JPH10254407A - Display device, drive circuit and gradation display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gradation display technique without picture quality deterioration. SOLUTION: Plural sub-fields are made arrangement provided with an arrangement part of order that the number of displaying pulses allocated to respective sub-fields become more and the arrangement part of order becoming less. Then, when a final operated sub-field in a prior field is switched to the operated sub-field of the number of maximum displaying pulses in a succeeding field between adjacent fields, and the gradation is increased by hone level, this final operated sub-field is made to become a rear side than this sub-field of the number of maximum displaying pulses in the arrangement order in the field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a gas discharge panel,
The present invention relates to a display technique for an EL display device, a fluorescent display tube, a liquid crystal display device, and the like.

[0002]

2. Description of the Related Art Conventionally, as a technique for displaying a gradation of an image on a matrix panel, for example, Kaji et al .: IEICE Technical Report on Image Engineering, Document No. IT72-45 (197)
3-03) (1973.3.12) There is a memory type gas discharge panel described in "Display of halftone moving image by AC type plasma display". In the prior art, for example, in an 8-bit gray scale, each subfield is divided into b0, b1, b2,
.., B7 (b0: subfield with the shortest display period (lowest subfield), b7: subfield with the longest display period (highest subfield)), arrangement order of subfields for representing gradation Is the order of b0, b1, b2,... B7, in which the display period gradually increases within one field time (for example, 1/60 second (s) (about 16.7 ms for NTSC television signals)). ing.

[0003]

In the above-described subfield arrangement in the prior art, the image quality of a moving image deteriorates, and the moving image appears to be grayed-out or the pixels appear to be coarse.

The problems to be solved by the present invention will be described below with reference to FIGS. 2 to 5 by taking a gray scale display technique in the case of a gas discharge television as an example.

FIG. 2 is a diagram showing an example of a sectional structure of a cell of a three-electrode gas discharge panel. On the substrate 200, the first electrode (cathode) 220, Ba or Ni, are formed of a material such as LaB _6. On the other hand, a third electrode (display anode) 240 is formed on the face plate 210 by a printing technique or the like. The discharge space (display discharge space 250 and auxiliary discharge space 27)
0) is formed by a laminated structure of spacers and the like, and the second electrode (auxiliary anode) 230 is also provided at a predetermined position.

When a discharge (display discharge) occurs between the first electrode (cathode) 220 and the third electrode (display anode) 240, the gas (Xe or Ne-Xe, H) in the display discharge space 250 is generated.
e-Xe or other mixed gas) to generate ultraviolet rays,
0 is emitted and display is performed. An auxiliary discharge, which is a so-called pilot discharge, is generated between the first electrode 220 and the second electrode (auxiliary anode) 230. Whether or not this auxiliary discharge shifts to a display discharge between the first electrode 220 and the third electrode 240 depends on whether or not a pulse voltage is applied to the second electrode 230.

FIG. 3 shows a matrix type gas discharge panel 30.
It is a figure which shows the example of a connection structure of 0 electrode and an electrode lead wire.
The first and third electrodes of the cell 350 of the gas discharge panel are:
(In this example, and the number of electrode leads 480, K ₁ number from the top in the order of each lead, K _2, ... are the K ₄₈₀₎ the first electrode lead 310 laterally and the third electrode lead wire 3
40 (in this example, the number of electrode leads at 480, A _1, A ₂ from the top the number of each lead wire, ... is set to A ₄₈₀₎ is connected to, the second electrode second electrode in the longitudinal direction Lead wires (auxiliary anode lead wires) 320 and 330 are connected.

FIG. 4 shows a waveform of a voltage applied to the electrodes.

In FIG. 4, V _K denotes a first electrode lead wire 3.
A waveform 400 of a voltage applied to the first electrode via 10 and a pulse 400 for addressing one line in the matrix panel (hereinafter, referred to as a first electrode address pulse).
In FIG. 4, the pulse width of the first electrode address pulse is equal to the time width Δ (= 1H / number of gray scale bits, H: horizontal scanning period) assigned to address one line. . For example, when a television signal is displayed in 8-bit gradation (256 gradations), the time width Δ is Δ
≒ 7.9 μs.

