JP2002032054A - Display device and display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device and a display method capable of displaying a video signal having a different field frequency while suppressing flicker. SOLUTION: In a plasma display device capable of displaying a video signal whose field frequency is 60 Hz, a surplus time to be generated when the device receives a video signal whose field frequency is 50 Hz is distributed among plural sub-fields in one field. The time interval among sub-fields is not broadened in a group G1 including sub-fields sf 1 to sf 6 whose weights are small, but the time interval among sub-fields is broadened in a group G2 including sub-fields sf 7 to sf 12 whose weights are large. In this case, the surplus time is divided equally by the number of sub-fields sf 7 to sf 12 in the group G2 to be inserted among the sub-fields sf 7 to sf 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention divides one field into a plurality of subfields arranged on a time axis in a predetermined order, weights each subfield in correspondence with a gradation level, and applies a weight to a video signal. The present invention relates to a display device and a display method for performing gradation display by causing pixels on a display panel to emit light or not to emit light according to each subfield.

[0002]

2. Description of the Related Art A plasma display device using a plasma display panel has the advantage that it can be made thinner and larger. In this plasma display device, an image is displayed by utilizing light emission at the time of discharge of a discharge cell constituting a pixel. Further, in the plasma display panel, in order to emit light in a binary manner, a subfield method of displaying a halftone by temporally overlapping a plurality of weighted binary images is used.

In this subfield method, different grayscale levels are obtained by changing the length of time during which a discharge cell emits light or the number of light emission pulses within a time during which a visual afterimage effect can be used, that is, within one field period.

[0004] Specifically, one field is time-divided into a plurality of subfields, and each subfield is weighted. The weight of each subfield corresponds to the light emission amount of each subfield. For example, the number of light emission pulses is used as a weight, and the total amount of the weights of the subfields in one field corresponds to the luminance of the video signal, that is, the gradation level. I do.

[0005] For example, if one field includes eight subfields, each subfield is 1, 2, 4, 8, 16, 32, 64 and 128 according to a binary system.
Are assigned weights corresponding to the luminance levels.

FIG. 11 is a schematic diagram showing an example of a subfield division method when a video signal having a field frequency of 60 Hz is received.

As shown in FIG. 11, the time of one field is 1/60 second. One field is divided into 12 subfields sf1 to sf12. Different weights are assigned to the subfields sf1 to sf12. In this case, the weight is represented by the number of light emission pulses. A gradation display can be performed by selecting and combining subfields in which discharge cells should emit light from the 12 subfields sf1 to sf12.

In a video signal having a field frequency of 60 Hz, a flicker component having a frequency of 60 Hz is generated. However, flicker components of 60 Hz or higher are hardly recognized by human eyes, and do not lead to deterioration of image quality.

Incidentally, not only a video signal having a field frequency of 60 Hz but also a PAL (phase alternation by Lin)
As shown in e), a plasma display device capable of displaying a video signal having a field frequency of 50 Hz is being developed.

FIG. 12 shows a case where a video signal having a field frequency of 50 Hz is received in a plasma display device capable of displaying a video signal having a field frequency of 60 Hz.
It is a schematic diagram which shows the arrangement of subfields within a field.

As shown in FIG. 12, when a video signal having a field frequency of 50 Hz is received, the time of one field is increased to 1/50 second. When displaying a video signal having a field frequency of 50 Hz without changing the configuration of each subfield, a surplus time S occurs after the end of the last subfield sf12 in one field.

In this case, since the field frequency is as low as 50 Hz, a flicker component having a frequency of 50 Hz is generated. As described above, a flicker component of 60 Hz or higher is hardly recognized by human eyes, but a flicker component of 50 Hz is easily perceived.

Therefore, if the field frequency is doubled to 100 Hz by signal processing and the emission frequency is doubled, flicker will not be felt. Also, without changing the field frequency, the speed of light emission is increased, the number of subfields is doubled, and even if the number of times of light emission is doubled, flicker can be similarly suppressed.

However, in the plasma display device, there is a limit in increasing the speed due to the discharge characteristics of the discharge cells.
The maximum value of the field frequency or the maximum number of subfields is also limited.

Therefore, it is desired to be able to suppress the perceived flicker without converting the field frequency or the number of subfields when a video signal having a field frequency of 50 Hz is received.

On the other hand, when the above-described subfield method is used, since the viewer's line of sight follows the moving image, the temporal integration region of the eyes changes spatially, and a unique pseudo contour shape for the moving image is obtained. Noise is observed. This noise is called a moving image pseudo contour and causes image quality to deteriorate. When suppressing flicker, it is necessary to consider suppressing the increase in the moving image pseudo contour.

