JP3238365B2 - Display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device suitable for a plasma display device, and more particularly to an improvement for preventing a display screen from being damaged.

[0002]

2. Description of the Related Art In recent years, a plasma display device has been put into practical use as a display device of a large wall-mounted television. The plasma display device is a self-luminous PD
P (plasma display panel)
It has a feature that it can realize a large screen, a thin shape, a high viewing angle, and a high luminance, and is expected as a display device replacing a CRT device. On the other hand, in the plasma display device, heat is generated on a glass surface which is a component of the display screen with light emission when displaying an image. When the brightness of the image is increased, the amount of heat generated increases, and the temperature of the glass surface increases.

For example, when an image in which only a part of the display screen is bright is displayed, the temperature locally rises and an extreme temperature difference occurs on the glass surface. Therefore, there is a problem that unnecessary stress is generated on the glass surface due to expansion at only the portion of the glass surface where the temperature has increased, and as a result, the glass surface is broken in the worst case. In order to avoid this, a countermeasure for displaying an image with reduced luminance is conceivable. However, this countermeasure has problems in viewability of an image and image quality, and is not practical.

As a technique for solving this problem, Japanese Patent Application Laid-Open No. Sho 62
-75588 discloses a display device in which luminance control is performed. FIG. 24 shows an example of a conventional display device disclosed in this publication. This display device is configured as a plasma display device. A display unit 94 having a display screen 97 is connected to a display controller unit 92 through wires 95 and 96. The display controller 9
2 is connected to an input terminal 91.

[0005] The display controller 92 performs data conversion on the image signal arriving at the input terminal 91 so that the image signal can be displayed on the display 94. The data-converted signal is supplied to the display unit 94 via a line 95 together with a drive control signal for driving the display unit 94.

The display controller 92 further counts the number of pixels displayed on the display unit 94, that is, the number of display pixels, and outputs a control signal for lowering the luminance according to the number Np of display pixels. , As a luminance control signal. The generated luminance control signal is supplied to the display unit 94 via the wiring 96.

[0007] The display unit 94 displays an image based on the converted image signal supplied through the wiring 95 and responds to the luminance control signal supplied through the wiring 96 to display the overall luminance of the display screen 97. to correct. The display unit 94 has a built-in brightness adjustment circuit for changing the brightness of the image in response to the brightness control signal, and the brightness adjustment circuit corrects the brightness. The display device shown in FIG. 24 is naturally provided with a power supply circuit and a power supply wiring for supplying power to each part of the device (not shown).

FIG. 25 shows a display controller 2
Is a graph showing the relationship between the luminance controlled by the display and the number of display pixels. As shown in FIG. 25, when the number of display pixels Np is small, the luminance is set high. On the other hand, as the number Np of display pixels becomes higher than the reference value N0 (for example, the number of pixels corresponding to 50% of the total number of pixels), the brightness is reduced. In this way, the luminance is controlled so that the temperature does not increase as the number of display pixels Np increases.

Although the number of display pixels Np may be detected based on an image of one frame, a mode is also known in which the number of display pixels is detected based on an average value of images of a plurality of frames. The mode based on the average value of the images of a plurality of frames has an advantage that a change in the luminance of the display screen 97 due to the luminance control signal is hardly perceived by human eyes, thereby realizing a more practical and effective image display. .

[0010]

However, in the conventional display device, the number of display pixels on the entire display screen 97 is detected, and the luminance is controlled in accordance with the detection result, thereby suppressing the temperature rise. There were the following problems. That is, an image in which only a part of the display screen 97 is bright, for example, 20
When a white window image or the like having a size of% is displayed, since the control for lowering the luminance is not performed, the temperature locally increases. As a result, there was a problem that the glass surface was broken as described above.

If the reference value N0 is set low to a value of 20% or less, the luminance is reduced, and as a result, the rise in temperature can be suppressed. Will be lowered. That is, the luminance is unnecessarily reduced for most of the images, which causes problems in viewability of images and image quality.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems in the conventional apparatus, and it is an object of the present invention to effectively prevent a display screen from being damaged due to a rise in temperature without deteriorating the quality of a displayed image. It is an object of the present invention to provide a display device which enables the display.

[0013]

According to a first aspect of the present invention, there is provided a display device including a display unit having a single display panel for displaying an image based on an image signal;
Control means for controlling the operation of the a section , wherein the control means
Is based on the luminance correction coefficient for the input image signal
Apply the correction to generate a corrected image signal, and
By outputting an image signal to the display unit
Brightness for controlling the brightness of the image displayed on the display panel
A correcting unit, setting a plurality of areas on the display panel,
Of the corrected image signal in each area for each area
Calculates the average value and performs new brightness correction based on this average value.
Generate a new coefficient for the brightness correction unit.
And a temperature prediction control section for outputting, and the brightness correction section has a new
Newly generated corrections to the input image signal
It is performed based on the calculated brightness correction coefficient .

[0014]

[0015]

Further, according to the display device of the present invention, the temperature prediction control section generates a new luminance correction coefficient.
Is corrected based on the new luminance correction coefficient.
One frame before the frame of the input image signal
Is performed using the image signal after the correction.
You. According to a third aspect of the present invention, in the display device, the control of the luminance is performed by changing a density of a driving pulse input to the display unit by the control unit .

According to a fourth aspect of the present invention, the plurality of areas of the display panel are set such that the areas do not overlap with each other.

Further, in the display device according to the fifth aspect , the setting of the plurality of regions of the display panel includes a setting performed so that each region has a portion overlapping each other.

Further, the display apparatus according to claim 6, control of the luminance, flat image signal within each area
Characterized in that it is performed based on the maximum value of the average value.

[0020] The display device according to claim 7, control of the luminance, flat image signal in each region
When the maximum value among the average values exceeds a predetermined reference value, the method includes a control for lowering the luminance.

The display device according to claim 8 , wherein the predetermined reference value includes a plurality of reference values, and the maximum value among the average values of the image signals in each area is one of the plurality of reference values. It is characterized in that the luminance reduction rate in the control for lowering the luminance is changed depending on whether or not it has exceeded.

According to a ninth aspect of the present invention, the control of the luminance is performed based on the maximum value of the difference between the average values of the image signals in areas adjacent to each other.

According to a tenth aspect of the present invention, in the display device, the control of the luminance is performed when the difference between the average value of the image signal before a predetermined time and the average value of the current image signal is equal to or less than a predetermined value for each area. And a control for lowering the luminance.

Further, the display device according to the eleventh aspect is characterized in that the calculation of the average value of the image signal is performed for one area each time an image of one frame is displayed.

A display device according to a twelfth aspect is characterized in that the control of the luminance is performed by changing the overall luminance of the display panel.

A display device according to a thirteenth aspect of the present invention is characterized in that the control of the luminance is performed by increasing the rate of decrease in the luminance at the peripheral portion of the display panel than at the central portion.

The display device according to a fourteenth aspect is characterized in that the control of the luminance is performed using a different luminance reduction rate for each area of the display panel.

Further, a display device according to a fifteenth aspect comprises a first power supply for supplying power to the display device, and a circuit independent of the first power supply. A second power supply for supplying power for calculating an average value of the image signal for each area in the control unit even while the supply is stopped. Further, the display device according to claim 16 , a capacitor that stores a part of the electric power supplied to the display device as electric energy, and a timer that measures an elapsed time from when the power supply of the display device is cut off, Having a non-volatile memory, when the power of the display device is cut off,
The average value of the image signal for each area is calculated using the electric energy stored in the capacitor, the result is stored in the nonvolatile memory, and then, when the display device is powered on, and calculates an average value of the image signal of each of the areas by using the value of the average value stored in the nonvolatile memory timer. The display device according to claim 17, wherein
The generation of the luminance correction coefficient by the temperature prediction control unit
Prediction for each area obtained based on the average value of image signals
It is performed using temperature . Claims
The display device according to Item 18 , wherein the predicted temperature for each region is calculated based on a predicted heat release amount in each region based on an average value of the image signals and a predicted heat release amount in each region.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. First Embodiment First, a display device according to a first embodiment of the present invention will be described.

<1-1. Outline of Apparatus> FIG.
FIG. 2 is a block diagram showing a configuration of a display device of FIG. This device is a display device, for example, a plasma display device, which can cause a temperature rise on the display screen when an image is displayed on the display screen. In addition to the display unit 4 and the display controller unit 2, the temperature prediction control unit 3 It has. The display controller 4 is connected to the display unit 4 having the display screen 50 via the wiring 17. The input terminal 1 is connected to the display controller 2, and the temperature prediction controller 3 is connected to the display controller 2 through wires 5 and 6.

The display controller 2 performs data conversion on the image signal arriving at the input terminal 1 so that the image signal can be displayed on the display 4. The converted image signal is supplied to the display unit 4 via the line 17. The temperature prediction control unit 3 includes a display screen 5
The temperature at 0 is predicted, and a luminance control signal is generated based on the predicted temperature. The generated brightness control signal is input to the display controller 2 through the wiring 6.

Prior to performing data conversion on the image signal input through the input terminal 1, the display controller 2 corrects the luminance of the image signal based on the luminance control signal. Temperature prediction control unit 3
Receives the signal after the luminance is corrected through the wiring 5 and predicts the temperature based on the received signal (received signal).

The display unit 4 corrects the luminance,
Further, the converted signal is input. Therefore, the display unit 4 is the display unit 9 of the conventional device.
Unlike the case of No. 4, a brightness adjustment circuit may not be provided.
The display device of FIG. 1 is also provided with a power supply circuit and a power supply wiring for supplying power to each part of the device (not shown), similarly to the conventional device of FIG.