In FIG. 4, Vs is a pulse (second electrode pulse) 41 applied to the second electrode via the second electrode lead wire.
0 is a voltage waveform. The second electrode pulse 410 has a smaller pulse width than the first electrode address pulse 400,
It is located behind the time width Δ. The second electrode pulse may or may not be present depending on the content of the television signal.

Further, _VA is applied to the third electrode via the third electrode lead wire.
5 is a waveform of a voltage applied to an electrode. For the same line number of the first electrode lead and the third electrode lead,
The voltage of the pulse 420 is applied to the first electrode address pulse 400
Immediately after, the voltage is continuously applied to the third electrode a number of times corresponding to the display period of the subfield.

Next, the discharge between the electrodes will be described with reference to periods I, II, and III in FIG.

When the voltage of the address pulse 400 is applied to the first electrode, a discharge, that is, an auxiliary discharge occurs between the first electrode and the second electrode in a period I. This auxiliary discharge occurs in the auxiliary discharge space 270 (FIG. 2). Since there is no phosphor on the wall surface of the auxiliary discharge space 270 and the auxiliary discharge space 270 is located at a position hidden from the front side of the panel, the auxiliary discharge has little effect on display image quality.

Next, during the period II in which the voltage of the pulse 410 is applied to the second electrode, the potential difference between the first electrode and the second electrode is reduced, so that the discharge between the first electrode and the second electrode is reduced. Stops. However, as described above, since the pilot discharge (auxiliary discharge) has already been performed in the period I, the first discharge is performed in the period II.
Many space charges exist near the electrodes. Therefore, a new discharge, that is, a display discharge occurs between the first electrode and the third electrode. The transition of the discharge from the second electrode to the third electrode in this manner is referred to herein as switching. When this switching is performed, a large number of charged particles are generated in a discharge path (display discharge space 250) between the first electrode and the third electrode.

Next, in period III, first, the third electrode
The voltage of the pulse 420 having a small width is applied. Period II above
As a result, a large amount of charged particles are present in the display discharge space 250, and a discharge is generated between the first electrode and the third electrode by the voltage of the pulse 420. Due to this discharge, charged particles are further generated in the display discharge space 250, and the discharge is caused by the voltage of the next pulse 430. Thus, in the period III, this discharge continues during the period in which the pulse voltage is continuously applied. This is called a pulse memory. This discharge causes the phosphor 260 to emit light and display is performed. This discharge stops even when the pulse voltage is continuously applied, when a new voltage is applied to the first electrode.

In the case where the panel does not emit light for display, FIG.
Pulse 410 is not applied to the second electrode. In this case, the switching is not performed and the first
No discharge occurs between the electrode and the third electrode. Therefore, the number of charged particles in the display discharge space 250 is small. Therefore, the third
Even if the voltages of the pulses 420 and 430 are applied to the electrodes, no discharge occurs and the phosphor 260 does not emit light. As described above, the discharge between the first and third electrodes can be controlled by controlling the presence or absence of the pulse 410 of the second electrode, and the display light emission of the panel can be controlled.

Next, with reference to FIG. 5, an example of an 8-bit gray scale (256 gray scale) image display in the case of a gas discharge panel will be described.

FIG. 5 is a diagram showing an example of the waveform V _{K of} the voltage applied to the first electrode and the waveform _VA of the voltage applied to the third electrode during one field. A voltage of eight pulses 400 corresponding to the subfield is applied to the first electrode during one field. Each of the eight pulses 400 is referred to as an address pulse in each subfield b0, b1, b2,. As shown in FIGS. 4 and 5, the voltage of the pulse 420 applied to the third electrode is repeatedly applied immediately after the application of the address pulse 400, and ends before the next subfield address pulse 400 comes. Pulse 420 is
In each of the subfields b0, b1, b2,..., A display period corresponding to each subfield is formed.