An object of the present invention is to provide a display device and a display method capable of displaying video signals of different field frequencies while suppressing flicker.

[0018]

Means for Solving the Problems (1) First invention A display device according to the first invention is configured to be capable of displaying a plurality of types of video signals having different field frequencies, and comprises:
A display device that divides a field into a plurality of sub-fields, weights each sub-field with luminance, and performs gradation display by a combination of light emission in each sub-field. Means for judging the field frequency, and 1 according to the change of the field frequency in accordance with the result of the judgment of the field frequency by the judgment means
When a surplus time other than a plurality of sub-fields occurs in a field, the surplus time is distributed among the plurality of sub-fields in one field to control a time interval between the plurality of sub-fields in one field. And field interval control means.

In the display device according to the present invention, the field frequency of the input video signal is determined by the determining means. When the field frequency becomes low, extra time other than a plurality of subfields occurs in one field. Therefore, when a surplus time other than a plurality of subfields occurs in one field due to a change in the field frequency in accordance with the determination result of the field frequency, the surplus time is controlled by the subfield interval control means in the one field. The time interval between the subfields in one field is controlled.

Accordingly, when the field frequency is low, a plurality of subfields are dispersedly arranged in one field, and the temporal concentration of the emission energy is reduced. As a result, the occurrence of a flicker that can be felt is suppressed.

(2) Second invention In the display device according to the second invention, in the configuration of the display device according to the first invention, the subfield interval control means sets the surplus time to a plurality of subfields in one field. The time interval between a plurality of subfields is extended by distributing them evenly between them.

In this case, a plurality of subfields are distributed and arranged at equal time intervals within one field. This suppresses the generation of flicker components at all gradation levels.

Further, since the amount of distribution can be calculated by simply dividing the surplus time, the circuit scale of the subfield interval control means can be reduced.

(3) Third Invention In the display device according to the third invention, in the configuration of the display device according to the first invention, the subfield interval control means sets the surplus time to a plurality of subfields in one field. The time interval between a plurality of sub-fields is extended by distributing the data among a plurality of sub-fields in accordance with the weights of the luminances.

In this case, a plurality of subfields are distributed in one field according to the weight. That is, the time interval between subfields having a large weight is larger than the time interval between subfields having a small weight. This suppresses a flicker component of a high gradation level that is easily perceived.

On the other hand, the time interval between subfields having small weights which does not significantly contribute to the occurrence of perceived flicker is not extended as compared with the time interval between subfields having large weights. The increase in occurrence is suppressed.

(4) Fourth invention In a display device according to a fourth invention, in the configuration of the display device according to the first invention, the subfield interval control means converts the plurality of subfields into subfields having a small weight. The first group including the first group and the second group including subfields having a larger weight than the first group, and by distributing the surplus time evenly among the subfields in the second group, the second group is included. The time interval between a plurality of subfields of the group is extended.

In this case, a plurality of sub-fields in one field are divided into a first group including a sub-field with a small weight and a second group including a sub-field with a large weight. The time interval between fields is extended. That is, the time interval between subfields having a large weight is larger than the time interval between subfields having a small weight. This suppresses a flicker component of a high gradation level that is easily perceived.

On the other hand, the time interval between subfields having a small weight that does not significantly contribute to the occurrence of a perceived flicker is not extended as compared with the time interval between subfields having a large weight. The increase in occurrence is suppressed.

Further, since the amount of distribution can be calculated by simply dividing the surplus time by the number of subfields of the second group, the circuit scale of the subfield interval control means can be reduced.

(5) Fifth Invention The display device according to the fifth invention is the display device according to any one of the first to fourth inventions, wherein each of the sub-devices corresponds to the level of an input video signal. Weighting control means for changing the weight of the luminance of each subfield by changing the number of light emission pulses in the field is further provided. The subfield interval control means includes a plurality of subfields within one field which are changed by the weighting control means. When a surplus time other than a field occurs, the surplus time is distributed among a plurality of subfields to control a time interval between the plurality of subfields in one field.

In this case, the luminance weight of each subfield changes by changing the number of light emission pulses in each subfield according to the level of the input video signal.
Thereby, adaptive luminance control is performed. If the number of light emission pulses in each subfield changes in this adaptive brightness control, a surplus time other than a plurality of subfields occurs in one field. Also in this case, the surplus time is distributed among a plurality of subfields within one field, and the time interval between the plurality of subfields within one field is controlled.

Accordingly, when the number of light emission pulses is small, a plurality of subfields are dispersedly arranged in one field, and the temporal concentration of light emission energy is reduced. As a result, the occurrence of a flicker that can be felt is suppressed.

