JP4923447B2 - Image signal control device, electro-optical device, electronic apparatus having the same, and display method - Google Patents

Description

The present invention relates to an image signal control device, an electro-optical device, an electronic apparatus having the same, and a display method, and in particular, a CRT, a plasma display panel (hereinafter referred to as PDP) or an organic EL.
The present invention is useful when applied to a case where a burn-in problem occurs with the display of a still image on a display or the like.

In a display device such as a CRT, PDP, or organic EL display, a burn-in problem occurs when a still image or the like is displayed. For example, an organic light emitting diode element (OLED
(Organic Light Emitting Diode) element. In organic EL displays that are arranged in a matrix, the deterioration rate of each OLED element differs when a still image is displayed, so the difference in deterioration between the OLED elements becomes apparent as a burn-in phenomenon. To do.

In order to reduce this burn-in, a technique has been proposed in which the display luminance is reduced at a speed at which a change in human vision is not known while a still image is displayed (see Patent Document 1).

JP 2001-306026 A

As described above, the method of reducing the display brightness while displaying a still image has the effect of suppressing burn-in, but the contrast of the image is reduced due to the reduction of the display brightness. As a result, a new problem of lowering display quality occurs.

In view of the above prior art, the present invention prevents image burn-in by reducing display brightness, and at the same time, eliminates the influence of contrast reduction due to reduction in display brightness and can ensure good display quality. It is an object of the present invention to provide an electro-optical device, an electronic apparatus including the same, and a display method.

In order to solve the above problems, in the present invention, the display luminance is lowered and the gamma characteristic of the image is changed at the same time in order to prevent burn-in. As the gamma characteristic, a value of γ = 2.2 is usually used, and this is changed according to the image. As a result, as shown in FIG. 1, when the average gradation value of a still image is high, increasing the gamma value improves the contrast on the high gradation side and improves the visibility. On the other hand, when the average gradation value is low, if the gamma value is lowered, the contrast on the low gradation side is improved and the visibility is improved.

In this way, contrast reduction due to luminance reduction is complemented by changes in gamma characteristics to prevent display quality degradation.

1) Therefore, the image signal control apparatus according to the first aspect of the present invention includes an image determination unit that determines whether a display image displayed on the display unit is a still image or a moving image based on the image signal; A mode selection unit that selects a still image mode when the image determination unit detects that it is a still image, and a peak luminance of the display image is reduced when the mode selection unit selects a still image mode. a peak brightness setting means for controlling so as to, when said mode selecting means selects the still image mode, the case where the average gray scale value of the image signal representing a still image is higher than the reference average gradation value, As the average gradation value increases, the gamma value of the image signal is increased as compared with a moving image, and when the average gradation value is lower than the reference average gradation value , the average gradation value is decreased. With the above And wherein the Turkey of having a gamma characteristic setting means for reducing than a gamma value of the moving image.
According to this aspect, it is possible to reduce the burn-in that occurs in the still image display mode, and at the same time, while maintaining the contrast of the display image by changing the gamma characteristic while reducing the peak luminance, the display quality is improved. Reduction can be prevented.
In addition, in an image with a high average luminance, the peak luminance is lowered and the gamma value is also increased, so that an effect of reducing power consumption can be expected and an effect of extending the life can be expected.

2) An image signal control device according to the second aspect of the present invention provides:
In the first aspect,
The image determining means determines whether the image is a still image or a moving image in a comparison between the luminance histogram of the image signal of the preceding frame and the luminance histogram of the image signal of the current frame.
According to this aspect, it is possible to easily determine whether or not the image is a still image. As a result,
The effects of the invention according to the first aspect can be obtained satisfactorily.

3) An image signal control apparatus according to the third aspect of the present invention provides:
In the first or second aspect,
The increase / decrease of the gamma value is performed in association with the reduction amount of the peak luminance.
According to this aspect, the gamma value can be most appropriately controlled.

