JPH11288244A - Display device display method and plasma display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mitigate thermal distortion between the outer periphery of a display part and the display part and to stabilize performance for long time by obtaining average gray scale data of a picture signal based on an inputted picture signal and controlling the luminance of a picture displayed on the display part in accordance with the value. SOLUTION: When a picture signal 8 is inputted to a whole screen average gray scale calculation part 112, the gray scale data for one screen in the inputted picture signal 8 is averaged by the number of picture elements existing in the whole display part on average, for example, and the gray scale data per picture element is calculated. Picture element average gray scale data is outputted to a discharging times control part 113 and the number of maintaining pulses which are to be applied to respective picture elements is set based on picture element average gray scale data. Output corresponding to the number is given to an X electrode driving circuit 141 and a Y electrode driving circuit 142. Thus, the number of maintenance discharging times is controlled. Consequently, the luminance of a picture displayed on a display part can be controlled in accordance with the value of picture element average gray scale data by controlling the number of maintenance discharging times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, a display method, and a plasma display device.

[0002]

2. Description of the Related Art A plasma display device is expected to be a flat display device having many advantages such as having a wide viewing angle, good display quality, and being suitable for upsizing. In a general plasma display device, a predetermined voltage is applied between a pair of electrodes, and a gas discharge is performed by a discharge gas sealed between a front substrate and a rear substrate to generate ultraviolet rays. Is incident on the phosphor to emit visible light (conversion from ultraviolet light to visible light), thereby displaying a desired image.

FIG. 17 shows, for example, Japanese Patent Application Laid-Open No. 62-75588.
FIG. 1 is an explanatory diagram for explaining a configuration for performing temperature control in a conventional display device described in Japanese Patent Application Laid-Open Publication No. HEI 9-163456. FIG. 17A is a block diagram showing a conventional display device, in which reference numeral 80 denotes a plasma display panel (hereinafter, referred to as PDP), and reference numeral 82 denotes a display for generating display data and control signals required for the PDP 80. Controller (hereinafter referred to as DCTL), 83
Is a power supply circuit for supplying necessary power to the PDP 80, and 84 is a temperature sensor, which functions to convert the temperature to a luminance signal by an appropriate means.

The operation of the conventional device will be described below. FIG. 17B is a diagram showing a relationship between the temperature detected by the temperature sensor 84 and the luminance control described in the above publication, in which the horizontal axis represents the temperature and the vertical axis represents the luminance. That is, when the temperature detected by the temperature sensor 84 exceeds a certain temperature threshold value T0, the brightness of the PDP 80 is reduced to a certain value.

[0005] As the luminance decreases, the power consumption decreases accordingly, and as a result, the temperature is prevented from further increasing. When the temperature decreases and becomes equal to or lower than the temperature threshold value T0, the luminance returns to the original value. Therefore, the rise in temperature exceeds the temperature threshold T by the temperature sensor 84 before the temperature exceeds the maximum allowable value.
It will be suppressed starting from 0. Further, there is described an example in which the luminance is gradually reduced in order to suppress a rapid change in the luminance.

[0006] The conventional device has a PDP device which is configured as described above, which eliminates power consumption and a temperature rise that are hindered by a small and lightweight design, and does not sacrifice brightness. It is to try.

[0007]

A plasma display device as a display device uses discharge for image display, and displays an image based on the presence or absence of light emission based on discharge in a discharge cell, that is, a binary light emission state. It can be called a device. In practice, when a multi-valued image signal such as a TV signal is to be displayed, it is naturally necessary to consider gradation expression. In order to perform gradation expression using such an apparatus, the display period of one field is divided into subfield periods having a lighting period for display at a predetermined ratio, and each pixel constituting an image for one screen is divided into subfield periods. In the subfield period selected in accordance with the grayscale data, the grayscale expression is performed by performing lighting for display (using the eye integration effect).

[0008] For example, at present,
In the type PDP, it is necessary to express 63 gradations when one field period is divided into subfield periods having a display period (a period in which a sustain pulse is applied; a sustain period) which is proportional to a power of 2. the sustain pulse for every subfield period corresponding from 2 ⁰ to 2 ⁵ first
, And sustain discharge is performed.

Therefore, it is very important to ensure the best display state for the gradation data of the image signal.
Further, since the PDP is usually made of glass, it has poor thermal conductivity.
In the case of gray scale and 256 gray scale, the temperature difference between the discharge cells in the vicinity becomes very large, and the sealing portion for achieving the sealing structure of the PDP, for example, due to the thermal strain caused by this temperature difference, There has been a strong demand for a specific configuration and method for solving the problem of PDP performance degradation such as damage and loss of sealing performance.

The present invention has been made to solve the above-described problems in the PDP, and can reduce the occurrence of thermal distortion while ensuring a good display state in consideration of the gradation of an image signal. In particular, the present invention proposes a specific solution for PDP, in particular, by relieving thermal distortion between the outer periphery of the display unit and the display unit, so that the performance is stable for a long time and the display quality is not impaired. Is

[0011]

According to a first aspect of the present invention, there is provided a display device comprising a plurality of pixels;
A drive control unit including a configuration for obtaining average grayscale data of the image signal based on the input image signal and controlling the luminance of an image displayed on the display unit according to the value of the average grayscale data And was prepared.

In the display device according to the second invention,
The average gradation data is configured to be obtained as an average per pixel in the display unit.

In the display device according to the third invention,
The configuration is such that the average gradation data is obtained as an average per divided area composed of a plurality of pixels in the display unit.