(6) Sixth invention A display device according to a sixth invention is the display device according to any one of the first to fifth inventions, wherein a plurality of types of video signals having different field frequencies are A first video signal having a first field frequency and a second video signal having a second field frequency lower than the first field frequency;
When the first video signal is input, one field is divided into a plurality of subfields, and when the second video signal is input, the first
The surplus time generated by the change from the field frequency to the second field frequency is distributed among a plurality of subfields within one field.

When the first video signal is input, the surplus time in one field is short because the field frequency is high.
On the other hand, when the second video signal is input, the surplus time in one field becomes longer because the field frequency is low. In this case, the surplus time is distributed among the plurality of subfields within one field, so that the plurality of subfields are distributed. As a result, the temporal concentration of the light-emitting energy is reduced, and the occurrence of flicker that can be felt is suppressed.

(7) Seventh Invention A display device according to a seventh invention is the display device according to the sixth invention, wherein the first field frequency is 60 Hz.
And the second field frequency is 50 Hz.

Although a flicker component of 60 Hz or higher is hardly recognized by human eyes, a flicker component of 50 Hz is easily perceived. Therefore, when displaying a video signal having a field frequency of 50 Hz, a plurality of sub-fields are dispersedly arranged in one field, thereby alleviating temporal concentration of luminescent energy and suppressing occurrence of flicker that is perceived. Becomes possible.

(8) Eighth Invention The display method according to the eighth invention divides one field into a plurality of subfields, weights each subfield with luminance, and determines whether or not light emission occurs in each subfield. A display method for performing gradation display by a combination, wherein a step of determining a field frequency of an input video signal,
When a surplus time other than a plurality of subfields occurs in one field due to a change in the field frequency according to the determination result of the field frequency, the surplus time is allocated to a plurality of subfields in one field.
Controlling the time interval between a plurality of subfields within the field.

In the display method according to the present invention, the field frequency of the input video signal is determined. When the field frequency becomes low, extra time other than a plurality of subfields occurs in one field. Therefore, when a surplus time other than a plurality of subfields occurs in one field due to a change in the field frequency according to the determination result of the field frequency, the surplus time is distributed among the plurality of subfields in one field and 1 The time interval between a plurality of subfields within a field is controlled.

Thus, when the field frequency is low, a plurality of subfields are dispersedly arranged in one field, and the temporal concentration of the emission energy is reduced. As a result, the occurrence of a flicker that can be felt is suppressed.

(9) Ninth Invention In a display method according to a ninth invention, in the display method according to the eighth invention, the step of controlling is such that a surplus time is evenly set between a plurality of subfields in one field. Extending the time interval between the plurality of subfields by allocating.

In this case, a plurality of subfields are distributed and arranged at equal time intervals within one field. This suppresses the generation of flicker components at all gradation levels.

Also, since the distribution amount can be calculated by simply dividing the surplus time, the circuit scale can be reduced.

(10) Tenth invention In a display method according to a tenth invention, in the display method according to the eighth invention, the step of controlling comprises: setting the surplus time to a luminance weight of a plurality of subfields in one field. And extending the time interval between the plurality of subfields by allocating the subfields between the plurality of subfields in accordance with the following.

In this case, a plurality of sub-fields are distributed in one field according to the weight. That is, the time interval between subfields having a large weight is larger than the time interval between subfields having a small weight. This suppresses a flicker component of a high gradation level that is easily perceived.

On the other hand, the time interval between sub-fields with small weights that does not significantly contribute to the occurrence of perceived flicker is not extended as compared with the time interval between sub-fields with large weights. The increase in occurrence is suppressed.

(11) Eleventh Invention In a display method according to an eleventh aspect of the present invention, in the display method according to the eighth aspect, the controlling step comprises the step of controlling the plurality of subfields to include a first subfield having a small weight. The second group is divided into a group and a second group including sub-fields having a weight greater than that of the first group, and the surplus time is equally distributed among the sub-fields in the second group. Extending the time interval between the sub-fields.

In this case, a plurality of sub-fields in one field are divided into a first group including a sub-field having a small weight and a second group including a sub-field having a large weight. The time interval between fields is extended. That is, the time interval between subfields having a large weight is larger than the time interval between subfields having a small weight. This suppresses a flicker component of a high gradation level that is easily perceived.

On the other hand, since the time interval between subfields with small weights that does not significantly contribute to the occurrence of perceived flicker is not extended as compared with the time interval between subfields with large weights, the pseudo-contour of the moving image at low gradation is low. The increase in occurrence is suppressed.

Further, the amount of distribution can be calculated by simply dividing the surplus time by the number of subfields of the second group, so that the circuit scale can be reduced.