4) An image signal control apparatus according to the fourth aspect of the present invention provides:
In any one of the first to third aspects,
The gamma characteristic setting means sets the gamma value to a predetermined fixed value when the luminance histogram representing the frequency distribution for each gradation of the image signal is flat or does not have a single peak. It is characterized by being.
According to this aspect, even when the luminance histogram is flat or does not have a single peak, an appropriate gamma value can be obtained.

5) An image signal control device according to the fifth aspect of the present invention provides:
In any one of the first to fourth aspects,
The peak luminance is controlled by controlling a light emission duty of a light emitting element forming the display portion.
According to this aspect, the peak luminance can be easily and satisfactorily controlled by controlling the light emission duty of the light emitting element forming the display unit.

6) An electro-optical device according to a sixth aspect of the present invention includes:
The image signal control device according to any one of the first to fifth aspects is provided as an image signal control device that generates an image signal to be supplied to a display unit in which a plurality of light emitting elements are arranged in a matrix. It is characterized by that.
According to this aspect, it is possible to obtain an electro-optical device that can prevent burn-in at the time of displaying a still image and at the same time have good image contrast.

7) An electronic device according to a seventh aspect of the present invention is
The electro-optical device described in the sixth aspect is provided as display means for displaying an image.
According to this aspect, it is possible to obtain an electronic device that prevents burn-in at the time of still image display and at the same time has good image contrast.

8) A display method according to an eighth aspect of the present invention includes:
When a still image is displayed on a display unit in which a plurality of light emitting elements are arranged in a matrix, the peak luminance is reduced and, based on the average luminance of the still image, gamma is used when the average luminance is high. The characteristic value is increased, and when the average luminance is low, the gamma characteristic value is decreased.
According to this aspect, it is possible to reduce the burn-in that occurs in the still image display mode, and at the same time, while maintaining the contrast of the display image by changing the gamma characteristic while reducing the peak luminance, the display quality is improved. Reduction can be prevented.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The description of the present embodiment is an exemplification, and the configuration of the present invention is not limited to the following description.

FIG. 2 is a block diagram showing a schematic configuration of the electro-optical device I according to the embodiment of the present invention.
As shown in the figure, the electro-optical device I includes a pixel region A, a scanning line driving circuit 100, a data line driving circuit 200, a control circuit 300, and a power supply circuit 500. Of these, the pixel area A
, M scanning lines 101 and m light emission control lines 102 are formed in parallel with the X direction, and n data lines 103 are formed in parallel with the Y direction orthogonal to the X direction. A pixel circuit 400 including an OLED element corresponding to each intersection of the scanning line 101 and the data line 103.
Are provided. Each pixel circuit 400 is supplied with a power supply voltage Vdd via a power supply line L.

The scanning line driving circuit 100 scans signals Y1 and Y for sequentially selecting a plurality of scanning lines 101.
2, Y3,..., Ym are generated and the emission control signals Vg1, Vg2, Vg3,.
, Vgm is generated. The scanning signals Y1 to Ym and the light emission control signals Vg1 to Vgm are generated by sequentially transferring the Y transfer start pulse DY in synchronization with the Y clock signal YCLK. The light emission control signals Vg1, Vg2, Vg3,..., Vgm are supplied to the pixel circuits 400 via the light emission control lines 102, respectively.

FIG. 3 shows an example of a timing chart of the scanning signals Y1 to Ym and the light emission control signals Vg1 to Vgm. The scanning signal Y1 is a pulse having a width corresponding to one horizontal scanning period (1H) from the first timing of one vertical scanning period (1F), and is supplied to the scanning line 101 in the first row. Thereafter, the pulses are sequentially shifted and supplied as scanning signals Y2, Y3,..., Ym to the scanning lines 101 in the 2, 3,. In general, when the scanning signal Yi supplied to the scanning line 101 in the i-th row (i is an integer satisfying 1 ≦ i ≦ m) becomes H level, the scanning line 10
1 is selected. Further, the light emission control signals Vg1, Vg2, Vg3,..., Vg
As m, for example, a signal obtained by inverting the logic level of the scanning signals Y1, Y2, Y3,.

The data line driving circuit 200 selects the scanning line 1 selected based on the output gradation data Dout.
Current signals Idata 1, Idata 2 representing the gray level for each of the pixel circuits 400 located at 01,
Idata3, Idata4,..., Idatan are supplied. In other words, in this example, the gradation signal is given as current signals Idata1, Idata2, Idata3, Idata4,..., Idatan indicating gradation luminance, and j (j is an integer satisfying 1 ≦ j ≦ n). Idataj is supplied to the data line of the column.

The control circuit 300 generates various control signals such as a Y clock signal YCLK, an X clock signal XCLK, an X transfer start pulse DX, and a Y transfer start pulse DY, and sends them to the scanning line drive circuit 100 and the data line drive circuit 200. Output. In addition, the control circuit 300 performs image processing such as gamma correction on the input gradation data Din supplied from the outside to output gradation data Dout.
Is generated. The output gradation data Dout is, for example, 8-bit gradation components arranged in a predetermined arrangement.

Next, the pixel circuit 400 will be described. FIG. 4 shows a circuit diagram of the pixel circuit 400. The pixel circuit 400 shown in the figure corresponds to the i-th row and the j-th column, and is supplied with the power supply voltage Vdd. The pixel circuit 400 includes four TFTs 401 to 404, a capacitor element 410, and an OLED.
And an element 420. In the manufacturing process of the TFTs 401 to 404, a polysilicon layer is formed on the glass substrate using laser annealing shot. OLED element 4
No. 20 has a light emitting layer sandwiched between an anode and a cathode. The OLED element 420 is
Light is emitted at a luminance corresponding to the forward current. The light-emitting layer has an organic EL (Electrolum) according to the emission color.
inescence) material is used. In the manufacturing process of the light emitting layer, the organic EL material is ejected as droplets from an inkjet head and dried.

The TFT 401 that is a driving transistor is a p-channel type, and the TFTs 402 to 404 that are switching transistors are an n-channel type. The source electrode of the TFT 401 is connected to the power supply line L, while its drain electrode is connected to the drain electrode of the TFT 403, the drain electrode of the TFT 404, and the source electrode of the TFT 402.

One end of the capacitive element 410 is connected to the source electrode of the TFT 401, while the other end is connected to the T
The gate electrode of FT 401 and the drain electrode of TFT 402 are connected to each other. TFT
A gate electrode 403 is connected to the scanning line 101, and a source electrode thereof is connected to the data line 103. The gate electrode of the TFT 402 is connected to the scanning line 101. On the other hand, TFT
The gate electrode 404 is connected to the light emission control line 102, and its source electrode is the OLED element 42.
Connected to zero anode. A light emission control signal Vgi is supplied to the gate electrode of the TFT 404 via the light emission control line 102. Note that the cathode of the OLED element 420 is a common electrode for all of the pixel circuits 400 and is at the GND potential in the power supply.

In such a configuration, when the scanning signal Yi becomes H level, the n-channel TFT 40
Since 2 is turned on, the TFT 401 functions as a diode in which the gate electrode and the drain electrode are connected to each other. When the scanning signal Yi becomes H level, the n-channel TFT
Similarly to the TFT 402, 403 is also turned on. As a result, the current Idata of the data line driving circuit 200 flows through the path of the power supply line L → TFT 401 → TFT 403 → data line 103, and at that time, the charge corresponding to the potential of the gate electrode of the TFT 401 is transferred to the capacitive element 4.
10 is accumulated.

When the scanning signal Yi becomes L level, both the TFTs 403 and 402 are turned off. At this time, since the input impedance of the gate electrode of the TFT 401 is extremely high, the charge accumulation state in the capacitor 410 does not change. The voltage between the gate and source of the TFT 401 is held at the voltage when the current Idataj flows. Further, when the scanning signal Yi becomes L level, the light emission control signal Vgi becomes H level. Therefore, the TFT 404 is turned on and the TFT
An injection current Ioled corresponding to the gate voltage flows between the source and drain of 401. Specifically, this current flows through a path of the power supply line L → TFT 401 → TFT 404 → OLED element 420.

Here, the injection current Ioled flowing through the OLED element 420 is determined by the gate-source voltage of the TFT 401, and this voltage is determined when the current Idataj flows through the data line 103 by the H level scanning signal Yi. Is the voltage held by. For this reason,
When the light emission control signal Vgi becomes H level, the injection current I flowing in the OLED element 420 is
oled substantially coincides with the current Idataj that flows immediately before. Thus, the pixel circuit 400 has the current Id.
Since the emission luminance is defined by ata, this is a circuit of a current program system.

In this embodiment, the input gradation data Din is subjected to image processing such as gamma correction, and output gradation data Do.
The control circuit 300 generates ut.

FIG. 5 is a block diagram showing the control circuit 300 in detail. As shown in the figure
The control circuit 300 includes a display control unit 301 and a luminance / gamma characteristic control unit 302.

The display control unit 301 performs predetermined image processing on input gradation data Din supplied from the outside to form output gradation data Dout, and also includes a Y clock signal YCLK, an X clock signal XCLK, an X transfer start pulse DX, Various control signals such as a Y transfer start pulse DY are generated and output to the scanning line driving circuit 100 and the data line driving circuit 200 (see FIG. 2).

On the other hand, the luminance / gamma characteristic control unit 302 controls the peak luminance control signals S1 and S2 and the gamma characteristic for controlling the optimum peak luminance and gamma value according to the average gradation value in each case of the moving image or the still image. Control signals S 3 and S 4 are formed and supplied to the display control unit 301. Here, the peak luminance control signal S1 and the gamma characteristic control signal S3 are control signals when the display image is a moving image, and the peak luminance control signal S2 and the gamma characteristic control signal S4 are a still image. Control signal.

In order to form the peak luminance control signals S1 and S2 and the gamma characteristic control signals S3 and S4, the luminance / gamma characteristic control unit 302 includes a histogram detection unit 302a and an average gradation value calculation unit 30.
2b, a memory 302c, a histogram comparison unit 302d, a mode selection unit 302e, peak luminance setting units 302f and 302g, and gamma characteristic setting units 302h and 302i.

The histogram detection unit 302a is a predetermined frame (usually one frame) based on the input image signal.
The frequency distribution for each gradation of the input gradation data Din is detected. Average gradation value calculator 302b
Calculates the average value of the frequency distribution detected by the histogram detector 302a. Memory 302c
Stores data for a predetermined frame (usually one frame) related to the frequency distribution detected by the histogram detection unit 302a. The histogram comparison unit 302d compares the frequency distribution of the preceding frame stored in the memory 302c with the frequency distribution captured in real time, and the image signal represented by the input gradation data Din is that of a moving image. Or whether it is a still image. This determination can be made easily by, for example, taking a frequency distribution difference for each gradation in the preceding frame and the current frame, and recognizing a moving image when the difference exceeds a predetermined threshold value and a still image when the difference is less than the threshold value. Can be done.

There are various other methods for determining a moving image and a still image. For example, 1) the input image signal data is compared with each frame, for example, 2) the image signal is determined by Fourier transform, 3) the moving image speed is detected, and 4) the moving image itself is However, there may be one that detects a moving amount or a motion vector of a moving image.

The determination result in the histogram comparison unit 302d is supplied to the mode selection unit 302e. In the mode selection unit 302e, data representing the average gradation value, which is output data of the average gradation value calculation unit 302b, depending on whether the image is a moving image or a still image, is used as peak luminance setting units 302f and 30
Supply to any of 2g. That is, data representing the average gradation value is supplied to the peak luminance setting unit 302f in the case of a moving image and to the peak luminance setting unit 302g in the case of a still image.

The peak luminance setting unit 302f supplies the display control unit 301 with a peak luminance control signal S1 for setting the peak luminance in the case of a moving image according to the supplied average gradation value. Similarly, the peak luminance setting unit 302g supplies the display control unit 301 with a peak luminance control signal S2 for setting the peak luminance in the case of a still image. The gamma characteristic setting unit 302h supplies the display control unit 301 with a gamma characteristic control signal S3 for setting a gamma value in the case of a moving image corresponding to the average gradation value supplied via the peak luminance setting unit 302f. . Similarly, the gamma characteristic setting unit 302i is a gamma characteristic control signal S4 for setting a gamma value for a still image.
Is supplied to the display control unit 301.

In the moving image mode, the display control unit 301 controls the luminance of the pixel region A (see FIG. 2) so that the display peak luminance is adjusted to the moving image based on the peak luminance control signal S1. In this case, the peak luminance can be controlled by applying all conventionally known methods. For example, the light emission duty of the OLED element 420 (see FIG. 4) is controlled, the current Idata (see FIG. 4) is controlled via the output gradation data Dout, and the power supply voltage Vdd (see FIG. 2) is controlled. Etc. are considered.

On the other hand, in the case of the still image mode, control is performed so that the display peak luminance is matched to the still image based on the peak luminance control signal S2. That is, in the case of the still image mode, a peak luminance reduced by a certain amount is set for the moving image mode, and control is performed in the same manner as in the case of the moving image so as to obtain the luminance. As a result, even when the average gradation value of the input gradation data Din is the same, the peak luminance in the case of a still image is relatively reduced compared to the case of a moving image. As a result, burn-in of the pixel area A due to deterioration of the OLED element 420 (see FIG. 4) can be effectively prevented. This is the same as in the prior art.

Further, the display control unit 301 performs control to change the gamma value of the output gradation data Dout based on the gamma characteristic control signal S3 in the moving image mode, and the gamma characteristic control signal S4 in the still image mode. Based on this, control is performed to change the gamma value of the output gradation data Dout. Here, the method for changing the gamma characteristic is not particularly limited, but the LUT (Look U
A method of converting the output gradation data Dout corresponding to the input gradation data Din using p Table) is preferable. In this method, the rules for changing the gamma value are stored in a table in advance. This LUT method is provided in the display control unit 301. Therefore, the gamma characteristic control signals S3 and S4 according to the present embodiment function as a selection signal for selecting a specific table value in the LUT formed for each average gradation value. As described above, in this embodiment, when the still image mode is set, control is performed so as to appropriately change not only the peak luminance but also the gamma value.

FIG. 6 shows the relationship between the average gradation value and the peak luminance. The curve a in the figure shows the relationship between the average gradation value and the peak luminance when the image is a moving image, and the relationship between the average gradation value and the peak luminance when the curve b is a still image. As shown in the figure, the peak luminance is set lower as the average gradation value is larger, and the peak luminance is set lower in the case of a still image than in the case of a moving image.

Therefore, when the still image mode is set, the peak luminance setting unit 302g shown in FIG. 5 uses the average luminance from the peak luminance at a point on the curve a corresponding to the average gradation value calculated by the average gradation value calculation unit 302b. The peak luminance is controlled via the display control unit 301 with the peak luminance control signal S2 so as to gradually shift to the peak luminance at the point on the curve b according to the tone value.

FIG. 7 shows the relationship between the average gradation value and the gamma value. The curve c in the figure shows the relationship between the average gradation value and the gamma value when the image is a moving image, and the relationship between the average gradation value and the gamma value when the curve d is a still image.

8 to 10 are graphs showing the histogram distribution of the input gradation data Din. FIG. 8 shows a case where the histogram distribution is shifted to the low gradation value side, and FIG. 9 shows a histogram distribution on the high gradation value side. FIG. 10 shows a case where the histogram distribution is flat.

In the case of a moving image, when the histogram exists on the low gradation value side as shown in FIG. 8, the gamma value is set lower, and when the histogram exists on the high gradation value side as shown in FIG. Is set to a high value, and when the histogram is flat as shown in FIG. 10 or when the histogram is not a single peak, the gamma value is set to a constant value (for example, 2.2).
That is, as shown in FIGS. 8 and 9, when the peak of the histogram is significantly unevenly distributed on the low gradation value side or the high gradation value side, the average gradation value is used as it is and the gamma value is based on the curve c. If the histogram is flat or if the histogram is not a single peak, a constant gamma value (for example, 2.2) is set regardless of the average gradation value. . Here, in order to detect whether or not the peak of the histogram is significantly unevenly distributed on the low gradation value or high gradation value side, for example, whether or not the peak value of the frequency in the histogram exceeds a predetermined threshold value is determined. What is necessary is just to detect. The case where the peak value exceeds a predetermined threshold value is unevenly distributed, and the case where the peak value is not more than the threshold value is a case where the peak value is not flat or a single peak.

On the other hand, in the case of a still image, in a region where the average gradation value is larger than the reference value e, the gamma value is increased as compared with the case of a moving image as the average gradation value increases, and the average gradation value is the reference value e. In the smaller region, the gamma value is decreased as the average gradation value is decreased than in the case of the moving image.

Therefore, in the gamma characteristic setting unit 302i shown in FIG. 5, a point on the curve c set on the curve c based on the average gradation value calculated by the average gradation value calculation unit 302b (the last gamma value of the moving image is given). The LUT of the display control unit 301 is appropriately selected by the gamma characteristic control signal S4 so as to gradually shift from the gamma value at the point) to the gamma value at the point on the curve d in the average gradation value, and the output gradation data Dout Control the gamma value.

Thus, when a still image is displayed, the gamma characteristic is gradually changed to the value shown by the curve d as the display peak luminance is lowered to maintain the contrast of the video of the display image. The amount of change in the gamma value at this time is set for each average gradation value in association with the peak luminance. As a result, the gamma value can be optimized by associating it with the peak luminance.

The mode of control in the case of a moving image is the same as in the conventional case. However, in the case of a still image, in this embodiment, the peak luminance and gamma value determined by the procedure as described above are used as the peak luminance control signal S2 and gamma characteristic control signal S4. , And supplied to the display control unit 301 every frame. Here, the peak luminance is controlled by, for example, the light emission duty value. The relationship between the light emission duty width and the luminance is linear. This light emission duty width is transmitted as a peak luminance control signal. On the other hand, the gamma value is set by selecting a suitable LUT pattern prepared in advance. Here, if the increase / decrease of the gamma value is set in association with the reduction amount of the peak luminance, the gamma value can be most appropriately controlled.

According to the present embodiment, it is possible to reduce the burn-in that occurs in the still image display mode, while maintaining the contrast of the display image by changing the gamma characteristic while reducing the peak luminance, and the display quality. Can be prevented.

In addition, in an image with a high average gradation value, the peak luminance is lowered and the gamma characteristic is also increased, so that the effect of reducing power consumption can be expected and the effect of extending the life can be expected.

<Application example>
Next, an electronic apparatus to which the electro-optical device I according to the above-described embodiment is applied will be described. FIG. 11 shows a configuration of a mobile personal computer to which the electro-optical device I is applied. The personal computer 2000 includes an electro-optical device I as a display unit and a main body 2010. A main body 2010 includes a power switch 2001 and a keyboard 2002.
Is provided. Since the electro-optical device I uses the OLED element 420, it is possible to display an easy-to-see screen with a wide viewing angle.

FIG. 12 shows a configuration of a mobile phone to which the electro-optical device I is applied. A cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and an electro-optical device I as a display unit. By operating the scroll button 3002, the screen displayed on the electro-optical device I is scrolled.

FIG. 13 shows a portable information terminal (PDA: Personal Digital Assis) to which the electro-optical device I is applied.
tants). The information portable terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and the electro-optical device I as a display unit. Power switch 4
When 002 is operated, various types of information such as an address book and a schedule book are displayed on the electro-optical device I.

Furthermore, field emission element (FED), surface electric emission element (SE
D) and can be suitably applied to a display device using a self-luminous element such as a ballistic electron-emitting device (BSD).

Note that examples of electronic devices to which the electro-optical device I is applied include liquid crystal televisions, car navigation devices, videophones, and the like in addition to those shown in FIGS. The electro-optical device described above can be applied as a display unit of these various electronic devices.

It is a characteristic view for demonstrating the principle of this invention. 1 is a block diagram illustrating an electro-optical device according to an embodiment of the invention. 3 is a timing chart of scanning signals and light emission control signals in FIG. 2. FIG. 3 is a circuit diagram illustrating a pixel circuit in the electro-optical device illustrated in FIG. 2. FIG. 3 is a block diagram showing in detail an extracted control circuit 300 in FIG. 2. It is a graph which shows the relationship between an average gradation value and peak luminance. It is a graph which shows the relationship between an average gradation value and a gamma value. It is a graph (distribution to the low gradation value side) which shows the histogram distribution of an average gradation value. It is a graph (distribution to the high gradation value side) which shows the histogram distribution of an average gradation value. It is a graph (flat distribution) which shows the histogram distribution of an average gradation value. FIG. 14 is a perspective view showing a personal computer to which the electro-optical device is applied. It is a perspective view which shows the structure of the mobile telephone to which the electro-optical device is applied. It is a perspective view which shows the structure of the portable information terminal to which the electro-optical device is applied.

Explanation of symbols

100 scanning line drive circuit, 101 scanning line, 102 light emission control line, 103 data line,
200 data line driving circuit, 300 control circuit, 301 display control unit, 302 gamma characteristic control unit, 302a histogram detection unit, 302b average gradation value calculation unit, 302c memory, 302d histogram comparison unit, 302e mode selection unit, 302f, 302g
Peak luminance setting section, 302h, 302i gamma characteristic setting section, A pixel area, DX transfer start pulse, DY transfer start pulse, Din input gradation data, Dout output gradation data, I electro-optical device, a, b, c, d, curve, e reference value

Claims (7)

Image determination means for determining whether a display image displayed on the display unit based on the image signal is a still image or a moving image;
A mode selection unit that selects a still image mode when the image determination unit detects that the image is a still image;
When the mode selection unit selects the still image mode, a peak luminance setting unit that controls to reduce the peak luminance of the display image;
When said mode selecting means selects the still image mode, the case where the average gray scale value of the image signal representing a still image is higher than the reference average gradation value, the image with an increase in the mean gray level is increased than when the gamma value of the signal of the moving image, than the case where the average gray scale value is lower than the reference average gradation value in the case of a moving image the gamma value with the decrease of the mean gray level an image signal control device comprising a Turkey also having a gamma characteristic setting means for reducing. In claim 1,
The image determining means determines whether the image is a still image or a moving image in a comparison between the luminance histogram of the image signal of the preceding frame and the luminance histogram of the image signal of the current frame. Signal control device. In claim 1 or claim 2,
The image signal control apparatus characterized in that the increase / decrease of the gamma value is performed in association with the reduction amount of the peak luminance. In any one of Claims 1 to 3,
The gamma characteristic setting means sets the gamma value to a predetermined fixed value when the luminance histogram representing the frequency distribution for each gradation of the image signal is flat or does not have a single peak. An image signal control apparatus characterized by the above. In any one of Claim 1 thru | or 4,
The image signal control apparatus according to claim 1, wherein the peak luminance is controlled by controlling a light emission duty of a light emitting element forming the display unit.   6. The image signal control apparatus according to claim 1, wherein the image signal control apparatus generates an image signal to be supplied to a display unit in which a plurality of light emitting elements are arranged in a matrix. An electro-optical device.   An electronic apparatus comprising the electro-optical device according to claim 6 as display means for displaying an image.

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