Each of the subfields b0, b1, b2... B7
, The ratio of the number of pulses of the pulse 420 in each subfield to the subfields b0, b1, b2,.
If the ratio is 2: 4: 8:...: 128, this combination constitutes 256 gray levels of the binary code of the image. It is determined whether the panel is to be displayed by the voltage of the pulse 420 applied to the third electrode during the period corresponding to the address pulse 400 in each of the subfields b0, b1, b2,. 410).

In a conventional gradation display, as shown in FIG.
From the lowermost (shortest display period) subfield b0 to progressively higher (longer display period) subfields,
That is, they are arranged in the order of b0, b1, b2,.
In this case, as shown in Table 1, when the gradation level changes by one level between level 127 and level 128, when the level is 127, display is performed in seven subfields b0 to b6, When the level is 128, display is performed only in the subfield b7.

[0021]

[Table 1]

As is apparent from FIG. 5, in the case of the conventional technique, the level 127 is displayed in a certain field,
When displaying the level 128 in the next field, the time width of one field (about 16.7
ms), there is a period in which the display unit does not emit light at all. Especially in the case of moving images, the image quality is significantly degraded due to this.
The gradation appears to be dropped, or the pixels appear to be coarse.

Table 2 shows the case of another gradation level. As shown in Table 2, when the gray level changes between adjacent fields, when the gray level changes between level 63 and level 64, when the level changes between level 31 and level 32, or when level 15 and level When it changes between 16,
Further, like the change between the level 191 and the level 192, when the level changes between the level 63 and the level 64 with reference to the level 128 of the subfield b7, a long non-light emitting period is generated in the display unit. There is image quality degradation for moving images. This deterioration in image quality is remarkable in the case of a display with high luminance.
If the brightness is low, it is difficult to observe.

[0024]

[Table 2]

As described above, in the above prior art,
Since the order of the subfields is the order of b0, b1,... B7, the image quality of the moving image is degraded.

An object of the present invention is to provide a gradation display technique which does not cause such image quality deterioration.

[0027]

In order to achieve the above-mentioned object, according to the present invention, as a basic configuration, (1)
A plurality of subfields are arranged having an arrangement portion in the order of increasing the number of display pulses assigned to each subfield, and during a display operation, between adjacent fields, An operation subfield for setting the display unit to a display state, wherein the number of display pulses is switched to a higher subfield such as a subfield having the largest number of display pulses or a subfield having the second largest number of display pulses. When the gradation increases by one level, the last operation subfield in the preceding field is arranged so that the arrangement order in the field is later than the operation subfield in the subsequent field. I do. Further, (2) a plurality of subfields are arranged having an arrangement portion in which the number of display pulses assigned to each subfield is increased and an arrangement portion in which the number of display pulses is decreased, and In the display operation, an operation sub-field in which the display section of the array sub-field is in a display state between adjacent fields, wherein the number of display pulses is the largest or the number of display pulses is 2
When the number of display pulses such as the next largest subfield is switched to the upper subfield and the gray level rises by one level, the last operation subfield in the preceding field is higher than the operation subfield in the subsequent field. , Are arranged such that the order of arrangement in the field is on the rear side. Further, (3) the plurality of subfields are arranged so as to have an arrangement portion in which the number of display pulses allocated to each subfield is increased and an arrangement portion in which the number of display pulses is decreased. In addition, at the time of display operation, an operation sub-field in which the display section of the array sub-field is in a display state between adjacent fields, wherein the sub-field having the largest number of display pulses or the number of display pulses is 2 When the number of display pulses, such as the next largest subfield, is switched to the upper subfield and the gray level rises by one level, when the display period of the last operation subfield in the preceding field ends and the operation subfield in the subsequent field The arrangement is such that the time interval from the start of the field display period is less than one field.