(12) Twelfth Invention The display method according to the twelfth invention is the display method according to any one of the eighth to eleventh inventions, wherein each subfield is provided in accordance with a level of an input video signal. The method further includes the step of changing the weight of the luminance of each subfield by changing the number of light emission pulses of the subfield, and the step of controlling includes: when a change in the weight causes a surplus time other than a plurality of subfields in one field, And controlling the time interval between the plurality of subfields by allocating the surplus time among the plurality of subfields.

In this case, the luminance weight of each subfield changes by changing the number of light emission pulses in each subfield according to the level of the input video signal.
Thereby, adaptive luminance control is performed. If the number of light emission pulses in each subfield changes in this adaptive brightness control, a surplus time other than a plurality of subfields occurs in one field. Also in this case, the surplus time is distributed among a plurality of subfields within one field, and the time interval between the plurality of subfields within one field is controlled.

Thus, when the number of light emission pulses is small, a plurality of subfields are dispersedly arranged in one field, and the temporal concentration of light emission energy is reduced. As a result, the occurrence of a flicker that can be felt is suppressed.

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plasma display device will be described as an example of a display device according to the present invention.
FIG. 1 is a block diagram showing a configuration of a plasma display device according to one embodiment of the present invention.

The plasma display device shown in FIG.
P (plasma display panel) 1, drive circuit 2,
3, 4, a discharge control circuit 5, a synchronous frequency discriminator 6, a subfield interval controller 7, an input signal detector 8, and a video signal processor 9.

The video signal VS is input to the input signal detector 8 and the video signal processor 9. Also, the synchronization signal SY
Is supplied to the discharge control circuit 5 and the synchronization frequency determination unit 6. The synchronization signal SY includes a horizontal synchronization signal and a vertical synchronization signal.

PDP 1 includes a plurality of data electrodes D, a plurality of scan electrodes SCN, and a plurality of sustain electrodes SUS. The plurality of data electrodes D are arranged in the vertical direction of the screen, and the plurality of scan electrodes SCN and the plurality of sustain electrodes SUS are arranged in the horizontal direction of the screen. The plurality of sustain electrodes SUS are commonly connected. A discharge cell 10 is formed at each intersection of the data electrode D, the scan electrode SCN, and the sustain electrode SUS,
Each discharge cell 10 forms a pixel on the screen.

The video signal processing section 9 converts the video signal VS into image data and supplies it to the drive circuit 4. The input signal detector 8 detects the level of the video signal VS, and supplies the detection result to the subfield interval controller 7. Synchronous frequency discriminator 6
Determines the field frequency of the video signal VS based on the synchronization signal SY, and supplies the result of the determination to the subfield interval control unit 7. In the present embodiment, the synchronization frequency determination unit 6
Determines whether the field frequency of the video signal VS is 60 Hz or 50 Hz.

The discharge control circuit 5 includes an initialization pulse generator 51 for generating an initialization pulse, a write pulse generator 52 for generating a write pulse, a sustain pulse generator 53 for generating a sustain pulse, and an eraser for generating an erase pulse. A pulse generation circuit 54 is included.

The discharge control circuit 5 includes an initialization pulse generated by the initialization pulse generation circuit 51 in synchronization with the synchronization signal SY, a write pulse generated by the write pulse generation circuit 52, and a generation pulse generated by the sustain pulse generation circuit 53. The supplied sustain pulse and the erase pulse generated by erase pulse generating circuit 54 are sequentially applied to drive circuit 2, and the sustain pulse generated by sustain pulse generating circuit 53 is applied to drive circuit 3.

The discharge control circuit 5 has a field frequency of 60
When the video signal VS of 1 Hz is received, one field is divided into 12 sub-fields sf1 as shown in FIG.
To sf12. When the discharge control circuit 5 receives the video signal VS having the field frequency of 50 Hz, the discharge control circuit 5 controls the time interval between the subfields according to the control of the subfield interval control unit 7 to thereby control the 12 subfields in one field. The fields sf1 to sf12 are distributed and arranged by a method described later.

The drive circuit 4 selectively drives the plurality of data electrodes D based on the image data provided from the video signal processing section 9 during the writing period of each subfield. The drive circuit 2 sequentially drives the plurality of scan electrodes SCN in response to an initialization pulse, a write pulse, and a sustain pulse sequentially applied from the discharge control circuit 5 in each subfield. The driving circuit 3 controls the discharge control circuit 5 in each subfield.
Drives a plurality of sustain electrodes SUS in response to a sustain pulse and an erase pulse provided from the semiconductor device.

The sub-field interval control unit 7 controls a plurality of sub-fields formed by the discharge control circuit 5 based on the detection result of the video signal level by the input signal detection unit 8 and the determination result of the frequency by the synchronization frequency determination unit 6. Control the time interval between.

