JPH1049098A - Display device and driving circuit thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gradation display technique by which the quality of a moving picture is prevented form being deteriorated. SOLUTION: This device is provided with plural sub-fields having display terms whose ratios are 1, 2, 2<2> , 2<3> ,... in a field. Besides, it is provided with a part where the sub-fields are arrayed in such turn that the display terms thereof become longer and a part where they are arrayed in such turn that the display terms thereof become shorter. Then, the sub-fields are arrayed so that the sub-field actuated last in the preceding field is arrayed more delayed than the sub-field actuated first in the following field in the field when gradation is changed to the second gradation in the following field whose level is one-level higher than the first gradation obtained by combining five or more sub-fields in the preceding field from the first gradation between the adjacent fields.

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 order in the prior art, the moving picture quality is degraded, and the moving picture may appear to be grayed-out or the pixels may 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 subfield b0, b1, b2,... B
7 is 1: 2: 4: 8:...: 128 corresponding to the subfields b0, b1, b2,. The 256 gray scales of the hexadecimal code are configured. This third
It is determined whether or not the panel is to be discharge-displayed by the voltage of the pulse train 420 applied to the electrodes.
.. In the period corresponding to the address pulse 400 within the second electrode pulse (410 in FIG. 4).

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]

To achieve the above object, according to the solution to ## in the present invention, as the basic configuration, the ratio is 1,2,2 ^2, 2 ³ of the display period, the ... plurality of subfields of a field Having a plurality of sub-fields, the sub-fields have an arrangement portion arranged in the order of increasing the display period of the sub-field and an arrangement portion arranged in the order of decreasing the length, and, between adjacent fields, When the gray level changes from the first gray level of a combination of five or more subfields in the preceding field to the second gray level in the succeeding field that is one level higher than the first gray level, The subfield that operates last in the preceding field is arranged so that the arrangement order in the field is later than the subfield that operates first in the subsequent field.

A plurality of subfields in the field
In the arrangement configuration having a portion arranged in the order of increasing display period and a portion arranged in the order of decreasing display period, the subfields of the display period of each length are dispersedly arranged in each field. The configuration of the dispersed arrangement and the switching between the last operation subfield in the preceding field to the first operation subfield in the succeeding field, which is the longest display period, between adjacent fields, thereby increasing the gradation by one level. The configuration in which the last operation subfield in the preceding field is arranged so that the order thereof is later in the field than the subfield of the longest display period in the subsequent field is ,
In particular, in the gray level change of the halftone level, from the end of the display period of the sub-field corresponding to the gray level before the level change in the preceding field after the last operation, the subfield after the level change in the subsequent field The time until the start of the display period of the first operation subfield among the subfields corresponding to the gradation level is shortened, and the time difference between the two points is always 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 apparent from the above, in order to improve the image quality deterioration, basically, a plurality of subfields may be arranged in an order in which display periods are dispersed. In this arrangement, even if the level 127 and the level 128 in the above Table 1 change from field to field, 1
The light emission period always exists within the field period. Hereinafter, the plurality of subfields b0, b1, b2
.. B7 are used, and the subfields are arranged on both sides of the uppermost subfield (the longest display period subfield (b7 in the above example)) and subfields b5 and b6 of a shorter display period. Configuration example of a distributed subfield array in which the uppermost subfield b7 is arranged substantially at the center of the field (FIGS. 1 and 6).
And a configuration example of the gas discharge television using the same (FIG. 7).

FIG. 1 shows a configuration example of a subfield arrangement according to the present invention. A sub-field in one field b1, b3, b5, b7, b6, b4, b2, when arranged in the order of b0, is applied to the voltage waveform V _K and the third electrode to be applied to the first electrode An example of a voltage waveform _VA is shown. The display period of each subfield is the same as that of the prior art shown in FIG. The number of pulses 420 applied to the third electrode also corresponds to the display period of each subfield, and is the same as in the case of the prior art in FIG. In the subfield arrangement of FIG. 1 as well, a change between subfields with low gradation levels, such as a change between b0 and b1 at the time of field switching, is a change in a dark display level range. Even if the non-light-emitting time becomes long, the image quality does not deteriorate remarkably.

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 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 Continued on the front page (72) Inventor Shinichi Shinada 1-280 Koigakubo, Kokubunji-shi, Tokyo Co., Ltd. Inside the Central Research Laboratory, Hitachi, Ltd. In the Central Research Laboratory (72) Inventor F. C. Curzon 1-280 Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory Co., Ltd.