A plurality of subfields in the field
An array configuration in which the number of display pulses allocated to each subfield has an array portion in the order of increasing and an array portion in the order of decreasing the number of display pulses is such that the subfields of the number of display pulses are distributed in each field. Let it. The configuration of the distributed arrangement and the number of display pulse sub-fields, which are the most active sub-fields in the succeeding field from the last active sub-field in the preceding field, or the number of display pulses in the second, When the number of display pulses such as a large number of sub-fields is switched to a higher-order sub-field and the gradation is increased by one level, the last operation sub-field in the preceding field is set to be smaller than the operation sub-field in the subsequent field. The configuration in which the arrangement in which the order is rearward in the field is combined with the configuration of the preceding field, particularly when the gradation level changes at a halftone level such as 1/2 level or 1/4 level of the highest gradation. From the end of the display period of the last active sub-field to the start of the display period of the active sub-field in the subsequent field To shorten the time in, the time difference between the time to less than one field.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIGS.

As is apparent from the above description, in order to improve the image quality deterioration, a plurality of subfields are basically divided into a display period in which a predetermined number of display pulses are allocated in one field period. What is necessary is just to arrange in the order which performs. In such an arrangement, a light emission period always exists within one field period even if the level 127 and the level 128 in Table 1 change for each field. Hereinafter, the plurality of sub-fields b0,
In the case where b1, b2,. , And the uppermost subfield b7 is arranged substantially at the center of the field.
FIG. 6) and a configuration example of the gas discharge television using the same (FIG. 7) will be described.

FIG. 1 shows a configuration example of a subfield arrangement according to the present invention. Subfields in one field are represented by b1, b3, b5, b7, b6, b4, b2, b0.
And an example of a voltage waveform V _K applied to the first electrode and a voltage waveform V _A applied to the third electrode. The display period of each subfield is the same as that of the prior art shown in FIG. The number of pulses 420 (pulses for display) applied to the third electrode and assigned to each subfield also corresponds to the display period of each subfield. Is the same as In the subfield arrangement of FIG. 1 as well, a change between subfields having low gradation levels, such as a change between b0 and b1 at the time of field switching, is due to a change in a dark display level area. ,
Even if the non-light emitting time is long, the deterioration of the image quality is not noticeable.

FIG. 6 shows another example of the subfield arrangement according to the present invention. That is, subfields within one field are represented by b0, b2, b4, b6, b7, b
5, in a case arranged in the order of b3, b1, showing an example of a voltage waveform V _A applied to the voltage waveform V _K and the third electrode to be applied to the first electrode. In this case, as in the case of the embodiment of FIG. 1, the display period of each subfield is the same as that of each subfield in the prior art of FIG.

FIG. 7 shows an embodiment of the apparatus of the present invention, and shows a specific example of the structure of a gas discharge television. Video signals 810, 820, 830 separated into R, G, B color signals
Are converted from analog signals to digital signals by A / D converters 840, 850, and 860, respectively, and stored in the frame memory 870. The frame memory 8
The readout of the signal from 70 is performed by a dedicated readout ROM 9.
00, it is performed at a timing that matches the time of the subfield array of the present invention. The ROM 900 is operated by a counter 890 that counts a clock signal 880. The counter 890 outputs a V signal (vertical synchronization signal) of a television signal or an H signal (horizontal synchronization signal) as necessary.
Reset using. The signals read from the frame memory 870 are input to the shift registers 1010 and 1030, where the signals are subjected to serial-parallel conversion, and then converted into high-voltage signals necessary for driving the panel 800 by the second electrode drivers 1020 and 1040. Then, it is input to the second electrode of the panel. In the embodiment shown in FIG. 7, the device configuration is a two-row simultaneous driving system in which the second electrode is driven separately in the upper half and the lower half of the panel. It is provided in.

On the other hand, a signal input to the first electrode (FIG. 1,
The logic signal V _K in FIG. 6) is generated by the ROM 920 and is shifted by 1H in the shift register 98.
0, 970, and after serial-parallel conversion, the signals are converted into high-voltage signals by the drivers 1000, 990 and input to the first electrode of the panel.