<1-2. Display Controller> FIG.
3 is a block diagram showing an internal configuration of the display controller 2. FIG. As shown in FIG. 2, the display controller 2 includes a data converter 62 and a brightness corrector 61.
And equipped. The data conversion unit 62 is a device part also provided in the conventional display controller unit 92 shown in FIG. The other luminance correction unit 61
Is a device portion that performs the same function as the brightness adjustment circuit (not shown) provided in the conventional display unit 94 shown in FIG. 1, but in that the brightness of the signal before conversion is corrected. This is different from the conventional brightness adjustment circuit.

The image signal of the current frame (current frame) input to the display controller 2 through the input terminal 1 is input to the luminance corrector 61. The image signal includes a color difference signal and horizontal and vertical synchronization signals (not shown) in addition to the luminance signal P (t). On the other hand,
The brightness control signal input from the temperature prediction control unit 3 to the brightness correction unit 61 via the wiring 6 expresses a brightness correction coefficient B (t) which is a ratio for weakening the intensity of the brightness signal P (t).

The luminance correction section 61 performs correction based on a luminance correction coefficient B (t) on the luminance signal P (t) included in the input image signal. The correction is performed according to the following equation (1). A (t) = B (t) × P (t) (1) That is, by multiplying the luminance signal P (t) by the luminance correction coefficient B (t), the luminance signal P (t) is obtained. ) Is converted to a corrected luminance signal A (t). The corrected luminance signal A (t) is sent to the data converter 62 together with the color difference signal and the horizontal and vertical synchronization signals.

The data conversion unit 62 receives an input of an image signal corrected for the luminance signal P (t), converts the input image signal into a format compatible with the display unit 4, Supply to 4. That is, the signal input to the display unit 4 includes the converted corrected luminance signal A (t) ^* obtained by converting the corrected luminance signal A (t).

Accordingly, an image whose luminance has been corrected based on the luminance correction coefficient B (t) is displayed on the display screen 50. That is, when the brightness correction coefficient B (t) is a value (B (t) = 1) for which the brightness is not corrected, the image is displayed on the display screen 50 with the standard brightness. On the other hand, when the brightness correction coefficient B (t) is a value that reduces the brightness (for example, B (t) = 0.7), the image is displayed darker than the standard.

The corrected luminance signal A (t) generated by the luminance correction section 61 is input to the temperature prediction control section 3 through the wiring 5 together with the horizontal and vertical synchronization signals. The temperature prediction control unit 3 predicts a temperature based on the corrected luminance signal A (t), and further generates a luminance correction coefficient B (t).

When the device is configured as a plasma display device, the display controller unit 2 has a drive control for driving the display unit 4 similar to the conventional display controller unit 92 (not shown). A device for generating a signal is provided, and the generated drive control signal is transmitted to the display unit 4 together with the converted corrected luminance signal A (t) ^{* and the} like. Also,
Brightness signal P (t), brightness correction coefficient B (t), corrected brightness signal A
A variable "t" included in a code such as (t) represents the current frame, and variables such as "t-1", "t-2",. .., J frames from the frame are represented.

<1-3. Calculation of Predicted Temperature> FIG. 3 is a block diagram showing the internal configuration of the temperature prediction control unit 3. The temperature prediction control unit 3 includes, as main elements, an average value calculation unit 8, a register unit 9, a reference temperature storage unit 10, and a determination unit 11
Is provided. The average luminance calculator 8 receives the corrected luminance signal A (t) and the horizontal / vertical synchronization signal through the wiring 5. A part of the determination unit 11, the average value calculation unit 8, and the register unit 9 constitute a predicted temperature calculation unit 73.

As shown in the operation explanatory diagram of FIG. 4, the average value calculating section 8 conceptually changes the display screen 50 of the display section 4 to a plurality of blocks (areas) BK ₁ based on the horizontal and vertical synchronizing signals. ~ BK _N and block BK ₁ ~ B
For each of K _N , the average value S ₁ (t) of the corrected luminance signal A (t),
S ₂ (t),..., S _N (t) are calculated. FIG. 4 shows an example in which the number N of blocks is 12 (N = 12).

Returning to FIG. 3, the calculated average value S ₁ (t),
S ₂ (t),..., S _N (t) are temporarily stored in the register unit 9. As described above, the register section 9 stores the average values S ₁ (t), S ₂ (t),..., S _N (t) for each frame. The stored average values S ₁ (t), S ₂ (t),..., S _N (t)
Is read by the determination unit 11 for each frame. That is, the judging unit 11 reads out the average values S ₁ (t−1), S ₂ (t−1),..., S _N (t−1) one frame before from the register unit 9.

FIG. 5 is a block diagram showing the internal configuration of the judgment unit 11. The determining unit 11 includes a predicted temperature calculating unit 21,
Predicted temperature storage unit 20, maximum value calculation unit 22, comparison unit 23,
And a correction coefficient calculating section (buffer section) 24.
The above-described predicted temperature calculation unit 73 also includes the predicted temperature calculation unit 21 and the predicted temperature storage unit 20. Further, the maximum value calculation unit 22, the comparison unit 23, and the correction coefficient calculation unit 24
Constitutes a correction control section 72 for controlling the correction operation in the luminance correction section 61 based on the predicted temperature. Judgment unit 1
1 may be composed of only hardware, and CP
U and software stored in the memory may be equivalently configured.

Average value S read from register section 9
₁ (t-1), S ₂ (t-1),..., S _N (t-1) are input to the predicted temperature calculation unit 21. The predicted temperature calculation unit 21 calculates a predicted temperature value for each of the plurality of blocks BK _{1 to} BK _N , that is, predicted temperatures T ₁ (t), T ₂ (t),..., T _N (t). It is calculated based on the average values S ₁ (t-1), S ₂ (t-1),..., S _N (t-1). A predicted temperature storage unit 20 is connected to the predicted temperature calculation unit 21, and the calculated predicted temperatures T ₁ (t), T ₂ (t),.
, T _N (t) are written to the predicted temperature storage unit 20.

The predicted temperature calculator 21 calculates the predicted temperature T ₁ (t),
When calculating T ₂ (t),..., T _N (t), the data stored in the predicted temperature storage unit 20, that is, the predicted temperature T ₁ (t-1) calculated one frame before. , T ₂ (t-1), ..., T _N (t-1)
Is read and referenced. These predicted temperatures T ₁ (t-1), T
_{2 (t-1), ···} , T N (t-1) is the average value of _{S 1 (t-1),} S 2 (t-
1), ..., the average value of the further previous frame than _{S N (t-1) S} 1 (t-2), S 2 (t-2), ···, S N (t-2) It is a value calculated based on this.

Immediately after the power is turned on, the predicted temperature T
_{When 1} (t), T ₂ (t),..., T _N (t) are calculated for the first time, the predicted temperatures T ₁ (t-1), T ₂ (t-1),.・ 、
For example, an initial value “0” is used as T _N (t−1).
For this purpose, for example, the value stored in the register unit 9 may be initialized to an initial value “0” immediately after power-on. At this time, the predicted temperatures T ₁ (t), T ₂ (t),.
_N (t) corresponds to the initial temperature of the display screen 50 or the temperature rise based on the outside air temperature.

The predicted temperatures T ₁ (t), T ₂ (t),..., T _N (t)
Is calculated based on the following Expression 2. _Tn (t) = K1 × [ _Sn (t−1) + α] + (1−K2) × _Tn (t−1) (2) where the variable n is the block BK ₁ ... BK _N is a variable indicating that the value is for an arbitrary block BK _n , and takes all values in the range of n = 1 to _N. Coefficient K1,
K2 is 0 <K1 ≦ 1 and 0 <K2 ≦
It is a constant set in the range of 1. The constant α is a constant corresponding to the temperature rise during one frame when an image is not displayed on the display screen 50. For example, when the device is a plasma display device, the temperature rise caused by a pilot discharge Corresponding to

Equation (2) expresses that the rate of change of temperature depends on the amount of heat generation and the amount of heat radiation in a linear relationship, and that the amount of heat radiation is proportional to the temperature. For this reason,
When the average value S _n (t) is constant, the predicted temperature T _n (t)
Changes along an exponential function, and eventually converges to a steady state. That is, Equation 2 predicts a change in temperature on the display screen 50 in the simplest form and with high accuracy. FIG. 6A and FIG.
(B) is a graph illustrating this. That is, in FIG. 6 (a), FIG. 6 (b), the average value S _n in the block BK _n (t), and, the variation along the time predicted temperature T _n (t), are respectively illustrated .

[0050] FIG. 6 (a), in FIG. 6 (b), the after the power is turned on at time 0, after the elapse until a time t1, the display image is started on the display screen 50 including the block BK _n It is assumed that the display of the image at a constant luminance is continued until time t2, and the display of the image is stopped at time t2. At this time, as shown in FIG. 6 (a), in the period from time 0 to t1, an average value S _n (t) = 0, in a period of time t1 to t2, an average value S _n (t) = Constant value (> 0), and the average value _Sn (t) = 0 after time t2.

The predicted temperature T _n (t) is calculated as follows for the average value S _n (t) that changes in this way. During the period from time 0 to t1, no image is displayed, and the average value S _n (t)
Is zero, the predicted temperature T _n (t) has increased somewhat, as shown in FIG. This rise in temperature is derived from the constant α. For example, when the device is a plasma display device, the rise in temperature reflects the rise in temperature due to pilot discharge. Predicted temperature T during this period
The change in _n (t) is represented by an exponential function that asymptotically approaches a certain value defined by a constant α.