In the display device according to the fourth invention,
When the average gradation data exceeds a predetermined value, the rate of change in luminance with respect to the number of pixels is changed.

In the display device according to the fifth invention,
When the average gradation data exceeds a predetermined value, the rate of change in luminance with respect to the number of pixels is reduced.

In the display device according to the sixth aspect,
A temperature sensor is provided corresponding to the segmented area, and the brightness of an image displayed is controlled based on temperature data detected by the temperature sensor.

In the display device according to the seventh invention,
The brightness of the displayed image is controlled based on the weight coefficient corresponding to the pixel position in at least one of the first direction and the second direction on the display unit.

In the display method according to the eighth invention,
Average grayscale data of the image table signal is obtained based on the input image signal, and the luminance of an image displayed on a display unit including a large number of pixels is controlled according to the value of the average grayscale data. I did it.

In the display method according to the ninth aspect,
The average gradation data is obtained as an average per pixel in the display unit.

In the display method according to the tenth aspect, the average gradation data is obtained as an average per divided area composed of a plurality of pixels in the display section.

In the display method according to the eleventh aspect, when the average gradation data exceeds a predetermined value, the rate of change in luminance with respect to the number of pixels is changed.

In the display method according to the twelfth aspect, when the average gradation data exceeds a predetermined value, the rate of change in luminance with respect to the number of pixels is reduced.

In the display method according to the thirteenth aspect, the brightness of the displayed image is controlled based on the temperature data measured corresponding to the divided area.

In a display method according to a fourteenth aspect, the brightness of an image to be displayed is controlled based on a weight coefficient corresponding to a pixel position of at least one of the first direction and the second direction on the display unit. I did it.

In the plasma display device according to the fifteenth aspect, the display section is composed of a number of pixels for displaying an image depending on whether the pixels are turned on or off.
In order to express the gradation of the image with the lighting and non-lighting periods of each pixel in the display unit, when the value of gradation data in the display unit based on an input image signal exceeds a predetermined value, the display is stopped. And a drive control unit including a configuration for controlling a lighting period and a non-lighting period in each of the pixels of the unit such that a rate of change in luminance in the display unit is reduced.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Explanation of Parts Common to Each Embodiment) FIG. 1 is an external view schematically showing an example of a plasma display panel constituting a display device. In the figure, reference numeral 500 denotes a PDP having the following configuration. That is, reference numeral 1 denotes a first electrode group (a group of X electrodes and Y electrodes described later, and a pair of X electrodes and Y electrodes
The front substrate 2 made of glass on which a display electrode (corresponding to a display line) is formed is disposed so as to face the front substrate 1, and is made of glass on which a second electrode group (a group of W electrodes described later) is formed. A ceramic back substrate 30 generates a gas discharge for display by applying a pulse voltage (sustain pulse described later) to the first electrode group, and emits ultraviolet light generated by the gas discharge using a phosphor. Display section for displaying an image composed of a large number of pixels by converting the image into visible light (portion surrounded by a dotted line in FIG. 1);
Reference numeral 1 denotes a non-display unit that is located around the display unit 30 and does not display an image.

The PDP 500 is divided into a display section 30 on which an image is displayed and a non-display section 31 on the outer periphery of the display section 30 where no image is displayed. In the non-display portion 31, a sealing portion for hermetically sealing the front substrate 1 and the rear substrate 2 exists around the display portion 30, and the front substrate 1 formed by the sealing portion is provided. A discharge gas (a Penning gas in which Ne or Xe is mixed) for causing the above-described gas discharge is sealed in a sealed space between the substrate and the rear substrate 2.

On the first electrode group, a dielectric layer (not shown), usually a dielectric layer, is further provided on the dielectric layer to protect the dielectric from ion bombardment during gas discharge and to facilitate electron emission during gas discharge. An MgO film is provided as a member for this purpose. Hereinafter, unless otherwise specified, the dielectric layer and the MgO film will be simply referred to as a dielectric layer.

Since the number of sustain pulses applied to the first electrode group is substantially proportional to the size of the gradation to be displayed on the display unit 30, light emission for display is performed. By controlling the number of sustain pulses to be applied, an image expression with rich gradation expression can be realized.

FIG. 2 is an explanatory diagram schematically showing the configuration of a plasma display device 1000 using the above-described PDP 500. In the drawing, reference numeral 5 denotes an X electrode, which is formed on the front substrate 1 side and functions as a scanning electrode to which a scanning voltage is sequentially applied, and which is related to gas discharge for display.
Are formed on the front substrate 1 side in parallel with the X electrode 5 and at a predetermined interval (discharge gap), and an electric field is applied between the X electrode 5 (sustain pulse is given) to thereby be described later. A Y electrode 6 for causing a sustain discharge to be performed is a W electrode 6 formed on the rear substrate 2 side and arranged so as to intersect the X electrode 5 at a right angle, and corresponds to an intersection with the X electrode 5. In a write operation for accumulating wall charges in a portion of the dielectric layer covering each of the X electrode 5 and the Y electrode 4 corresponding to the discharge cell UC to be caused to emit light by gas discharge for display in the portion. Used for

141, 142 and 143 output driving voltages to the X electrode 5, the Y electrode 4 and the W electrode 6, respectively.
Driving circuits provided corresponding to the respective electrodes (hereinafter, the X electrode driving circuit 141, the Y electrode driving circuit 142, and the W electrode driving circuit 143 are collectively expressed as driving circuits 141 to 143), and 110 is a driving circuit 141 to 141. 143 is a drive control circuit for controlling each of them, and the drive control unit in the figure is configured to include the drive circuits 141 to 143 and the drive control circuit 110.

