JP2877142B2 - Display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the display of gradation of an image, and to a technique for controlling the gradation of an image by the display time of a display element.

[0002]

2. Description of the Related Art Conventionally, as a technique for controlling a display time of a display element to perform gradation display, there are, for example, (1) Kaji et al.
(1973-03) (1973.3.12) There is a technology for a memory-type plasma display described in “Display of Halftone Moving Image by AC-Type Plasma Display”. This is because a fixed display time (for example, one field of a television signal) is distributed in time corresponding to a display period of each subfield of a binary code, and the display time is controlled by controlling whether or not each subfield operates. To control the gradation of the image. Further, as a television-related technique for displaying a gradation by time division, (2) Murakami et al .: Journal of the Institute of Television Engineers of Japan, vol. 38, no. 9
(1984) "Color TV display using an 8-type pulse memory type discharge panel" and (3) Kogami et al .: Technical Report of the Institute of Television Engineers of Japan, vol. 13, No. 58 (1989)
"Recovering reactive power from Townsend light-emitting gas discharge television"
There is one described in.

In the former ((1)), as shown in FIG.
One field is divided into eight subfields, and scanning and display of each subfield (b7 to b0) are performed in this subfield.

In the latter ((2) and (3)), as shown in FIG. 10, one field is divided into eight time regions (b0 to b7) each having a length corresponding to each subfield of a binary code.
The scanning is shifted by 1H (horizontal scanning period) for each line, and the scanning pulse for the line address is slightly shifted in each subfield so that the selection of the line in each subfield does not become two lines at the same time.

[0005]

In the above prior art, the image quality deterioration of the gradation display such as flicker may not be visually recognized depending on the device specification, but when the display screen becomes large or the luminance becomes low. When the height of the moving image becomes high or when the moving image has a moving image, the disturbance of the gradation such as flicker is recognized. In the display technique of FIG. 9, the display screen is dark because the light emission time between one field is short. Therefore, no disturbance in the gradation is recognized. Further, in the display technique of FIG. 10, since the number of scanning lines is small, details of an image cannot be visually recognized. Therefore, also in this case, no disturbance in the gradation is recognized. However, for example, in a 40-inch class large-sized gas discharge television in which the brightness and the screen size are higher than those cases, the maximum brightness of the image is set to 50 fL (# 171c
d / m ² ) or more, and when an image is displayed in the same manner as in the above-described conventional technique, significant gradation disturbance occurs in a moving image. For example, in displaying a person's face, when the face moves, a phenomenon occurs in which a white streak runs on the cheek. In other words, in a smooth gradation display, when a display image moves (a so-called moving image), a streak is generated in the screen, and it is as if a certain gradation subfield is missing. This is a phenomenon that cannot be seen in a conventional cathode ray tube or the like.

[0006] Such disturbance of gradation in a moving image is caused by instantaneous flicker of a specific pattern in time-division gradation display. This will be described below using the conventional gray scale display technique of FIG.

FIG. 10 shows an example of a gray scale display of 256 gray scales (8-bit gray scale). For example, at the 127 gradation level, subfields b0 to b6 are activated, that is, the first half of one field emits light, and at the 128 gradation level at which the gradation of the next field is increased by one level, b7 is activated, ie, the second half of the field is activated. Moreover, part of the light is emitted.
That is, the operating position of the operating subfield changes greatly from the first half to a part of the second half in the field just by increasing the gradation by one level. The instantaneous light emission cycle at this time is from the light emission start time of the subfield b0 in the preceding field to the light emission start time of the subfield b7 of the succeeding field, and the time interval is 25 msec. This cycle 2
Flicker occurs for 5 msec, which causes disturbance of gradation. When the image is a moving image, the gradation is disturbed one after another in a cell of the screen, and appears as a streak that can be visually recognized clearly.

Next, the principle of the time-division gradation technology including the flicker will be described. As a human visual characteristic, luminance L
It is known that the brightness sensation L when an image is displayed by alternately repeating 1 for t1 seconds and luminance L2 for t2 seconds is represented by L = (t1L1 + t2L2) / (t1 + t2) (Talbot- Plateau's Law (Television Handbook, Volume 1, Section 3.4, 55
page)). However, this rule is satisfied when flicker is not felt (called fusion time).