In the period from time t1 to t2, the average value S _n (t)
Is high, reflecting this, the predicted temperature T
_n (t) soars. Since the average value S _n (t) is a constant value, the change in the predicted temperature T _n (t) at this time is also expressed by an exponential function. Then, the predicted temperature T _n (t) converges to a certain value while changing along the exponential function. After time t2, since the average value S _n (t) is zero, the predicted temperature T _n (t) decreases rapidly. The change in the predicted temperature T _n (t) at this time is also expressed by an exponential function. Then, the predicted temperature T _n (t)
Converges to a constant value defined by a constant α while changing along an exponential function.

6 (a) and 6 (b), the asymptotic value of the predicted temperature T _n (t) at the time t1 to t2 is changed to the reference temperatures T1 and T2 described later (in FIG. Drawn with
So that the average value S ₁ (t), S
_It is assumed that ₂ (t),..., S _N (t) are not excessively high.

<1-4. Calculation of Brightness Correction Coefficient B (t)> Returning to FIG. 5, the predicted temperature T calculated by the predicted temperature
₁ (t), T ₂ (t),..., T _N (t) are written to the predicted temperature storage unit 20 and also input to the maximum value calculation unit 22. The maximum value calculator 22 calculates the predicted temperatures T ₁ (t), T ₂ (t),
, T _N (t), the largest value is searched for, and the value is input to the comparing unit 23 as the maximum value Tmax. Comparison section 23
Is connected to a reference temperature storage unit 10. In the reference temperature storage unit 10, reference temperatures T1 and T2 (T1 <T2), which are predetermined constants, are stored in advance. Comparison section 2
3 compares the maximum value Tmax with the reference temperatures T1 and T2, and calculates a target value C (t) of the luminance correction coefficient B (t) based on the comparison result.

FIG. 7 is a graph for explaining the operation of the comparison unit 23. As shown in FIG.
Performs a comparison that incorporates the hysteresis characteristics. That is, when the maximum value Tmax is a value lower than the one reference temperature T1, a standard value “1” for realizing the standard brightness of the image is added to the target value C (t), and the other reference temperature Tmax is used. T
When the value is higher than 2, a value lower than the standard value "1", for example, "0.7" is given.

When the target value C (t) is the standard value "1", the target value C (t) becomes the standard value "1" when the maximum value Tmax becomes higher than the reference temperature T2. Is reduced to a value of "0.7". On the other hand, when the maximum value Tmax is the value "0.7", the target value C (t) is raised from the value "0.7" to the standard value "1" when the maximum value Tmax becomes lower than the reference temperature T1. Can be

The calculated target value C (t) is input to the correction coefficient calculator 24. The correction coefficient calculation unit 24 calculates a luminance correction coefficient B (t) based on the target value C (t). The brightness correction coefficient B (t) is calculated as a coefficient that increases or decreases so as to gradually approach the target value C (t). For example, after the target value C (t) changes, the brightness correction coefficient B (t) changes smoothly over a period of 10 seconds, and the target value C (t) changes.
To reach. The calculated luminance correction coefficient B (t) is
To the luminance correction unit 61 (FIG. 2), and is used to calculate a corrected luminance signal A (t). That is, the brightness correction unit 61 and the temperature prediction control unit 3 form a feedback loop.

<1-5. Operation Example> Since the luminance correction coefficient B (t) changes with a hysteresis characteristic with respect to the change of the maximum value Tmax, an oscillation phenomenon appears in the luminance correction coefficient B (t). Can be prevented. Also, the brightness correction coefficient B
Since (t) slowly follows the target value C (t) over time, an advantage is obtained in that the change in the luminance of the image displayed on the display screen 50 is visually inconspicuous. FIGS. 8A and 8B are graphs illustrating such characteristic operations.

In FIGS. 8A and 8B, the block B
An operation example in which the predicted temperature T _n (t) at K _n is the highest, and as a result, the maximum value T max = predicted temperature T _n (t) is shown. That is, the time t1 after the power is turned on.
, The average value S in the blocks BK _{1 to} BK _{N
Among the 1} (t), S ₂ (t),..., S _N (t), the average value S _n (t) for the block BK _n becomes the highest value, and the more the temperature rises, the more the temperature rises. Is expected to be high.

As a result, after time t1, the predicted temperature T _n (t) rises sharply. Since the average value _Sn (t) is excessively high, the predicted temperature _Tn (t) eventually exceeds the reference temperature T2. Then, as a result of the target value C (t) being reduced by the comparison unit 23, the luminance correction coefficient B (t) thereafter gradually decreases from the value "1" to the value "0.7" over, for example, 10 seconds.
As a result, the overall luminance of the display screen 50 gradually decreases over 10 seconds. Accordingly, the average value S _n (t)
Also decreases to a lower value over 10 seconds.

The decrease in the average value S _n (t) is also reflected on the predicted temperature T _n (t). That is, the predicted temperature T _n (t) is _{equal to} the time t2
After that, it turns from rising to falling. Predicted temperature T
_n (t) converges to a certain value after turning down.
At this time, the reference temperature T1 is set so that the value that converges does not become lower than the reference temperature T1.

At the subsequent time t3, the average value S _n (t)
Changes to a lower value in response to a change in the luminance signal P (t) input from the outside, the predicted temperature T _n (t) starts to decrease again accordingly. If the predicted temperature T _n (t) exceeds the reference temperature T1 at the time of the decrease, for example, at time t4, the comparison unit 23 reduces the target value C (t) to a low value “0.7”.
From "1" to the standard value "1".

As a result, the overall luminance of the display screen 50 becomes
Over 10 seconds, it slowly rises to the uncorrected standard brightness. Accordingly, the average value _Sn (t) also shifts to a higher value in 10 seconds. Reflecting this, the predicted temperature T _n (t) turns from falling to rising after time t4. The predicted temperature T _n (t) converges to a certain value after turning to rising. At this time, the reference temperature T2 is set so that the value that converges does not become lower than the reference temperature T2.

<1-6. Advantages and Modifications of Apparatus> As described above, in the apparatus of this embodiment, the display screen 50 is divided into a plurality of blocks BK _{1 to} BK _N.
Since the temperature is predicted and the brightness of the entire screen is corrected based on the highest predicted temperature, the display screen 50 can be prevented from being damaged due to a local temperature rise. Moreover, even when the brightness is uniform over the entire display screen 50, the brightness is not corrected unless the brightness is so high that the temperature rise exceeds the reference value.
Can be prevented without deteriorating the image quality.

Also, the comparison taking the hysteresis characteristic into place in the comparing section 23 causes an oscillation phenomenon in which the luminance corrected based on the predicted temperature T _n (t) repeatedly rises and falls. Can be prevented. In order to prevent the oscillation phenomenon, the reference temperatures T1, T
2 and the lower value of the target value C (t) (for example, the value “0.7”)
Are optimized in relation to each other.

Further, since the brightness of the image displayed on the display screen 50 changes gradually when it changes with the correction, there is no visual unnaturalness. That is, it is possible to prevent the display screen 50 from being damaged due to a rise in temperature without deteriorating the image quality.

The predicted temperatures T ₁ (t), T ₂ (t),..., T _N
Since the change in (t) is more gradual than the change in the average values S ₁ (t), S ₂ (t),..., S _N (t), the two reference temperatures T1, T
Instead of setting 2 and performing control with hysteresis characteristics, a single reference temperature may be set and control without hysteresis characteristics may be performed. Even with such control, the reduction in visual image quality is not so much as to impair practicality. This control is equivalent to setting the values of the reference temperatures T1 and T2 stored in the reference temperature storage unit 10 to T1 = T2.

For the same reason, the luminance correction coefficient B
The value of (t) may be set so as to always be equal to the target value C (t) without gradually following the target value C (t). This is equivalent to directly inputting the target value C (t) as the luminance correction coefficient B (t) to the luminance correction unit 61 without providing the correction coefficient calculation unit 24.

Further, since the target value C (t) is a signal representing two values, it may be a binary signal merely representing ON / OFF. At this time, the correction coefficient calculation unit 24
It is preferable that the luminance correction coefficient B (t) is asymptotically or matched to a predetermined value based on the on / off signal. Further, the correction coefficient calculation unit 24 may be provided in the display controller unit 2 or the brightness correction unit 61 instead of being provided in the temperature prediction control unit 3.

<2. Second Embodiment> In the first embodiment, the comparator 23 assigns two-step values including the standard value “1” to the target value C (t). However, in general,
The target value C (t) may be given three or more levels.
Here, an example will be described.

The temperature prediction control unit 3 shown in the block diagram of FIG.
, T6 are stored in advance. Then, the comparison unit 23 (FIG. 5) provided in the judgment unit 11 calculates the maximum value Tmax and the reference temperatures T1,.
6 (T1 <... <T6), and a target value C (t) is determined based on the comparison result.

That is, the target value C (t) includes the maximum value Tmax
Are given in four levels including the standard value "1" according to the magnitude of Then, the standard value “1” in the top row and the value in the second row “
The transition of the target value C (t) between the reference temperature T
1, and T2, in the same manner as in FIG. 7, taking into account the hysteresis characteristics. Similarly, the value “0.
The transition of the target value C (t) between 9 "and the third stage value" 0.8 "is
It is determined based on the reference temperatures T3 and T4. further,
Target value C between the third-stage value "0.8" and the fourth-stage value "0.7"
The transition of (t) is determined based on the reference temperatures T5 and T6.