The operation according to this configuration will be described below. When the image signal 8 and the synchronization signal 9 input from the outside of the drive control unit are input to the drive control circuit 110, the drive control circuit 110 controls the X electrode drive circuit 141 based on these input signals. An output is generated for Based on this output, the X electrode drive circuit 141
A scanning voltage is sequentially applied to the electrodes 4.

In synchronization with the timing of applying the scanning voltage, a selective writing voltage is applied from the W electrode drive circuit 143 so as to correspond to the portion of the discharge cell UC where the W electrode 6 is to emit light. A gas discharge (writing discharge) caused by the potential difference between the writing voltage applied to the W electrode 6 and the scanning voltage applied to the X electrode 5 exceeding the discharge starting voltage (discharge threshold) causes a corresponding discharge cell UC to respond. Wall charges having different electric polarities are accumulated on the dielectric layer at portions corresponding to the pair of X electrodes 5 and Y electrodes 4 (writing operation).

Thereafter, the X electrode drive circuit 141 and the Y electrode drive circuit 142 generate a pulse voltage (sustain pulse) for performing gas discharge (sustain discharge or display discharge) a number of times corresponding to the gray level to be displayed. A gas discharge is alternately output between the X electrode 5 and the Y electrode 4 and a synergistic voltage with a wall voltage caused by a wall charge accumulated on the dielectric layer by a writing operation exceeds a discharge starting voltage, thereby causing gas discharge. Is generated and maintained (display operation).

The above-described writing operation and display operation are performed at timings schematically shown in FIG.
In the following, unless otherwise specified, the wall charges accumulated on the dielectric layer at the time of completion of the immediately preceding sustaining operation are temporarily extinguished before the above-described writing operation (at least, the sustaining pulse is applied. This is referred to as a writing operation including an erasing operation for generating no gas discharge.

FIG. 3 is an explanatory diagram for explaining a gradation display operation in the plasma display device. In the figure, F is one field period, for example, having a time length corresponding to one field of the NTSC signal (however, F
Is a period during which one screen displayed on the plasma display panel is displayed, and
It is not necessarily limited to one field in the NTSC signal. FIG. 3 shows an example in which a field period F is composed of eight subfields SF1 to SF8 each separated by a predetermined period (subfield gradation method).

One subfield basically includes a writing period in which a writing operation is performed (including the erasing operation described above) and a sustaining period in which a display operation is performed. That is to say, referring to the drawing, each of W1 to W8 indicates a writing period corresponding to each subfield of SF1 to SF8 in which a writing operation is performed, and each of S1 to S8 performs a display operation. To the sustain period corresponding to each subfield of SF8.

The operation will be described below. Write period W
In 1, after the erase operation of all the discharge cells included in the display unit 30, a write operation is selectively performed on the discharge cells UC to be caused to emit light (write operation in the subfield SF1), and in the subsequent sustain period S1 Sustain pulse is X electrode 5
A sustain operation is performed during the sustain period S1 by applying the voltage between the pixel electrode and the Y electrode 4 (sustain operation in the subfield SF1). Then, a series of operations in the subfield SF1 is completed by ending the sustain operation S1.

In the above-mentioned sustaining period, ultraviolet rays are generated by the occurrence and maintenance of the gas discharge, and the ultraviolet rays are incident on the phosphor contained in the discharge cells UC and converted into visible light, and are displayed. Light emission is performed. On the other hand, in the discharge cells UC in which no write discharge is performed and no wall charge is stored, no sustain discharge is generated even when the sustain pulse is applied, so that no ultraviolet light is generated and no light emission for display is generated.

The above operation is performed in the respective periods of the subfields SF2 to SF8 following the subfield SF1, and the same operation as that of the subfield SF1 is sequentially performed, so that an image is displayed in one field period F.

Each of the above-described subfields SF1 to SF8
In, for example, the number of sustain pulses according to the power of 2 is given. In this case, one display discharge is performed in the subfield SF1, two display discharges are performed in the subfield SF2, four display discharges are performed in the subfield SF3,.
In the subfield SF8, if the number of display discharges in each subfield follows a power of 2, such as 128 display discharges, gradation can be expressed by a combination of subfields in which this display discharge is to be generated.

Therefore, as described above, since the number of sustain pulses is substantially proportional to the gradation, one field period F
By selecting a subfield to emit light in accordance with the gray scale, the gray scale expression is performed.

As described above, it is easy to change the gradation by 1) changing the number of sustain pulses 2) changing the combination of subfields in which the writing operation is to be performed. Can understand.

Regarding the above 1), in order to change the number of sustain pulses applied to the X electrode 5 and the Y electrode 4,
From the drive control circuit 110 to the X electrode drive circuit 141 and Y
This is realized by changing the output for the sustain pulse to the electrode driving circuit 142.
Is changed by changing the output from the drive control circuit 110 to the W electrode drive circuit 143 in order to change the state of the write operation.

Embodiment 1 FIG. 4 shows a drive control circuit 110 shown in FIG. 2 according to an embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an entire control function unit 111 included in FIG. In the figure, reference numeral 112 denotes a full-screen average gray-scale calculation unit for calculating an average gray-scale over the entire display unit 30; The control unit is a control unit, and the entire screen average gradation calculation unit 112 and the number-of-discharges control unit 113 constitute an entire control unit 111.