Claims (5)

[Claims] 1. A display device for displaying an image with gradation using subfields, wherein a plurality of subfields having a display period ratio of 1, ² , 22 ² , 2 ³ ,. The plurality of sub-fields has an arrangement portion arranged in the order of increasing the display period of the sub-field and an arrangement portion arranged in the order of decreasing length, and between adjacent fields, the gradation is
When changing from the first gradation by the combination of five or more subfields in the preceding field to the second gradation in the succeeding field that is one level higher than the first gradation, the last in the preceding field The active subfield is greater than the first active subfield in the subsequent field.
A display device characterized by being arranged such that the arrangement order in a field is on the rear side. 2. A display device for displaying an image having a gradation by causing a matrix panel to emit light using a display period of a subfield, a memory means for holding an image input signal, and a first signal from the memory means. Control means for reading in accordance with the subfield; first drive signal output means for forming and outputting a first drive signal for driving a first electrode of the matrix panel from the first signal; ratio 1,2,2 ^2, 2 ^3, has a ... plurality of subfields in the field, several subfields plurality is shorter and sequence portion display period of sub-fields are arranged in order of longer And an array portion arranged in a certain order, and between the fields adjacent to each other, the gradation is
When changing from the first gradation by the combination of five or more subfields in the preceding field to the second gradation in the succeeding field that is one level higher than the first gradation, the last in the preceding field The active subfield is greater than the first active subfield in the subsequent field.
Array information output means for outputting an information signal arranged so that the arrangement order in the field is on the rear side; and forming a second drive signal for driving a second electrode of the matrix panel from the information signal. A second drive signal output means for outputting, and for each subfield, the panel unit is selected by the first drive signal between a light emitting state and a non-light emitting state according to the second drive signal, and A display device, comprising: a matrix panel in which a light emission period of the light emission of the panel unit is controlled by a drive signal, and a grayscale image corresponding to the light emission period is displayed. 3. A display device in which a matrix panel emits light by using a display period of a subfield to display an image having a gradation, wherein a first electrode for driving a first electrode of the matrix panel based on an image input signal. first means for forming a drive signal, the ratio of the display period 1,2,2 ^2, 2 ^3, has a ... plurality of subfields in the field, several subfields plurality subfields Has an array portion arranged in the order of increasing display period and an array portion arranged in the order of decreasing length, and between adjacent fields, the gradation is
When changing from the first gradation by the combination of five or more subfields in the preceding field to the second gradation in the succeeding field that is one level higher than the first gradation, the last in the preceding field The active subfield is greater than the first active subfield in the subsequent field.
Second means for forming a second drive signal for driving a second electrode of the matrix panel from information signals arranged such that the arrangement order in the field is on the rear side; and the first drive And a matrix panel for controlling light emission of the panel unit by the second drive signal by a signal, and displaying a gradation image corresponding to a light emission period of the controlled light emission on the panel unit. Display device. 4. A display device for driving a display unit using a display period of a subfield to display an image having a gradation, wherein a first electrode for driving a first electrode of the display unit based on an image input signal. forming a drive signal, and the ratio is 1,2,2 ^2, 2 ³ of the display period, has a ... plurality of subfields within a field, the plurality several subfields, the display period of the subfields Has an array portion arranged in the order of increasing length and an array portion arranged in the order of decreasing length, and between the fields adjacent to each other, the gradation is determined by a combination of five or more subfields in the preceding field. When changing from one gray level to a second gray level in a succeeding field that is one level higher than the first gray level, the last activated subfield in the preceding field is activated first in the subsequent field. Do Means for forming a second drive signal for driving a second electrode of the display unit from an information signal arranged such that the arrangement order in the field is later than that of the first field; A display unit that controls driving of the display unit by the second drive signal with the drive signal, and displays an image having a gradation corresponding to the drive state. 5. A driving circuit of a display device for displaying a gradation image by causing a matrix panel to emit light in a display period of a subfield, wherein a memory means for holding an image input signal and a driving means for driving an electrode of the matrix panel are provided. an information signal to form a first driving signal, the ratio of the display period 1,2,2 ^2, 2 ^3, has a ... plurality of subfields within a field, the plurality several subfields Has an array portion arranged in the order of increasing the display period of the subfield and an array portion arranged in the order of decreasing the length of the display period of the subfield. Changes from the first gradation by the combination of the subfields to the second gradation in the succeeding field which is higher by one level than the first gradation, and finally operates in the preceding field. Array information output means for outputting an information signal in which the subfields are arranged so that the arrangement order in the field is later than the subfield which operates first in the subsequent field; and Control means for reading a second signal for forming a second drive signal for driving a second electrode of the matrix panel in accordance with the subfield.