In this embodiment, the synchronous frequency discriminating section 6 corresponds to discriminating means, the discharge control circuit 5 and the subfield interval controlling section 7 correspond to interval controlling means, and the discharge control circuit 5 and the input signal detecting section 8 Corresponds to the weight control means.

FIG. 2 is a schematic diagram showing a first example of a subfield arranging method at the time of receiving a video signal having a field frequency of 50 Hz in the plasma display device of FIG.

As shown in FIG. 2, one field includes 12 subfields sf1 to sf12. In this example,
The twelve subfields sf1 to sf12 are distributed and arranged at equal intervals in one field so that the time interval d between the twelve subfields sf1 to sf12 becomes equal. In this case, a surplus time S (see FIG. 12) generated when the field frequency changes from 60 Hz to 50 Hz is equally divided by the number of subfields sf1 to sf12 and inserted between the subfields sf1 to sf12. Thereby, the subfields sf1 to sf1 are changed according to the change in the field frequency.
The time interval d between sf12 also changes.

In this example, a plurality of subfields sf1
By dispersing the sf12 in one field, the temporal concentration of the emission energy is reduced. As a result, the occurrence of a flicker that can be felt is suppressed.

FIG. 3 is a schematic diagram showing a second example of a subfield arranging method when receiving a video signal having a field frequency of 50 Hz in the plasma display device of FIG.

In this example, 12 subfields sf1
The twelve subfields sf1 to sf12 are distributed and arranged according to the weight ratio in one field so that the time interval between sf12 and sf12 increases in proportion to the weight (gray level). That is, the time interval between subfields having a low gradation level is small, and the time interval between subfields having a high gradation level is large. In this case, the surplus time S generated by changing the field frequency from 60 Hz to 50 Hz is proportionally distributed according to the subfield weight,
It is inserted between the subfields sf1 to sf12.

In this example, since a flicker component having a high gradation level is more easily perceived, the perceived flicker component can be sufficiently suppressed by increasing the time interval between subfields having a large weight. . In addition, by not greatly increasing the time interval between subfields having a low weight that does not significantly contribute to the occurrence of a perceived flicker, it is possible to suppress an increase in the occurrence of a moving image false contour at a low gradation.

For example, a moving image pseudo-contour generated in an image having a smooth gradation like human skin is conspicuous, and a sub-field having a small weight that contributes to a smooth gradation expression is not dispersed, so that the moving-image pseudo-contour is not dispersed. An increase in occurrence can be suppressed.

FIG. 4 is a schematic diagram showing a third example of a subfield arranging method at the time of receiving a video signal having a field frequency of 50 Hz in the plasma display device of FIG.

In this example, 12 subfields sf1
To sf12 are replaced by six subfields sf1 having small weights.
To sf6 and a group G2 including six subfields sf7 to sf12 having a large weight. Six subfields sf1 to s with small weight
In the group G1 of f6, the subfields sf1 to sf
In a group G2 including six subfields sf7 to sf12 having a large weight without extending the time interval d1 between the six,
The time interval d2 between the subfields sf7 to sf12 is increased. In this case, the field frequency is from 60 Hz to 50
The surplus time S generated by changing to Hz is divided into six equal parts, and inserted into the subfields sf7 to sf12 of the group G2.

Also in this example, by suppressing the flicker component having a high gradation level, the occurrence of the flicker that can be sensed can be mainly suppressed. In addition, by not greatly increasing the time interval between subfields having a small weight that does not significantly contribute to the occurrence of a perceived flicker, it is possible to suppress an increase in the occurrence of a moving image false contour at a low gradation.

In the examples shown in FIGS. 2 and 4, it is easy to calculate the time interval between subfields from the surplus time S.
The circuit scale of the subfield interval control unit 7 in FIG. 1 can be reduced.

FIG. 5A is a schematic diagram showing an example of a subfield configuration, and FIG. 5B is a schematic diagram showing another example of a subfield configuration.

In the example of FIG. 5A, the subfield sf
Each of 1 to sf12 includes an initialization period, a write period, a sustain period, and an erase period. In this case, the subfield interval control unit 7 in FIG.
In 2, the distributed arrangement of the subfields sf1 to sf12 shown in FIGS. 2 to 4 is performed by controlling the time interval between the erasing period of the preceding subfield and the initialization period of the following subfield.

In the example of FIG. 5B, the subfield sf
Each of 1 to sf12 includes an initialization period, a writing period, and a sustaining period, and the last subfield sf12 includes an initialization period, a writing period, a sustaining period, and an erasing period. In this case, the subfield interval control unit 7 controls the time interval between the sustain period of the preceding subfield and the initialization period of the succeeding subfield in the subfields sf1 to sf12, so that the 4
The subfields sf1 to sf12 shown in FIG.