As described above, the target value C (t) is given a multi-step value in accordance with the magnitude of the maximum value Tmax. For this reason, since the correction of the brightness is performed more delicately, it is possible to prevent the display screen 50 from being damaged due to a rise in temperature while maintaining a high image quality without unnecessarily lowering or raising the brightness. Becomes Moreover, the target value C
Since a hysteresis characteristic is provided between the change of (t) and the change of the maximum value Tmax, it is possible to prevent an oscillation phenomenon from appearing in the corrected luminance.

The predicted temperatures T ₁ (t), T ₂ (t),..., T _N
The change in (t) is the average value S ₁ (t), S ₂ (t),.
_Since the change is slower than the change in _N (t), the number of set values of the target value C (t) other than the standard value “1” (3 in the example of FIG. 10).
And the control without the hysteresis characteristic may be performed by setting the same number of reference temperatures as the reference temperature. Even with such control, the reduction in visual image quality is not so much as to impair practicality. This control is performed by the reference temperature storage unit 10 shown in FIG.
.., T6 stored in
= T2, T3 = T4, and T5 = T6.

<3. Third Embodiment> In the first and second embodiments, the blocks BK _{1 to} BK _N obtained by dividing the display screen 50 are used.
Shows an example in which the blocks BK ₁ are independent of each other.
~ BK _N may be set to overlap with each other. For example, as shown in an explanatory diagram of FIG. 11, the display screen 50 includes blocks BK ₁ that do not overlap each other.
And ~BK _M, block BK _M + 1 _{~BK N} to duplicate these
And may be divided into In FIG. 11, N = 18 and M = 1
Two examples are depicted.

[0076] Mean value calculation unit 8 (FIG. 3), irrespective of whether overlap is between these blocks BK ₁ ~BK _N, in the manner described in the first embodiment, the block BK ₁ ~
Average value S of corrected luminance signal A (t) corresponding to each of BK _N
1 (t), S ₂ (t),..., S _N (t) are calculated. Then, the predicted temperature calculating section 21 (FIG. 5) calculates the predicted temperatures T ₁ (t), T ₂ (t),... Corresponding to each of the blocks BK _{1 to} BK _N in the manner described in the first embodiment.・, T _N (t) is calculated. Further, the comparing unit 23 determines these maximum values as the maximum value Tmax.

[0077] Thus, as illustrated in FIG. 11, for example, the portion corresponding to the boundary of the block BK ₁ ~BK _M,
When the window image 51 is displayed, the fact that the luminance of the portion of the window image 51 is excessively high is correctly reflected on the value of the average value S _m (t) in the block BK _m including the window image 51. As a result, a high value is calculated as the predicted temperature T _m (t) in the block BK _m .
The correction of the luminance is appropriately performed. in this way,
Since the blocks BK _{1 to} BK _N are set in an overlapping manner, damage to the display screen 50 due to a local temperature rise can be prevented.
More properly prevented.

<4. Fourth Embodiment> In the display device, when the power is turned on, the power is turned off, and the power is turned on again before the temperature of the display screen 50 does not cool down to the outside air temperature. It can be done. At this time, if a value “0” corresponding to the outside air temperature is given as an initial value of the predicted temperatures T ₁ (t), T ₂ (t),..., T _N (t), Temperature T ₁ (t), T ₂ (t),..., T _N (t)
However, it may be underestimated.

The device of the fourth embodiment shown in the block diagram of FIG. 12 is a device configured to prevent this. In this device, the power supply unit 30 is provided with two power supplies, a main power supply 31 and a sub power supply 32. The sub power supply 32
The main power supply 31 is a power supply that supplies power to the determination unit 11.
Is a power supply for supplying power to each device other than the determination unit 11. When not using the device,
Only the main power supply 31 is shut off. For this reason, even if the other device parts stop operating, only the determination unit 11 continues the operation.

Since the main power supply 31 is shut off, the judgment unit 11 provides the new average values S ₁ (t), S ₂ (t),..., S _N (t).
Is not supplied. However, since the main power supply 31 is shut off, the brightness of the display screen 50 is zero, and the average values S ₁ (t), S ₂ (t),..., S _N (t) are originally zero. It is. Further, the constant α corresponding to pilot discharge or the like also becomes zero. For this reason, the predicted temperature calculation unit 21 provided in the determination unit 11 (FIG. 5)
Is the average value S ₁ (t−
Instead of reading 1), S ₂ (t−1),..., S _N (t−1), use the value “0” as their value, further, set the constant α to zero, and Predicted temperatures T ₁ (t), T ₂ (t),
..., T _N (t) is calculated.

As a result, the predicted temperatures T ₁ (t), T ₂ (t) _,.
The calculation of (t) is continued. Thereafter, when the main power supply 31 is turned on, the average value S supplied to the predicted temperature calculation unit 21 is calculated.
₁ (t-1), S ₂ (t-1),..., S _N (t-1) and a normal value as a constant α, and then a predicted temperature T ₁ (t), T ₂ (t),..., T _N (t) are calculated. Therefore, even after the main power supply 31 is turned on before a sufficient period for cooling the display screen 50 is set after the main power supply 31 is turned off, the predicted temperatures T ₁ (t), T
₂ (t),..., T _N (t) can be accurately calculated without underestimating.

[0082] Note that in the period in which the main power supply 31 is cut off, it is not necessary to calculate the luminance correction coefficient B (t), the predicted temperature _{T 1 (t), T 2} (t), ···, T N ( It is sufficient if only t) is calculated continuously. Therefore, the power of the sub power supply 32 does not need to be supplied to all of the determination units 11, but it is sufficient if the power is supplied to the predicted temperature calculation unit 21 and the predicted temperature storage unit 20. The power of the main power supply 31 may be supplied to each part of the determination unit 11 other than the predicted temperature calculation unit 21 and the predicted temperature storage unit 20. However, when the determination unit 11 is equivalently configured by the CPU and the software, the power of the sub power supply 32 is supplied to the entire determination unit 11.

<5. Fifth Embodiment> In a device provided with two power supplies, both power supplies may be cut off, for example, when a power plug inserted into an outlet is pulled out. . At this time, the judgment unit 11
Power supply to the power supply stops. Therefore, even when the supply of power to the determination unit 11 is stopped, when the supply of power is started later, the predicted temperatures T ₁ (t), T ₁
It is further desirable that ₂ (t),..., T _N (t) be calculated with high accuracy. Here, an example will be described.

The temperature prediction control unit 3 shown in the block diagram of FIG. 13 is different from the temperature prediction control units 3 of the first to third embodiments in that it has a timer unit 13 with a battery and a nonvolatile memory unit 14. Are different. The timer unit 13 with battery and the non-volatile memory unit 14
It is connected to one predicted temperature calculation unit 21. The timer unit 13 with a battery includes a timer and a battery (not shown), and the timer is backed up by the battery. Therefore, even when the power is turned off, the timer unit with battery 13 keeps counting the time. Note that the display device including the temperature prediction control unit 3 in FIG. 13 is different from the device in the fourth embodiment and is not premised on having two power supplies.

The operation of the temperature prediction control section 3 in FIG. 13 when the power is turned on is the same as in the first to third embodiments. When the power is cut off, the predicted temperature calculating unit 21
Performs the following characteristic operations. That is,
When the power is turned off, the predicted temperature calculating unit 21 reads the time at which the power is turned off from the timer unit 13 with a battery,
The current predicted temperatures T ₁ (t), T ₂ (t),..., And T _N (t) are stored in the nonvolatile memory unit 14.

The data saving operation is performed after the power is turned off. A capacitor 34 having a sufficient capacity is connected to the power supply terminal of the predicted temperature calculation unit 21 or the power supply terminal of the judgment unit 11 which is in charge of this operation. It can be realized by connecting. In particular, when the determination unit 11 is equivalently configured by the CPU and the software, the capacitor 34 is connected to the power supply terminal of the determination unit 11. When the capacitor 34 is connected to the determination unit 11, it is equivalent to being connected to the predicted temperature calculation unit 21.

When the storage of the data in the non-volatile memory section 14 is completed, only the timer section with battery 13 continues to operate. Thereafter, when the power is turned on, the predicted temperature calculating unit 21
Thus, the power shutdown time and the predicted temperatures T ₁ (t), T ₂ (t),..., T _N (t) stored in the nonvolatile memory unit 14 are read. Next, the current time is set to the timer unit 1 with the battery.
3, the length of the period during which the power supply is shut off, that is, the elapsed time of the shutoff, is calculated.

Next, the initial value of the predicted temperature is determined based on the relationship between the elapsed time and the temperature attenuation coefficient shown in FIG. 14, that is, the cooling characteristic of the display screen 50. FIG.
Is a graph showing the relationship between the elapsed time and the temperature, assuming that the value of the temperature at the time when the power supply is cut off (more precisely, the temperature rise from the outside air temperature) is a value "1", for example, Expressed as an exponential function. The device described above calculates an attenuation coefficient based on the calculated elapsed time and the function shown in FIG.
_{1 (t), T 2 (} t), ···, by multiplying each of T _N (t), the predicted temperature _{T 1 (t), T 2} (t), ···, T N (t) Get the initial value of.

After that, the predicted temperature calculating section 21 performs an arithmetic operation based on Equation 2 using the obtained initial value as a starting point, similarly to the predicted temperature calculating section 21 of the first to third embodiments. The calculated predicted temperatures T ₁ (t) and T ₁ are calculated because the degree of temperature decay when the power is cut off is taken into account.
₂ (t),..., T _N (t) are highly accurate.

In the above example, when the power is cut off, the predicted temperature calculating section 21 sets the N predicted temperatures T ₁ (t), T ₂ (t),.
, T _N (t) are all stored in the non-volatile memory unit 14, but N predicted temperatures T ₁ (t), T ₂ (t),..., T _N (t)
The device may be configured to store a part of. For example, only one predicted temperature T _s (t) (s = 1 to N) may be stored. In this case, the predicted temperature T ₁ (t),
It is more desirable that the maximum value Tmax among T ₂ (t),..., T _N (t) be selected as the predicted temperature T _s (t) to be stored. In the latter case, the predicted temperature calculation section 21 does not need to calculate the maximum value Tmax separately from the calculation of the maximum value calculation section 22, and the maximum value Tmax calculated by the maximum value calculation section 22 is not required.
What is necessary is just to store max in the nonvolatile memory unit 14 as it is.

[0091] Thereafter, when the power is turned on, for example, the predicted temperature T _s which is calculated based on the relationship between the non-volatile memory portion of the power-off to be stored in the 14 predicted temperature T _s (t) and Figure 14 The initial value of (t) is N predicted temperatures T ₁ (t), T
₂ (t),..., T _N (t) are uniformly provided as initial values. Thus, one or more representative values less than N are stored in the non-volatile memory unit 14, and based on the representative values, N predicted temperatures T ₁ (t) and T ₂ ( t) 、 ・ ・
, T _N (t) may be calculated as an initial value.

Alternatively, when the power is turned off, a predetermined plurality of blocks among the _N blocks BK _{1 to} BK N are
Selected as a sampling block, the predicted temperature T
A plurality of values corresponding to the sampling blocks among ₁ (t), T ₂ (t),..., T _N (t) may be stored in the nonvolatile memory unit 14 as representative values. In this case, at the subsequent power-on, each predicted temperature T ₁ (t), T ₂ (t),.
, T _N (t) as the initial values, the corresponding blocks BK ₁ -B
A stored value for the sampling block closest to each of K _N may be provided. As the number of sampling blocks approaches N, the accuracy of the calculated initial value improves.

As described above, when the representative values are used instead of the N predicted temperatures for the calculation of the initial value, the accuracy of the calculated predicted temperature is somewhat inferior. Since the time required for storing the required value in the nonvolatile memory unit 14 is reduced, the advantage that the capacitance of the capacitor 34 can be set small can be obtained. This advantage is most pronounced when a single predicted temperature T _s (t) is used.

In general, when the temperature is attenuated by heat radiation, the temperature becomes uniform with time between the blocks BK _{1 to} BK _N , and the magnitude of the error of the initial value by using the representative value is non-volatile. Calculating the initial value based on the value stored in the memory unit 14 does not impair the significance. In particular, when a single representative value is used, initial the maximum value Tmax is used as a representative value, the predicted temperature _{T 1 (t), T 2} (t), ···, T N (t) As a value, there is an advantage that a value on the safest side can be obtained for the purpose of preventing the display screen 50 from being damaged.

<6. Sixth Embodiment> In the first to fifth embodiments, based on the maximum value Tmax among the predicted temperatures T ₁ (t), T ₂ (t),..., T _N (t). The example in which the brightness is controlled by the above is shown. However, the magnitude of the thermal stress generated on the display screen 50 more directly depends on the temperature difference. Therefore, if the brightness is controlled based on the temperature difference, it is possible to prevent the display screen 50 from being damaged while maintaining a higher image quality. Here, an example will be described.

The decision section 11 shown in the block diagram of FIG.
Are embodiments 1 to 5 in that the temperature difference calculating unit 25 is provided.
Characteristically different from the determination unit 11. That is, the predicted temperatures T ₁ (t), T calculated by the predicted temperature calculation unit 21.
₂ (t),..., T _N (t) are not directly input to the maximum value calculation unit 22, but are first input to the temperature difference calculation unit 25. The temperature difference calculator 25 calculates the predicted temperatures T ₁ (t), T
₂ (t),..., T _N (t), for each of the blocks BK _{1 to} BK
The difference between the predicted temperature for the adjacent block in K _N and the predicted temperature is calculated.

That is, for all n (n = 1 to N), all blocks BK _i adjacent to block BK _n
Is calculated between the predicted temperature T _i (t) and the predicted temperature T _n (t). The maximum value calculator 22 receives the calculated temperature differences T _d1 (t), T _d2 (t),..., T _dK (t).
Therefore, in the maximum value calculation unit 22, the temperature difference T _d1 (t),
The maximum value Tdmax of T _d2 (t),..., T _dK (t) is calculated.
Further, in the comparing section 23, the maximum value Tdmax is compared with, for example, the reference temperatures T1,..., T6 instead of the maximum value Tmax. The subsequent operation is the same as in the first to fifth embodiments.

As described above, since the brightness is controlled based on the maximum value of the temperature difference between the adjacent blocks, the thermal stress generated on the display screen 50 due to the temperature difference is:
Appropriately mitigated. That is, it is possible to prevent the display screen 50 from being damaged while suppressing unnecessary reduction in the brightness of the image displayed on the display screen 50.

<7. Seventh Embodiment> In the first to sixth embodiments, the temperatures or the temperature differences of all the adjacent blocks are compared with each other equally, and the luminance is determined based on the largest value among them. Was controlled. However, in general, each of the blocks BK _{1 to} BK _N can be handled with different weights. In particular, the peripheral portion of the display screen 50 is more likely to generate a larger thermal stress than the central portion. Therefore, depending on the position in the display screen 50, the temperature or the temperature difference is appropriately adjusted. If such weighting can be performed, it can be said that this is advantageous in achieving more accurate control. Here, an example will be described.

The decision section 11 shown in the block diagram of FIG.
Is characteristically different from the determining unit 11 of the first to fifth embodiments in that the weighting unit 41 is provided. That is, the predicted temperatures T ₁ (t), T ₂ (t),
.., T _N (t) are not directly input to the maximum value calculation unit 22, but are first input to the weight addition unit 41.
The weighting unit 41 calculates the predicted temperatures T ₁ (t), T ₂ (t) _,.
(t), for each of the corresponding blocks BK _1-
BK _N are respectively multiplied by weighting factors w ₁ , w ₂ ,..., W _N corresponding to the positions occupied in the display screen 50.

With respect to the values of the weighting factors w ₁ , w ₂ ,..., W _N , for example, the weighting factor of a block located around the display screen 50 is set to the value “1”, and the block is located at the center. , The value of the corresponding weighting factor is set to a lower value. The maximum value calculating unit 22 includes the weight adding unit 4
The weighted predicted temperature w ₁ T ₁ (t), w ₂ T ₂ (t) calculated in step _{1
·, W N T N (t} ) is input. Therefore, the maximum value calculating unit 22 calculates the weighted predicted temperatures w ₁ T ₁ (t), w ₂ T ₂ (t),.
-, the maximum value Twmax of w _N T _N (t) is calculated. Also, in the comparing unit 23, instead of the maximum value Tmax, the maximum value Twmax
Are compared with, for example, reference temperatures T1,..., T6. The subsequent operation is the same as in the first to fifth embodiments.

Thus, the predicted temperatures T ₁ (t), T ₂ (t),.
, T _N (t) is weighted reflecting the contribution of temperature to the thermal stress, and the luminance is controlled.
The thermal stress generated on the display screen 50 is reduced more appropriately. That is, unnecessary reduction of the brightness of the image displayed on the display screen 50 is effectively suppressed, and it is possible to prevent the display screen 50 from being damaged while maintaining higher image quality.

The judgment unit 11 shown in FIG.
₁ (t), T ₂ (t), ..., T _N (t) are weighted, but the temperature differences T _d1 (t), T _d2 (t), ..., T _dK (t ) May be weighted. Thereby, it is possible to more appropriately reduce the thermal stress directly caused by the temperature difference, and to more appropriately prevent the display screen 50 from being damaged. FIG. 17 is a block diagram showing one example.

The determining unit 11 shown in FIG. 17 is characteristically different from the determining unit 11 of the sixth embodiment in that a weighting unit 42 is provided. That is, the temperature differences T _d1 (t), T _d2 (t),..., T _dK (t) calculated by the temperature difference calculation unit 25 may be directly input to the maximum value calculation unit 22. Instead, it is input to the weighting unit 42 first. Weight adding unit 42
Is the position occupied in the display screen 50 for each of the temperature differences T _d1 (t), T _d2 (t),..., T _dK (t). Weighting factors w ₁ , w ₂ ,.
.., w _K are multiplied respectively.

Regarding the values of the weighting factors w ₁ , w ₂ ,..., W _K , for example, the weighting factor of a pair of blocks located around the display screen 50 is set to the value “1”, and The closer the pair is to the center, the lower the value of the corresponding weighting factor is set. The maximum value calculating unit 22 includes the weighted predicted temperature difference w ₁ T _d1 (t), w calculated by the weight adding unit 42.
₂ T _d2 (t),..., W _K T _dK (t) are input. Therefore, the maximum value calculation unit 22 calculates the weighted predicted temperature difference w ₁ T
_{d1 (t), w 2 T} d2 (t), ···, the maximum value of w _K T _dK (t) Tdwmax
Is calculated. Further, in the comparing unit 23, instead of the maximum value Tdmax, the maximum value Tdwmax is, for example, the reference temperature T1,.
., T6. Subsequent operations are the same as in the sixth embodiment.

Thus, the temperature differences T _d1 (t), T _d2 (t),.
_.. , T _dK (t) is weighted reflecting the contribution of the temperature difference to the thermal stress, and then the luminance is controlled. Therefore, the thermal stress generated on the display screen 50 is reduced. Appropriately mitigated. That is, unnecessary reduction of the luminance of the image displayed on the display screen 50 is more effectively suppressed, and it is possible to prevent the display screen 50 from being damaged while maintaining a high image quality.

<8. Eighth Embodiment> In a display device that generates heat on the display screen 50, for example, a plasma display device, if the same image is continuously displayed for a long time, the phosphor portion included in the display screen 50 is reduced. It is known that "burn-in" sometimes occurs. Here, a device configured to prevent this “burn-in” will be described.

The judgment section 11 shown in the block diagram of FIG.
Is characteristically different from the determination unit 11 of the first to fifth embodiments in that the determination unit 11 includes a still image determination unit 43, an average value storage unit 44, and a selection unit 45. The selection unit 45 belongs to the correction control unit 72 and is interposed between the comparison unit 23 and the correction coefficient calculation unit 24. The average values S ₁ (t−1), S ₂ (t−1),..., S _N (t−1) read from the register unit 9 are input to the predicted temperature calculation unit 21 and It is also input to the still image determination unit 43 at the same time. An average value storage unit 44 is connected to the still image determination unit 43, and the still image determination unit 43 receives the input average values S ₁ (t-1), S ₂ (t-1),. S _N (t−1) is written to the average value storage unit 44.

The still image judging section 43 simultaneously outputs the average value S ₁ (t−t) written in the average value storage section 44 one frame before.
2), S ₂ (t−2),..., S _N (t−2) are read from the average value storage unit 44. The still image determination unit 43 further calculates the average value S
₁ (t-1), S ₂ (t-1), ..., S _N (t-1) and average value S ₁ (t-2),
S ₂ (t−2),..., S _N (t−2) are compared for each same block. Then, when the difference between the average values of the compared blocks is equal to or smaller than a predetermined reference value, the still image determination unit 43 determines that the image of the block is a still image. When it is determined that all the blocks BK _{1 to} BK _N of the display screen 50 are still images for a predetermined period or more, the still image determination unit 43 outputs a predetermined determination signal. The determination signal is sent to the selection unit 45.

Upon receiving the predetermined judgment signal, the selecting section 45 sets the target value C (t) to be higher than the standard value "1" regardless of the value of the target value C (t) output from the comparing section 23. Set it to a lower specific value, for example the value "0.7". At this time, the correction coefficient calculation unit 24 causes the luminance correction coefficient B (t) to follow the specific value set by the selection unit 45 as a target value. Still image determination unit 4
3 does not transmit the predetermined determination signal, the selection unit 4
5 transmits the target value C (t) output from the comparison unit 23 to the correction coefficient calculation unit 24 as it is.

As described above, when the same still image is displayed on the display screen 50 for a long time, the brightness is forcibly reduced, so that "burn-in" of the phosphor can be prevented.

<9. Ninth Embodiment> In the first to eighth embodiments, all the blocks BK _{1 to} BK _N are provided for each frame.
Mean value _{S 1 (t), S 2} (t), ···, S N (t) is calculated about. However, the image signal input through the input terminal 1 (FIG. 1) usually has a strong correlation in the time direction, and the same scene is often displayed over many frames. Therefore, the average values S ₁ (t), S _{1
Even if 2} (t),..., S _N (t) are calculated, the configuration of the device can be simplified without greatly deteriorating the accuracy of luminance control. Here, an example will be described.

The judgment section 11 shown in the block diagram of FIG.
Is characteristically different from the determination unit 11 of the first to fifth embodiments in the internal configuration of the predicted temperature calculation unit 21 and the maximum value calculation unit 46. That is, the predicted temperature calculation unit 21
Instead of reading out all of the average values S ₁ (t-1), S ₂ (t-1),..., S _N (t-1) from the register unit 9 (FIG. 3) for each frame. , And reads only the average value S _n (t−1) corresponding to one block BK _n according to a certain order.

The predicted temperature calculator 21 calculates the read average value S _n (t−1) and the predicted temperature T _n (t) for the same block BK _n N frames before stored in the predicted temperature storage 20.
-N), the predicted temperature T _n (t) for the same block BK _n is calculated. The calculation of the predicted temperature T _n (t) is performed according to the following Expression 3 according to Expression 2.

[0115] _{T n (t) = K1 ×} [S n (t-1) + α] + (1-K2) × T n (tN) ···· predicted temperature T _n (t of (Equation 3) is calculated ) Is written to the predicted temperature storage unit 20. The written predicted temperature T _n (t) is read by the predicted temperature calculation unit 21 after N frames.

The predicted temperature T _n (t) calculated by the predicted temperature calculator 21 is input to the maximum value calculator 46. The maximum value calculation unit 46 calculates the predicted temperature T output from the predicted temperature calculation unit 21.
_In addition to receiving _n (t), the predicted temperature T _n (t)
The N-1 predicted temperatures calculated N frames before and stored in the predicted temperature storage unit 20 are read. The maximum value calculator 46 calculates the N predicted temperatures, for example, the predicted temperature T
₁ (t−n + 1),..., T ₂ (tN), T ₂ (t),..., T _N (tn) Output as Tmax.

The comparing section 23 determines the target value C (t) by comparing the maximum value Tmax output from the maximum value calculating section 46 with, for example, the reference temperatures T1,. The unit 24 calculates the luminance correction coefficient B (t) so as to follow the target value C (t). Subsequent operations are described in Embodiments 1 to
Equivalent to 5.

Also, the average value calculation unit 8 (FIG. 3) located in the preceding stage of the judgment unit 11 also calculates all the average values S ₁ (t), S ₁ for each frame based on the corrected luminance signal A (t). ₂ (t),
.., S _N (t) does not need to be calculated, and only an average value S _{n + 1} (t) corresponding to one block, for example, block BK _{n + 1} , is determined for each frame in a certain order. It is enough to calculate The calculated average value _{Sn + 1} (t) is stored in the register unit 9. Then, the predicted temperature calculation unit 21
The average value S _n (t−1) stored one frame before is read.

Therefore, as compared with Embodiments 1 to 5,
The storage capacity of the register unit 9 can be reduced, and the circuit scale of the average value calculation unit 8 and the predicted temperature calculation unit 21 can be reduced. Note that FIG. 19 shows an example in which the maximum value of the predicted temperature is calculated.
8, a mode for calculating the maximum value of the difference between the predicted temperatures,
It is also possible to adopt a form in which weights are added or a form in which a still image is determined.

<10. Tenth Embodiment> First to Ninth Embodiments
Has shown an example in which the correction of the luminance is uniformly performed over the entire display screen 50. However, in general, it is also possible to individually correct the luminance for each of the blocks BK _{1 to} BK _N. In particular, since the stress is more likely to be generated in the peripheral portion than in the central portion of the display screen 50, if the luminance can be controlled so that the peripheral portion is darker than the central portion of the display screen 50. For example, it is possible to prevent the display screen 50 from being damaged while maintaining better image quality without significantly lowering the luminance of the central portion, which is relatively conspicuous visually. Here, an example will be described.

In the display device shown in the block diagram of FIG. 20, the luminance correction section 61 corrects the luminance for each of the blocks BK _{1 to} BK _N , and the temperature prediction control section 3
Brightness correction coefficient B for each of blocks BK _{1 to} BK _N
1 (t), ···, in that to calculate the B _N (t), the device first to ninth embodiments, are characteristically different. The luminance correction unit 61 provided in the display controller unit 2 divides the display screen 50 into blocks BK _{1 to} BK _N for the sake of idea, similarly to the average value calculation unit 8 provided in the temperature prediction control unit 3.

Then, the luminance correction section 61 outputs the luminance signal P
(t) are divided into luminance signals P ₁ (t),..., P _N (t) respectively corresponding to the blocks BK _{1 to} BK _N , and the luminance signal P
₁ (t), ···, against P _N (t), the luminance correction coefficient B ₁ sent from the temperature prediction control unit 3 (t), ···, B N a (t), by multiplying each , the corrected luminance signal a ₁ respectively corresponding to the blocks BK ₁ ~BK _N (t), obtained · · ·, a _N and (t). That is, for any n (1 ≦ n ≦ N), A _n (t) = B
The corrected luminance signal A _n (t) of the block BK _n is calculated as _n (t) × P _n (t).

The calculated corrected luminance signals A ₁ (t),..., A _N
(t) is input to the data conversion unit 62 and the temperature prediction control unit 3. The data conversion unit 62 shown in FIG.
Works the same as. Therefore, the display screen 50 of the display unit 4 displays, for each of the blocks BK _{1 to} BK _N ,
An image for which the luminance has been individually corrected will be displayed.

FIG. 21 is a block diagram showing the internal configuration of the temperature prediction control unit 3. The temperature prediction control unit 3 is characteristically different from the determination unit 11 of the first to ninth embodiments in that the correction weighting unit 63 is interposed between the determination unit 11 and the output terminal 12. I have. That is, the average value calculation unit 8
Receives the corrected luminance signals A ₁ (t),..., A _N (t),
Based on these signals, the average values S ₁ (t), S ₂ (t),... In the same manner as the average value calculation unit 8 of the first embodiment (FIG. 3).
• Calculate S _N (t). Register unit 9 and judgment unit 11
Is the same as that of the first embodiment, for example.

The luminance correction coefficient B (t) calculated by the judgment unit 11
Is not directly output to the output terminal 12 but is input to the correction weighting unit 63. In the correction weighting unit 63, the luminance correction coefficient B output from decision section 11 (t), for each respective block BK ₁ ~BK _N, weights are added. The weight coefficient is, for example, a value “
Is set to 1 ", closer to the peripheral portion is set to a smaller value. Thus, the luminance correction coefficient B ₁ respectively corresponding to the blocks _{BK 1 ~BK N (t),} ···, B N (t The calculated brightness correction coefficients B ₁ (t),..., B _N (t)
Is transmitted to the luminance correction unit 61 through the output terminal 12.

<11. Eleventh Embodiment> Some plasma display devices control the luminance of the display screen 50 by changing the density of sustain discharge pulses (the number of pulses in one frame period) ( A device of a "sustain discharge pulse control type" is known. Embodiments 1 to 3 of this type of plasma display device
In addition to 10, it is also possible to implement a form as shown in the block diagram of FIG.

In the apparatus shown in FIG. 22, the display controller 2 has a drive signal generator 81 in addition to the data converter 62. The drive signal generator 81 includes a sustain discharge pulse number controller 84. Is provided. The sustain discharge pulse number control unit 84 corresponds to the luminance correction unit 61.
The data conversion unit 62 converts the image signal including the luminance signal P (t) into data, and converts the converted signal including the converted luminance signal P ^* (t) into
The signal is sent to the display unit 4 through the wiring 82.

The drive signal generation section 81 itself includes a display controller section of the plasma display device.
This is a device portion that is always provided, and supplies a drive signal S for generating various types of pulses to the display unit 4 through the wiring 83. In the sustain discharge pulse control type plasma display device, the sustain discharge pulse number control unit 84 controls the number of sustain discharge pulses in one frame period, thereby realizing control of the luminance of the entire display screen 50. .

That is, sustain discharge pulse number control section 84
However, when the control is performed so as to reduce the number of sustain discharge pulses during one frame period, the luminance of the entire display screen 50 is reduced (the entire screen is dark). Conversely, when the control is performed to increase the luminance, the entire display screen 50 is controlled. The brightness becomes higher (the whole screen becomes brighter). Generally, an image is displayed on the display screen 50 with a brightness proportional to the number of sustain discharge pulses in one frame.

The display device of FIG. 22 is configured to effectively use the function of the sustain discharge pulse number control section 84. That is, the luminance signal P (t) input through the input terminal 1 is directly input to the data conversion unit 62 and the temperature prediction control unit 3 without being subjected to correction based on the luminance correction coefficient B (t).

The corrected luminance signal A (t) is supplied to the temperature prediction controller 3.
However, since the luminance signal P (t) is input as the received signal instead of the luminance signal P (t), the average value calculation unit 8 (FIG. 3) provided in the temperature prediction control unit 3 has the luminance not corrected by the luminance correction coefficient B (t). Blocks BK _{1 to} BK _{N of the} signal P (t) itself
As the average value of each average value _{S 1 (t), S 2} (t), ···, S N
(t) is calculated. Therefore, the average values S ₁ (t−1), S 1 read from the register unit 9 and input to the determination unit 11
₂ (t-1),..., S _N (t-1) are also the luminance signal P of the previous frame.
is the average value of each block BK ₁ ~BK _N of (t-1).

FIG. 23 is a block diagram showing the internal configuration of the judgment section 11 of FIG. This judging unit 11 is different in that the luminance correction coefficient B (t) output from the correction coefficient calculating unit 24 is fed back to the predicted temperature calculating unit 21.
It is characteristically different from the determination unit 11 of FIG. The brightness correction coefficient B (t) is delayed by one frame period by the delay unit 71 and is input to the predicted temperature calculation unit 21. The delay unit 71 has, for example, the same configuration as the register unit 9.

The predicted temperature calculating section 21 calculates the average value S ₁ (t-1), S ₂ (t-1),..., S _N (t-1) and the luminance correction coefficient of the previous frame. B (t-1), and the predicted temperatures T ₁ (t-1), T ₂ (t-1),..., T _N (t-
Based on 1), the predicted temperature T
₁ (t), T ₂ (t),..., T _N (t) are calculated.

[0134] _{T n (t) = K1 ×} [B (t-1) × S n (t-1) + α] + (1-K2) × T n (t-1) ·· ( Equation 4) Therefore, B (t−1) × S _n (t−1) is the same value as the average value S _n (t−1) input to the predicted temperature calculation unit 21 in FIG. In other words, the predicted temperatures T ₁ (t), T ₂ (t),..., T _N (t) calculated according to Equation 4 are the predicted temperatures T _N (t) calculated by the predicted temperature calculation unit 21 in FIG. ₁ (t), T ₂ (t), ...
, T _N (t).

Predicted temperature T calculated according to equation (4)
₁ (t), T ₂ (t),..., T _N (t) are written to the predicted temperature storage unit 20 and simultaneously input to the maximum value calculation unit 22. Therefore, if the luminance signals P (t) are the same, the value of the luminance correction coefficient B (t) output from the correction coefficient calculation unit 24 is equal to the luminance correction coefficient B (T) output from the correction coefficient calculation unit 24 in FIG. It is the same as the value of (t).

Returning to FIG. 22, the brightness correction coefficient B (t) calculated by the temperature prediction control section 3 is input to the sustain discharge pulse number control section 84. Sustain discharge pulse number controller 8
4, when the density of the sustain discharge pulse when the luminance correction is not performed is M, the density of the sustain discharge pulse is B (t) × M,
Is controlled so that Therefore, an image having a brightness proportional to B (t) × M is displayed on the display screen 50.
That is, the density of the sustain discharge pulse is controlled so as to realize the luminance corresponding to the corrected luminance signal A (t) = B (t) × P (t). Thus, the display device of FIG. 22 effectively uses the function of the sustain discharge pulse number control unit 84.

<12. Modifications> (1) In the first to eleventh embodiments, the luminance signal P (t) is extracted from the image signal input through the input terminal 1, and based on this, or based on this, The example of calculating the predicted temperatures T ₁ (t), T ₂ (t),..., T _N (t) after correcting the luminance has been described. However, the signal on which the predicted temperature is calculated is generally not limited to the luminance signal P (t).

For example, when an image signal of the RGB color system is input through the input terminal 1, the average value of the R, G, and B components of the image signal is calculated, and the average value is used for each of the above embodiments. Can be handled in the same manner as the luminance signal P (t) in the form (1). At this time, a simple average value of each component can be used, but a weighted average value obtained by adding a weight corresponding to the degree of contribution of each component to heat generation is used as the luminance signal P (t). The calculation of the predicted temperature can be performed with higher accuracy.

That is, in general, by treating a signal reflecting the luminance of an image in the same manner as the luminance signal P (t), it is possible to obtain the same effect as in each embodiment. Therefore, in the present invention, the luminance of the image signal is represented by the luminance signal P (t) as a representative example, but is not limited to this, and includes general signals reflecting the luminance described above.

(2) In Embodiments 1 to 11, mainly
Although the example in which the display device is a plasma display device has been described, the present invention is not limited to the plasma display device, and is applicable to all display devices in which a temperature rise according to the brightness of an image occurs on a display screen. It is possible.

(3) The control of the luminance may be performed by controlling the amplitude of the image signal, ie, the contrast, or by controlling the offset value of the image signal, ie, the brightness. You may.

(4) In the first to eleventh embodiments, the average value calculator 8 calculates the average values S ₁ (t) and S ₂ of the corrected luminance signal A (t) for each of the blocks BK _{1 to} BK _N. (t), ..., S _N (t)
Was calculated, but this average value is not limited to a simple average value, and may be a weighted average value. For example, for an arbitrary block BK _n (n = 1 to N), the luminance signal P (t) at the center of the block BK _n is weighted by 1.2 times and the luminance signal P (t) at the peripheral part by 0.8 times. For example, different weights are added between the central part and the peripheral part to add the average value S
_n (t) may be calculated.

(5) In the first to eleventh embodiments, the example in which the reference temperature storage unit 10 is provided outside the determination unit 11 has been described, but the reference temperature storage unit 10 may be provided in the determination unit 11.

(6) In Embodiments 1 to 11, display screen 5
The number of blocks BK _{1 to} BK _N obtained by dividing 0 is 12
Although the example in which the number is 18 or 18 is shown, it is generally possible to perform the division so as to be more or less.

(7) The above embodiments can be implemented in appropriate combinations. Some of the possible combinations are mentioned in the description of each embodiment, but the possible combinations are not limited to them.

[0146]

According to the display apparatus according to the embodiments of the Invention claims 1 18, to set a plurality of regions on the display panel, the average value of the image signal within each region for each region, based on the average value Thus, the brightness of the image displayed on the display panel is controlled, so that damage to the display panel due to a rise in temperature can be prevented. In addition, since the brightness of the image displayed on the display panel is controlled based on the average value of the image signals in the area, the image signal in each area is reflected in the brightness control. It is possible to prevent a decrease in image quality due to a need to lower the luminance.

According to the display device of the fifth aspect , the setting of the plurality of regions of the display panel includes the setting performed so that each region has a portion overlapping each other. Locally high luminance is likely to be correctly reflected in the maximum value, such as when an image with excessively high luminance is displayed in a corresponding portion. For this reason, breakage of the display panel due to a local temperature rise is more appropriately prevented.

According to the display device of the sixth aspect , the control of the luminance is performed by controlling the flatness of the image signal in each area.
Since the determination is performed based on the maximum value among the average values, damage to the display panel due to a local temperature rise can be more effectively prevented.

Further, according to the display device of the seventh aspect , the control of the luminance is performed by controlling the flatness of the image signal in each area.
When the maximum value among the average values exceeds a predetermined reference value, control for lowering the luminance is included, so that the luminance correction can be realized with a simple configuration.

[0150] Further, according to the display apparatus according to claim 8, the predetermined reference value includes a plurality of reference values, one of the largest value is a plurality of reference values of the average value of the image signal within each area Depending on whether it has exceeded, since the luminance reduction rate in the control for lowering the luminance is changed, the luminance can be corrected in many stages, and the luminance correction is performed more delicately, so the luminance is unnecessarily reduced, or Without raising, it is possible to prevent the display screen from being damaged due to a rise in temperature while maintaining a high image quality.

According to the display device of the ninth aspect , the control of the luminance is performed based on the maximum value of the difference between the average values of the image signals in the areas adjacent to each other. Thermal stress generated on the screen is more appropriately alleviated. Therefore, it is possible to prevent the display screen from being damaged while suppressing unnecessary reduction in the brightness of the image displayed on the display screen.

According to the display device of the tenth aspect , the control of the luminance is performed when the difference between the average value of the image signal before the predetermined time and the average value of the current image signal is equal to or smaller than the predetermined value. Includes control to lower the brightness,
It is possible to detect a still image that continues for a certain period or more, and to prevent "burn-in" on the display screen due to the same still image being displayed on the display panel for a long time.

[0153] Further, according to the display apparatus according to claim 11, calculating the average value of the image signal, for each of displaying an image of one frame, is performed for one area, large degradation of the accuracy of the control of the brightness Without doing so, the configuration of the device can be simplified.

According to the display device of the thirteenth aspect , the control of the luminance is performed by increasing the rate of decrease in the luminance in the peripheral part of the display panel than in the central part.
The degree of correction is set higher in the peripheral portion of the display panel where stress is easily generated and the change in luminance is relatively inconspicuous visually, so that better image quality can be maintained.
It is possible to prevent the display panel from being damaged.

Further, according to the display device of the fifteenth aspect , the first power source for supplying power to the display device and the circuit independent of the first power source are provided, and the power supply by the first power source is performed. And the second power supply for supplying power for calculating the average value of the image signal for each area in the control unit even when the power supply is stopped. Even when the power is turned on again, the average value can be calculated accurately without underestimating the average value , and accurate luminance control can be realized.

According to the display device of the sixteenth aspect , a capacitor for storing a part of the supplied electric power as electric energy, a timer for measuring an elapsed time from the time when the power is turned off, and a nonvolatile memory When the power supply is cut off, the average value of the image signal for each area is calculated using the electric energy stored in the capacitor, and the result is stored in the nonvolatile memory. When turned on, stored in non-volatile memory
The average of the image signal for each region by using the value of the average value and the timer
Since the value is calculated, even when the power is turned off and thereafter the power is turned on again, the average value of the image signal can be calculated accurately without underestimating the average value ,
Accurate luminance control can be realized.

[0157]

[0158]

[0159]

[0160]

[0161]

[Brief description of the drawings]

FIG. 1 is a block diagram of an apparatus according to a first embodiment.

FIG. 2 is a block diagram of a display controller of FIG. 1;

FIG. 3 is a block diagram of a temperature prediction control unit of FIG. 1;

FIG. 4 is an explanatory diagram of the operation of the device of FIG. 1;

FIG. 5 is a block diagram of a determination unit in FIG. 3;

FIG. 6 is an explanatory diagram of the operation of the device of FIG. 1;

FIG. 7 is an explanatory diagram of the operation of the determination unit in FIG. 5;

FIG. 8 is an operation explanatory diagram of the device of FIG. 1;

FIG. 9 is a block diagram of an apparatus according to a second embodiment.

FIG. 10 is an explanatory diagram of the operation of the determination unit 11 of FIG. 9;

FIG. 11 is an explanatory diagram of the operation of the device according to the third embodiment.

FIG. 12 is a block diagram of an apparatus according to a fourth embodiment.

FIG. 13 is a block diagram of an apparatus according to a fifth embodiment.

FIG. 14 is an explanatory diagram of the operation of the predicted temperature calculation unit in FIG. 13;

FIG. 15 is a block diagram of a determining unit according to the sixth embodiment.

FIG. 16 is a block diagram of a determination unit according to the seventh embodiment.

FIG. 17 is a block diagram of another example of the determining unit according to the seventh embodiment.

FIG. 18 is a block diagram of a determining unit according to the eighth embodiment.

FIG. 19 is a block diagram of a judgment unit according to the ninth embodiment.

FIG. 20 is a block diagram of an apparatus according to a tenth embodiment.

FIG. 21 is a block diagram of a temperature prediction control unit of FIG. 20;

FIG. 22 is a block diagram of an apparatus according to an eleventh embodiment.

FIG. 23 is a block diagram of a judgment unit provided in the apparatus of FIG. 22;

FIG. 24 is a block diagram of a conventional device.

FIG. 25 is an explanatory diagram of the operation of the device in FIG. 24.

[Explanation of symbols]

8 average value calculation unit, 13 timer unit with battery, 14 nonvolatile memory unit, 21 predicted temperature calculation unit, 22, 46 maximum value calculation unit, 23 comparison unit, 24 correction coefficient calculation unit (buffer unit), 25 temperature difference calculation Unit, 30 power supply unit, 31 main power supply, 32 sub-power supply, 34 capacitor, 41, 42 weighting unit, 50 display screen, 61 brightness correction unit, 72
Correction control unit, 73 predicted temperature calculation unit, 84 sustain discharge pulse number control unit, BK _{1 to} BK _N blocks, S ₁ (t), S
₂ (t),..., S _N (t) average, T ₁ (t), T ₂ (t),.
_N (t) Predicted temperature.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G09G 3/28 G09G 3/20

Claims (18)

(57) [Claims] A display unit having a single display panel for displaying an image based on 1. A picture signal, in a display device and a control means for controlling the operation of the display unit, wherein the control means is input Based on luminance correction coefficient
To generate a corrected image signal.
By outputting a signal to the display unit,
Brightness correction to control the brightness of the image displayed on the display panel
And a plurality of areas are set on the display panel and the display panel.
Calculate the average value of the corrected image signal in each area
And generate a new brightness correction coefficient based on this average value
Temperature for outputting a new luminance correction coefficient to the luminance correction unit.
And a degree prediction controller, auxiliary for newly input image signal to the luminance correction unit
A display device, wherein the correction is performed based on a newly generated luminance correction coefficient . 2. A new luminance compensation by the temperature prediction control unit.
The generation of the positive coefficient is complemented based on this new luminance correction coefficient.
1 more than the frame of the newly input image signal to be corrected
What is done using the corrected image signal before the frame
The display device according to claim 1, wherein: 3. The display device according to claim 1, wherein the control of the luminance is performed by changing a density of a driving pulse input to the display unit by the control unit. . 4. The setting of a plurality of areas of the display panel includes:
The display device according to any one of claims 1 to 3 , wherein the display is performed so that the areas do not overlap with each other. 5. A plurality of area setting of the display panel, have <br/> of including setting the respective areas is performed so as to have portions that overlap each other from claim 1, wherein up to 3 A display device according to any of the preceding claims. Wherein control of the brightness, the display device according to claim 1, characterized in that it is performed based on the maximum value among the average values of the image signal in each region to 5. 7. The luminance control according to claim 1, wherein the control includes lowering the luminance when the maximum value among the average values of the image signals in each area exceeds a predetermined reference value. 6. The display device according to any one of 1 to 5 . 8. The predetermined reference value includes a plurality of reference values, and the luminance is reduced depending on which of the plurality of reference values has a maximum value among average values of image signals in each area. The display device according to claim 7 , wherein a rate of decrease in luminance in the control is changed. 9. Control of the brightness display according to any one of up to claims 1-5, characterized in that it is performed based on the maximum value of the difference between the mean values of the image signal in the areas adjacent to each other apparatus. 10. Control of the brightness average value of a predetermined time before the image signal for each region and the average value of the current image signal
The difference between the in the case of less than the predetermined value, the display device according to claim 1, characterized in that it comprises a control for reducing the luminance to 9. 11. Calculation of the average value of the image signal, a frame image for each of displaying a display apparatus according to any one of doing the one region from claim 1, wherein up to 10. 12. The control of the brightness, the display device according to any one of claims 1 to 11, characterized by being performed by varying the overall brightness of the display panel. 13. Control of the brightness display according to any one of claims 1 to 12, characterized by being performed by increasing the reduction rate of the luminance in the peripheral portion than the central portion of the display panel apparatus. 14. The control of the brightness, the display device according to claim 1, characterized in that it is carried out with a reduction rate of the different luminance for each area of the display panel to 11. 15. A power supply for supplying power to the display device, comprising: a first power supply for supplying power to the display device; and a circuit independent of the first power supply, wherein power supply by the first power supply is stopped. The display according to any one of claims 1 to 14 , further comprising a second power supply for supplying power for calculating an average value of the image signal for each area in the control means. apparatus. 16. A capacitor for storing a part of electric power supplied to the display device as electric energy, a timer for measuring an elapsed time from a time point when the power supply of the display device is cut off, and a nonvolatile memory. When the power of the display device is cut off, the average value of the image signal for each area is calculated using the electric energy stored in the capacitor, and the result is stored in the nonvolatile memory. Thereafter, when the display device is powered on, the average value of the image signal for each area is calculated using the average value stored in the nonvolatile memory and the value of the timer. display device according to any one of claims 1 to 15. 17. A brightness correction section by the temperature prediction control section.
Number generation based on the average value of the corrected image signal.
Display device according to any one of claims 1 to 16, characterized in that is carried out using a predicted temperature of each of the regions. The predicted temperature of 18. each of the areas are to claim 17, characterized in that is calculated based on the predicted heat radiation amount in the prediction calorific value and each region in each region based on the average value of the image signal The display device according to any one of the preceding claims.