The signal input to the third electrode (FIG. 1,
The logic signal V _A in FIG. 6) is generated by the ROM 910 and is shifted by 1H in a shift register 93.
0, 940, and after serial-parallel conversion, converted into a high voltage signal by drivers 950, 960 and input to the third electrode of the panel.

Although the embodiments of the present invention have been described with reference to a gas discharge television, the scope of the present invention is not limited to this.
In addition, for example, an EL display device, a liquid crystal display device, a fluorescent display tube, and the like, such as a matrix panel that digitally performs luminance modulation by a pulse width or the number of pulses are also included.

[0037]

According to the present invention, it is possible to improve the image quality of moving images under a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a subfield arrangement according to the present invention.

FIG. 2 is a sectional view of a cell of the gas discharge panel.

FIG. 3 is a diagram showing wiring of a gas discharge panel.

FIG. 4 is a diagram illustrating driving of a gas discharge panel.

FIG. 5 is an explanatory diagram of a conventional gradation display technique.

FIG. 6 is a diagram showing another embodiment of a subfield arrangement according to the present invention.

FIG. 7 is a diagram showing one embodiment of the apparatus of the present invention.

[Explanation of symbols]

220: first electrode, 230: second electrode, 240: third electrode, 250: display discharge space, 270: auxiliary discharge space, 400: first electrode address pulse.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shinichi Shinada, Inventor Shinichi Shinagawa 1-280, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. Inside the Central Research Laboratory, Hitachi, Ltd. (72) Inventor F.S. C. Curzon 1-280 Koikurakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Kuni Kitagawa 3681 Hayano, Mobara-shi, Chiba Hitachi Device Engineering Co., Ltd

Claims (8)