FIG. 6 is a timing chart showing an example of drive voltages for the data electrodes, scan electrodes and sustain electrodes in PDP 1 of the plasma display device of FIG.

In the example of FIG. 6, as shown in FIG. 5A, the subfields sf1 to sf12 are set in the initialization period,
It includes a write period, a sustain period, and an erase period. Here, PDP1 has M data electrodes D1 to DM, N scan electrodes SCN1 to SCNN, and N sustain electrodes SUS.
1 to SUSN. M and N are each a positive integer.

In the initialization period, a plurality of scan electrodes SCN1
To SCNN are simultaneously applied with the initialization pulse Pset. Thereafter, during the writing period, the plurality of scan electrodes S
The write pulse Pw is sequentially applied to CN1 to SCNN. At the same time, the data electrodes D1 to D
A write pulse Pa is selectively applied to M. As a result, an address discharge occurs in the corresponding discharge cell 10 of the PDP 1.

Next, in the sustain period, the sustain pulse Psc is periodically applied to the plurality of scan electrodes SCN1 to SCNN, and the sustain pulse Psu is periodically applied to the plurality of sustain electrodes SUS1 to SUSN. Sustain electrode SU
The phases of the sustain pulses Psu of S1 to SUSN are shifted by 180 ° with respect to the phases of the sustain pulses Psc of the scan electrodes SCN1 to SCNN. Thus, a sustain discharge occurs following the address discharge. Scan electrode SCN during sustain period
The sum of the number of sustain pulses Psc applied to each of sustain electrodes 1 to SCNN and the number of sustain pulses Psu applied to each of sustain electrodes SUS1 to SUSN is the number of light emission pulses.

Thereafter, in the erasing period, the erasing pulse Pe is simultaneously applied to the plurality of sustain electrodes SUS1 to SUSN. Thereby, the discharge in each discharge cell 10 ends.

In the case of FIG. 6, by adjusting the time interval d between the end point of the erasing period of the preceding subfield and the start point of the initializing period of the succeeding subfield in the successive subfields, FIG. 4 are realized.

Next, a specific example of controlling the interval between subfields in the plasma display device of FIG. 1 will be described with reference to FIGS. Here, the case where the subfields sf1 to sf12 in one field have the configuration shown in FIG. 5B will be described.

FIG. 7 is a diagram showing an example of the time of the initialization period, the writing period, the sustaining period, and the erasing period constituting each subfield.

As shown in FIG. 7, the subfield sf1
Is 343 μs, and the initialization period of subfields sf2 to sf12 is 130 μs. The time of the writing period of the subfields sf1 to sf12 is 420 μs, and the time of the sustaining period is 6 μs.
X Number of light emission pulses. The time of the erasing period of the subfield sf12 is 132 μs.

FIG. 8A is a diagram showing an example of the weight and required time of each subfield in the case of the maximum number of light emission pulses, and FIG. 8B is a diagram showing the weight of each subfield in the case of the minimum number of light emission pulses. FIG. 4 is a diagram showing an example of a required time.

In the example of FIG. 8A, the maximum number of light emission pulses is 1355, and the time required for light emission in one field in that case is 8130 μs. In the example of FIG. 8B, the minimum number of light emission pulses is 511, and the time required for light emission in one field in that case is 3066 μs.

The subfield interval controller 7 shown in FIG. 1 shows the weights (the number of light emission pulses) of the subfields sf1 to sf12 based on the detection result of the level of the video signal by the input signal detector 8 in FIG. Adaptive luminance control is performed by switching the number of light emission pulses from the maximum number of light emission pulses to the minimum number of light emission pulses shown in FIG.

When the number of subfields is n, the total required time of one subfield in one field (the required driving time of one field) tsf is as follows.

Tsf = ts1 + (ta + te) + (ts2 + ta) × (n−1) + w × np (1) where ts1 is the time of the initialization period of the subfield sf1, and ts2 is the time after the subfield sf2. The time of the initialization period, ta is the time of the writing period, and te is the time of the erasing period. W is the light emission pulse width, and np is 1
This is the total number of light emission pulses in the field.

In the example of FIG. 7, ts1 = 343 and ts2 =
130, ta = 420, and te = 132. Also, w
= 6, n = 12. By substituting these values into the above equation (1), the required driving time tsf for one field is as follows.

Tsf = 343 + (420 + 132) +
(130 + 420) × (12-1) + 6 × np In the case of the maximum light emission pulse number, the light emission pulse number np is 1355 from FIG.
30 μs. Therefore, the required driving time tsf for one field is as follows.

Tsf = 6945 + 8130 = 115075 [μs] In the case of the minimum light emission pulse number, the light emission pulse number np is 511 from FIG.
6 μs. Therefore, the required driving time tsf for one field is as follows.