FIG. 11 shows a critical fusion cycle of visual characteristics when a luminance is changed by changing a white display emission time width using a memory type gas discharge television, that is, turning on and off a light emitting element at a constant luminance. The measurement result of a cycle in which flicker cannot be identified when lighting is repeated at a constant cycle is shown. In the figure, the upper broken line indicates the last subfield (b0) of the next field from the start of the display period of the first subfield (b7) in the field by the gradation display technique of FIG.
(In the example of FIG. 9, one field is equally divided into eight subfields). Also, the broken line in the lower part of FIG. 11 indicates the first sub-field b in the field by the gradation display technique shown in FIG.
A time interval from the start of the display period of 0 to the start of the display period of the last subfield b7 in the next field (in the example of FIG. 10, the display period of each 8-bit subfield in one field is 1: 2: 4...: 128). As can be seen from FIG.
In the conventional gray scale display technique of 0, when the luminance is several fL or more, the interval from the start of the display period of the first subfield in a certain field to the start of the display period of the last subfield in the next field is the critical value. Beyond the fusion cycle.
Therefore, when the light emission of each subfield changes as in the case of a moving image, instantaneous flicker is felt particularly on a bright screen, and gradation is disturbed. Usually, since the average luminance required for the display device is 50 fL or more,
It is desirable that the critical fusion cycle of the visual characteristics is set to 20 msec or less, but if the value is in the vicinity of this value, even if the value exceeds this value, the disturbance of the gradation is improved.

Further, in the above-mentioned prior art, the utilization rate of the time within one field as the light emission time is poor, that is, since the light emission time is short, the brightness of the screen is reduced.

An object of the present invention is to improve the disadvantages of the prior art, and to provide a technique capable of suppressing the disturbance of gradation even for a moving image or a high-luminance image.

[0012]

In order to achieve the above object, the present invention provides: (1) a subfield weighted by a display pulse;
In a display device that displays an image with a used gradation,
All subfields in one field used for level formation
And subfields of the same weight level
In each case.

(2) Sub weighted by display pulses
For display devices that display images with gradation using fields
In this case, all the cells in one field used for forming the gradation level
Subfields with all subfields of the same weight level
There are a plurality of weight levels, and
Bell subfields with other weight levels in between
Arrange to be arranged by.

(3) Sub weighted by display pulse
For display devices that display images with gradation using fields
In this case, all the cells in one field used for forming the gradation level
Subfields with all subfields of the same weight level
There is a plurality for each weight level and the same weight
Level sub-fields with other weight levels in between
Arrange them so that they are sandwiched .

(4) Sub weighted by display pulse
For display devices that display images with gradation using fields
In this case, all the cells in one field used for forming the gradation level
Subfields with all subfields of the same weight level
There are a plurality of each for each weight level.
Multiple items with different levels arranged in the same order
Are formed .

(5) Sub weighted by display pulse
For display devices that display images with gradation using fields
In this case, all the cells in one field used for forming the gradation level
Subfields with all subfields of the same weight level
There are a plurality of each for each weight level.
Multiple items with different levels arranged in the same order
Are formed, and the plurality of subfields are formed.
At least one of the groups is between adjacent fields
The image is interpolated for each field .

(6) Sub weighted by display pulse
For display devices that display images with gradation using fields
In this case, all the cells in one field used for forming the gradation level
Subfields with all subfields of the same weight level
Each weight level has an even number .

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a principle explanatory diagram for explaining the basics of the present invention. In this case, the number of scanning electrodes is 240, and the signal to be displayed is 8 bits (8 subfields b0, b1,
b2, b3, b4, b5, b6, b7), each subfield is coded by a binary code, and 256 gray scales can be displayed.

In the figure, the vertical axis is the horizontal scanning electrode 2.
Forty rows (the upper half of the display panel), the horizontal axis shows the time for two fields (1/30 second). In this explanatory diagram, the subfields are arranged in one direction of the field without allocating all the time of one field to the emission time,
The rest is free time. In such a configuration, 1
The interval (Tm) between the light emission start time of the subfield b0 that emits light first in the field (display time start time) and the light emission start time of the subfield b7 that emits light last in the next field (display time start time). Is shorter than the critical fusion period of the visual characteristics (about 20 ms). The arrangement order of each subfield does not need to be limited to the illustrated order. Also, the light emission time may be padded on the right or left side of the field. FIG.
When the light-emission order of the subfield is inverted and the order of b7 to b0 is set in the field, the subfield b7
The time interval from the light emission start time (display time start time) to the light emission start time (display time start time) of the next field subfield b6 is determined by the critical fusion cycle (about 20 msec).
c) Make it shorter.