The operation will be described below. When the image signal 8 is input to the full-screen average gray-scale calculation unit 112, the gray-scale data for one screen in the input image signal 8 is averaged by, for example, the number of pixels existing on the entire display unit 30, and 1 Tone data per pixel (hereinafter referred to as pixel average tone data)
Is calculated. This pixel average gradation data is output to the number-of-discharges control unit 113, and the number of sustain pulses to be applied to each pixel is set based on the pixel average gradation data. 141 and the Y electrode drive circuit 142, the number of sustain discharges is controlled. The brightness of the display unit 30 can be controlled by controlling the number of times of the sustain discharge. That is, the luminance of the image displayed on the display unit 30 is controlled according to the value of the pixel average gradation data.

Hereinafter, a control method using the above configuration will be described. FIG. 5 is an explanatory diagram showing an average luminance-average gradation characteristic per pixel of the plasma display device according to the embodiment of the present invention. In the figure, the horizontal axis (indicated as “average gray level” in the figure) is the average gray level per pixel (pixel average gray level data) obtained by averaging one screen of the image signal. 0-1
The vertical axis (indicated as “average luminance” in the figure) is the average luminance per pixel obtained by averaging one screen of the display screen displayed on the display unit 30, and the minimum is set to 0. , With the maximum being 1 being normalized between 0 and 1.

As shown in the figure, when the average gradation becomes equal to or more than a (a is a predetermined value in this case), the number of discharges is suppressed so that the average luminance becomes constant b, and the change rate of the luminance with respect to the number of pixels is changed. (Decrease). By doing so, even if the average luminance required from the input image signal 8 is large, it is possible to suppress the temperature rise of the substrate constituting the PDP and reduce the occurrence of thermal distortion in the peripheral portion of the substrate. Can,
For example, it is possible to suppress, for example, damage in the sealing portion, which has conventionally been a problem, and to suppress performance degradation of the PDP. In addition, the heat radiation mechanism can be made smaller,
Further, since the number of discharges is suppressed so that the power does not become larger than a certain value, the size of the power supply circuit can be reduced.

(Other average luminance-average gradation characteristics) FIG.
FIG. 9 shows an example of another control method according to this embodiment.
Average brightness per pixel of plasma display device-
FIG. 4 is an explanatory diagram illustrating an average gradation characteristic. In the figure, the horizontal axis (in the figure, indicated as average grayscale) represents the average grayscale per pixel (pixel average grayscale data) obtained by averaging one screen of the image signal.
The vertical axis (indicated as average luminance in the figure) represents one screen of the display screen displayed on the display unit 30. Is the average luminance per pixel, which is normalized to 0 to 1 with the minimum being 0 and the maximum being 1.

As shown in FIG.
The change rate (increase rate) of the average luminance is 0 to b1, b1 to b2, b2 to bm corresponding to each range of 1 to a2 and a2 to 1.
As shown in the figure. For this reason,
Restricting the image signal so that the power does not become larger than a certain value is the same as that in FIG. 5, but a bright input can be displayed brightly and a dark input can be displayed dark, so that a finer adjustment of the average luminance can be performed. This makes it possible to feel less discomfort when looking at the screen. In the example shown in FIG. 6, which is referred to here, the rate of increase of the average luminance is decreased step by step in each gradation section, but in order to make the average luminance change more smoothly. Alternatively, the rate of increase of the average luminance may be continuously reduced according to the gradation.

(Control of Number of Discharges) FIG. 7 is a diagram for explaining a control characteristic for controlling the number of discharges based on the average gradation per pixel of the plasma display device according to the embodiment of the present invention. FIG. In the figure, the horizontal axis (indicated as “average gray level” in the figure) is the average gray level per pixel (pixel average gray level data) obtained by averaging one screen of the image signal. Vertical axis (indicated as weighting factor in the figure)
Indicates a coefficient by which the number of sustain discharges corresponding to each gradation is multiplied. Note that the weighting coefficient only needs to include a range in which the weighting coefficient decreases as the average gradation increases.

As shown in the figure, the weight coefficient is set to 1 when the average gradation is from 0 to c, and when the average gradation exceeds c, for example, a weight coefficient proportional to the reciprocal of the average gradation is set to the original value. The number of display discharges actually given is based on a value multiplied by the number of display discharges, and the lower limit value d (d> 0) of the weight coefficient is set when the average gradation is 1. At this time, the value of the weight coefficient d may be determined to a level that does not cause discomfort compared to the actual display image.

As described above, even if the average gradation is increased, the number of discharges is controlled to be smaller than the intended number of times, thereby suppressing the thermal distortion of the PDP and shortening the operation time of one screen. Thus, there is also an effect that pseudo contours in a moving image, which are peculiar to a binary display device such as a PDP, are eventually suppressed.

(Control of Other Number of Discharges) FIG. 8 illustrates another control characteristic for controlling the number of discharges by an average gradation per pixel of the plasma display device according to the embodiment of the present invention. FIG. In the figure, the horizontal axis (indicated as “average gray level” in the figure) is the average gray level per pixel (pixel average gray level data) obtained by averaging one screen of the image signal. 0-1
The vertical axis (in the figure, denoted by a weight coefficient) indicates a coefficient by which the number of sustain discharges corresponding to each gradation is multiplied. Note that the weight coefficients shown in FIG. 8 are those in which the weight coefficient when the average gradation is 0 is 1 and the weight coefficient monotonously decreases as the average gradation increases.

As shown in the figure, as the average gray level of the input image signal per pixel increases, the number of sustain discharges for each gray level initially determined is reduced, and the weight at the time of the average gray level 1 is reduced. The minimum value of the coefficient is d (d> 0). Therefore, FIG.
Similar to the one shown in the above, bright input is displayed brightly,
By displaying darkly on a dark input, finer adjustment of the average luminance becomes possible, and when looking at the screen, the sense of discomfort is reduced.