Tsf = 6945 + 3066 = 10011 [μs] When the field frequency of the input video signal is 50 Hz, 3 Hz is used to cope with the frequency fluctuation of the video signal.
To have enough time. Therefore, when the required light emission time is 8130 μs with the maximum number of light emission pulses, the surplus time S is expressed by the following equation.

S = (1/53) × 1000-15075
= 3793 [μs] Further, the time required for light emission with the minimum number of light emission pulses is 3066 μm.
In the case of s, the surplus time S is expressed by the following equation.

S = (1/53) × 1000-10011
= 8857 [μs] FIG. 9 is a table showing the relationship between the number of light emission pulses in one field and the surplus time. FIG. 10 is a graph showing the relationship between the number of light emission pulses in one field and the surplus time.

As shown in FIGS. 9 and 10, in a video signal having a field frequency of 50 Hz, the surplus time in the case of the minimum light emission pulse number 511 is 8857 μs, and the surplus time in the case of the maximum light emission pulse number 1355 is 3793 μm.
s. In a video signal having a field frequency of 60 Hz, the surplus time when the minimum number of light emission pulses is 511 is 58.
62 μs, and the surplus time in the case of the maximum light emission pulse number of 1355 is 798 μs.

As described above, in the case of a video signal having a field frequency of 50 Hz, the surplus time increases as compared with a video signal having a field frequency of 60 Hz. The surplus time increases as the number of light emission pulses in one field decreases. That is, the surplus time changes according to the change in the field frequency and the change in the number of light emission pulses.

The subfield interval control unit 7 in FIG. 1 calculates the surplus time by the above method based on the result of the field frequency discrimination by the synchronization frequency discrimination unit 6 and the result of the video signal level detection by the input signal detection unit 8. I do. Further, the subfield interval control unit 7 determines whether the subfields sf1 to sf1 shown in FIGS.
The time interval in the arrangement method 2 is calculated. in this case,
The time interval between the subfields sf1 to sf12 changes according to the surplus time.

[0102]

In the following Examples 1, 2 and Comparative Examples, subfields sf1 to sf12 are arranged by using the surplus time in a video signal having a field frequency of 50 Hz calculated as described above. The signal was displayed on the screen. Then, flicker occurring in the image was evaluated.

In the first embodiment, the surplus time of 8857 μs at a field frequency of 50 Hz is set to 1 according to the arrangement method of FIG.
It is divided into two equal parts, and a time interval of 8857/12 = 738 [μs] is inserted between the twelve subfields sf1 to sf12.

In the second embodiment, according to the arrangement method shown in FIG.
Equally divided, and the subfields sf7 to sf1 of the latter half group G2 among the 12 subfields sf1 to sf12
A time interval of 8857/6 = 1476 [μs] was inserted between the two.

In the comparative example, as shown in FIG. 12, the distributed arrangement of the subfields sf1 to sf12 in one field was not performed.

In Example 1, flicker was reduced by 25% as compared with the comparative example. In Example 2, flicker was reduced by 20% as compared with Example 1, and 40% as compared with Comparative Example.

Further, in the second embodiment, the pseudo contour of the moving image generated in the smooth gradation expression is reduced as compared with the first embodiment, and the image becomes closer to the image of the comparative example.

[0108]

As described above, according to the present invention, when a surplus time other than a plurality of subfields occurs in one field due to a change in the field frequency according to the determination result of the field frequency, the surplus time Allocation is made between a plurality of subfields within one field, and a time interval between the plurality of subfields within one field is controlled. Thereby, when the field frequency is low, a plurality of subfields are dispersedly arranged in one field, and the temporal concentration of the emission energy is reduced. As a result, the occurrence of a flicker that can be felt is suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a plasma display device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a first example of a subfield arrangement method when receiving a video signal having a field frequency of 50 Hz in the plasma display device of FIG.

FIG. 3 is a schematic diagram showing a second example of a subfield arrangement method when receiving a video signal having a field frequency of 50 Hz in the plasma display device of FIG. 1;

FIG. 4 is a schematic diagram showing a third example of a subfield arrangement method when receiving a video signal having a field frequency of 50 Hz in the plasma display device of FIG. 1;

FIG. 5 is a schematic diagram showing an example of the configuration of each subfield.

FIG. 6 is a timing chart showing an example of drive voltages of data electrodes, scan electrodes, and sustain electrodes in the PDP of the plasma display device of FIG.

FIG. 7 is a diagram showing an example of time of an initialization period, a writing period, a sustain period, and an erasing period of each subfield.

