Signal processing circuit 15, 26 Address electrode 16, 27 Scan electrode 20 AC type plasma display device 25 Sustain pulse output circuit 28 Sustain electrode 30 DC Waveform of driving type plasma display 40 Driving sequence by time division driving method 50 Driving waveform of AC type plasma display 60 Driving sequence by time division driving method 100 Driving waveform when the screen is doubled according to the present invention 110 Screen according to the present invention Driving sequence when enlarging the screen by 120 times 120 driving waveform when enlarging the screen by 1.5 times according to the present invention 130 driving sequence when enlarging the screen by 1.5 times according to the present invention 140 second according to the present invention Drive sequence of the embodiment Other tone over the relative luminance characteristics of the second embodiment according to the gradation over the relative luminance characteristics 170 present invention in a second embodiment according to the second embodiment of the driving waveform 160 present invention according to 150 the invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuichiro Kimura Inventor, Yuichiro Kimura 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa, Ltd., Hitachi, Ltd., Video and Information Media Division (72) Yasushi Noguchi, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Address 292, Hitachi, Ltd. Video Information Media Division (72) Inventor Ken Kumakura 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture 292 Hitachi Ltd. Video Information Media Division

Claims (8)

[Claims] 1. A matrix display type display in which a large number of pixels arranged in the horizontal and vertical directions are selected to emit light by applying a voltage to a plurality of electrodes arranged in a matrix form. A display device, wherein when the number of input signal lines is smaller than the number of lines, enlarged display is performed by simultaneously scanning arbitrary plural lines. 2. A matrix display type display in which a large number of pixels arranged in the horizontal and vertical directions are selected to emit light by applying a voltage to a plurality of electrodes arranged in a matrix form. A display device characterized by enlarging and displaying an arbitrary position on a screen to an arbitrary size by simultaneously scanning the screen. 3. A matrix display type display in which a large number of pixels arranged in a horizontal direction and a plurality of pixels arranged in a vertical direction are selected to emit light by applying a voltage to a plurality of electrodes arranged in a matrix form. The display device characterized in that the number of scanning lines per electrode scanning time is reduced by simultaneously scanning the scanning electrodes corresponding to the above and thinning out the data given to the address electrodes orthogonal to the scanning electrodes according to the input signal. . 4. The display device according to claim 1, wherein a plurality of rows are simultaneously scanned to shorten a scanning period, and the shortened time is weighted by light emission luminance. The display device is characterized in that the number of colors that can be displayed is increased as compared with the case where scanning is performed for each single line by increasing the number of subfields of the generated subfields. 5. The display device according to claim 1, wherein a plurality of rows are simultaneously scanned to shorten a scanning period, and the shortened time is weighted by light emission luminance. The display device is characterized in that the displayable brightness is increased as compared with the case where scanning is performed for each single line by increasing the sustain period of the generated subfield. 6. A matrix display type display in which a large number of pixels arranged in the horizontal and vertical directions are selected to emit light by applying a voltage to a plurality of electrodes arranged in a matrix, and one pixel is formed. A display device characterized by giving different gradation characteristics to a plurality of dots by assigning different subfields to the plurality of dots. 7. The display device according to claim 1, wherein a period of one field is divided into a plurality of subfields weighted by emission luminance, and an arbitrary subfield is selected. A display device characterized by applying a time-division driving method which enables gradation expression. 8. The display device according to claim 1, further comprising: a front plate and a rear plate having display portions arranged at a constant interval, and between the front plate and the rear plate. A gas that is enclosed in a matrix and a plurality of electrodes that are arranged in a matrix are formed. By applying a voltage according to an image signal to the electrodes that are arranged in a matrix, a gas discharge is generated at an arbitrary position. A display device, which is a gas discharge display device for displaying an image.