FIG. 2 is a diagram showing an example of a circuit configuration in a gas discharge television device as a display device according to the present invention.
The video signals G, B, and R separated into green (G), blue (B), and red (R) color signals of the television signal are A / D converters 1-1, 1-2, and 1-3, respectively. From the analog signal
Bits (b0, b1, b2, b3, b4, b5, b6,
b7) is converted into a digital signal (binary code) and stored in the frame memory (or field memory) 2. On the other hand, reading out of the frame memory 2 is performed by using a dedicated read-out ROM 5 so as to make a timing suitable for the gradation sub-field. The read ROM 5 is
The operation is performed by the counter 4 that counts the clock signal CLK. The reset of the counter 4 is performed by the V (vertical synchronization) signal of the television signal or the H (horizontal synchronization) signal as necessary.
This is performed using signals. Reading of the frame memory 2 is performed by accessing an address where a subfield signal of each scanning electrode is stored at the timing of each of the subfields b0, b2,. Each subfield signal read from the frame memory 2 is supplied to the shift registers 8 and 11 of the driver circuit for the auxiliary anode of the light emitting element.
And through the drivers 9 and 10, the auxiliary anodes S1, S2, S2 of the light emitting elements constituting the gas discharge panel 3.
, S1 ', S2', S3 ',.

On the other hand, the ROM 6 for the cathode and the ROM 7 for the anode
Respectively use the output of the counter 4 to convert the arrangement signals of the subfields into the shift registers 13, 14 and 17, 18.
Add to Further, shift registers 13, 14, and 1
The signals from 7 and 18 are applied to drivers 15, 16 and 19 and 20, respectively, where the driving signals for the anode and cathode of the light emitting element of the gas discharge panel 3 are generated. The anode of the light emitting element has anode lead wires A1, A2, A3.
A480 are provided, and the cathode is provided with cathode leads K1, K2, K3... K240 and K241. These ROM, shift register and driver constitute a drive circuit for selecting a light emitting element to be displayed. In this embodiment, since the gas discharge panel 3 is divided into upper and lower parts, two scanning electrodes can be driven simultaneously.

FIG. 3 is a partially enlarged view of the gas discharge panel 3, showing electrode wiring of the light emitting element. The gas discharge panel 3 has a plurality of light emitting elements 30 arranged in a matrix of rows and columns. The light emitting element 30 has three electrodes of a cathode, an anode, and an auxiliary anode, and has a memory function. A first electrode lead 32 (k1, k2,... Kl) and a third electrode lead 31 (A1, A2,... Al) are provided on the cathode and anode of each light emitting element 30 in the lateral direction, respectively. S is a vertical auxiliary electrode lead wire 33 (S1, S2, ...)
Is provided. When the gas discharge panel 3 is driven horizontally by dividing the panel into two vertically by setting the number of horizontal scanning electrodes 1 to 480, the auxiliary electrode lead wires 33 are separated at the center of the panel. The first electrode lead wires 32 (k1, k2,...)
kl), the third electrode lead wire 31 (A1, A2,... Al) and the auxiliary electrode lead wire 33 (S1, S2,...) respectively have the cathode driver 19 (or 20) and the anode driver 15 ( Or 16) and a drive signal from the auxiliary anode driver 9 (or 10).

FIG. 4 is a diagram showing a cross section of the light emitting element 30. A first electrode (cathode) 22 is made of Ba, Ni,
It is formed of a material such as LaBa. On the other hand, a third electrode (display anode) 24 is formed on the face plate 28 by a printing technique. The discharge space (display discharge space 25 and auxiliary discharge space 27) shown in the figure is formed, for example, by stacking a number of spacers with holes, and the second electrode (auxiliary anode) 23 shown in the figure is formed. Be placed. When a discharge (display discharge) occurs between the first electrode 22 and the third electrode 24, ultraviolet rays are generated from a gas (a mixed gas such as Xe or Ne-Xe, He-Xe) in the display discharge space 25, and fluorescent light is generated. The light body 26 emits light to perform display. A so-called pilot discharge (auxiliary discharge) is generated between the first electrode 22 and the second electrode 23, and this auxiliary discharge is transferred to a display discharge between the first electrode 22 and the third electrode 24. This is controlled by the presence or absence of a pulse applied to the second electrode 24. Since this auxiliary discharge does not excite the phosphor 26, it does not affect display light emission.