In FIG. 8 referred to here, the rate of increase of the average luminance continuously decreases in each gradation section, as in the case of FIG. ,
The rate of increase of the average luminance may decrease stepwise according to the gradation. Also, as in the case shown in FIG. 7, even if the average gradation increases, the number of discharges is controlled to be smaller than the intended number of times, thereby suppressing the thermal distortion of the PDP and achieving one screen. The operating time can be shortened,
There is also an effect that pseudo contours in a moving image are suppressed as a result, which is unique to a binary display device such as a PDP.

As described above, the overall control function unit 11
By configuring 1, it is possible to reduce the number of discharges when the average gradation per pixel is large over the entire display unit, so that the amount of heat generated over the entire display unit is reduced to the gradation of the input image signal. Can be reduced accordingly,
For this reason, even if the gradation changed by the image signal has a large difference, it is generated on the front substrate and the rear substrate by adaptively changing and controlling the average luminance and the number of sustain pulses according to the image signal. Thermal distortion can be reduced, and pseudo contours can be suppressed.

As a method of suppressing the generation of heat, in addition to controlling the number of sustain discharges, the method of 2) changing the combination of subfields in which the writing operation is to be performed is suppressed. You may.

FIG. 9 is a block diagram showing another configuration of the overall control function unit 111. The write operation for outputting write data to the W electrode drive circuit 143 in place of the discharge number control unit 113 shown in FIG. The data output unit 114 is provided.

The discharge number control unit 113 controls the number of sustain pulses in the selected subfield in a state where the original subfield is selected based on the gradation of the image signal. By inputting the output from the tone calculation unit 112 to the write data output unit 114, the selection of the original subfield based on the tone of the image signal is changed according to the average tone.

Even in this case, the same effect can be obtained as when the number of sustain pulses is multiplied by a weighting factor based on the average gradation.

Embodiment 2 In the first embodiment,
Although the configuration in which the drive control circuit 110 includes the overall control function unit 111 has been described, an embodiment described below can also be used. First, before describing a specific configuration, the concept of the present embodiment will be described. FIGS. 10 and 11 are explanatory diagrams illustrating a state in which a PDP is divided for explaining the concept in the present embodiment.

In FIG. 10, reference numeral 32 denotes a divided area to be controlled. As can be seen from the drawing, one display surface 30 is constituted by a plurality of divided areas 32. For example, assuming a PDP having a resolution of 480 lines (480 display lines) × 640 dots (640 pixels per display line), which is currently called a VGA type, the total number of pixels is 307200 pixels. In the case of color display, discharge cells for emitting three primary colors of red (R), green (G), and blue (B) are required for each pixel, so that the total number of discharge cells is 921600 discharge cells. For example, as shown in FIG. 10, when the display area 30 is regarded as 48 divided areas, the number of discharge cells per one divided area is 19,200 discharge cells.

That is, as shown in FIG. 10, by configuring the display area 30 as a plurality of divided areas and controlling the luminance, the operation speed is increased, the circuit scale is reduced, and the required memory capacity is obtained. The effect of reduction of the amount can be expected.

In FIG. 11, reference numeral 33 denotes a temperature measurement position, and shows a case where a temperature sensor is provided in any of the divided areas 32 shown in FIG. Therefore, the following describes a case configured as described above.

(Regarding the Partial Control Circuit) In FIG. 10, reference numeral 32 denotes a division area to be controlled, which is obtained by dividing the display unit 30 into 48 as described above. In FIG. 10, the average gradation in the divided area 32 is accumulated on the time axis, the temperature of each divided area 32 is estimated, and the temperature difference estimated between a certain divided area 32 and the adjacent divided area 32 is calculated. Ask. Then, the image signal in the periphery of the display unit 30 or the gradation data thereof is added to that part (display unit 30).
Is multiplied by a weighting factor that makes the brightness darker.

In this manner, the brightness is reduced around the display unit 30 and the number of gas discharges around the display unit 30 is reduced. Therefore, thermal distortion around the display unit 30 is reduced. Thus, damage to the sealing portion can be suppressed.

FIG. 11 is an explanatory diagram for explaining an example for further accurately estimating the temperature in the divided area described with reference to FIG.
Reference numeral 3 denotes a segmented area where the temperature sensor is attached (that is, a temperature measuring position). According to the configuration shown in FIG. 11, based on the actual temperature value obtained from the temperature measurement position 33, the average gradation in the other divided areas 32 to which the temperature sensor is not attached is accumulated on the time axis, and It is characterized by estimating the temperature of every 32. In other words, the temperature estimated for each of the divided areas 32 is calibrated by the temperature obtained from the temperature measurement position 33.

The image signal around the display section 30 or the gradation data thereof includes the portion (the display section 30).
Is multiplied by a weighting factor that makes the brightness darker.

In this manner, the brightness is reduced around the display unit 30 and the number of gas discharges around the display unit 30 is reduced, so that the heat distortion around the display unit 30 is small. Thus, damage to the sealing portion can be suppressed. In addition, the temperature measuring position 33 to which the temperature sensor provided corresponding to the segmented area is attached.
Need only be provided at a few places on the display unit 30, and FIG. 11 shows an example in which the display unit 30 is provided inside the display unit 30. The display unit 30 is provided over both or both of the display unit 30 and the non-display unit 31. In this case, the temperature control can be performed more precisely and finely, which is effective in suppressing the influence of thermal strain.

FIG. 12 is a block diagram showing the configuration of the partial control function unit 115 included in the drive control circuit 110 shown in FIG. 2, which is an embodiment according to the present invention.
In the figure, reference numeral 116 denotes an average gray level calculating unit for each area for obtaining the average gray level in the above-described divided area 32, and 117 denotes a control unit for controlling the number of display discharges based on the output from the average gray level calculating unit 116 for each area. , And a partial control function unit 115 is configured by the area average gradation calculating unit 116 and the number-of-discharges control unit 117.

The operation will be described below. When the image signal 8 is input to the average gradation calculating unit 116 for each area, each gray scale data of each of the divided areas 32 in the input image signal 8 is averaged, for example, by the number of pixels existing in the divided area 32, and
The gradation data per section area (hereinafter, referred to as section area average gradation data) is calculated. The divided area average gradation data is output to the number-of-discharges control unit 117, and the luminance of each pixel can be controlled based on the divided area average gradation data. That is, the brightness of the image displayed on the display unit 30 is controlled according to the value of the divided area average gradation data.

(Regarding Control of Gradation Data by Partial Control Circuit) Hereinafter, a method of controlling gradation data using the above-described method of estimating the temperature of each divided area will be described in detail. FIG. 13 is an explanatory diagram for describing a control method when the partial control function unit 115 is used. In the figure, the axis in the first direction represents, for example, the number of pixels in the horizontal direction of the display unit 30 and is normalized between 0 and 1. The axis in the second direction represents, for example, the number of pixels in the vertical direction of the display unit 30, and is normalized to 0 to 1 like the axis in the first direction. The axis of the weight coefficient in the figure represents a weight coefficient of 0 to 1 by which the gradation data is multiplied to control the gradation data.

In FIG. 13, the input image is based on the predicted temperature difference calculated in the second direction (vertical direction of the display unit 30), particularly in the adjacent divided areas 32 around the display unit 30. The data to be output to the W electrode drive circuit 143 is obtained by multiplying the gradation data obtained from the signal by a coefficient that changes in the first direction (horizontal direction of the display unit 30). ah, (1-ah) to 1 are each multiplied by a coefficient that changes from 1 to bh, as shown in the figure. Thereby, the temperature in the first direction can be controlled by detecting the expected temperature difference of the display unit 30 only in the second direction.

FIG. 14 is an explanatory diagram for explaining another control method when the partial control function unit 115 is used. In the figure, the axis in the first direction represents, for example, the number of pixels in the horizontal direction of the display unit 30 and is normalized between 0 and 1.
The axis in the second direction represents, for example, the number of pixels in the vertical direction of the display unit 30, and is normalized to 0 to 1 like the axis in the first direction. The axis of the weight coefficient in the figure represents a weight coefficient of 0 to 1 by which the gradation data is multiplied to control the gradation data.

In FIG. 14, the input image is calculated based on the predicted temperature difference calculated in the first direction (horizontal direction of the display unit 30), particularly in the adjacent divided areas 32 around the display unit 30. The data to be output to the W electrode drive circuit 143 is obtained by multiplying the gradation data obtained from the signal by a coefficient that changes in the second direction (vertical direction of the display unit 30). Each section of av, (1-av) to 1 is multiplied by a coefficient that changes from 1 to bv, as shown in the figure. Thereby, the temperature in the second direction can be controlled by detecting the expected temperature difference of the display unit 30 only in the first direction.

FIG. 15 is an explanatory diagram for explaining another control method when the partial control function unit 115 is used. In the figure, the axis in the first direction represents, for example, the number of pixels in the horizontal direction of the display unit 30 and is normalized between 0 and 1.
The axis in the second direction represents, for example, the number of pixels in the vertical direction of the display unit 30, and is normalized to 0 to 1 like the axis in the first direction. In addition, the axis of the weight coefficient corresponding to the vertical axis of the figure is:
Multiply the gradation data by 0 to 1 to control the gradation data
Represents a weighting coefficient of.

In FIG. 15, adjacent divided areas 32, 3 in the first direction (horizontal direction of the display unit 30) and the second direction (vertical direction of the display unit 30), particularly around the display unit 30 are shown.
2 is multiplied by a coefficient that changes in both the first direction and the second direction with respect to the gradation data obtained from the input image signal based on the predicted temperature difference calculated in step 2, and output to the W electrode drive circuit 143. As shown in the figure, each of the peripheral portions 0 to ah and (1-ah) to 1 in the first direction is multiplied by a coefficient that changes from 1 to bh. Peripheral parts 0-av, (1-a
Each of the sections v) to 1 is multiplied by a coefficient that changes from 1 to bv, as shown in the figure. Thereby, it is possible to detect the expected temperature difference between the first direction and the second direction of the display unit 30 and control the temperature in the two directions of the first direction and the second direction.

As described above, when the partial control function section 115 is used, since the drive control can be performed for each of the divided areas 32, for example, heat generation around the display section 30 as a specific portion in the display section 30 is suppressed. This makes it possible to reduce the thermal strain in this area.

In this way, it is sufficient to use a memory for obtaining the gradations of the divided areas, so that the memory capacity is smaller than the memory required for obtaining the number of gradations of the entire display screen. For example, two areas of memories A and B are prepared, and while the number of gradations of a certain area is obtained in A, the image data of the next area is written in the memory B, When the number of tones has been obtained, the number of tones in the memory B can be read in parallel with the reading of the image data of the next area into the memory A. Therefore, the number of tones can be obtained at high speed while saving the memory capacity. be able to. Needless to say, two areas of memory are not necessarily required as in the above-described example, and the same effect as in the above-described configuration can be obtained by devising data writing and reading with only one area of memory. In this case, a memory capacity of 1 / the number of divided areas is sufficient.

In FIGS. 4, 9 and 12 described above, the drive control circuit 110 is provided with a full-screen control function unit 111 including a full-screen average gradation calculation unit 112 and a discharge count control unit 113. A full-screen control function unit 111 including a full-screen average gradation calculation unit 112 and a write data output unit 114,
A configuration including a partial control function unit 115 including a region-specific average gradation calculation unit 116 and a discharge count control unit 117, and a partial control function unit 115 including a region-specific average gradation calculation unit 116 and a write data output unit 118. However, as shown in FIG. 16, as shown in FIG. 16, the whole-screen control function unit 111 including the full-screen average gradation calculation unit 112 and the number-of-discharges control unit 113, the region-specific average gradation calculation unit 116, and the write data output unit Alternatively, a configuration having a partial control function unit 115 including the control unit 118 may be adopted to combine the control methods described above. In the above description, the control is performed using the average gradation per pixel as the calculated gradation information for easy understanding. However, the control is performed using the sum of the image signals 8 for one screen. You can also.

Further, in the calculation of the average gradation per pixel, it has been described that the calculation is performed using the image signal 8 for one screen. However, considering the continuity of the normal image signal 8,
As a part of the image signal 8 for one screen, for example, 1/8 to 1
The average gradation may be calculated by using the data thinned to / 4. In this case, the calculation time of the average gradation can be shortened, and the scale of the calculation circuit including the image memory and the like can be reduced. Furthermore, if this is performed for each area, the memory capacity can be further reduced and the calculation circuit scale can be further reduced as described above.

[0083]

Since the present invention is configured as described above, it has the following effects. First
According to the invention, a display unit composed of a large number of pixels,
A drive control unit including a configuration for obtaining average grayscale data of the image signal based on the input image signal and controlling the luminance of an image displayed on the display unit according to the value of the average grayscale data Therefore, it is possible to adopt an optimal driving method that suppresses the temperature rise of the display unit, so that the performance of the display unit can be suppressed, and the display device that can reduce the heat radiation mechanism and the power supply circuit can be configured. Obtainable.

According to the second invention, the average gradation data is
Since it is configured to be obtained as an average per pixel in the display unit, it is possible to obtain a display device capable of displaying an image with appropriate luminance based on the gradation data of the entire display unit.

According to the third invention, the average gradation data is
Since the display unit is configured to be obtained as an average per divided area composed of a plurality of pixels in the display unit, it is possible to obtain a display device with high-speed operation, reduced circuit scale, and reduced memory capacity.

According to the fourth aspect, when the average gradation data exceeds a predetermined value, the rate of change of the luminance with respect to the number of pixels is changed. A display device can be obtained.

According to the fifth aspect, when the average gradation data exceeds a predetermined value, the rate of change in luminance with respect to the number of pixels is reduced, so that deterioration in the performance of the display unit can be suppressed and the heat radiation mechanism can be reduced. In addition, a display device in which a power supply circuit can be made small can be obtained.

According to the sixth aspect of the present invention, the temperature sensor is provided corresponding to the divided area, and the brightness of the displayed image is controlled based on the temperature data detected by the temperature sensor. A display device capable of displaying an image in accordance with the actual temperature of the display unit can be obtained.

According to the seventh aspect, the brightness of the displayed image is controlled based on the weight coefficient corresponding to the pixel position of at least one of the first direction and the second direction on the display unit. With this configuration, it is possible to obtain a display device capable of suppressing heat generation at a specific portion of the display unit, for example, around the display unit.

According to the eighth aspect, the average gradation data of the image table signal is obtained based on the input image signal, and a display composed of a large number of pixels is determined according to the value of the average gradation data. Since the brightness of the image displayed on the display is controlled, the optimal driving method that suppresses the temperature rise of the display can be adopted, so that the performance degradation of the display can be suppressed, the heat radiation mechanism can be reduced, and the power supply can be reduced. A display method in which a circuit can be configured to be small can be realized.

In the display method according to the ninth aspect,
Since the average gradation data is obtained as an average per pixel in the display unit, a display method capable of displaying an image with appropriate luminance based on the gradation data of the entire display unit can be realized.

In the display method according to the tenth aspect, the average gradation data is obtained as an average per divided area composed of a plurality of pixels in the display unit, so that the display method can achieve a high-speed operation. Can be realized.

In the display method according to the eleventh aspect, when the average gradation data exceeds a predetermined value, the rate of change of the luminance with respect to the number of pixels is changed. A display method according to the method can be realized.

In the display method according to the twelfth aspect, when the average gradation data exceeds a predetermined value, the rate of change in luminance with respect to the number of pixels is reduced. A display method that can be made smaller and a power supply circuit can be made smaller can be realized.

In the display method according to the thirteenth aspect, the brightness of the displayed image is controlled based on the temperature data measured corresponding to the divided area.
A display method capable of displaying an image according to the actual temperature on the display unit can be realized.

[0096] In the display method according to the fourteenth aspect, in the display method, the luminance of an image displayed based on a weighting factor corresponding to a pixel position in at least one of the first direction and the second direction on the display unit is determined. Since the control is performed, it is possible to realize a display method capable of suppressing heat generation, for example, around the display unit as a specific part in the display unit.

[0097] In the plasma display device according to the fifteenth aspect, a display section comprising a large number of pixels for displaying an image by turning on and off the pixels,
In order to express the gradation of the image with the lighting and non-lighting periods of each pixel in the display unit, when the value of gradation data in the display unit based on an input image signal exceeds a predetermined value, the display is stopped. And a drive control unit including a configuration for controlling the period of lighting and non-lighting of each pixel of the unit so that the rate of change in luminance in the display unit is reduced, so that the temperature rise of the display unit is suppressed. Since an optimal driving method can be adopted, it is possible to obtain a plasma display device in which the performance degradation of the display unit is suppressed, the heat radiation mechanism can be reduced, and the power supply circuit can be configured small.

[Brief description of the drawings]

FIG. 1 is an external view schematically showing an example of a plasma display panel according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram schematically showing a configuration of a plasma display device according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram for explaining a gray scale display operation in the plasma display device according to the embodiment of the present invention;

FIG. 4 is a block diagram showing a configuration of an overall control function unit of the plasma display device according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an average luminance-average gradation characteristic per pixel of the plasma display device according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an average luminance-average gradation characteristic per pixel by another control method of the plasma display device according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram for describing control characteristics of the plasma display device according to the first embodiment of the present invention.

FIG. 8 is an explanatory diagram for describing a control characteristic by another control of the number of discharges of the plasma display device according to the first embodiment of the present invention;

FIG. 9 is a block diagram showing another configuration of the overall control function unit of the plasma display device according to the first embodiment of the present invention.

FIG. 10 is an explanatory diagram illustrating the concept of a plasma display device according to a second embodiment of the present invention.

FIG. 11 is an explanatory diagram for explaining the concept of a plasma display device according to a second embodiment of the present invention.

FIG. 12 is a block diagram showing a configuration of a partial control function unit of a plasma display device according to a second embodiment of the present invention.

FIG. 13 is an explanatory diagram for describing a control method in the plasma display device according to the second embodiment of the present invention.

FIG. 14 is an explanatory diagram for describing a control method when using the partial control function unit in the plasma display device according to the second embodiment of the present invention.

FIG. 15 is an explanatory diagram illustrating another control method when using the partial control function unit in the plasma display device according to the second embodiment of the present invention.

FIG. 16 is a block diagram showing another configuration of the drive control circuit according to the embodiment of the present invention.

FIG. 17 is an explanatory diagram of a configuration for performing temperature control in a conventional display device.

[Explanation of symbols]

1000 plasma display device, 500 PD
P, 5X electrode, 4Y electrode, 6W electrode, 141X
Electrode drive circuit, 142 Y electrode drive circuit, 143 W electrode drive circuit, 110 drive control circuit, 111 full screen control function section, 112 full screen average gradation calculation section, 113 discharge count control section, 114, 118 write data output section, 32 section area, 30 display section, 31 non-display section, 33 temperature measurement position, 115 partial control function section, 116 area average gradation calculation section.

Claims (15)

[Claims] 1. A display unit comprising a large number of pixels, an average grayscale data of an image signal is obtained based on an input image signal, and the average grayscale data is displayed on the display unit according to a value of the average grayscale data. And a drive control unit including a configuration for controlling the luminance of an image to be displayed. 2. The display device according to claim 1, wherein the average gradation data is obtained as an average per pixel in the display unit. 3. The display device according to claim 1, wherein the average gradation data is obtained as an average per divided area composed of a plurality of pixels in the display unit. 4. The display device according to claim 1, wherein when the average gradation data exceeds a predetermined value, the change rate of the luminance with respect to the number of pixels is changed. 5. The display device according to claim 4, wherein when the average gradation data exceeds a predetermined value, the rate of change in luminance with respect to the number of pixels is reduced. 6. A temperature sensor is provided corresponding to each of the divided areas, and the brightness of an image displayed is controlled based on temperature data detected by the temperature sensor. 3. The display device according to 3. 7. The display device according to claim 1, wherein a luminance of an image to be displayed is controlled based on a weight coefficient corresponding to a pixel position in at least one of the first direction and the second direction on the display unit. The display device according to claim 1. 8. An image displayed on a display unit composed of a large number of pixels according to an average tone data of the image table signal based on an input image signal. A display method characterized by controlling the brightness of a display. 9. The display method according to claim 8, wherein the average gradation data is obtained as an average per pixel in the display unit. 10. The display method according to claim 8, wherein the average gradation data is obtained as an average per divided area composed of a plurality of pixels in the display unit. 11. The display method according to claim 8, wherein when the average gradation data exceeds a predetermined value, the rate of change in luminance with respect to the number of pixels is changed. 12. The display method according to claim 11, wherein when the average gradation data exceeds a predetermined value, the rate of change in luminance with respect to the number of pixels is reduced. 13. The display method according to claim 10, wherein the brightness of an image to be displayed is controlled based on temperature data measured corresponding to the divided area. 14. The brightness of an image to be displayed is controlled based on a weighting factor corresponding to a pixel position in at least one of the first direction and the second direction on the display unit. 14. The display method according to any one of claims 1 to 13. 15. A display section comprising a number of pixels for displaying an image according to the lighting or non-lighting state of the pixel, and the gradation of the image is expressed by a lighting or non-lighting period of each pixel in the display section. Therefore, when the value of the gradation data in the display unit based on the input image signal exceeds a predetermined value, the lighting and non-lighting periods in each of the pixels of the display unit are changed by a change in the brightness in the display unit. And a drive control unit including a configuration for controlling the rate to decrease.