[Claims] In a display device for displaying an image having a gradation by a subfield, a plurality of subfields formed within one field period are arranged in the order of increasing the number of display pulses assigned to each subfield. An operation sub-field for displaying the display unit in the display sub-field of the array sub-field between the fields adjacent to each other and having an arrangement part and an arrangement part in an ascending order. When the number of display pulses in the succeeding field is switched from the last active subfield to the largest number of active subfields and the gray level rises by one level, the last active subfield in the preceding field becomes the same as the display pulse in the subsequent field. It is specially arranged that the arrangement order in the field is later than the subfield with the largest number of pulses. Display device. 2. A display device for displaying an image with gradation by subfields, wherein a plurality of subfields formed within one field period are arranged in the order of increasing the number of display pulses assigned to each subfield. An operation sub-field for displaying the display unit in the display sub-field of the array sub-field between the fields adjacent to each other and having an arrangement part and an arrangement part in an ascending order. When the number of display pulses in the subsequent field is switched from the last operation subfield to the operation subfield in which the number of display pulses in the subsequent field is the higher number, and the gradation is increased by one level, the display period of the last operation subfield in the preceding field ends and the subsequent The time interval from the start of the display period of the subfield higher in the number of display pulses in the field is one field. A display device, wherein the display devices are arranged so as to be less than the distance. 3. A display device for displaying an image with gradation by subfields, wherein a plurality of subfields formed within one field period are arranged in the order of increasing the number of display pulses assigned to each subfield. It is arranged having an array portion and an array portion in decreasing order, and at the time of a display operation, between adjacent fields, the gradation is set by an operation subfield for setting the display portion to the display state in the array subfield. When the first gray level of at least approximately 1/2 level or approximately 1/4 level of the highest gray level changes to the second gray level which is one level higher than the first gray level, the second gray level is displayed. Formed by the operation of one subfield having the largest number of display pulses or one subfield having the second largest number of display pulses, and the subfield which is operated last in the preceding field of the first gradation. Ludo,
A display device, wherein the display device is arranged such that the arrangement order in the field is later than the one subfield operated in the subsequent field of the second gradation. 4. A display device for displaying an image with gradation by subfields, wherein a plurality of subfields formed in one field period are arranged in the order of increasing the number of display pulses assigned to each subfield. It is arranged having an arrangement part and an arrangement part in the order of decreasing order, a subfield where the number of display pulses is the largest is arranged between both arrangement parts, and between adjacent fields, the An operation sub-field for bringing the display unit into a display state in the array sub-field, wherein the sub-field is switched from the last operation sub-field in the preceding field to the sub-field having the maximum number of display pulses in the operation sub-field in the succeeding field, and the gradation is changed. Rises one level, the last active subfield in the preceding field is the number of display pulses in the succeeding field. A display device, wherein the display device is arranged such that the arrangement order in the field is rearward of the most subfields. 5. A display device for displaying a gradation image on a display unit by a subfield, wherein a first drive signal for driving a first electrode of the display unit is formed based on an image input signal. A plurality of subfields formed in the field period are arranged with an arrangement portion in which the number of display pulses assigned to each subfield is increased and an arrangement portion in which the number of display pulses is decreased, and are adjacent to each other. Between the combined fields, an operation sub-field for displaying the display portion of the array sub-field is switched from the last operation sub-field in the preceding field to the operation sub-field having the largest number of display pulses in the succeeding field. When the gray level is increased by one level, the last operation subfield in the preceding field corresponds to the number of display pulses in the subsequent field. Means for forming a second drive signal arranged so that the arrangement order in the field is later than the number of sub-fields; and the first drive signal is used for displaying the second drive signal. A display device, comprising: a display unit that controls the driving of the display unit corresponding to the number of pulses and displays a grayscale image corresponding to the driving state. 6. A driving circuit for a display device for displaying a gradation image on a display unit by a subfield, wherein a first driving signal for driving a first electrode of the display unit is provided based on an image input signal. A plurality of sub-fields formed and formed within one field period are arranged so as to have an arrangement portion in which the number of display pulses assigned to each sub-field is increased and an arrangement portion in which the number of display pulses is decreased. A sub-field having the largest number of display pulses is arranged between the two arrangement portions. During a display operation, an operation sub-portion for setting a display portion of the arrangement sub-field to a display state between adjacent fields. Depending on the field, the gradation is at least from the first gradation which is approximately half the highest gradation to the first gradation.
When changing to the second gray level one level higher than the gray level, the second gray level is formed by the operation of the subfield having the largest number of display pulses, and is operated last in the preceding field of the first gray level. Are arranged such that the arrangement order in the field is later than the subfield having the largest number of display pulses that operates in the subsequent field of the second gradation. Means for forming a second drive signal for driving the two electrodes. 7. A display device for displaying a gradation image on a display unit by using subfields, wherein a plurality of subfields formed in one field period have a large number of display pulses assigned to each subfield. An operation sub-field for displaying the display unit in the display state of the array sub-fields between the fields adjacent to each other and having an arrangement portion in the order of When the number of display pulses in the subsequent field is switched from the last operation subfield in the field to the operation subfield having the largest number and the gradation is increased by one level, the display period of the operation subfield having the largest number of display pulses is started. It is arranged so that the display period of the last operation subfield exists within the time range retroactive to one field from. A display device characterized by the following. 8. A gradation display method for displaying an image with gradation on a display section by using subfields, wherein a plurality of subfields formed in one field period are equal to the number of display pulses assigned to each subfield. An operation sub-field for arranging the display unit in the display state of the array sub-field between the fields adjacent to each other and having an arrangement part in an order of increasing and an arrangement part in an order of decreasing. When the number of display pulses in the succeeding field is switched from the last working subfield in the preceding field to the largest operating subfield in the succeeding field and the gray level rises by one level, the last working subfield in the preceding field becomes It is arranged so that the arrangement order in the field is later than the subfield where the number of display pulses is the largest in the field. Forming a display section driving signal, controlling the display time of the display section based on the number of display pulses of the display section driving signal, and displaying an image with gradation on the display section. Gradation display method.