Next, the discharge state between the electrodes will be described with reference to FIG. In FIG. 5, Vk indicates a voltage waveform applied to the first electrode lead line, and 40 indicates a pulse for addressing one line of the gas discharge panel 3, which is referred to as a first electrode scanning pulse. In the example of FIG. 5, the pulse width of the first electrode pulse is
Time width Δ assigned to address one line
It is the same as For example, the scanning time of each line is 1H
When 240 lines are addressed in one field (the number of lines in the upper half of a panel driven simultaneously by two lines) and 8-bit gradation display is performed, Δ ≒ 8 μsec. Vs indicates a pulse voltage waveform applied to the second electrode lead,
Reference numeral 1 denotes a second electrode pulse, which has a smaller pulse width than the first electrode scanning pulse 40 and is located behind the time width Δ. This second
The presence / absence of the electrode pulse 41 changes depending on the content of the television signal, that is, “1” and “0” of the subfield signal. VA indicates the waveform of the pulse voltage applied to the third electrode lead wire. For the same line number of the first electrode lead wire and the third electrode lead wire, the width of the voltage applied to the third electrode in FIG. Immediately after the first electrode scanning pulse 40, the narrow pulse 41 is continuously applied by the number of pulses corresponding to the number of gradation bits.

In a period III in the drawing, a pulse 42 having a narrow pulse width is first applied to the third electrode. Since a large number of charged particles are present in the display discharge space 25 due to the switching in the period II, the pulse 42 causes the first electrode and the third
A pulsating discharge occurs between the electrodes. Due to this pulse-like discharge, charged particles are further generated in the display discharge space 25, and the discharge is performed even in the next pulse 43. As described above, in the period III, the discharge continues while the pulse is continuously applied or until a new voltage that stops the discharge is applied to the first electrode. This function is called a pulse memory function. By this pulse discharge, the phosphor 26 of FIG. 4 is excited to perform display light emission.

When the display is not to be emitted, the pulse 41 of the second electrode shown in FIG. 5 is removed. In this case, switching is not performed, and no discharge occurs between the first electrode and the third electrode, so that the number of charged particles in the display discharge space 25 in FIG. 4 is small. Therefore, even if the pulses 42 and 43 are applied to the third electrode, no discharge occurs, and the phosphor 26 in FIG. 4 is not excited.

Therefore, the pulse 41 of the second electrode serves to control the discharge between the first electrode and the third electrode, and the display brightness is controlled by the presence or absence of this pulse.

FIG. 6 is an explanatory diagram for displaying an image on the gas discharge panel 3 in 256 gradations using an 8-bit binary code.
One field in FIG. 1 (about 1 in the case of an NTSC television signal)
/ 60 seconds = 16.7 msec). FIG. 3 shows the voltage waveform Vk applied to the first electrode and the third waveform.
3 shows a voltage waveform VA applied to an electrode. Eight scanning pulses 40 corresponding to subfields are applied to the first electrode during one field. The pulse 42 applied to the third electrode is
As shown in FIG. 5, it starts immediately after the application of the scanning pulse 40 and ends before the next scanning pulse 40 comes. The number of each pulse 42 is determined by the subfields b0, b1,.
6, proportional to the display period of b7, and the time interval ratio is 1:
2: 4: 8...: 128, 2
56 gradations are realized. Control of whether or not to discharge the pulse train of each of the third electrodes includes b0, b1,... B6, b
The pulse of the second electrode corresponding to the scanning pulse of No. 7 (4 in FIG. 5)
It depends on the presence or absence of 1) In FIG. 5, when the light emission in the period II cannot be neglected, the number of pulses of the third electrode is distributed in consideration of the luminance due to the light emission. Here, the absolute number of pulses of the third electrode is set such that the period from the beginning of the subfield b0 in FIG. 6 (start of the display period) to the end of the subfield b6 (end of the display period) is about 3.3 msec. When the value is determined, the critical fusion period described above is set to 20.
(= 3.3 + 16.7) msec, and the disturbance of the gradation for the moving image can be suppressed.

In the configuration shown in FIGS. 1 and 6, the light emission start time of the first subfield in one field (display time start time) and the light emission start time of the last subfield in the next field (display time period) Interval (T)
In order to make m) shorter than the critical fusion period of the visual characteristics, the entire display period is made considerably shorter, but in order to extend the light emission time, at least one of the sub-fields of the binary code structure is divided, Similar effects can be obtained by arranging the divided subfields in a time zone different from the subfield operation time zone in the case of FIGS. 1 and 6, for example, in a vacant time zone in FIGS. Can be obtained.

FIG. 7 shows an embodiment of the present invention. In this embodiment, all the subfields b0 to b
7 are displayed twice, and the first electrode line scanning period に お け る in FIG. 5 is about 4 μsec. In the case of this embodiment,
The two subfield groups may have exactly the same display.
Also, as described with reference to FIG. 8, when one of the two subfield groups is converted into a field-interpolated signal, the image quality of a moving image can be further improved.