FIG. 8 is a diagram illustrating an example of the weight and required time of each subfield in the case of the maximum light emission pulse number and the case of the minimum light emission pulse number.

FIG. 9 is a table showing an example of a relationship between the number of light emission pulses in one field and a surplus time;

FIG. 10 is a graph showing an example of a relationship between the number of light emission pulses in one field and a surplus time;

FIG. 11 is a schematic diagram showing an example of a subfield division method when a video signal having a field frequency of 60 Hz is received in the plasma display device.

FIG. 12 is a schematic diagram showing an arrangement of subfields when a video signal having a field frequency of 50 Hz is received in a conventional plasma display device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 PDP 2,3,4 drive circuit 5 discharge control circuit 6 synchronization frequency discriminator 7 subfield interval controller 8 input signal detector 9 video signal processor 10 discharge cell 51 initialization pulse generator 52 write pulse generator 53 maintenance Pulse generation circuit 54 Erase pulse generation circuit D Data electrode SCN Scan electrode SUS Sustain electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/66 101 G09G 3/28 K

Claims (12)

[Claims] The present invention is configured to display a plurality of types of video signals having different field frequencies, divide one field into a plurality of subfields, weight each subfield with luminance, and emit light in each subfield. What is claimed is: 1. A display device for performing gradation display by a combination of presence / absence, comprising: discriminating means for discriminating a field frequency of an input video signal; When a surplus time other than the plurality of subfields occurs in the field, the surplus time is distributed among the plurality of subfields within one field to thereby set a time interval between the plurality of subfields within one field. A display device comprising: a subfield interval control means for controlling. 2. The apparatus according to claim 1, wherein the subfield interval control means extends the time interval between the plurality of subfields by equally allocating the surplus time among the plurality of subfields in one field. Claim 1
The display device according to the above. 3. The sub-field interval control means allocates the surplus time among the plurality of sub-fields in accordance with the luminance weight of the plurality of sub-fields in one field, so 2. The display device according to claim 1, wherein the time interval is extended. 4. The sub-field interval control means includes a first group including a plurality of sub-fields having a smaller weight, and a second group including a sub-field having a greater weight than the first group. The time interval between a plurality of subfields of the second group is extended by equally allocating the surplus time among the subfields in the second group. The display device according to 1. 5. The sub-field interval control further comprising weighting control means for changing a luminance weight of each sub-field by changing the number of light emission pulses in each sub-field according to a level of an input video signal. Means for allocating the surplus time among the plurality of sub-fields when a surplus time other than the plurality of sub-fields occurs in one field due to a change in weight by the weight control means. The display device according to claim 1, wherein a time interval between the plurality of subfields is controlled. 6. The plurality of types of video signals having different field frequencies are a first video signal having a first field frequency and a second video signal having a second field frequency lower than the first field frequency. A video signal, wherein the sub-field interval control means divides one field into the plurality of sub-fields when the first video signal is input, and divides the first field into the plurality of sub-fields when the second video signal is input.
The display according to any one of claims 1 to 5, wherein the surplus time caused by the change from the field frequency to the second field frequency is distributed among the plurality of subfields within one field. apparatus. 7. The first field frequency is 60 Hz.
The display device according to claim 6, wherein the second field frequency is 50 Hz. 8. A display method for dividing one field into a plurality of subfields, weighting each subfield with luminance, and performing gradation display by a combination of light emission in each subfield. Judging the field frequency of the video signal to be output. If the surplus time other than the plurality of subfields occurs in one field due to a change in the field frequency according to the discrimination result of the field frequency, the surplus time is set to 1 Controlling the time interval between the plurality of subfields within one field by allocating the plurality of subfields within the field. 9. The method of claim 1, wherein the controlling includes extending a time interval between the plurality of subfields by equally allocating the surplus time among the plurality of subfields in one field. The display method according to claim 8, wherein 10. The method according to claim 10, wherein the step of controlling comprises: allocating the surplus time among the plurality of subfields in accordance with the luminance weight of the plurality of subfields in one field. 9. The display method according to claim 8, further comprising a step of extending an interval. 11. The step of controlling comprises: dividing the plurality of sub-fields into a first group including sub-fields having a lower weight and a second group including sub-fields having a higher weight than the first group. Partitioning and extending a time interval between a plurality of subfields of the second group by evenly distributing the surplus time among the subfields in the second group. Item 8. The display method according to Item 8. 12. The method according to claim 12, further comprising the step of changing the number of light emission pulses in each subfield according to the level of an input video signal to change the luminance weight of each subfield. Controlling a time interval between the plurality of subfields by allocating the surplus time among the plurality of subfields when a surplus time other than the plurality of subfields occurs in one field due to a change in weight. The display method according to any one of claims 8 to 11, comprising: