JP3308234B2 - Display device luminance level control device and luminance level control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a luminance level control device and a luminance level control method for a display device, and more particularly to a method for providing an efficient luminance control method for displaying a moving image. .

[0002]

2. Description of the Related Art In designing a self-luminous display device, for example, a plasma display device, it is important to balance brightness and contrast with power consumption control.

[0003] In order to secure the luminance, it is generally sufficient to increase the control voltage. However, there is a downside that the power consumption of the device increases. for that reason,
It is necessary to increase power consumption to secure brightness,
In order to reduce the power consumption, a contradictory condition is required that the luminance must be reduced.

Therefore, in recent years, there has been a demand for a method of balancing such image quality securing and low power consumption. To meet this demand, for example, there is a method of detecting the average luminance of the display screen and controlling the luminance in accordance with the content of the image.

[0005]

However, the above method has a disadvantage that an unnatural luminance change is noticeable because the luminance level is immediately controlled every time the average luminance of the screen changes.

A main object of the present invention is to ensure the brightness and contrast of a display screen of a display device such as a plasma display and to efficiently control power consumption, and furthermore, the control makes the fluctuation of the brightness on the display screen inconspicuous. It is an object of the present invention to provide a luminance level control device and a luminance level control method for a display device which can be controlled as described above.

[0007]

Luminance level control device for a display device of the present invention According to an aspect of the input video signal scene Cheng
Scene change detection means for detecting image
Average luminance level calculator for determining the average luminance level of an image signal
Step and a scene change by the scene change detecting means.
Is detected based on the average luminance level.
Means for controlling the display brightness level suitable for the display image.
Is what you do.

[0008]

Further, the brightness level control device of the display device of the present invention comprises a scene change detecting means for detecting a scene change of the input video signal, and immediately when a scene change is detected by the scene change detecting means. Means for controlling so as to reach a display luminance level suitable for a display image, and controlling to reach a display luminance level suitable for the display image after a set time if no scene change is detected.

The brightness level control device of the display device according to the present invention includes a scene change detecting means for detecting a scene change of the input video signal, and an average brightness level calculating means for obtaining an average brightness level of the input video signal. When a scene change is detected by the scene change detecting means, control is performed so that a display luminance level suitable for a display image is immediately obtained based on an output from the average luminance level calculating means, and the scene change is detected. If not, control is performed after a set time to reach a display luminance level suitable for a display image based on the output from the average luminance level calculation means.

[0011]

Further, according to the brightness level control method for a display device of the present invention, a scene change of an input video signal is detected,
If the scene change is detected, control is performed so as to immediately reach a display luminance level suitable for the display image. If the scene change is not detected, control is performed so as to reach a display luminance level suitable for the display image after a set time. Is what you do.

Although the present invention can be suitably used for a plasma display, other self-luminous display devices such as EL (Elecrtoluminescence), FED
(Field Emission Display), fluorescent display tubes and the like.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, a plasma display will be described as a display device.

In a preferred embodiment of the present invention, in a display device, a scene (one cut) in which images are continuous is sent to an automatic brightness limiting circuit that adjusts a brightness level that fluctuates according to the content of a displayed image to an appropriate brightness. In the case where the average luminance of the image fluctuates, the luminance level control is not performed, or the luminance level control is performed with a longer luminance change time, and when the average luminance of the image fluctuates during a scene change of the image, A control circuit for controlling the luminance level so that the luminance can be changed immediately is provided.

FIG. 1 is a block diagram showing an apparatus for controlling a luminance level of a plasma display according to the present invention. FIG. 2 is a block diagram of a conventional brightness level control device for a plasma display.

In the conventional brightness level control device shown in FIG. 2, the automatic brightness limiting circuit 3, the average brightness level calculation circuit 4, the brightness level control circuit 5, and the PDP drive controller 6
1, the brightness level control device according to the present invention further includes a scene change detection circuit 1 and a brightness level switching circuit 2.

A video signal converted into a digital signal is input to the scene change detection circuit 1. Then, a video level is detected for the input image data, and a scene change is detected. Then, the detection result is input to the luminance level switching circuit 2. The average luminance level calculation circuit 4 calculates the average luminance level of the input video signal, and inputs the average luminance data signal to the luminance level switching circuit 2.

The luminance level switching circuit 2 outputs the average luminance data signal obtained by the average luminance level calculation circuit 4 at that time when the signal of the scene change detection result is a signal determined to be a scene change. When the signal is determined not to be a scene change, the average luminance data signal obtained by the average luminance level arithmetic circuit 4 at that time is set to be close to the average luminance data signal with a certain time length. , While updating the average luminance data signal. Alternatively, instead of the average luminance data signal obtained by the average luminance level calculation circuit 4, the previous average luminance data signal is continuously output. That is, when there is a scene change, the luminance level is immediately changed, and when no scene change is performed, an operation of slowly changing the luminance level or not changing the luminance level is executed.

Therefore, a sudden change in the brightness level caused by scrolling of an image is eliminated, and when a scene change in which the brightness change is not so noticeable, the brightness level is changed immediately so that an unnatural brightness of the screen is obtained. The effect of eliminating the change and efficiently improving the luminance and the contrast can be obtained.

[0021]

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

FIG. 1 is a block diagram showing a plasma display luminance level control device as one embodiment of the present invention. As shown in FIG. 1, the brightness level control device of the present embodiment includes a scene change detection circuit 1, a brightness level switching circuit 2, an automatic brightness limiting circuit 3, an average brightness level calculation circuit 4,
It has a luminance level control circuit 5 and a PDP drive controller 6.

The scene change detection circuit 1 receives analog / digital converted digital data of a video signal input to the plasma display. The scene change detection circuit 1 detects a video level of an input video signal to detect a scene change. And
The detection result is input to the luminance level switching circuit 2. In addition, the average luminance level calculation circuit 4 calculates the average luminance level of the input video signal, and inputs the optimum average luminance level data signal as a result to the luminance level switching circuit 2.

The luminance level switching circuit 2 outputs the average luminance data signal obtained by the average luminance level calculation circuit 4 when the signal from the scene change detection circuit 1 is a signal that determines that a scene change has occurred. On the other hand, when the signal from the scene change detection circuit 1 is a signal that determines that a scene change has not been performed, the average luminance data signal obtained by the average luminance level calculation circuit 4 is not used, Continue to output the signal. This makes it possible to control the brightness level of the plasma display only when there is a scene change in the input video.

The output from the luminance level switching circuit 2 is input to an automatic luminance limiting circuit 3. The automatic brightness limiting circuit 3 sets the brightness and the video contrast suitable for the video content based on the average brightness data signal obtained as described above.

The output from the automatic brightness limiting circuit 3 is input to a brightness level control circuit 5. The luminance level control circuit 5 receives setting data from the automatic luminance limiting circuit 3 and performs setting for controlling appropriate luminance and contrast in the display module. Then, the data is input to the PDP drive controller 6 as automatic brightness restriction data, and is output as a video having both power consumption, appropriate brightness, and video contrast, and displayed on a display.

Further, in the brightness level switching circuit 2,
When a scene change is not being performed, the data signal is changed so as to approach the average luminance data signal with a certain set time with respect to the average luminance data signal updated from time to time from the average luminance level calculation circuit 4. When output,
Brightness control can be performed even when a scene change is not being performed, and more efficient brightness level control can be performed.

(Description of Operation) The operation of this embodiment will be described below. First, the operation of the scene change detection circuit 1 will be described with reference to FIG.

The scene change detection circuit 1 comprises a frame memory 7, a subtractor 8, a difference data value calculation circuit 9, a difference data value accumulation circuit 10, and a scene change detection unit 11.

The signal input to the scene change detection circuit 1 is input to a frame memory 7 and a subtractor 8, respectively. The signal input to the frame memory 7 is output from the frame memory 7 as a signal delayed by one frame, and input to the subtractor 8. The subtractor 8 calculates a difference between each pixel value of the input original image data and the image data from the frame memory 7. Then, the difference data value calculation circuit 9 averages the values of the pixels included in the predetermined area.
The averaging in the predetermined area is performed on the entire video data. For example, as shown in FIG.
As a 6.times.16 macroblock, averaging of pixel values in the area is performed on the entire video data. Then, the calculation data is output to the difference data value accumulation circuit 10.

The difference data value accumulation circuit 10 receives a plurality of calculation data calculated by the difference data value calculation circuit 9, and accumulates the plurality of calculation data values for each luminance value. Then, the accumulated data value is output to the scene change detection unit 11.

The scene change detecting section 11 detects whether a scene change has occurred between frames by comparing the magnitude of a data value accumulated for each luminance value with a predetermined value. For example, when the luminance value of the accumulated data is larger than a predetermined luminance value, detection information indicating that a scene change has occurred is output.

In the difference data value calculating circuit 9, only a specific pixel data value is extracted instead of averaging the pixel values of a predetermined area, and the difference data value accumulating circuit 10 outputs the specific pixel data value. Is accumulated for each luminance, and the scene change detection unit 11 determines a scene based on this data. Further, if the processing is performed on the color information, the accuracy is improved.

As shown in a specific image, for example, as shown in FIG. 5, in the case of an image (a) in which a person is at the right end and an image (b) in which the camera scrolls to the right, an abrupt change between frames occurs. Since no change in the luminance of the video is detected, it is not determined that a scene change has occurred. At this time, a signal indicating that no signal is detected is output. Also, as shown in FIG. 6, when the video is switched from the video (a) where a person is present to the landscape (b) with trees, a rapid change in luminance between frames is detected.
A scene change is determined. At this time, a signal indicating the detection is output. The scene change detection circuit 1
The circuit is not limited to the circuit configuration shown in the present embodiment, and may be a circuit that can detect a scene change by another method. For example, there is a circuit using a method disclosed in JP-A-10-294923 and JP-A-10-276435. A method for detecting a scene change will be described with reference to an example.
Japanese Patent Application Laid-Open No. 10-276435 discloses a method of detecting a scene change between a first screen and a second screen, determining a color value of the first screen by level, counting each level, and creating a histogram. A maximum point and / or a minimum point (representative point) are obtained, a representative point is similarly obtained for the second screen, and the representative points of the first and second screens are compared. A method for determining a scene change is described.

Next, the operation of the circuits other than the scene change detection circuit 1 will be described. First, the operation of the average luminance level calculation circuit 4 will be described. The signal input to the average luminance level calculation circuit 4 detects the luminance of the entire screen in one frame and creates data in which the luminance levels are averaged. As the luminance of the entire screen, the luminance of each dot is detected. The average luminance level of the entire screen is output to the luminance level switching circuit 2 as an average luminance data signal.

In the brightness level switching circuit 2, when the signal of the detection result from the scene change detection circuit 1 is a signal that has determined that a scene change has occurred, the average brightness data obtained by the average brightness level calculation circuit 4 at that time is obtained. Perform the operation of outputting a signal. When the signal from the scene change detection circuit 1 is a signal that determines that a scene change has not been performed, the signal is not the average luminance data signal obtained by the average luminance level calculation circuit 4 at that time, but is the average value up to that point. An operation of continuously outputting the luminance data signal is performed.

The output from the brightness level switching circuit 2 is then input to the automatic brightness limiting circuit 3. The automatic brightness limiting circuit 3 corresponds to an ABL circuit in a television device. The ABL circuit is a circuit for preventing the high voltage circuit in the picture tube from being overloaded when the luminance becomes abnormally high. Specifically, as shown in FIG. 7, an operation of limiting the average video level (APL) is performed. As indicated by the dotted line, power consumption increases unless the APL is limited. Therefore, assuming an APL characteristic shown by a straight line, a control characteristic shown by a curve can be actually obtained as an example of the characteristic. In the automatic brightness limiting circuit 3 as well,
An operation for controlling the PL is performed.

In the automatic luminance limiting circuit 3, the luminance suitable for the video content is adjusted so as not to overload the PDP module.
And data of image contrast. The set data signal is input to the luminance level control circuit 5. The brightness level control circuit 5 inputs the set data signal to the PDP drive controller 6 as automatic brightness limit data. Then, the PDP drive controller 6 reflects the automatic brightness limit data as the optimum brightness on the display image, outputs the data, and displays the data on the display.

Further, in the above-mentioned brightness level switching circuit 2, when a scene change is not performed, the average brightness data signal updated from time to time by the average brightness level calculation circuit 4 has a certain set time. When a data signal is output so as to approach the average luminance data signal, luminance control can be performed even when a scene change is not performed, and more efficient luminance level control can be performed.

In the above-described method, there is a method in which processing in a frame is performed as processing in a field.

[0041]

As described above, according to the present invention, the luminance control based on the fluctuation of the average luminance in the same scene caused by the scrolling of the video or the like is not performed, or
Efficient brightness level control can be performed by performing brightness level control with a long brightness change time and immediately performing brightness level control when a scene change is performed.

Accordingly, it is possible to eliminate an unnatural change in luminance of the display screen occurring in the same scene, to perform efficient luminance control, and to improve luminance and image contrast. Can be

[Brief description of the drawings]

FIG. 1 is a block diagram of a brightness level control apparatus for a plasma display according to the present invention.

FIG. 2 is a block diagram of a conventional brightness level control device for a plasma display.

FIG. 3 is a block diagram illustrating a configuration of a scene change detection circuit.

FIG. 4 is a diagram showing blocks for performing averaging.

FIG. 5 is a diagram illustrating an image that is not determined to be a scene change.

FIG. 6 is a diagram showing an image determined to be a scene change.

FIG. 7 is a diagram showing a relationship between an average video level (APL) and power consumption.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scene change detection circuit 2 Brightness level switching circuit 3 Automatic brightness limiting circuit 4 Average brightness level calculation circuit 5 Brightness level control circuit 6 PDP drive controller 7 Frame memory 8 Subtractor 9 Difference data value calculation circuit 10 Difference data value accumulation circuit 11 Scene change detector

Claims (5)

(57) [Claims] 1. A scene change detecting means for detecting a scene change of an input video signal, an average luminance level calculating means for obtaining an average luminance level of the input video signal, and a scene change is detected by the scene change detecting means. Means for performing display luminance level control suitable for a display image based on the average luminance level when the display is performed. 2. A scene change detection means for detecting a scene change of an input video signal, and a display brightness level suitable for a display image is immediately obtained when a scene change is detected by the scene change detection means. Means for controlling the display so as to reach a display luminance level suitable for a display image after a set time if the scene change is not detected. 3. A scene change detecting means for detecting a scene change of an input video signal, an average luminance level calculating means for obtaining an average luminance level of the input video signal, and a scene change is detected by the scene change detecting means. If the scene change is not detected, the average brightness level calculation is controlled immediately after the set time if the scene change is not detected, based on the output from the average brightness level calculation means. Means for controlling to reach a display brightness level suitable for a display image based on an output from the means. 4. A luminance level control device for a display device is a plasma display device according to any one of claims 1-3. 5. A method for detecting a scene change of an input video signal, controlling the display luminance level suitable for a display image immediately when the scene change is detected, and detecting the scene change when the scene change is not detected. A luminance level control method for a display device, which controls to reach a display luminance level suitable for a display image after a set time.