FIG. 8 shows an arrangement for field-interpolating two sets of subfields in the subfield arrangement of FIG. 7, ie, one of the two subfield groups. A signal 121 for each field is transmitted via a switch 122 to a first field memory 123 and a second field memory 12.
4 are stored alternately. By the interpolation memory 125, this 2
The signals from the two field memories 123 and 124 are interpolated and stored. The switch 126 extracts the signal 127 of the subfields b0 to b7 every half field.

Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to the above embodiments. For example, the present invention includes a case where the direction of the time axis in the subfield arrangement in FIG. 7 is reversed. In addition, as a display device according to the present invention, a gas discharge television device using a gas discharge light emitting element is typical, but the present invention is not limited to this.

[0034]

According to the present invention, the disturbance of the gradation can be improved without lowering the brightness.

[Brief description of the drawings]

FIG. 1 is a principle explanatory diagram of the present invention.

FIG. 2 is a diagram showing an example of a circuit configuration for an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration example of a gas discharge panel used in an embodiment of the present invention.

FIG. 4 is a sectional view of a light emitting device of a gas discharge panel used in an embodiment of the present invention.

FIG. 5 is a voltage waveform chart for explaining the operation of the light emitting device shown in FIG.

FIG. 6 is a principle explanatory diagram of the present invention.

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

FIG. 8 is a diagram illustrating an example of an interpolation circuit.

FIG. 9 is a diagram showing a conventional example of gradation display.

FIG. 10 is a diagram showing another conventional example of gradation display.

FIG. 11 is a diagram illustrating an example of a measurement result of a critical fusion period.

[Description of Signs] 1 ... A / D converter, 2 ... Frame memory, 3 ... Gas discharge panel, 4 ... Counter, 5, 6, 7 ... ROM, 8, 11, 13, 14, 17, 18 ... Shift register , 9, 10, 15, 16, 19, 20: driver, 21: substrate, 22: cathode, 23: auxiliary anode, 24: display anode, 25: display discharge space, 26: phosphor, 27: auxiliary discharge space Reference numeral 28: face plate, 30: discharge cell (light emitting element), 31: third electrode lead, 32: first electrode lead, 33: second electrode lead, 123, 124: field memory, 125: interpolation memory.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Mutsumi Suzuki 1-280 Higashi Koigabo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory of Hitachi, Ltd. (56) References JP-A-4-1693 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G09G 3/00-3/38 H04N 5/66

Claims (10)

(57) [Claims] In a display device for displaying an image with gradation using subfields weighted by display pulses, all subfields in one field used for forming a gradation level are provided.
Subfields of the same weight level
A display device, wherein a plurality of display devices are provided for each device. 2. A display device for displaying an image having a gradation by using a subfield weighted by a display pulse, wherein all subfields in one field used for forming a gradation level are provided.
Subfields of the same weight level
There is more than one for each
Display device characterized by subfields are arranged in so that disposed across those other weight levels between. 3. A display device for displaying an image with gradation using subfields weighted by display pulses, wherein all subfields in one field used for forming a gradation level.
Subfields of the same weight level
Each of which has the same weight level.
Subfield display device, characterized in that arranged in so that disposed across those other weight levels in between. 4. The method according to claim 1, wherein the subfield having the highest weight level has a small number of subfields.
2. The display device according to claim 1, wherein the display device is arranged at least at one end of the subfield array . 5. The method according to claim 1, wherein the subfield having the highest weight level has a small number of subfields.
Claims located at the center of at least the subfield array
2. The display device according to 1 . 6. The method of claim 1, wherein the subfield of the highest weight level is
請which is arranged on the one end of the field array and substantially in central portion
The display device according to claim 1 . 7.Sub-feature weighted by display pulse
Display device that displays images with gradation using
hand, All sub-fields in one field used for forming gradation levels
Subfields of the same weight level
There are several for each file, and the weight level is
Multiple sub-files in which different
Characterized by forming a field group display
apparatus. 8. The plurality of subfield groups are respectively:
The subfield with the highest weight level within each group is
Claim is disposed on the end of the group of subfield arrangement 7
The display device according to claim 1. 9. A display device for displaying an image with gradation using subfields weighted by display pulses, wherein all subfields in one field used for forming a gradation level are provided.
Subfields of the same weight level
There are several for each file, and the weight level is
Are formed in the same order to form a plurality of subfield groups, and among the plurality of subfield groups,
At least one field between adjacent fields
A display device for interpolating an image for each mode . 10. Sub-field weighted by display pulse
Display device that displays images with gradation using
hand, All sub-fields in one field used for forming gradation levels
Subfields of the same weight level
It is characterized in that there are even numbers for each file
Display device.